gccrs: Add full definitions of Rust AST data structures

This adds the proper definitions of our AST nodes split across multiple
files for clarity

	gcc/rust/
	* ast/rust-expr.h: New.
	* ast/rust-macro.h: New.
	* ast/rust-path.h: New.
	* ast/rust-pattern.h: New.
	* ast/rust-stmt.h: New.
	* ast/rust-type.h: New.

Co-authored-by: Philip Herron <philip.herron@embecosm.com>

Signed-off-by: Joel Phillips <simplytheother@gmail.com>

6 files changed, 9782 insertions, 0 deletions

diff --git a/gcc/rust/ast/rust-expr.h b/gcc/rust/ast/rust-expr.h
new file mode 100644
index 0000000..1966a59
--- /dev/null
+++ b/gcc/rust/ast/rust-expr.h
@@ -0,0 +1,4631 @@
+#ifndef RUST_AST_EXPR_H
+#define RUST_AST_EXPR_H
+
+#include "rust-ast.h"
+#include "rust-path.h"
+#include "operator.h"
+
+namespace Rust {
+namespace AST {
+/* TODO: if GCC moves to C++17 or allows boost, replace some boolean
+ * "has_whatever" pairs with
+ * optional types (std::optional or boost::optional)? */
+
+// AST node for an expression with an accompanying block - abstract
+class ExprWithBlock : public Expr
+{
+protected:
+  // pure virtual clone implementation
+  virtual ExprWithBlock *clone_expr_with_block_impl () const = 0;
+
+  // prevent having to define multiple clone expressions
+  ExprWithBlock *clone_expr_impl () const final override
+  {
+    return clone_expr_with_block_impl ();
+  }
+
+  bool is_expr_without_block () const final override { return false; };
+
+public:
+  // Unique pointer custom clone function
+  std::unique_ptr<ExprWithBlock> clone_expr_with_block () const
+  {
+    return std::unique_ptr<ExprWithBlock> (clone_expr_with_block_impl ());
+  }
+};
+
+// Literals? Or literal base?
+class LiteralExpr : public ExprWithoutBlock
+{
+  std::vector<Attribute> outer_attrs;
+  Literal literal;
+  Location locus;
+
+public:
+  std::string as_string () const override { return literal.as_string (); }
+
+  Literal::LitType get_lit_type () const { return literal.get_lit_type (); }
+
+  LiteralExpr (std::string value_as_string, Literal::LitType type,
+	       PrimitiveCoreType type_hint, std::vector<Attribute> outer_attrs,
+	       Location locus)
+    : outer_attrs (std::move (outer_attrs)),
+      literal (std::move (value_as_string), type, type_hint), locus (locus)
+  {}
+
+  LiteralExpr (Literal literal, std::vector<Attribute> outer_attrs,
+	       Location locus)
+    : outer_attrs (std::move (outer_attrs)), literal (std::move (literal)),
+      locus (locus)
+  {}
+
+  // Unique pointer custom clone function
+  std::unique_ptr<LiteralExpr> clone_literal_expr () const
+  {
+    return std::unique_ptr<LiteralExpr> (clone_literal_expr_impl ());
+  }
+
+  Location get_locus () const override final { return locus; }
+
+  Literal get_literal () const { return literal; }
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // Invalid if literal is in error state, so base stripping on that.
+  void mark_for_strip () override { literal = Literal::create_error (); }
+  bool is_marked_for_strip () const override { return literal.is_error (); }
+
+  const std::vector<Attribute> &get_outer_attrs () const { return outer_attrs; }
+  std::vector<Attribute> &get_outer_attrs () { return outer_attrs; }
+
+  void set_outer_attrs (std::vector<Attribute> new_attrs) override
+  {
+    outer_attrs = std::move (new_attrs);
+  }
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  LiteralExpr *clone_expr_without_block_impl () const final override
+  {
+    return clone_literal_expr_impl ();
+  }
+
+  /* not virtual as currently no subclasses of LiteralExpr, but could be in
+   * future */
+  /*virtual*/ LiteralExpr *clone_literal_expr_impl () const
+  {
+    return new LiteralExpr (*this);
+  }
+};
+
+// Literal expression attribute body (non-macro attribute)
+class AttrInputLiteral : public AttrInput
+{
+  LiteralExpr literal_expr;
+
+public:
+  AttrInputLiteral (LiteralExpr lit_expr) : literal_expr (std::move (lit_expr))
+  {}
+
+  std::string as_string () const override
+  {
+    return " = " + literal_expr.as_string ();
+  }
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  /* this can never be a cfg predicate - cfg and cfg_attr require a token-tree
+   * cfg */
+  bool check_cfg_predicate (const Session &) const override { return false; }
+
+  bool is_meta_item () const override { return false; }
+
+  LiteralExpr &get_literal () { return literal_expr; }
+
+  AttrInputType get_attr_input_type () const final override
+  {
+    return AttrInput::AttrInputType::LITERAL;
+  }
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  AttrInputLiteral *clone_attr_input_impl () const override
+  {
+    return new AttrInputLiteral (*this);
+  }
+};
+
+/* literal expr only meta item inner - TODO possibly replace with inheritance of
+ * LiteralExpr itself? */
+class MetaItemLitExpr : public MetaItemInner
+{
+  LiteralExpr lit_expr;
+
+public:
+  MetaItemLitExpr (LiteralExpr lit_expr) : lit_expr (std::move (lit_expr)) {}
+
+  std::string as_string () const override { return lit_expr.as_string (); }
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  bool check_cfg_predicate (const Session &session) const override;
+
+protected:
+  // Use covariance to implement clone function as returning this type
+  MetaItemLitExpr *clone_meta_item_inner_impl () const override
+  {
+    return new MetaItemLitExpr (*this);
+  }
+};
+
+// more generic meta item "path = lit" form
+class MetaItemPathLit : public MetaItem
+{
+  SimplePath path;
+  LiteralExpr lit;
+
+public:
+  MetaItemPathLit (SimplePath path, LiteralExpr lit_expr)
+    : path (std::move (path)), lit (std::move (lit_expr))
+  {}
+
+  std::string as_string () const override
+  {
+    return path.as_string () + " = " + lit.as_string ();
+  }
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  bool check_cfg_predicate (const Session &session) const override;
+  /* TODO: return true if "ident" is defined and value of it is "lit", return
+   * false otherwise */
+
+  Attribute to_attribute () const override;
+
+protected:
+  // Use covariance to implement clone function as returning this type
+  MetaItemPathLit *clone_meta_item_inner_impl () const override
+  {
+    return new MetaItemPathLit (*this);
+  }
+};
+
+/* Represents an expression using unary or binary operators as AST node. Can be
+ * overloaded. */
+class OperatorExpr : public ExprWithoutBlock
+{
+  // TODO: create binary and unary operator subclasses?
+public:
+  Location locus;
+
+protected:
+  /* Variables must be protected to allow derived classes to use them as first
+   * class citizens */
+  std::vector<Attribute> outer_attrs;
+  std::unique_ptr<Expr> main_or_left_expr;
+
+  // Constructor (only for initialisation of expr purposes)
+  OperatorExpr (std::unique_ptr<Expr> main_or_left_expr,
+		std::vector<Attribute> outer_attribs, Location locus)
+    : locus (locus), outer_attrs (std::move (outer_attribs)),
+      main_or_left_expr (std::move (main_or_left_expr))
+  {}
+
+  // Copy constructor (only for initialisation of expr purposes)
+  OperatorExpr (OperatorExpr const &other)
+    : locus (other.locus), outer_attrs (other.outer_attrs)
+  {
+    // guard to prevent null dereference (only required if error state)
+    if (other.main_or_left_expr != nullptr)
+      main_or_left_expr = other.main_or_left_expr->clone_expr ();
+  }
+
+  // Overload assignment operator to deep copy expr
+  OperatorExpr &operator= (OperatorExpr const &other)
+  {
+    ExprWithoutBlock::operator= (other);
+    locus = other.locus;
+    outer_attrs = other.outer_attrs;
+
+    // guard to prevent null dereference (only required if error state)
+    if (other.main_or_left_expr != nullptr)
+      main_or_left_expr = other.main_or_left_expr->clone_expr ();
+    else
+      main_or_left_expr = nullptr;
+
+    return *this;
+  }
+
+  // move constructors
+  OperatorExpr (OperatorExpr &&other) = default;
+  OperatorExpr &operator= (OperatorExpr &&other) = default;
+
+public:
+  Location get_locus () const override final { return locus; }
+
+  // Invalid if expr is null, so base stripping on that.
+  void mark_for_strip () override { main_or_left_expr = nullptr; }
+  bool is_marked_for_strip () const override
+  {
+    return main_or_left_expr == nullptr;
+  }
+
+  const std::vector<Attribute> &get_outer_attrs () const { return outer_attrs; }
+  std::vector<Attribute> &get_outer_attrs () { return outer_attrs; }
+
+  void set_outer_attrs (std::vector<Attribute> new_attrs) override
+  {
+    outer_attrs = std::move (new_attrs);
+  }
+};
+
+/* Unary prefix & or &mut (or && and &&mut) borrow operator. Cannot be
+ * overloaded. */
+class BorrowExpr : public OperatorExpr
+{
+  bool is_mut;
+  bool double_borrow;
+
+public:
+  std::string as_string () const override;
+
+  BorrowExpr (std::unique_ptr<Expr> borrow_lvalue, bool is_mut_borrow,
+	      bool is_double_borrow, std::vector<Attribute> outer_attribs,
+	      Location locus)
+    : OperatorExpr (std::move (borrow_lvalue), std::move (outer_attribs),
+		    locus),
+      is_mut (is_mut_borrow), double_borrow (is_double_borrow)
+  {}
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // TODO: is this better? Or is a "vis_block" better?
+  std::unique_ptr<Expr> &get_borrowed_expr ()
+  {
+    rust_assert (main_or_left_expr != nullptr);
+    return main_or_left_expr;
+  }
+
+  bool get_is_mut () const { return is_mut; }
+
+  bool get_is_double_borrow () const { return double_borrow; }
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  BorrowExpr *clone_expr_without_block_impl () const override
+  {
+    return new BorrowExpr (*this);
+  }
+};
+
+// Unary prefix * deference operator
+class DereferenceExpr : public OperatorExpr
+{
+public:
+  std::string as_string () const override;
+
+  // Constructor calls OperatorExpr's protected constructor
+  DereferenceExpr (std::unique_ptr<Expr> deref_lvalue,
+		   std::vector<Attribute> outer_attribs, Location locus)
+    : OperatorExpr (std::move (deref_lvalue), std::move (outer_attribs), locus)
+  {}
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // TODO: is this better? Or is a "vis_block" better?
+  std::unique_ptr<Expr> &get_dereferenced_expr ()
+  {
+    rust_assert (main_or_left_expr != nullptr);
+    return main_or_left_expr;
+  }
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  DereferenceExpr *clone_expr_without_block_impl () const override
+  {
+    return new DereferenceExpr (*this);
+  }
+};
+
+// Unary postfix ? error propogation operator. Cannot be overloaded.
+class ErrorPropagationExpr : public OperatorExpr
+{
+public:
+  std::string as_string () const override;
+
+  // Constructor calls OperatorExpr's protected constructor
+  ErrorPropagationExpr (std::unique_ptr<Expr> potential_error_value,
+			std::vector<Attribute> outer_attribs, Location locus)
+    : OperatorExpr (std::move (potential_error_value),
+		    std::move (outer_attribs), locus)
+  {}
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // TODO: is this better? Or is a "vis_block" better?
+  std::unique_ptr<Expr> &get_propagating_expr ()
+  {
+    rust_assert (main_or_left_expr != nullptr);
+    return main_or_left_expr;
+  }
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  ErrorPropagationExpr *clone_expr_without_block_impl () const override
+  {
+    return new ErrorPropagationExpr (*this);
+  }
+};
+
+// Unary prefix - or ! negation or NOT operators.
+class NegationExpr : public OperatorExpr
+{
+public:
+  using ExprType = NegationOperator;
+
+private:
+  /* Note: overload negation via std::ops::Neg and not via std::ops::Not
+   * Negation only works for signed integer and floating-point types, NOT only
+   * works for boolean and integer types (via bitwise NOT) */
+  ExprType expr_type;
+
+public:
+  std::string as_string () const override;
+
+  ExprType get_expr_type () const { return expr_type; }
+
+  // Constructor calls OperatorExpr's protected constructor
+  NegationExpr (std::unique_ptr<Expr> negated_value, ExprType expr_kind,
+		std::vector<Attribute> outer_attribs, Location locus)
+    : OperatorExpr (std::move (negated_value), std::move (outer_attribs),
+		    locus),
+      expr_type (expr_kind)
+  {}
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // TODO: is this better? Or is a "vis_block" better?
+  std::unique_ptr<Expr> &get_negated_expr ()
+  {
+    rust_assert (main_or_left_expr != nullptr);
+    return main_or_left_expr;
+  }
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  NegationExpr *clone_expr_without_block_impl () const override
+  {
+    return new NegationExpr (*this);
+  }
+};
+
+// Infix binary operators. +, -, *, /, %, &, |, ^, <<, >>
+class ArithmeticOrLogicalExpr : public OperatorExpr
+{
+public:
+  using ExprType = ArithmeticOrLogicalOperator;
+
+private:
+  // Note: overloading trait specified in comments
+  ExprType expr_type;
+
+  std::unique_ptr<Expr> right_expr;
+
+public:
+  std::string as_string () const override;
+
+  ExprType get_expr_type () const { return expr_type; }
+
+  // Constructor calls OperatorExpr's protected constructor
+  ArithmeticOrLogicalExpr (std::unique_ptr<Expr> left_value,
+			   std::unique_ptr<Expr> right_value,
+			   ExprType expr_kind, Location locus)
+    : OperatorExpr (std::move (left_value), std::vector<Attribute> (), locus),
+      expr_type (expr_kind), right_expr (std::move (right_value))
+  {}
+  // outer attributes not allowed
+
+  // Copy constructor - probably required due to unique pointer
+  ArithmeticOrLogicalExpr (ArithmeticOrLogicalExpr const &other)
+    : OperatorExpr (other), expr_type (other.expr_type),
+      right_expr (other.right_expr->clone_expr ())
+  {}
+
+  // Overload assignment operator
+  ArithmeticOrLogicalExpr &operator= (ArithmeticOrLogicalExpr const &other)
+  {
+    OperatorExpr::operator= (other);
+    // main_or_left_expr = other.main_or_left_expr->clone_expr();
+    right_expr = other.right_expr->clone_expr ();
+    expr_type = other.expr_type;
+
+    return *this;
+  }
+
+  // move constructors
+  ArithmeticOrLogicalExpr (ArithmeticOrLogicalExpr &&other) = default;
+  ArithmeticOrLogicalExpr &operator= (ArithmeticOrLogicalExpr &&other)
+    = default;
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // TODO: is this better? Or is a "vis_block" better?
+  std::unique_ptr<Expr> &get_left_expr ()
+  {
+    rust_assert (main_or_left_expr != nullptr);
+    return main_or_left_expr;
+  }
+
+  // TODO: is this better? Or is a "vis_block" better?
+  std::unique_ptr<Expr> &get_right_expr ()
+  {
+    rust_assert (right_expr != nullptr);
+    return right_expr;
+  }
+
+  void visit_lhs (ASTVisitor &vis) { main_or_left_expr->accept_vis (vis); }
+  void visit_rhs (ASTVisitor &vis) { right_expr->accept_vis (vis); }
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  ArithmeticOrLogicalExpr *clone_expr_without_block_impl () const override
+  {
+    return new ArithmeticOrLogicalExpr (*this);
+  }
+};
+
+// Infix binary comparison operators. ==, !=, <, <=, >, >=
+class ComparisonExpr : public OperatorExpr
+{
+public:
+  using ExprType = ComparisonOperator;
+
+private:
+  // Note: overloading trait specified in comments
+  ExprType expr_type;
+
+  std::unique_ptr<Expr> right_expr;
+
+public:
+  std::string as_string () const override;
+
+  ExprType get_expr_type () const { return expr_type; }
+
+  // Constructor requires pointers for polymorphism
+  ComparisonExpr (std::unique_ptr<Expr> left_value,
+		  std::unique_ptr<Expr> right_value, ExprType comparison_kind,
+		  Location locus)
+    : OperatorExpr (std::move (left_value), std::vector<Attribute> (), locus),
+      expr_type (comparison_kind), right_expr (std::move (right_value))
+  {}
+  // outer attributes not allowed
+
+  // Copy constructor also calls OperatorExpr's protected constructor
+  ComparisonExpr (ComparisonExpr const &other)
+    : OperatorExpr (other), expr_type (other.expr_type),
+      right_expr (other.right_expr->clone_expr ())
+  {}
+
+  // Overload assignment operator to deep copy
+  ComparisonExpr &operator= (ComparisonExpr const &other)
+  {
+    OperatorExpr::operator= (other);
+    // main_or_left_expr = other.main_or_left_expr->clone_expr();
+    right_expr = other.right_expr->clone_expr ();
+    expr_type = other.expr_type;
+    // outer_attrs = other.outer_attrs;
+
+    return *this;
+  }
+
+  // move constructors
+  ComparisonExpr (ComparisonExpr &&other) = default;
+  ComparisonExpr &operator= (ComparisonExpr &&other) = default;
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // TODO: is this better? Or is a "vis_block" better?
+  std::unique_ptr<Expr> &get_left_expr ()
+  {
+    rust_assert (main_or_left_expr != nullptr);
+    return main_or_left_expr;
+  }
+
+  // TODO: is this better? Or is a "vis_block" better?
+  std::unique_ptr<Expr> &get_right_expr ()
+  {
+    rust_assert (right_expr != nullptr);
+    return right_expr;
+  }
+
+  ExprType get_kind () { return expr_type; }
+
+  /* TODO: implement via a function call to std::cmp::PartialEq::eq(&op1, &op2)
+   * maybe? */
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  ComparisonExpr *clone_expr_without_block_impl () const override
+  {
+    return new ComparisonExpr (*this);
+  }
+};
+
+// Infix binary lazy boolean logical operators && and ||.
+class LazyBooleanExpr : public OperatorExpr
+{
+public:
+  using ExprType = LazyBooleanOperator;
+
+private:
+  ExprType expr_type;
+
+  std::unique_ptr<Expr> right_expr;
+
+public:
+  // Constructor calls OperatorExpr's protected constructor
+  LazyBooleanExpr (std::unique_ptr<Expr> left_bool_expr,
+		   std::unique_ptr<Expr> right_bool_expr, ExprType expr_kind,
+		   Location locus)
+    : OperatorExpr (std::move (left_bool_expr), std::vector<Attribute> (),
+		    locus),
+      expr_type (expr_kind), right_expr (std::move (right_bool_expr))
+  {}
+  // outer attributes not allowed
+
+  // Copy constructor also calls OperatorExpr's protected constructor
+  LazyBooleanExpr (LazyBooleanExpr const &other)
+    : OperatorExpr (other), expr_type (other.expr_type),
+      right_expr (other.right_expr->clone_expr ())
+  {}
+
+  // Overload assignment operator to deep copy
+  LazyBooleanExpr &operator= (LazyBooleanExpr const &other)
+  {
+    OperatorExpr::operator= (other);
+    // main_or_left_expr = other.main_or_left_expr->clone_expr();
+    right_expr = other.right_expr->clone_expr ();
+    expr_type = other.expr_type;
+
+    return *this;
+  }
+
+  // move constructors
+  LazyBooleanExpr (LazyBooleanExpr &&other) = default;
+  LazyBooleanExpr &operator= (LazyBooleanExpr &&other) = default;
+
+  std::string as_string () const override;
+
+  ExprType get_expr_type () const { return expr_type; }
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // TODO: is this better? Or is a "vis_block" better?
+  std::unique_ptr<Expr> &get_left_expr ()
+  {
+    rust_assert (main_or_left_expr != nullptr);
+    return main_or_left_expr;
+  }
+
+  // TODO: is this better? Or is a "vis_block" better?
+  std::unique_ptr<Expr> &get_right_expr ()
+  {
+    rust_assert (right_expr != nullptr);
+    return right_expr;
+  }
+
+  ExprType get_kind () { return expr_type; }
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  LazyBooleanExpr *clone_expr_without_block_impl () const override
+  {
+    return new LazyBooleanExpr (*this);
+  }
+};
+
+// Binary infix "as" cast expression.
+class TypeCastExpr : public OperatorExpr
+{
+  std::unique_ptr<TypeNoBounds> type_to_convert_to;
+
+  // Note: only certain type casts allowed, outlined in reference
+public:
+  std::string as_string () const override;
+
+  // Constructor requires calling protected constructor of OperatorExpr
+  TypeCastExpr (std::unique_ptr<Expr> expr_to_cast,
+		std::unique_ptr<TypeNoBounds> type_to_cast_to, Location locus)
+    : OperatorExpr (std::move (expr_to_cast), std::vector<Attribute> (), locus),
+      type_to_convert_to (std::move (type_to_cast_to))
+  {}
+  // outer attributes not allowed
+
+  // Copy constructor also requires calling protected constructor
+  TypeCastExpr (TypeCastExpr const &other)
+    : OperatorExpr (other),
+      type_to_convert_to (other.type_to_convert_to->clone_type_no_bounds ())
+  {}
+
+  // Overload assignment operator to deep copy
+  TypeCastExpr &operator= (TypeCastExpr const &other)
+  {
+    OperatorExpr::operator= (other);
+    // main_or_left_expr = other.main_or_left_expr->clone_expr();
+    type_to_convert_to = other.type_to_convert_to->clone_type_no_bounds ();
+
+    return *this;
+  }
+
+  // move constructors
+  TypeCastExpr (TypeCastExpr &&other) = default;
+  TypeCastExpr &operator= (TypeCastExpr &&other) = default;
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // TODO: is this better? Or is a "vis_block" better?
+  std::unique_ptr<Expr> &get_casted_expr ()
+  {
+    rust_assert (main_or_left_expr != nullptr);
+    return main_or_left_expr;
+  }
+
+  // TODO: is this better? Or is a "vis_block" better?
+  std::unique_ptr<TypeNoBounds> &get_type_to_cast_to ()
+  {
+    rust_assert (type_to_convert_to != nullptr);
+    return type_to_convert_to;
+  }
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  TypeCastExpr *clone_expr_without_block_impl () const override
+  {
+    return new TypeCastExpr (*this);
+  }
+};
+
+// Binary assignment expression.
+class AssignmentExpr : public OperatorExpr
+{
+  std::unique_ptr<Expr> right_expr;
+
+public:
+  std::string as_string () const override;
+
+  // Call OperatorExpr constructor to initialise left_expr
+  AssignmentExpr (std::unique_ptr<Expr> value_to_assign_to,
+		  std::unique_ptr<Expr> value_to_assign,
+		  std::vector<Attribute> outer_attribs, Location locus)
+    : OperatorExpr (std::move (value_to_assign_to), std::move (outer_attribs),
+		    locus),
+      right_expr (std::move (value_to_assign))
+  {}
+  // outer attributes not allowed
+
+  // Call OperatorExpr constructor in copy constructor, as well as clone
+  AssignmentExpr (AssignmentExpr const &other)
+    : OperatorExpr (other), right_expr (other.right_expr->clone_expr ())
+  {}
+
+  // Overload assignment operator to clone unique_ptr right_expr
+  AssignmentExpr &operator= (AssignmentExpr const &other)
+  {
+    OperatorExpr::operator= (other);
+    // main_or_left_expr = other.main_or_left_expr->clone_expr();
+    right_expr = other.right_expr->clone_expr ();
+    // outer_attrs = other.outer_attrs;
+
+    return *this;
+  }
+
+  // move constructors
+  AssignmentExpr (AssignmentExpr &&other) = default;
+  AssignmentExpr &operator= (AssignmentExpr &&other) = default;
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  void visit_lhs (ASTVisitor &vis) { main_or_left_expr->accept_vis (vis); }
+  void visit_rhs (ASTVisitor &vis) { right_expr->accept_vis (vis); }
+
+  // TODO: is this better? Or is a "vis_block" better?
+  std::unique_ptr<Expr> &get_left_expr ()
+  {
+    rust_assert (main_or_left_expr != nullptr);
+    return main_or_left_expr;
+  }
+
+  // TODO: is this better? Or is a "vis_block" better?
+  std::unique_ptr<Expr> &get_right_expr ()
+  {
+    rust_assert (right_expr != nullptr);
+    return right_expr;
+  }
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  AssignmentExpr *clone_expr_without_block_impl () const override
+  {
+    return new AssignmentExpr (*this);
+  }
+};
+
+/* Binary infix compound assignment (arithmetic or logic then assignment)
+ * expressions. */
+class CompoundAssignmentExpr : public OperatorExpr
+{
+public:
+  using ExprType = CompoundAssignmentOperator;
+
+private:
+  // Note: overloading trait specified in comments
+  ExprType expr_type;
+  std::unique_ptr<Expr> right_expr;
+
+public:
+  std::string as_string () const override;
+
+  ExprType get_expr_type () const { return expr_type; }
+
+  // Use pointers in constructor to enable polymorphism
+  CompoundAssignmentExpr (std::unique_ptr<Expr> value_to_assign_to,
+			  std::unique_ptr<Expr> value_to_assign,
+			  ExprType expr_kind, Location locus)
+    : OperatorExpr (std::move (value_to_assign_to), std::vector<Attribute> (),
+		    locus),
+      expr_type (expr_kind), right_expr (std::move (value_to_assign))
+  {}
+  // outer attributes not allowed
+
+  // Have clone in copy constructor
+  CompoundAssignmentExpr (CompoundAssignmentExpr const &other)
+    : OperatorExpr (other), expr_type (other.expr_type),
+      right_expr (other.right_expr->clone_expr ())
+  {}
+
+  // Overload assignment operator to clone
+  CompoundAssignmentExpr &operator= (CompoundAssignmentExpr const &other)
+  {
+    OperatorExpr::operator= (other);
+    // main_or_left_expr = other.main_or_left_expr->clone_expr();
+    right_expr = other.right_expr->clone_expr ();
+    expr_type = other.expr_type;
+    // outer_attrs = other.outer_attrs;
+
+    return *this;
+  }
+
+  // move constructors
+  CompoundAssignmentExpr (CompoundAssignmentExpr &&other) = default;
+  CompoundAssignmentExpr &operator= (CompoundAssignmentExpr &&other) = default;
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // TODO: is this better? Or is a "vis_block" better?
+  std::unique_ptr<Expr> &get_left_expr ()
+  {
+    rust_assert (main_or_left_expr != nullptr);
+    return main_or_left_expr;
+  }
+
+  // TODO: is this better? Or is a "vis_block" better?
+  std::unique_ptr<Expr> &get_right_expr ()
+  {
+    rust_assert (right_expr != nullptr);
+    return right_expr;
+  }
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  CompoundAssignmentExpr *clone_expr_without_block_impl () const override
+  {
+    return new CompoundAssignmentExpr (*this);
+  }
+};
+
+// Expression in parentheses (i.e. like literally just any 3 + (2 * 6))
+class GroupedExpr : public ExprWithoutBlock
+{
+  std::vector<Attribute> outer_attrs;
+  std::vector<Attribute> inner_attrs;
+  std::unique_ptr<Expr> expr_in_parens;
+  Location locus;
+
+public:
+  std::string as_string () const override;
+
+  const std::vector<Attribute> &get_inner_attrs () const { return inner_attrs; }
+  std::vector<Attribute> &get_inner_attrs () { return inner_attrs; }
+
+  const std::vector<Attribute> &get_outer_attrs () const { return outer_attrs; }
+  std::vector<Attribute> &get_outer_attrs () { return outer_attrs; }
+
+  void set_outer_attrs (std::vector<Attribute> new_attrs) override
+  {
+    outer_attrs = std::move (new_attrs);
+  }
+
+  GroupedExpr (std::unique_ptr<Expr> parenthesised_expr,
+	       std::vector<Attribute> inner_attribs,
+	       std::vector<Attribute> outer_attribs, Location locus)
+    : outer_attrs (std::move (outer_attribs)),
+      inner_attrs (std::move (inner_attribs)),
+      expr_in_parens (std::move (parenthesised_expr)), locus (locus)
+  {}
+
+  // Copy constructor includes clone for expr_in_parens
+  GroupedExpr (GroupedExpr const &other)
+    : ExprWithoutBlock (other), outer_attrs (other.outer_attrs),
+      inner_attrs (other.inner_attrs), locus (other.locus)
+  {
+    // guard to prevent null dereference (only required if error state)
+    if (other.expr_in_parens != nullptr)
+      expr_in_parens = other.expr_in_parens->clone_expr ();
+  }
+
+  // Overloaded assignment operator to clone expr_in_parens
+  GroupedExpr &operator= (GroupedExpr const &other)
+  {
+    ExprWithoutBlock::operator= (other);
+    inner_attrs = other.inner_attrs;
+    locus = other.locus;
+    outer_attrs = other.outer_attrs;
+
+    // guard to prevent null dereference (only required if error state)
+    if (other.expr_in_parens != nullptr)
+      expr_in_parens = other.expr_in_parens->clone_expr ();
+    else
+      expr_in_parens = nullptr;
+
+    return *this;
+  }
+
+  // move constructors
+  GroupedExpr (GroupedExpr &&other) = default;
+  GroupedExpr &operator= (GroupedExpr &&other) = default;
+
+  Location get_locus () const override final { return locus; }
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // Invalid if inner expr is null, so base stripping on that.
+  void mark_for_strip () override { expr_in_parens = nullptr; }
+  bool is_marked_for_strip () const override
+  {
+    return expr_in_parens == nullptr;
+  }
+
+  // TODO: is this better? Or is a "vis_block" better?
+  std::unique_ptr<Expr> &get_expr_in_parens ()
+  {
+    rust_assert (expr_in_parens != nullptr);
+    return expr_in_parens;
+  }
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  GroupedExpr *clone_expr_without_block_impl () const override
+  {
+    return new GroupedExpr (*this);
+  }
+};
+
+// Base array initialisation internal element representation thing (abstract)
+// aka ArrayElements
+class ArrayElems
+{
+public:
+  virtual ~ArrayElems () {}
+
+  // Unique pointer custom clone ArrayElems function
+  std::unique_ptr<ArrayElems> clone_array_elems () const
+  {
+    return std::unique_ptr<ArrayElems> (clone_array_elems_impl ());
+  }
+
+  virtual std::string as_string () const = 0;
+
+  virtual void accept_vis (ASTVisitor &vis) = 0;
+
+  NodeId get_node_id () const { return node_id; }
+
+protected:
+  ArrayElems () : node_id (Analysis::Mappings::get ()->get_next_node_id ()) {}
+
+  // pure virtual clone implementation
+  virtual ArrayElems *clone_array_elems_impl () const = 0;
+
+  NodeId node_id;
+};
+
+// Value array elements
+class ArrayElemsValues : public ArrayElems
+{
+  std::vector<std::unique_ptr<Expr> > values;
+  Location locus;
+
+public:
+  ArrayElemsValues (std::vector<std::unique_ptr<Expr> > elems, Location locus)
+    : ArrayElems (), values (std::move (elems)), locus (locus)
+  {}
+
+  // copy constructor with vector clone
+  ArrayElemsValues (ArrayElemsValues const &other)
+  {
+    values.reserve (other.values.size ());
+    for (const auto &e : other.values)
+      values.push_back (e->clone_expr ());
+  }
+
+  // overloaded assignment operator with vector clone
+  ArrayElemsValues &operator= (ArrayElemsValues const &other)
+  {
+    values.reserve (other.values.size ());
+    for (const auto &e : other.values)
+      values.push_back (e->clone_expr ());
+
+    return *this;
+  }
+
+  // move constructors
+  ArrayElemsValues (ArrayElemsValues &&other) = default;
+  ArrayElemsValues &operator= (ArrayElemsValues &&other) = default;
+
+  std::string as_string () const override;
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // TODO: this mutable getter seems really dodgy. Think up better way.
+  const std::vector<std::unique_ptr<Expr> > &get_values () const
+  {
+    return values;
+  }
+  std::vector<std::unique_ptr<Expr> > &get_values () { return values; }
+
+  size_t get_num_values () const { return values.size (); }
+
+protected:
+  ArrayElemsValues *clone_array_elems_impl () const override
+  {
+    return new ArrayElemsValues (*this);
+  }
+};
+
+// Copied array element and number of copies
+class ArrayElemsCopied : public ArrayElems
+{
+  std::unique_ptr<Expr> elem_to_copy;
+  std::unique_ptr<Expr> num_copies;
+  Location locus;
+
+public:
+  // Constructor requires pointers for polymorphism
+  ArrayElemsCopied (std::unique_ptr<Expr> copied_elem,
+		    std::unique_ptr<Expr> copy_amount, Location locus)
+    : ArrayElems (), elem_to_copy (std::move (copied_elem)),
+      num_copies (std::move (copy_amount)), locus (locus)
+  {}
+
+  // Copy constructor required due to unique_ptr - uses custom clone
+  ArrayElemsCopied (ArrayElemsCopied const &other)
+    : elem_to_copy (other.elem_to_copy->clone_expr ()),
+      num_copies (other.num_copies->clone_expr ())
+  {}
+
+  // Overloaded assignment operator for deep copying
+  ArrayElemsCopied &operator= (ArrayElemsCopied const &other)
+  {
+    elem_to_copy = other.elem_to_copy->clone_expr ();
+    num_copies = other.num_copies->clone_expr ();
+
+    return *this;
+  }
+
+  // move constructors
+  ArrayElemsCopied (ArrayElemsCopied &&other) = default;
+  ArrayElemsCopied &operator= (ArrayElemsCopied &&other) = default;
+
+  std::string as_string () const override;
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // TODO: is this better? Or is a "vis_block" better?
+  std::unique_ptr<Expr> &get_elem_to_copy ()
+  {
+    rust_assert (elem_to_copy != nullptr);
+    return elem_to_copy;
+  }
+
+  // TODO: is this better? Or is a "vis_block" better?
+  std::unique_ptr<Expr> &get_num_copies ()
+  {
+    rust_assert (num_copies != nullptr);
+    return num_copies;
+  }
+
+protected:
+  ArrayElemsCopied *clone_array_elems_impl () const override
+  {
+    return new ArrayElemsCopied (*this);
+  }
+};
+
+// Array definition-ish expression
+class ArrayExpr : public ExprWithoutBlock
+{
+  std::vector<Attribute> outer_attrs;
+  std::vector<Attribute> inner_attrs;
+  std::unique_ptr<ArrayElems> internal_elements;
+  Location locus;
+
+  // TODO: find another way to store this to save memory?
+  bool marked_for_strip = false;
+
+public:
+  std::string as_string () const override;
+
+  const std::vector<Attribute> &get_inner_attrs () const { return inner_attrs; }
+  std::vector<Attribute> &get_inner_attrs () { return inner_attrs; }
+
+  const std::vector<Attribute> &get_outer_attrs () const { return outer_attrs; }
+  std::vector<Attribute> &get_outer_attrs () { return outer_attrs; }
+
+  void set_outer_attrs (std::vector<Attribute> new_attrs) override
+  {
+    outer_attrs = std::move (new_attrs);
+  }
+
+  // Constructor requires ArrayElems pointer
+  ArrayExpr (std::unique_ptr<ArrayElems> array_elems,
+	     std::vector<Attribute> inner_attribs,
+	     std::vector<Attribute> outer_attribs, Location locus)
+    : outer_attrs (std::move (outer_attribs)),
+      inner_attrs (std::move (inner_attribs)),
+      internal_elements (std::move (array_elems)), locus (locus)
+  {
+    rust_assert (internal_elements != nullptr);
+  }
+
+  // Copy constructor requires cloning ArrayElems for polymorphism to hold
+  ArrayExpr (ArrayExpr const &other)
+    : ExprWithoutBlock (other), outer_attrs (other.outer_attrs),
+      inner_attrs (other.inner_attrs), locus (other.locus),
+      marked_for_strip (other.marked_for_strip)
+  {
+    internal_elements = other.internal_elements->clone_array_elems ();
+    rust_assert (internal_elements != nullptr);
+  }
+
+  // Overload assignment operator to clone internal_elements
+  ArrayExpr &operator= (ArrayExpr const &other)
+  {
+    ExprWithoutBlock::operator= (other);
+    inner_attrs = other.inner_attrs;
+    locus = other.locus;
+    marked_for_strip = other.marked_for_strip;
+    outer_attrs = other.outer_attrs;
+
+    internal_elements = other.internal_elements->clone_array_elems ();
+
+    rust_assert (internal_elements != nullptr);
+    return *this;
+  }
+
+  // move constructors
+  ArrayExpr (ArrayExpr &&other) = default;
+  ArrayExpr &operator= (ArrayExpr &&other) = default;
+
+  Location get_locus () const override final { return locus; }
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // Can't think of any invalid invariants, so store boolean.
+  void mark_for_strip () override { marked_for_strip = true; }
+  bool is_marked_for_strip () const override { return marked_for_strip; }
+
+  // TODO: is this better? Or is a "vis_block" better?
+  std::unique_ptr<ArrayElems> &get_array_elems ()
+  {
+    rust_assert (internal_elements != nullptr);
+    return internal_elements;
+  }
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  ArrayExpr *clone_expr_without_block_impl () const override
+  {
+    return new ArrayExpr (*this);
+  }
+};
+
+// Aka IndexExpr (also applies to slices)
+/* Apparently a[b] is equivalent to *std::ops::Index::index(&a, b) or
+ * *std::ops::Index::index_mut(&mut a, b) */
+/* Also apparently deref operations on a will be repeatedly applied to find an
+ * implementation */
+class ArrayIndexExpr : public ExprWithoutBlock
+{
+  std::vector<Attribute> outer_attrs;
+  std::unique_ptr<Expr> array_expr;
+  std::unique_ptr<Expr> index_expr;
+  Location locus;
+
+public:
+  std::string as_string () const override;
+
+  ArrayIndexExpr (std::unique_ptr<Expr> array_expr,
+		  std::unique_ptr<Expr> array_index_expr,
+		  std::vector<Attribute> outer_attribs, Location locus)
+    : outer_attrs (std::move (outer_attribs)),
+      array_expr (std::move (array_expr)),
+      index_expr (std::move (array_index_expr)), locus (locus)
+  {}
+
+  // Copy constructor requires special cloning due to unique_ptr
+  ArrayIndexExpr (ArrayIndexExpr const &other)
+    : ExprWithoutBlock (other), outer_attrs (other.outer_attrs),
+      locus (other.locus)
+  {
+    // guard to prevent null dereference (only required if error state)
+    if (other.array_expr != nullptr)
+      array_expr = other.array_expr->clone_expr ();
+    if (other.index_expr != nullptr)
+      index_expr = other.index_expr->clone_expr ();
+  }
+
+  // Overload assignment operator to clone unique_ptrs
+  ArrayIndexExpr &operator= (ArrayIndexExpr const &other)
+  {
+    ExprWithoutBlock::operator= (other);
+    outer_attrs = other.outer_attrs;
+    locus = other.locus;
+
+    // guard to prevent null dereference (only required if error state)
+    if (other.array_expr != nullptr)
+      array_expr = other.array_expr->clone_expr ();
+    else
+      array_expr = nullptr;
+    if (other.index_expr != nullptr)
+      index_expr = other.index_expr->clone_expr ();
+    else
+      index_expr = nullptr;
+
+    return *this;
+  }
+
+  // move constructors
+  ArrayIndexExpr (ArrayIndexExpr &&other) = default;
+  ArrayIndexExpr &operator= (ArrayIndexExpr &&other) = default;
+
+  Location get_locus () const override final { return locus; }
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // Invalid if either expr is null, so base stripping on that.
+  void mark_for_strip () override
+  {
+    array_expr = nullptr;
+    index_expr = nullptr;
+  }
+  bool is_marked_for_strip () const override
+  {
+    return array_expr == nullptr && index_expr == nullptr;
+  }
+
+  // TODO: is this better? Or is a "vis_block" better?
+  std::unique_ptr<Expr> &get_array_expr ()
+  {
+    rust_assert (array_expr != nullptr);
+    return array_expr;
+  }
+
+  // TODO: is this better? Or is a "vis_block" better?
+  std::unique_ptr<Expr> &get_index_expr ()
+  {
+    rust_assert (index_expr != nullptr);
+    return index_expr;
+  }
+
+  const std::vector<Attribute> &get_outer_attrs () const { return outer_attrs; }
+  std::vector<Attribute> &get_outer_attrs () { return outer_attrs; }
+
+  void set_outer_attrs (std::vector<Attribute> new_attrs) override
+  {
+    outer_attrs = std::move (new_attrs);
+  }
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  ArrayIndexExpr *clone_expr_without_block_impl () const override
+  {
+    return new ArrayIndexExpr (*this);
+  }
+};
+
+// AST representation of a tuple
+class TupleExpr : public ExprWithoutBlock
+{
+  std::vector<Attribute> outer_attrs;
+  std::vector<Attribute> inner_attrs;
+  std::vector<std::unique_ptr<Expr> > tuple_elems;
+  Location locus;
+
+  // TODO: find another way to store this to save memory?
+  bool marked_for_strip = false;
+
+public:
+  std::string as_string () const override;
+
+  const std::vector<Attribute> &get_inner_attrs () const { return inner_attrs; }
+  std::vector<Attribute> &get_inner_attrs () { return inner_attrs; }
+
+  const std::vector<Attribute> &get_outer_attrs () const { return outer_attrs; }
+  std::vector<Attribute> &get_outer_attrs () { return outer_attrs; }
+
+  void set_outer_attrs (std::vector<Attribute> new_attrs) override
+  {
+    outer_attrs = std::move (new_attrs);
+  }
+
+  TupleExpr (std::vector<std::unique_ptr<Expr> > tuple_elements,
+	     std::vector<Attribute> inner_attribs,
+	     std::vector<Attribute> outer_attribs, Location locus)
+    : outer_attrs (std::move (outer_attribs)),
+      inner_attrs (std::move (inner_attribs)),
+      tuple_elems (std::move (tuple_elements)), locus (locus)
+  {}
+
+  // copy constructor with vector clone
+  TupleExpr (TupleExpr const &other)
+    : ExprWithoutBlock (other), outer_attrs (other.outer_attrs),
+      inner_attrs (other.inner_attrs), locus (other.locus),
+      marked_for_strip (other.marked_for_strip)
+  {
+    tuple_elems.reserve (other.tuple_elems.size ());
+    for (const auto &e : other.tuple_elems)
+      tuple_elems.push_back (e->clone_expr ());
+  }
+
+  // overloaded assignment operator to vector clone
+  TupleExpr &operator= (TupleExpr const &other)
+  {
+    ExprWithoutBlock::operator= (other);
+    outer_attrs = other.outer_attrs;
+    inner_attrs = other.inner_attrs;
+    locus = other.locus;
+    marked_for_strip = other.marked_for_strip;
+
+    tuple_elems.reserve (other.tuple_elems.size ());
+    for (const auto &e : other.tuple_elems)
+      tuple_elems.push_back (e->clone_expr ());
+
+    return *this;
+  }
+
+  // move constructors
+  TupleExpr (TupleExpr &&other) = default;
+  TupleExpr &operator= (TupleExpr &&other) = default;
+
+  /* Note: syntactically, can disambiguate single-element tuple from parens with
+   * comma, i.e. (0,) rather than (0) */
+
+  Location get_locus () const override final { return locus; }
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // Can't think of any invalid invariants, so store boolean.
+  void mark_for_strip () override { marked_for_strip = true; }
+  bool is_marked_for_strip () const override { return marked_for_strip; }
+
+  // TODO: this mutable getter seems really dodgy. Think up better way.
+  const std::vector<std::unique_ptr<Expr> > &get_tuple_elems () const
+  {
+    return tuple_elems;
+  }
+  std::vector<std::unique_ptr<Expr> > &get_tuple_elems ()
+  {
+    return tuple_elems;
+  }
+
+  bool is_unit () const { return tuple_elems.size () == 0; }
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  TupleExpr *clone_expr_without_block_impl () const override
+  {
+    return new TupleExpr (*this);
+  }
+};
+
+// aka TupleIndexingExpr
+// AST representation of a tuple indexing expression
+class TupleIndexExpr : public ExprWithoutBlock
+{
+  std::vector<Attribute> outer_attrs;
+  std::unique_ptr<Expr> tuple_expr;
+  // TupleIndex is a decimal int literal with no underscores or suffix
+  TupleIndex tuple_index;
+
+  Location locus;
+
+  // i.e. pair.0
+
+public:
+  std::string as_string () const override;
+
+  TupleIndex get_tuple_index () const { return tuple_index; }
+
+  TupleIndexExpr (std::unique_ptr<Expr> tuple_expr, TupleIndex index,
+		  std::vector<Attribute> outer_attribs, Location locus)
+    : outer_attrs (std::move (outer_attribs)),
+      tuple_expr (std::move (tuple_expr)), tuple_index (index), locus (locus)
+  {}
+
+  // Copy constructor requires a clone for tuple_expr
+  TupleIndexExpr (TupleIndexExpr const &other)
+    : ExprWithoutBlock (other), outer_attrs (other.outer_attrs),
+      tuple_index (other.tuple_index), locus (other.locus)
+  {
+    // guard to prevent null dereference (only required if error state)
+    if (other.tuple_expr != nullptr)
+      tuple_expr = other.tuple_expr->clone_expr ();
+  }
+
+  // Overload assignment operator in order to clone
+  TupleIndexExpr &operator= (TupleIndexExpr const &other)
+  {
+    ExprWithoutBlock::operator= (other);
+    tuple_index = other.tuple_index;
+    locus = other.locus;
+    outer_attrs = other.outer_attrs;
+
+    // guard to prevent null dereference (only required if error state)
+    if (other.tuple_expr != nullptr)
+      tuple_expr = other.tuple_expr->clone_expr ();
+    else
+      tuple_expr = nullptr;
+
+    return *this;
+  }
+
+  // move constructors
+  TupleIndexExpr (TupleIndexExpr &&other) = default;
+  TupleIndexExpr &operator= (TupleIndexExpr &&other) = default;
+
+  Location get_locus () const override final { return locus; }
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // Invalid if tuple expr is null, so base stripping on that.
+  void mark_for_strip () override { tuple_expr = nullptr; }
+  bool is_marked_for_strip () const override { return tuple_expr == nullptr; }
+
+  // TODO: is this better? Or is a "vis_block" better?
+  std::unique_ptr<Expr> &get_tuple_expr ()
+  {
+    rust_assert (tuple_expr != nullptr);
+    return tuple_expr;
+  }
+
+  const std::vector<Attribute> &get_outer_attrs () const { return outer_attrs; }
+  std::vector<Attribute> &get_outer_attrs () { return outer_attrs; }
+
+  void set_outer_attrs (std::vector<Attribute> new_attrs) override
+  {
+    outer_attrs = std::move (new_attrs);
+  }
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  TupleIndexExpr *clone_expr_without_block_impl () const override
+  {
+    return new TupleIndexExpr (*this);
+  }
+};
+
+// Base struct/tuple/union value creator AST node (abstract)
+class StructExpr : public ExprWithoutBlock
+{
+  std::vector<Attribute> outer_attrs;
+  PathInExpression struct_name;
+
+protected:
+  // Protected constructor to allow initialising struct_name
+  StructExpr (PathInExpression struct_path,
+	      std::vector<Attribute> outer_attribs)
+    : outer_attrs (std::move (outer_attribs)),
+      struct_name (std::move (struct_path))
+  {}
+
+public:
+  const PathInExpression &get_struct_name () const { return struct_name; }
+  PathInExpression &get_struct_name () { return struct_name; }
+
+  std::string as_string () const override;
+
+  // Invalid if path is empty, so base stripping on that.
+  void mark_for_strip () override
+  {
+    struct_name = PathInExpression::create_error ();
+  }
+  bool is_marked_for_strip () const override { return struct_name.is_error (); }
+
+  const std::vector<Attribute> &get_outer_attrs () const { return outer_attrs; }
+  std::vector<Attribute> &get_outer_attrs () { return outer_attrs; }
+
+  void set_outer_attrs (std::vector<Attribute> new_attrs) override
+  {
+    outer_attrs = std::move (new_attrs);
+  }
+};
+
+// Actual AST node of the struct creator (with no fields). Not abstract!
+class StructExprStruct : public StructExpr
+{
+  std::vector<Attribute> inner_attrs;
+
+  Location locus;
+
+public:
+  std::string as_string () const override;
+
+  const std::vector<Attribute> &get_inner_attrs () const { return inner_attrs; }
+  std::vector<Attribute> &get_inner_attrs () { return inner_attrs; }
+
+  // Constructor has to call protected constructor of base class
+  StructExprStruct (PathInExpression struct_path,
+		    std::vector<Attribute> inner_attribs,
+		    std::vector<Attribute> outer_attribs, Location locus)
+    : StructExpr (std::move (struct_path), std::move (outer_attribs)),
+      inner_attrs (std::move (inner_attribs)), locus (locus)
+  {}
+
+  Location get_locus () const override final { return locus; }
+
+  void accept_vis (ASTVisitor &vis) override;
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  StructExprStruct *clone_expr_without_block_impl () const override
+  {
+    return new StructExprStruct (*this);
+  }
+};
+
+/* AST node representing expression used to fill a struct's fields from another
+ * struct */
+struct StructBase
+{
+private:
+  std::unique_ptr<Expr> base_struct;
+  Location locus;
+
+public:
+  StructBase (std::unique_ptr<Expr> base_struct_ptr, Location locus)
+    : base_struct (std::move (base_struct_ptr)), locus (locus)
+  {}
+
+  // Copy constructor requires clone
+  StructBase (StructBase const &other)
+  {
+    /* HACK: gets around base_struct pointer being null (e.g. if no struct base
+     * exists) */
+    if (other.base_struct != nullptr)
+      base_struct = other.base_struct->clone_expr ();
+  }
+
+  // Destructor
+  ~StructBase () = default;
+
+  // Overload assignment operator to clone base_struct
+  StructBase &operator= (StructBase const &other)
+  {
+    // prevent null pointer dereference
+    if (other.base_struct != nullptr)
+      base_struct = other.base_struct->clone_expr ();
+    else
+      base_struct = nullptr;
+
+    return *this;
+  }
+
+  // move constructors
+  StructBase (StructBase &&other) = default;
+  StructBase &operator= (StructBase &&other) = default;
+
+  // Returns a null expr-ed StructBase - error state
+  static StructBase error () { return StructBase (nullptr, Location ()); }
+
+  // Returns whether StructBase is in error state
+  bool is_invalid () const { return base_struct == nullptr; }
+
+  std::string as_string () const;
+
+  // TODO: is this better? Or is a "vis_block" better?
+  std::unique_ptr<Expr> &get_base_struct ()
+  {
+    rust_assert (base_struct != nullptr);
+    return base_struct;
+  }
+};
+
+/* Base AST node for a single struct expression field (in struct instance
+ * creation) - abstract */
+class StructExprField
+{
+public:
+  virtual ~StructExprField () {}
+
+  // Unique pointer custom clone function
+  std::unique_ptr<StructExprField> clone_struct_expr_field () const
+  {
+    return std::unique_ptr<StructExprField> (clone_struct_expr_field_impl ());
+  }
+
+  virtual std::string as_string () const = 0;
+
+  virtual void accept_vis (ASTVisitor &vis) = 0;
+
+  virtual Location get_locus () const = 0;
+
+  NodeId get_node_id () const { return node_id; }
+
+protected:
+  // pure virtual clone implementation
+  virtual StructExprField *clone_struct_expr_field_impl () const = 0;
+
+  StructExprField () : node_id (Analysis::Mappings::get ()->get_next_node_id ())
+  {}
+
+  NodeId node_id;
+};
+
+// Identifier-only variant of StructExprField AST node
+class StructExprFieldIdentifier : public StructExprField
+{
+  Identifier field_name;
+  Location locus;
+
+public:
+  StructExprFieldIdentifier (Identifier field_identifier, Location locus)
+    : StructExprField (), field_name (std::move (field_identifier)),
+      locus (locus)
+  {}
+
+  std::string as_string () const override { return field_name; }
+
+  Location get_locus () const override final { return locus; }
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  Identifier get_field_name () const { return field_name; }
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  StructExprFieldIdentifier *clone_struct_expr_field_impl () const override
+  {
+    return new StructExprFieldIdentifier (*this);
+  }
+};
+
+/* Base AST node for a single struct expression field with an assigned value -
+ * abstract */
+class StructExprFieldWithVal : public StructExprField
+{
+  std::unique_ptr<Expr> value;
+
+protected:
+  StructExprFieldWithVal (std::unique_ptr<Expr> field_value)
+    : StructExprField (), value (std::move (field_value))
+  {}
+
+  // Copy constructor requires clone
+  StructExprFieldWithVal (StructExprFieldWithVal const &other)
+    : value (other.value->clone_expr ())
+  {}
+
+  // Overload assignment operator to clone unique_ptr
+  StructExprFieldWithVal &operator= (StructExprFieldWithVal const &other)
+  {
+    value = other.value->clone_expr ();
+
+    return *this;
+  }
+
+  // move constructors
+  StructExprFieldWithVal (StructExprFieldWithVal &&other) = default;
+  StructExprFieldWithVal &operator= (StructExprFieldWithVal &&other) = default;
+
+public:
+  std::string as_string () const override;
+
+  // TODO: is this better? Or is a "vis_block" better?
+  std::unique_ptr<Expr> &get_value ()
+  {
+    rust_assert (value != nullptr);
+    return value;
+  }
+};
+
+// Identifier and value variant of StructExprField AST node
+class StructExprFieldIdentifierValue : public StructExprFieldWithVal
+{
+  Identifier field_name;
+  Location locus;
+
+public:
+  StructExprFieldIdentifierValue (Identifier field_identifier,
+				  std::unique_ptr<Expr> field_value,
+				  Location locus)
+    : StructExprFieldWithVal (std::move (field_value)),
+      field_name (std::move (field_identifier)), locus (locus)
+  {}
+
+  std::string as_string () const override;
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  std::string get_field_name () const { return field_name; }
+
+  Location get_locus () const override final { return locus; }
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  StructExprFieldIdentifierValue *clone_struct_expr_field_impl () const override
+  {
+    return new StructExprFieldIdentifierValue (*this);
+  }
+};
+
+// Tuple index and value variant of StructExprField AST node
+class StructExprFieldIndexValue : public StructExprFieldWithVal
+{
+  TupleIndex index;
+  Location locus;
+
+public:
+  StructExprFieldIndexValue (TupleIndex tuple_index,
+			     std::unique_ptr<Expr> field_value, Location locus)
+    : StructExprFieldWithVal (std::move (field_value)), index (tuple_index),
+      locus (locus)
+  {}
+
+  std::string as_string () const override;
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  TupleIndex get_index () const { return index; }
+
+  Location get_locus () const override final { return locus; }
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  StructExprFieldIndexValue *clone_struct_expr_field_impl () const override
+  {
+    return new StructExprFieldIndexValue (*this);
+  }
+};
+
+// AST node of a struct creator with fields
+class StructExprStructFields : public StructExprStruct
+{
+  // std::vector<StructExprField> fields;
+  std::vector<std::unique_ptr<StructExprField> > fields;
+
+  // bool has_struct_base;
+  StructBase struct_base;
+
+public:
+  std::string as_string () const override;
+
+  bool has_struct_base () const { return !struct_base.is_invalid (); }
+
+  // Constructor for StructExprStructFields when no struct base is used
+  StructExprStructFields (
+    PathInExpression struct_path,
+    std::vector<std::unique_ptr<StructExprField> > expr_fields, Location locus,
+    StructBase base_struct = StructBase::error (),
+    std::vector<Attribute> inner_attribs = std::vector<Attribute> (),
+    std::vector<Attribute> outer_attribs = std::vector<Attribute> ())
+    : StructExprStruct (std::move (struct_path), std::move (inner_attribs),
+			std::move (outer_attribs), locus),
+      fields (std::move (expr_fields)), struct_base (std::move (base_struct))
+  {}
+
+  // copy constructor with vector clone
+  StructExprStructFields (StructExprStructFields const &other)
+    : StructExprStruct (other), struct_base (other.struct_base)
+  {
+    fields.reserve (other.fields.size ());
+    for (const auto &e : other.fields)
+      fields.push_back (e->clone_struct_expr_field ());
+  }
+
+  // overloaded assignment operator with vector clone
+  StructExprStructFields &operator= (StructExprStructFields const &other)
+  {
+    StructExprStruct::operator= (other);
+    struct_base = other.struct_base;
+
+    fields.reserve (other.fields.size ());
+    for (const auto &e : other.fields)
+      fields.push_back (e->clone_struct_expr_field ());
+
+    return *this;
+  }
+
+  // move constructors
+  StructExprStructFields (StructExprStructFields &&other) = default;
+  StructExprStructFields &operator= (StructExprStructFields &&other) = default;
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // TODO: this mutable getter seems really dodgy. Think up better way.
+  std::vector<std::unique_ptr<StructExprField> > &get_fields ()
+  {
+    return fields;
+  }
+  const std::vector<std::unique_ptr<StructExprField> > &get_fields () const
+  {
+    return fields;
+  }
+
+  StructBase &get_struct_base () { return struct_base; }
+  const StructBase &get_struct_base () const { return struct_base; }
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  StructExprStructFields *clone_expr_without_block_impl () const override
+  {
+    return new StructExprStructFields (*this);
+  }
+};
+
+// AST node of the functional update struct creator
+/* TODO: remove and replace with StructExprStructFields, except with empty
+ * vector of fields? */
+class StructExprStructBase : public StructExprStruct
+{
+  StructBase struct_base;
+
+public:
+  std::string as_string () const override;
+
+  StructExprStructBase (PathInExpression struct_path, StructBase base_struct,
+			std::vector<Attribute> inner_attribs,
+			std::vector<Attribute> outer_attribs, Location locus)
+    : StructExprStruct (std::move (struct_path), std::move (inner_attribs),
+			std::move (outer_attribs), locus),
+      struct_base (std::move (base_struct))
+  {}
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  StructBase &get_struct_base () { return struct_base; }
+  const StructBase &get_struct_base () const { return struct_base; }
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  StructExprStructBase *clone_expr_without_block_impl () const override
+  {
+    return new StructExprStructBase (*this);
+  }
+};
+
+// Forward decl for Function - used in CallExpr
+class Function;
+
+// Function call expression AST node
+class CallExpr : public ExprWithoutBlock
+{
+  std::vector<Attribute> outer_attrs;
+  std::unique_ptr<Expr> function;
+  std::vector<std::unique_ptr<Expr> > params;
+  Location locus;
+
+public:
+  Function *fndeclRef;
+
+  std::string as_string () const override;
+
+  CallExpr (std::unique_ptr<Expr> function_expr,
+	    std::vector<std::unique_ptr<Expr> > function_params,
+	    std::vector<Attribute> outer_attribs, Location locus)
+    : outer_attrs (std::move (outer_attribs)),
+      function (std::move (function_expr)),
+      params (std::move (function_params)), locus (locus)
+  {}
+
+  // copy constructor requires clone
+  CallExpr (CallExpr const &other)
+    : ExprWithoutBlock (other), outer_attrs (other.outer_attrs),
+      locus (other.locus)
+  {
+    // guard to prevent null dereference (only required if error state)
+    if (other.function != nullptr)
+      function = other.function->clone_expr ();
+
+    params.reserve (other.params.size ());
+    for (const auto &e : other.params)
+      params.push_back (e->clone_expr ());
+  }
+
+  // Overload assignment operator to clone
+  CallExpr &operator= (CallExpr const &other)
+  {
+    ExprWithoutBlock::operator= (other);
+    locus = other.locus;
+    outer_attrs = other.outer_attrs;
+
+    // guard to prevent null dereference (only required if error state)
+    if (other.function != nullptr)
+      function = other.function->clone_expr ();
+    else
+      function = nullptr;
+
+    params.reserve (other.params.size ());
+    for (const auto &e : other.params)
+      params.push_back (e->clone_expr ());
+
+    return *this;
+  }
+
+  // move constructors
+  CallExpr (CallExpr &&other) = default;
+  CallExpr &operator= (CallExpr &&other) = default;
+
+  // Returns whether function call has parameters.
+  bool has_params () const { return !params.empty (); }
+
+  Location get_locus () const override final { return locus; }
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // Invalid if function expr is null, so base stripping on that.
+  void mark_for_strip () override { function = nullptr; }
+  bool is_marked_for_strip () const override { return function == nullptr; }
+
+  // TODO: this mutable getter seems really dodgy. Think up better way.
+  const std::vector<std::unique_ptr<Expr> > &get_params () const
+  {
+    return params;
+  }
+  std::vector<std::unique_ptr<Expr> > &get_params () { return params; }
+
+  // TODO: is this better? Or is a "vis_block" better?
+  std::unique_ptr<Expr> &get_function_expr ()
+  {
+    rust_assert (function != nullptr);
+    return function;
+  }
+
+  const std::vector<Attribute> &get_outer_attrs () const { return outer_attrs; }
+  std::vector<Attribute> &get_outer_attrs () { return outer_attrs; }
+
+  void set_outer_attrs (std::vector<Attribute> new_attrs) override
+  {
+    outer_attrs = std::move (new_attrs);
+  }
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  CallExpr *clone_expr_without_block_impl () const override
+  {
+    return new CallExpr (*this);
+  }
+};
+
+// Method call expression AST node
+class MethodCallExpr : public ExprWithoutBlock
+{
+  std::vector<Attribute> outer_attrs;
+  std::unique_ptr<Expr> receiver;
+  PathExprSegment method_name;
+  std::vector<std::unique_ptr<Expr> > params;
+  Location locus;
+
+public:
+  std::string as_string () const override;
+
+  MethodCallExpr (std::unique_ptr<Expr> call_receiver,
+		  PathExprSegment method_path,
+		  std::vector<std::unique_ptr<Expr> > method_params,
+		  std::vector<Attribute> outer_attribs, Location locus)
+    : outer_attrs (std::move (outer_attribs)),
+      receiver (std::move (call_receiver)),
+      method_name (std::move (method_path)), params (std::move (method_params)),
+      locus (locus)
+  {}
+
+  // copy constructor required due to cloning
+  MethodCallExpr (MethodCallExpr const &other)
+    : ExprWithoutBlock (other), outer_attrs (other.outer_attrs),
+      method_name (other.method_name), locus (other.locus)
+  {
+    // guard to prevent null dereference (only required if error state)
+    if (other.receiver != nullptr)
+      receiver = other.receiver->clone_expr ();
+
+    params.reserve (other.params.size ());
+    for (const auto &e : other.params)
+      params.push_back (e->clone_expr ());
+  }
+
+  // Overload assignment operator to clone receiver object
+  MethodCallExpr &operator= (MethodCallExpr const &other)
+  {
+    ExprWithoutBlock::operator= (other);
+    method_name = other.method_name;
+    locus = other.locus;
+    outer_attrs = other.outer_attrs;
+
+    // guard to prevent null dereference (only required if error state)
+    if (other.receiver != nullptr)
+      receiver = other.receiver->clone_expr ();
+    else
+      receiver = nullptr;
+
+    params.reserve (other.params.size ());
+    for (const auto &e : other.params)
+      params.push_back (e->clone_expr ());
+
+    return *this;
+  }
+
+  // move constructors
+  MethodCallExpr (MethodCallExpr &&other) = default;
+  MethodCallExpr &operator= (MethodCallExpr &&other) = default;
+
+  Location get_locus () const override final { return locus; }
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // Invalid if receiver expr is null, so base stripping on that.
+  void mark_for_strip () override { receiver = nullptr; }
+  bool is_marked_for_strip () const override { return receiver == nullptr; }
+
+  // TODO: this mutable getter seems really dodgy. Think up better way.
+  const std::vector<std::unique_ptr<Expr> > &get_params () const
+  {
+    return params;
+  }
+  std::vector<std::unique_ptr<Expr> > &get_params () { return params; }
+
+  // TODO: is this better? Or is a "vis_block" better?
+  std::unique_ptr<Expr> &get_receiver_expr ()
+  {
+    rust_assert (receiver != nullptr);
+    return receiver;
+  }
+
+  const PathExprSegment &get_method_name () const { return method_name; }
+  PathExprSegment &get_method_name () { return method_name; }
+
+  const std::vector<Attribute> &get_outer_attrs () const { return outer_attrs; }
+  std::vector<Attribute> &get_outer_attrs () { return outer_attrs; }
+
+  void set_outer_attrs (std::vector<Attribute> new_attrs) override
+  {
+    outer_attrs = std::move (new_attrs);
+  }
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  MethodCallExpr *clone_expr_without_block_impl () const override
+  {
+    return new MethodCallExpr (*this);
+  }
+};
+
+// aka FieldExpression
+// Struct or union field access expression AST node
+class FieldAccessExpr : public ExprWithoutBlock
+{
+  std::vector<Attribute> outer_attrs;
+  std::unique_ptr<Expr> receiver;
+  Identifier field;
+  Location locus;
+
+public:
+  std::string as_string () const override;
+
+  FieldAccessExpr (std::unique_ptr<Expr> field_access_receiver,
+		   Identifier field_name, std::vector<Attribute> outer_attribs,
+		   Location locus)
+    : outer_attrs (std::move (outer_attribs)),
+      receiver (std::move (field_access_receiver)),
+      field (std::move (field_name)), locus (locus)
+  {}
+
+  // Copy constructor required due to unique_ptr cloning
+  FieldAccessExpr (FieldAccessExpr const &other)
+    : ExprWithoutBlock (other), outer_attrs (other.outer_attrs),
+      field (other.field), locus (other.locus)
+  {
+    // guard to prevent null dereference (only required if error state)
+    if (other.receiver != nullptr)
+      receiver = other.receiver->clone_expr ();
+  }
+
+  // Overload assignment operator to clone unique_ptr
+  FieldAccessExpr &operator= (FieldAccessExpr const &other)
+  {
+    ExprWithoutBlock::operator= (other);
+    field = other.field;
+    locus = other.locus;
+    outer_attrs = other.outer_attrs;
+
+    // guard to prevent null dereference (only required if error state)
+    if (other.receiver != nullptr)
+      receiver = other.receiver->clone_expr ();
+    else
+      receiver = nullptr;
+
+    return *this;
+  }
+
+  // move constructors
+  FieldAccessExpr (FieldAccessExpr &&other) = default;
+  FieldAccessExpr &operator= (FieldAccessExpr &&other) = default;
+
+  Location get_locus () const override final { return locus; }
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // Invalid if receiver expr is null, so base stripping on that.
+  void mark_for_strip () override { receiver = nullptr; }
+  bool is_marked_for_strip () const override { return receiver == nullptr; }
+
+  // TODO: is this better? Or is a "vis_block" better?
+  std::unique_ptr<Expr> &get_receiver_expr ()
+  {
+    rust_assert (receiver != nullptr);
+    return receiver;
+  }
+
+  Identifier get_field_name () const { return field; }
+
+  const std::vector<Attribute> &get_outer_attrs () const { return outer_attrs; }
+  std::vector<Attribute> &get_outer_attrs () { return outer_attrs; }
+
+  void set_outer_attrs (std::vector<Attribute> new_attrs) override
+  {
+    outer_attrs = std::move (new_attrs);
+  }
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  FieldAccessExpr *clone_expr_without_block_impl () const override
+  {
+    return new FieldAccessExpr (*this);
+  }
+};
+
+// Closure parameter data structure
+struct ClosureParam
+{
+private:
+  std::vector<Attribute> outer_attrs;
+  std::unique_ptr<Pattern> pattern;
+
+  // bool has_type_given;
+  std::unique_ptr<Type> type;
+  Location locus;
+
+public:
+  // Returns whether the type of the parameter has been given.
+  bool has_type_given () const { return type != nullptr; }
+
+  bool has_outer_attrs () const { return !outer_attrs.empty (); }
+
+  // Constructor for closure parameter
+  ClosureParam (std::unique_ptr<Pattern> param_pattern, Location locus,
+		std::unique_ptr<Type> param_type = nullptr,
+		std::vector<Attribute> outer_attrs = {})
+    : outer_attrs (std::move (outer_attrs)),
+      pattern (std::move (param_pattern)), type (std::move (param_type)),
+      locus (locus)
+  {}
+
+  // Copy constructor required due to cloning as a result of unique_ptrs
+  ClosureParam (ClosureParam const &other) : outer_attrs (other.outer_attrs)
+  {
+    // guard to protect from null pointer dereference
+    if (other.pattern != nullptr)
+      pattern = other.pattern->clone_pattern ();
+    if (other.type != nullptr)
+      type = other.type->clone_type ();
+  }
+
+  ~ClosureParam () = default;
+
+  // Assignment operator must be overloaded to clone as well
+  ClosureParam &operator= (ClosureParam const &other)
+  {
+    outer_attrs = other.outer_attrs;
+
+    // guard to protect from null pointer dereference
+    if (other.pattern != nullptr)
+      pattern = other.pattern->clone_pattern ();
+    else
+      pattern = nullptr;
+    if (other.type != nullptr)
+      type = other.type->clone_type ();
+    else
+      type = nullptr;
+
+    return *this;
+  }
+
+  // move constructors
+  ClosureParam (ClosureParam &&other) = default;
+  ClosureParam &operator= (ClosureParam &&other) = default;
+
+  // Returns whether closure parameter is in an error state.
+  bool is_error () const { return pattern == nullptr; }
+
+  // Creates an error state closure parameter.
+  static ClosureParam create_error ()
+  {
+    return ClosureParam (nullptr, Location ());
+  }
+
+  std::string as_string () const;
+
+  const std::vector<Attribute> &get_outer_attrs () const { return outer_attrs; }
+  std::vector<Attribute> &get_outer_attrs () { return outer_attrs; }
+
+  // TODO: is this better? Or is a "vis_block" better?
+  std::unique_ptr<Pattern> &get_pattern ()
+  {
+    rust_assert (pattern != nullptr);
+    return pattern;
+  }
+
+  // TODO: is this better? Or is a "vis_block" better?
+  std::unique_ptr<Type> &get_type ()
+  {
+    rust_assert (has_type_given ());
+    return type;
+  }
+};
+
+// Base closure definition expression AST node - abstract
+class ClosureExpr : public ExprWithoutBlock
+{
+  std::vector<Attribute> outer_attrs;
+  bool has_move;
+  std::vector<ClosureParam> params; // may be empty
+  Location locus;
+
+protected:
+  ClosureExpr (std::vector<ClosureParam> closure_params, bool has_move,
+	       std::vector<Attribute> outer_attribs, Location locus)
+    : outer_attrs (std::move (outer_attribs)), has_move (has_move),
+      params (std::move (closure_params)), locus (locus)
+  {}
+
+public:
+  std::string as_string () const override;
+
+  Location get_locus () const override final { return locus; }
+
+  // TODO: this mutable getter seems really dodgy. Think up better way.
+  const std::vector<ClosureParam> &get_params () const { return params; }
+  std::vector<ClosureParam> &get_params () { return params; }
+
+  const std::vector<Attribute> &get_outer_attrs () const { return outer_attrs; }
+  std::vector<Attribute> &get_outer_attrs () { return outer_attrs; }
+
+  void set_outer_attrs (std::vector<Attribute> new_attrs) override
+  {
+    outer_attrs = std::move (new_attrs);
+  }
+};
+
+// Represents a non-type-specified closure expression AST node
+class ClosureExprInner : public ClosureExpr
+{
+  std::unique_ptr<Expr> closure_inner;
+
+public:
+  std::string as_string () const override;
+
+  // Constructor for a ClosureExprInner
+  ClosureExprInner (std::unique_ptr<Expr> closure_inner_expr,
+		    std::vector<ClosureParam> closure_params, Location locus,
+		    bool is_move = false,
+		    std::vector<Attribute> outer_attribs
+		    = std::vector<Attribute> ())
+    : ClosureExpr (std::move (closure_params), is_move,
+		   std::move (outer_attribs), locus),
+      closure_inner (std::move (closure_inner_expr))
+  {}
+
+  // Copy constructor must be defined to allow copying via cloning of unique_ptr
+  ClosureExprInner (ClosureExprInner const &other) : ClosureExpr (other)
+  {
+    // guard to prevent null dereference (only required if error state)
+    if (other.closure_inner != nullptr)
+      closure_inner = other.closure_inner->clone_expr ();
+  }
+
+  // Overload assignment operator to clone closure_inner
+  ClosureExprInner &operator= (ClosureExprInner const &other)
+  {
+    ClosureExpr::operator= (other);
+    // params = other.params;
+    // has_move = other.has_move;
+    // outer_attrs = other.outer_attrs;
+
+    // guard to prevent null dereference (only required if error state)
+    if (other.closure_inner != nullptr)
+      closure_inner = other.closure_inner->clone_expr ();
+    else
+      closure_inner = nullptr;
+
+    return *this;
+  }
+
+  // move constructors
+  ClosureExprInner (ClosureExprInner &&other) = default;
+  ClosureExprInner &operator= (ClosureExprInner &&other) = default;
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // Invalid if inner expr is null, so base stripping on that.
+  void mark_for_strip () override { closure_inner = nullptr; }
+  bool is_marked_for_strip () const override
+  {
+    return closure_inner == nullptr;
+  }
+
+  // TODO: is this better? Or is a "vis_block" better?
+  std::unique_ptr<Expr> &get_definition_expr ()
+  {
+    rust_assert (closure_inner != nullptr);
+    return closure_inner;
+  }
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  ClosureExprInner *clone_expr_without_block_impl () const override
+  {
+    return new ClosureExprInner (*this);
+  }
+};
+
+// A block AST node
+class BlockExpr : public ExprWithBlock
+{
+  std::vector<Attribute> outer_attrs;
+  std::vector<Attribute> inner_attrs;
+  std::vector<std::unique_ptr<Stmt> > statements;
+  std::unique_ptr<Expr> expr;
+  Location start_locus;
+  Location end_locus;
+  bool marked_for_strip = false;
+
+public:
+  std::string as_string () const override;
+
+  // Returns whether the block contains statements.
+  bool has_statements () const { return !statements.empty (); }
+
+  // Returns whether the block contains a final expression.
+  bool has_tail_expr () const { return expr != nullptr; }
+
+  BlockExpr (std::vector<std::unique_ptr<Stmt> > block_statements,
+	     std::unique_ptr<Expr> block_expr,
+	     std::vector<Attribute> inner_attribs,
+	     std::vector<Attribute> outer_attribs, Location start_locus,
+	     Location end_locus)
+    : outer_attrs (std::move (outer_attribs)),
+      inner_attrs (std::move (inner_attribs)),
+      statements (std::move (block_statements)), expr (std::move (block_expr)),
+      start_locus (start_locus), end_locus (end_locus)
+  {}
+
+  // Copy constructor with clone
+  BlockExpr (BlockExpr const &other)
+    : ExprWithBlock (other), outer_attrs (other.outer_attrs),
+      inner_attrs (other.inner_attrs), start_locus (other.start_locus),
+      end_locus (other.end_locus), marked_for_strip (other.marked_for_strip)
+  {
+    // guard to protect from null pointer dereference
+    if (other.expr != nullptr)
+      expr = other.expr->clone_expr ();
+
+    statements.reserve (other.statements.size ());
+    for (const auto &e : other.statements)
+      statements.push_back (e->clone_stmt ());
+  }
+
+  // Overloaded assignment operator to clone pointer
+  BlockExpr &operator= (BlockExpr const &other)
+  {
+    ExprWithBlock::operator= (other);
+    inner_attrs = other.inner_attrs;
+    start_locus = other.start_locus;
+    end_locus = other.end_locus;
+    marked_for_strip = other.marked_for_strip;
+    outer_attrs = other.outer_attrs;
+
+    // guard to protect from null pointer dereference
+    if (other.expr != nullptr)
+      expr = other.expr->clone_expr ();
+    else
+      expr = nullptr;
+
+    statements.reserve (other.statements.size ());
+    for (const auto &e : other.statements)
+      statements.push_back (e->clone_stmt ());
+
+    return *this;
+  }
+
+  // move constructors
+  BlockExpr (BlockExpr &&other) = default;
+  BlockExpr &operator= (BlockExpr &&other) = default;
+
+  // Unique pointer custom clone function
+  std::unique_ptr<BlockExpr> clone_block_expr () const
+  {
+    return std::unique_ptr<BlockExpr> (clone_block_expr_impl ());
+  }
+
+  Location get_locus () const override final { return start_locus; }
+
+  Location get_start_locus () const { return start_locus; }
+  Location get_end_locus () const { return end_locus; }
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // Can be completely empty, so have to have a separate flag.
+  void mark_for_strip () override { marked_for_strip = true; }
+  bool is_marked_for_strip () const override { return marked_for_strip; }
+
+  size_t num_statements () const { return statements.size (); }
+
+  // TODO: this mutable getter seems really dodgy. Think up better way.
+  const std::vector<Attribute> &get_inner_attrs () const { return inner_attrs; }
+  std::vector<Attribute> &get_inner_attrs () { return inner_attrs; }
+
+  const std::vector<std::unique_ptr<Stmt> > &get_statements () const
+  {
+    return statements;
+  }
+  std::vector<std::unique_ptr<Stmt> > &get_statements () { return statements; }
+
+  // TODO: is this better? Or is a "vis_block" better?
+  std::unique_ptr<Expr> &get_tail_expr ()
+  {
+    rust_assert (has_tail_expr ());
+    return expr;
+  }
+
+  // Removes the tail expression from the block.
+  void strip_tail_expr () { expr = nullptr; }
+
+  const std::vector<Attribute> &get_outer_attrs () const { return outer_attrs; }
+  std::vector<Attribute> &get_outer_attrs () { return outer_attrs; }
+
+  void set_outer_attrs (std::vector<Attribute> new_attrs) override
+  {
+    outer_attrs = std::move (new_attrs);
+  }
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  BlockExpr *clone_expr_with_block_impl () const final override
+  {
+    return clone_block_expr_impl ();
+  }
+
+  /* This is the base method as not an abstract class - not virtual but could be
+   * in future if required. */
+  /*virtual*/ BlockExpr *clone_block_expr_impl () const
+  {
+    return new BlockExpr (*this);
+  }
+};
+
+// Represents a type-specified closure expression AST node
+class ClosureExprInnerTyped : public ClosureExpr
+{
+  // TODO: spec says typenobounds
+  std::unique_ptr<Type> return_type;
+  std::unique_ptr<BlockExpr>
+    expr; // only used because may be polymorphic in future
+
+public:
+  std::string as_string () const override;
+
+  // Constructor potentially with a move
+  ClosureExprInnerTyped (std::unique_ptr<Type> closure_return_type,
+			 std::unique_ptr<BlockExpr> closure_expr,
+			 std::vector<ClosureParam> closure_params,
+			 Location locus, bool is_move = false,
+			 std::vector<Attribute> outer_attribs
+			 = std::vector<Attribute> ())
+    : ClosureExpr (std::move (closure_params), is_move,
+		   std::move (outer_attribs), locus),
+      return_type (std::move (closure_return_type)),
+      expr (std::move (closure_expr))
+  {}
+
+  // Copy constructor requires cloning
+  ClosureExprInnerTyped (ClosureExprInnerTyped const &other)
+    : ClosureExpr (other)
+  {
+    // guard to prevent null dereference (only required if error state)
+    if (other.expr != nullptr)
+      expr = other.expr->clone_block_expr ();
+    if (other.return_type != nullptr)
+      return_type = other.return_type->clone_type ();
+  }
+
+  // Overload assignment operator to clone unique_ptrs
+  ClosureExprInnerTyped &operator= (ClosureExprInnerTyped const &other)
+  {
+    ClosureExpr::operator= (other);
+    // params = other.params;
+    // has_move = other.has_move;
+    // outer_attrs = other.outer_attrs;
+
+    // guard to prevent null dereference (only required if error state)
+    if (other.expr != nullptr)
+      expr = other.expr->clone_block_expr ();
+    else
+      expr = nullptr;
+    if (other.return_type != nullptr)
+      return_type = other.return_type->clone_type ();
+    else
+      return_type = nullptr;
+
+    return *this;
+  }
+
+  // move constructors
+  ClosureExprInnerTyped (ClosureExprInnerTyped &&other) = default;
+  ClosureExprInnerTyped &operator= (ClosureExprInnerTyped &&other) = default;
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  /* Invalid if inner expr is null, so base stripping on that. Technically,
+   * type should also not be null. */
+  void mark_for_strip () override { expr = nullptr; }
+  bool is_marked_for_strip () const override { return expr == nullptr; }
+
+  // TODO: is this better? Or is a "vis_block" better?
+  std::unique_ptr<BlockExpr> &get_definition_block ()
+  {
+    rust_assert (expr != nullptr);
+    return expr;
+  }
+
+  // TODO: is this better? Or is a "vis_block" better?
+  std::unique_ptr<Type> &get_return_type ()
+  {
+    rust_assert (return_type != nullptr);
+    return return_type;
+  }
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  ClosureExprInnerTyped *clone_expr_without_block_impl () const override
+  {
+    return new ClosureExprInnerTyped (*this);
+  }
+};
+
+// AST node representing continue expression within loops
+class ContinueExpr : public ExprWithoutBlock
+{
+  std::vector<Attribute> outer_attrs;
+  Lifetime label;
+  Location locus;
+
+  // TODO: find another way to store this to save memory?
+  bool marked_for_strip = false;
+
+public:
+  std::string as_string () const override;
+
+  // Returns true if the continue expr has a label.
+  bool has_label () const { return !label.is_error (); }
+
+  // Constructor for a ContinueExpr with a label.
+  ContinueExpr (Lifetime label, std::vector<Attribute> outer_attribs,
+		Location locus)
+    : outer_attrs (std::move (outer_attribs)), label (std::move (label)),
+      locus (locus)
+  {}
+
+  Location get_locus () const override final { return locus; }
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // Can't think of any invalid invariants, so store boolean.
+  void mark_for_strip () override { marked_for_strip = true; }
+  bool is_marked_for_strip () const override { return marked_for_strip; }
+
+  const std::vector<Attribute> &get_outer_attrs () const { return outer_attrs; }
+  std::vector<Attribute> &get_outer_attrs () { return outer_attrs; }
+
+  void set_outer_attrs (std::vector<Attribute> new_attrs) override
+  {
+    outer_attrs = std::move (new_attrs);
+  }
+
+  Lifetime &get_label () { return label; }
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  ContinueExpr *clone_expr_without_block_impl () const override
+  {
+    return new ContinueExpr (*this);
+  }
+};
+// TODO: merge "break" and "continue"? Or even merge in "return"?
+
+// AST node representing break expression within loops
+class BreakExpr : public ExprWithoutBlock
+{
+  std::vector<Attribute> outer_attrs;
+  Lifetime label;
+  std::unique_ptr<Expr> break_expr;
+  Location locus;
+
+  // TODO: find another way to store this to save memory?
+  bool marked_for_strip = false;
+
+public:
+  std::string as_string () const override;
+
+  // Returns whether the break expression has a label or not.
+  bool has_label () const { return !label.is_error (); }
+
+  /* Returns whether the break expression has an expression used in the break or
+   * not. */
+  bool has_break_expr () const { return break_expr != nullptr; }
+
+  // Constructor for a break expression
+  BreakExpr (Lifetime break_label, std::unique_ptr<Expr> expr_in_break,
+	     std::vector<Attribute> outer_attribs, Location locus)
+    : outer_attrs (std::move (outer_attribs)), label (std::move (break_label)),
+      break_expr (std::move (expr_in_break)), locus (locus)
+  {}
+
+  // Copy constructor defined to use clone for unique pointer
+  BreakExpr (BreakExpr const &other)
+    : ExprWithoutBlock (other), outer_attrs (other.outer_attrs),
+      label (other.label), locus (other.locus),
+      marked_for_strip (other.marked_for_strip)
+  {
+    // guard to protect from null pointer dereference
+    if (other.break_expr != nullptr)
+      break_expr = other.break_expr->clone_expr ();
+  }
+
+  // Overload assignment operator to clone unique pointer
+  BreakExpr &operator= (BreakExpr const &other)
+  {
+    ExprWithoutBlock::operator= (other);
+    label = other.label;
+    locus = other.locus;
+    marked_for_strip = other.marked_for_strip;
+    outer_attrs = other.outer_attrs;
+
+    // guard to protect from null pointer dereference
+    if (other.break_expr != nullptr)
+      break_expr = other.break_expr->clone_expr ();
+    else
+      break_expr = nullptr;
+
+    return *this;
+  }
+
+  // move constructors
+  BreakExpr (BreakExpr &&other) = default;
+  BreakExpr &operator= (BreakExpr &&other) = default;
+
+  Location get_locus () const override final { return locus; }
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // Can't think of any invalid invariants, so store boolean.
+  void mark_for_strip () override { marked_for_strip = true; }
+  bool is_marked_for_strip () const override { return marked_for_strip; }
+
+  // TODO: is this better? Or is a "vis_block" better?
+  std::unique_ptr<Expr> &get_break_expr ()
+  {
+    rust_assert (has_break_expr ());
+    return break_expr;
+  }
+
+  const std::vector<Attribute> &get_outer_attrs () const { return outer_attrs; }
+  std::vector<Attribute> &get_outer_attrs () { return outer_attrs; }
+
+  void set_outer_attrs (std::vector<Attribute> new_attrs) override
+  {
+    outer_attrs = std::move (new_attrs);
+  }
+
+  Lifetime &get_label () { return label; }
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  BreakExpr *clone_expr_without_block_impl () const override
+  {
+    return new BreakExpr (*this);
+  }
+};
+
+// Base range expression AST node object - abstract
+class RangeExpr : public ExprWithoutBlock
+{
+  Location locus;
+
+protected:
+  // outer attributes not allowed before range expressions
+  RangeExpr (Location locus) : locus (locus) {}
+
+public:
+  Location get_locus () const override final { return locus; }
+
+  // should never be called - error if called
+  void set_outer_attrs (std::vector<Attribute> /* new_attrs */) override
+  {
+    rust_assert (false);
+  }
+};
+
+// Range from (inclusive) and to (exclusive) expression AST node object
+// aka RangeExpr; constructs a std::ops::Range object
+class RangeFromToExpr : public RangeExpr
+{
+  std::unique_ptr<Expr> from;
+  std::unique_ptr<Expr> to;
+
+public:
+  std::string as_string () const override;
+
+  RangeFromToExpr (std::unique_ptr<Expr> range_from,
+		   std::unique_ptr<Expr> range_to, Location locus)
+    : RangeExpr (locus), from (std::move (range_from)),
+      to (std::move (range_to))
+  {}
+
+  // Copy constructor with cloning
+  RangeFromToExpr (RangeFromToExpr const &other) : RangeExpr (other)
+  {
+    // guard to prevent null dereference (only required if error state)
+    if (other.from != nullptr)
+      from = other.from->clone_expr ();
+    if (other.to != nullptr)
+      to = other.to->clone_expr ();
+  }
+
+  // Overload assignment operator to clone unique pointers
+  RangeFromToExpr &operator= (RangeFromToExpr const &other)
+  {
+    RangeExpr::operator= (other);
+
+    // guard to prevent null dereference (only required if error state)
+    if (other.from != nullptr)
+      from = other.from->clone_expr ();
+    else
+      from = nullptr;
+    if (other.to != nullptr)
+      to = other.to->clone_expr ();
+    else
+      to = nullptr;
+
+    return *this;
+  }
+
+  // move constructors
+  RangeFromToExpr (RangeFromToExpr &&other) = default;
+  RangeFromToExpr &operator= (RangeFromToExpr &&other) = default;
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // Invalid if either expr is null, so base stripping on that.
+  void mark_for_strip () override
+  {
+    from = nullptr;
+    to = nullptr;
+  }
+  bool is_marked_for_strip () const override
+  {
+    return from == nullptr && to == nullptr;
+  }
+
+  // TODO: is this better? Or is a "vis_block" better?
+  std::unique_ptr<Expr> &get_from_expr ()
+  {
+    rust_assert (from != nullptr);
+    return from;
+  }
+
+  // TODO: is this better? Or is a "vis_block" better?
+  std::unique_ptr<Expr> &get_to_expr ()
+  {
+    rust_assert (to != nullptr);
+    return to;
+  }
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  RangeFromToExpr *clone_expr_without_block_impl () const override
+  {
+    return new RangeFromToExpr (*this);
+  }
+};
+
+// Range from (inclusive) expression AST node object
+// constructs a std::ops::RangeFrom object
+class RangeFromExpr : public RangeExpr
+{
+  std::unique_ptr<Expr> from;
+
+public:
+  std::string as_string () const override;
+
+  RangeFromExpr (std::unique_ptr<Expr> range_from, Location locus)
+    : RangeExpr (locus), from (std::move (range_from))
+  {}
+
+  // Copy constructor with clone
+  RangeFromExpr (RangeFromExpr const &other) : RangeExpr (other)
+  {
+    // guard to prevent null dereference (only required if error state)
+    if (other.from != nullptr)
+      from = other.from->clone_expr ();
+  }
+
+  // Overload assignment operator to clone unique_ptr
+  RangeFromExpr &operator= (RangeFromExpr const &other)
+  {
+    RangeExpr::operator= (other);
+
+    // guard to prevent null dereference (only required if error state)
+    if (other.from != nullptr)
+      from = other.from->clone_expr ();
+    else
+      from = nullptr;
+
+    return *this;
+  }
+
+  // move constructors
+  RangeFromExpr (RangeFromExpr &&other) = default;
+  RangeFromExpr &operator= (RangeFromExpr &&other) = default;
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // Invalid if expr is null, so base stripping on that.
+  void mark_for_strip () override { from = nullptr; }
+  bool is_marked_for_strip () const override { return from == nullptr; }
+
+  // TODO: is this better? Or is a "vis_block" better?
+  std::unique_ptr<Expr> &get_from_expr ()
+  {
+    rust_assert (from != nullptr);
+    return from;
+  }
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  RangeFromExpr *clone_expr_without_block_impl () const override
+  {
+    return new RangeFromExpr (*this);
+  }
+};
+
+// Range to (exclusive) expression AST node object
+// constructs a std::ops::RangeTo object
+class RangeToExpr : public RangeExpr
+{
+  std::unique_ptr<Expr> to;
+
+public:
+  std::string as_string () const override;
+
+  // outer attributes not allowed
+  RangeToExpr (std::unique_ptr<Expr> range_to, Location locus)
+    : RangeExpr (locus), to (std::move (range_to))
+  {}
+
+  // Copy constructor with clone
+  RangeToExpr (RangeToExpr const &other) : RangeExpr (other)
+  {
+    // guard to prevent null dereference (only required if error state)
+    if (other.to != nullptr)
+      to = other.to->clone_expr ();
+  }
+
+  // Overload assignment operator to clone unique_ptr
+  RangeToExpr &operator= (RangeToExpr const &other)
+  {
+    RangeExpr::operator= (other);
+
+    // guard to prevent null dereference (only required if error state)
+    if (other.to != nullptr)
+      to = other.to->clone_expr ();
+    else
+      to = nullptr;
+
+    return *this;
+  }
+
+  // move constructors
+  RangeToExpr (RangeToExpr &&other) = default;
+  RangeToExpr &operator= (RangeToExpr &&other) = default;
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // Invalid if expr is null, so base stripping on that.
+  void mark_for_strip () override { to = nullptr; }
+  bool is_marked_for_strip () const override { return to == nullptr; }
+
+  // TODO: is this better? Or is a "vis_block" better?
+  std::unique_ptr<Expr> &get_to_expr ()
+  {
+    rust_assert (to != nullptr);
+    return to;
+  }
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  RangeToExpr *clone_expr_without_block_impl () const override
+  {
+    return new RangeToExpr (*this);
+  }
+};
+
+// Full range expression AST node object
+// constructs a std::ops::RangeFull object
+class RangeFullExpr : public RangeExpr
+{
+  // TODO: find another way to store this to save memory?
+  bool marked_for_strip = false;
+
+public:
+  std::string as_string () const override;
+
+  RangeFullExpr (Location locus) : RangeExpr (locus) {}
+  // outer attributes not allowed
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // Can't think of any invalid invariants, so store boolean.
+  void mark_for_strip () override { marked_for_strip = true; }
+  bool is_marked_for_strip () const override { return marked_for_strip; }
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  RangeFullExpr *clone_expr_without_block_impl () const override
+  {
+    return new RangeFullExpr (*this);
+  }
+};
+
+// Range from (inclusive) and to (inclusive) expression AST node object
+// aka RangeInclusiveExpr; constructs a std::ops::RangeInclusive object
+class RangeFromToInclExpr : public RangeExpr
+{
+  std::unique_ptr<Expr> from;
+  std::unique_ptr<Expr> to;
+
+public:
+  std::string as_string () const override;
+
+  RangeFromToInclExpr (std::unique_ptr<Expr> range_from,
+		       std::unique_ptr<Expr> range_to, Location locus)
+    : RangeExpr (locus), from (std::move (range_from)),
+      to (std::move (range_to))
+  {}
+  // outer attributes not allowed
+
+  // Copy constructor with clone
+  RangeFromToInclExpr (RangeFromToInclExpr const &other) : RangeExpr (other)
+  {
+    // guard to prevent null dereference (only required if error state)
+    if (other.from != nullptr)
+      from = other.from->clone_expr ();
+    if (other.to != nullptr)
+      to = other.to->clone_expr ();
+  }
+
+  // Overload assignment operator to use clone
+  RangeFromToInclExpr &operator= (RangeFromToInclExpr const &other)
+  {
+    RangeExpr::operator= (other);
+
+    // guard to prevent null dereference (only required if error state)
+    if (other.from != nullptr)
+      from = other.from->clone_expr ();
+    else
+      from = nullptr;
+    if (other.to != nullptr)
+      to = other.to->clone_expr ();
+    else
+      to = nullptr;
+
+    return *this;
+  }
+
+  // move constructors
+  RangeFromToInclExpr (RangeFromToInclExpr &&other) = default;
+  RangeFromToInclExpr &operator= (RangeFromToInclExpr &&other) = default;
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // Invalid if either expr is null, so base stripping on that.
+  void mark_for_strip () override
+  {
+    from = nullptr;
+    to = nullptr;
+  }
+  bool is_marked_for_strip () const override
+  {
+    return from == nullptr && to == nullptr;
+  }
+
+  // TODO: is this better? Or is a "vis_block" better?
+  std::unique_ptr<Expr> &get_from_expr ()
+  {
+    rust_assert (from != nullptr);
+    return from;
+  }
+
+  // TODO: is this better? Or is a "vis_block" better?
+  std::unique_ptr<Expr> &get_to_expr ()
+  {
+    rust_assert (to != nullptr);
+    return to;
+  }
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  RangeFromToInclExpr *clone_expr_without_block_impl () const override
+  {
+    return new RangeFromToInclExpr (*this);
+  }
+};
+
+// Range to (inclusive) expression AST node object
+// aka RangeToInclusiveExpr; constructs a std::ops::RangeToInclusive object
+class RangeToInclExpr : public RangeExpr
+{
+  std::unique_ptr<Expr> to;
+
+public:
+  std::string as_string () const override;
+
+  RangeToInclExpr (std::unique_ptr<Expr> range_to, Location locus)
+    : RangeExpr (locus), to (std::move (range_to))
+  {}
+  // outer attributes not allowed
+
+  // Copy constructor with clone
+  RangeToInclExpr (RangeToInclExpr const &other) : RangeExpr (other)
+  {
+    // guard to prevent null dereference (only required if error state)
+    if (other.to != nullptr)
+      to = other.to->clone_expr ();
+  }
+
+  // Overload assignment operator to clone pointer
+  RangeToInclExpr &operator= (RangeToInclExpr const &other)
+  {
+    RangeExpr::operator= (other);
+
+    // guard to prevent null dereference (only required if error state)
+    if (other.to != nullptr)
+      to = other.to->clone_expr ();
+    else
+      to = nullptr;
+
+    return *this;
+  }
+
+  // move constructors
+  RangeToInclExpr (RangeToInclExpr &&other) = default;
+  RangeToInclExpr &operator= (RangeToInclExpr &&other) = default;
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // Invalid if expr is null, so base stripping on that.
+  void mark_for_strip () override { to = nullptr; }
+  bool is_marked_for_strip () const override { return to == nullptr; }
+
+  // TODO: is this better? Or is a "vis_block" better?
+  std::unique_ptr<Expr> &get_to_expr ()
+  {
+    rust_assert (to != nullptr);
+    return to;
+  }
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  RangeToInclExpr *clone_expr_without_block_impl () const override
+  {
+    return new RangeToInclExpr (*this);
+  }
+};
+
+// Return expression AST node representation
+class ReturnExpr : public ExprWithoutBlock
+{
+  std::vector<Attribute> outer_attrs;
+  std::unique_ptr<Expr> return_expr;
+  Location locus;
+
+  // TODO: find another way to store this to save memory?
+  bool marked_for_strip = false;
+
+public:
+  std::string as_string () const override;
+
+  /* Returns whether the object has an expression returned (i.e. not void return
+   * type). */
+  bool has_returned_expr () const { return return_expr != nullptr; }
+
+  // Constructor for ReturnExpr.
+  ReturnExpr (std::unique_ptr<Expr> returned_expr,
+	      std::vector<Attribute> outer_attribs, Location locus)
+    : outer_attrs (std::move (outer_attribs)),
+      return_expr (std::move (returned_expr)), locus (locus)
+  {}
+
+  // Copy constructor with clone
+  ReturnExpr (ReturnExpr const &other)
+    : ExprWithoutBlock (other), outer_attrs (other.outer_attrs),
+      locus (other.locus), marked_for_strip (other.marked_for_strip)
+  {
+    // guard to protect from null pointer dereference
+    if (other.return_expr != nullptr)
+      return_expr = other.return_expr->clone_expr ();
+  }
+
+  // Overloaded assignment operator to clone return_expr pointer
+  ReturnExpr &operator= (ReturnExpr const &other)
+  {
+    ExprWithoutBlock::operator= (other);
+    locus = other.locus;
+    marked_for_strip = other.marked_for_strip;
+    outer_attrs = other.outer_attrs;
+
+    // guard to protect from null pointer dereference
+    if (other.return_expr != nullptr)
+      return_expr = other.return_expr->clone_expr ();
+    else
+      return_expr = nullptr;
+
+    return *this;
+  }
+
+  // move constructors
+  ReturnExpr (ReturnExpr &&other) = default;
+  ReturnExpr &operator= (ReturnExpr &&other) = default;
+
+  Location get_locus () const override final { return locus; }
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // Can't think of any invalid invariants, so store boolean.
+  void mark_for_strip () override { marked_for_strip = true; }
+  bool is_marked_for_strip () const override { return marked_for_strip; }
+
+  // TODO: is this better? Or is a "vis_block" better?
+  std::unique_ptr<Expr> &get_returned_expr ()
+  {
+    rust_assert (return_expr != nullptr);
+    return return_expr;
+  }
+
+  const std::vector<Attribute> &get_outer_attrs () const { return outer_attrs; }
+  std::vector<Attribute> &get_outer_attrs () { return outer_attrs; }
+
+  void set_outer_attrs (std::vector<Attribute> new_attrs) override
+  {
+    outer_attrs = std::move (new_attrs);
+  }
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  ReturnExpr *clone_expr_without_block_impl () const override
+  {
+    return new ReturnExpr (*this);
+  }
+};
+
+// Forward decl - defined in rust-macro.h
+class MacroInvocation;
+
+// An unsafe block AST node
+class UnsafeBlockExpr : public ExprWithBlock
+{
+  std::vector<Attribute> outer_attrs;
+  // Or just have it extend BlockExpr
+  std::unique_ptr<BlockExpr> expr;
+  Location locus;
+
+public:
+  std::string as_string () const override;
+
+  UnsafeBlockExpr (std::unique_ptr<BlockExpr> block_expr,
+		   std::vector<Attribute> outer_attribs, Location locus)
+    : outer_attrs (std::move (outer_attribs)), expr (std::move (block_expr)),
+      locus (locus)
+  {}
+
+  // Copy constructor with clone
+  UnsafeBlockExpr (UnsafeBlockExpr const &other)
+    : ExprWithBlock (other), outer_attrs (other.outer_attrs),
+      locus (other.locus)
+  {
+    // guard to prevent null dereference (only required if error state)
+    if (other.expr != nullptr)
+      expr = other.expr->clone_block_expr ();
+  }
+
+  // Overloaded assignment operator to clone
+  UnsafeBlockExpr &operator= (UnsafeBlockExpr const &other)
+  {
+    ExprWithBlock::operator= (other);
+    locus = other.locus;
+    outer_attrs = other.outer_attrs;
+
+    // guard to prevent null dereference (only required if error state)
+    if (other.expr != nullptr)
+      expr = other.expr->clone_block_expr ();
+    else
+      expr = nullptr;
+
+    return *this;
+  }
+
+  // move constructors
+  UnsafeBlockExpr (UnsafeBlockExpr &&other) = default;
+  UnsafeBlockExpr &operator= (UnsafeBlockExpr &&other) = default;
+
+  Location get_locus () const override final { return locus; }
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // Invalid if block is null, so base stripping on that.
+  void mark_for_strip () override { expr = nullptr; }
+  bool is_marked_for_strip () const override { return expr == nullptr; }
+
+  // TODO: is this better? Or is a "vis_block" better?
+  std::unique_ptr<BlockExpr> &get_block_expr ()
+  {
+    rust_assert (expr != nullptr);
+    return expr;
+  }
+
+  const std::vector<Attribute> &get_outer_attrs () const { return outer_attrs; }
+  std::vector<Attribute> &get_outer_attrs () { return outer_attrs; }
+
+  void set_outer_attrs (std::vector<Attribute> new_attrs) override
+  {
+    outer_attrs = std::move (new_attrs);
+  }
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  UnsafeBlockExpr *clone_expr_with_block_impl () const override
+  {
+    return new UnsafeBlockExpr (*this);
+  }
+};
+
+// Loop label expression AST node used with break and continue expressions
+// TODO: inline?
+class LoopLabel /*: public Node*/
+{
+  Lifetime label; // or type LIFETIME_OR_LABEL
+  Location locus;
+
+  NodeId node_id;
+
+public:
+  std::string as_string () const;
+
+  LoopLabel (Lifetime loop_label, Location locus = Location ())
+    : label (std::move (loop_label)), locus (locus),
+      node_id (Analysis::Mappings::get ()->get_next_node_id ())
+  {}
+
+  // Returns whether the LoopLabel is in an error state.
+  bool is_error () const { return label.is_error (); }
+
+  // Creates an error state LoopLabel.
+  static LoopLabel error () { return LoopLabel (Lifetime::error ()); }
+
+  Location get_locus () const { return locus; }
+
+  Lifetime &get_lifetime () { return label; }
+
+  NodeId get_node_id () const { return node_id; }
+};
+
+// Base loop expression AST node - aka LoopExpr
+class BaseLoopExpr : public ExprWithBlock
+{
+protected:
+  // protected to allow subclasses better use of them
+  std::vector<Attribute> outer_attrs;
+  LoopLabel loop_label;
+  std::unique_ptr<BlockExpr> loop_block;
+
+private:
+  Location locus;
+
+protected:
+  // Constructor for BaseLoopExpr
+  BaseLoopExpr (std::unique_ptr<BlockExpr> loop_block, Location locus,
+		LoopLabel loop_label = LoopLabel::error (),
+		std::vector<Attribute> outer_attribs
+		= std::vector<Attribute> ())
+    : outer_attrs (std::move (outer_attribs)),
+      loop_label (std::move (loop_label)), loop_block (std::move (loop_block)),
+      locus (locus)
+  {}
+
+  // Copy constructor for BaseLoopExpr with clone
+  BaseLoopExpr (BaseLoopExpr const &other)
+    : ExprWithBlock (other), outer_attrs (other.outer_attrs),
+      loop_label (other.loop_label), locus (other.locus)
+  {
+    // guard to prevent null dereference (only required if error state)
+    if (other.loop_block != nullptr)
+      loop_block = other.loop_block->clone_block_expr ();
+  }
+
+  // Overloaded assignment operator to clone
+  BaseLoopExpr &operator= (BaseLoopExpr const &other)
+  {
+    ExprWithBlock::operator= (other);
+    loop_label = other.loop_label;
+    locus = other.locus;
+    outer_attrs = other.outer_attrs;
+
+    // guard to prevent null dereference (only required if error state)
+    if (other.loop_block != nullptr)
+      loop_block = other.loop_block->clone_block_expr ();
+    else
+      loop_block = nullptr;
+
+    return *this;
+  }
+
+  // move constructors
+  BaseLoopExpr (BaseLoopExpr &&other) = default;
+  BaseLoopExpr &operator= (BaseLoopExpr &&other) = default;
+
+public:
+  bool has_loop_label () const { return !loop_label.is_error (); }
+
+  LoopLabel &get_loop_label () { return loop_label; }
+
+  Location get_locus () const override final { return locus; }
+
+  // Invalid if loop block is null, so base stripping on that.
+  void mark_for_strip () override { loop_block = nullptr; }
+  bool is_marked_for_strip () const override { return loop_block == nullptr; }
+
+  // TODO: is this better? Or is a "vis_block" better?
+  std::unique_ptr<BlockExpr> &get_loop_block ()
+  {
+    rust_assert (loop_block != nullptr);
+    return loop_block;
+  }
+
+  const std::vector<Attribute> &get_outer_attrs () const { return outer_attrs; }
+  std::vector<Attribute> &get_outer_attrs () { return outer_attrs; }
+
+  void set_outer_attrs (std::vector<Attribute> new_attrs) override
+  {
+    outer_attrs = std::move (new_attrs);
+  }
+};
+
+// 'Loop' expression (i.e. the infinite loop) AST node
+class LoopExpr : public BaseLoopExpr
+{
+public:
+  std::string as_string () const override;
+
+  // Constructor for LoopExpr
+  LoopExpr (std::unique_ptr<BlockExpr> loop_block, Location locus,
+	    LoopLabel loop_label = LoopLabel::error (),
+	    std::vector<Attribute> outer_attribs = std::vector<Attribute> ())
+    : BaseLoopExpr (std::move (loop_block), locus, std::move (loop_label),
+		    std::move (outer_attribs))
+  {}
+
+  void accept_vis (ASTVisitor &vis) override;
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  LoopExpr *clone_expr_with_block_impl () const override
+  {
+    return new LoopExpr (*this);
+  }
+};
+
+// While loop expression AST node (predicate loop)
+class WhileLoopExpr : public BaseLoopExpr
+{
+  std::unique_ptr<Expr> condition;
+
+public:
+  std::string as_string () const override;
+
+  // Constructor for while loop with loop label
+  WhileLoopExpr (std::unique_ptr<Expr> loop_condition,
+		 std::unique_ptr<BlockExpr> loop_block, Location locus,
+		 LoopLabel loop_label = LoopLabel::error (),
+		 std::vector<Attribute> outer_attribs
+		 = std::vector<Attribute> ())
+    : BaseLoopExpr (std::move (loop_block), locus, std::move (loop_label),
+		    std::move (outer_attribs)),
+      condition (std::move (loop_condition))
+  {}
+
+  // Copy constructor with clone
+  WhileLoopExpr (WhileLoopExpr const &other)
+    : BaseLoopExpr (other), condition (other.condition->clone_expr ())
+  {}
+
+  // Overloaded assignment operator to clone
+  WhileLoopExpr &operator= (WhileLoopExpr const &other)
+  {
+    BaseLoopExpr::operator= (other);
+    condition = other.condition->clone_expr ();
+    // loop_block = other.loop_block->clone_block_expr();
+    // loop_label = other.loop_label;
+    // outer_attrs = other.outer_attrs;
+
+    return *this;
+  }
+
+  // move constructors
+  WhileLoopExpr (WhileLoopExpr &&other) = default;
+  WhileLoopExpr &operator= (WhileLoopExpr &&other) = default;
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // TODO: is this better? Or is a "vis_block" better?
+  std::unique_ptr<Expr> &get_predicate_expr ()
+  {
+    rust_assert (condition != nullptr);
+    return condition;
+  }
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  WhileLoopExpr *clone_expr_with_block_impl () const override
+  {
+    return new WhileLoopExpr (*this);
+  }
+};
+
+// While let loop expression AST node (predicate pattern loop)
+class WhileLetLoopExpr : public BaseLoopExpr
+{
+  // MatchArmPatterns patterns;
+  std::vector<std::unique_ptr<Pattern> > match_arm_patterns; // inlined
+  std::unique_ptr<Expr> scrutinee;
+
+public:
+  std::string as_string () const override;
+
+  // Constructor with a loop label
+  WhileLetLoopExpr (std::vector<std::unique_ptr<Pattern> > match_arm_patterns,
+		    std::unique_ptr<Expr> scrutinee,
+		    std::unique_ptr<BlockExpr> loop_block, Location locus,
+		    LoopLabel loop_label = LoopLabel::error (),
+		    std::vector<Attribute> outer_attribs
+		    = std::vector<Attribute> ())
+    : BaseLoopExpr (std::move (loop_block), locus, std::move (loop_label),
+		    std::move (outer_attribs)),
+      match_arm_patterns (std::move (match_arm_patterns)),
+      scrutinee (std::move (scrutinee))
+  {}
+
+  // Copy constructor with clone
+  WhileLetLoopExpr (WhileLetLoopExpr const &other)
+    : BaseLoopExpr (other),
+      /*match_arm_patterns(other.match_arm_patterns),*/ scrutinee (
+	other.scrutinee->clone_expr ())
+  {
+    match_arm_patterns.reserve (other.match_arm_patterns.size ());
+    for (const auto &e : other.match_arm_patterns)
+      match_arm_patterns.push_back (e->clone_pattern ());
+  }
+
+  // Overloaded assignment operator to clone pointers
+  WhileLetLoopExpr &operator= (WhileLetLoopExpr const &other)
+  {
+    BaseLoopExpr::operator= (other);
+    // match_arm_patterns = other.match_arm_patterns;
+    scrutinee = other.scrutinee->clone_expr ();
+    // loop_block = other.loop_block->clone_block_expr();
+    // loop_label = other.loop_label;
+    // outer_attrs = other.outer_attrs;
+
+    match_arm_patterns.reserve (other.match_arm_patterns.size ());
+    for (const auto &e : other.match_arm_patterns)
+      match_arm_patterns.push_back (e->clone_pattern ());
+
+    return *this;
+  }
+
+  // move constructors
+  WhileLetLoopExpr (WhileLetLoopExpr &&other) = default;
+  WhileLetLoopExpr &operator= (WhileLetLoopExpr &&other) = default;
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // TODO: is this better? Or is a "vis_block" better?
+  std::unique_ptr<Expr> &get_scrutinee_expr ()
+  {
+    rust_assert (scrutinee != nullptr);
+    return scrutinee;
+  }
+
+  // TODO: this mutable getter seems really dodgy. Think up better way.
+  const std::vector<std::unique_ptr<Pattern> > &get_patterns () const
+  {
+    return match_arm_patterns;
+  }
+  std::vector<std::unique_ptr<Pattern> > &get_patterns ()
+  {
+    return match_arm_patterns;
+  }
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  WhileLetLoopExpr *clone_expr_with_block_impl () const override
+  {
+    return new WhileLetLoopExpr (*this);
+  }
+};
+
+// For loop expression AST node (iterator loop)
+class ForLoopExpr : public BaseLoopExpr
+{
+  std::unique_ptr<Pattern> pattern;
+  std::unique_ptr<Expr> iterator_expr;
+
+public:
+  std::string as_string () const override;
+
+  // Constructor with loop label
+  ForLoopExpr (std::unique_ptr<Pattern> loop_pattern,
+	       std::unique_ptr<Expr> iterator_expr,
+	       std::unique_ptr<BlockExpr> loop_body, Location locus,
+	       LoopLabel loop_label = LoopLabel::error (),
+	       std::vector<Attribute> outer_attribs = std::vector<Attribute> ())
+    : BaseLoopExpr (std::move (loop_body), locus, std::move (loop_label),
+		    std::move (outer_attribs)),
+      pattern (std::move (loop_pattern)),
+      iterator_expr (std::move (iterator_expr))
+  {}
+
+  // Copy constructor with clone
+  ForLoopExpr (ForLoopExpr const &other)
+    : BaseLoopExpr (other), pattern (other.pattern->clone_pattern ()),
+      iterator_expr (other.iterator_expr->clone_expr ())
+  {}
+
+  // Overloaded assignment operator to clone
+  ForLoopExpr &operator= (ForLoopExpr const &other)
+  {
+    BaseLoopExpr::operator= (other);
+    pattern = other.pattern->clone_pattern ();
+    iterator_expr = other.iterator_expr->clone_expr ();
+    /*loop_block = other.loop_block->clone_block_expr();
+    loop_label = other.loop_label;
+    outer_attrs = other.outer_attrs;*/
+
+    return *this;
+  }
+
+  // move constructors
+  ForLoopExpr (ForLoopExpr &&other) = default;
+  ForLoopExpr &operator= (ForLoopExpr &&other) = default;
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // TODO: is this better? Or is a "vis_block" better?
+  std::unique_ptr<Expr> &get_iterator_expr ()
+  {
+    rust_assert (iterator_expr != nullptr);
+    return iterator_expr;
+  }
+
+  // TODO: is this better? Or is a "vis_block" better?
+  std::unique_ptr<Pattern> &get_pattern ()
+  {
+    rust_assert (pattern != nullptr);
+    return pattern;
+  }
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  ForLoopExpr *clone_expr_with_block_impl () const override
+  {
+    return new ForLoopExpr (*this);
+  }
+};
+
+// forward decl for IfExpr
+class IfLetExpr;
+
+// Base if expression with no "else" or "if let" AST node
+class IfExpr : public ExprWithBlock
+{
+  std::vector<Attribute> outer_attrs;
+  std::unique_ptr<Expr> condition;
+  std::unique_ptr<BlockExpr> if_block;
+  Location locus;
+
+public:
+  std::string as_string () const override;
+
+  IfExpr (std::unique_ptr<Expr> condition, std::unique_ptr<BlockExpr> if_block,
+	  std::vector<Attribute> outer_attrs, Location locus)
+    : outer_attrs (std::move (outer_attrs)), condition (std::move (condition)),
+      if_block (std::move (if_block)), locus (locus)
+  {}
+  // outer attributes are never allowed on IfExprs
+
+  // Copy constructor with clone
+  IfExpr (IfExpr const &other)
+    : ExprWithBlock (other), outer_attrs (other.outer_attrs),
+      locus (other.locus)
+  {
+    // guard to prevent null dereference (only required if error state)
+    if (other.condition != nullptr)
+      condition = other.condition->clone_expr ();
+    if (other.if_block != nullptr)
+      if_block = other.if_block->clone_block_expr ();
+  }
+
+  // Overloaded assignment operator to clone expressions
+  IfExpr &operator= (IfExpr const &other)
+  {
+    ExprWithBlock::operator= (other);
+    outer_attrs = other.outer_attrs;
+    locus = other.locus;
+
+    // guard to prevent null dereference (only required if error state)
+    if (other.condition != nullptr)
+      condition = other.condition->clone_expr ();
+    else
+      condition = nullptr;
+    if (other.if_block != nullptr)
+      if_block = other.if_block->clone_block_expr ();
+    else
+      if_block = nullptr;
+
+    return *this;
+  }
+
+  // move constructors
+  IfExpr (IfExpr &&other) = default;
+  IfExpr &operator= (IfExpr &&other) = default;
+
+  // Unique pointer custom clone function
+  std::unique_ptr<IfExpr> clone_if_expr () const
+  {
+    return std::unique_ptr<IfExpr> (clone_if_expr_impl ());
+  }
+
+  /* Note that multiple "else if"s are handled via nested ASTs rather than a
+   * vector of else ifs - i.e. not like a switch statement. TODO - is this a
+   * better approach? or does it not parse correctly and have downsides? */
+
+  Location get_locus () const override final { return locus; }
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  void vis_if_condition (ASTVisitor &vis) { condition->accept_vis (vis); }
+  void vis_if_block (ASTVisitor &vis) { if_block->accept_vis (vis); }
+
+  // TODO: is this better? Or is a "vis_block" better?
+  std::unique_ptr<Expr> &get_condition_expr ()
+  {
+    rust_assert (condition != nullptr);
+    return condition;
+  }
+
+  // TODO: is this better? Or is a "vis_block" better?
+  std::unique_ptr<BlockExpr> &get_if_block ()
+  {
+    rust_assert (if_block != nullptr);
+    return if_block;
+  }
+
+  // Invalid if if block or condition is null, so base stripping on that.
+  void mark_for_strip () override
+  {
+    if_block = nullptr;
+    condition = nullptr;
+  }
+  bool is_marked_for_strip () const override
+  {
+    return if_block == nullptr && condition == nullptr;
+  }
+
+  void set_outer_attrs (std::vector<Attribute> new_attrs) override
+  {
+    outer_attrs = std::move (new_attrs);
+  }
+
+  // TODO: this mutable getter seems really dodgy. Think up better way.
+  const std::vector<Attribute> &get_outer_attrs () const { return outer_attrs; }
+  std::vector<Attribute> &get_outer_attrs () { return outer_attrs; }
+
+protected:
+  // Base clone function but still concrete as concrete base class
+  virtual IfExpr *clone_if_expr_impl () const { return new IfExpr (*this); }
+
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  IfExpr *clone_expr_with_block_impl () const final override
+  {
+    return clone_if_expr_impl ();
+  }
+};
+
+// If expression with an ending "else" expression AST node (trailing)
+class IfExprConseqElse : public IfExpr
+{
+  std::unique_ptr<BlockExpr> else_block;
+
+public:
+  std::string as_string () const override;
+
+  IfExprConseqElse (std::unique_ptr<Expr> condition,
+		    std::unique_ptr<BlockExpr> if_block,
+		    std::unique_ptr<BlockExpr> else_block,
+		    std::vector<Attribute> outer_attrs, Location locus)
+    : IfExpr (std::move (condition), std::move (if_block),
+	      std::move (outer_attrs), locus),
+      else_block (std::move (else_block))
+  {}
+  // again, outer attributes not allowed
+
+  // Copy constructor with clone
+  IfExprConseqElse (IfExprConseqElse const &other)
+    : IfExpr (other), else_block (other.else_block->clone_block_expr ())
+  {}
+
+  // Overloaded assignment operator with cloning
+  IfExprConseqElse &operator= (IfExprConseqElse const &other)
+  {
+    IfExpr::operator= (other);
+    // condition = other.condition->clone_expr();
+    // if_block = other.if_block->clone_block_expr();
+    else_block = other.else_block->clone_block_expr ();
+
+    return *this;
+  }
+
+  // move constructors
+  IfExprConseqElse (IfExprConseqElse &&other) = default;
+  IfExprConseqElse &operator= (IfExprConseqElse &&other) = default;
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  void vis_else_block (ASTVisitor &vis) { else_block->accept_vis (vis); }
+
+  // TODO: is this better? Or is a "vis_block" better?
+  std::unique_ptr<BlockExpr> &get_else_block ()
+  {
+    rust_assert (else_block != nullptr);
+    return else_block;
+  }
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  IfExprConseqElse *clone_if_expr_impl () const override
+  {
+    return new IfExprConseqElse (*this);
+  }
+};
+
+// If expression with an ending "else if" expression AST node
+class IfExprConseqIf : public IfExpr
+{
+  std::unique_ptr<IfExpr> conseq_if_expr;
+
+public:
+  std::string as_string () const override;
+
+  IfExprConseqIf (std::unique_ptr<Expr> condition,
+		  std::unique_ptr<BlockExpr> if_block,
+		  std::unique_ptr<IfExpr> conseq_if_expr,
+		  std::vector<Attribute> outer_attrs, Location locus)
+    : IfExpr (std::move (condition), std::move (if_block),
+	      std::move (outer_attrs), locus),
+      conseq_if_expr (std::move (conseq_if_expr))
+  {}
+  // outer attributes not allowed
+
+  // Copy constructor with clone
+  IfExprConseqIf (IfExprConseqIf const &other)
+    : IfExpr (other), conseq_if_expr (other.conseq_if_expr->clone_if_expr ())
+  {}
+
+  // Overloaded assignment operator to use clone
+  IfExprConseqIf &operator= (IfExprConseqIf const &other)
+  {
+    IfExpr::operator= (other);
+    // condition = other.condition->clone_expr();
+    // if_block = other.if_block->clone_block_expr();
+    conseq_if_expr = other.conseq_if_expr->clone_if_expr ();
+
+    return *this;
+  }
+
+  // move constructors
+  IfExprConseqIf (IfExprConseqIf &&other) = default;
+  IfExprConseqIf &operator= (IfExprConseqIf &&other) = default;
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  void vis_conseq_if_expr (ASTVisitor &vis)
+  {
+    conseq_if_expr->accept_vis (vis);
+  }
+
+  // TODO: is this better? Or is a "vis_block" better?
+  std::unique_ptr<IfExpr> &get_conseq_if_expr ()
+  {
+    rust_assert (conseq_if_expr != nullptr);
+    return conseq_if_expr;
+  }
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  IfExprConseqIf *clone_if_expr_impl () const override
+  {
+    return new IfExprConseqIf (*this);
+  }
+};
+
+// Basic "if let" expression AST node with no else
+class IfLetExpr : public ExprWithBlock
+{
+  std::vector<Attribute> outer_attrs;
+  std::vector<std::unique_ptr<Pattern> > match_arm_patterns; // inlined
+  std::unique_ptr<Expr> value;
+  std::unique_ptr<BlockExpr> if_block;
+  Location locus;
+
+public:
+  std::string as_string () const override;
+
+  IfLetExpr (std::vector<std::unique_ptr<Pattern> > match_arm_patterns,
+	     std::unique_ptr<Expr> value, std::unique_ptr<BlockExpr> if_block,
+	     std::vector<Attribute> outer_attrs, Location locus)
+    : outer_attrs (std::move (outer_attrs)),
+      match_arm_patterns (std::move (match_arm_patterns)),
+      value (std::move (value)), if_block (std::move (if_block)), locus (locus)
+  {}
+
+  // copy constructor with clone
+  IfLetExpr (IfLetExpr const &other)
+    : ExprWithBlock (other), outer_attrs (other.outer_attrs),
+      locus (other.locus)
+  {
+    // guard to prevent null dereference (only required if error state)
+    if (other.value != nullptr)
+      value = other.value->clone_expr ();
+    if (other.if_block != nullptr)
+      if_block = other.if_block->clone_block_expr ();
+
+    match_arm_patterns.reserve (other.match_arm_patterns.size ());
+    for (const auto &e : other.match_arm_patterns)
+      match_arm_patterns.push_back (e->clone_pattern ());
+  }
+
+  // overload assignment operator to clone
+  IfLetExpr &operator= (IfLetExpr const &other)
+  {
+    ExprWithBlock::operator= (other);
+    outer_attrs = other.outer_attrs;
+    locus = other.locus;
+
+    // guard to prevent null dereference (only required if error state)
+    if (other.value != nullptr)
+      value = other.value->clone_expr ();
+    else
+      value = nullptr;
+    if (other.if_block != nullptr)
+      if_block = other.if_block->clone_block_expr ();
+    else
+      if_block = nullptr;
+
+    match_arm_patterns.reserve (other.match_arm_patterns.size ());
+    for (const auto &e : other.match_arm_patterns)
+      match_arm_patterns.push_back (e->clone_pattern ());
+
+    return *this;
+  }
+
+  // move constructors
+  IfLetExpr (IfLetExpr &&other) = default;
+  IfLetExpr &operator= (IfLetExpr &&other) = default;
+
+  // Unique pointer custom clone function
+  std::unique_ptr<IfLetExpr> clone_if_let_expr () const
+  {
+    return std::unique_ptr<IfLetExpr> (clone_if_let_expr_impl ());
+  }
+
+  Location get_locus () const override final { return locus; }
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // Invalid if block or value is null, so base stripping on that.
+  void mark_for_strip () override
+  {
+    if_block = nullptr;
+    value = nullptr;
+  }
+  bool is_marked_for_strip () const override
+  {
+    return if_block == nullptr && value == nullptr;
+  }
+
+  // TODO: is this better? Or is a "vis_block" better?
+  std::unique_ptr<Expr> &get_value_expr ()
+  {
+    rust_assert (value != nullptr);
+    return value;
+  }
+
+  // TODO: is this better? Or is a "vis_block" better?
+  std::unique_ptr<BlockExpr> &get_if_block ()
+  {
+    rust_assert (if_block != nullptr);
+    return if_block;
+  }
+
+  // TODO: this mutable getter seems really dodgy. Think up better way.
+  const std::vector<std::unique_ptr<Pattern> > &get_patterns () const
+  {
+    return match_arm_patterns;
+  }
+  std::vector<std::unique_ptr<Pattern> > &get_patterns ()
+  {
+    return match_arm_patterns;
+  }
+
+  void set_outer_attrs (std::vector<Attribute> new_attrs) override
+  {
+    outer_attrs = std::move (new_attrs);
+  }
+
+  // TODO: this mutable getter seems really dodgy. Think up better way.
+  const std::vector<Attribute> &get_outer_attrs () const { return outer_attrs; }
+  std::vector<Attribute> &get_outer_attrs () { return outer_attrs; }
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base (or rather this or any derived object) */
+  IfLetExpr *clone_expr_with_block_impl () const final override
+  {
+    return clone_if_let_expr_impl ();
+  }
+
+  // Base clone function but still concrete as concrete base class
+  virtual IfLetExpr *clone_if_let_expr_impl () const
+  {
+    return new IfLetExpr (*this);
+  }
+};
+
+// If expression with an ending "else if let" expression AST node
+class IfExprConseqIfLet : public IfExpr
+{
+  std::unique_ptr<IfLetExpr> if_let_expr;
+
+public:
+  std::string as_string () const override;
+
+  IfExprConseqIfLet (std::unique_ptr<Expr> condition,
+		     std::unique_ptr<BlockExpr> if_block,
+		     std::unique_ptr<IfLetExpr> conseq_if_let_expr,
+		     std::vector<Attribute> outer_attrs, Location locus)
+    : IfExpr (std::move (condition), std::move (if_block),
+	      std::move (outer_attrs), locus),
+      if_let_expr (std::move (conseq_if_let_expr))
+  {}
+  // outer attributes not allowed
+
+  // Copy constructor with clone
+  IfExprConseqIfLet (IfExprConseqIfLet const &other)
+    : IfExpr (other), if_let_expr (other.if_let_expr->clone_if_let_expr ())
+  {}
+
+  // Overloaded assignment operator to use clone
+  IfExprConseqIfLet &operator= (IfExprConseqIfLet const &other)
+  {
+    IfExpr::operator= (other);
+    // condition = other.condition->clone_expr();
+    // if_block = other.if_block->clone_block_expr();
+    if_let_expr = other.if_let_expr->clone_if_let_expr ();
+
+    return *this;
+  }
+
+  // move constructors
+  IfExprConseqIfLet (IfExprConseqIfLet &&other) = default;
+  IfExprConseqIfLet &operator= (IfExprConseqIfLet &&other) = default;
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // TODO: is this better? Or is a "vis_block" better?
+  std::unique_ptr<IfLetExpr> &get_conseq_if_let_expr ()
+  {
+    rust_assert (if_let_expr != nullptr);
+    return if_let_expr;
+  }
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  IfExprConseqIfLet *clone_if_expr_impl () const override
+  {
+    return new IfExprConseqIfLet (*this);
+  }
+};
+
+/* AST node representing "if let" expression with an "else" expression at the
+ * end */
+class IfLetExprConseqElse : public IfLetExpr
+{
+  std::unique_ptr<BlockExpr> else_block;
+
+public:
+  std::string as_string () const override;
+
+  IfLetExprConseqElse (
+    std::vector<std::unique_ptr<Pattern> > match_arm_patterns,
+    std::unique_ptr<Expr> value, std::unique_ptr<BlockExpr> if_block,
+    std::unique_ptr<BlockExpr> else_block, std::vector<Attribute> outer_attrs,
+    Location locus)
+    : IfLetExpr (std::move (match_arm_patterns), std::move (value),
+		 std::move (if_block), std::move (outer_attrs), locus),
+      else_block (std::move (else_block))
+  {}
+  // outer attributes not allowed
+
+  // copy constructor with clone
+  IfLetExprConseqElse (IfLetExprConseqElse const &other)
+    : IfLetExpr (other), else_block (other.else_block->clone_block_expr ())
+  {}
+
+  // overload assignment operator to clone
+  IfLetExprConseqElse &operator= (IfLetExprConseqElse const &other)
+  {
+    IfLetExpr::operator= (other);
+    // match_arm_patterns = other.match_arm_patterns;
+    // value = other.value->clone_expr();
+    // if_block = other.if_block->clone_block_expr();
+    else_block = other.else_block->clone_block_expr ();
+    // outer_attrs = other.outer_attrs;
+
+    return *this;
+  }
+
+  // move constructors
+  IfLetExprConseqElse (IfLetExprConseqElse &&other) = default;
+  IfLetExprConseqElse &operator= (IfLetExprConseqElse &&other) = default;
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // TODO: is this better? Or is a "vis_block" better?
+  std::unique_ptr<BlockExpr> &get_else_block ()
+  {
+    rust_assert (else_block != nullptr);
+    return else_block;
+  }
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  IfLetExprConseqElse *clone_if_let_expr_impl () const override
+  {
+    return new IfLetExprConseqElse (*this);
+  }
+};
+
+/* AST node representing "if let" expression with an "else if" expression at the
+ * end */
+class IfLetExprConseqIf : public IfLetExpr
+{
+  std::unique_ptr<IfExpr> if_expr;
+
+public:
+  std::string as_string () const override;
+
+  IfLetExprConseqIf (std::vector<std::unique_ptr<Pattern> > match_arm_patterns,
+		     std::unique_ptr<Expr> value,
+		     std::unique_ptr<BlockExpr> if_block,
+		     std::unique_ptr<IfExpr> if_expr,
+		     std::vector<Attribute> outer_attrs, Location locus)
+    : IfLetExpr (std::move (match_arm_patterns), std::move (value),
+		 std::move (if_block), std::move (outer_attrs), locus),
+      if_expr (std::move (if_expr))
+  {}
+  // again, outer attributes not allowed
+
+  // copy constructor with clone
+  IfLetExprConseqIf (IfLetExprConseqIf const &other)
+    : IfLetExpr (other), if_expr (other.if_expr->clone_if_expr ())
+  {}
+
+  // overload assignment operator to clone
+  IfLetExprConseqIf &operator= (IfLetExprConseqIf const &other)
+  {
+    IfLetExpr::operator= (other);
+    // match_arm_patterns = other.match_arm_patterns;
+    // value = other.value->clone_expr();
+    // if_block = other.if_block->clone_block_expr();
+    if_expr = other.if_expr->clone_if_expr ();
+
+    return *this;
+  }
+
+  // move constructors
+  IfLetExprConseqIf (IfLetExprConseqIf &&other) = default;
+  IfLetExprConseqIf &operator= (IfLetExprConseqIf &&other) = default;
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // TODO: is this better? Or is a "vis_block" better?
+  std::unique_ptr<IfExpr> &get_conseq_if_expr ()
+  {
+    rust_assert (if_expr != nullptr);
+    return if_expr;
+  }
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  IfLetExprConseqIf *clone_if_let_expr_impl () const override
+  {
+    return new IfLetExprConseqIf (*this);
+  }
+};
+
+/* AST node representing "if let" expression with an "else if let" expression at
+ * the end */
+class IfLetExprConseqIfLet : public IfLetExpr
+{
+  std::unique_ptr<IfLetExpr> if_let_expr;
+
+public:
+  std::string as_string () const override;
+
+  IfLetExprConseqIfLet (
+    std::vector<std::unique_ptr<Pattern> > match_arm_patterns,
+    std::unique_ptr<Expr> value, std::unique_ptr<BlockExpr> if_block,
+    std::unique_ptr<IfLetExpr> if_let_expr, std::vector<Attribute> outer_attrs,
+    Location locus)
+    : IfLetExpr (std::move (match_arm_patterns), std::move (value),
+		 std::move (if_block), std::move (outer_attrs), locus),
+      if_let_expr (std::move (if_let_expr))
+  {}
+  // outer attributes not allowed
+
+  // copy constructor with clone
+  IfLetExprConseqIfLet (IfLetExprConseqIfLet const &other)
+    : IfLetExpr (other), if_let_expr (other.if_let_expr->clone_if_let_expr ())
+  {}
+
+  // overload assignment operator to clone
+  IfLetExprConseqIfLet &operator= (IfLetExprConseqIfLet const &other)
+  {
+    IfLetExpr::operator= (other);
+    // match_arm_patterns = other.match_arm_patterns;
+    // value = other.value->clone_expr();
+    // if_block = other.if_block->clone_block_expr();
+    if_let_expr = other.if_let_expr->clone_if_let_expr ();
+
+    return *this;
+  }
+
+  // move constructors
+  IfLetExprConseqIfLet (IfLetExprConseqIfLet &&other) = default;
+  IfLetExprConseqIfLet &operator= (IfLetExprConseqIfLet &&other) = default;
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // TODO: is this better? Or is a "vis_block" better?
+  std::unique_ptr<IfLetExpr> &get_conseq_if_let_expr ()
+  {
+    rust_assert (if_let_expr != nullptr);
+    return if_let_expr;
+  }
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  IfLetExprConseqIfLet *clone_if_let_expr_impl () const override
+  {
+    return new IfLetExprConseqIfLet (*this);
+  }
+};
+
+// Match arm expression
+struct MatchArm
+{
+private:
+  std::vector<Attribute> outer_attrs;
+  // MatchArmPatterns patterns;
+  std::vector<std::unique_ptr<Pattern> > match_arm_patterns; // inlined
+
+  // bool has_match_arm_guard;
+  // inlined from MatchArmGuard
+  std::unique_ptr<Expr> guard_expr;
+
+  Location locus;
+
+public:
+  // Returns whether the MatchArm has a match arm guard expression
+  bool has_match_arm_guard () const { return guard_expr != nullptr; }
+
+  // Constructor for match arm with a guard expression
+  MatchArm (std::vector<std::unique_ptr<Pattern> > match_arm_patterns,
+	    Location locus, std::unique_ptr<Expr> guard_expr = nullptr,
+	    std::vector<Attribute> outer_attrs = std::vector<Attribute> ())
+    : outer_attrs (std::move (outer_attrs)),
+      match_arm_patterns (std::move (match_arm_patterns)),
+      guard_expr (std::move (guard_expr)), locus (locus)
+  {}
+
+  // Copy constructor with clone
+  MatchArm (MatchArm const &other) : outer_attrs (other.outer_attrs)
+  {
+    // guard to protect from null pointer dereference
+    if (other.guard_expr != nullptr)
+      guard_expr = other.guard_expr->clone_expr ();
+
+    match_arm_patterns.reserve (other.match_arm_patterns.size ());
+    for (const auto &e : other.match_arm_patterns)
+      match_arm_patterns.push_back (e->clone_pattern ());
+
+    locus = other.locus;
+  }
+
+  ~MatchArm () = default;
+
+  // Overload assignment operator to clone
+  MatchArm &operator= (MatchArm const &other)
+  {
+    outer_attrs = other.outer_attrs;
+
+    if (other.guard_expr != nullptr)
+      guard_expr = other.guard_expr->clone_expr ();
+    else
+      guard_expr = nullptr;
+
+    match_arm_patterns.reserve (other.match_arm_patterns.size ());
+    for (const auto &e : other.match_arm_patterns)
+      match_arm_patterns.push_back (e->clone_pattern ());
+
+    return *this;
+  }
+
+  // move constructors
+  MatchArm (MatchArm &&other) = default;
+  MatchArm &operator= (MatchArm &&other) = default;
+
+  // Returns whether match arm is in an error state.
+  bool is_error () const { return match_arm_patterns.empty (); }
+
+  // Creates a match arm in an error state.
+  static MatchArm create_error ()
+  {
+    Location locus = Location ();
+    return MatchArm (std::vector<std::unique_ptr<Pattern> > (), locus);
+  }
+
+  std::string as_string () const;
+
+  // TODO: is this better? Or is a "vis_block" better?
+  std::unique_ptr<Expr> &get_guard_expr ()
+  {
+    rust_assert (has_match_arm_guard ());
+    return guard_expr;
+  }
+
+  // TODO: this mutable getter seems really dodgy. Think up better way.
+  const std::vector<Attribute> &get_outer_attrs () const { return outer_attrs; }
+  std::vector<Attribute> &get_outer_attrs () { return outer_attrs; }
+
+  const std::vector<std::unique_ptr<Pattern> > &get_patterns () const
+  {
+    return match_arm_patterns;
+  }
+  std::vector<std::unique_ptr<Pattern> > &get_patterns ()
+  {
+    return match_arm_patterns;
+  }
+
+  Location get_locus () const { return locus; }
+};
+
+/* A "match case" - a correlated match arm and resulting expression. Not
+ * abstract. */
+struct MatchCase
+{
+private:
+  MatchArm arm;
+  std::unique_ptr<Expr> expr;
+  NodeId node_id;
+
+  /* TODO: does whether trailing comma exists need to be stored? currently
+   * assuming it is only syntactical and has no effect on meaning. */
+
+public:
+  MatchCase (MatchArm arm, std::unique_ptr<Expr> expr)
+    : arm (std::move (arm)), expr (std::move (expr)),
+      node_id (Analysis::Mappings::get ()->get_next_node_id ())
+  {}
+
+  MatchCase (const MatchCase &other)
+    : arm (other.arm), expr (other.expr->clone_expr ()), node_id (other.node_id)
+  {}
+
+  MatchCase &operator= (const MatchCase &other)
+  {
+    arm = other.arm;
+    expr = other.expr->clone_expr ();
+    node_id = other.node_id;
+
+    return *this;
+  }
+
+  MatchCase (MatchCase &&other) = default;
+  MatchCase &operator= (MatchCase &&other) = default;
+
+  ~MatchCase () = default;
+
+  std::string as_string () const;
+
+  // TODO: is this better? Or is a "vis_block" better?
+  std::unique_ptr<Expr> &get_expr ()
+  {
+    rust_assert (expr != nullptr);
+    return expr;
+  }
+
+  // TODO: is this better? Or is a "vis_block" better?
+  MatchArm &get_arm ()
+  {
+    rust_assert (!arm.is_error ());
+    return arm;
+  }
+
+  NodeId get_node_id () const { return node_id; }
+};
+
+// Match expression AST node
+class MatchExpr : public ExprWithBlock
+{
+  std::vector<Attribute> outer_attrs;
+  std::unique_ptr<Expr> branch_value;
+  std::vector<Attribute> inner_attrs;
+  std::vector<MatchCase> match_arms;
+  Location locus;
+
+public:
+  std::string as_string () const override;
+
+  // Returns whether the match expression has any match arms.
+  bool has_match_arms () const { return !match_arms.empty (); }
+
+  MatchExpr (std::unique_ptr<Expr> branch_value,
+	     std::vector<MatchCase> match_arms,
+	     std::vector<Attribute> inner_attrs,
+	     std::vector<Attribute> outer_attrs, Location locus)
+    : outer_attrs (std::move (outer_attrs)),
+      branch_value (std::move (branch_value)),
+      inner_attrs (std::move (inner_attrs)),
+      match_arms (std::move (match_arms)), locus (locus)
+  {}
+
+  // Copy constructor requires clone due to unique_ptr
+  MatchExpr (MatchExpr const &other)
+    : ExprWithBlock (other), outer_attrs (other.outer_attrs),
+      inner_attrs (other.inner_attrs), match_arms (other.match_arms),
+      locus (other.locus)
+  {
+    // guard to prevent null dereference (only required if error state)
+    if (other.branch_value != nullptr)
+      branch_value = other.branch_value->clone_expr ();
+  }
+
+  // Overloaded assignment operator to clone due to unique_ptr
+  MatchExpr &operator= (MatchExpr const &other)
+  {
+    ExprWithBlock::operator= (other);
+    inner_attrs = other.inner_attrs;
+    match_arms = other.match_arms;
+    outer_attrs = other.outer_attrs;
+    locus = other.locus;
+
+    // guard to prevent null dereference (only required if error state)
+    if (other.branch_value != nullptr)
+      branch_value = other.branch_value->clone_expr ();
+    else
+      branch_value = nullptr;
+
+    return *this;
+  }
+
+  // move constructors
+  MatchExpr (MatchExpr &&other) = default;
+  MatchExpr &operator= (MatchExpr &&other) = default;
+
+  Location get_locus () const override final { return locus; }
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // Invalid if branch value is null, so base stripping on that.
+  void mark_for_strip () override { branch_value = nullptr; }
+  bool is_marked_for_strip () const override { return branch_value == nullptr; }
+
+  // TODO: this mutable getter seems really dodgy. Think up better way.
+  const std::vector<Attribute> &get_inner_attrs () const { return inner_attrs; }
+  std::vector<Attribute> &get_inner_attrs () { return inner_attrs; }
+
+  const std::vector<Attribute> &get_outer_attrs () const { return outer_attrs; }
+  std::vector<Attribute> &get_outer_attrs () { return outer_attrs; }
+
+  void set_outer_attrs (std::vector<Attribute> new_attrs) override
+  {
+    outer_attrs = std::move (new_attrs);
+  }
+
+  // TODO: is this better? Or is a "vis_block" better?
+  std::unique_ptr<Expr> &get_scrutinee_expr ()
+  {
+    rust_assert (branch_value != nullptr);
+    return branch_value;
+  }
+
+  const std::vector<MatchCase> &get_match_cases () const { return match_arms; }
+  std::vector<MatchCase> &get_match_cases () { return match_arms; }
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  MatchExpr *clone_expr_with_block_impl () const override
+  {
+    return new MatchExpr (*this);
+  }
+};
+
+// Await expression AST node (pseudo-member variable access)
+class AwaitExpr : public ExprWithoutBlock
+{
+  std::vector<Attribute> outer_attrs;
+  std::unique_ptr<Expr> awaited_expr;
+  Location locus;
+
+public:
+  // TODO: ensure outer attributes are actually allowed
+  AwaitExpr (std::unique_ptr<Expr> awaited_expr,
+	     std::vector<Attribute> outer_attrs, Location locus)
+    : outer_attrs (std::move (outer_attrs)),
+      awaited_expr (std::move (awaited_expr)), locus (locus)
+  {}
+
+  // copy constructor with clone
+  AwaitExpr (AwaitExpr const &other)
+    : ExprWithoutBlock (other), outer_attrs (other.outer_attrs),
+      locus (other.locus)
+  {
+    // guard to prevent null dereference (only required if error state)
+    if (other.awaited_expr != nullptr)
+      awaited_expr = other.awaited_expr->clone_expr ();
+  }
+
+  // overloaded assignment operator with clone
+  AwaitExpr &operator= (AwaitExpr const &other)
+  {
+    ExprWithoutBlock::operator= (other);
+    outer_attrs = other.outer_attrs;
+    locus = other.locus;
+
+    // guard to prevent null dereference (only required if error state)
+    if (other.awaited_expr != nullptr)
+      awaited_expr = other.awaited_expr->clone_expr ();
+    else
+      awaited_expr = nullptr;
+
+    return *this;
+  }
+
+  // move constructors
+  AwaitExpr (AwaitExpr &&other) = default;
+  AwaitExpr &operator= (AwaitExpr &&other) = default;
+
+  std::string as_string () const override;
+
+  Location get_locus () const override final { return locus; }
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // Invalid if awaited expr is null, so base stripping on that.
+  void mark_for_strip () override { awaited_expr = nullptr; }
+  bool is_marked_for_strip () const override { return awaited_expr == nullptr; }
+
+  // TODO: is this better? Or is a "vis_block" better?
+  std::unique_ptr<Expr> &get_awaited_expr ()
+  {
+    rust_assert (awaited_expr != nullptr);
+    return awaited_expr;
+  }
+
+  const std::vector<Attribute> &get_outer_attrs () const { return outer_attrs; }
+  std::vector<Attribute> &get_outer_attrs () { return outer_attrs; }
+
+  void set_outer_attrs (std::vector<Attribute> new_attrs) override
+  {
+    outer_attrs = std::move (new_attrs);
+  }
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  AwaitExpr *clone_expr_without_block_impl () const override
+  {
+    return new AwaitExpr (*this);
+  }
+};
+
+// Async block expression AST node (block expr that evaluates to a future)
+class AsyncBlockExpr : public ExprWithBlock
+{
+  // TODO: should this extend BlockExpr rather than be a composite of it?
+  std::vector<Attribute> outer_attrs;
+  bool has_move;
+  std::unique_ptr<BlockExpr> block_expr;
+  Location locus;
+
+public:
+  AsyncBlockExpr (std::unique_ptr<BlockExpr> block_expr, bool has_move,
+		  std::vector<Attribute> outer_attrs, Location locus)
+    : outer_attrs (std::move (outer_attrs)), has_move (has_move),
+      block_expr (std::move (block_expr)), locus (locus)
+  {}
+
+  // copy constructor with clone
+  AsyncBlockExpr (AsyncBlockExpr const &other)
+    : ExprWithBlock (other), outer_attrs (other.outer_attrs),
+      has_move (other.has_move), locus (other.locus)
+  {
+    // guard to prevent null dereference (only required if error state)
+    if (other.block_expr != nullptr)
+      block_expr = other.block_expr->clone_block_expr ();
+  }
+
+  // overloaded assignment operator to clone
+  AsyncBlockExpr &operator= (AsyncBlockExpr const &other)
+  {
+    ExprWithBlock::operator= (other);
+    outer_attrs = other.outer_attrs;
+    has_move = other.has_move;
+    locus = other.locus;
+
+    // guard to prevent null dereference (only required if error state)
+    if (other.block_expr != nullptr)
+      block_expr = other.block_expr->clone_block_expr ();
+    else
+      block_expr = nullptr;
+
+    return *this;
+  }
+
+  // move constructors
+  AsyncBlockExpr (AsyncBlockExpr &&other) = default;
+  AsyncBlockExpr &operator= (AsyncBlockExpr &&other) = default;
+
+  std::string as_string () const override;
+
+  Location get_locus () const override final { return locus; }
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // Invalid if block is null, so base stripping on that.
+  void mark_for_strip () override { block_expr = nullptr; }
+  bool is_marked_for_strip () const override { return block_expr == nullptr; }
+
+  // TODO: is this better? Or is a "vis_block" better?
+  std::unique_ptr<BlockExpr> &get_block_expr ()
+  {
+    rust_assert (block_expr != nullptr);
+    return block_expr;
+  }
+
+  const std::vector<Attribute> &get_outer_attrs () const { return outer_attrs; }
+  std::vector<Attribute> &get_outer_attrs () { return outer_attrs; }
+
+  void set_outer_attrs (std::vector<Attribute> new_attrs) override
+  {
+    outer_attrs = std::move (new_attrs);
+  }
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  AsyncBlockExpr *clone_expr_with_block_impl () const override
+  {
+    return new AsyncBlockExpr (*this);
+  }
+};
+} // namespace AST
+} // namespace Rust
+
+#endif
diff --git a/gcc/rust/ast/rust-macro.h b/gcc/rust/ast/rust-macro.h
new file mode 100644
index 0000000..1470375
--- /dev/null
+++ b/gcc/rust/ast/rust-macro.h
@@ -0,0 +1,958 @@
+// Copyright (C) 2020-2022 Free Software Foundation, Inc.
+
+// This file is part of GCC.
+
+// GCC is free software; you can redistribute it and/or modify it under
+// the terms of the GNU General Public License as published by the Free
+// Software Foundation; either version 3, or (at your option) any later
+// version.
+
+// GCC is distributed in the hope that it will be useful, but WITHOUT ANY
+// WARRANTY; without even the implied warranty of MERCHANTABILITY or
+// FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+// for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with GCC; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+#ifndef RUST_AST_MACRO_H
+#define RUST_AST_MACRO_H
+
+#include "rust-system.h"
+#include "rust-ast.h"
+#include "rust-location.h"
+
+namespace Rust {
+namespace AST {
+
+// Decls as definitions moved to rust-ast.h
+class MacroItem;
+
+class MacroFragSpec
+{
+public:
+  enum Kind
+  {
+    BLOCK,
+    EXPR,
+    IDENT,
+    ITEM,
+    LIFETIME,
+    LITERAL,
+    META,
+    PAT,
+    PATH,
+    STMT,
+    TT,
+    TY,
+    VIS,
+    INVALID // not really a specifier, but used to mark invalid one passed in
+  };
+
+  MacroFragSpec (Kind kind) : kind (kind) {}
+
+  static MacroFragSpec get_frag_spec_from_str (const std::string &str)
+  {
+    if (str == "block")
+      return MacroFragSpec (BLOCK);
+    else if (str == "expr")
+      return MacroFragSpec (EXPR);
+    else if (str == "ident")
+      return MacroFragSpec (IDENT);
+    else if (str == "item")
+      return MacroFragSpec (ITEM);
+    else if (str == "lifetime")
+      return MacroFragSpec (LIFETIME);
+    else if (str == "literal")
+      return MacroFragSpec (LITERAL);
+    else if (str == "meta")
+      return MacroFragSpec (META);
+    else if (str == "pat" || str == "pat_param")
+      return MacroFragSpec (PAT);
+    else if (str == "path")
+      return MacroFragSpec (PATH);
+    else if (str == "stmt")
+      return MacroFragSpec (STMT);
+    else if (str == "tt")
+      return MacroFragSpec (TT);
+    else if (str == "ty")
+      return MacroFragSpec (TY);
+    else if (str == "vis")
+      return MacroFragSpec (VIS);
+    else
+      {
+	// error_at("invalid string '%s' used as fragment specifier",
+	// str->c_str()));
+	return MacroFragSpec (INVALID);
+      }
+  }
+
+  Kind get_kind () const { return kind; }
+  bool is_error () const { return kind == Kind::INVALID; }
+
+  // Converts a frag spec enum item to a string form.
+  std::string as_string () const
+  {
+    switch (kind)
+      {
+      case BLOCK:
+	return "block";
+      case EXPR:
+	return "expr";
+      case IDENT:
+	return "ident";
+      case ITEM:
+	return "item";
+      case LIFETIME:
+	return "lifetime";
+      case LITERAL:
+	return "literal";
+      case META:
+	return "meta";
+      case PAT:
+	return "pat";
+      case PATH:
+	return "path";
+      case STMT:
+	return "stmt";
+      case TT:
+	return "tt";
+      case TY:
+	return "ty";
+      case VIS:
+	return "vis";
+      case INVALID:
+	return "INVALID_FRAG_SPEC";
+      default:
+	return "ERROR_MARK_STRING - unknown frag spec";
+      }
+  }
+
+  bool has_follow_set_restrictions () const
+  {
+    switch (kind)
+      {
+      case EXPR:
+      case STMT:
+      case PAT:
+      case PATH:
+      case TY:
+      case VIS:
+	return true;
+      default:
+	return false;
+      }
+  }
+
+  bool has_follow_set_fragment_restrictions () const
+  {
+    switch (kind)
+      {
+      case PAT:
+      case TY:
+      case VIS:
+	return true;
+      default:
+	return false;
+      }
+  }
+
+private:
+  Kind kind;
+};
+
+// A macro match that has an identifier and fragment spec
+class MacroMatchFragment : public MacroMatch
+{
+  Identifier ident;
+  MacroFragSpec frag_spec;
+  Location locus;
+
+public:
+  MacroMatchFragment (Identifier ident, MacroFragSpec frag_spec, Location locus)
+    : ident (std::move (ident)), frag_spec (frag_spec), locus (locus)
+  {}
+
+  // Returns whether macro match fragment is in an error state.
+  bool is_error () const
+  {
+    return frag_spec.get_kind () == MacroFragSpec::INVALID;
+  }
+
+  // Creates an error state macro match fragment.
+  static MacroMatchFragment create_error (Location locus)
+  {
+    return MacroMatchFragment (std::string (""),
+			       MacroFragSpec (MacroFragSpec::Kind::INVALID),
+			       locus);
+  }
+
+  std::string as_string () const override;
+  Location get_match_locus () const override { return locus; };
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  MacroMatchType get_macro_match_type () const override
+  {
+    return MacroMatchType::Fragment;
+  }
+
+  Identifier get_ident () const { return ident; }
+  const MacroFragSpec &get_frag_spec () const { return frag_spec; }
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  MacroMatchFragment *clone_macro_match_impl () const override
+  {
+    return new MacroMatchFragment (*this);
+  }
+};
+
+// A repetition macro match
+class MacroMatchRepetition : public MacroMatch
+{
+public:
+  enum MacroRepOp
+  {
+    NONE,
+    ANY,
+    ONE_OR_MORE,
+    ZERO_OR_ONE,
+  };
+
+private:
+  std::vector<std::unique_ptr<MacroMatch> > matches;
+  MacroRepOp op;
+
+  // bool has_sep;
+  typedef Token MacroRepSep;
+  // any token except delimiters and repetition operators
+  std::unique_ptr<MacroRepSep> sep;
+  Location locus;
+
+public:
+  // Returns whether macro match repetition has separator token.
+  bool has_sep () const { return sep != nullptr; }
+
+  MacroMatchRepetition (std::vector<std::unique_ptr<MacroMatch> > matches,
+			MacroRepOp op, std::unique_ptr<MacroRepSep> sep,
+			Location locus)
+    : matches (std::move (matches)), op (op), sep (std::move (sep)),
+      locus (locus)
+  {}
+
+  // Copy constructor with clone
+  MacroMatchRepetition (MacroMatchRepetition const &other)
+    : op (other.op), locus (other.locus)
+  {
+    // guard to protect from null pointer dereference
+    if (other.sep != nullptr)
+      sep = other.sep->clone_token ();
+
+    matches.reserve (other.matches.size ());
+    for (const auto &e : other.matches)
+      matches.push_back (e->clone_macro_match ());
+  }
+
+  // Overloaded assignment operator to clone
+  MacroMatchRepetition &operator= (MacroMatchRepetition const &other)
+  {
+    op = other.op;
+    locus = other.locus;
+
+    // guard to protect from null pointer dereference
+    if (other.sep != nullptr)
+      sep = other.sep->clone_token ();
+    else
+      sep = nullptr;
+
+    matches.reserve (other.matches.size ());
+    for (const auto &e : other.matches)
+      matches.push_back (e->clone_macro_match ());
+
+    return *this;
+  }
+
+  // move constructors
+  MacroMatchRepetition (MacroMatchRepetition &&other) = default;
+  MacroMatchRepetition &operator= (MacroMatchRepetition &&other) = default;
+
+  std::string as_string () const override;
+  Location get_match_locus () const override { return locus; };
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  MacroMatchType get_macro_match_type () const override
+  {
+    return MacroMatchType::Repetition;
+  }
+
+  MacroRepOp get_op () const { return op; }
+  const std::unique_ptr<MacroRepSep> &get_sep () const { return sep; }
+  std::vector<std::unique_ptr<MacroMatch> > &get_matches () { return matches; }
+  const std::vector<std::unique_ptr<MacroMatch> > &get_matches () const
+  {
+    return matches;
+  }
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  MacroMatchRepetition *clone_macro_match_impl () const override
+  {
+    return new MacroMatchRepetition (*this);
+  }
+};
+
+// can't inline due to polymorphism
+class MacroMatcher : public MacroMatch
+{
+  DelimType delim_type;
+  std::vector<std::unique_ptr<MacroMatch> > matches;
+  Location locus;
+
+  // TODO: think of way to mark invalid that doesn't take up more space
+  bool is_invalid;
+
+public:
+  MacroMatcher (DelimType delim_type,
+		std::vector<std::unique_ptr<MacroMatch> > matches,
+		Location locus)
+    : delim_type (delim_type), matches (std::move (matches)), locus (locus),
+      is_invalid (false)
+  {}
+
+  // copy constructor with vector clone
+  MacroMatcher (MacroMatcher const &other)
+    : delim_type (other.delim_type), locus (other.locus)
+  {
+    matches.reserve (other.matches.size ());
+    for (const auto &e : other.matches)
+      matches.push_back (e->clone_macro_match ());
+  }
+
+  // overloaded assignment operator with vector clone
+  MacroMatcher &operator= (MacroMatcher const &other)
+  {
+    delim_type = other.delim_type;
+    locus = other.locus;
+
+    matches.reserve (other.matches.size ());
+    for (const auto &e : other.matches)
+      matches.push_back (e->clone_macro_match ());
+
+    return *this;
+  }
+
+  // move constructors
+  MacroMatcher (MacroMatcher &&other) = default;
+  MacroMatcher &operator= (MacroMatcher &&other) = default;
+
+  // Creates an error state macro matcher.
+  static MacroMatcher create_error (Location locus)
+  {
+    return MacroMatcher (true, locus);
+  }
+
+  // Returns whether MacroMatcher is in an error state.
+  bool is_error () const { return is_invalid; }
+  Location get_match_locus () const override { return locus; }
+
+  std::string as_string () const override;
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  MacroMatchType get_macro_match_type () const override
+  {
+    return MacroMatchType::Matcher;
+  }
+
+  DelimType get_delim_type () const { return delim_type; }
+  std::vector<std::unique_ptr<MacroMatch> > &get_matches () { return matches; }
+  const std::vector<std::unique_ptr<MacroMatch> > &get_matches () const
+  {
+    return matches;
+  }
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  MacroMatcher *clone_macro_match_impl () const override
+  {
+    return new MacroMatcher (*this);
+  }
+
+  // constructor only used to create error matcher
+  MacroMatcher (bool is_invalid, Location locus)
+    : delim_type (PARENS), locus (locus), is_invalid (is_invalid)
+  {}
+};
+
+// TODO: inline?
+struct MacroTranscriber
+{
+private:
+  DelimTokenTree token_tree;
+  Location locus;
+
+public:
+  MacroTranscriber (DelimTokenTree token_tree, Location locus)
+    : token_tree (std::move (token_tree)), locus (locus)
+  {}
+
+  std::string as_string () const { return token_tree.as_string (); }
+
+  Location get_locus () const { return locus; }
+
+  DelimTokenTree &get_token_tree () { return token_tree; }
+};
+
+// A macro rule? Matcher and transcriber pair?
+struct MacroRule
+{
+private:
+  MacroMatcher matcher;
+  MacroTranscriber transcriber;
+  Location locus;
+
+public:
+  MacroRule (MacroMatcher matcher, MacroTranscriber transcriber, Location locus)
+    : matcher (std::move (matcher)), transcriber (std::move (transcriber)),
+      locus (locus)
+  {}
+
+  // Returns whether macro rule is in error state.
+  bool is_error () const { return matcher.is_error (); }
+
+  // Creates an error state macro rule.
+  static MacroRule create_error (Location locus)
+  {
+    return MacroRule (MacroMatcher::create_error (locus),
+		      MacroTranscriber (DelimTokenTree::create_empty (),
+					Location ()),
+		      locus);
+  }
+
+  Location get_locus () const { return locus; }
+
+  std::string as_string () const;
+
+  MacroMatcher &get_matcher () { return matcher; }
+  MacroTranscriber &get_transcriber () { return transcriber; }
+};
+
+// A macro rules definition item AST node
+class MacroRulesDefinition : public MacroItem
+{
+  std::vector<Attribute> outer_attrs;
+  Identifier rule_name;
+  // MacroRulesDef rules_def;
+  // only curly without required semicolon at end
+  DelimType delim_type;
+  // MacroRules rules;
+  std::vector<MacroRule> rules; // inlined form
+  Location locus;
+
+  std::function<ASTFragment (Location, MacroInvocData &)>
+    associated_transcriber;
+  // Since we can't compare std::functions, we need to use an extra boolean
+  bool is_builtin_rule;
+
+  /**
+   * Default function to use as an associated transcriber. This function should
+   * never be called, hence the gcc_unreachable().
+   * If this function is used, then the macro is not builtin and the compiler
+   * should make use of the actual rules. If the macro is builtin, then another
+   * associated transcriber should be used
+   */
+  static ASTFragment dummy_builtin (Location, MacroInvocData &)
+  {
+    gcc_unreachable ();
+    return ASTFragment::create_error ();
+  }
+
+  /* NOTE: in rustc, macro definitions are considered (and parsed as) a type
+   * of macro, whereas here they are considered part of the language itself.
+   * I am not aware of the implications of this decision. The rustc spec does
+   * mention that using the same parser for macro definitions and invocations
+   * is "extremely self-referential and non-intuitive". */
+
+public:
+  std::string as_string () const override;
+
+  MacroRulesDefinition (Identifier rule_name, DelimType delim_type,
+			std::vector<MacroRule> rules,
+			std::vector<Attribute> outer_attrs, Location locus)
+    : outer_attrs (std::move (outer_attrs)), rule_name (std::move (rule_name)),
+      delim_type (delim_type), rules (std::move (rules)), locus (locus),
+      associated_transcriber (dummy_builtin), is_builtin_rule (false)
+  {}
+
+  MacroRulesDefinition (Identifier builtin_name, DelimType delim_type,
+			std::function<ASTFragment (Location, MacroInvocData &)>
+			  associated_transcriber)
+    : outer_attrs (std::vector<Attribute> ()), rule_name (builtin_name),
+      delim_type (delim_type), rules (std::vector<MacroRule> ()),
+      locus (Location ()), associated_transcriber (associated_transcriber),
+      is_builtin_rule (true)
+  {}
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // Invalid if rule name is empty, so base stripping on that.
+  void mark_for_strip () override { rule_name = ""; }
+  bool is_marked_for_strip () const override { return rule_name.empty (); }
+
+  // TODO: this mutable getter seems really dodgy. Think up better way.
+  std::vector<Attribute> &get_outer_attrs () { return outer_attrs; }
+  const std::vector<Attribute> &get_outer_attrs () const { return outer_attrs; }
+
+  std::vector<MacroRule> &get_macro_rules () { return rules; }
+  const std::vector<MacroRule> &get_macro_rules () const { return rules; }
+
+  Location get_locus () const override final { return locus; }
+
+  Identifier get_rule_name () const { return rule_name; }
+
+  std::vector<MacroRule> &get_rules () { return rules; }
+  const std::vector<MacroRule> &get_rules () const { return rules; }
+
+  bool is_builtin () const { return is_builtin_rule; }
+  const std::function<ASTFragment (Location, MacroInvocData &)> &
+  get_builtin_transcriber () const
+  {
+    rust_assert (is_builtin ());
+    return associated_transcriber;
+  }
+  void set_builtin_transcriber (
+    std::function<ASTFragment (Location, MacroInvocData &)> transcriber)
+  {
+    associated_transcriber = transcriber;
+    is_builtin_rule = true;
+  }
+
+  Kind get_ast_kind () const override { return Kind::MACRO_RULES_DEFINITION; }
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  MacroRulesDefinition *clone_item_impl () const override
+  {
+    return new MacroRulesDefinition (*this);
+  }
+};
+
+/* AST node of a macro invocation, which is replaced by the macro result at
+ * compile time */
+class MacroInvocation : public TypeNoBounds,
+			public Pattern,
+			public MacroItem,
+			public TraitItem,
+			public TraitImplItem,
+			public InherentImplItem,
+			public ExternalItem,
+			public ExprWithoutBlock
+{
+  std::vector<Attribute> outer_attrs;
+  MacroInvocData invoc_data;
+  Location locus;
+
+  // Important for when we actually expand the macro
+  bool is_semi_coloned;
+
+  NodeId node_id;
+
+public:
+  std::string as_string () const override;
+
+  MacroInvocation (MacroInvocData invoc_data,
+		   std::vector<Attribute> outer_attrs, Location locus,
+		   bool is_semi_coloned = false)
+    : outer_attrs (std::move (outer_attrs)),
+      invoc_data (std::move (invoc_data)), locus (locus),
+      is_semi_coloned (is_semi_coloned),
+      node_id (Analysis::Mappings::get ()->get_next_node_id ())
+  {}
+
+  Location get_locus () const override final { return locus; }
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // Invalid if path is empty, so base stripping on that.
+  void mark_for_strip () override { invoc_data.mark_for_strip (); }
+  bool is_marked_for_strip () const override
+  {
+    return invoc_data.is_marked_for_strip ();
+  }
+
+  const std::vector<Attribute> &get_outer_attrs () const { return outer_attrs; }
+  std::vector<Attribute> &get_outer_attrs () { return outer_attrs; }
+
+  void set_outer_attrs (std::vector<Attribute> new_attrs) override
+  {
+    outer_attrs = std::move (new_attrs);
+  }
+
+  NodeId get_pattern_node_id () const override final
+  {
+    return ExprWithoutBlock::get_node_id ();
+  }
+
+  Kind get_ast_kind () const override { return Kind::MACRO_INVOCATION; }
+
+  NodeId get_macro_node_id () const { return node_id; }
+
+  MacroInvocData &get_invoc_data () { return invoc_data; }
+
+  bool has_semicolon () const { return is_semi_coloned; }
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  MacroInvocation *clone_pattern_impl () const final override
+  {
+    return clone_macro_invocation_impl ();
+  }
+
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  MacroInvocation *clone_expr_without_block_impl () const final override
+  {
+    return clone_macro_invocation_impl ();
+  }
+
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  MacroInvocation *clone_type_no_bounds_impl () const final override
+  {
+    return clone_macro_invocation_impl ();
+  }
+
+  MacroInvocation *clone_external_item_impl () const final override
+  {
+    return clone_macro_invocation_impl ();
+  }
+
+  /*virtual*/ MacroInvocation *clone_macro_invocation_impl () const
+  {
+    return new MacroInvocation (*this);
+  }
+
+  Item *clone_item_impl () const override
+  {
+    return clone_macro_invocation_impl ();
+  }
+
+  bool is_item () const override { return !has_semicolon (); }
+
+  TraitItem *clone_trait_item_impl () const override
+  {
+    return clone_macro_invocation_impl ();
+  };
+
+  TraitImplItem *clone_trait_impl_item_impl () const override
+  {
+    return clone_macro_invocation_impl ();
+  };
+
+  InherentImplItem *clone_inherent_impl_item_impl () const override
+  {
+    return clone_macro_invocation_impl ();
+  }
+
+  ExprWithoutBlock *to_stmt () const override
+
+  {
+    auto new_impl = clone_macro_invocation_impl ();
+    new_impl->is_semi_coloned = true;
+
+    return new_impl;
+  }
+};
+
+// more generic meta item path-only form
+class MetaItemPath : public MetaItem
+{
+  SimplePath path;
+
+public:
+  MetaItemPath (SimplePath path) : path (std::move (path)) {}
+
+  std::string as_string () const override { return path.as_string (); }
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // HACK: used to simplify parsing - returns non-empty only in this case
+  SimplePath to_path_item () const override
+  {
+    // this should copy construct - TODO ensure it does
+    return path;
+  }
+
+  bool check_cfg_predicate (const Session &session) const override;
+
+  Attribute to_attribute () const override;
+
+protected:
+  // Use covariance to implement clone function as returning this type
+  MetaItemPath *clone_meta_item_inner_impl () const override
+  {
+    return new MetaItemPath (*this);
+  }
+};
+
+// more generic meta item sequence form
+class MetaItemSeq : public MetaItem
+{
+  SimplePath path;
+  std::vector<std::unique_ptr<MetaItemInner> > seq;
+
+public:
+  MetaItemSeq (SimplePath path,
+	       std::vector<std::unique_ptr<MetaItemInner> > seq)
+    : path (std::move (path)), seq (std::move (seq))
+  {}
+
+  // copy constructor with vector clone
+  MetaItemSeq (const MetaItemSeq &other) : path (other.path)
+  {
+    seq.reserve (other.seq.size ());
+    for (const auto &e : other.seq)
+      seq.push_back (e->clone_meta_item_inner ());
+  }
+
+  // overloaded assignment operator with vector clone
+  MetaItemSeq &operator= (const MetaItemSeq &other)
+  {
+    MetaItem::operator= (other);
+    path = other.path;
+
+    seq.reserve (other.seq.size ());
+    for (const auto &e : other.seq)
+      seq.push_back (e->clone_meta_item_inner ());
+
+    return *this;
+  }
+
+  // default move constructors
+  MetaItemSeq (MetaItemSeq &&other) = default;
+  MetaItemSeq &operator= (MetaItemSeq &&other) = default;
+
+  std::string as_string () const override;
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  bool check_cfg_predicate (const Session &session) const override;
+
+  Attribute to_attribute () const override;
+
+protected:
+  // Use covariance to implement clone function as returning this type
+  MetaItemSeq *clone_meta_item_inner_impl () const override
+  {
+    return new MetaItemSeq (*this);
+  }
+};
+
+// Preferred specialisation for single-identifier meta items.
+class MetaWord : public MetaItem
+{
+  Identifier ident;
+  Location ident_locus;
+
+public:
+  MetaWord (Identifier ident, Location ident_locus)
+    : ident (std::move (ident)), ident_locus (ident_locus)
+  {}
+
+  std::string as_string () const override { return ident; }
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  bool check_cfg_predicate (const Session &session) const override;
+
+  Attribute to_attribute () const override;
+
+protected:
+  // Use covariance to implement clone function as returning this type
+  MetaWord *clone_meta_item_inner_impl () const override
+  {
+    return new MetaWord (*this);
+  }
+};
+
+// Preferred specialisation for "identifier '=' string literal" meta items.
+class MetaNameValueStr : public MetaItem
+{
+  Identifier ident;
+  Location ident_locus;
+
+  // NOTE: str stored without quotes
+  std::string str;
+  Location str_locus;
+
+public:
+  MetaNameValueStr (Identifier ident, Location ident_locus, std::string str,
+		    Location str_locus)
+    : ident (std::move (ident)), ident_locus (ident_locus),
+      str (std::move (str)), str_locus (str_locus)
+  {}
+
+  std::string as_string () const override
+  {
+    return ident + " = \"" + str + "\"";
+  }
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // HACK: used to simplify parsing - creates a copy of this
+  std::unique_ptr<MetaNameValueStr> to_meta_name_value_str () const override
+  {
+    return std::unique_ptr<MetaNameValueStr> (clone_meta_item_inner_impl ());
+  }
+
+  bool check_cfg_predicate (const Session &session) const override;
+
+  Attribute to_attribute () const override;
+
+  inline std::pair<Identifier, std::string> get_name_value_pair () const
+  {
+    return std::pair<Identifier, std::string> (ident, str);
+  }
+
+  bool is_key_value_pair () const override { return true; }
+
+protected:
+  // Use covariance to implement clone function as returning this type
+  MetaNameValueStr *clone_meta_item_inner_impl () const override
+  {
+    return new MetaNameValueStr (*this);
+  }
+};
+
+// doubles up as MetaListIdents - determine via iterating through each path?
+// Preferred specialisation for "identifier '(' SimplePath, SimplePath, ... ')'"
+class MetaListPaths : public MetaItem
+{
+  Identifier ident;
+  Location ident_locus;
+  std::vector<SimplePath> paths;
+
+public:
+  MetaListPaths (Identifier ident, Location ident_locus,
+		 std::vector<SimplePath> paths)
+    : ident (std::move (ident)), ident_locus (ident_locus),
+      paths (std::move (paths))
+  {}
+
+  std::string as_string () const override;
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  bool check_cfg_predicate (const Session &session) const override;
+
+  Attribute to_attribute () const override;
+
+private:
+  bool check_path_exists_in_cfg (const Session &session,
+				 const SimplePath &path) const;
+
+protected:
+  // Use covariance to implement clone function as returning this type
+  MetaListPaths *clone_meta_item_inner_impl () const override
+  {
+    return new MetaListPaths (*this);
+  }
+};
+
+// Preferred specialisation for "identifier '(' MetaNameValueStr, ... ')'"
+class MetaListNameValueStr : public MetaItem
+{
+  Identifier ident;
+  Location ident_locus;
+  std::vector<MetaNameValueStr> strs;
+
+public:
+  MetaListNameValueStr (Identifier ident, Location ident_locus,
+			std::vector<MetaNameValueStr> strs)
+    : ident (std::move (ident)), ident_locus (ident_locus),
+      strs (std::move (strs))
+  {}
+
+  std::string as_string () const override;
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  bool check_cfg_predicate (const Session &session) const override;
+
+  Attribute to_attribute () const override;
+
+protected:
+  // Use covariance to implement clone function as returning this type
+  MetaListNameValueStr *clone_meta_item_inner_impl () const override
+  {
+    return new MetaListNameValueStr (*this);
+  }
+};
+
+// Object that parses macros from a token stream.
+/* TODO: would "AttributeParser" be a better name? MetaItems are only for
+ * attributes, I believe */
+struct AttributeParser
+{
+private:
+  // TODO: might as well rewrite to use lexer tokens
+  std::vector<std::unique_ptr<Token> > token_stream;
+  int stream_pos;
+
+public:
+  AttributeParser (std::vector<std::unique_ptr<Token> > token_stream,
+		   int stream_start_pos = 0)
+    : token_stream (std::move (token_stream)), stream_pos (stream_start_pos)
+  {}
+
+  ~AttributeParser () = default;
+
+  std::vector<std::unique_ptr<MetaItemInner> > parse_meta_item_seq ();
+
+private:
+  // Parses a MetaItemInner.
+  std::unique_ptr<MetaItemInner> parse_meta_item_inner ();
+  // Returns whether token can end a meta item.
+  bool is_end_meta_item_tok (TokenId id) const;
+  // Parses a simple path.
+  SimplePath parse_simple_path ();
+  // Parses a segment of a simple path (but not scope resolution operator).
+  SimplePathSegment parse_simple_path_segment ();
+  // Parses a MetaItemLitExpr.
+  std::unique_ptr<MetaItemLitExpr> parse_meta_item_lit ();
+  // Parses a literal.
+  Literal parse_literal ();
+  // Parses a meta item that begins with a simple path.
+  std::unique_ptr<MetaItem> parse_path_meta_item ();
+
+  // TODO: should this be const?
+  std::unique_ptr<Token> &peek_token (int i = 0)
+  {
+    return token_stream[stream_pos + i];
+  }
+
+  void skip_token (int i = 0) { stream_pos += 1 + i; }
+};
+} // namespace AST
+} // namespace Rust
+
+/* <https://stackoverflow.com/a/35304501> */
+namespace std {
+template <> struct hash<Rust::AST::MacroFragSpec::Kind>
+{
+  size_t operator() (const Rust::AST::MacroFragSpec::Kind &t) const noexcept
+  {
+    return size_t (t);
+  }
+};
+} // namespace std
+
+#endif
diff --git a/gcc/rust/ast/rust-path.h b/gcc/rust/ast/rust-path.h
new file mode 100644
index 0000000..cc79e27
--- /dev/null
+++ b/gcc/rust/ast/rust-path.h
@@ -0,0 +1,1297 @@
+// Copyright (C) 2020-2022 Free Software Foundation, Inc.
+
+// This file is part of GCC.
+
+// GCC is free software; you can redistribute it and/or modify it under
+// the terms of the GNU General Public License as published by the Free
+// Software Foundation; either version 3, or (at your option) any later
+// version.
+
+// GCC is distributed in the hope that it will be useful, but WITHOUT ANY
+// WARRANTY; without even the implied warranty of MERCHANTABILITY or
+// FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+// for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with GCC; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+#ifndef RUST_AST_PATH_H
+#define RUST_AST_PATH_H
+/* "Path" (identifier within namespaces, essentially) handling. Required include
+ * for virtually all AST-related functionality. */
+
+#include "rust-ast.h"
+#include "system.h"
+
+namespace Rust {
+namespace AST {
+
+// The "identifier" (not generic args) aspect of each path expression segment
+class PathIdentSegment
+{
+  std::string segment_name;
+  Location locus;
+
+  // only allow identifiers, "super", "self", "Self", "crate", or "$crate"
+public:
+  PathIdentSegment (std::string segment_name, Location locus)
+    : segment_name (std::move (segment_name)), locus (locus)
+  {}
+
+  // Creates an error PathIdentSegment.
+  static PathIdentSegment create_error ()
+  {
+    return PathIdentSegment ("", Location ());
+  }
+
+  // Returns whether PathIdentSegment is in an error state.
+  bool is_error () const { return segment_name.empty (); }
+
+  std::string as_string () const { return segment_name; }
+
+  Location get_locus () const { return locus; }
+
+  bool is_super_segment () const { return as_string ().compare ("super") == 0; }
+  bool is_crate_segment () const { return as_string ().compare ("crate") == 0; }
+  bool is_lower_self () const { return as_string ().compare ("self") == 0; }
+  bool is_big_self () const { return as_string ().compare ("Self") == 0; }
+};
+
+// A binding of an identifier to a type used in generic arguments in paths
+struct GenericArgsBinding
+{
+private:
+  Identifier identifier;
+  std::unique_ptr<Type> type;
+  Location locus;
+
+public:
+  // Returns whether binding is in an error state.
+  bool is_error () const
+  {
+    return type == nullptr;
+    // and also identifier is empty, but cheaper computation
+  }
+
+  // Creates an error state generic args binding.
+  static GenericArgsBinding create_error ()
+  {
+    return GenericArgsBinding ("", nullptr);
+  }
+
+  // Pointer type for type in constructor to enable polymorphism
+  GenericArgsBinding (Identifier ident, std::unique_ptr<Type> type_ptr,
+		      Location locus = Location ())
+    : identifier (std::move (ident)), type (std::move (type_ptr)), locus (locus)
+  {}
+
+  // Copy constructor has to deep copy the type as it is a unique pointer
+  GenericArgsBinding (GenericArgsBinding const &other)
+    : identifier (other.identifier), locus (other.locus)
+  {
+    // guard to protect from null pointer dereference
+    if (other.type != nullptr)
+      type = other.type->clone_type ();
+  }
+
+  // default destructor
+  ~GenericArgsBinding () = default;
+
+  // Overload assignment operator to deep copy the pointed-to type
+  GenericArgsBinding &operator= (GenericArgsBinding const &other)
+  {
+    identifier = other.identifier;
+    locus = other.locus;
+
+    // guard to protect from null pointer dereference
+    if (other.type != nullptr)
+      type = other.type->clone_type ();
+    else
+      type = nullptr;
+
+    return *this;
+  }
+
+  // move constructors
+  GenericArgsBinding (GenericArgsBinding &&other) = default;
+  GenericArgsBinding &operator= (GenericArgsBinding &&other) = default;
+
+  std::string as_string () const;
+
+  // TODO: is this better? Or is a "vis_pattern" better?
+  std::unique_ptr<Type> &get_type ()
+  {
+    rust_assert (type != nullptr);
+    return type;
+  }
+
+  Location get_locus () const { return locus; }
+
+  Identifier get_identifier () const { return identifier; }
+};
+
+/* Class representing a const generic application */
+class GenericArg
+{
+public:
+  /**
+   * const generic arguments cannot always be differentiated with generic type
+   * arguments during parsing, e.g:
+   * ```rust
+   * let a: Foo<N>;
+   * ```
+   *
+   * Is N a type? A constant defined elsewhere? The parser cannot know, and must
+   * not draw any conclusions. We must wait until later passes of the compiler
+   * to decide whether this refers to a constant item or a type.
+   *
+   * On the other hand, simple expressions like literals or block expressions
+   * will always be constant expressions: There is no ambiguity at all.
+   */
+  enum class Kind
+  {
+    Error,
+    Const,  // A const value
+    Type,   // A type argument (not discernable during parsing)
+    Either, // Either a type or a const value, cleared up during resolving
+  };
+
+  static GenericArg create_error ()
+  {
+    return GenericArg (nullptr, nullptr, "", Kind::Error, Location ());
+  }
+
+  static GenericArg create_const (std::unique_ptr<Expr> expression)
+  {
+    auto locus = expression->get_locus ();
+    return GenericArg (std::move (expression), nullptr, "", Kind::Const, locus);
+  }
+
+  static GenericArg create_type (std::unique_ptr<Type> type)
+  {
+    auto locus = type->get_locus ();
+    return GenericArg (nullptr, std::move (type), "", Kind::Type, locus);
+  }
+
+  static GenericArg create_ambiguous (Identifier path, Location locus)
+  {
+    return GenericArg (nullptr, nullptr, std::move (path), Kind::Either, locus);
+  }
+
+  GenericArg (const GenericArg &other)
+    : path (other.path), kind (other.kind), locus (other.locus)
+  {
+    if (other.expression)
+      expression = other.expression->clone_expr ();
+    if (other.type)
+      type = other.type->clone_type ();
+  }
+
+  GenericArg operator= (const GenericArg &other)
+  {
+    kind = other.kind;
+    path = other.path;
+    locus = other.locus;
+
+    if (other.expression)
+      expression = other.expression->clone_expr ();
+    if (other.type)
+      type = other.type->clone_type ();
+
+    return *this;
+  }
+
+  bool is_error () const { return kind == Kind::Error; }
+
+  Kind get_kind () const { return kind; }
+  const Location &get_locus () const { return locus; }
+
+  std::unique_ptr<Expr> &get_expression ()
+  {
+    rust_assert (kind == Kind::Const);
+
+    return expression;
+  }
+
+  std::unique_ptr<Type> &get_type ()
+  {
+    rust_assert (kind == Kind::Type);
+
+    return type;
+  }
+
+  const std::string &get_path () const
+  {
+    rust_assert (kind == Kind::Either);
+
+    return path;
+  }
+
+  std::string as_string () const
+  {
+    switch (get_kind ())
+      {
+      case Kind::Error:
+	gcc_unreachable ();
+      case Kind::Either:
+	return "Ambiguous: " + path;
+      case Kind::Const:
+	return "Const: { " + expression->as_string () + " }";
+      case Kind::Type:
+	return "Type: " + type->as_string ();
+      }
+
+    return "";
+  }
+
+  /**
+   * Disambiguate an ambiguous generic argument to a const generic argument,
+   * unequivocally
+   */
+  GenericArg disambiguate_to_const () const;
+
+  /**
+   * Disambiguate an ambiguous generic argument to a type argument,
+   * unequivocally
+   */
+  GenericArg disambiguate_to_type () const;
+
+private:
+  GenericArg (std::unique_ptr<Expr> expression, std::unique_ptr<Type> type,
+	      Identifier path, Kind kind, Location locus)
+    : expression (std::move (expression)), type (std::move (type)),
+      path (std::move (path)), kind (kind), locus (locus)
+  {}
+
+  /**
+   * Expression associated with a `Clear` const generic application
+   * A null pointer here is allowed in the case that the const argument is
+   * ambiguous.
+   */
+  std::unique_ptr<Expr> expression;
+
+  /**
+   * If the argument ends up being a type argument instead. A null pointer will
+   * be present here until the resolving phase.
+   */
+  std::unique_ptr<Type> type;
+
+  /**
+   * Optional path which cannot be differentiated between a constant item and
+   * a type. Only used for ambiguous const generic arguments, otherwise
+   * empty.
+   */
+  Identifier path;
+
+  /* Which kind of const generic application are we dealing with */
+  Kind kind;
+
+  Location locus;
+};
+
+/**
+ * Representation of const generic parameters
+ */
+class ConstGenericParam : public GenericParam
+{
+  /* Name of the parameter */
+  Identifier name;
+
+  /* Mandatory type of the const parameter - a null pointer is an error */
+  std::unique_ptr<AST::Type> type;
+
+  /**
+   * Default value for the const generic parameter
+   */
+  GenericArg default_value;
+
+  Attribute outer_attr;
+  Location locus;
+
+public:
+  ConstGenericParam (Identifier name, std::unique_ptr<AST::Type> type,
+		     GenericArg default_value, Attribute outer_attr,
+		     Location locus)
+    : name (name), type (std::move (type)),
+      default_value (std::move (default_value)), outer_attr (outer_attr),
+      locus (locus)
+  {}
+
+  ConstGenericParam (const ConstGenericParam &other)
+    : GenericParam (), name (other.name), type (other.type->clone_type ()),
+      default_value (other.default_value), outer_attr (other.outer_attr),
+      locus (other.locus)
+  {}
+
+  bool has_type () const { return type != nullptr; }
+  bool has_default_value () const { return !default_value.is_error (); }
+
+  const Identifier &get_name () const { return name; }
+
+  std::unique_ptr<AST::Type> &get_type ()
+  {
+    rust_assert (has_type ());
+
+    return type;
+  }
+
+  GenericArg &get_default_value ()
+  {
+    rust_assert (has_default_value ());
+
+    return default_value;
+  }
+
+  const GenericArg &get_default_value () const
+  {
+    rust_assert (has_default_value ());
+
+    return default_value;
+  }
+
+  std::string as_string () const override;
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  Location get_locus () const override final { return locus; }
+
+  Kind get_kind () const override final { return Kind::Const; }
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  ConstGenericParam *clone_generic_param_impl () const override
+  {
+    return new ConstGenericParam (*this);
+  }
+};
+
+// Generic arguments allowed in each path expression segment - inline?
+struct GenericArgs
+{
+  std::vector<Lifetime> lifetime_args;
+  std::vector<GenericArg> generic_args;
+  std::vector<GenericArgsBinding> binding_args;
+  Location locus;
+
+public:
+  // Returns true if there are any generic arguments
+  bool has_generic_args () const
+  {
+    return !(lifetime_args.empty () && generic_args.empty ()
+	     && binding_args.empty ());
+  }
+
+  GenericArgs (std::vector<Lifetime> lifetime_args,
+	       std::vector<GenericArg> generic_args,
+	       std::vector<GenericArgsBinding> binding_args,
+	       Location locus = Location ())
+    : lifetime_args (std::move (lifetime_args)),
+      generic_args (std::move (generic_args)),
+      binding_args (std::move (binding_args)), locus (locus)
+  {}
+
+  // copy constructor with vector clone
+  GenericArgs (GenericArgs const &other)
+    : lifetime_args (other.lifetime_args), generic_args (other.generic_args),
+      binding_args (other.binding_args), locus (other.locus)
+  {}
+
+  ~GenericArgs () = default;
+
+  // overloaded assignment operator to vector clone
+  GenericArgs &operator= (GenericArgs const &other)
+  {
+    lifetime_args = other.lifetime_args;
+    generic_args = other.generic_args;
+    binding_args = other.binding_args;
+    locus = other.locus;
+
+    return *this;
+  }
+
+  // move constructors
+  GenericArgs (GenericArgs &&other) = default;
+  GenericArgs &operator= (GenericArgs &&other) = default;
+
+  // Creates an empty GenericArgs (no arguments)
+  static GenericArgs create_empty () { return GenericArgs ({}, {}, {}); }
+
+  std::string as_string () const;
+
+  // TODO: is this better? Or is a "vis_pattern" better?
+  std::vector<GenericArg> &get_generic_args () { return generic_args; }
+
+  // TODO: is this better? Or is a "vis_pattern" better?
+  std::vector<GenericArgsBinding> &get_binding_args () { return binding_args; }
+
+  std::vector<Lifetime> &get_lifetime_args () { return lifetime_args; };
+
+  Location get_locus () { return locus; }
+};
+
+/* A segment of a path in expression, including an identifier aspect and maybe
+ * generic args */
+class PathExprSegment
+{ // or should this extend PathIdentSegment?
+private:
+  PathIdentSegment segment_name;
+  GenericArgs generic_args;
+  Location locus;
+  NodeId node_id;
+
+public:
+  // Returns true if there are any generic arguments
+  bool has_generic_args () const { return generic_args.has_generic_args (); }
+
+  // Constructor for segment (from IdentSegment and GenericArgs)
+  PathExprSegment (PathIdentSegment segment_name, Location locus,
+		   GenericArgs generic_args = GenericArgs::create_empty ())
+    : segment_name (std::move (segment_name)),
+      generic_args (std::move (generic_args)), locus (locus),
+      node_id (Analysis::Mappings::get ()->get_next_node_id ())
+  {}
+
+  /* Constructor for segment with generic arguments (from segment name and all
+   * args) */
+  PathExprSegment (std::string segment_name, Location locus,
+		   std::vector<Lifetime> lifetime_args = {},
+		   std::vector<GenericArg> generic_args = {},
+		   std::vector<GenericArgsBinding> binding_args = {})
+    : segment_name (PathIdentSegment (std::move (segment_name), locus)),
+      generic_args (GenericArgs (std::move (lifetime_args),
+				 std::move (generic_args),
+				 std::move (binding_args))),
+      locus (locus), node_id (Analysis::Mappings::get ()->get_next_node_id ())
+  {}
+
+  // Returns whether path expression segment is in an error state.
+  bool is_error () const { return segment_name.is_error (); }
+
+  // Creates an error-state path expression segment.
+  static PathExprSegment create_error ()
+  {
+    return PathExprSegment (PathIdentSegment::create_error (), Location ());
+  }
+
+  std::string as_string () const;
+
+  Location get_locus () const { return locus; }
+
+  // TODO: is this better? Or is a "vis_pattern" better?
+  GenericArgs &get_generic_args ()
+  {
+    rust_assert (has_generic_args ());
+    return generic_args;
+  }
+
+  PathIdentSegment &get_ident_segment () { return segment_name; }
+  const PathIdentSegment &get_ident_segment () const { return segment_name; }
+
+  NodeId get_node_id () const { return node_id; }
+
+  bool is_super_path_seg () const
+  {
+    return !has_generic_args () && get_ident_segment ().is_super_segment ();
+  }
+
+  bool is_crate_path_seg () const
+  {
+    return !has_generic_args () && get_ident_segment ().is_crate_segment ();
+  }
+  bool is_lower_self_seg () const
+  {
+    return !has_generic_args () && get_ident_segment ().is_lower_self ();
+  }
+};
+
+// AST node representing a pattern that involves a "path" - abstract base
+// class
+class PathPattern : public Pattern
+{
+  std::vector<PathExprSegment> segments;
+
+protected:
+  PathPattern (std::vector<PathExprSegment> segments)
+    : segments (std::move (segments))
+  {}
+
+  // Returns whether path has segments.
+  bool has_segments () const { return !segments.empty (); }
+
+  /* Converts path segments to their equivalent SimplePath segments if
+   * possible, and creates a SimplePath from them. */
+  SimplePath convert_to_simple_path (bool with_opening_scope_resolution) const;
+
+  // Removes all segments of the path.
+  void remove_all_segments ()
+  {
+    segments.clear ();
+    segments.shrink_to_fit ();
+  }
+
+public:
+  /* Returns whether the path is a single segment (excluding qualified path
+   * initial as segment). */
+  bool is_single_segment () const { return segments.size () == 1; }
+
+  std::string as_string () const override;
+
+  // TODO: this seems kinda dodgy
+  std::vector<PathExprSegment> &get_segments () { return segments; }
+  const std::vector<PathExprSegment> &get_segments () const { return segments; }
+};
+
+/* AST node representing a path-in-expression pattern (path that allows
+ * generic arguments) */
+class PathInExpression : public PathPattern, public PathExpr
+{
+  std::vector<Attribute> outer_attrs;
+  bool has_opening_scope_resolution;
+  Location locus;
+  NodeId _node_id;
+
+public:
+  std::string as_string () const override;
+
+  // Constructor
+  PathInExpression (std::vector<PathExprSegment> path_segments,
+		    std::vector<Attribute> outer_attrs, Location locus,
+		    bool has_opening_scope_resolution = false)
+    : PathPattern (std::move (path_segments)),
+      outer_attrs (std::move (outer_attrs)),
+      has_opening_scope_resolution (has_opening_scope_resolution),
+      locus (locus), _node_id (Analysis::Mappings::get ()->get_next_node_id ())
+  {}
+
+  // Creates an error state path in expression.
+  static PathInExpression create_error ()
+  {
+    return PathInExpression ({}, {}, Location ());
+  }
+
+  // Returns whether path in expression is in an error state.
+  bool is_error () const { return !has_segments (); }
+
+  /* Converts PathInExpression to SimplePath if possible (i.e. no generic
+   * arguments). Otherwise returns an empty SimplePath. */
+  SimplePath as_simple_path () const
+  {
+    /* delegate to parent class as can't access segments. however,
+     * QualifiedPathInExpression conversion to simple path wouldn't make
+     * sense, so the method in the parent class should be protected, not
+     * public. Have to pass in opening scope resolution as parent class has no
+     * access to it.
+     */
+    return convert_to_simple_path (has_opening_scope_resolution);
+  }
+
+  Location get_locus () const override final { return locus; }
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // Invalid if path is empty (error state), so base stripping on that.
+  void mark_for_strip () override { remove_all_segments (); }
+  bool is_marked_for_strip () const override { return is_error (); }
+
+  bool opening_scope_resolution () const
+  {
+    return has_opening_scope_resolution;
+  }
+
+  NodeId get_node_id () const override { return _node_id; }
+
+  const std::vector<Attribute> &get_outer_attrs () const { return outer_attrs; }
+  std::vector<Attribute> &get_outer_attrs () { return outer_attrs; }
+
+  void set_outer_attrs (std::vector<Attribute> new_attrs) override
+  {
+    outer_attrs = std::move (new_attrs);
+  }
+
+  NodeId get_pattern_node_id () const override final { return get_node_id (); }
+
+protected:
+  /* Use covariance to implement clone function as returning this object
+   * rather than base */
+  PathInExpression *clone_pattern_impl () const final override
+  {
+    return clone_path_in_expression_impl ();
+  }
+
+  /* Use covariance to implement clone function as returning this object
+   * rather than base */
+  PathInExpression *clone_expr_without_block_impl () const final override
+  {
+    return clone_path_in_expression_impl ();
+  }
+
+  /*virtual*/ PathInExpression *clone_path_in_expression_impl () const
+  {
+    return new PathInExpression (*this);
+  }
+};
+
+/* Base class for segments used in type paths - not abstract (represents an
+ * ident-only segment) */
+class TypePathSegment
+{
+public:
+  enum SegmentType
+  {
+    REG,
+    GENERIC,
+    FUNCTION
+  };
+
+private:
+  PathIdentSegment ident_segment;
+  Location locus;
+
+protected:
+  /* This is protected because it is only really used by derived classes, not
+   * the base. */
+  bool has_separating_scope_resolution;
+  NodeId node_id;
+
+  // Clone function implementation - not pure virtual as overrided by
+  // subclasses
+  virtual TypePathSegment *clone_type_path_segment_impl () const
+  {
+    return new TypePathSegment (*this);
+  }
+
+public:
+  virtual ~TypePathSegment () {}
+
+  virtual SegmentType get_type () const { return SegmentType::REG; }
+
+  // Unique pointer custom clone function
+  std::unique_ptr<TypePathSegment> clone_type_path_segment () const
+  {
+    return std::unique_ptr<TypePathSegment> (clone_type_path_segment_impl ());
+  }
+
+  TypePathSegment (PathIdentSegment ident_segment,
+		   bool has_separating_scope_resolution, Location locus)
+    : ident_segment (std::move (ident_segment)), locus (locus),
+      has_separating_scope_resolution (has_separating_scope_resolution),
+      node_id (Analysis::Mappings::get ()->get_next_node_id ())
+  {}
+
+  TypePathSegment (std::string segment_name,
+		   bool has_separating_scope_resolution, Location locus)
+    : ident_segment (PathIdentSegment (std::move (segment_name), locus)),
+      locus (locus),
+      has_separating_scope_resolution (has_separating_scope_resolution),
+      node_id (Analysis::Mappings::get ()->get_next_node_id ())
+  {}
+
+  virtual std::string as_string () const { return ident_segment.as_string (); }
+
+  /* Returns whether the type path segment is in an error state. May be
+   * virtual in future. */
+  bool is_error () const { return ident_segment.is_error (); }
+
+  /* Returns whether segment is identifier only (as opposed to generic args or
+   * function). Overridden in derived classes with other segments. */
+  virtual bool is_ident_only () const { return true; }
+
+  Location get_locus () const { return locus; }
+
+  // not pure virtual as class not abstract
+  virtual void accept_vis (ASTVisitor &vis);
+
+  bool get_separating_scope_resolution () const
+  {
+    return has_separating_scope_resolution;
+  }
+
+  PathIdentSegment &get_ident_segment () { return ident_segment; };
+  const PathIdentSegment &get_ident_segment () const { return ident_segment; };
+
+  NodeId get_node_id () const { return node_id; }
+
+  bool is_crate_path_seg () const
+  {
+    return get_ident_segment ().is_crate_segment ();
+  }
+  bool is_super_path_seg () const
+  {
+    return get_ident_segment ().is_super_segment ();
+  }
+  bool is_big_self_seg () const { return get_ident_segment ().is_big_self (); }
+  bool is_lower_self_seg () const
+  {
+    return get_ident_segment ().is_lower_self ();
+  }
+};
+
+// Segment used in type path with generic args
+class TypePathSegmentGeneric : public TypePathSegment
+{
+  GenericArgs generic_args;
+
+public:
+  SegmentType get_type () const override { return SegmentType::GENERIC; }
+
+  bool has_generic_args () const { return generic_args.has_generic_args (); }
+
+  bool is_ident_only () const override { return false; }
+
+  // Constructor with PathIdentSegment and GenericArgs
+  TypePathSegmentGeneric (PathIdentSegment ident_segment,
+			  bool has_separating_scope_resolution,
+			  GenericArgs generic_args, Location locus)
+    : TypePathSegment (std::move (ident_segment),
+		       has_separating_scope_resolution, locus),
+      generic_args (std::move (generic_args))
+  {}
+
+  // Constructor from segment name and all args
+  TypePathSegmentGeneric (std::string segment_name,
+			  bool has_separating_scope_resolution,
+			  std::vector<Lifetime> lifetime_args,
+			  std::vector<GenericArg> generic_args,
+			  std::vector<GenericArgsBinding> binding_args,
+			  Location locus)
+    : TypePathSegment (std::move (segment_name),
+		       has_separating_scope_resolution, locus),
+      generic_args (GenericArgs (std::move (lifetime_args),
+				 std::move (generic_args),
+				 std::move (binding_args)))
+  {}
+
+  std::string as_string () const override;
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // TODO: is this better? Or is a "vis_pattern" better?
+  GenericArgs &get_generic_args ()
+  {
+    rust_assert (has_generic_args ());
+    return generic_args;
+  }
+
+protected:
+  // Use covariance to override base class method
+  TypePathSegmentGeneric *clone_type_path_segment_impl () const override
+  {
+    return new TypePathSegmentGeneric (*this);
+  }
+};
+
+// A function as represented in a type path
+struct TypePathFunction
+{
+private:
+  // TODO: remove
+  /*bool has_inputs;
+  TypePathFnInputs inputs;*/
+  // inlined from TypePathFnInputs
+  std::vector<std::unique_ptr<Type> > inputs;
+
+  // bool has_type;
+  std::unique_ptr<Type> return_type;
+
+  // FIXME: think of better way to mark as invalid than taking up storage
+  bool is_invalid;
+
+  Location locus;
+
+protected:
+  // Constructor only used to create invalid type path functions.
+  TypePathFunction (bool is_invalid, Location locus)
+    : is_invalid (is_invalid), locus (locus)
+  {}
+
+public:
+  // Returns whether the return type of the function has been specified.
+  bool has_return_type () const { return return_type != nullptr; }
+
+  // Returns whether the function has inputs.
+  bool has_inputs () const { return !inputs.empty (); }
+
+  // Returns whether function is in an error state.
+  bool is_error () const { return is_invalid; }
+
+  // Creates an error state function.
+  static TypePathFunction create_error ()
+  {
+    return TypePathFunction (true, Location ());
+  }
+
+  // Constructor
+  TypePathFunction (std::vector<std::unique_ptr<Type> > inputs, Location locus,
+		    std::unique_ptr<Type> type = nullptr)
+    : inputs (std::move (inputs)), return_type (std::move (type)),
+      is_invalid (false), locus (locus)
+  {}
+
+  // Copy constructor with clone
+  TypePathFunction (TypePathFunction const &other)
+    : is_invalid (other.is_invalid)
+  {
+    // guard to protect from null pointer dereference
+    if (other.return_type != nullptr)
+      return_type = other.return_type->clone_type ();
+
+    inputs.reserve (other.inputs.size ());
+    for (const auto &e : other.inputs)
+      inputs.push_back (e->clone_type ());
+  }
+
+  ~TypePathFunction () = default;
+
+  // Overloaded assignment operator to clone type
+  TypePathFunction &operator= (TypePathFunction const &other)
+  {
+    is_invalid = other.is_invalid;
+
+    // guard to protect from null pointer dereference
+    if (other.return_type != nullptr)
+      return_type = other.return_type->clone_type ();
+    else
+      return_type = nullptr;
+
+    inputs.reserve (other.inputs.size ());
+    for (const auto &e : other.inputs)
+      inputs.push_back (e->clone_type ());
+
+    return *this;
+  }
+
+  // move constructors
+  TypePathFunction (TypePathFunction &&other) = default;
+  TypePathFunction &operator= (TypePathFunction &&other) = default;
+
+  std::string as_string () const;
+
+  // TODO: this mutable getter seems really dodgy. Think up better way.
+  const std::vector<std::unique_ptr<Type> > &get_params () const
+  {
+    return inputs;
+  }
+  std::vector<std::unique_ptr<Type> > &get_params () { return inputs; }
+
+  // TODO: is this better? Or is a "vis_pattern" better?
+  std::unique_ptr<Type> &get_return_type ()
+  {
+    rust_assert (has_return_type ());
+    return return_type;
+  }
+};
+
+// Segment used in type path with a function argument
+class TypePathSegmentFunction : public TypePathSegment
+{
+  TypePathFunction function_path;
+
+public:
+  SegmentType get_type () const override { return SegmentType::FUNCTION; }
+
+  // Constructor with PathIdentSegment and TypePathFn
+  TypePathSegmentFunction (PathIdentSegment ident_segment,
+			   bool has_separating_scope_resolution,
+			   TypePathFunction function_path, Location locus)
+    : TypePathSegment (std::move (ident_segment),
+		       has_separating_scope_resolution, locus),
+      function_path (std::move (function_path))
+  {}
+
+  // Constructor with segment name and TypePathFn
+  TypePathSegmentFunction (std::string segment_name,
+			   bool has_separating_scope_resolution,
+			   TypePathFunction function_path, Location locus)
+    : TypePathSegment (std::move (segment_name),
+		       has_separating_scope_resolution, locus),
+      function_path (std::move (function_path))
+  {}
+
+  std::string as_string () const override;
+
+  bool is_ident_only () const override { return false; }
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // TODO: is this better? Or is a "vis_pattern" better?
+  TypePathFunction &get_type_path_function ()
+  {
+    rust_assert (!function_path.is_error ());
+    return function_path;
+  }
+
+protected:
+  // Use covariance to override base class method
+  TypePathSegmentFunction *clone_type_path_segment_impl () const override
+  {
+    return new TypePathSegmentFunction (*this);
+  }
+};
+
+// Path used inside types
+class TypePath : public TypeNoBounds
+{
+  bool has_opening_scope_resolution;
+  std::vector<std::unique_ptr<TypePathSegment> > segments;
+  Location locus;
+
+protected:
+  /* Use covariance to implement clone function as returning this object
+   * rather than base */
+  TypePath *clone_type_no_bounds_impl () const override
+  {
+    return new TypePath (*this);
+  }
+
+public:
+  /* Returns whether the TypePath has an opening scope resolution operator
+   * (i.e. is global path or crate-relative path, not module-relative) */
+  bool has_opening_scope_resolution_op () const
+  {
+    return has_opening_scope_resolution;
+  }
+
+  // Returns whether the TypePath is in an invalid state.
+  bool is_error () const { return segments.empty (); }
+
+  // Creates an error state TypePath.
+  static TypePath create_error ()
+  {
+    return TypePath (std::vector<std::unique_ptr<TypePathSegment> > (),
+		     Location ());
+  }
+
+  // Constructor
+  TypePath (std::vector<std::unique_ptr<TypePathSegment> > segments,
+	    Location locus, bool has_opening_scope_resolution = false)
+    : TypeNoBounds (),
+      has_opening_scope_resolution (has_opening_scope_resolution),
+      segments (std::move (segments)), locus (locus)
+  {}
+
+  // Copy constructor with vector clone
+  TypePath (TypePath const &other)
+    : has_opening_scope_resolution (other.has_opening_scope_resolution),
+      locus (other.locus)
+  {
+    segments.reserve (other.segments.size ());
+    for (const auto &e : other.segments)
+      segments.push_back (e->clone_type_path_segment ());
+  }
+
+  // Overloaded assignment operator with clone
+  TypePath &operator= (TypePath const &other)
+  {
+    has_opening_scope_resolution = other.has_opening_scope_resolution;
+    locus = other.locus;
+
+    segments.reserve (other.segments.size ());
+    for (const auto &e : other.segments)
+      segments.push_back (e->clone_type_path_segment ());
+
+    return *this;
+  }
+
+  // move constructors
+  TypePath (TypePath &&other) = default;
+  TypePath &operator= (TypePath &&other) = default;
+
+  std::string as_string () const override;
+
+  /* Converts TypePath to SimplePath if possible (i.e. no generic or function
+   * arguments). Otherwise returns an empty SimplePath. */
+  SimplePath as_simple_path () const;
+
+  // Creates a trait bound with a clone of this type path as its only element.
+  TraitBound *to_trait_bound (bool in_parens) const override;
+
+  Location get_locus () const override final { return locus; }
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // TODO: this seems kinda dodgy
+  std::vector<std::unique_ptr<TypePathSegment> > &get_segments ()
+  {
+    return segments;
+  }
+  const std::vector<std::unique_ptr<TypePathSegment> > &get_segments () const
+  {
+    return segments;
+  }
+
+  size_t get_num_segments () const { return segments.size (); }
+};
+
+struct QualifiedPathType
+{
+private:
+  std::unique_ptr<Type> type_to_invoke_on;
+  TypePath trait_path;
+  Location locus;
+  NodeId node_id;
+
+public:
+  // Constructor
+  QualifiedPathType (std::unique_ptr<Type> invoke_on_type,
+		     Location locus = Location (),
+		     TypePath trait_path = TypePath::create_error ())
+    : type_to_invoke_on (std::move (invoke_on_type)),
+      trait_path (std::move (trait_path)), locus (locus),
+      node_id (Analysis::Mappings::get ()->get_next_node_id ())
+  {}
+
+  // Copy constructor uses custom deep copy for Type to preserve polymorphism
+  QualifiedPathType (QualifiedPathType const &other)
+    : trait_path (other.trait_path), locus (other.locus)
+  {
+    node_id = other.node_id;
+    // guard to prevent null dereference
+    if (other.type_to_invoke_on != nullptr)
+      type_to_invoke_on = other.type_to_invoke_on->clone_type ();
+  }
+
+  // default destructor
+  ~QualifiedPathType () = default;
+
+  // overload assignment operator to use custom clone method
+  QualifiedPathType &operator= (QualifiedPathType const &other)
+  {
+    node_id = other.node_id;
+    trait_path = other.trait_path;
+    locus = other.locus;
+
+    // guard to prevent null dereference
+    if (other.type_to_invoke_on != nullptr)
+      type_to_invoke_on = other.type_to_invoke_on->clone_type ();
+    else
+      type_to_invoke_on = nullptr;
+
+    return *this;
+  }
+
+  // move constructor
+  QualifiedPathType (QualifiedPathType &&other) = default;
+  QualifiedPathType &operator= (QualifiedPathType &&other) = default;
+
+  // Returns whether the qualified path type has a rebind as clause.
+  bool has_as_clause () const { return !trait_path.is_error (); }
+
+  // Returns whether the qualified path type is in an error state.
+  bool is_error () const { return type_to_invoke_on == nullptr; }
+
+  // Creates an error state qualified path type.
+  static QualifiedPathType create_error ()
+  {
+    return QualifiedPathType (nullptr);
+  }
+
+  std::string as_string () const;
+
+  Location get_locus () const { return locus; }
+
+  // TODO: is this better? Or is a "vis_pattern" better?
+  std::unique_ptr<Type> &get_type ()
+  {
+    rust_assert (type_to_invoke_on != nullptr);
+    return type_to_invoke_on;
+  }
+
+  // TODO: is this better? Or is a "vis_pattern" better?
+  TypePath &get_as_type_path ()
+  {
+    rust_assert (has_as_clause ());
+    return trait_path;
+  }
+
+  NodeId get_node_id () const { return node_id; }
+};
+
+/* AST node representing a qualified path-in-expression pattern (path that
+ * allows specifying trait functions) */
+class QualifiedPathInExpression : public PathPattern, public PathExpr
+{
+  std::vector<Attribute> outer_attrs;
+  QualifiedPathType path_type;
+  Location locus;
+  NodeId _node_id;
+
+public:
+  std::string as_string () const override;
+
+  QualifiedPathInExpression (QualifiedPathType qual_path_type,
+			     std::vector<PathExprSegment> path_segments,
+			     std::vector<Attribute> outer_attrs, Location locus)
+    : PathPattern (std::move (path_segments)),
+      outer_attrs (std::move (outer_attrs)),
+      path_type (std::move (qual_path_type)), locus (locus),
+      _node_id (Analysis::Mappings::get ()->get_next_node_id ())
+  {}
+
+  /* TODO: maybe make a shortcut constructor that has QualifiedPathType
+   * elements as params */
+
+  // Returns whether qualified path in expression is in an error state.
+  bool is_error () const { return path_type.is_error (); }
+
+  // Creates an error qualified path in expression.
+  static QualifiedPathInExpression create_error ()
+  {
+    return QualifiedPathInExpression (QualifiedPathType::create_error (), {},
+				      {}, Location ());
+  }
+
+  Location get_locus () const override final { return locus; }
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // Invalid if path_type is error, so base stripping on that.
+  void mark_for_strip () override
+  {
+    path_type = QualifiedPathType::create_error ();
+  }
+  bool is_marked_for_strip () const override { return is_error (); }
+
+  // TODO: is this better? Or is a "vis_pattern" better?
+  QualifiedPathType &get_qualified_path_type ()
+  {
+    rust_assert (!path_type.is_error ());
+    return path_type;
+  }
+
+  const std::vector<Attribute> &get_outer_attrs () const { return outer_attrs; }
+  std::vector<Attribute> &get_outer_attrs () { return outer_attrs; }
+
+  void set_outer_attrs (std::vector<Attribute> new_attrs) override
+  {
+    outer_attrs = std::move (new_attrs);
+  }
+
+  NodeId get_node_id () const override { return _node_id; }
+
+  NodeId get_pattern_node_id () const override final { return get_node_id (); }
+
+protected:
+  /* Use covariance to implement clone function as returning this object
+   * rather than base */
+  QualifiedPathInExpression *clone_pattern_impl () const final override
+  {
+    return clone_qual_path_in_expression_impl ();
+  }
+
+  /* Use covariance to implement clone function as returning this object
+   * rather than base */
+  QualifiedPathInExpression *
+  clone_expr_without_block_impl () const final override
+  {
+    return clone_qual_path_in_expression_impl ();
+  }
+
+  /*virtual*/ QualifiedPathInExpression *
+  clone_qual_path_in_expression_impl () const
+  {
+    return new QualifiedPathInExpression (*this);
+  }
+};
+
+/* Represents a qualified path in a type; used for disambiguating trait
+ * function calls */
+class QualifiedPathInType : public TypeNoBounds
+{
+  QualifiedPathType path_type;
+  std::unique_ptr<TypePathSegment> associated_segment;
+  std::vector<std::unique_ptr<TypePathSegment> > segments;
+  Location locus;
+
+protected:
+  /* Use covariance to implement clone function as returning this object
+   * rather than base */
+  QualifiedPathInType *clone_type_no_bounds_impl () const override
+  {
+    return new QualifiedPathInType (*this);
+  }
+
+public:
+  QualifiedPathInType (
+    QualifiedPathType qual_path_type,
+    std::unique_ptr<TypePathSegment> associated_segment,
+    std::vector<std::unique_ptr<TypePathSegment> > path_segments,
+    Location locus)
+    : path_type (std::move (qual_path_type)),
+      associated_segment (std::move (associated_segment)),
+      segments (std::move (path_segments)), locus (locus)
+  {}
+
+  /* TODO: maybe make a shortcut constructor that has QualifiedPathType
+   * elements as params */
+
+  // Copy constructor with vector clone
+  QualifiedPathInType (QualifiedPathInType const &other)
+    : path_type (other.path_type), locus (other.locus)
+  {
+    segments.reserve (other.segments.size ());
+    for (const auto &e : other.segments)
+      segments.push_back (e->clone_type_path_segment ());
+  }
+
+  // Overloaded assignment operator with vector clone
+  QualifiedPathInType &operator= (QualifiedPathInType const &other)
+  {
+    path_type = other.path_type;
+    locus = other.locus;
+
+    segments.reserve (other.segments.size ());
+    for (const auto &e : other.segments)
+      segments.push_back (e->clone_type_path_segment ());
+
+    return *this;
+  }
+
+  // move constructors
+  QualifiedPathInType (QualifiedPathInType &&other) = default;
+  QualifiedPathInType &operator= (QualifiedPathInType &&other) = default;
+
+  // Returns whether qualified path in type is in an error state.
+  bool is_error () const { return path_type.is_error (); }
+
+  // Creates an error state qualified path in type.
+  static QualifiedPathInType create_error ()
+  {
+    return QualifiedPathInType (
+      QualifiedPathType::create_error (), nullptr,
+      std::vector<std::unique_ptr<TypePathSegment> > (), Location ());
+  }
+
+  std::string as_string () const override;
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // TODO: is this better? Or is a "vis_pattern" better?
+  QualifiedPathType &get_qualified_path_type ()
+  {
+    rust_assert (!path_type.is_error ());
+    return path_type;
+  }
+
+  std::unique_ptr<TypePathSegment> &get_associated_segment ()
+  {
+    return associated_segment;
+  }
+
+  // TODO: this seems kinda dodgy
+  std::vector<std::unique_ptr<TypePathSegment> > &get_segments ()
+  {
+    return segments;
+  }
+  const std::vector<std::unique_ptr<TypePathSegment> > &get_segments () const
+  {
+    return segments;
+  }
+
+  Location get_locus () const override final { return locus; }
+};
+} // namespace AST
+} // namespace Rust
+
+#endif
diff --git a/gcc/rust/ast/rust-pattern.h b/gcc/rust/ast/rust-pattern.h
new file mode 100644
index 0000000..247af5d
--- /dev/null
+++ b/gcc/rust/ast/rust-pattern.h
@@ -0,0 +1,1576 @@
+// Copyright (C) 2020-2022 Free Software Foundation, Inc.
+
+// This file is part of GCC.
+
+// GCC is free software; you can redistribute it and/or modify it under
+// the terms of the GNU General Public License as published by the Free
+// Software Foundation; either version 3, or (at your option) any later
+// version.
+
+// GCC is distributed in the hope that it will be useful, but WITHOUT ANY
+// WARRANTY; without even the implied warranty of MERCHANTABILITY or
+// FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+// for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with GCC; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+#ifndef RUST_AST_PATTERN_H
+#define RUST_AST_PATTERN_H
+
+#include "rust-ast.h"
+
+namespace Rust {
+namespace AST {
+// Literal pattern AST node (comparing to a literal)
+class LiteralPattern : public Pattern
+{
+  Literal lit;
+  Location locus;
+  NodeId node_id;
+
+public:
+  std::string as_string () const override;
+
+  // Constructor for a literal pattern
+  LiteralPattern (Literal lit, Location locus)
+    : lit (std::move (lit)), locus (locus),
+      node_id (Analysis::Mappings::get ()->get_next_node_id ())
+  {}
+
+  LiteralPattern (std::string val, Literal::LitType type, Location locus)
+    : lit (Literal (std::move (val), type, PrimitiveCoreType::CORETYPE_STR)),
+      locus (locus), node_id (Analysis::Mappings::get ()->get_next_node_id ())
+  {}
+
+  Location get_locus () const override final { return locus; }
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  NodeId get_node_id () const { return node_id; }
+
+  NodeId get_pattern_node_id () const override final { return node_id; }
+
+  Literal &get_literal () { return lit; }
+
+  const Literal &get_literal () const { return lit; }
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  virtual LiteralPattern *clone_pattern_impl () const override
+  {
+    return new LiteralPattern (*this);
+  }
+};
+
+// Identifier pattern AST node (bind value matched to a variable)
+class IdentifierPattern : public Pattern
+{
+  Identifier variable_ident;
+  bool is_ref;
+  bool is_mut;
+
+  // bool has_pattern;
+  std::unique_ptr<Pattern> to_bind;
+  Location locus;
+  NodeId node_id;
+
+public:
+  std::string as_string () const override;
+
+  // Returns whether the IdentifierPattern has a pattern to bind.
+  bool has_pattern_to_bind () const { return to_bind != nullptr; }
+
+  // Constructor
+  IdentifierPattern (Identifier ident, Location locus, bool is_ref = false,
+		     bool is_mut = false,
+		     std::unique_ptr<Pattern> to_bind = nullptr)
+    : Pattern (), variable_ident (std::move (ident)), is_ref (is_ref),
+      is_mut (is_mut), to_bind (std::move (to_bind)), locus (locus),
+      node_id (Analysis::Mappings::get ()->get_next_node_id ())
+  {}
+
+  IdentifierPattern (NodeId node_id, Identifier ident, Location locus,
+		     bool is_ref = false, bool is_mut = false,
+		     std::unique_ptr<Pattern> to_bind = nullptr)
+    : Pattern (), variable_ident (std::move (ident)), is_ref (is_ref),
+      is_mut (is_mut), to_bind (std::move (to_bind)), locus (locus),
+      node_id (node_id)
+  {}
+
+  // Copy constructor with clone
+  IdentifierPattern (IdentifierPattern const &other)
+    : variable_ident (other.variable_ident), is_ref (other.is_ref),
+      is_mut (other.is_mut), locus (other.locus), node_id (other.node_id)
+  {
+    // fix to get prevent null pointer dereference
+    if (other.to_bind != nullptr)
+      to_bind = other.to_bind->clone_pattern ();
+  }
+
+  // Overload assignment operator to use clone
+  IdentifierPattern &operator= (IdentifierPattern const &other)
+  {
+    variable_ident = other.variable_ident;
+    is_ref = other.is_ref;
+    is_mut = other.is_mut;
+    locus = other.locus;
+    node_id = other.node_id;
+
+    // fix to prevent null pointer dereference
+    if (other.to_bind != nullptr)
+      to_bind = other.to_bind->clone_pattern ();
+    else
+      to_bind = nullptr;
+
+    return *this;
+  }
+
+  // default move semantics
+  IdentifierPattern (IdentifierPattern &&other) = default;
+  IdentifierPattern &operator= (IdentifierPattern &&other) = default;
+
+  Location get_locus () const override final { return locus; }
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // TODO: is this better? Or is a "vis_pattern" better?
+  std::unique_ptr<Pattern> &get_pattern_to_bind ()
+  {
+    rust_assert (has_pattern_to_bind ());
+    return to_bind;
+  }
+
+  Identifier get_ident () const { return variable_ident; }
+
+  bool get_is_mut () const { return is_mut; }
+  bool get_is_ref () const { return is_ref; }
+
+  NodeId get_node_id () const { return node_id; }
+
+  NodeId get_pattern_node_id () const override final { return node_id; }
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  IdentifierPattern *clone_pattern_impl () const override
+  {
+    return new IdentifierPattern (*this);
+  }
+};
+
+// AST node for using the '_' wildcard "match any value" pattern
+class WildcardPattern : public Pattern
+{
+  Location locus;
+  NodeId node_id;
+
+public:
+  std::string as_string () const override { return std::string (1, '_'); }
+
+  WildcardPattern (Location locus)
+    : locus (locus), node_id (Analysis::Mappings::get ()->get_next_node_id ())
+  {}
+
+  Location get_locus () const override final { return locus; }
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  NodeId get_node_id () const { return node_id; }
+
+  NodeId get_pattern_node_id () const override final { return node_id; }
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  WildcardPattern *clone_pattern_impl () const override
+  {
+    return new WildcardPattern (*this);
+  }
+};
+
+// Base range pattern bound (lower or upper limit) - abstract
+class RangePatternBound
+{
+public:
+  enum RangePatternBoundType
+  {
+    LITERAL,
+    PATH,
+    QUALPATH
+  };
+
+  virtual ~RangePatternBound () {}
+
+  // Unique pointer custom clone function
+  std::unique_ptr<RangePatternBound> clone_range_pattern_bound () const
+  {
+    return std::unique_ptr<RangePatternBound> (
+      clone_range_pattern_bound_impl ());
+  }
+
+  virtual std::string as_string () const = 0;
+
+  virtual void accept_vis (ASTVisitor &vis) = 0;
+
+  virtual RangePatternBoundType get_bound_type () const = 0;
+
+protected:
+  // pure virtual as RangePatternBound is abstract
+  virtual RangePatternBound *clone_range_pattern_bound_impl () const = 0;
+};
+
+// Literal-based pattern bound
+class RangePatternBoundLiteral : public RangePatternBound
+{
+  Literal literal;
+  /* Can only be a char, byte, int, or float literal - same impl here as
+   * previously */
+
+  // Minus prefixed to literal (if integer or floating-point)
+  bool has_minus;
+
+  Location locus;
+
+public:
+  // Constructor
+  RangePatternBoundLiteral (Literal literal, Location locus,
+			    bool has_minus = false)
+    : literal (literal), has_minus (has_minus), locus (locus)
+  {}
+
+  std::string as_string () const override;
+
+  Literal get_literal () const { return literal; }
+
+  bool get_has_minus () const { return has_minus; }
+
+  Location get_locus () const { return locus; }
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  RangePatternBoundType get_bound_type () const override
+  {
+    return RangePatternBoundType::LITERAL;
+  }
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  RangePatternBoundLiteral *clone_range_pattern_bound_impl () const override
+  {
+    return new RangePatternBoundLiteral (*this);
+  }
+};
+
+// Path-based pattern bound
+class RangePatternBoundPath : public RangePatternBound
+{
+  PathInExpression path;
+
+  /* TODO: should this be refactored so that PathInExpression is a subclass of
+   * RangePatternBound? */
+
+public:
+  RangePatternBoundPath (PathInExpression path) : path (std::move (path)) {}
+
+  std::string as_string () const override { return path.as_string (); }
+
+  Location get_locus () const { return path.get_locus (); }
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // TODO: this mutable getter seems kinda dodgy
+  PathInExpression &get_path () { return path; }
+  const PathInExpression &get_path () const { return path; }
+
+  RangePatternBoundType get_bound_type () const override
+  {
+    return RangePatternBoundType::PATH;
+  }
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  RangePatternBoundPath *clone_range_pattern_bound_impl () const override
+  {
+    return new RangePatternBoundPath (*this);
+  }
+};
+
+// Qualified path-based pattern bound
+class RangePatternBoundQualPath : public RangePatternBound
+{
+  QualifiedPathInExpression path;
+
+  /* TODO: should this be refactored so that QualifiedPathInExpression is a
+   * subclass of RangePatternBound? */
+
+public:
+  RangePatternBoundQualPath (QualifiedPathInExpression path)
+    : path (std::move (path))
+  {}
+
+  std::string as_string () const override { return path.as_string (); }
+
+  Location get_locus () const { return path.get_locus (); }
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // TODO: this mutable getter seems kinda dodgy
+  QualifiedPathInExpression &get_qualified_path () { return path; }
+  const QualifiedPathInExpression &get_qualified_path () const { return path; }
+
+  RangePatternBoundType get_bound_type () const override
+  {
+    return RangePatternBoundType::QUALPATH;
+  }
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  RangePatternBoundQualPath *clone_range_pattern_bound_impl () const override
+  {
+    return new RangePatternBoundQualPath (*this);
+  }
+};
+
+// AST node for matching within a certain range (range pattern)
+class RangePattern : public Pattern
+{
+  std::unique_ptr<RangePatternBound> lower;
+  std::unique_ptr<RangePatternBound> upper;
+
+  bool has_ellipsis_syntax;
+
+  /* location only stored to avoid a dereference - lower pattern should give
+   * correct location so maybe change in future */
+  Location locus;
+  NodeId node_id;
+
+public:
+  std::string as_string () const override;
+
+  // Constructor
+  RangePattern (std::unique_ptr<RangePatternBound> lower,
+		std::unique_ptr<RangePatternBound> upper, Location locus,
+		bool has_ellipsis_syntax = false)
+    : lower (std::move (lower)), upper (std::move (upper)),
+      has_ellipsis_syntax (has_ellipsis_syntax), locus (locus),
+      node_id (Analysis::Mappings::get ()->get_next_node_id ())
+  {}
+
+  // Copy constructor with clone
+  RangePattern (RangePattern const &other)
+    : lower (other.lower->clone_range_pattern_bound ()),
+      upper (other.upper->clone_range_pattern_bound ()),
+      has_ellipsis_syntax (other.has_ellipsis_syntax), locus (other.locus),
+      node_id (other.node_id)
+  {}
+
+  // Overloaded assignment operator to clone
+  RangePattern &operator= (RangePattern const &other)
+  {
+    lower = other.lower->clone_range_pattern_bound ();
+    upper = other.upper->clone_range_pattern_bound ();
+    has_ellipsis_syntax = other.has_ellipsis_syntax;
+    locus = other.locus;
+    node_id = other.node_id;
+
+    return *this;
+  }
+
+  // default move semantics
+  RangePattern (RangePattern &&other) = default;
+  RangePattern &operator= (RangePattern &&other) = default;
+
+  Location get_locus () const override final { return locus; }
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // TODO: is this better? or is a "vis_bound" better?
+  std::unique_ptr<RangePatternBound> &get_lower_bound ()
+  {
+    rust_assert (lower != nullptr);
+    return lower;
+  }
+
+  std::unique_ptr<RangePatternBound> &get_upper_bound ()
+  {
+    rust_assert (upper != nullptr);
+    return upper;
+  }
+
+  NodeId get_node_id () const { return node_id; }
+
+  NodeId get_pattern_node_id () const override final { return node_id; }
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  RangePattern *clone_pattern_impl () const override
+  {
+    return new RangePattern (*this);
+  }
+};
+
+// AST node for pattern based on dereferencing the pointers given
+class ReferencePattern : public Pattern
+{
+  bool has_two_amps;
+  bool is_mut;
+  std::unique_ptr<Pattern> pattern;
+  Location locus;
+  NodeId node_id;
+
+public:
+  std::string as_string () const override;
+
+  ReferencePattern (std::unique_ptr<Pattern> pattern, bool is_mut_reference,
+		    bool ref_has_two_amps, Location locus)
+    : has_two_amps (ref_has_two_amps), is_mut (is_mut_reference),
+      pattern (std::move (pattern)), locus (locus),
+      node_id (Analysis::Mappings::get ()->get_next_node_id ())
+  {}
+
+  // Copy constructor requires clone
+  ReferencePattern (ReferencePattern const &other)
+    : has_two_amps (other.has_two_amps), is_mut (other.is_mut),
+      pattern (other.pattern->clone_pattern ()), locus (other.locus),
+      node_id (other.node_id)
+  {}
+
+  // Overload assignment operator to clone
+  ReferencePattern &operator= (ReferencePattern const &other)
+  {
+    pattern = other.pattern->clone_pattern ();
+    is_mut = other.is_mut;
+    has_two_amps = other.has_two_amps;
+    locus = other.locus;
+    node_id = other.node_id;
+
+    return *this;
+  }
+
+  // default move semantics
+  ReferencePattern (ReferencePattern &&other) = default;
+  ReferencePattern &operator= (ReferencePattern &&other) = default;
+
+  Location get_locus () const override final { return locus; }
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // TODO: is this better? Or is a "vis_pattern" better?
+  std::unique_ptr<Pattern> &get_referenced_pattern ()
+  {
+    rust_assert (pattern != nullptr);
+    return pattern;
+  }
+
+  NodeId get_node_id () const { return node_id; }
+
+  NodeId get_pattern_node_id () const override final { return node_id; }
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  ReferencePattern *clone_pattern_impl () const override
+  {
+    return new ReferencePattern (*this);
+  }
+};
+
+#if 0
+// aka StructPatternEtCetera; potential element in struct pattern
+struct StructPatternEtc
+{
+private:
+  std::vector<Attribute> outer_attrs;
+
+  // should this store location data?
+
+public:
+  StructPatternEtc (std::vector<Attribute> outer_attribs)
+    : outer_attrs (std::move (outer_attribs))
+  {}
+
+  // Creates an empty StructPatternEtc
+  static StructPatternEtc create_empty ()
+  {
+    return StructPatternEtc (std::vector<Attribute> ());
+  }
+};
+#endif
+
+// Base class for a single field in a struct pattern - abstract
+class StructPatternField
+{
+  std::vector<Attribute> outer_attrs;
+  Location locus;
+
+protected:
+  NodeId node_id;
+
+public:
+  enum ItemType
+  {
+    TUPLE_PAT,
+    IDENT_PAT,
+    IDENT
+  };
+
+  virtual ~StructPatternField () {}
+
+  // Unique pointer custom clone function
+  std::unique_ptr<StructPatternField> clone_struct_pattern_field () const
+  {
+    return std::unique_ptr<StructPatternField> (
+      clone_struct_pattern_field_impl ());
+  }
+
+  virtual std::string as_string () const;
+
+  Location get_locus () const { return locus; }
+
+  virtual void accept_vis (ASTVisitor &vis) = 0;
+
+  virtual void mark_for_strip () = 0;
+  virtual bool is_marked_for_strip () const = 0;
+  virtual ItemType get_item_type () const = 0;
+
+  NodeId get_node_id () const { return node_id; }
+
+  // TODO: seems kinda dodgy. Think of better way.
+  std::vector<Attribute> &get_outer_attrs () { return outer_attrs; }
+  const std::vector<Attribute> &get_outer_attrs () const { return outer_attrs; }
+
+protected:
+  StructPatternField (std::vector<Attribute> outer_attribs, Location locus,
+		      NodeId node_id)
+    : outer_attrs (std::move (outer_attribs)), locus (locus), node_id (node_id)
+  {}
+
+  // Clone function implementation as pure virtual method
+  virtual StructPatternField *clone_struct_pattern_field_impl () const = 0;
+};
+
+// Tuple pattern single field in a struct pattern
+class StructPatternFieldTuplePat : public StructPatternField
+{
+  TupleIndex index;
+  std::unique_ptr<Pattern> tuple_pattern;
+
+public:
+  StructPatternFieldTuplePat (TupleIndex index,
+			      std::unique_ptr<Pattern> tuple_pattern,
+			      std::vector<Attribute> outer_attribs,
+			      Location locus)
+    : StructPatternField (std::move (outer_attribs), locus,
+			  Analysis::Mappings::get ()->get_next_node_id ()),
+      index (index), tuple_pattern (std::move (tuple_pattern))
+  {}
+
+  // Copy constructor requires clone
+  StructPatternFieldTuplePat (StructPatternFieldTuplePat const &other)
+    : StructPatternField (other), index (other.index)
+  {
+    // guard to prevent null dereference (only required if error state)
+    node_id = other.get_node_id ();
+    if (other.tuple_pattern != nullptr)
+      tuple_pattern = other.tuple_pattern->clone_pattern ();
+  }
+
+  // Overload assignment operator to perform clone
+  StructPatternFieldTuplePat &
+  operator= (StructPatternFieldTuplePat const &other)
+  {
+    StructPatternField::operator= (other);
+    index = other.index;
+    // outer_attrs = other.outer_attrs;
+    node_id = other.get_node_id ();
+
+    // guard to prevent null dereference (only required if error state)
+    if (other.tuple_pattern != nullptr)
+      tuple_pattern = other.tuple_pattern->clone_pattern ();
+    else
+      tuple_pattern = nullptr;
+
+    return *this;
+  }
+
+  // default move semantics
+  StructPatternFieldTuplePat (StructPatternFieldTuplePat &&other) = default;
+  StructPatternFieldTuplePat &operator= (StructPatternFieldTuplePat &&other)
+    = default;
+
+  std::string as_string () const override;
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // based on idea of tuple pattern no longer existing
+  void mark_for_strip () override { tuple_pattern = nullptr; }
+  bool is_marked_for_strip () const override
+  {
+    return tuple_pattern == nullptr;
+  }
+
+  // TODO: is this better? Or is a "vis_pattern" better?
+  std::unique_ptr<Pattern> &get_index_pattern ()
+  {
+    rust_assert (tuple_pattern != nullptr);
+    return tuple_pattern;
+  }
+
+  ItemType get_item_type () const override final { return ItemType::TUPLE_PAT; }
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  StructPatternFieldTuplePat *clone_struct_pattern_field_impl () const override
+  {
+    return new StructPatternFieldTuplePat (*this);
+  }
+};
+
+// Identifier pattern single field in a struct pattern
+class StructPatternFieldIdentPat : public StructPatternField
+{
+  Identifier ident;
+  std::unique_ptr<Pattern> ident_pattern;
+
+public:
+  StructPatternFieldIdentPat (Identifier ident,
+			      std::unique_ptr<Pattern> ident_pattern,
+			      std::vector<Attribute> outer_attrs,
+			      Location locus)
+    : StructPatternField (std::move (outer_attrs), locus,
+			  Analysis::Mappings::get ()->get_next_node_id ()),
+      ident (std::move (ident)), ident_pattern (std::move (ident_pattern))
+  {}
+
+  // Copy constructor requires clone
+  StructPatternFieldIdentPat (StructPatternFieldIdentPat const &other)
+    : StructPatternField (other), ident (other.ident)
+  {
+    // guard to prevent null dereference (only required if error state)
+    node_id = other.get_node_id ();
+    if (other.ident_pattern != nullptr)
+      ident_pattern = other.ident_pattern->clone_pattern ();
+  }
+
+  // Overload assignment operator to clone
+  StructPatternFieldIdentPat &
+  operator= (StructPatternFieldIdentPat const &other)
+  {
+    StructPatternField::operator= (other);
+    ident = other.ident;
+    // outer_attrs = other.outer_attrs;
+    node_id = other.get_node_id ();
+
+    // guard to prevent null dereference (only required if error state)
+    if (other.ident_pattern != nullptr)
+      ident_pattern = other.ident_pattern->clone_pattern ();
+    else
+      ident_pattern = nullptr;
+
+    return *this;
+  }
+
+  // default move semantics
+  StructPatternFieldIdentPat (StructPatternFieldIdentPat &&other) = default;
+  StructPatternFieldIdentPat &operator= (StructPatternFieldIdentPat &&other)
+    = default;
+
+  std::string as_string () const override;
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // based on idea of identifier pattern no longer existing
+  void mark_for_strip () override { ident_pattern = nullptr; }
+  bool is_marked_for_strip () const override
+  {
+    return ident_pattern == nullptr;
+  }
+
+  const Identifier &get_identifier () const { return ident; }
+
+  // TODO: is this better? Or is a "vis_pattern" better?
+  std::unique_ptr<Pattern> &get_ident_pattern ()
+  {
+    rust_assert (ident_pattern != nullptr);
+    return ident_pattern;
+  }
+
+  ItemType get_item_type () const override final { return ItemType::IDENT_PAT; }
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  StructPatternFieldIdentPat *clone_struct_pattern_field_impl () const override
+  {
+    return new StructPatternFieldIdentPat (*this);
+  }
+};
+
+// Identifier only (with no pattern) single field in a struct pattern
+class StructPatternFieldIdent : public StructPatternField
+{
+  bool has_ref;
+  bool has_mut;
+  Identifier ident;
+
+public:
+  StructPatternFieldIdent (Identifier ident, bool is_ref, bool is_mut,
+			   std::vector<Attribute> outer_attrs, Location locus)
+    : StructPatternField (std::move (outer_attrs), locus,
+			  Analysis::Mappings::get ()->get_next_node_id ()),
+      has_ref (is_ref), has_mut (is_mut), ident (std::move (ident))
+  {}
+
+  std::string as_string () const override;
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // based on idea of identifier no longer existing
+  void mark_for_strip () override { ident = {}; }
+  bool is_marked_for_strip () const override { return ident.empty (); }
+
+  const Identifier &get_identifier () const { return ident; }
+
+  ItemType get_item_type () const override final { return ItemType::IDENT; }
+
+  bool is_ref () const { return has_ref; }
+
+  bool is_mut () const { return has_mut; }
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  StructPatternFieldIdent *clone_struct_pattern_field_impl () const override
+  {
+    return new StructPatternFieldIdent (*this);
+  }
+};
+
+// Elements of a struct pattern
+struct StructPatternElements
+{
+private:
+  // bool has_struct_pattern_fields;
+  std::vector<std::unique_ptr<StructPatternField> > fields;
+
+  bool has_struct_pattern_etc;
+  std::vector<Attribute> struct_pattern_etc_attrs;
+  // StructPatternEtc etc;
+
+  // must have at least one of the two and maybe both
+
+  // should this store location data?
+
+public:
+  // Returns whether there are any struct pattern fields
+  bool has_struct_pattern_fields () const { return !fields.empty (); }
+
+  /* Returns whether the struct pattern elements is entirely empty (no fields,
+   * no etc). */
+  bool is_empty () const
+  {
+    return !has_struct_pattern_fields () && !has_struct_pattern_etc;
+  }
+
+  bool has_etc () const { return has_struct_pattern_etc; }
+
+  // Constructor for StructPatternElements with both (potentially)
+  StructPatternElements (
+    std::vector<std::unique_ptr<StructPatternField> > fields,
+    std::vector<Attribute> etc_attrs)
+    : fields (std::move (fields)), has_struct_pattern_etc (true),
+      struct_pattern_etc_attrs (std::move (etc_attrs))
+  {}
+
+  // Constructor for StructPatternElements with no StructPatternEtc
+  StructPatternElements (
+    std::vector<std::unique_ptr<StructPatternField> > fields)
+    : fields (std::move (fields)), has_struct_pattern_etc (false),
+      struct_pattern_etc_attrs ()
+  {}
+
+  // Copy constructor with vector clone
+  StructPatternElements (StructPatternElements const &other)
+    : has_struct_pattern_etc (other.has_struct_pattern_etc),
+      struct_pattern_etc_attrs (other.struct_pattern_etc_attrs)
+  {
+    fields.reserve (other.fields.size ());
+    for (const auto &e : other.fields)
+      fields.push_back (e->clone_struct_pattern_field ());
+  }
+
+  // Overloaded assignment operator with vector clone
+  StructPatternElements &operator= (StructPatternElements const &other)
+  {
+    struct_pattern_etc_attrs = other.struct_pattern_etc_attrs;
+    has_struct_pattern_etc = other.has_struct_pattern_etc;
+
+    fields.reserve (other.fields.size ());
+    for (const auto &e : other.fields)
+      fields.push_back (e->clone_struct_pattern_field ());
+
+    return *this;
+  }
+
+  // move constructors
+  StructPatternElements (StructPatternElements &&other) = default;
+  StructPatternElements &operator= (StructPatternElements &&other) = default;
+
+  // Creates an empty StructPatternElements
+  static StructPatternElements create_empty ()
+  {
+    return StructPatternElements (
+      std::vector<std::unique_ptr<StructPatternField> > ());
+  }
+
+  std::string as_string () const;
+
+  // TODO: seems kinda dodgy. Think of better way.
+  std::vector<std::unique_ptr<StructPatternField> > &
+  get_struct_pattern_fields ()
+  {
+    return fields;
+  }
+  const std::vector<std::unique_ptr<StructPatternField> > &
+  get_struct_pattern_fields () const
+  {
+    return fields;
+  }
+
+  std::vector<Attribute> &get_etc_outer_attrs ()
+  {
+    return struct_pattern_etc_attrs;
+  }
+  const std::vector<Attribute> &get_etc_outer_attrs () const
+  {
+    return struct_pattern_etc_attrs;
+  }
+
+  void strip_etc ()
+  {
+    has_struct_pattern_etc = false;
+    struct_pattern_etc_attrs.clear ();
+    struct_pattern_etc_attrs.shrink_to_fit ();
+  }
+};
+
+// Struct pattern AST node representation
+class StructPattern : public Pattern
+{
+  PathInExpression path;
+
+  // bool has_struct_pattern_elements;
+  StructPatternElements elems;
+
+  NodeId node_id;
+  Location locus;
+
+public:
+  std::string as_string () const override;
+
+  // Constructs a struct pattern from specified StructPatternElements
+  StructPattern (PathInExpression struct_path, Location locus,
+		 StructPatternElements elems
+		 = StructPatternElements::create_empty ())
+    : path (std::move (struct_path)), elems (std::move (elems)),
+      node_id (Analysis::Mappings::get ()->get_next_node_id ()), locus (locus)
+  {}
+
+  /* TODO: constructor to construct via elements included in
+   * StructPatternElements */
+
+  /* Returns whether struct pattern has any struct pattern elements (if not, it
+   * is empty). */
+  bool has_struct_pattern_elems () const { return !elems.is_empty (); }
+
+  Location get_locus () const { return path.get_locus (); }
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // TODO: seems kinda dodgy. Think of better way.
+  StructPatternElements &get_struct_pattern_elems () { return elems; }
+  const StructPatternElements &get_struct_pattern_elems () const
+  {
+    return elems;
+  }
+
+  PathInExpression &get_path () { return path; }
+  const PathInExpression &get_path () const { return path; }
+
+  NodeId get_node_id () const { return node_id; }
+
+  NodeId get_pattern_node_id () const override final { return node_id; }
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  StructPattern *clone_pattern_impl () const override
+  {
+    return new StructPattern (*this);
+  }
+};
+
+// Base abstract class for patterns used in TupleStructPattern
+class TupleStructItems
+{
+public:
+  enum ItemType
+  {
+    RANGE,
+    NO_RANGE
+  };
+
+  virtual ~TupleStructItems () {}
+
+  // TODO: should this store location data?
+
+  // Unique pointer custom clone function
+  std::unique_ptr<TupleStructItems> clone_tuple_struct_items () const
+  {
+    return std::unique_ptr<TupleStructItems> (clone_tuple_struct_items_impl ());
+  }
+
+  virtual std::string as_string () const = 0;
+
+  virtual void accept_vis (ASTVisitor &vis) = 0;
+
+  virtual ItemType get_item_type () const = 0;
+
+protected:
+  // pure virtual clone implementation
+  virtual TupleStructItems *clone_tuple_struct_items_impl () const = 0;
+};
+
+// Class for non-ranged tuple struct pattern patterns
+class TupleStructItemsNoRange : public TupleStructItems
+{
+  std::vector<std::unique_ptr<Pattern> > patterns;
+
+public:
+  TupleStructItemsNoRange (std::vector<std::unique_ptr<Pattern> > patterns)
+    : patterns (std::move (patterns))
+  {}
+
+  // Copy constructor with vector clone
+  TupleStructItemsNoRange (TupleStructItemsNoRange const &other)
+  {
+    patterns.reserve (other.patterns.size ());
+    for (const auto &e : other.patterns)
+      patterns.push_back (e->clone_pattern ());
+  }
+
+  // Overloaded assignment operator with vector clone
+  TupleStructItemsNoRange &operator= (TupleStructItemsNoRange const &other)
+  {
+    patterns.reserve (other.patterns.size ());
+    for (const auto &e : other.patterns)
+      patterns.push_back (e->clone_pattern ());
+
+    return *this;
+  }
+
+  // move constructors
+  TupleStructItemsNoRange (TupleStructItemsNoRange &&other) = default;
+  TupleStructItemsNoRange &operator= (TupleStructItemsNoRange &&other)
+    = default;
+
+  std::string as_string () const override;
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // TODO: seems kinda dodgy. Think of better way.
+  std::vector<std::unique_ptr<Pattern> > &get_patterns () { return patterns; }
+  const std::vector<std::unique_ptr<Pattern> > &get_patterns () const
+  {
+    return patterns;
+  }
+
+  ItemType get_item_type () const override final { return ItemType::NO_RANGE; }
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  TupleStructItemsNoRange *clone_tuple_struct_items_impl () const override
+  {
+    return new TupleStructItemsNoRange (*this);
+  }
+};
+
+// Class for ranged tuple struct pattern patterns
+class TupleStructItemsRange : public TupleStructItems
+{
+  std::vector<std::unique_ptr<Pattern> > lower_patterns;
+  std::vector<std::unique_ptr<Pattern> > upper_patterns;
+
+public:
+  TupleStructItemsRange (std::vector<std::unique_ptr<Pattern> > lower_patterns,
+			 std::vector<std::unique_ptr<Pattern> > upper_patterns)
+    : lower_patterns (std::move (lower_patterns)),
+      upper_patterns (std::move (upper_patterns))
+  {}
+
+  // Copy constructor with vector clone
+  TupleStructItemsRange (TupleStructItemsRange const &other)
+  {
+    lower_patterns.reserve (other.lower_patterns.size ());
+    for (const auto &e : other.lower_patterns)
+      lower_patterns.push_back (e->clone_pattern ());
+
+    upper_patterns.reserve (other.upper_patterns.size ());
+    for (const auto &e : other.upper_patterns)
+      upper_patterns.push_back (e->clone_pattern ());
+  }
+
+  // Overloaded assignment operator to clone
+  TupleStructItemsRange &operator= (TupleStructItemsRange const &other)
+  {
+    lower_patterns.reserve (other.lower_patterns.size ());
+    for (const auto &e : other.lower_patterns)
+      lower_patterns.push_back (e->clone_pattern ());
+
+    upper_patterns.reserve (other.upper_patterns.size ());
+    for (const auto &e : other.upper_patterns)
+      upper_patterns.push_back (e->clone_pattern ());
+
+    return *this;
+  }
+
+  // move constructors
+  TupleStructItemsRange (TupleStructItemsRange &&other) = default;
+  TupleStructItemsRange &operator= (TupleStructItemsRange &&other) = default;
+
+  std::string as_string () const override;
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // TODO: seems kinda dodgy. Think of better way.
+  std::vector<std::unique_ptr<Pattern> > &get_lower_patterns ()
+  {
+    return lower_patterns;
+  }
+  const std::vector<std::unique_ptr<Pattern> > &get_lower_patterns () const
+  {
+    return lower_patterns;
+  }
+
+  // TODO: seems kinda dodgy. Think of better way.
+  std::vector<std::unique_ptr<Pattern> > &get_upper_patterns ()
+  {
+    return upper_patterns;
+  }
+  const std::vector<std::unique_ptr<Pattern> > &get_upper_patterns () const
+  {
+    return upper_patterns;
+  }
+
+  ItemType get_item_type () const override final { return ItemType::RANGE; }
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  TupleStructItemsRange *clone_tuple_struct_items_impl () const override
+  {
+    return new TupleStructItemsRange (*this);
+  }
+};
+
+// AST node representing a tuple struct pattern
+class TupleStructPattern : public Pattern
+{
+  PathInExpression path;
+  std::unique_ptr<TupleStructItems> items;
+  NodeId node_id;
+
+  /* TOOD: should this store location data? current accessor uses path location
+   * data */
+
+public:
+  std::string as_string () const override;
+
+  // Returns whether the pattern has tuple struct items.
+  bool has_items () const { return items != nullptr; }
+
+  TupleStructPattern (PathInExpression tuple_struct_path,
+		      std::unique_ptr<TupleStructItems> items)
+    : path (std::move (tuple_struct_path)), items (std::move (items)),
+      node_id (Analysis::Mappings::get ()->get_next_node_id ())
+  {}
+
+  // Copy constructor required to clone
+  TupleStructPattern (TupleStructPattern const &other) : path (other.path)
+  {
+    // guard to protect from null dereference
+    node_id = other.node_id;
+    if (other.items != nullptr)
+      items = other.items->clone_tuple_struct_items ();
+  }
+
+  // Operator overload assignment operator to clone
+  TupleStructPattern &operator= (TupleStructPattern const &other)
+  {
+    path = other.path;
+    node_id = other.node_id;
+
+    // guard to protect from null dereference
+    if (other.items != nullptr)
+      items = other.items->clone_tuple_struct_items ();
+    else
+      items = nullptr;
+
+    return *this;
+  }
+
+  // move constructors
+  TupleStructPattern (TupleStructPattern &&other) = default;
+  TupleStructPattern &operator= (TupleStructPattern &&other) = default;
+
+  Location get_locus () const override { return path.get_locus (); }
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // TODO: seems kinda dodgy. Think of better way.
+  std::unique_ptr<TupleStructItems> &get_items ()
+  {
+    rust_assert (has_items ());
+    return items;
+  }
+
+  PathInExpression &get_path () { return path; }
+  const PathInExpression &get_path () const { return path; }
+
+  NodeId get_node_id () const { return node_id; }
+
+  NodeId get_pattern_node_id () const override final { return node_id; }
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  TupleStructPattern *clone_pattern_impl () const override
+  {
+    return new TupleStructPattern (*this);
+  }
+};
+
+// Base abstract class representing TuplePattern patterns
+class TuplePatternItems
+{
+public:
+  enum TuplePatternItemType
+  {
+    MULTIPLE,
+    RANGED,
+  };
+
+  virtual ~TuplePatternItems () {}
+
+  // TODO: should this store location data?
+
+  // Unique pointer custom clone function
+  std::unique_ptr<TuplePatternItems> clone_tuple_pattern_items () const
+  {
+    return std::unique_ptr<TuplePatternItems> (
+      clone_tuple_pattern_items_impl ());
+  }
+
+  virtual std::string as_string () const = 0;
+
+  virtual void accept_vis (ASTVisitor &vis) = 0;
+
+  virtual TuplePatternItemType get_pattern_type () const = 0;
+
+protected:
+  // pure virtual clone implementation
+  virtual TuplePatternItems *clone_tuple_pattern_items_impl () const = 0;
+};
+
+// Class representing TuplePattern patterns where there is only a single pattern
+/*class TuplePatternItemsSingle : public TuplePatternItems {
+    // Pattern pattern;
+    std::unique_ptr<Pattern> pattern;
+
+  public:
+    TuplePatternItemsSingle(Pattern* pattern) : pattern(pattern) {}
+
+    // Copy constructor uses clone
+    TuplePatternItemsSingle(TuplePatternItemsSingle const& other) :
+      pattern(other.pattern->clone_pattern()) {}
+
+    // Destructor - define here if required
+
+    // Overload assignment operator to clone
+    TuplePatternItemsSingle& operator=(TuplePatternItemsSingle const& other) {
+	pattern = other.pattern->clone_pattern();
+
+	return *this;
+    }
+
+    // move constructors
+    TuplePatternItemsSingle(TuplePatternItemsSingle&& other) = default;
+    TuplePatternItemsSingle& operator=(TuplePatternItemsSingle&& other) =
+default;
+
+  protected:
+    // Use covariance to implement clone function as returning this object
+rather than base virtual TuplePatternItemsSingle*
+clone_tuple_pattern_items_impl() const override { return new
+TuplePatternItemsSingle(*this);
+    }
+};*/
+// removed in favour of single-element TuplePatternItemsMultiple
+
+// Class representing TuplePattern patterns where there are multiple patterns
+class TuplePatternItemsMultiple : public TuplePatternItems
+{
+  std::vector<std::unique_ptr<Pattern> > patterns;
+
+public:
+  TuplePatternItemsMultiple (std::vector<std::unique_ptr<Pattern> > patterns)
+    : patterns (std::move (patterns))
+  {}
+
+  // Copy constructor with vector clone
+  TuplePatternItemsMultiple (TuplePatternItemsMultiple const &other)
+  {
+    patterns.reserve (other.patterns.size ());
+    for (const auto &e : other.patterns)
+      patterns.push_back (e->clone_pattern ());
+  }
+
+  // Overloaded assignment operator to vector clone
+  TuplePatternItemsMultiple &operator= (TuplePatternItemsMultiple const &other)
+  {
+    patterns.reserve (other.patterns.size ());
+    for (const auto &e : other.patterns)
+      patterns.push_back (e->clone_pattern ());
+
+    return *this;
+  }
+
+  // move constructors
+  TuplePatternItemsMultiple (TuplePatternItemsMultiple &&other) = default;
+  TuplePatternItemsMultiple &operator= (TuplePatternItemsMultiple &&other)
+    = default;
+
+  std::string as_string () const override;
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // TODO: seems kinda dodgy. Think of better way.
+  std::vector<std::unique_ptr<Pattern> > &get_patterns () { return patterns; }
+  const std::vector<std::unique_ptr<Pattern> > &get_patterns () const
+  {
+    return patterns;
+  }
+
+  TuplePatternItemType get_pattern_type () const override
+  {
+    return TuplePatternItemType::MULTIPLE;
+  }
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  TuplePatternItemsMultiple *clone_tuple_pattern_items_impl () const override
+  {
+    return new TuplePatternItemsMultiple (*this);
+  }
+};
+
+// Class representing TuplePattern patterns where there are a range of patterns
+class TuplePatternItemsRanged : public TuplePatternItems
+{
+  std::vector<std::unique_ptr<Pattern> > lower_patterns;
+  std::vector<std::unique_ptr<Pattern> > upper_patterns;
+
+public:
+  TuplePatternItemsRanged (
+    std::vector<std::unique_ptr<Pattern> > lower_patterns,
+    std::vector<std::unique_ptr<Pattern> > upper_patterns)
+    : lower_patterns (std::move (lower_patterns)),
+      upper_patterns (std::move (upper_patterns))
+  {}
+
+  // Copy constructor with vector clone
+  TuplePatternItemsRanged (TuplePatternItemsRanged const &other)
+  {
+    lower_patterns.reserve (other.lower_patterns.size ());
+    for (const auto &e : other.lower_patterns)
+      lower_patterns.push_back (e->clone_pattern ());
+
+    upper_patterns.reserve (other.upper_patterns.size ());
+    for (const auto &e : other.upper_patterns)
+      upper_patterns.push_back (e->clone_pattern ());
+  }
+
+  // Overloaded assignment operator to clone
+  TuplePatternItemsRanged &operator= (TuplePatternItemsRanged const &other)
+  {
+    lower_patterns.reserve (other.lower_patterns.size ());
+    for (const auto &e : other.lower_patterns)
+      lower_patterns.push_back (e->clone_pattern ());
+
+    upper_patterns.reserve (other.upper_patterns.size ());
+    for (const auto &e : other.upper_patterns)
+      upper_patterns.push_back (e->clone_pattern ());
+
+    return *this;
+  }
+
+  // move constructors
+  TuplePatternItemsRanged (TuplePatternItemsRanged &&other) = default;
+  TuplePatternItemsRanged &operator= (TuplePatternItemsRanged &&other)
+    = default;
+
+  std::string as_string () const override;
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // TODO: seems kinda dodgy. Think of better way.
+  std::vector<std::unique_ptr<Pattern> > &get_lower_patterns ()
+  {
+    return lower_patterns;
+  }
+  const std::vector<std::unique_ptr<Pattern> > &get_lower_patterns () const
+  {
+    return lower_patterns;
+  }
+
+  // TODO: seems kinda dodgy. Think of better way.
+  std::vector<std::unique_ptr<Pattern> > &get_upper_patterns ()
+  {
+    return upper_patterns;
+  }
+  const std::vector<std::unique_ptr<Pattern> > &get_upper_patterns () const
+  {
+    return upper_patterns;
+  }
+
+  TuplePatternItemType get_pattern_type () const override
+  {
+    return TuplePatternItemType::RANGED;
+  }
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  TuplePatternItemsRanged *clone_tuple_pattern_items_impl () const override
+  {
+    return new TuplePatternItemsRanged (*this);
+  }
+};
+
+// AST node representing a tuple pattern
+class TuplePattern : public Pattern
+{
+  // bool has_tuple_pattern_items;
+  std::unique_ptr<TuplePatternItems> items;
+  Location locus;
+  NodeId node_id;
+
+public:
+  std::string as_string () const override;
+
+  // Returns true if the tuple pattern has items
+  bool has_tuple_pattern_items () const { return items != nullptr; }
+
+  TuplePattern (std::unique_ptr<TuplePatternItems> items, Location locus)
+    : items (std::move (items)), locus (locus),
+      node_id (Analysis::Mappings::get ()->get_next_node_id ())
+  {}
+
+  // Copy constructor requires clone
+  TuplePattern (TuplePattern const &other) : locus (other.locus)
+  {
+    // guard to prevent null dereference
+    node_id = other.node_id;
+    if (other.items != nullptr)
+      items = other.items->clone_tuple_pattern_items ();
+  }
+
+  // Overload assignment operator to clone
+  TuplePattern &operator= (TuplePattern const &other)
+  {
+    locus = other.locus;
+    node_id = other.node_id;
+
+    // guard to prevent null dereference
+    if (other.items != nullptr)
+      items = other.items->clone_tuple_pattern_items ();
+    else
+      items = nullptr;
+
+    return *this;
+  }
+
+  Location get_locus () const override final { return locus; }
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // TODO: seems kinda dodgy. Think of better way.
+  std::unique_ptr<TuplePatternItems> &get_items ()
+  {
+    rust_assert (has_tuple_pattern_items ());
+    return items;
+  }
+
+  NodeId get_node_id () const { return node_id; }
+
+  NodeId get_pattern_node_id () const override final { return node_id; }
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  TuplePattern *clone_pattern_impl () const override
+  {
+    return new TuplePattern (*this);
+  }
+};
+
+// AST node representing a pattern in parentheses, used to control precedence
+class GroupedPattern : public Pattern
+{
+  std::unique_ptr<Pattern> pattern_in_parens;
+  Location locus;
+  NodeId node_id;
+
+public:
+  std::string as_string () const override
+  {
+    return "(" + pattern_in_parens->as_string () + ")";
+  }
+
+  GroupedPattern (std::unique_ptr<Pattern> pattern_in_parens, Location locus)
+    : pattern_in_parens (std::move (pattern_in_parens)), locus (locus),
+      node_id (Analysis::Mappings::get ()->get_next_node_id ())
+  {}
+
+  // Copy constructor uses clone
+  GroupedPattern (GroupedPattern const &other)
+    : pattern_in_parens (other.pattern_in_parens->clone_pattern ()),
+      locus (other.locus), node_id (other.node_id)
+  {}
+
+  // Overload assignment operator to clone
+  GroupedPattern &operator= (GroupedPattern const &other)
+  {
+    pattern_in_parens = other.pattern_in_parens->clone_pattern ();
+    locus = other.locus;
+    node_id = other.node_id;
+
+    return *this;
+  }
+
+  // default move semantics
+  GroupedPattern (GroupedPattern &&other) = default;
+  GroupedPattern &operator= (GroupedPattern &&other) = default;
+
+  Location get_locus () const override final { return locus; }
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // TODO: seems kinda dodgy. Think of better way.
+  std::unique_ptr<Pattern> &get_pattern_in_parens ()
+  {
+    rust_assert (pattern_in_parens != nullptr);
+    return pattern_in_parens;
+  }
+
+  NodeId get_node_id () const { return node_id; }
+
+  NodeId get_pattern_node_id () const override final { return node_id; }
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  GroupedPattern *clone_pattern_impl () const override
+  {
+    return new GroupedPattern (*this);
+  }
+};
+
+// AST node representing patterns that can match slices and arrays
+class SlicePattern : public Pattern
+{
+  std::vector<std::unique_ptr<Pattern> > items;
+  Location locus;
+  NodeId node_id;
+
+public:
+  std::string as_string () const override;
+
+  SlicePattern (std::vector<std::unique_ptr<Pattern> > items, Location locus)
+    : items (std::move (items)), locus (locus),
+      node_id (Analysis::Mappings::get ()->get_next_node_id ())
+  {}
+
+  // Copy constructor with vector clone
+  SlicePattern (SlicePattern const &other) : locus (other.locus)
+  {
+    node_id = other.node_id;
+    items.reserve (other.items.size ());
+    for (const auto &e : other.items)
+      items.push_back (e->clone_pattern ());
+  }
+
+  // Overloaded assignment operator to vector clone
+  SlicePattern &operator= (SlicePattern const &other)
+  {
+    locus = other.locus;
+    node_id = other.node_id;
+
+    items.reserve (other.items.size ());
+    for (const auto &e : other.items)
+      items.push_back (e->clone_pattern ());
+
+    return *this;
+  }
+
+  // move constructors
+  SlicePattern (SlicePattern &&other) = default;
+  SlicePattern &operator= (SlicePattern &&other) = default;
+
+  Location get_locus () const override final { return locus; }
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // TODO: seems kinda dodgy. Think of better way.
+  std::vector<std::unique_ptr<Pattern> > &get_items () { return items; }
+  const std::vector<std::unique_ptr<Pattern> > &get_items () const
+  {
+    return items;
+  }
+
+  NodeId get_node_id () const { return node_id; }
+
+  NodeId get_pattern_node_id () const override final { return node_id; }
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  SlicePattern *clone_pattern_impl () const override
+  {
+    return new SlicePattern (*this);
+  }
+};
+
+// Moved definition to rust-path.h
+class PathPattern;
+
+// Forward decls for paths (defined in rust-path.h)
+class PathInExpression;
+class QualifiedPathInExpression;
+
+// Replaced with forward decl - defined in rust-macro.h
+class MacroInvocation;
+} // namespace AST
+} // namespace Rust
+
+#endif
diff --git a/gcc/rust/ast/rust-stmt.h b/gcc/rust/ast/rust-stmt.h
new file mode 100644
index 0000000..9d95c3e
--- /dev/null
+++ b/gcc/rust/ast/rust-stmt.h
@@ -0,0 +1,358 @@
+// Copyright (C) 2020-2022 Free Software Foundation, Inc.
+
+// This file is part of GCC.
+
+// GCC is free software; you can redistribute it and/or modify it under
+// the terms of the GNU General Public License as published by the Free
+// Software Foundation; either version 3, or (at your option) any later
+// version.
+
+// GCC is distributed in the hope that it will be useful, but WITHOUT ANY
+// WARRANTY; without even the implied warranty of MERCHANTABILITY or
+// FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+// for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with GCC; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+#ifndef RUST_AST_STATEMENT_H
+#define RUST_AST_STATEMENT_H
+
+#include "rust-ast.h"
+#include "rust-path.h"
+#include "rust-expr.h"
+
+namespace Rust {
+namespace AST {
+// Just a semi-colon, which apparently is a statement.
+class EmptyStmt : public Stmt
+{
+  Location locus;
+
+  // TODO: find another way to store this to save memory?
+  bool marked_for_strip = false;
+
+public:
+  std::string as_string () const override { return std::string (1, ';'); }
+
+  EmptyStmt (Location locus) : locus (locus) {}
+
+  Location get_locus () const override final { return locus; }
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // Can't think of any invalid invariants, so store boolean.
+  void mark_for_strip () override { marked_for_strip = true; }
+  bool is_marked_for_strip () const override { return marked_for_strip; }
+
+  bool is_item () const override final { return false; }
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  EmptyStmt *clone_stmt_impl () const override { return new EmptyStmt (*this); }
+};
+
+/* Variable assignment let statement - type of "declaration statement" as it
+ * introduces new name into scope */
+class LetStmt : public Stmt
+{
+  // bool has_outer_attrs;
+  std::vector<Attribute> outer_attrs;
+
+  std::unique_ptr<Pattern> variables_pattern;
+
+  // bool has_type;
+  std::unique_ptr<Type> type;
+
+  // bool has_init_expr;
+  std::unique_ptr<Expr> init_expr;
+
+  Location locus;
+
+public:
+  Type *inferedType;
+
+  // Returns whether let statement has outer attributes.
+  bool has_outer_attrs () const { return !outer_attrs.empty (); }
+
+  // Returns whether let statement has a given return type.
+  bool has_type () const { return type != nullptr; }
+
+  // Returns whether let statement has an initialisation expression.
+  bool has_init_expr () const { return init_expr != nullptr; }
+
+  std::string as_string () const override;
+
+  LetStmt (std::unique_ptr<Pattern> variables_pattern,
+	   std::unique_ptr<Expr> init_expr, std::unique_ptr<Type> type,
+	   std::vector<Attribute> outer_attrs, Location locus)
+    : outer_attrs (std::move (outer_attrs)),
+      variables_pattern (std::move (variables_pattern)),
+      type (std::move (type)), init_expr (std::move (init_expr)), locus (locus)
+  {}
+
+  // Copy constructor with clone
+  LetStmt (LetStmt const &other)
+    : outer_attrs (other.outer_attrs), locus (other.locus)
+  {
+    // guard to prevent null dereference (only required if error state)
+    if (other.variables_pattern != nullptr)
+      variables_pattern = other.variables_pattern->clone_pattern ();
+
+    // guard to prevent null dereference (always required)
+    if (other.init_expr != nullptr)
+      init_expr = other.init_expr->clone_expr ();
+    if (other.type != nullptr)
+      type = other.type->clone_type ();
+  }
+
+  // Overloaded assignment operator to clone
+  LetStmt &operator= (LetStmt const &other)
+  {
+    outer_attrs = other.outer_attrs;
+    locus = other.locus;
+
+    // guard to prevent null dereference (only required if error state)
+    if (other.variables_pattern != nullptr)
+      variables_pattern = other.variables_pattern->clone_pattern ();
+    else
+      variables_pattern = nullptr;
+
+    // guard to prevent null dereference (always required)
+    if (other.init_expr != nullptr)
+      init_expr = other.init_expr->clone_expr ();
+    else
+      init_expr = nullptr;
+    if (other.type != nullptr)
+      type = other.type->clone_type ();
+    else
+      type = nullptr;
+
+    return *this;
+  }
+
+  // move constructors
+  LetStmt (LetStmt &&other) = default;
+  LetStmt &operator= (LetStmt &&other) = default;
+
+  Location get_locus () const override final { return locus; }
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // Invalid if pattern is null, so base stripping on that.
+  void mark_for_strip () override { variables_pattern = nullptr; }
+  bool is_marked_for_strip () const override
+  {
+    return variables_pattern == nullptr;
+  }
+
+  // TODO: this mutable getter seems really dodgy. Think up better way.
+  std::vector<Attribute> &get_outer_attrs () { return outer_attrs; }
+  const std::vector<Attribute> &get_outer_attrs () const { return outer_attrs; }
+
+  // TODO: is this better? Or is a "vis_block" better?
+  std::unique_ptr<Expr> &get_init_expr ()
+  {
+    rust_assert (has_init_expr ());
+    return init_expr;
+  }
+
+  std::unique_ptr<Pattern> &get_pattern ()
+  {
+    rust_assert (variables_pattern != nullptr);
+    return variables_pattern;
+  }
+
+  std::unique_ptr<Type> &get_type ()
+  {
+    rust_assert (has_type ());
+    return type;
+  }
+
+  bool is_item () const override final { return false; }
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  LetStmt *clone_stmt_impl () const override { return new LetStmt (*this); }
+};
+
+/* Abstract base class for expression statements (statements containing an
+ * expression) */
+class ExprStmt : public Stmt
+{
+public:
+  enum ExprStmtType
+  {
+    WITH_BLOCK,
+    WITHOUT_BLOCK
+  };
+
+protected:
+  Location locus;
+
+public:
+  Location get_locus () const override final { return locus; }
+
+  bool is_item () const override final { return false; }
+
+  virtual ExprStmtType get_type () const = 0;
+
+protected:
+  ExprStmt (Location locus) : locus (locus) {}
+};
+
+/* Statement containing an expression without a block (or, due to technical
+ * difficulties, can only be guaranteed to hold an expression). */
+class ExprStmtWithoutBlock : public ExprStmt
+{
+  // TODO: ensure that this works
+  std::unique_ptr<ExprWithoutBlock> expr;
+  /* HACK: cannot ensure type safety of ExprWithoutBlock due to Pratt parsing,
+   * so have to store more general type of Expr. FIXME: fix this issue somehow
+   * or redesign AST. */
+  // std::unique_ptr<Expr> expr;
+
+public:
+  std::string as_string () const override;
+
+  ExprStmtWithoutBlock (std::unique_ptr<ExprWithoutBlock> expr, Location locus)
+    : ExprStmt (locus), expr (std::move (expr->to_stmt ()))
+  {}
+
+  /*ExprStmtWithoutBlock (std::unique_ptr<Expr> expr, Location locus)
+    : ExprStmt (locus), expr (std::move (expr))
+  {}*/
+
+  // Copy constructor with clone
+  ExprStmtWithoutBlock (ExprStmtWithoutBlock const &other) : ExprStmt (other)
+  {
+    // guard to prevent null dereference (only required if error state)
+    if (other.expr != nullptr)
+      expr = other.expr->clone_expr_without_block ();
+  }
+  /*ExprStmtWithoutBlock (ExprStmtWithoutBlock const &other)
+    : ExprStmt (other), expr (other.expr->clone_expr ())
+  {}*/
+
+  // Overloaded assignment operator to clone
+  ExprStmtWithoutBlock &operator= (ExprStmtWithoutBlock const &other)
+  {
+    ExprStmt::operator= (other);
+    // expr = other.expr->clone_expr ();
+
+    // guard to prevent null dereference (only required if error state)
+    if (other.expr != nullptr)
+      expr = other.expr->clone_expr_without_block ();
+    else
+      expr = nullptr;
+
+    return *this;
+  }
+
+  // move constructors
+  ExprStmtWithoutBlock (ExprStmtWithoutBlock &&other) = default;
+  ExprStmtWithoutBlock &operator= (ExprStmtWithoutBlock &&other) = default;
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // Invalid if expr is null, so base stripping on that.
+  void mark_for_strip () override { expr = nullptr; }
+  bool is_marked_for_strip () const override { return expr == nullptr; }
+
+  // TODO: is this better? Or is a "vis_block" better?
+  std::unique_ptr<ExprWithoutBlock> &get_expr ()
+  {
+    rust_assert (expr != nullptr);
+    return expr;
+  }
+
+  ExprStmtType get_type () const override
+  {
+    return ExprStmtType::WITHOUT_BLOCK;
+  };
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  ExprStmtWithoutBlock *clone_stmt_impl () const override
+  {
+    return new ExprStmtWithoutBlock (*this);
+  }
+};
+
+// Statement containing an expression with a block
+class ExprStmtWithBlock : public ExprStmt
+{
+  std::unique_ptr<ExprWithBlock> expr;
+  bool semicolon_followed;
+
+public:
+  std::string as_string () const override;
+
+  std::vector<LetStmt *> locals;
+
+  ExprStmtWithBlock (std::unique_ptr<ExprWithBlock> expr, Location locus,
+		     bool semicolon_followed)
+    : ExprStmt (locus), expr (std::move (expr)),
+      semicolon_followed (semicolon_followed)
+  {}
+
+  // Copy constructor with clone
+  ExprStmtWithBlock (ExprStmtWithBlock const &other) : ExprStmt (other)
+  {
+    // guard to prevent null dereference (only required if error state)
+    if (other.expr != nullptr)
+      expr = other.expr->clone_expr_with_block ();
+  }
+
+  // Overloaded assignment operator to clone
+  ExprStmtWithBlock &operator= (ExprStmtWithBlock const &other)
+  {
+    ExprStmt::operator= (other);
+
+    // guard to prevent null dereference (only required if error state)
+    if (other.expr != nullptr)
+      expr = other.expr->clone_expr_with_block ();
+    else
+      expr = nullptr;
+
+    return *this;
+  }
+
+  // move constructors
+  ExprStmtWithBlock (ExprStmtWithBlock &&other) = default;
+  ExprStmtWithBlock &operator= (ExprStmtWithBlock &&other) = default;
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // Invalid if expr is null, so base stripping on that.
+  void mark_for_strip () override { expr = nullptr; }
+  bool is_marked_for_strip () const override { return expr == nullptr; }
+
+  // TODO: is this better? Or is a "vis_block" better?
+  std::unique_ptr<ExprWithBlock> &get_expr ()
+  {
+    rust_assert (expr != nullptr);
+    return expr;
+  }
+
+  bool is_semicolon_followed () const { return semicolon_followed; }
+
+  ExprStmtType get_type () const override { return ExprStmtType::WITH_BLOCK; };
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  ExprStmtWithBlock *clone_stmt_impl () const override
+  {
+    return new ExprStmtWithBlock (*this);
+  }
+};
+
+} // namespace AST
+} // namespace Rust
+
+#endif
diff --git a/gcc/rust/ast/rust-type.h b/gcc/rust/ast/rust-type.h
new file mode 100644
index 0000000..7e9e07d
--- /dev/null
+++ b/gcc/rust/ast/rust-type.h
@@ -0,0 +1,962 @@
+// Copyright (C) 2020-2022 Free Software Foundation, Inc.
+
+// This file is part of GCC.
+
+// GCC is free software; you can redistribute it and/or modify it under
+// the terms of the GNU General Public License as published by the Free
+// Software Foundation; either version 3, or (at your option) any later
+// version.
+
+// GCC is distributed in the hope that it will be useful, but WITHOUT ANY
+// WARRANTY; without even the implied warranty of MERCHANTABILITY or
+// FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+// for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with GCC; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+#ifndef RUST_AST_TYPE_H
+#define RUST_AST_TYPE_H
+
+#include "rust-ast.h"
+#include "rust-path.h"
+
+namespace Rust {
+namespace AST {
+// definitions moved to rust-ast.h
+class TypeParamBound;
+class Lifetime;
+
+// A trait bound
+class TraitBound : public TypeParamBound
+{
+  bool in_parens;
+  bool opening_question_mark;
+
+  // bool has_for_lifetimes;
+  // LifetimeParams for_lifetimes;
+  std::vector<LifetimeParam> for_lifetimes; // inlined LifetimeParams
+
+  TypePath type_path;
+
+  Location locus;
+
+public:
+  // Returns whether trait bound has "for" lifetimes
+  bool has_for_lifetimes () const { return !for_lifetimes.empty (); }
+
+  TraitBound (TypePath type_path, Location locus, bool in_parens = false,
+	      bool opening_question_mark = false,
+	      std::vector<LifetimeParam> for_lifetimes
+	      = std::vector<LifetimeParam> ())
+    : TypeParamBound (Analysis::Mappings::get ()->get_next_node_id ()),
+      in_parens (in_parens), opening_question_mark (opening_question_mark),
+      for_lifetimes (std::move (for_lifetimes)),
+      type_path (std::move (type_path)), locus (locus)
+  {}
+
+  TraitBound (NodeId id, TypePath type_path, Location locus,
+	      bool in_parens = false, bool opening_question_mark = false,
+	      std::vector<LifetimeParam> for_lifetimes
+	      = std::vector<LifetimeParam> ())
+    : TypeParamBound (id), in_parens (in_parens),
+      opening_question_mark (opening_question_mark),
+      for_lifetimes (std::move (for_lifetimes)),
+      type_path (std::move (type_path)), locus (locus)
+  {}
+
+  std::string as_string () const override;
+
+  Location get_locus () const override final { return locus; }
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // TODO: this mutable getter seems kinda dodgy
+  TypePath &get_type_path () { return type_path; }
+  const TypePath &get_type_path () const { return type_path; }
+
+  bool is_in_parens () const { return in_parens; }
+  bool has_opening_question_mark () const { return opening_question_mark; }
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  TraitBound *clone_type_param_bound_impl () const override
+  {
+    return new TraitBound (node_id, type_path, locus, in_parens,
+			   opening_question_mark, for_lifetimes);
+  }
+};
+
+// definition moved to rust-ast.h
+class TypeNoBounds;
+
+// An impl trait? Poor reference material here.
+class ImplTraitType : public Type
+{
+  // TypeParamBounds type_param_bounds;
+  // inlined form
+  std::vector<std::unique_ptr<TypeParamBound> > type_param_bounds;
+
+  Location locus;
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  ImplTraitType *clone_type_impl () const override
+  {
+    return new ImplTraitType (*this);
+  }
+
+public:
+  ImplTraitType (
+    std::vector<std::unique_ptr<TypeParamBound> > type_param_bounds,
+    Location locus)
+    : type_param_bounds (std::move (type_param_bounds)), locus (locus)
+  {}
+
+  // copy constructor with vector clone
+  ImplTraitType (ImplTraitType const &other) : locus (other.locus)
+  {
+    type_param_bounds.reserve (other.type_param_bounds.size ());
+    for (const auto &e : other.type_param_bounds)
+      type_param_bounds.push_back (e->clone_type_param_bound ());
+  }
+
+  // overloaded assignment operator to clone
+  ImplTraitType &operator= (ImplTraitType const &other)
+  {
+    locus = other.locus;
+
+    type_param_bounds.reserve (other.type_param_bounds.size ());
+    for (const auto &e : other.type_param_bounds)
+      type_param_bounds.push_back (e->clone_type_param_bound ());
+
+    return *this;
+  }
+
+  // move constructors
+  ImplTraitType (ImplTraitType &&other) = default;
+  ImplTraitType &operator= (ImplTraitType &&other) = default;
+
+  std::string as_string () const override;
+
+  Location get_locus () const override final { return locus; }
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // TODO: mutable getter seems kinda dodgy
+  std::vector<std::unique_ptr<TypeParamBound> > &get_type_param_bounds ()
+  {
+    return type_param_bounds;
+  }
+  const std::vector<std::unique_ptr<TypeParamBound> > &
+  get_type_param_bounds () const
+  {
+    return type_param_bounds;
+  }
+};
+
+// An opaque value of another type that implements a set of traits
+class TraitObjectType : public Type
+{
+  bool has_dyn;
+  std::vector<std::unique_ptr<TypeParamBound> > type_param_bounds;
+  Location locus;
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  TraitObjectType *clone_type_impl () const override
+  {
+    return new TraitObjectType (*this);
+  }
+
+public:
+  TraitObjectType (
+    std::vector<std::unique_ptr<TypeParamBound> > type_param_bounds,
+    Location locus, bool is_dyn_dispatch)
+    : has_dyn (is_dyn_dispatch),
+      type_param_bounds (std::move (type_param_bounds)), locus (locus)
+  {}
+
+  // copy constructor with vector clone
+  TraitObjectType (TraitObjectType const &other)
+    : has_dyn (other.has_dyn), locus (other.locus)
+  {
+    type_param_bounds.reserve (other.type_param_bounds.size ());
+    for (const auto &e : other.type_param_bounds)
+      type_param_bounds.push_back (e->clone_type_param_bound ());
+  }
+
+  // overloaded assignment operator to clone
+  TraitObjectType &operator= (TraitObjectType const &other)
+  {
+    has_dyn = other.has_dyn;
+    locus = other.locus;
+    type_param_bounds.reserve (other.type_param_bounds.size ());
+    for (const auto &e : other.type_param_bounds)
+      type_param_bounds.push_back (e->clone_type_param_bound ());
+
+    return *this;
+  }
+
+  // move constructors
+  TraitObjectType (TraitObjectType &&other) = default;
+  TraitObjectType &operator= (TraitObjectType &&other) = default;
+
+  std::string as_string () const override;
+
+  Location get_locus () const override final { return locus; }
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  bool is_dyn () const { return has_dyn; }
+
+  // TODO: mutable getter seems kinda dodgy
+  std::vector<std::unique_ptr<TypeParamBound> > &get_type_param_bounds ()
+  {
+    return type_param_bounds;
+  }
+  const std::vector<std::unique_ptr<TypeParamBound> > &
+  get_type_param_bounds () const
+  {
+    return type_param_bounds;
+  }
+};
+
+// A type with parentheses around it, used to avoid ambiguity.
+class ParenthesisedType : public TypeNoBounds
+{
+  std::unique_ptr<Type> type_in_parens;
+  Location locus;
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  ParenthesisedType *clone_type_no_bounds_impl () const override
+  {
+    return new ParenthesisedType (*this);
+  }
+
+public:
+  // Constructor uses Type pointer for polymorphism
+  ParenthesisedType (std::unique_ptr<Type> type_inside_parens, Location locus)
+    : type_in_parens (std::move (type_inside_parens)), locus (locus)
+  {}
+
+  /* Copy constructor uses custom deep copy method for type to preserve
+   * polymorphism */
+  ParenthesisedType (ParenthesisedType const &other)
+    : type_in_parens (other.type_in_parens->clone_type ()), locus (other.locus)
+  {}
+
+  // overload assignment operator to use custom clone method
+  ParenthesisedType &operator= (ParenthesisedType const &other)
+  {
+    type_in_parens = other.type_in_parens->clone_type ();
+    locus = other.locus;
+    return *this;
+  }
+
+  // default move semantics
+  ParenthesisedType (ParenthesisedType &&other) = default;
+  ParenthesisedType &operator= (ParenthesisedType &&other) = default;
+
+  std::string as_string () const override
+  {
+    return "(" + type_in_parens->as_string () + ")";
+  }
+
+  // Creates a trait bound (clone of this one's trait bound) - HACK
+  TraitBound *to_trait_bound (bool) const override
+  {
+    /* NOTE: obviously it is unknown whether the internal type is a trait bound
+     * due to polymorphism, so just let the internal type handle it. As
+     * parenthesised type, it must be in parentheses. */
+    return type_in_parens->to_trait_bound (true);
+  }
+
+  Location get_locus () const override final { return locus; }
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // TODO: would a "vis_type" be better?
+  std::unique_ptr<Type> &get_type_in_parens ()
+  {
+    rust_assert (type_in_parens != nullptr);
+    return type_in_parens;
+  }
+};
+
+// Impl trait with a single bound? Poor reference material here.
+class ImplTraitTypeOneBound : public TypeNoBounds
+{
+  TraitBound trait_bound;
+  Location locus;
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  ImplTraitTypeOneBound *clone_type_no_bounds_impl () const override
+  {
+    return new ImplTraitTypeOneBound (*this);
+  }
+
+public:
+  ImplTraitTypeOneBound (TraitBound trait_bound, Location locus)
+    : trait_bound (std::move (trait_bound)), locus (locus)
+  {}
+
+  std::string as_string () const override;
+
+  Location get_locus () const override final { return locus; }
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // TODO: would a "vis_type" be better?
+  TraitBound &get_trait_bound ()
+  {
+    // TODO: check to ensure invariants are met?
+    return trait_bound;
+  }
+};
+
+/* A trait object with a single trait bound. The "trait bound" is really just
+ * the trait. Basically like using an interface as a type in an OOP language. */
+class TraitObjectTypeOneBound : public TypeNoBounds
+{
+  bool has_dyn;
+  TraitBound trait_bound;
+  Location locus;
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  TraitObjectTypeOneBound *clone_type_no_bounds_impl () const override
+  {
+    return new TraitObjectTypeOneBound (*this);
+  }
+
+public:
+  TraitObjectTypeOneBound (TraitBound trait_bound, Location locus,
+			   bool is_dyn_dispatch = false)
+    : has_dyn (is_dyn_dispatch), trait_bound (std::move (trait_bound)),
+      locus (locus)
+  {}
+
+  std::string as_string () const override;
+
+  // Creates a trait bound (clone of this one's trait bound) - HACK
+  TraitBound *to_trait_bound (bool) const override
+  {
+    /* NOTE: this assumes there is no dynamic dispatch specified- if there was,
+     * this cloning would not be required as parsing is unambiguous. */
+    return new TraitBound (trait_bound);
+  }
+
+  Location get_locus () const override final { return locus; }
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // TODO: would a "vis_type" be better?
+  TraitBound &get_trait_bound ()
+  {
+    // TODO: check to ensure invariants are met?
+    return trait_bound;
+  }
+
+  bool is_dyn () const { return has_dyn; }
+};
+
+class TypePath; // definition moved to "rust-path.h"
+
+/* A type consisting of the "product" of others (the tuple's elements) in a
+ * specific order */
+class TupleType : public TypeNoBounds
+{
+  std::vector<std::unique_ptr<Type> > elems;
+  Location locus;
+
+public:
+  // Returns whether the tuple type is the unit type, i.e. has no elements.
+  bool is_unit_type () const { return elems.empty (); }
+
+  TupleType (std::vector<std::unique_ptr<Type> > elems, Location locus)
+    : elems (std::move (elems)), locus (locus)
+  {}
+
+  // copy constructor with vector clone
+  TupleType (TupleType const &other) : locus (other.locus)
+  {
+    elems.reserve (other.elems.size ());
+    for (const auto &e : other.elems)
+      elems.push_back (e->clone_type ());
+  }
+
+  // overloaded assignment operator to clone
+  TupleType &operator= (TupleType const &other)
+  {
+    locus = other.locus;
+
+    elems.reserve (other.elems.size ());
+    for (const auto &e : other.elems)
+      elems.push_back (e->clone_type ());
+
+    return *this;
+  }
+
+  // move constructors
+  TupleType (TupleType &&other) = default;
+  TupleType &operator= (TupleType &&other) = default;
+
+  std::string as_string () const override;
+
+  Location get_locus () const override final { return locus; }
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // TODO: mutable getter seems kinda dodgy
+  std::vector<std::unique_ptr<Type> > &get_elems () { return elems; }
+  const std::vector<std::unique_ptr<Type> > &get_elems () const
+  {
+    return elems;
+  }
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  TupleType *clone_type_no_bounds_impl () const override
+  {
+    return new TupleType (*this);
+  }
+};
+
+/* A type with no values, representing the result of computations that never
+ * complete. Expressions of NeverType can be coerced into any other types.
+ * Represented as "!". */
+class NeverType : public TypeNoBounds
+{
+  Location locus;
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  NeverType *clone_type_no_bounds_impl () const override
+  {
+    return new NeverType (*this);
+  }
+
+public:
+  NeverType (Location locus) : locus (locus) {}
+
+  std::string as_string () const override { return "! (never type)"; }
+
+  Location get_locus () const override final { return locus; }
+
+  void accept_vis (ASTVisitor &vis) override;
+};
+
+// A type consisting of a pointer without safety or liveness guarantees
+class RawPointerType : public TypeNoBounds
+{
+public:
+  enum PointerType
+  {
+    MUT,
+    CONST
+  };
+
+private:
+  PointerType pointer_type;
+  std::unique_ptr<TypeNoBounds> type;
+  Location locus;
+
+public:
+  // Returns whether the pointer is mutable or constant.
+  PointerType get_pointer_type () const { return pointer_type; }
+
+  // Constructor requires pointer for polymorphism reasons
+  RawPointerType (PointerType pointer_type,
+		  std::unique_ptr<TypeNoBounds> type_no_bounds, Location locus)
+    : pointer_type (pointer_type), type (std::move (type_no_bounds)),
+      locus (locus)
+  {}
+
+  // Copy constructor calls custom polymorphic clone function
+  RawPointerType (RawPointerType const &other)
+    : pointer_type (other.pointer_type),
+      type (other.type->clone_type_no_bounds ()), locus (other.locus)
+  {}
+
+  // overload assignment operator to use custom clone method
+  RawPointerType &operator= (RawPointerType const &other)
+  {
+    pointer_type = other.pointer_type;
+    type = other.type->clone_type_no_bounds ();
+    locus = other.locus;
+    return *this;
+  }
+
+  // default move semantics
+  RawPointerType (RawPointerType &&other) = default;
+  RawPointerType &operator= (RawPointerType &&other) = default;
+
+  std::string as_string () const override;
+
+  Location get_locus () const override final { return locus; }
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // TODO: would a "vis_type" be better?
+  std::unique_ptr<TypeNoBounds> &get_type_pointed_to ()
+  {
+    rust_assert (type != nullptr);
+    return type;
+  }
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  RawPointerType *clone_type_no_bounds_impl () const override
+  {
+    return new RawPointerType (*this);
+  }
+};
+
+// A type pointing to memory owned by another value
+class ReferenceType : public TypeNoBounds
+{
+  // bool has_lifetime; // TODO: handle in lifetime or something?
+  Lifetime lifetime;
+
+  bool has_mut;
+  std::unique_ptr<TypeNoBounds> type;
+  Location locus;
+
+public:
+  // Returns whether the reference is mutable or immutable.
+  bool is_mut () const { return has_mut; }
+
+  // Returns whether the reference has a lifetime.
+  bool has_lifetime () const { return !lifetime.is_error (); }
+
+  // Constructor
+  ReferenceType (bool is_mut, std::unique_ptr<TypeNoBounds> type_no_bounds,
+		 Location locus, Lifetime lifetime = Lifetime::error ())
+    : lifetime (std::move (lifetime)), has_mut (is_mut),
+      type (std::move (type_no_bounds)), locus (locus)
+  {}
+
+  // Copy constructor with custom clone method
+  ReferenceType (ReferenceType const &other)
+    : lifetime (other.lifetime), has_mut (other.has_mut),
+      type (other.type->clone_type_no_bounds ()), locus (other.locus)
+  {}
+
+  // Operator overload assignment operator to custom clone the unique pointer
+  ReferenceType &operator= (ReferenceType const &other)
+  {
+    lifetime = other.lifetime;
+    has_mut = other.has_mut;
+    type = other.type->clone_type_no_bounds ();
+    locus = other.locus;
+
+    return *this;
+  }
+
+  // move constructors
+  ReferenceType (ReferenceType &&other) = default;
+  ReferenceType &operator= (ReferenceType &&other) = default;
+
+  std::string as_string () const override;
+
+  Location get_locus () const override final { return locus; }
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // TODO: would a "vis_type" be better?
+  std::unique_ptr<TypeNoBounds> &get_type_referenced ()
+  {
+    rust_assert (type != nullptr);
+    return type;
+  }
+
+  bool get_has_mut () const { return has_mut; }
+
+  Lifetime &get_lifetime () { return lifetime; }
+
+  std::unique_ptr<TypeNoBounds> &get_base_type () { return type; }
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  ReferenceType *clone_type_no_bounds_impl () const override
+  {
+    return new ReferenceType (*this);
+  }
+};
+
+// A fixed-size sequence of elements of a specified type
+class ArrayType : public TypeNoBounds
+{
+  std::unique_ptr<Type> elem_type;
+  std::unique_ptr<Expr> size;
+  Location locus;
+
+public:
+  // Constructor requires pointers for polymorphism
+  ArrayType (std::unique_ptr<Type> type, std::unique_ptr<Expr> array_size,
+	     Location locus)
+    : elem_type (std::move (type)), size (std::move (array_size)), locus (locus)
+  {}
+
+  // Copy constructor requires deep copies of both unique pointers
+  ArrayType (ArrayType const &other)
+    : elem_type (other.elem_type->clone_type ()),
+      size (other.size->clone_expr ()), locus (other.locus)
+  {}
+
+  // Overload assignment operator to deep copy pointers
+  ArrayType &operator= (ArrayType const &other)
+  {
+    elem_type = other.elem_type->clone_type ();
+    size = other.size->clone_expr ();
+    locus = other.locus;
+    return *this;
+  }
+
+  // move constructors
+  ArrayType (ArrayType &&other) = default;
+  ArrayType &operator= (ArrayType &&other) = default;
+
+  std::string as_string () const override;
+
+  Location get_locus () const override final { return locus; }
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // TODO: would a "vis_type" be better?
+  std::unique_ptr<Type> &get_elem_type ()
+  {
+    rust_assert (elem_type != nullptr);
+    return elem_type;
+  }
+
+  // TODO: would a "vis_expr" be better?
+  std::unique_ptr<Expr> &get_size_expr ()
+  {
+    rust_assert (size != nullptr);
+    return size;
+  }
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  ArrayType *clone_type_no_bounds_impl () const override
+  {
+    return new ArrayType (*this);
+  }
+};
+
+/* A dynamically-sized type representing a "view" into a sequence of elements of
+ * a type */
+class SliceType : public TypeNoBounds
+{
+  std::unique_ptr<Type> elem_type;
+  Location locus;
+
+public:
+  // Constructor requires pointer for polymorphism
+  SliceType (std::unique_ptr<Type> type, Location locus)
+    : elem_type (std::move (type)), locus (locus)
+  {}
+
+  // Copy constructor requires deep copy of Type smart pointer
+  SliceType (SliceType const &other)
+    : elem_type (other.elem_type->clone_type ()), locus (other.locus)
+  {}
+
+  // Overload assignment operator to deep copy
+  SliceType &operator= (SliceType const &other)
+  {
+    elem_type = other.elem_type->clone_type ();
+    locus = other.locus;
+
+    return *this;
+  }
+
+  // move constructors
+  SliceType (SliceType &&other) = default;
+  SliceType &operator= (SliceType &&other) = default;
+
+  std::string as_string () const override;
+
+  Location get_locus () const override final { return locus; }
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // TODO: would a "vis_type" be better?
+  std::unique_ptr<Type> &get_elem_type ()
+  {
+    rust_assert (elem_type != nullptr);
+    return elem_type;
+  }
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  SliceType *clone_type_no_bounds_impl () const override
+  {
+    return new SliceType (*this);
+  }
+};
+
+/* Type used in generic arguments to explicitly request type inference (wildcard
+ * pattern) */
+class InferredType : public TypeNoBounds
+{
+  Location locus;
+
+  // e.g. Vec<_> = whatever
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  InferredType *clone_type_no_bounds_impl () const override
+  {
+    return new InferredType (*this);
+  }
+
+public:
+  InferredType (Location locus) : locus (locus) {}
+
+  std::string as_string () const override;
+
+  Location get_locus () const override final { return locus; }
+
+  void accept_vis (ASTVisitor &vis) override;
+};
+
+class QualifiedPathInType; // definition moved to "rust-path.h"
+
+// A possibly named param used in a BaseFunctionType
+struct MaybeNamedParam
+{
+public:
+  enum ParamKind
+  {
+    UNNAMED,
+    IDENTIFIER,
+    WILDCARD
+  };
+
+private:
+  std::vector<Attribute> outer_attrs;
+
+  std::unique_ptr<Type> param_type;
+
+  ParamKind param_kind;
+  Identifier name; // technically, can be an identifier or '_'
+
+  Location locus;
+
+public:
+  MaybeNamedParam (Identifier name, ParamKind param_kind,
+		   std::unique_ptr<Type> param_type,
+		   std::vector<Attribute> outer_attrs, Location locus)
+    : outer_attrs (std::move (outer_attrs)),
+      param_type (std::move (param_type)), param_kind (param_kind),
+      name (std::move (name)), locus (locus)
+  {}
+
+  // Copy constructor with clone
+  MaybeNamedParam (MaybeNamedParam const &other)
+    : outer_attrs (other.outer_attrs), param_kind (other.param_kind),
+      name (other.name), locus (other.locus)
+  {
+    // guard to prevent null dereference
+    if (other.param_type != nullptr)
+      param_type = other.param_type->clone_type ();
+  }
+
+  ~MaybeNamedParam () = default;
+
+  // Overloaded assignment operator with clone
+  MaybeNamedParam &operator= (MaybeNamedParam const &other)
+  {
+    outer_attrs = other.outer_attrs;
+    name = other.name;
+    param_kind = other.param_kind;
+    locus = other.locus;
+
+    // guard to prevent null dereference
+    if (other.param_type != nullptr)
+      param_type = other.param_type->clone_type ();
+    else
+      param_type = nullptr;
+
+    return *this;
+  }
+
+  // move constructors
+  MaybeNamedParam (MaybeNamedParam &&other) = default;
+  MaybeNamedParam &operator= (MaybeNamedParam &&other) = default;
+
+  std::string as_string () const;
+
+  // Returns whether the param is in an error state.
+  bool is_error () const { return param_type == nullptr; }
+
+  // Creates an error state param.
+  static MaybeNamedParam create_error ()
+  {
+    return MaybeNamedParam ("", UNNAMED, nullptr, {}, Location ());
+  }
+
+  Location get_locus () const { return locus; }
+
+  // TODO: this mutable getter seems really dodgy. Think up better way.
+  std::vector<Attribute> &get_outer_attrs () { return outer_attrs; }
+  const std::vector<Attribute> &get_outer_attrs () const { return outer_attrs; }
+
+  // TODO: would a "vis_type" be better?
+  std::unique_ptr<Type> &get_type ()
+  {
+    rust_assert (param_type != nullptr);
+    return param_type;
+  }
+
+  ParamKind get_param_kind () const { return param_kind; }
+
+  Identifier get_name () const { return name; }
+};
+
+/* A function pointer type - can be created via coercion from function items and
+ * non- capturing closures. */
+class BareFunctionType : public TypeNoBounds
+{
+  // bool has_for_lifetimes;
+  // ForLifetimes for_lifetimes;
+  std::vector<LifetimeParam> for_lifetimes; // inlined version
+
+  FunctionQualifiers function_qualifiers;
+  std::vector<MaybeNamedParam> params;
+  bool is_variadic;
+  std::vector<Attribute> variadic_attrs;
+
+  // bool has_return_type;
+  // BareFunctionReturnType return_type;
+  std::unique_ptr<TypeNoBounds> return_type; // inlined version
+
+  Location locus;
+
+public:
+  // Whether a return type is defined with the function.
+  bool has_return_type () const { return return_type != nullptr; }
+
+  // Whether the function has ForLifetimes.
+  bool has_for_lifetimes () const { return !for_lifetimes.empty (); }
+
+  BareFunctionType (std::vector<LifetimeParam> lifetime_params,
+		    FunctionQualifiers qualifiers,
+		    std::vector<MaybeNamedParam> named_params, bool is_variadic,
+		    std::vector<Attribute> variadic_attrs,
+		    std::unique_ptr<TypeNoBounds> type, Location locus)
+    : for_lifetimes (std::move (lifetime_params)),
+      function_qualifiers (std::move (qualifiers)),
+      params (std::move (named_params)), is_variadic (is_variadic),
+      variadic_attrs (std::move (variadic_attrs)),
+      return_type (std::move (type)), locus (locus)
+  {
+    if (!variadic_attrs.empty ())
+      is_variadic = true;
+  }
+
+  // Copy constructor with clone
+  BareFunctionType (BareFunctionType const &other)
+    : for_lifetimes (other.for_lifetimes),
+      function_qualifiers (other.function_qualifiers), params (other.params),
+      is_variadic (other.is_variadic), variadic_attrs (other.variadic_attrs),
+      locus (other.locus)
+  {
+    // guard to prevent null dereference
+    if (other.return_type != nullptr)
+      return_type = other.return_type->clone_type_no_bounds ();
+  }
+
+  // Overload assignment operator to deep copy
+  BareFunctionType &operator= (BareFunctionType const &other)
+  {
+    for_lifetimes = other.for_lifetimes;
+    function_qualifiers = other.function_qualifiers;
+    params = other.params;
+    is_variadic = other.is_variadic;
+    variadic_attrs = other.variadic_attrs;
+    locus = other.locus;
+
+    // guard to prevent null dereference
+    if (other.return_type != nullptr)
+      return_type = other.return_type->clone_type_no_bounds ();
+    else
+      return_type = nullptr;
+
+    return *this;
+  }
+
+  // move constructors
+  BareFunctionType (BareFunctionType &&other) = default;
+  BareFunctionType &operator= (BareFunctionType &&other) = default;
+
+  std::string as_string () const override;
+
+  Location get_locus () const override final { return locus; }
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // TODO: this mutable getter seems kinda dodgy
+  std::vector<MaybeNamedParam> &get_function_params () { return params; }
+  const std::vector<MaybeNamedParam> &get_function_params () const
+  {
+    return params;
+  }
+
+  // TODO: would a "vis_type" be better?
+  std::unique_ptr<TypeNoBounds> &get_return_type ()
+  {
+    rust_assert (has_return_type ());
+    return return_type;
+  }
+
+  FunctionQualifiers get_function_qualifiers () { return function_qualifiers; }
+
+protected:
+  /* Use covariance to implement clone function as returning this object rather
+   * than base */
+  BareFunctionType *clone_type_no_bounds_impl () const override
+  {
+    return new BareFunctionType (*this);
+  }
+};
+
+// Forward decl - defined in rust-macro.h
+class MacroInvocation;
+
+/* TODO: possible types
+ * struct type?
+ * "enum" (tagged union) type?
+ * C-like union type?
+ * function item type?
+ * closure expression types?
+ * primitive types (bool, int, float, char, str (the slice))
+ * Although supposedly TypePaths are used to reference these types (including
+ * primitives) */
+
+/* FIXME: Incomplete spec references:
+ *  anonymous type parameters, aka "impl Trait in argument position" - impl then
+ * trait bounds abstract return types, aka "impl Trait in return position" -
+ * impl then trait bounds */
+} // namespace AST
+} // namespace Rust
+
+#endif