gccrs: Add definitions of Rust Items in AST data structures

This adds the proper definitions of our AST Item nodes.

	gcc/rust/
	* ast/rust-item.h: New.

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

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

1 files changed, 4382 insertions, 0 deletions

diff --git a/gcc/rust/ast/rust-item.h b/gcc/rust/ast/rust-item.h
new file mode 100644
index 0000000..f1b3522
--- /dev/null
+++ b/gcc/rust/ast/rust-item.h
@@ -0,0 +1,4382 @@
+// 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_ITEM_H
+#define RUST_AST_ITEM_H
+
+#include "rust-ast.h"
+#include "rust-path.h"
+#include "rust-common.h"
+
+namespace Rust {
+namespace AST {
+// forward decls
+class BlockExpr;
+class TypePath;
+
+// TODO: inline?
+/*struct AbiName {
+    std::string abi_name;
+    // Technically is meant to be STRING_LITERAL
+
+  public:
+    // Returns whether abi name is empty, i.e. doesn't exist.
+    bool is_empty() const {
+	return abi_name.empty();
+    }
+
+    AbiName(std::string name) : abi_name(std::move(name)) {}
+
+    // Empty AbiName constructor
+    AbiName() {}
+};*/
+
+// A type generic parameter (as opposed to a lifetime generic parameter)
+class TypeParam : public GenericParam
+{
+  // bool has_outer_attribute;
+  // std::unique_ptr<Attribute> outer_attr;
+  Attribute outer_attr;
+
+  Identifier type_representation;
+
+  // bool has_type_param_bounds;
+  // TypeParamBounds type_param_bounds;
+  std::vector<std::unique_ptr<TypeParamBound>>
+    type_param_bounds; // inlined form
+
+  // bool has_type;
+  std::unique_ptr<Type> type;
+
+  Location locus;
+
+public:
+  Identifier get_type_representation () const { return type_representation; }
+
+  // Returns whether the type of the type param has been specified.
+  bool has_type () const { return type != nullptr; }
+
+  // Returns whether the type param has type param bounds.
+  bool has_type_param_bounds () const { return !type_param_bounds.empty (); }
+
+  // Returns whether the type param has an outer attribute.
+  bool has_outer_attribute () const { return !outer_attr.is_empty (); }
+
+  TypeParam (Identifier type_representation, Location locus = Location (),
+	     std::vector<std::unique_ptr<TypeParamBound>> type_param_bounds
+	     = std::vector<std::unique_ptr<TypeParamBound>> (),
+	     std::unique_ptr<Type> type = nullptr,
+	     Attribute outer_attr = Attribute::create_empty ())
+    : GenericParam (Analysis::Mappings::get ()->get_next_node_id ()),
+      outer_attr (std::move (outer_attr)),
+      type_representation (std::move (type_representation)),
+      type_param_bounds (std::move (type_param_bounds)),
+      type (std::move (type)), locus (locus)
+  {}
+
+  // Copy constructor uses clone
+  TypeParam (TypeParam const &other)
+    : GenericParam (other.node_id), outer_attr (other.outer_attr),
+      type_representation (other.type_representation), locus (other.locus)
+  {
+    // guard to prevent null pointer dereference
+    if (other.type != nullptr)
+      type = other.type->clone_type ();
+
+    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
+  TypeParam &operator= (TypeParam const &other)
+  {
+    type_representation = other.type_representation;
+    outer_attr = other.outer_attr;
+    locus = other.locus;
+    node_id = other.node_id;
+
+    // guard to prevent null pointer dereference
+    if (other.type != nullptr)
+      type = other.type->clone_type ();
+    else
+      type = nullptr;
+
+    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
+  TypeParam (TypeParam &&other) = default;
+  TypeParam &operator= (TypeParam &&other) = default;
+
+  std::string as_string () const override;
+
+  Location get_locus () const override final { return locus; }
+
+  Kind get_kind () const override final { return Kind::Type; }
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // TODO: is this better? Or is a "vis_block" better?
+  std::unique_ptr<Type> &get_type ()
+  {
+    rust_assert (type != nullptr);
+    return type;
+  }
+
+  // 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;
+  }
+
+protected:
+  // Clone function implementation as virtual method
+  TypeParam *clone_generic_param_impl () const override
+  {
+    return new TypeParam (*this);
+  }
+};
+
+/* "where" clause item base. Abstract - use LifetimeWhereClauseItem,
+ * TypeBoundWhereClauseItem */
+class WhereClauseItem
+{
+public:
+  virtual ~WhereClauseItem () {}
+
+  // Unique pointer custom clone function
+  std::unique_ptr<WhereClauseItem> clone_where_clause_item () const
+  {
+    return std::unique_ptr<WhereClauseItem> (clone_where_clause_item_impl ());
+  }
+
+  virtual std::string as_string () const = 0;
+
+  virtual void accept_vis (ASTVisitor &vis) = 0;
+
+  virtual NodeId get_node_id () const = 0;
+
+protected:
+  // Clone function implementation as pure virtual method
+  virtual WhereClauseItem *clone_where_clause_item_impl () const = 0;
+};
+
+// A lifetime where clause item
+class LifetimeWhereClauseItem : public WhereClauseItem
+{
+  Lifetime lifetime;
+  std::vector<Lifetime> lifetime_bounds;
+  Location locus;
+  NodeId node_id;
+
+public:
+  LifetimeWhereClauseItem (Lifetime lifetime,
+			   std::vector<Lifetime> lifetime_bounds,
+			   Location locus)
+    : lifetime (std::move (lifetime)),
+      lifetime_bounds (std::move (lifetime_bounds)), locus (locus),
+      node_id (Analysis::Mappings::get ()->get_next_node_id ())
+  {}
+
+  std::string as_string () const override;
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  NodeId get_node_id () const override final { return node_id; }
+
+  Lifetime &get_lifetime () { return lifetime; }
+
+  std::vector<Lifetime> &get_lifetime_bounds () { return lifetime_bounds; }
+
+  Location get_locus () const { return locus; }
+
+protected:
+  // Clone function implementation as (not pure) virtual method
+  LifetimeWhereClauseItem *clone_where_clause_item_impl () const override
+  {
+    return new LifetimeWhereClauseItem (*this);
+  }
+};
+
+// A type bound where clause item
+class TypeBoundWhereClauseItem : public WhereClauseItem
+{
+  std::vector<LifetimeParam> for_lifetimes;
+  std::unique_ptr<Type> bound_type;
+  std::vector<std::unique_ptr<TypeParamBound>> type_param_bounds;
+  NodeId node_id;
+  Location locus;
+
+public:
+  // Returns whether the item has ForLifetimes
+  bool has_for_lifetimes () const { return !for_lifetimes.empty (); }
+
+  // Returns whether the item has type param bounds
+  bool has_type_param_bounds () const { return !type_param_bounds.empty (); }
+
+  TypeBoundWhereClauseItem (
+    std::vector<LifetimeParam> for_lifetimes, std::unique_ptr<Type> bound_type,
+    std::vector<std::unique_ptr<TypeParamBound>> type_param_bounds,
+    Location locus)
+    : for_lifetimes (std::move (for_lifetimes)),
+      bound_type (std::move (bound_type)),
+      type_param_bounds (std::move (type_param_bounds)),
+      node_id (Analysis::Mappings::get ()->get_next_node_id ()), locus (locus)
+  {}
+
+  // Copy constructor requires clone
+  TypeBoundWhereClauseItem (TypeBoundWhereClauseItem const &other)
+    : for_lifetimes (other.for_lifetimes),
+      bound_type (other.bound_type->clone_type ())
+  {
+    node_id = other.node_id;
+    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 ());
+  }
+
+  // Overload assignment operator to clone
+  TypeBoundWhereClauseItem &operator= (TypeBoundWhereClauseItem const &other)
+  {
+    node_id = other.node_id;
+    for_lifetimes = other.for_lifetimes;
+    bound_type = other.bound_type->clone_type ();
+    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
+  TypeBoundWhereClauseItem (TypeBoundWhereClauseItem &&other) = default;
+  TypeBoundWhereClauseItem &operator= (TypeBoundWhereClauseItem &&other)
+    = default;
+
+  std::string as_string () const override;
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  std::unique_ptr<Type> &get_type ()
+  {
+    rust_assert (bound_type != nullptr);
+    return bound_type;
+  }
+
+  // TODO: this mutable getter seems really dodgy. Think up better way.
+  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;
+  }
+
+  NodeId get_node_id () const override final { return node_id; }
+
+  Location get_locus () const { return locus; }
+
+protected:
+  // Clone function implementation as (not pure) virtual method
+  TypeBoundWhereClauseItem *clone_where_clause_item_impl () const override
+  {
+    return new TypeBoundWhereClauseItem (*this);
+  }
+};
+
+// A where clause
+struct WhereClause
+{
+private:
+  std::vector<std::unique_ptr<WhereClauseItem>> where_clause_items;
+  NodeId node_id;
+
+public:
+  WhereClause (std::vector<std::unique_ptr<WhereClauseItem>> where_clause_items)
+    : where_clause_items (std::move (where_clause_items)),
+      node_id (Analysis::Mappings::get ()->get_next_node_id ())
+  {}
+
+  // copy constructor with vector clone
+  WhereClause (WhereClause const &other)
+  {
+    node_id = other.node_id;
+    where_clause_items.reserve (other.where_clause_items.size ());
+    for (const auto &e : other.where_clause_items)
+      where_clause_items.push_back (e->clone_where_clause_item ());
+  }
+
+  // overloaded assignment operator with vector clone
+  WhereClause &operator= (WhereClause const &other)
+  {
+    node_id = other.node_id;
+    where_clause_items.reserve (other.where_clause_items.size ());
+    for (const auto &e : other.where_clause_items)
+      where_clause_items.push_back (e->clone_where_clause_item ());
+
+    return *this;
+  }
+
+  // move constructors
+  WhereClause (WhereClause &&other) = default;
+  WhereClause &operator= (WhereClause &&other) = default;
+
+  // Creates a WhereClause with no items.
+  static WhereClause create_empty ()
+  {
+    return WhereClause (std::vector<std::unique_ptr<WhereClauseItem>> ());
+  }
+
+  // Returns whether the WhereClause has no items.
+  bool is_empty () const { return where_clause_items.empty (); }
+
+  std::string as_string () const;
+
+  NodeId get_node_id () const { return node_id; }
+
+  // TODO: this mutable getter seems kinda dodgy
+  std::vector<std::unique_ptr<WhereClauseItem>> &get_items ()
+  {
+    return where_clause_items;
+  }
+  const std::vector<std::unique_ptr<WhereClauseItem>> &get_items () const
+  {
+    return where_clause_items;
+  }
+};
+
+// A self parameter in a method
+struct SelfParam
+{
+private:
+  bool has_ref;
+  bool is_mut;
+  // bool has_lifetime; // only possible if also ref
+  Lifetime lifetime;
+
+  // bool has_type; // only possible if not ref
+  std::unique_ptr<Type> type;
+
+  NodeId node_id;
+
+  Location locus;
+
+  // Unrestricted constructor used for error state
+  SelfParam (Lifetime lifetime, bool has_ref, bool is_mut, Type *type)
+    : has_ref (has_ref), is_mut (is_mut), lifetime (std::move (lifetime)),
+      type (type), node_id (Analysis::Mappings::get ()->get_next_node_id ())
+  {}
+  // this is ok as no outside classes can ever call this
+
+  // TODO: self param can have outer attributes
+
+public:
+  // Returns whether the self-param has a type field.
+  bool has_type () const { return type != nullptr; }
+
+  // Returns whether the self-param has a valid lifetime.
+  bool has_lifetime () const { return !lifetime.is_error (); }
+
+  // Returns whether the self-param is in an error state.
+  bool is_error () const
+  {
+    return (has_type () && has_lifetime ()) || (has_lifetime () && !has_ref);
+    // not having either is not an error
+  }
+
+  // Creates an error state self-param.
+  static SelfParam create_error ()
+  {
+    // cannot have no ref but have a lifetime at the same time
+    return SelfParam (Lifetime (Lifetime::STATIC), false, false, nullptr);
+  }
+
+  // Type-based self parameter (not ref, no lifetime)
+  SelfParam (std::unique_ptr<Type> type, bool is_mut, Location locus)
+    : has_ref (false), is_mut (is_mut), lifetime (Lifetime::error ()),
+      type (std::move (type)),
+      node_id (Analysis::Mappings::get ()->get_next_node_id ()), locus (locus)
+  {}
+
+  // Lifetime-based self parameter (is ref, no type)
+  SelfParam (Lifetime lifetime, bool is_mut, Location locus)
+    : has_ref (true), is_mut (is_mut), lifetime (std::move (lifetime)),
+      node_id (Analysis::Mappings::get ()->get_next_node_id ()), locus (locus)
+  {}
+
+  // Copy constructor requires clone
+  SelfParam (SelfParam const &other)
+    : has_ref (other.has_ref), is_mut (other.is_mut), lifetime (other.lifetime),
+      node_id (Analysis::Mappings::get ()->get_next_node_id ()),
+      locus (other.locus)
+  {
+    node_id = other.node_id;
+    if (other.type != nullptr)
+      type = other.type->clone_type ();
+  }
+
+  // Overload assignment operator to use clone
+  SelfParam &operator= (SelfParam const &other)
+  {
+    is_mut = other.is_mut;
+    has_ref = other.has_ref;
+    lifetime = other.lifetime;
+    locus = other.locus;
+    node_id = other.node_id;
+
+    if (other.type != nullptr)
+      type = other.type->clone_type ();
+    else
+      type = nullptr;
+
+    return *this;
+  }
+
+  // move constructors
+  SelfParam (SelfParam &&other) = default;
+  SelfParam &operator= (SelfParam &&other) = default;
+
+  std::string as_string () const;
+
+  Location get_locus () const { return locus; }
+
+  bool get_has_ref () const { return has_ref; };
+  bool get_is_mut () const { return is_mut; }
+
+  Lifetime get_lifetime () const { return lifetime; }
+
+  NodeId get_node_id () const { return node_id; }
+
+  // TODO: is this better? Or is a "vis_block" better?
+  std::unique_ptr<Type> &get_type ()
+  {
+    rust_assert (has_type ());
+    return type;
+  }
+};
+
+// Qualifiers for function, i.e. const, unsafe, extern etc.
+struct FunctionQualifiers
+{
+private:
+  AsyncConstStatus const_status;
+  bool has_unsafe;
+  bool has_extern;
+  std::string extern_abi;
+  Location locus;
+
+public:
+  FunctionQualifiers (Location locus, AsyncConstStatus const_status,
+		      bool has_unsafe, bool has_extern = false,
+		      std::string extern_abi = std::string ())
+    : const_status (const_status), has_unsafe (has_unsafe),
+      has_extern (has_extern), extern_abi (std::move (extern_abi)),
+      locus (locus)
+  {
+    if (!this->extern_abi.empty ())
+      {
+	// having extern is required; not having it is an implementation error
+	rust_assert (has_extern);
+      }
+  }
+
+  std::string as_string () const;
+
+  AsyncConstStatus get_const_status () const { return const_status; }
+  bool is_unsafe () const { return has_unsafe; }
+  bool is_extern () const { return has_extern; }
+  std::string get_extern_abi () const { return extern_abi; }
+  bool has_abi () const { return !extern_abi.empty (); }
+
+  Location get_locus () const { return locus; }
+};
+
+// A function parameter
+struct FunctionParam
+{
+private:
+  std::vector<Attribute> outer_attrs;
+  Location locus;
+  std::unique_ptr<Pattern> param_name;
+  std::unique_ptr<Type> type;
+
+public:
+  FunctionParam (std::unique_ptr<Pattern> param_name,
+		 std::unique_ptr<Type> param_type,
+		 std::vector<Attribute> outer_attrs, Location locus)
+    : outer_attrs (std::move (outer_attrs)), locus (locus),
+      param_name (std::move (param_name)), type (std::move (param_type)),
+      node_id (Analysis::Mappings::get ()->get_next_node_id ())
+  {}
+
+  // Copy constructor uses clone
+  FunctionParam (FunctionParam const &other)
+    : locus (other.locus), node_id (other.node_id)
+  {
+    // guard to prevent nullptr dereference
+    if (other.param_name != nullptr)
+      param_name = other.param_name->clone_pattern ();
+    if (other.type != nullptr)
+      type = other.type->clone_type ();
+  }
+
+  // Overload assignment operator to use clone
+  FunctionParam &operator= (FunctionParam const &other)
+  {
+    locus = other.locus;
+    node_id = other.node_id;
+
+    // guard to prevent nullptr dereference
+    if (other.param_name != nullptr)
+      param_name = other.param_name->clone_pattern ();
+    else
+      param_name = nullptr;
+    if (other.type != nullptr)
+      type = other.type->clone_type ();
+    else
+      type = nullptr;
+
+    return *this;
+  }
+
+  // move constructors
+  FunctionParam (FunctionParam &&other) = default;
+  FunctionParam &operator= (FunctionParam &&other) = default;
+
+  // Returns whether FunctionParam is in an invalid state.
+  bool is_error () const { return param_name == nullptr || type == nullptr; }
+
+  // Creates an error FunctionParam.
+  static FunctionParam create_error ()
+  {
+    return FunctionParam (nullptr, nullptr, {}, Location ());
+  }
+
+  std::string as_string () const;
+
+  Location get_locus () const { return locus; }
+
+  // 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; }
+
+  // TODO: is this better? Or is a "vis_block" better?
+  std::unique_ptr<Pattern> &get_pattern ()
+  {
+    rust_assert (param_name != nullptr);
+    return param_name;
+  }
+
+  // TODO: is this better? Or is a "vis_block" better?
+  std::unique_ptr<Type> &get_type ()
+  {
+    rust_assert (type != nullptr);
+    return type;
+  }
+  NodeId get_node_id () const { return node_id; }
+
+protected:
+  NodeId node_id;
+};
+
+// Visibility of item - if the item has it, then it is some form of public
+struct Visibility
+{
+public:
+  enum VisType
+  {
+    PRIV,
+    PUB,
+    PUB_CRATE,
+    PUB_SELF,
+    PUB_SUPER,
+    PUB_IN_PATH
+  };
+
+private:
+  VisType vis_type;
+  // Only assigned if vis_type is IN_PATH
+  SimplePath in_path;
+
+  // should this store location info?
+
+public:
+  // Creates a Visibility - TODO make constructor protected or private?
+  Visibility (VisType vis_type, SimplePath in_path)
+    : vis_type (vis_type), in_path (std::move (in_path))
+  {}
+
+  VisType get_public_vis_type () const { return vis_type; }
+
+  // Returns whether visibility is in an error state.
+  bool is_error () const
+  {
+    return vis_type == PUB_IN_PATH && in_path.is_empty ();
+  }
+
+  // Returns whether a visibility has a path
+  bool has_path () const { return !(is_error ()) && vis_type == PUB_IN_PATH; }
+
+  // Returns whether visibility is public or not.
+  bool is_public () const { return vis_type != PRIV && !is_error (); }
+
+  // Creates an error visibility.
+  static Visibility create_error ()
+  {
+    return Visibility (PUB_IN_PATH, SimplePath::create_empty ());
+  }
+
+  // Unique pointer custom clone function
+  /*std::unique_ptr<Visibility> clone_visibility() const {
+      return std::unique_ptr<Visibility>(clone_visibility_impl());
+  }*/
+
+  /* TODO: think of a way to only allow valid Visibility states - polymorphism
+   * is one idea but may be too resource-intensive. */
+
+  // Creates a public visibility with no further features/arguments.
+  static Visibility create_public ()
+  {
+    return Visibility (PUB, SimplePath::create_empty ());
+  }
+
+  // Creates a public visibility with crate-relative paths
+  static Visibility create_crate (Location crate_tok_location)
+  {
+    return Visibility (PUB_CRATE,
+		       SimplePath::from_str ("crate", crate_tok_location));
+  }
+
+  // Creates a public visibility with self-relative paths
+  static Visibility create_self (Location self_tok_location)
+  {
+    return Visibility (PUB_SELF,
+		       SimplePath::from_str ("self", self_tok_location));
+  }
+
+  // Creates a public visibility with parent module-relative paths
+  static Visibility create_super (Location super_tok_location)
+  {
+    return Visibility (PUB_SUPER,
+		       SimplePath::from_str ("super", super_tok_location));
+  }
+
+  // Creates a private visibility
+  static Visibility create_private ()
+  {
+    return Visibility (PRIV, SimplePath::create_empty ());
+  }
+
+  // Creates a public visibility with a given path or whatever.
+  static Visibility create_in_path (SimplePath in_path)
+  {
+    return Visibility (PUB_IN_PATH, std::move (in_path));
+  }
+
+  std::string as_string () const;
+  const SimplePath &get_path () const { return in_path; }
+  SimplePath &get_path () { return in_path; }
+
+protected:
+  // Clone function implementation - not currently virtual but may be if
+  // polymorphism used
+  /*virtual*/ Visibility *clone_visibility_impl () const
+  {
+    return new Visibility (*this);
+  }
+};
+
+// A method (function belonging to a type)
+class Method : public InherentImplItem, public TraitImplItem
+{
+  std::vector<Attribute> outer_attrs;
+  Visibility vis;
+  FunctionQualifiers qualifiers;
+  Identifier method_name;
+  std::vector<std::unique_ptr<GenericParam>> generic_params;
+  SelfParam self_param;
+  std::vector<FunctionParam> function_params;
+  std::unique_ptr<Type> return_type;
+  WhereClause where_clause;
+  std::unique_ptr<BlockExpr> function_body;
+  Location locus;
+  NodeId node_id;
+
+public:
+  // Returns whether the method is in an error state.
+  bool is_error () const
+  {
+    return function_body == nullptr || method_name.empty ()
+	   || self_param.is_error ();
+  }
+
+  // Creates an error state method.
+  static Method create_error ()
+  {
+    return Method ("", FunctionQualifiers (Location (), NONE, true),
+		   std::vector<std::unique_ptr<GenericParam>> (),
+		   SelfParam::create_error (), std::vector<FunctionParam> (),
+		   nullptr, WhereClause::create_empty (), nullptr,
+		   Visibility::create_error (), std::vector<Attribute> (), {});
+  }
+
+  // Returns whether the method has generic parameters.
+  bool has_generics () const { return !generic_params.empty (); }
+
+  // Returns whether the method has parameters.
+  bool has_params () const { return !function_params.empty (); }
+
+  // Returns whether the method has a return type (void otherwise).
+  bool has_return_type () const { return return_type != nullptr; }
+
+  // Returns whether the where clause exists (i.e. has items)
+  bool has_where_clause () const { return !where_clause.is_empty (); }
+
+  // Returns whether method has a non-default visibility.
+  bool has_visibility () const { return !vis.is_error (); }
+
+  // Mega-constructor with all possible fields
+  Method (Identifier method_name, FunctionQualifiers qualifiers,
+	  std::vector<std::unique_ptr<GenericParam>> generic_params,
+	  SelfParam self_param, std::vector<FunctionParam> function_params,
+	  std::unique_ptr<Type> return_type, WhereClause where_clause,
+	  std::unique_ptr<BlockExpr> function_body, Visibility vis,
+	  std::vector<Attribute> outer_attrs, Location locus)
+    : outer_attrs (std::move (outer_attrs)), vis (std::move (vis)),
+      qualifiers (std::move (qualifiers)),
+      method_name (std::move (method_name)),
+      generic_params (std::move (generic_params)),
+      self_param (std::move (self_param)),
+      function_params (std::move (function_params)),
+      return_type (std::move (return_type)),
+      where_clause (std::move (where_clause)),
+      function_body (std::move (function_body)), locus (locus),
+      node_id (Analysis::Mappings::get ()->get_next_node_id ())
+  {}
+
+  // TODO: add constructor with less fields
+
+  // Copy constructor with clone
+  Method (Method const &other)
+    : outer_attrs (other.outer_attrs), vis (other.vis),
+      qualifiers (other.qualifiers), method_name (other.method_name),
+      self_param (other.self_param), function_params (other.function_params),
+      where_clause (other.where_clause), locus (other.locus)
+  {
+    // guard to prevent null dereference (always required)
+    if (other.return_type != nullptr)
+      return_type = other.return_type->clone_type ();
+
+    // guard to prevent null dereference (only required if error state)
+    if (other.function_body != nullptr)
+      function_body = other.function_body->clone_block_expr ();
+
+    generic_params.reserve (other.generic_params.size ());
+    for (const auto &e : other.generic_params)
+      generic_params.push_back (e->clone_generic_param ());
+
+    node_id = other.node_id;
+  }
+
+  // Overloaded assignment operator to clone
+  Method &operator= (Method const &other)
+  {
+    method_name = other.method_name;
+    outer_attrs = other.outer_attrs;
+    vis = other.vis;
+    qualifiers = other.qualifiers;
+    self_param = other.self_param;
+    function_params = other.function_params;
+    where_clause = other.where_clause;
+    locus = other.locus;
+
+    // guard to prevent null dereference (always required)
+    if (other.return_type != nullptr)
+      return_type = other.return_type->clone_type ();
+    else
+      return_type = nullptr;
+
+    // guard to prevent null dereference (only required if error state)
+    if (other.function_body != nullptr)
+      function_body = other.function_body->clone_block_expr ();
+    else
+      function_body = nullptr;
+
+    generic_params.reserve (other.generic_params.size ());
+    for (const auto &e : other.generic_params)
+      generic_params.push_back (e->clone_generic_param ());
+
+    node_id = other.node_id;
+
+    return *this;
+  }
+
+  // move constructors
+  Method (Method &&other) = default;
+  Method &operator= (Method &&other) = default;
+
+  std::string as_string () const override;
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // Invalid if block is null, so base stripping on that.
+  void mark_for_strip () override { function_body = nullptr; }
+  bool is_marked_for_strip () const override
+  {
+    return function_body == 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; }
+
+  std::vector<FunctionParam> &get_function_params () { return function_params; }
+  const std::vector<FunctionParam> &get_function_params () const
+  {
+    return function_params;
+  }
+
+  std::vector<std::unique_ptr<GenericParam>> &get_generic_params ()
+  {
+    return generic_params;
+  }
+  const std::vector<std::unique_ptr<GenericParam>> &get_generic_params () const
+  {
+    return generic_params;
+  }
+
+  // TODO: is this better? Or is a "vis_block" better?
+  std::unique_ptr<BlockExpr> &get_definition ()
+  {
+    rust_assert (function_body != nullptr);
+    return function_body;
+  }
+
+  SelfParam &get_self_param () { return self_param; }
+  const SelfParam &get_self_param () const { return self_param; }
+
+  // TODO: is this better? Or is a "vis_block" better?
+  std::unique_ptr<Type> &get_return_type ()
+  {
+    rust_assert (has_return_type ());
+    return return_type;
+  }
+
+  // TODO: is this better? Or is a "vis_block" better?
+  WhereClause &get_where_clause () { return where_clause; }
+
+  Identifier get_method_name () const { return method_name; }
+
+  NodeId get_node_id () const { return node_id; }
+
+  Location get_locus () const override final { return locus; }
+
+  FunctionQualifiers get_qualifiers () { return qualifiers; }
+
+  const Visibility &get_visibility () const { return vis; }
+
+protected:
+  /* Use covariance to implement clone function as returning this object
+   * rather than base */
+  Method *clone_inherent_impl_item_impl () const final override
+  {
+    return clone_method_impl ();
+  }
+
+  /* Use covariance to implement clone function as returning this object
+   * rather than base */
+  Method *clone_trait_impl_item_impl () const final override
+  {
+    return clone_method_impl ();
+  }
+
+  /*virtual*/ Method *clone_method_impl () const { return new Method (*this); }
+};
+
+// Item that supports visibility - abstract base class
+class VisItem : public Item
+{
+  Visibility visibility;
+  std::vector<Attribute> outer_attrs;
+
+protected:
+  // Visibility constructor
+  VisItem (Visibility visibility,
+	   std::vector<Attribute> outer_attrs = std::vector<Attribute> ())
+    : visibility (std::move (visibility)), outer_attrs (std::move (outer_attrs))
+  {}
+
+  // Visibility copy constructor
+  VisItem (VisItem const &other)
+    : visibility (other.visibility), outer_attrs (other.outer_attrs)
+  {}
+
+  // Overload assignment operator to clone
+  VisItem &operator= (VisItem const &other)
+  {
+    visibility = other.visibility;
+    outer_attrs = other.outer_attrs;
+
+    return *this;
+  }
+
+  // move constructors
+  VisItem (VisItem &&other) = default;
+  VisItem &operator= (VisItem &&other) = default;
+
+public:
+  /* Does the item have some kind of public visibility (non-default
+   * visibility)? */
+  bool has_visibility () const { return visibility.is_public (); }
+
+  std::string as_string () const override;
+
+  // TODO: this mutable getter seems really dodgy. Think up better way.
+  Visibility &get_visibility () { return visibility; }
+  const Visibility &get_visibility () const { return visibility; }
+
+  std::vector<Attribute> &get_outer_attrs () { return outer_attrs; }
+  const std::vector<Attribute> &get_outer_attrs () const { return outer_attrs; }
+};
+
+// Rust module item - abstract base class
+class Module : public VisItem
+{
+public:
+  // Type of the current module. A module can be either loaded or unloaded,
+  // meaning that the items of the module can already be present or not. For
+  // example, the following module would be loaded: `mod foo { fn bar() {} }`.
+  // However, the module would be unloaded if it refers to an external file (i.e
+  // `mod foo;`) and then become loaded upon expansion.
+  enum ModuleKind
+  {
+    LOADED,
+    UNLOADED,
+  };
+
+  Identifier get_name () const { return module_name; }
+
+private:
+  Identifier module_name;
+  Location locus;
+  ModuleKind kind;
+
+  // Name of the file including the module
+  std::string outer_filename;
+  // bool has_inner_attrs;
+  std::vector<Attribute> inner_attrs;
+  // bool has_items;
+  std::vector<std::unique_ptr<Item>> items;
+  // Names of including inline modules (immediate parent is last in the list)
+  std::vector<std::string> module_scope;
+
+  // Filename the module refers to. Empty string on LOADED modules or if an
+  // error occured when dealing with UNLOADED modules
+  std::string module_file;
+
+  void clone_items (const std::vector<std::unique_ptr<Item>> &other_items)
+  {
+    items.reserve (other_items.size ());
+    for (const auto &e : other_items)
+      items.push_back (e->clone_item ());
+  }
+
+public:
+  // Returns whether the module has items in its body.
+  bool has_items () const { return !items.empty (); }
+
+  // Returns whether the module has any inner attributes.
+  bool has_inner_attrs () const { return !inner_attrs.empty (); }
+
+  // Unloaded module constructor
+  Module (Identifier module_name, Visibility visibility,
+	  std::vector<Attribute> outer_attrs, Location locus,
+	  std::string outer_filename, std::vector<std::string> module_scope)
+    : VisItem (std::move (visibility), std::move (outer_attrs)),
+      module_name (module_name), locus (locus), kind (ModuleKind::UNLOADED),
+      outer_filename (outer_filename), inner_attrs (std::vector<Attribute> ()),
+      items (std::vector<std::unique_ptr<Item>> ()),
+      module_scope (std::move (module_scope))
+  {}
+
+  // Loaded module constructor, with items
+  Module (Identifier name, Location locus,
+	  std::vector<std::unique_ptr<Item>> items,
+	  Visibility visibility = Visibility::create_error (),
+	  std::vector<Attribute> inner_attrs = std::vector<Attribute> (),
+	  std::vector<Attribute> outer_attrs = std::vector<Attribute> ())
+    : VisItem (std::move (visibility), std::move (outer_attrs)),
+      module_name (name), locus (locus), kind (ModuleKind::LOADED),
+      outer_filename (std::string ()), inner_attrs (std::move (inner_attrs)),
+      items (std::move (items))
+  {}
+
+  // Copy constructor with vector clone
+  Module (Module const &other)
+    : VisItem (other), module_name (other.module_name), locus (other.locus),
+      kind (other.kind), inner_attrs (other.inner_attrs),
+      module_scope (other.module_scope)
+  {
+    // We need to check whether we are copying a loaded module or an unloaded
+    // one. In the second case, clear the `items` vector.
+    if (other.kind == LOADED)
+      clone_items (other.items);
+    else
+      items.clear ();
+  }
+
+  // Overloaded assignment operator with vector clone
+  Module &operator= (Module const &other)
+  {
+    VisItem::operator= (other);
+
+    module_name = other.module_name;
+    locus = other.locus;
+    kind = other.kind;
+    inner_attrs = other.inner_attrs;
+    module_scope = other.module_scope;
+
+    // Likewise, we need to clear the `items` vector in case the other module is
+    // unloaded
+    if (kind == LOADED)
+      clone_items (other.items);
+    else
+      items.clear ();
+
+    return *this;
+  }
+
+  // Search for the filename associated with an external module, storing it in
+  // module_file
+  void process_file_path ();
+  // Load the items contained in an external module
+  void load_items ();
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  /* Override that runs the function recursively on all items contained within
+   * the module. */
+  void add_crate_name (std::vector<std::string> &names) const override;
+
+  // Returns the kind of the module
+  enum ModuleKind get_kind () const { return kind; }
+
+  // TODO: think of better way to do this - mutable getter seems dodgy
+  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<Item>> &get_items () const { return items; }
+  std::vector<std::unique_ptr<Item>> &get_items () { return items; }
+
+  // move constructors
+  Module (Module &&other) = default;
+  Module &operator= (Module &&other) = default;
+
+  std::string as_string () const override;
+
+  Location get_locus () const override final { return locus; }
+
+  // Invalid if name is empty, so base stripping on that.
+  void mark_for_strip () override { module_name = ""; }
+  bool is_marked_for_strip () const override { return module_name.empty (); }
+
+protected:
+  /* Use covariance to implement clone function as returning this object
+   * rather than base */
+  Module *clone_item_impl () const override { return new Module (*this); }
+};
+
+// Rust extern crate declaration AST node
+class ExternCrate : public VisItem
+{
+  // this is either an identifier or "self", with self parsed to string
+  std::string referenced_crate;
+  // bool has_as_clause;
+  // AsClause as_clause;
+  // this is either an identifier or "_", with _ parsed to string
+  std::string as_clause_name;
+
+  Location locus;
+
+  /* e.g.
+      "extern crate foo as _"
+      "extern crate foo"
+      "extern crate std as cool_std"  */
+public:
+  std::string as_string () const override;
+
+  // Returns whether extern crate declaration has an as clause.
+  bool has_as_clause () const { return !as_clause_name.empty (); }
+
+  /* Returns whether extern crate declaration references the current crate
+   * (i.e. self). */
+  bool references_self () const { return referenced_crate == "self"; }
+
+  // Constructor
+  ExternCrate (std::string referenced_crate, Visibility visibility,
+	       std::vector<Attribute> outer_attrs, Location locus,
+	       std::string as_clause_name = std::string ())
+    : VisItem (std::move (visibility), std::move (outer_attrs)),
+      referenced_crate (std::move (referenced_crate)),
+      as_clause_name (std::move (as_clause_name)), locus (locus)
+  {}
+
+  Location get_locus () const override final { return locus; }
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  const std::string &get_referenced_crate () const { return referenced_crate; }
+  const std::string &get_as_clause () const { return as_clause_name; }
+
+  // Override that adds extern crate name in decl to passed list of names.
+  void add_crate_name (std::vector<std::string> &names) const override
+  {
+    names.push_back (referenced_crate);
+  }
+
+  // Invalid if crate name is empty, so base stripping on that.
+  void mark_for_strip () override { referenced_crate = ""; }
+  bool is_marked_for_strip () const override
+  {
+    return referenced_crate.empty ();
+  }
+
+protected:
+  /* Use covariance to implement clone function as returning this object
+   * rather than base */
+  ExternCrate *clone_item_impl () const override
+  {
+    return new ExternCrate (*this);
+  }
+};
+
+// The path-ish thing referred to in a use declaration - abstract base class
+class UseTree
+{
+  Location locus;
+
+public:
+  enum Kind
+  {
+    Glob,
+    Rebind,
+    List,
+  };
+
+  virtual ~UseTree () {}
+
+  // Overload assignment operator to clone
+  UseTree &operator= (UseTree const &other)
+  {
+    locus = other.locus;
+
+    return *this;
+  }
+
+  UseTree (const UseTree &other) = default;
+
+  // move constructors
+  UseTree (UseTree &&other) = default;
+  UseTree &operator= (UseTree &&other) = default;
+
+  // Unique pointer custom clone function
+  std::unique_ptr<UseTree> clone_use_tree () const
+  {
+    return std::unique_ptr<UseTree> (clone_use_tree_impl ());
+  }
+
+  virtual std::string as_string () const = 0;
+  virtual Kind get_kind () const = 0;
+
+  Location get_locus () const { return locus; }
+
+  virtual void accept_vis (ASTVisitor &vis) = 0;
+
+protected:
+  // Clone function implementation as pure virtual method
+  virtual UseTree *clone_use_tree_impl () const = 0;
+
+  UseTree (Location locus) : locus (locus) {}
+};
+
+// Use tree with a glob (wildcard) operator
+class UseTreeGlob : public UseTree
+{
+public:
+  enum PathType
+  {
+    NO_PATH,
+    GLOBAL,
+    PATH_PREFIXED
+  };
+
+private:
+  PathType glob_type;
+  SimplePath path;
+
+public:
+  UseTreeGlob (PathType glob_type, SimplePath path, Location locus)
+    : UseTree (locus), glob_type (glob_type), path (std::move (path))
+  {
+    if (this->glob_type != PATH_PREFIXED)
+      {
+	// compiler implementation error if there is a path with a
+	// non-path-prefixed use tree glob
+	rust_assert (!has_path ());
+      }
+    // TODO: do path-prefixed paths also have to have a path? If so, have an
+    // assert for that too.
+  }
+
+  /* Returns whether has path. Should be made redundant by PathType
+   * PATH_PREFIXED. */
+  bool has_path () const { return !path.is_empty (); }
+
+  std::string as_string () const override;
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  Kind get_kind () const override { return Glob; }
+
+  SimplePath get_path () const
+  {
+    rust_assert (has_path ());
+    return path;
+  }
+
+  /* TODO: find way to ensure only PATH_PREFIXED glob_type has path - factory
+   * methods? */
+protected:
+  /* Use covariance to implement clone function as returning this object
+   * rather than base */
+  UseTreeGlob *clone_use_tree_impl () const override
+  {
+    return new UseTreeGlob (*this);
+  }
+};
+
+// Use tree with a list of paths with a common prefix
+class UseTreeList : public UseTree
+{
+public:
+  enum PathType
+  {
+    NO_PATH,
+    GLOBAL,
+    PATH_PREFIXED
+  };
+
+private:
+  PathType path_type;
+  SimplePath path;
+
+  std::vector<std::unique_ptr<UseTree>> trees;
+
+public:
+  UseTreeList (PathType path_type, SimplePath path,
+	       std::vector<std::unique_ptr<UseTree>> trees, Location locus)
+    : UseTree (locus), path_type (path_type), path (std::move (path)),
+      trees (std::move (trees))
+  {
+    if (this->path_type != PATH_PREFIXED)
+      {
+	// compiler implementation error if there is a path with a
+	// non-path-prefixed use tree glob
+	rust_assert (!has_path ());
+      }
+    // TODO: do path-prefixed paths also have to have a path? If so, have an
+    // assert for that too.
+  }
+
+  // copy constructor with vector clone
+  UseTreeList (UseTreeList const &other)
+    : UseTree (other), path_type (other.path_type), path (other.path)
+  {
+    trees.reserve (other.trees.size ());
+    for (const auto &e : other.trees)
+      trees.push_back (e->clone_use_tree ());
+  }
+
+  // overloaded assignment operator with vector clone
+  UseTreeList &operator= (UseTreeList const &other)
+  {
+    UseTree::operator= (other);
+    path_type = other.path_type;
+    path = other.path;
+
+    trees.reserve (other.trees.size ());
+    for (const auto &e : other.trees)
+      trees.push_back (e->clone_use_tree ());
+
+    return *this;
+  }
+
+  // move constructors
+  UseTreeList (UseTreeList &&other) = default;
+  UseTreeList &operator= (UseTreeList &&other) = default;
+
+  // Returns whether has path. Should be made redundant by path_type.
+  bool has_path () const { return !path.is_empty (); }
+
+  // Returns whether has inner tree elements.
+  bool has_trees () const { return !trees.empty (); }
+
+  std::string as_string () const override;
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  Kind get_kind () const override { return List; }
+  SimplePath get_path () const
+  {
+    rust_assert (has_path ());
+    return path;
+  }
+
+  const std::vector<std::unique_ptr<UseTree>> &get_trees () const
+  {
+    return trees;
+  }
+
+  // TODO: find way to ensure only PATH_PREFIXED path_type has path - factory
+  // methods?
+protected:
+  /* Use covariance to implement clone function as returning this object
+   * rather than base */
+  UseTreeList *clone_use_tree_impl () const override
+  {
+    return new UseTreeList (*this);
+  }
+};
+
+// Use tree where it rebinds the module name as something else
+class UseTreeRebind : public UseTree
+{
+public:
+  enum NewBindType
+  {
+    NONE,
+    IDENTIFIER,
+    WILDCARD
+  };
+
+private:
+  SimplePath path;
+
+  NewBindType bind_type;
+  Identifier identifier; // only if NewBindType is IDENTIFIER
+
+public:
+  UseTreeRebind (NewBindType bind_type, SimplePath path, Location locus,
+		 Identifier identifier = std::string ())
+    : UseTree (locus), path (std::move (path)), bind_type (bind_type),
+      identifier (std::move (identifier))
+  {}
+
+  // Returns whether has path (this should always be true).
+  bool has_path () const { return !path.is_empty (); }
+
+  // Returns whether has identifier (or, rather, is allowed to).
+  bool has_identifier () const { return bind_type == IDENTIFIER; }
+
+  std::string as_string () const override;
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  Kind get_kind () const override { return Rebind; }
+
+  SimplePath get_path () const
+  {
+    rust_assert (has_path ());
+    return path;
+  }
+
+  const Identifier &get_identifier () const
+  {
+    rust_assert (has_identifier ());
+    return identifier;
+  }
+
+  // TODO: find way to ensure only PATH_PREFIXED path_type has path - factory
+  // methods?
+protected:
+  /* Use covariance to implement clone function as returning this object
+   * rather than base */
+  virtual UseTreeRebind *clone_use_tree_impl () const override
+  {
+    return new UseTreeRebind (*this);
+  }
+};
+
+// Rust use declaration (i.e. for modules) AST node
+class UseDeclaration : public VisItem
+{
+  std::unique_ptr<UseTree> use_tree;
+  Location locus;
+
+public:
+  std::string as_string () const override;
+
+  UseDeclaration (std::unique_ptr<UseTree> use_tree, Visibility visibility,
+		  std::vector<Attribute> outer_attrs, Location locus)
+    : VisItem (std::move (visibility), std::move (outer_attrs)),
+      use_tree (std::move (use_tree)), locus (locus)
+  {}
+
+  // Copy constructor with clone
+  UseDeclaration (UseDeclaration const &other)
+    : VisItem (other), locus (other.locus)
+  {
+    // guard to prevent null dereference (only required if error state)
+    if (other.use_tree != nullptr)
+      use_tree = other.use_tree->clone_use_tree ();
+  }
+
+  // Overloaded assignment operator to clone
+  UseDeclaration &operator= (UseDeclaration const &other)
+  {
+    VisItem::operator= (other);
+    // visibility = other.visibility->clone_visibility();
+    // outer_attrs = other.outer_attrs;
+    locus = other.locus;
+
+    // guard to prevent null dereference (only required if error state)
+    if (other.use_tree != nullptr)
+      use_tree = other.use_tree->clone_use_tree ();
+    else
+      use_tree = nullptr;
+
+    return *this;
+  }
+
+  // move constructors
+  UseDeclaration (UseDeclaration &&other) = default;
+  UseDeclaration &operator= (UseDeclaration &&other) = default;
+
+  Location get_locus () const override final { return locus; }
+  const std::unique_ptr<UseTree> &get_tree () const { return use_tree; }
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // Invalid if use tree is null, so base stripping on that.
+  void mark_for_strip () override { use_tree = nullptr; }
+  bool is_marked_for_strip () const override { return use_tree == nullptr; }
+
+protected:
+  /* Use covariance to implement clone function as returning this object
+   * rather than base */
+  UseDeclaration *clone_item_impl () const override
+  {
+    return new UseDeclaration (*this);
+  }
+};
+
+class LetStmt;
+
+// Rust function declaration AST node
+class Function : public VisItem, public InherentImplItem, public TraitImplItem
+{
+  FunctionQualifiers qualifiers;
+  Identifier function_name;
+  std::vector<std::unique_ptr<GenericParam>> generic_params;
+  std::vector<FunctionParam> function_params;
+  std::unique_ptr<Type> return_type;
+  WhereClause where_clause;
+  std::unique_ptr<BlockExpr> function_body;
+  Location locus;
+
+public:
+  std::string as_string () const override;
+
+  // Returns whether function has generic parameters.
+  bool has_generics () const { return !generic_params.empty (); }
+
+  // Returns whether function has regular parameters.
+  bool has_function_params () const { return !function_params.empty (); }
+
+  // Returns whether function has return type - if not, it is void.
+  bool has_return_type () const { return return_type != nullptr; }
+
+  // Returns whether function has a where clause.
+  bool has_where_clause () const { return !where_clause.is_empty (); }
+
+  // Mega-constructor with all possible fields
+  Function (Identifier function_name, FunctionQualifiers qualifiers,
+	    std::vector<std::unique_ptr<GenericParam>> generic_params,
+	    std::vector<FunctionParam> function_params,
+	    std::unique_ptr<Type> return_type, WhereClause where_clause,
+	    std::unique_ptr<BlockExpr> function_body, Visibility vis,
+	    std::vector<Attribute> outer_attrs, Location locus)
+    : VisItem (std::move (vis), std::move (outer_attrs)),
+      qualifiers (std::move (qualifiers)),
+      function_name (std::move (function_name)),
+      generic_params (std::move (generic_params)),
+      function_params (std::move (function_params)),
+      return_type (std::move (return_type)),
+      where_clause (std::move (where_clause)),
+      function_body (std::move (function_body)), locus (locus)
+  {}
+
+  // TODO: add constructor with less fields
+
+  // Copy constructor with clone
+  Function (Function const &other)
+    : VisItem (other), qualifiers (other.qualifiers),
+      function_name (other.function_name),
+      function_params (other.function_params),
+      where_clause (other.where_clause), locus (other.locus)
+  {
+    // guard to prevent null dereference (always required)
+    if (other.return_type != nullptr)
+      return_type = other.return_type->clone_type ();
+
+    // guard to prevent null dereference (only required if error state)
+    if (other.function_body != nullptr)
+      function_body = other.function_body->clone_block_expr ();
+
+    generic_params.reserve (other.generic_params.size ());
+    for (const auto &e : other.generic_params)
+      generic_params.push_back (e->clone_generic_param ());
+  }
+
+  // Overloaded assignment operator to clone
+  Function &operator= (Function const &other)
+  {
+    VisItem::operator= (other);
+    function_name = other.function_name;
+    qualifiers = other.qualifiers;
+    function_params = other.function_params;
+    where_clause = other.where_clause;
+    // visibility = other.visibility->clone_visibility();
+    // outer_attrs = other.outer_attrs;
+    locus = other.locus;
+
+    // guard to prevent null dereference (always required)
+    if (other.return_type != nullptr)
+      return_type = other.return_type->clone_type ();
+    else
+      return_type = nullptr;
+
+    // guard to prevent null dereference (only required if error state)
+    if (other.function_body != nullptr)
+      function_body = other.function_body->clone_block_expr ();
+    else
+      function_body = nullptr;
+
+    generic_params.reserve (other.generic_params.size ());
+    for (const auto &e : other.generic_params)
+      generic_params.push_back (e->clone_generic_param ());
+
+    return *this;
+  }
+
+  // move constructors
+  Function (Function &&other) = default;
+  Function &operator= (Function &&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 { function_body = nullptr; }
+  bool is_marked_for_strip () const override
+  {
+    return function_body == nullptr;
+  }
+
+  std::vector<FunctionParam> &get_function_params () { return function_params; }
+  const std::vector<FunctionParam> &get_function_params () const
+  {
+    return function_params;
+  }
+
+  std::vector<std::unique_ptr<GenericParam>> &get_generic_params ()
+  {
+    return generic_params;
+  }
+  const std::vector<std::unique_ptr<GenericParam>> &get_generic_params () const
+  {
+    return generic_params;
+  }
+
+  // TODO: is this better? Or is a "vis_block" better?
+  std::unique_ptr<BlockExpr> &get_definition ()
+  {
+    rust_assert (function_body != nullptr);
+    return function_body;
+  }
+
+  const FunctionQualifiers &get_qualifiers () const { return qualifiers; }
+
+  Identifier get_function_name () const { return function_name; }
+
+  // TODO: is this better? Or is a "vis_block" better?
+  WhereClause &get_where_clause () { return where_clause; }
+
+  // TODO: is this better? Or is a "vis_block" better?
+  std::unique_ptr<Type> &get_return_type ()
+  {
+    rust_assert (has_return_type ());
+    return return_type;
+  }
+
+protected:
+  /* Use covariance to implement clone function as returning this object
+   * rather than base */
+  Function *clone_item_impl () const override { return new Function (*this); }
+
+  /* Use covariance to implement clone function as returning this object
+   * rather than base */
+  Function *clone_inherent_impl_item_impl () const override
+  {
+    return new Function (*this);
+  }
+
+  /* Use covariance to implement clone function as returning this object
+   * rather than base */
+  Function *clone_trait_impl_item_impl () const override
+  {
+    return new Function (*this);
+  }
+};
+
+// Rust type alias (i.e. typedef) AST node
+class TypeAlias : public VisItem, public TraitImplItem
+{
+  Identifier new_type_name;
+
+  // bool has_generics;
+  // Generics generic_params;
+  std::vector<std::unique_ptr<GenericParam>> generic_params; // inlined
+
+  // bool has_where_clause;
+  WhereClause where_clause;
+
+  std::unique_ptr<Type> existing_type;
+
+  Location locus;
+
+public:
+  std::string as_string () const override;
+
+  // Returns whether type alias has generic parameters.
+  bool has_generics () const { return !generic_params.empty (); }
+
+  // Returns whether type alias has a where clause.
+  bool has_where_clause () const { return !where_clause.is_empty (); }
+
+  // Mega-constructor with all possible fields
+  TypeAlias (Identifier new_type_name,
+	     std::vector<std::unique_ptr<GenericParam>> generic_params,
+	     WhereClause where_clause, std::unique_ptr<Type> existing_type,
+	     Visibility vis, std::vector<Attribute> outer_attrs, Location locus)
+    : VisItem (std::move (vis), std::move (outer_attrs)),
+      new_type_name (std::move (new_type_name)),
+      generic_params (std::move (generic_params)),
+      where_clause (std::move (where_clause)),
+      existing_type (std::move (existing_type)), locus (locus)
+  {}
+
+  // Copy constructor
+  TypeAlias (TypeAlias const &other)
+    : VisItem (other), new_type_name (other.new_type_name),
+      where_clause (other.where_clause), locus (other.locus)
+  {
+    // guard to prevent null dereference (only required if error state)
+    if (other.existing_type != nullptr)
+      existing_type = other.existing_type->clone_type ();
+
+    generic_params.reserve (other.generic_params.size ());
+    for (const auto &e : other.generic_params)
+      generic_params.push_back (e->clone_generic_param ());
+  }
+
+  // Overloaded assignment operator to clone
+  TypeAlias &operator= (TypeAlias const &other)
+  {
+    VisItem::operator= (other);
+    new_type_name = other.new_type_name;
+    where_clause = other.where_clause;
+    // visibility = other.visibility->clone_visibility();
+    // outer_attrs = other.outer_attrs;
+    locus = other.locus;
+
+    // guard to prevent null dereference (only required if error state)
+    if (other.existing_type != nullptr)
+      existing_type = other.existing_type->clone_type ();
+    else
+      existing_type = nullptr;
+
+    generic_params.reserve (other.generic_params.size ());
+    for (const auto &e : other.generic_params)
+      generic_params.push_back (e->clone_generic_param ());
+
+    return *this;
+  }
+
+  // move constructors
+  TypeAlias (TypeAlias &&other) = default;
+  TypeAlias &operator= (TypeAlias &&other) = default;
+
+  Location get_locus () const override final { return locus; }
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // Invalid if existing type is null, so base stripping on that.
+  void mark_for_strip () override { existing_type = nullptr; }
+  bool is_marked_for_strip () const override
+  {
+    return existing_type == nullptr;
+  }
+
+  std::vector<std::unique_ptr<GenericParam>> &get_generic_params ()
+  {
+    return generic_params;
+  }
+  const std::vector<std::unique_ptr<GenericParam>> &get_generic_params () const
+  {
+    return generic_params;
+  }
+
+  // TODO: is this better? Or is a "vis_block" better?
+  WhereClause &get_where_clause () { return where_clause; }
+
+  // TODO: is this better? Or is a "vis_block" better?
+  std::unique_ptr<Type> &get_type_aliased ()
+  {
+    rust_assert (existing_type != nullptr);
+    return existing_type;
+  }
+
+  Identifier get_new_type_name () const { return new_type_name; }
+
+protected:
+  /* Use covariance to implement clone function as returning this object
+   * rather than base */
+  TypeAlias *clone_item_impl () const override { return new TypeAlias (*this); }
+
+  /* Use covariance to implement clone function as returning this object
+   * rather than base */
+  TypeAlias *clone_trait_impl_item_impl () const override
+  {
+    return new TypeAlias (*this);
+  }
+};
+
+// Rust base struct declaration AST node - abstract base class
+class Struct : public VisItem
+{
+protected:
+  // protected to enable access by derived classes - allows better as_string
+  Identifier struct_name;
+
+  // bool has_generics;
+  // Generics generic_params;
+  std::vector<std::unique_ptr<GenericParam>> generic_params; // inlined
+
+  // bool has_where_clause;
+  WhereClause where_clause;
+
+private:
+  Location locus;
+
+public:
+  // Returns whether struct has generic parameters.
+  bool has_generics () const { return !generic_params.empty (); }
+
+  // Returns whether struct has a where clause.
+  bool has_where_clause () const { return !where_clause.is_empty (); }
+
+  Location get_locus () const override final { return locus; }
+
+  // Invalid if name is empty, so base stripping on that.
+  void mark_for_strip () override { struct_name = ""; }
+  bool is_marked_for_strip () const override { return struct_name.empty (); }
+
+  Identifier get_struct_name () const { return struct_name; }
+
+  std::vector<std::unique_ptr<GenericParam>> &get_generic_params ()
+  {
+    return generic_params;
+  }
+  const std::vector<std::unique_ptr<GenericParam>> &get_generic_params () const
+  {
+    return generic_params;
+  }
+
+  // TODO: is this better? Or is a "vis_block" better?
+  WhereClause &get_where_clause () { return where_clause; }
+
+  Identifier get_identifier () const { return struct_name; }
+
+protected:
+  Struct (Identifier struct_name,
+	  std::vector<std::unique_ptr<GenericParam>> generic_params,
+	  WhereClause where_clause, Visibility vis, Location locus,
+	  std::vector<Attribute> outer_attrs = std::vector<Attribute> ())
+    : VisItem (std::move (vis), std::move (outer_attrs)),
+      struct_name (std::move (struct_name)),
+      generic_params (std::move (generic_params)),
+      where_clause (std::move (where_clause)), locus (locus)
+  {}
+
+  // Copy constructor with vector clone
+  Struct (Struct const &other)
+    : VisItem (other), struct_name (other.struct_name),
+      where_clause (other.where_clause), locus (other.locus)
+  {
+    generic_params.reserve (other.generic_params.size ());
+    for (const auto &e : other.generic_params)
+      generic_params.push_back (e->clone_generic_param ());
+  }
+
+  // Overloaded assignment operator with vector clone
+  Struct &operator= (Struct const &other)
+  {
+    VisItem::operator= (other);
+    struct_name = other.struct_name;
+    where_clause = other.where_clause;
+    locus = other.locus;
+
+    generic_params.reserve (other.generic_params.size ());
+    for (const auto &e : other.generic_params)
+      generic_params.push_back (e->clone_generic_param ());
+
+    return *this;
+  }
+
+  // move constructors
+  Struct (Struct &&other) = default;
+  Struct &operator= (Struct &&other) = default;
+};
+
+// A single field in a struct
+struct StructField
+{
+private:
+  // bool has_outer_attributes;
+  std::vector<Attribute> outer_attrs;
+
+  // bool has_visibility;
+  Visibility visibility;
+
+  Identifier field_name;
+  std::unique_ptr<Type> field_type;
+
+  NodeId node_id;
+
+  Location locus;
+
+public:
+  // Returns whether struct field has any outer attributes.
+  bool has_outer_attributes () const { return !outer_attrs.empty (); }
+
+  // Returns whether struct field has a non-private (non-default) visibility.
+  bool has_visibility () const { return !visibility.is_error (); }
+
+  StructField (Identifier field_name, std::unique_ptr<Type> field_type,
+	       Visibility vis, Location locus,
+	       std::vector<Attribute> outer_attrs = std::vector<Attribute> ())
+    : outer_attrs (std::move (outer_attrs)), visibility (std::move (vis)),
+      field_name (std::move (field_name)), field_type (std::move (field_type)),
+      node_id (Analysis::Mappings::get ()->get_next_node_id ()), locus (locus)
+  {}
+
+  // Copy constructor
+  StructField (StructField const &other)
+    : outer_attrs (other.outer_attrs), visibility (other.visibility),
+      field_name (other.field_name), node_id (other.node_id),
+      locus (other.locus)
+  {
+    // guard to prevent null dereference
+    if (other.field_type != nullptr)
+      field_type = other.field_type->clone_type ();
+  }
+
+  ~StructField () = default;
+
+  // Overloaded assignment operator to clone
+  StructField &operator= (StructField const &other)
+  {
+    field_name = other.field_name;
+    visibility = other.visibility;
+    outer_attrs = other.outer_attrs;
+    node_id = other.node_id;
+
+    // guard to prevent null dereference
+    if (other.field_type != nullptr)
+      field_type = other.field_type->clone_type ();
+    else
+      field_type = nullptr;
+
+    return *this;
+  }
+
+  // move constructors
+  StructField (StructField &&other) = default;
+  StructField &operator= (StructField &&other) = default;
+
+  // Returns whether struct field is in an error state.
+  bool is_error () const
+  {
+    return field_name.empty () && field_type == nullptr;
+    // this should really be an or since neither are allowed
+  }
+
+  // Creates an error state struct field.
+  static StructField create_error ()
+  {
+    return StructField (std::string (""), nullptr, Visibility::create_error (),
+			Location ());
+  }
+
+  std::string as_string () const;
+
+  // 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; }
+
+  Identifier get_field_name () const { return field_name; }
+
+  Location get_locus () const { return locus; }
+
+  // TODO: is this better? Or is a "vis_block" better?
+  std::unique_ptr<Type> &get_field_type ()
+  {
+    rust_assert (field_type != nullptr);
+    return field_type;
+  }
+
+  const Visibility &get_visibility () const { return visibility; }
+
+  NodeId get_node_id () const { return node_id; }
+};
+
+// Rust struct declaration with true struct type AST node
+class StructStruct : public Struct
+{
+  std::vector<StructField> fields;
+  bool is_unit;
+
+public:
+  std::string as_string () const override;
+
+  // Mega-constructor with all possible fields
+  StructStruct (std::vector<StructField> fields, Identifier struct_name,
+		std::vector<std::unique_ptr<GenericParam>> generic_params,
+		WhereClause where_clause, bool is_unit, Visibility vis,
+		std::vector<Attribute> outer_attrs, Location locus)
+    : Struct (std::move (struct_name), std::move (generic_params),
+	      std::move (where_clause), std::move (vis), locus,
+	      std::move (outer_attrs)),
+      fields (std::move (fields)), is_unit (is_unit)
+  {}
+
+  // Unit struct constructor
+  StructStruct (Identifier struct_name,
+		std::vector<std::unique_ptr<GenericParam>> generic_params,
+		WhereClause where_clause, Visibility vis,
+		std::vector<Attribute> outer_attrs, Location locus)
+    : Struct (std::move (struct_name), std::move (generic_params),
+	      std::move (where_clause), std::move (vis), locus,
+	      std::move (outer_attrs)),
+      is_unit (true)
+  {}
+
+  /* Returns whether the struct is a unit struct - struct defined without
+   * fields. This is important because it also means an implicit constant of its
+   * type is defined. */
+  bool is_unit_struct () const { return is_unit; }
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // TODO: this mutable getter seems really dodgy. Think up better way.
+  std::vector<StructField> &get_fields () { return fields; }
+  const std::vector<StructField> &get_fields () const { return fields; }
+
+protected:
+  /* Use covariance to implement clone function as returning this object
+   * rather than base */
+  StructStruct *clone_item_impl () const override
+  {
+    return new StructStruct (*this);
+  }
+};
+
+// A single field in a tuple
+struct TupleField
+{
+private:
+  // bool has_outer_attributes;
+  std::vector<Attribute> outer_attrs;
+
+  // bool has_visibility;
+  Visibility visibility;
+
+  std::unique_ptr<Type> field_type;
+
+  NodeId node_id;
+
+  Location locus;
+
+public:
+  // Returns whether tuple field has outer attributes.
+  bool has_outer_attributes () const { return !outer_attrs.empty (); }
+
+  /* Returns whether tuple field has a non-default visibility (i.e. a public
+   * one) */
+  bool has_visibility () const { return !visibility.is_error (); }
+
+  // Complete constructor
+  TupleField (std::unique_ptr<Type> field_type, Visibility vis, Location locus,
+	      std::vector<Attribute> outer_attrs = std::vector<Attribute> ())
+    : outer_attrs (std::move (outer_attrs)), visibility (std::move (vis)),
+      field_type (std::move (field_type)),
+      node_id (Analysis::Mappings::get ()->get_next_node_id ()), locus (locus)
+  {}
+
+  // Copy constructor with clone
+  TupleField (TupleField const &other)
+    : outer_attrs (other.outer_attrs), visibility (other.visibility),
+      node_id (other.node_id), locus (other.locus)
+  {
+    // guard to prevent null dereference (only required if error)
+    if (other.field_type != nullptr)
+      field_type = other.field_type->clone_type ();
+  }
+
+  ~TupleField () = default;
+
+  // Overloaded assignment operator to clone
+  TupleField &operator= (TupleField const &other)
+  {
+    visibility = other.visibility;
+    outer_attrs = other.outer_attrs;
+    node_id = other.node_id;
+    locus = other.locus;
+
+    // guard to prevent null dereference (only required if error)
+    if (other.field_type != nullptr)
+      field_type = other.field_type->clone_type ();
+    else
+      field_type = nullptr;
+
+    return *this;
+  }
+
+  // move constructors
+  TupleField (TupleField &&other) = default;
+  TupleField &operator= (TupleField &&other) = default;
+
+  // Returns whether tuple field is in an error state.
+  bool is_error () const { return field_type == nullptr; }
+
+  // Creates an error state tuple field.
+  static TupleField create_error ()
+  {
+    return TupleField (nullptr, Visibility::create_error (), Location ());
+  }
+
+  std::string as_string () const;
+
+  NodeId get_node_id () const { return node_id; }
+
+  const Visibility &get_visibility () const { return visibility; }
+
+  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: is this better? Or is a "vis_block" better?
+  std::unique_ptr<Type> &get_field_type ()
+  {
+    rust_assert (field_type != nullptr);
+    return field_type;
+  }
+};
+
+// Rust tuple declared using struct keyword AST node
+class TupleStruct : public Struct
+{
+  std::vector<TupleField> fields;
+
+public:
+  std::string as_string () const override;
+
+  // Mega-constructor with all possible fields
+  TupleStruct (std::vector<TupleField> fields, Identifier struct_name,
+	       std::vector<std::unique_ptr<GenericParam>> generic_params,
+	       WhereClause where_clause, Visibility vis,
+	       std::vector<Attribute> outer_attrs, Location locus)
+    : Struct (std::move (struct_name), std::move (generic_params),
+	      std::move (where_clause), std::move (vis), locus,
+	      std::move (outer_attrs)),
+      fields (std::move (fields))
+  {}
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // TODO: this mutable getter seems really dodgy. Think up better way.
+  std::vector<TupleField> &get_fields () { return fields; }
+  const std::vector<TupleField> &get_fields () const { return fields; }
+
+protected:
+  /* Use covariance to implement clone function as returning this object
+   * rather than base */
+  TupleStruct *clone_item_impl () const override
+  {
+    return new TupleStruct (*this);
+  }
+};
+
+/* An item used in an "enum" tagged union - not abstract: base represents a
+ * name-only enum. EnumItems (variants) syntactically allow a Visibility
+ * annotation. */
+class EnumItem : public VisItem
+{
+  Identifier variant_name;
+
+  Location locus;
+
+public:
+  virtual ~EnumItem () {}
+
+  EnumItem (Identifier variant_name, Visibility vis,
+	    std::vector<Attribute> outer_attrs, Location locus)
+    : VisItem (std::move (vis), std::move (outer_attrs)),
+      variant_name (std::move (variant_name)), locus (locus)
+  {}
+
+  // Unique pointer custom clone function
+  std::unique_ptr<EnumItem> clone_enum_item () const
+  {
+    return std::unique_ptr<EnumItem> (clone_item_impl ());
+  }
+
+  virtual std::string as_string () const;
+
+  // not pure virtual as not abstract
+  virtual void accept_vis (ASTVisitor &vis);
+
+  Location get_locus () const { return locus; }
+
+  Identifier get_identifier () const { return variant_name; }
+
+  // Based on idea that name is never empty.
+  void mark_for_strip () { variant_name = ""; }
+  bool is_marked_for_strip () const { return variant_name.empty (); }
+
+protected:
+  EnumItem *clone_item_impl () const override { return new EnumItem (*this); }
+};
+
+// A tuple item used in an "enum" tagged union
+class EnumItemTuple : public EnumItem
+{
+  // bool has_tuple_fields;
+  std::vector<TupleField> tuple_fields;
+
+public:
+  // Returns whether tuple enum item has tuple fields.
+  bool has_tuple_fields () const { return !tuple_fields.empty (); }
+
+  EnumItemTuple (Identifier variant_name, Visibility vis,
+		 std::vector<TupleField> tuple_fields,
+		 std::vector<Attribute> outer_attrs, Location locus)
+    : EnumItem (std::move (variant_name), std::move (vis),
+		std::move (outer_attrs), locus),
+      tuple_fields (std::move (tuple_fields))
+  {}
+
+  std::string as_string () const override;
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // TODO: this mutable getter seems really dodgy. Think up better way.
+  std::vector<TupleField> &get_tuple_fields () { return tuple_fields; }
+  const std::vector<TupleField> &get_tuple_fields () const
+  {
+    return tuple_fields;
+  }
+
+protected:
+  // Clone function implementation as (not pure) virtual method
+  EnumItemTuple *clone_item_impl () const override
+  {
+    return new EnumItemTuple (*this);
+  }
+};
+
+// A struct item used in an "enum" tagged union
+class EnumItemStruct : public EnumItem
+{
+  // bool has_struct_fields;
+  std::vector<StructField> struct_fields;
+
+public:
+  // Returns whether struct enum item has struct fields.
+  bool has_struct_fields () const { return !struct_fields.empty (); }
+
+  EnumItemStruct (Identifier variant_name, Visibility vis,
+		  std::vector<StructField> struct_fields,
+		  std::vector<Attribute> outer_attrs, Location locus)
+    : EnumItem (std::move (variant_name), std::move (vis),
+		std::move (outer_attrs), locus),
+      struct_fields (std::move (struct_fields))
+  {}
+
+  std::string as_string () const override;
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // TODO: this mutable getter seems really dodgy. Think up better way.
+  std::vector<StructField> &get_struct_fields () { return struct_fields; }
+  const std::vector<StructField> &get_struct_fields () const
+  {
+    return struct_fields;
+  }
+
+protected:
+  // Clone function implementation as (not pure) virtual method
+  EnumItemStruct *clone_item_impl () const override
+  {
+    return new EnumItemStruct (*this);
+  }
+};
+
+// A discriminant (numbered enum) item used in an "enum" tagged union
+class EnumItemDiscriminant : public EnumItem
+{
+  std::unique_ptr<Expr> expression;
+
+public:
+  EnumItemDiscriminant (Identifier variant_name, Visibility vis,
+			std::unique_ptr<Expr> expr,
+			std::vector<Attribute> outer_attrs, Location locus)
+    : EnumItem (std::move (variant_name), std::move (vis),
+		std::move (outer_attrs), locus),
+      expression (std::move (expr))
+  {}
+
+  // Copy constructor with clone
+  EnumItemDiscriminant (EnumItemDiscriminant const &other)
+    : EnumItem (other), expression (other.expression->clone_expr ())
+  {}
+
+  // Overloaded assignment operator to clone
+  EnumItemDiscriminant &operator= (EnumItemDiscriminant const &other)
+  {
+    EnumItem::operator= (other);
+    expression = other.expression->clone_expr ();
+    // variant_name = other.variant_name;
+    // outer_attrs = other.outer_attrs;
+
+    return *this;
+  }
+
+  // move constructors
+  EnumItemDiscriminant (EnumItemDiscriminant &&other) = default;
+  EnumItemDiscriminant &operator= (EnumItemDiscriminant &&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_expr ()
+  {
+    rust_assert (expression != nullptr);
+    return expression;
+  }
+
+protected:
+  // Clone function implementation as (not pure) virtual method
+  EnumItemDiscriminant *clone_item_impl () const override
+  {
+    return new EnumItemDiscriminant (*this);
+  }
+};
+
+// AST node for Rust "enum" - tagged union
+class Enum : public VisItem
+{
+  Identifier enum_name;
+
+  // bool has_generics;
+  // Generics generic_params;
+  std::vector<std::unique_ptr<GenericParam>> generic_params; // inlined
+
+  // bool has_where_clause;
+  WhereClause where_clause;
+
+  std::vector<std::unique_ptr<EnumItem>> items;
+
+  Location locus;
+
+public:
+  std::string as_string () const override;
+
+  // Returns whether "enum" has generic parameters.
+  bool has_generics () const { return !generic_params.empty (); }
+
+  // Returns whether "enum" has a where clause.
+  bool has_where_clause () const { return !where_clause.is_empty (); }
+
+  /* Returns whether enum is a "zero-variant" (no possible variant) enum,
+   * which cannot be instantiated. */
+  bool is_zero_variant () const { return items.empty (); }
+
+  // Mega-constructor
+  Enum (Identifier enum_name, Visibility vis,
+	std::vector<std::unique_ptr<GenericParam>> generic_params,
+	WhereClause where_clause, std::vector<std::unique_ptr<EnumItem>> items,
+	std::vector<Attribute> outer_attrs, Location locus)
+    : VisItem (std::move (vis), std::move (outer_attrs)),
+      enum_name (std::move (enum_name)),
+      generic_params (std::move (generic_params)),
+      where_clause (std::move (where_clause)), items (std::move (items)),
+      locus (locus)
+  {}
+
+  // TODO: constructor with less arguments
+
+  // Copy constructor with vector clone
+  Enum (Enum const &other)
+    : VisItem (other), enum_name (other.enum_name),
+      where_clause (other.where_clause), locus (other.locus)
+  {
+    generic_params.reserve (other.generic_params.size ());
+    for (const auto &e : other.generic_params)
+      generic_params.push_back (e->clone_generic_param ());
+
+    items.reserve (other.items.size ());
+    for (const auto &e : other.items)
+      items.push_back (e->clone_enum_item ());
+  }
+
+  // Overloaded assignment operator with vector clone
+  Enum &operator= (Enum const &other)
+  {
+    VisItem::operator= (other);
+    enum_name = other.enum_name;
+    where_clause = other.where_clause;
+    locus = other.locus;
+
+    generic_params.reserve (other.generic_params.size ());
+    for (const auto &e : other.generic_params)
+      generic_params.push_back (e->clone_generic_param ());
+
+    items.reserve (other.items.size ());
+    for (const auto &e : other.items)
+      items.push_back (e->clone_enum_item ());
+
+    return *this;
+  }
+
+  // Move constructors
+  Enum (Enum &&other) = default;
+  Enum &operator= (Enum &&other) = default;
+
+  Location get_locus () const override final { return locus; }
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  Identifier get_identifier () const { return enum_name; }
+
+  // Invalid if name is empty, so base stripping on that.
+  void mark_for_strip () override { enum_name = ""; }
+  bool is_marked_for_strip () const override { return enum_name.empty (); }
+
+  // TODO: this mutable getter seems really dodgy. Think up better way.
+  std::vector<std::unique_ptr<EnumItem>> &get_variants () { return items; }
+  const std::vector<std::unique_ptr<EnumItem>> &get_variants () const
+  {
+    return items;
+  }
+
+  std::vector<std::unique_ptr<GenericParam>> &get_generic_params ()
+  {
+    return generic_params;
+  }
+  const std::vector<std::unique_ptr<GenericParam>> &get_generic_params () const
+  {
+    return generic_params;
+  }
+
+  // TODO: is this better? Or is a "vis_block" better?
+  WhereClause &get_where_clause () { return where_clause; }
+
+protected:
+  /* Use covariance to implement clone function as returning this object
+   * rather than base */
+  Enum *clone_item_impl () const override { return new Enum (*this); }
+};
+
+// Rust untagged union used for C compat AST node
+class Union : public VisItem
+{
+  Identifier union_name;
+
+  // bool has_generics;
+  // Generics generic_params;
+  std::vector<std::unique_ptr<GenericParam>> generic_params; // inlined
+
+  // bool has_where_clause;
+  WhereClause where_clause;
+
+  std::vector<StructField> variants;
+
+  Location locus;
+
+public:
+  std::string as_string () const override;
+
+  // Returns whether union has generic params.
+  bool has_generics () const { return !generic_params.empty (); }
+
+  // Returns whether union has where clause.
+  bool has_where_clause () const { return !where_clause.is_empty (); }
+
+  Union (Identifier union_name, Visibility vis,
+	 std::vector<std::unique_ptr<GenericParam>> generic_params,
+	 WhereClause where_clause, std::vector<StructField> variants,
+	 std::vector<Attribute> outer_attrs, Location locus)
+    : VisItem (std::move (vis), std::move (outer_attrs)),
+      union_name (std::move (union_name)),
+      generic_params (std::move (generic_params)),
+      where_clause (std::move (where_clause)), variants (std::move (variants)),
+      locus (locus)
+  {}
+
+  // copy constructor with vector clone
+  Union (Union const &other)
+    : VisItem (other), union_name (other.union_name),
+      where_clause (other.where_clause), variants (other.variants),
+      locus (other.locus)
+  {
+    generic_params.reserve (other.generic_params.size ());
+    for (const auto &e : other.generic_params)
+      generic_params.push_back (e->clone_generic_param ());
+  }
+
+  // overloaded assignment operator with vector clone
+  Union &operator= (Union const &other)
+  {
+    VisItem::operator= (other);
+    union_name = other.union_name;
+    where_clause = other.where_clause;
+    variants = other.variants;
+    locus = other.locus;
+
+    generic_params.reserve (other.generic_params.size ());
+    for (const auto &e : other.generic_params)
+      generic_params.push_back (e->clone_generic_param ());
+
+    return *this;
+  }
+
+  // move constructors
+  Union (Union &&other) = default;
+  Union &operator= (Union &&other) = default;
+
+  Location get_locus () const override final { return locus; }
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // Invalid if name is empty, so base stripping on that.
+  void mark_for_strip () override { union_name = ""; }
+  bool is_marked_for_strip () const override { return union_name.empty (); }
+
+  // TODO: this mutable getter seems really dodgy. Think up better way.
+  std::vector<StructField> &get_variants () { return variants; }
+  const std::vector<StructField> &get_variants () const { return variants; }
+
+  std::vector<std::unique_ptr<GenericParam>> &get_generic_params ()
+  {
+    return generic_params;
+  }
+  const std::vector<std::unique_ptr<GenericParam>> &get_generic_params () const
+  {
+    return generic_params;
+  }
+
+  // TODO: is this better? Or is a "vis_block" better?
+  WhereClause &get_where_clause () { return where_clause; }
+
+  Identifier get_identifier () const { return union_name; }
+
+protected:
+  /* Use covariance to implement clone function as returning this object
+   * rather than base */
+  Union *clone_item_impl () const override { return new Union (*this); }
+};
+
+/* "Constant item" AST node - used for constant, compile-time expressions
+ * within module scope (like constexpr) */
+class ConstantItem : public VisItem,
+		     public InherentImplItem,
+		     public TraitImplItem
+{
+  // either has an identifier or "_" - maybe handle in identifier?
+  // bool identifier_is_underscore;
+  // if no identifier declared, identifier will be "_"
+  std::string identifier;
+
+  std::unique_ptr<Type> type;
+  std::unique_ptr<Expr> const_expr;
+
+  Location locus;
+
+public:
+  std::string as_string () const override;
+
+  ConstantItem (std::string ident, Visibility vis, std::unique_ptr<Type> type,
+		std::unique_ptr<Expr> const_expr,
+		std::vector<Attribute> outer_attrs, Location locus)
+    : VisItem (std::move (vis), std::move (outer_attrs)),
+      identifier (std::move (ident)), type (std::move (type)),
+      const_expr (std::move (const_expr)), locus (locus)
+  {}
+
+  ConstantItem (ConstantItem const &other)
+    : VisItem (other), identifier (other.identifier), locus (other.locus)
+  {
+    // guard to prevent null dereference (only required if error state)
+    if (other.type != nullptr)
+      type = other.type->clone_type ();
+    if (other.const_expr != nullptr)
+      const_expr = other.const_expr->clone_expr ();
+  }
+
+  // Overload assignment operator to clone
+  ConstantItem &operator= (ConstantItem const &other)
+  {
+    VisItem::operator= (other);
+    identifier = other.identifier;
+    locus = other.locus;
+
+    // guard to prevent null dereference (only required if error state)
+    if (other.type != nullptr)
+      type = other.type->clone_type ();
+    else
+      type = nullptr;
+    if (other.const_expr != nullptr)
+      const_expr = other.const_expr->clone_expr ();
+    else
+      const_expr = nullptr;
+
+    return *this;
+  }
+
+  // move constructors
+  ConstantItem (ConstantItem &&other) = default;
+  ConstantItem &operator= (ConstantItem &&other) = default;
+
+  /* Returns whether constant item is an "unnamed" (wildcard underscore used
+   * as identifier) constant. */
+  bool is_unnamed () const { return identifier == "_"; }
+
+  Location get_locus () const override final { return locus; }
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // Invalid if type or expression are null, so base stripping on that.
+  void mark_for_strip () override
+  {
+    type = nullptr;
+    const_expr = nullptr;
+  }
+  bool is_marked_for_strip () const override
+  {
+    return type == nullptr && const_expr == nullptr;
+  }
+
+  // TODO: is this better? Or is a "vis_block" better?
+  std::unique_ptr<Expr> &get_expr ()
+  {
+    rust_assert (const_expr != nullptr);
+    return const_expr;
+  }
+
+  // TODO: is this better? Or is a "vis_block" better?
+  std::unique_ptr<Type> &get_type ()
+  {
+    rust_assert (type != nullptr);
+    return type;
+  }
+
+  std::string get_identifier () const { return identifier; }
+
+protected:
+  /* Use covariance to implement clone function as returning this object
+   * rather than base */
+  ConstantItem *clone_item_impl () const override
+  {
+    return new ConstantItem (*this);
+  }
+
+  /* Use covariance to implement clone function as returning this object
+   * rather than base */
+  ConstantItem *clone_inherent_impl_item_impl () const override
+  {
+    return new ConstantItem (*this);
+  }
+
+  /* Use covariance to implement clone function as returning this object
+   * rather than base */
+  ConstantItem *clone_trait_impl_item_impl () const override
+  {
+    return new ConstantItem (*this);
+  }
+};
+
+/* Static item AST node - items within module scope with fixed storage
+ * duration? */
+class StaticItem : public VisItem
+{
+  bool has_mut;
+  Identifier name;
+  std::unique_ptr<Type> type;
+  std::unique_ptr<Expr> expr;
+  Location locus;
+
+public:
+  std::string as_string () const override;
+
+  StaticItem (Identifier name, bool is_mut, std::unique_ptr<Type> type,
+	      std::unique_ptr<Expr> expr, Visibility vis,
+	      std::vector<Attribute> outer_attrs, Location locus)
+    : VisItem (std::move (vis), std::move (outer_attrs)), has_mut (is_mut),
+      name (std::move (name)), type (std::move (type)), expr (std::move (expr)),
+      locus (locus)
+  {}
+
+  // Copy constructor with clone
+  StaticItem (StaticItem const &other)
+    : VisItem (other), has_mut (other.has_mut), name (other.name),
+      locus (other.locus)
+  {
+    // guard to prevent null dereference (only required if error state)
+    if (other.type != nullptr)
+      type = other.type->clone_type ();
+    if (other.expr != nullptr)
+      expr = other.expr->clone_expr ();
+  }
+
+  // Overloaded assignment operator to clone
+  StaticItem &operator= (StaticItem const &other)
+  {
+    VisItem::operator= (other);
+    name = other.name;
+    has_mut = other.has_mut;
+    locus = other.locus;
+
+    // guard to prevent null dereference (only required if error state)
+    if (other.type != nullptr)
+      type = other.type->clone_type ();
+    else
+      type = nullptr;
+    if (other.expr != nullptr)
+      expr = other.expr->clone_expr ();
+    else
+      expr = nullptr;
+
+    return *this;
+  }
+
+  // move constructors
+  StaticItem (StaticItem &&other) = default;
+  StaticItem &operator= (StaticItem &&other) = default;
+
+  Location get_locus () const override final { return locus; }
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // Invalid if type or expression are null, so base stripping on that.
+  void mark_for_strip () override
+  {
+    type = nullptr;
+    expr = nullptr;
+  }
+  bool is_marked_for_strip () const override
+  {
+    return type == nullptr && expr == nullptr;
+  }
+
+  // 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?
+  std::unique_ptr<Type> &get_type ()
+  {
+    rust_assert (type != nullptr);
+    return type;
+  }
+
+  bool is_mutable () const { return has_mut; }
+
+  Identifier get_identifier () const { return name; }
+
+protected:
+  /* Use covariance to implement clone function as returning this object
+   * rather than base */
+  StaticItem *clone_item_impl () const override
+  {
+    return new StaticItem (*this);
+  }
+};
+
+// Function declaration in traits
+struct TraitFunctionDecl
+{
+private:
+  // TODO: delete and replace with Function decl item? no as no body in this.
+  FunctionQualifiers qualifiers;
+  Identifier function_name;
+
+  // bool has_generics;
+  // Generics generic_params;
+  std::vector<std::unique_ptr<GenericParam>> generic_params; // inlined
+
+  // bool has_params;
+  // FunctionParams function_params;
+  std::vector<FunctionParam> function_params; // inlined
+
+  // bool has_return_type;
+  std::unique_ptr<Type> return_type;
+
+  // bool has_where_clause;
+  WhereClause where_clause;
+
+  // should this store location info?
+
+public:
+  // Returns whether function decl has generic parameters.
+  bool has_generics () const { return !generic_params.empty (); }
+
+  // Returns whether function decl has regular parameters.
+  bool has_params () const { return !function_params.empty (); }
+
+  // Returns whether function has return type (otherwise is void).
+  bool has_return_type () const { return return_type != nullptr; }
+
+  // Returns whether function has a where clause.
+  bool has_where_clause () const { return !where_clause.is_empty (); }
+
+  Identifier get_identifier () const { return function_name; }
+
+  // Mega-constructor
+  TraitFunctionDecl (Identifier function_name, FunctionQualifiers qualifiers,
+		     std::vector<std::unique_ptr<GenericParam>> generic_params,
+		     std::vector<FunctionParam> function_params,
+		     std::unique_ptr<Type> return_type,
+		     WhereClause where_clause)
+    : qualifiers (std::move (qualifiers)),
+      function_name (std::move (function_name)),
+      generic_params (std::move (generic_params)),
+      function_params (std::move (function_params)),
+      return_type (std::move (return_type)),
+      where_clause (std::move (where_clause))
+  {}
+
+  // Copy constructor with clone
+  TraitFunctionDecl (TraitFunctionDecl const &other)
+    : qualifiers (other.qualifiers), function_name (other.function_name),
+      function_params (other.function_params), where_clause (other.where_clause)
+  {
+    // guard to prevent nullptr dereference
+    if (other.return_type != nullptr)
+      return_type = other.return_type->clone_type ();
+
+    generic_params.reserve (other.generic_params.size ());
+    for (const auto &e : other.generic_params)
+      generic_params.push_back (e->clone_generic_param ());
+  }
+
+  ~TraitFunctionDecl () = default;
+
+  // Overloaded assignment operator with clone
+  TraitFunctionDecl &operator= (TraitFunctionDecl const &other)
+  {
+    function_name = other.function_name;
+    qualifiers = other.qualifiers;
+    function_params = other.function_params;
+    where_clause = other.where_clause;
+
+    // guard to prevent nullptr dereference
+    if (other.return_type != nullptr)
+      return_type = other.return_type->clone_type ();
+    else
+      return_type = nullptr;
+
+    generic_params.reserve (other.generic_params.size ());
+    for (const auto &e : other.generic_params)
+      generic_params.push_back (e->clone_generic_param ());
+
+    return *this;
+  }
+
+  // move constructors
+  TraitFunctionDecl (TraitFunctionDecl &&other) = default;
+  TraitFunctionDecl &operator= (TraitFunctionDecl &&other) = default;
+
+  std::string as_string () const;
+
+  // Invalid if function name is empty, so base stripping on that.
+  void mark_for_strip () { function_name = ""; }
+  bool is_marked_for_strip () const { return function_name.empty (); }
+
+  // TODO: this mutable getter seems really dodgy. Think up better way.
+  std::vector<FunctionParam> &get_function_params () { return function_params; }
+  const std::vector<FunctionParam> &get_function_params () const
+  {
+    return function_params;
+  }
+
+  std::vector<std::unique_ptr<GenericParam>> &get_generic_params ()
+  {
+    return generic_params;
+  }
+  const std::vector<std::unique_ptr<GenericParam>> &get_generic_params () const
+  {
+    return generic_params;
+  }
+
+  // TODO: is this better? Or is a "vis_block" better?
+  std::unique_ptr<Type> &get_return_type () { return return_type; }
+
+  // TODO: is this better? Or is a "vis_block" better?
+  WhereClause &get_where_clause () { return where_clause; }
+
+  FunctionQualifiers get_qualifiers () { return qualifiers; }
+};
+
+// Actual trait item function declaration within traits
+class TraitItemFunc : public TraitItem
+{
+  std::vector<Attribute> outer_attrs;
+  TraitFunctionDecl decl;
+  std::unique_ptr<BlockExpr> block_expr;
+  Location locus;
+
+public:
+  // Returns whether function has a definition or is just a declaration.
+  bool has_definition () const { return block_expr != nullptr; }
+
+  TraitItemFunc (TraitFunctionDecl decl, std::unique_ptr<BlockExpr> block_expr,
+		 std::vector<Attribute> outer_attrs, Location locus)
+    : TraitItem (), outer_attrs (std::move (outer_attrs)),
+      decl (std::move (decl)), block_expr (std::move (block_expr)),
+      locus (locus)
+  {}
+
+  // Copy constructor with clone
+  TraitItemFunc (TraitItemFunc const &other)
+    : outer_attrs (other.outer_attrs), decl (other.decl), locus (other.locus)
+  {
+    node_id = other.node_id;
+
+    // guard to prevent null dereference
+    if (other.block_expr != nullptr)
+      block_expr = other.block_expr->clone_block_expr ();
+  }
+
+  // Overloaded assignment operator to clone
+  TraitItemFunc &operator= (TraitItemFunc const &other)
+  {
+    TraitItem::operator= (other);
+    outer_attrs = other.outer_attrs;
+    decl = other.decl;
+    locus = other.locus;
+    node_id = other.node_id;
+
+    // guard to prevent null dereference
+    if (other.block_expr != nullptr)
+      block_expr = other.block_expr->clone_block_expr ();
+    else
+      block_expr = nullptr;
+
+    return *this;
+  }
+
+  // move constructors
+  TraitItemFunc (TraitItemFunc &&other) = default;
+  TraitItemFunc &operator= (TraitItemFunc &&other) = default;
+
+  std::string as_string () const override;
+
+  Location get_locus () const { return locus; }
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // Invalid if trait decl is empty, so base stripping on that.
+  void mark_for_strip () override { decl.mark_for_strip (); }
+  bool is_marked_for_strip () const override
+  {
+    return decl.is_marked_for_strip ();
+  }
+
+  // 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<BlockExpr> &get_definition () { return block_expr; }
+
+  // TODO: is this better? Or is a "vis_block" better?
+  TraitFunctionDecl &get_trait_function_decl ()
+  {
+    // TODO: maybe only allow access if not marked for strip?
+    return decl;
+  }
+
+protected:
+  // Clone function implementation as (not pure) virtual method
+  TraitItemFunc *clone_trait_item_impl () const override
+  {
+    return new TraitItemFunc (*this);
+  }
+};
+
+// Method declaration within traits
+struct TraitMethodDecl
+{
+private:
+  // TODO: delete and replace with Function decl item? no as no body.
+  FunctionQualifiers qualifiers;
+  Identifier function_name;
+
+  // bool has_generics;
+  // Generics generic_params;
+  std::vector<std::unique_ptr<GenericParam>> generic_params; // inlined
+
+  SelfParam self_param;
+
+  // bool has_params;
+  // FunctionParams function_params;
+  std::vector<FunctionParam> function_params; // inlined
+
+  // bool has_return_type;
+  std::unique_ptr<Type> return_type;
+
+  // bool has_where_clause;
+  WhereClause where_clause;
+
+  // should this store location info?
+
+public:
+  // Returns whether method decl has generic parameters.
+  bool has_generics () const { return !generic_params.empty (); }
+
+  // Returns whether method decl has regular parameters.
+  bool has_params () const { return !function_params.empty (); }
+
+  // Returns whether method has return type (otherwise is void).
+  bool has_return_type () const { return return_type != nullptr; }
+
+  // Returns whether method has a where clause.
+  bool has_where_clause () const { return !where_clause.is_empty (); }
+
+  Identifier get_identifier () const { return function_name; }
+
+  // Mega-constructor
+  TraitMethodDecl (Identifier function_name, FunctionQualifiers qualifiers,
+		   std::vector<std::unique_ptr<GenericParam>> generic_params,
+		   SelfParam self_param,
+		   std::vector<FunctionParam> function_params,
+		   std::unique_ptr<Type> return_type, WhereClause where_clause)
+    : qualifiers (std::move (qualifiers)),
+      function_name (std::move (function_name)),
+      generic_params (std::move (generic_params)),
+      self_param (std::move (self_param)),
+      function_params (std::move (function_params)),
+      return_type (std::move (return_type)),
+      where_clause (std::move (where_clause))
+  {}
+
+  // Copy constructor with clone
+  TraitMethodDecl (TraitMethodDecl const &other)
+    : qualifiers (other.qualifiers), function_name (other.function_name),
+      self_param (other.self_param), function_params (other.function_params),
+      where_clause (other.where_clause)
+  {
+    // guard to prevent nullptr dereference
+    if (other.return_type != nullptr)
+      return_type = other.return_type->clone_type ();
+
+    generic_params.reserve (other.generic_params.size ());
+    for (const auto &e : other.generic_params)
+      generic_params.push_back (e->clone_generic_param ());
+  }
+
+  ~TraitMethodDecl () = default;
+
+  // Overloaded assignment operator with clone
+  TraitMethodDecl &operator= (TraitMethodDecl const &other)
+  {
+    function_name = other.function_name;
+    qualifiers = other.qualifiers;
+    self_param = other.self_param;
+    function_params = other.function_params;
+    where_clause = other.where_clause;
+
+    // guard to prevent nullptr dereference
+    if (other.return_type != nullptr)
+      return_type = other.return_type->clone_type ();
+    else
+      return_type = nullptr;
+
+    generic_params.reserve (other.generic_params.size ());
+    for (const auto &e : other.generic_params)
+      generic_params.push_back (e->clone_generic_param ());
+
+    return *this;
+  }
+
+  // move constructors
+  TraitMethodDecl (TraitMethodDecl &&other) = default;
+  TraitMethodDecl &operator= (TraitMethodDecl &&other) = default;
+
+  std::string as_string () const;
+
+  // Invalid if method name is empty, so base stripping on that.
+  void mark_for_strip () { function_name = ""; }
+  bool is_marked_for_strip () const { return function_name.empty (); }
+
+  // TODO: this mutable getter seems really dodgy. Think up better way.
+  std::vector<FunctionParam> &get_function_params () { return function_params; }
+  const std::vector<FunctionParam> &get_function_params () const
+  {
+    return function_params;
+  }
+
+  std::vector<std::unique_ptr<GenericParam>> &get_generic_params ()
+  {
+    return generic_params;
+  }
+  const std::vector<std::unique_ptr<GenericParam>> &get_generic_params () const
+  {
+    return generic_params;
+  }
+
+  // TODO: is this better? Or is a "vis_block" better?
+  std::unique_ptr<Type> &get_return_type () { return return_type; }
+
+  // TODO: is this better? Or is a "vis_block" better?
+  WhereClause &get_where_clause () { return where_clause; }
+
+  SelfParam &get_self_param () { return self_param; }
+  const SelfParam &get_self_param () const { return self_param; }
+
+  FunctionQualifiers get_qualifiers () { return qualifiers; }
+};
+
+// Actual trait item method declaration within traits
+class TraitItemMethod : public TraitItem
+{
+  std::vector<Attribute> outer_attrs;
+  TraitMethodDecl decl;
+  std::unique_ptr<BlockExpr> block_expr;
+  Location locus;
+
+public:
+  // Returns whether method has a definition or is just a declaration.
+  bool has_definition () const { return block_expr != nullptr; }
+
+  TraitItemMethod (TraitMethodDecl decl, std::unique_ptr<BlockExpr> block_expr,
+		   std::vector<Attribute> outer_attrs, Location locus)
+    : TraitItem (), outer_attrs (std::move (outer_attrs)),
+      decl (std::move (decl)), block_expr (std::move (block_expr)),
+      locus (locus)
+  {}
+
+  // Copy constructor with clone
+  TraitItemMethod (TraitItemMethod const &other)
+    : outer_attrs (other.outer_attrs), decl (other.decl), locus (other.locus)
+  {
+    node_id = other.node_id;
+
+    // guard to prevent null dereference
+    if (other.block_expr != nullptr)
+      block_expr = other.block_expr->clone_block_expr ();
+  }
+
+  // Overloaded assignment operator to clone
+  TraitItemMethod &operator= (TraitItemMethod const &other)
+  {
+    TraitItem::operator= (other);
+    outer_attrs = other.outer_attrs;
+    decl = other.decl;
+    locus = other.locus;
+    node_id = other.node_id;
+
+    // guard to prevent null dereference
+    if (other.block_expr != nullptr)
+      block_expr = other.block_expr->clone_block_expr ();
+    else
+      block_expr = nullptr;
+
+    return *this;
+  }
+
+  // move constructors
+  TraitItemMethod (TraitItemMethod &&other) = default;
+  TraitItemMethod &operator= (TraitItemMethod &&other) = default;
+
+  std::string as_string () const override;
+
+  Location get_locus () const { return locus; }
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // Invalid if trait decl is empty, so base stripping on that.
+  void mark_for_strip () override { decl.mark_for_strip (); }
+  bool is_marked_for_strip () const override
+  {
+    return decl.is_marked_for_strip ();
+  }
+
+  // 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?
+  TraitMethodDecl &get_trait_method_decl ()
+  {
+    // TODO: maybe only allow access if not marked for strip?
+    return decl;
+  }
+
+  // TODO: is this better? Or is a "vis_block" better?
+  std::unique_ptr<BlockExpr> &get_definition () { return block_expr; }
+
+protected:
+  // Clone function implementation as (not pure) virtual method
+  TraitItemMethod *clone_trait_item_impl () const override
+  {
+    return new TraitItemMethod (*this);
+  }
+};
+
+// Constant item within traits
+class TraitItemConst : public TraitItem
+{
+  std::vector<Attribute> outer_attrs;
+  Identifier name;
+  std::unique_ptr<Type> type;
+
+  // bool has_expression;
+  std::unique_ptr<Expr> expr;
+
+  Location locus;
+
+public:
+  // Whether the constant item has an associated expression.
+  bool has_expression () const { return expr != nullptr; }
+
+  TraitItemConst (Identifier name, std::unique_ptr<Type> type,
+		  std::unique_ptr<Expr> expr,
+		  std::vector<Attribute> outer_attrs, Location locus)
+    : TraitItem (), outer_attrs (std::move (outer_attrs)),
+      name (std::move (name)), type (std::move (type)), expr (std::move (expr)),
+      locus (locus)
+  {}
+
+  // Copy constructor with clones
+  TraitItemConst (TraitItemConst const &other)
+    : outer_attrs (other.outer_attrs), name (other.name), locus (other.locus)
+  {
+    node_id = other.node_id;
+
+    // guard to prevent null dereference
+    if (other.expr != nullptr)
+      expr = other.expr->clone_expr ();
+
+    // guard to prevent null dereference (only for error state)
+    if (other.type != nullptr)
+      type = other.type->clone_type ();
+  }
+
+  // Overloaded assignment operator to clone
+  TraitItemConst &operator= (TraitItemConst const &other)
+  {
+    TraitItem::operator= (other);
+    outer_attrs = other.outer_attrs;
+    name = other.name;
+    locus = other.locus;
+    node_id = other.node_id;
+
+    // guard to prevent null dereference
+    if (other.expr != nullptr)
+      expr = other.expr->clone_expr ();
+    else
+      expr = nullptr;
+
+    // guard to prevent null dereference (only for error state)
+    if (other.type != nullptr)
+      type = other.type->clone_type ();
+    else
+      type = nullptr;
+
+    return *this;
+  }
+
+  // move constructors
+  TraitItemConst (TraitItemConst &&other) = default;
+  TraitItemConst &operator= (TraitItemConst &&other) = default;
+
+  std::string as_string () const override;
+
+  Location get_locus () const { return locus; }
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // Invalid if type is null, so base stripping on that.
+  void mark_for_strip () override { type = nullptr; }
+  bool is_marked_for_strip () const override { return type == 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; }
+
+  bool has_expr () const { return expr != nullptr; }
+
+  // TODO: is this better? Or is a "vis_block" better?
+  std::unique_ptr<Expr> &get_expr ()
+  {
+    rust_assert (has_expr ());
+    return expr;
+  }
+
+  // TODO: is this better? Or is a "vis_block" better?
+  std::unique_ptr<Type> &get_type ()
+  {
+    rust_assert (type != nullptr);
+    return type;
+  }
+
+  Identifier get_identifier () const { return name; }
+
+protected:
+  // Clone function implementation as (not pure) virtual method
+  TraitItemConst *clone_trait_item_impl () const override
+  {
+    return new TraitItemConst (*this);
+  }
+};
+
+// Type items within traits
+class TraitItemType : public TraitItem
+{
+  std::vector<Attribute> outer_attrs;
+
+  Identifier name;
+
+  // bool has_type_param_bounds;
+  // TypeParamBounds type_param_bounds;
+  std::vector<std::unique_ptr<TypeParamBound>>
+    type_param_bounds; // inlined form
+
+  Location locus;
+
+public:
+  // Returns whether trait item type has type param bounds.
+  bool has_type_param_bounds () const { return !type_param_bounds.empty (); }
+
+  TraitItemType (Identifier name,
+		 std::vector<std::unique_ptr<TypeParamBound>> type_param_bounds,
+		 std::vector<Attribute> outer_attrs, Location locus)
+    : TraitItem (), outer_attrs (std::move (outer_attrs)),
+      name (std::move (name)),
+      type_param_bounds (std::move (type_param_bounds)), locus (locus)
+  {}
+
+  // Copy constructor with vector clone
+  TraitItemType (TraitItemType const &other)
+    : outer_attrs (other.outer_attrs), name (other.name), locus (other.locus)
+  {
+    node_id = other.node_id;
+    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 with vector clone
+  TraitItemType &operator= (TraitItemType const &other)
+  {
+    TraitItem::operator= (other);
+    outer_attrs = other.outer_attrs;
+    name = other.name;
+    locus = other.locus;
+    node_id = other.node_id;
+
+    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;
+  }
+
+  // default move constructors
+  TraitItemType (TraitItemType &&other) = default;
+  TraitItemType &operator= (TraitItemType &&other) = default;
+
+  std::string as_string () const override;
+
+  Location get_locus () const { return locus; }
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // Invalid if name is empty, so base stripping on that.
+  void mark_for_strip () override { name = ""; }
+  bool is_marked_for_strip () const override { return 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; }
+
+  // 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;
+  }
+
+  Identifier get_identifier () const { return name; }
+
+protected:
+  // Clone function implementation as (not pure) virtual method
+  TraitItemType *clone_trait_item_impl () const override
+  {
+    return new TraitItemType (*this);
+  }
+};
+
+// Rust trait item declaration AST node
+class Trait : public VisItem
+{
+  bool has_unsafe;
+  Identifier name;
+  std::vector<std::unique_ptr<GenericParam>> generic_params;
+  std::vector<std::unique_ptr<TypeParamBound>> type_param_bounds;
+  WhereClause where_clause;
+  std::vector<Attribute> inner_attrs;
+  std::vector<std::unique_ptr<TraitItem>> trait_items;
+  Location locus;
+
+public:
+  std::string as_string () const override;
+
+  // Returns whether trait has generic parameters.
+  bool has_generics () const { return !generic_params.empty (); }
+
+  // Returns whether trait has type parameter bounds.
+  bool has_type_param_bounds () const { return !type_param_bounds.empty (); }
+
+  // Returns whether trait has where clause.
+  bool has_where_clause () const { return !where_clause.is_empty (); }
+
+  // Returns whether trait has trait items.
+  bool has_trait_items () const { return !trait_items.empty (); }
+
+  // Returns whether trait has inner attributes.
+  bool has_inner_attrs () const { return !inner_attrs.empty (); }
+
+  Identifier get_identifier () const { return name; }
+
+  bool is_unsafe () const { return has_unsafe; }
+
+  // Mega-constructor
+  Trait (Identifier name, bool is_unsafe,
+	 std::vector<std::unique_ptr<GenericParam>> generic_params,
+	 std::vector<std::unique_ptr<TypeParamBound>> type_param_bounds,
+	 WhereClause where_clause,
+	 std::vector<std::unique_ptr<TraitItem>> trait_items, Visibility vis,
+	 std::vector<Attribute> outer_attrs, std::vector<Attribute> inner_attrs,
+	 Location locus)
+    : VisItem (std::move (vis), std::move (outer_attrs)),
+      has_unsafe (is_unsafe), name (std::move (name)),
+      generic_params (std::move (generic_params)),
+      type_param_bounds (std::move (type_param_bounds)),
+      where_clause (std::move (where_clause)),
+      inner_attrs (std::move (inner_attrs)),
+      trait_items (std::move (trait_items)), locus (locus)
+  {}
+
+  // Copy constructor with vector clone
+  Trait (Trait const &other)
+    : VisItem (other), has_unsafe (other.has_unsafe), name (other.name),
+      where_clause (other.where_clause), inner_attrs (other.inner_attrs),
+      locus (other.locus)
+  {
+    generic_params.reserve (other.generic_params.size ());
+    for (const auto &e : other.generic_params)
+      generic_params.push_back (e->clone_generic_param ());
+
+    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 ());
+
+    trait_items.reserve (other.trait_items.size ());
+    for (const auto &e : other.trait_items)
+      trait_items.push_back (e->clone_trait_item ());
+  }
+
+  // Overloaded assignment operator with vector clone
+  Trait &operator= (Trait const &other)
+  {
+    VisItem::operator= (other);
+    name = other.name;
+    has_unsafe = other.has_unsafe;
+    where_clause = other.where_clause;
+    inner_attrs = other.inner_attrs;
+    locus = other.locus;
+
+    generic_params.reserve (other.generic_params.size ());
+    for (const auto &e : other.generic_params)
+      generic_params.push_back (e->clone_generic_param ());
+
+    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 ());
+
+    trait_items.reserve (other.trait_items.size ());
+    for (const auto &e : other.trait_items)
+      trait_items.push_back (e->clone_trait_item ());
+
+    return *this;
+  }
+
+  // default move constructors
+  Trait (Trait &&other) = default;
+  Trait &operator= (Trait &&other) = default;
+
+  Location get_locus () const override final { return locus; }
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // Invalid if trait name is empty, so base stripping on that.
+  void mark_for_strip () override { name = ""; }
+  bool is_marked_for_strip () const override { return name.empty (); }
+
+  // TODO: think of better way to do this
+  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<TraitItem>> &get_trait_items () const
+  {
+    return trait_items;
+  }
+  std::vector<std::unique_ptr<TraitItem>> &get_trait_items ()
+  {
+    return trait_items;
+  }
+
+  std::vector<std::unique_ptr<GenericParam>> &get_generic_params ()
+  {
+    return generic_params;
+  }
+  const std::vector<std::unique_ptr<GenericParam>> &get_generic_params () const
+  {
+    return generic_params;
+  }
+
+  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;
+  }
+
+  WhereClause &get_where_clause () { return where_clause; }
+
+  void insert_implict_self (std::unique_ptr<AST::GenericParam> &&param)
+  {
+    std::vector<std::unique_ptr<GenericParam>> new_list;
+    new_list.reserve (generic_params.size () + 1);
+
+    new_list.push_back (std::move (param));
+    for (auto &p : generic_params)
+      {
+	new_list.push_back (std::move (p));
+      }
+
+    generic_params = std::move (new_list);
+  }
+
+protected:
+  /* Use covariance to implement clone function as returning this object
+   * rather than base */
+  Trait *clone_item_impl () const override { return new Trait (*this); }
+};
+
+// Implementation item declaration AST node - abstract base class
+class Impl : public VisItem
+{
+  // must be protected to allow subclasses to access them properly
+protected:
+  // bool has_generics;
+  // Generics generic_params;
+  std::vector<std::unique_ptr<GenericParam>> generic_params; // inlined
+
+  std::unique_ptr<Type> trait_type;
+
+  // bool has_where_clause;
+  WhereClause where_clause;
+
+  // bool has_inner_attrs;
+  std::vector<Attribute> inner_attrs;
+
+private:
+  // doesn't really need to be protected as write access probably not needed
+  Location locus;
+
+public:
+  // Returns whether impl has generic parameters.
+  bool has_generics () const { return !generic_params.empty (); }
+
+  // Returns whether impl has where clause.
+  bool has_where_clause () const { return !where_clause.is_empty (); }
+
+  // Returns whether impl has inner attributes.
+  bool has_inner_attrs () const { return !inner_attrs.empty (); }
+
+  Location get_locus () const override final { return locus; }
+
+  // Invalid if trait type is null, so base stripping on that.
+  void mark_for_strip () override { trait_type = nullptr; }
+  bool is_marked_for_strip () const override { return trait_type == nullptr; }
+
+  // TODO: think of better way to do this
+  const std::vector<Attribute> &get_inner_attrs () const { return inner_attrs; }
+  std::vector<Attribute> &get_inner_attrs () { return inner_attrs; }
+
+  std::vector<std::unique_ptr<GenericParam>> &get_generic_params ()
+  {
+    return generic_params;
+  }
+  const std::vector<std::unique_ptr<GenericParam>> &get_generic_params () const
+  {
+    return generic_params;
+  }
+
+  // TODO: is this better? Or is a "vis_block" better?
+  WhereClause &get_where_clause () { return where_clause; }
+
+  // TODO: is this better? Or is a "vis_block" better?
+  std::unique_ptr<Type> &get_type ()
+  {
+    rust_assert (trait_type != nullptr);
+    return trait_type;
+  }
+
+protected:
+  // Mega-constructor
+  Impl (std::vector<std::unique_ptr<GenericParam>> generic_params,
+	std::unique_ptr<Type> trait_type, WhereClause where_clause,
+	Visibility vis, std::vector<Attribute> inner_attrs,
+	std::vector<Attribute> outer_attrs, Location locus)
+    : VisItem (std::move (vis), std::move (outer_attrs)),
+      generic_params (std::move (generic_params)),
+      trait_type (std::move (trait_type)),
+      where_clause (std::move (where_clause)),
+      inner_attrs (std::move (inner_attrs)), locus (locus)
+  {}
+
+  // Copy constructor
+  Impl (Impl const &other)
+    : VisItem (other), where_clause (other.where_clause),
+      inner_attrs (other.inner_attrs), locus (other.locus)
+  {
+    // guard to prevent null dereference (only required if error state)
+    if (other.trait_type != nullptr)
+      trait_type = other.trait_type->clone_type ();
+
+    generic_params.reserve (other.generic_params.size ());
+    for (const auto &e : other.generic_params)
+      generic_params.push_back (e->clone_generic_param ());
+  }
+
+  // Assignment operator overload with cloning
+  Impl &operator= (Impl const &other)
+  {
+    VisItem::operator= (other);
+    where_clause = other.where_clause;
+    inner_attrs = other.inner_attrs;
+    locus = other.locus;
+
+    // guard to prevent null dereference (only required if error state)
+    if (other.trait_type != nullptr)
+      trait_type = other.trait_type->clone_type ();
+    else
+      trait_type = nullptr;
+
+    generic_params.reserve (other.generic_params.size ());
+    for (const auto &e : other.generic_params)
+      generic_params.push_back (e->clone_generic_param ());
+
+    return *this;
+  }
+
+  // move constructors
+  Impl (Impl &&other) = default;
+  Impl &operator= (Impl &&other) = default;
+};
+
+// Regular "impl foo" impl block declaration AST node
+class InherentImpl : public Impl
+{
+  // bool has_impl_items;
+  std::vector<std::unique_ptr<InherentImplItem>> impl_items;
+
+public:
+  std::string as_string () const override;
+
+  // Returns whether inherent impl block has inherent impl items.
+  bool has_impl_items () const { return !impl_items.empty (); }
+
+  // Mega-constructor
+  InherentImpl (std::vector<std::unique_ptr<InherentImplItem>> impl_items,
+		std::vector<std::unique_ptr<GenericParam>> generic_params,
+		std::unique_ptr<Type> trait_type, WhereClause where_clause,
+		Visibility vis, std::vector<Attribute> inner_attrs,
+		std::vector<Attribute> outer_attrs, Location locus)
+    : Impl (std::move (generic_params), std::move (trait_type),
+	    std::move (where_clause), std::move (vis), std::move (inner_attrs),
+	    std::move (outer_attrs), locus),
+      impl_items (std::move (impl_items))
+  {}
+
+  // Copy constructor with vector clone
+  InherentImpl (InherentImpl const &other) : Impl (other)
+  {
+    impl_items.reserve (other.impl_items.size ());
+    for (const auto &e : other.impl_items)
+      impl_items.push_back (e->clone_inherent_impl_item ());
+  }
+
+  // Overloaded assignment operator with vector clone
+  InherentImpl &operator= (InherentImpl const &other)
+  {
+    Impl::operator= (other);
+
+    impl_items.reserve (other.impl_items.size ());
+    for (const auto &e : other.impl_items)
+      impl_items.push_back (e->clone_inherent_impl_item ());
+
+    return *this;
+  }
+
+  // default move constructors
+  InherentImpl (InherentImpl &&other) = default;
+  InherentImpl &operator= (InherentImpl &&other) = default;
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // TODO: think of better way to do this
+  const std::vector<std::unique_ptr<InherentImplItem>> &get_impl_items () const
+  {
+    return impl_items;
+  }
+  std::vector<std::unique_ptr<InherentImplItem>> &get_impl_items ()
+  {
+    return impl_items;
+  }
+
+protected:
+  /* Use covariance to implement clone function as returning this object
+   * rather than base */
+  InherentImpl *clone_item_impl () const override
+  {
+    return new InherentImpl (*this);
+  }
+};
+
+// The "impl footrait for foo" impl block declaration AST node
+class TraitImpl : public Impl
+{
+  bool has_unsafe;
+  bool has_exclam;
+  TypePath trait_path;
+
+  // bool has_impl_items;
+  std::vector<std::unique_ptr<TraitImplItem>> impl_items;
+
+public:
+  std::string as_string () const override;
+
+  // Returns whether trait impl has impl items.
+  bool has_impl_items () const { return !impl_items.empty (); }
+
+  // Mega-constructor
+  TraitImpl (TypePath trait_path, bool is_unsafe, bool has_exclam,
+	     std::vector<std::unique_ptr<TraitImplItem>> impl_items,
+	     std::vector<std::unique_ptr<GenericParam>> generic_params,
+	     std::unique_ptr<Type> trait_type, WhereClause where_clause,
+	     Visibility vis, std::vector<Attribute> inner_attrs,
+	     std::vector<Attribute> outer_attrs, Location locus)
+    : Impl (std::move (generic_params), std::move (trait_type),
+	    std::move (where_clause), std::move (vis), std::move (inner_attrs),
+	    std::move (outer_attrs), locus),
+      has_unsafe (is_unsafe), has_exclam (has_exclam),
+      trait_path (std::move (trait_path)), impl_items (std::move (impl_items))
+  {}
+
+  // Copy constructor with vector clone
+  TraitImpl (TraitImpl const &other)
+    : Impl (other), has_unsafe (other.has_unsafe),
+      has_exclam (other.has_exclam), trait_path (other.trait_path)
+  {
+    impl_items.reserve (other.impl_items.size ());
+    for (const auto &e : other.impl_items)
+      impl_items.push_back (e->clone_trait_impl_item ());
+  }
+
+  // Overloaded assignment operator with vector clone
+  TraitImpl &operator= (TraitImpl const &other)
+  {
+    Impl::operator= (other);
+    trait_path = other.trait_path;
+    has_unsafe = other.has_unsafe;
+    has_exclam = other.has_exclam;
+
+    impl_items.reserve (other.impl_items.size ());
+    for (const auto &e : other.impl_items)
+      impl_items.push_back (e->clone_trait_impl_item ());
+
+    return *this;
+  }
+
+  // move constructors
+  TraitImpl (TraitImpl &&other) = default;
+  TraitImpl &operator= (TraitImpl &&other) = default;
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  bool is_unsafe () const { return has_unsafe; };
+  bool is_exclam () const { return has_exclam; }
+
+  // TODO: think of better way to do this
+  const std::vector<std::unique_ptr<TraitImplItem>> &get_impl_items () const
+  {
+    return impl_items;
+  }
+  std::vector<std::unique_ptr<TraitImplItem>> &get_impl_items ()
+  {
+    return impl_items;
+  }
+
+  // TODO: is this better? Or is a "vis_block" better?
+  TypePath &get_trait_path ()
+  {
+    // TODO: assert that trait path is not empty?
+    return trait_path;
+  }
+
+protected:
+  /* Use covariance to implement clone function as returning this object
+   * rather than base */
+  TraitImpl *clone_item_impl () const override { return new TraitImpl (*this); }
+};
+
+#if 0
+// Abstract base class for an item used inside an extern block
+class ExternalItem
+{
+  // bool has_outer_attrs;
+  std::vector<Attribute> outer_attrs;
+
+  // bool has_visibility;
+  Visibility visibility;
+
+  Identifier item_name;
+  Location locus;
+
+public:
+  virtual ~ExternalItem () {}
+
+  /* TODO: spec syntax rules state that "MacroInvocationSemi" can be used as
+   * ExternalItem, but text body isn't so clear. Adding MacroInvocationSemi
+   * support would require a lot of refactoring. */
+
+  // Returns whether item has outer attributes.
+  bool has_outer_attrs () const { return !outer_attrs.empty (); }
+
+  // Returns whether item has non-default visibility.
+  bool has_visibility () const { return !visibility.is_error (); }
+
+  // Unique pointer custom clone function
+  std::unique_ptr<ExternalItem> clone_external_item () const
+  {
+    return std::unique_ptr<ExternalItem> (clone_external_item_impl ());
+  }
+
+  virtual std::string as_string () const;
+
+  Location get_locus () const override final { return locus; }
+
+  virtual void accept_vis (ASTVisitor &vis) = 0;
+
+  // TODO: make virtual? Would be more flexible.
+  // Based on idea that name should never be empty.
+  void mark_for_strip () { item_name = ""; };
+  bool is_marked_for_strip () const { return item_name.empty (); };
+
+protected:
+  ExternalItem (Identifier item_name, Visibility vis,
+		std::vector<Attribute> outer_attrs, Location locus)
+    : outer_attrs (std::move (outer_attrs)), visibility (std::move (vis)),
+      item_name (std::move (item_name)), locus (locus)
+  {}
+
+  // Copy constructor
+  ExternalItem (ExternalItem const &other)
+    : outer_attrs (other.outer_attrs), visibility (other.visibility),
+      item_name (other.item_name), locus (other.locus)
+  {}
+
+  // Overloaded assignment operator to clone
+  ExternalItem &operator= (ExternalItem const &other)
+  {
+    item_name = other.item_name;
+    visibility = other.visibility;
+    outer_attrs = other.outer_attrs;
+    locus = other.locus;
+
+    return *this;
+  }
+
+  // move constructors
+  ExternalItem (ExternalItem &&other) = default;
+  ExternalItem &operator= (ExternalItem &&other) = default;
+
+  // Clone function implementation as pure virtual method
+  virtual ExternalItem *clone_external_item_impl () const = 0;
+
+  // possibly make this public if required
+  std::string get_item_name () const { return item_name; }
+};
+#endif
+
+// A static item used in an extern block
+class ExternalStaticItem : public ExternalItem
+{
+  // bool has_outer_attrs;
+  std::vector<Attribute> outer_attrs;
+
+  // bool has_visibility;
+  Visibility visibility;
+
+  Identifier item_name;
+  Location locus;
+
+  bool has_mut;
+  std::unique_ptr<Type> item_type;
+
+public:
+  ExternalStaticItem (Identifier item_name, std::unique_ptr<Type> item_type,
+		      bool is_mut, Visibility vis,
+		      std::vector<Attribute> outer_attrs, Location locus)
+    : ExternalItem (), outer_attrs (std::move (outer_attrs)),
+      visibility (std::move (vis)), item_name (std::move (item_name)),
+      locus (locus), has_mut (is_mut), item_type (std::move (item_type))
+  {}
+
+  // Copy constructor
+  ExternalStaticItem (ExternalStaticItem const &other)
+    : outer_attrs (other.outer_attrs), visibility (other.visibility),
+      item_name (other.item_name), locus (other.locus), has_mut (other.has_mut)
+  {
+    node_id = other.node_id;
+    // guard to prevent null dereference (only required if error state)
+    if (other.item_type != nullptr)
+      item_type = other.item_type->clone_type ();
+  }
+
+  // Overloaded assignment operator to clone
+  ExternalStaticItem &operator= (ExternalStaticItem const &other)
+  {
+    node_id = other.node_id;
+    outer_attrs = other.outer_attrs;
+    visibility = other.visibility;
+    item_name = other.item_name;
+    locus = other.locus;
+    has_mut = other.has_mut;
+
+    // guard to prevent null dereference (only required if error state)
+    if (other.item_type != nullptr)
+      item_type = other.item_type->clone_type ();
+    else
+      item_type = nullptr;
+
+    return *this;
+  }
+
+  // move constructors
+  ExternalStaticItem (ExternalStaticItem &&other) = default;
+  ExternalStaticItem &operator= (ExternalStaticItem &&other) = default;
+
+  std::string as_string () const override;
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // Returns whether item has outer attributes.
+  bool has_outer_attrs () const { return !outer_attrs.empty (); }
+
+  // Returns whether item has non-default visibility.
+  bool has_visibility () const { return !visibility.is_error (); }
+
+  Location get_locus () const { return locus; }
+
+  // Based on idea that type should never be null.
+  void mark_for_strip () override { item_type = nullptr; };
+  bool is_marked_for_strip () const override { return item_type == 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<Type> &get_type ()
+  {
+    rust_assert (item_type != nullptr);
+    return item_type;
+  }
+
+  Identifier get_identifier () const { return item_name; }
+
+  const Visibility &get_visibility () const { return visibility; }
+
+  bool is_mut () const { return has_mut; }
+
+protected:
+  /* Use covariance to implement clone function as returning this object
+   * rather than base */
+  ExternalStaticItem *clone_external_item_impl () const override
+  {
+    return new ExternalStaticItem (*this);
+  }
+};
+
+// A named function parameter used in external functions
+struct NamedFunctionParam
+{
+private:
+  // bool has_name;   // otherwise is _
+  std::string name;
+
+  std::unique_ptr<Type> param_type;
+
+  // seemingly new since writing this node
+  std::vector<Attribute> outer_attrs;
+
+  NodeId node_id;
+  Location locus;
+
+public:
+  /* Returns whether the named function parameter has a name (i.e. name is not
+   * '_'). */
+  bool has_name () const { return name != "_"; }
+
+  bool has_outer_attrs () const { return !outer_attrs.empty (); }
+
+  // Returns whether the named function parameter is in an error state.
+  bool is_error () const
+  {
+    // also if identifier is "" but that is probably more costly to compute
+    return param_type == nullptr;
+  }
+
+  std::string get_name () const { return name; }
+
+  // Creates an error state named function parameter.
+  static NamedFunctionParam create_error ()
+  {
+    return NamedFunctionParam ("", nullptr, {}, Location ());
+  }
+
+  NamedFunctionParam (std::string name, std::unique_ptr<Type> param_type,
+		      std::vector<Attribute> outer_attrs, Location locus)
+    : name (std::move (name)), param_type (std::move (param_type)),
+      outer_attrs (std::move (outer_attrs)),
+      node_id (Analysis::Mappings::get ()->get_next_node_id ()), locus (locus)
+  {}
+
+  // Copy constructor
+  NamedFunctionParam (NamedFunctionParam const &other)
+    : name (other.name), outer_attrs (other.outer_attrs)
+  {
+    node_id = other.node_id;
+    // guard to prevent null dereference (only required if error state)
+    if (other.param_type != nullptr)
+      param_type = other.param_type->clone_type ();
+  }
+
+  ~NamedFunctionParam () = default;
+
+  // Overloaded assignment operator to clone
+  NamedFunctionParam &operator= (NamedFunctionParam const &other)
+  {
+    node_id = other.node_id;
+    name = other.name;
+    // has_name = other.has_name;
+    outer_attrs = other.outer_attrs;
+
+    // guard to prevent null dereference (only required if error state)
+    if (other.param_type != nullptr)
+      param_type = other.param_type->clone_type ();
+    else
+      param_type = nullptr;
+
+    return *this;
+  }
+
+  // move constructors
+  NamedFunctionParam (NamedFunctionParam &&other) = default;
+  NamedFunctionParam &operator= (NamedFunctionParam &&other) = default;
+
+  std::string as_string () const;
+
+  // Based on idea that nane should never be empty.
+  void mark_for_strip () { param_type = nullptr; };
+  bool is_marked_for_strip () const { return is_error (); };
+
+  // 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<Type> &get_type ()
+  {
+    rust_assert (param_type != nullptr);
+    return param_type;
+  }
+
+  NodeId get_node_id () const { return node_id; }
+};
+
+// A function item used in an extern block
+class ExternalFunctionItem : public ExternalItem
+{
+  // bool has_outer_attrs;
+  std::vector<Attribute> outer_attrs;
+
+  // bool has_visibility;
+  Visibility visibility;
+
+  Identifier item_name;
+  Location locus;
+
+  // bool has_generics;
+  // Generics generic_params;
+  std::vector<std::unique_ptr<GenericParam>> generic_params; // inlined
+
+  // bool has_return_type;
+  // FunctionReturnType return_type;
+  std::unique_ptr<Type> return_type; // inlined
+
+  // bool has_where_clause;
+  WhereClause where_clause;
+
+  std::vector<NamedFunctionParam> function_params;
+  bool has_variadics;
+  std::vector<Attribute> variadic_outer_attrs;
+
+public:
+  // Returns whether item has generic parameters.
+  bool has_generics () const { return !generic_params.empty (); }
+
+  // Returns whether item has a return type (otherwise void).
+  bool has_return_type () const { return return_type != nullptr; }
+
+  // Returns whether item has a where clause.
+  bool has_where_clause () const { return !where_clause.is_empty (); }
+
+  // Returns whether item has outer attributes.
+  bool has_outer_attrs () const { return !outer_attrs.empty (); }
+
+  // Returns whether item has non-default visibility.
+  bool has_visibility () const { return !visibility.is_error (); }
+
+  // Returns whether item has variadic parameters.
+  bool is_variadic () const { return has_variadics; }
+
+  // Returns whether item has outer attributes on its variadic parameters.
+  bool has_variadic_outer_attrs () const
+  {
+    return !variadic_outer_attrs.empty ();
+  }
+
+  Location get_locus () const { return locus; }
+
+  const Visibility &get_visibility () const { return visibility; }
+
+  ExternalFunctionItem (
+    Identifier item_name,
+    std::vector<std::unique_ptr<GenericParam>> generic_params,
+    std::unique_ptr<Type> return_type, WhereClause where_clause,
+    std::vector<NamedFunctionParam> function_params, bool has_variadics,
+    std::vector<Attribute> variadic_outer_attrs, Visibility vis,
+    std::vector<Attribute> outer_attrs, Location locus)
+    : ExternalItem (), outer_attrs (std::move (outer_attrs)),
+      visibility (std::move (vis)), item_name (std::move (item_name)),
+      locus (locus), generic_params (std::move (generic_params)),
+      return_type (std::move (return_type)),
+      where_clause (std::move (where_clause)),
+      function_params (std::move (function_params)),
+      has_variadics (has_variadics),
+      variadic_outer_attrs (std::move (variadic_outer_attrs))
+  {
+    // TODO: assert that if has variadic outer attrs, then has_variadics is
+    // true?
+  }
+
+  // Copy constructor with clone
+  ExternalFunctionItem (ExternalFunctionItem const &other)
+    : outer_attrs (other.outer_attrs), visibility (other.visibility),
+      item_name (other.item_name), locus (other.locus),
+      where_clause (other.where_clause),
+      function_params (other.function_params),
+      has_variadics (other.has_variadics),
+      variadic_outer_attrs (other.variadic_outer_attrs)
+  {
+    node_id = other.node_id;
+    // guard to prevent null pointer dereference
+    if (other.return_type != nullptr)
+      return_type = other.return_type->clone_type ();
+
+    generic_params.reserve (other.generic_params.size ());
+    for (const auto &e : other.generic_params)
+      generic_params.push_back (e->clone_generic_param ());
+  }
+
+  // Overloaded assignment operator with clone
+  ExternalFunctionItem &operator= (ExternalFunctionItem const &other)
+  {
+    outer_attrs = other.outer_attrs;
+    visibility = other.visibility;
+    item_name = other.item_name;
+    locus = other.locus;
+    where_clause = other.where_clause;
+    function_params = other.function_params;
+    has_variadics = other.has_variadics;
+    variadic_outer_attrs = other.variadic_outer_attrs;
+    node_id = other.node_id;
+
+    // guard to prevent null pointer dereference
+    if (other.return_type != nullptr)
+      return_type = other.return_type->clone_type ();
+    else
+      return_type = nullptr;
+
+    generic_params.reserve (other.generic_params.size ());
+    for (const auto &e : other.generic_params)
+      generic_params.push_back (e->clone_generic_param ());
+
+    return *this;
+  }
+
+  // move constructors
+  ExternalFunctionItem (ExternalFunctionItem &&other) = default;
+  ExternalFunctionItem &operator= (ExternalFunctionItem &&other) = default;
+
+  std::string as_string () const override;
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // Based on idea that nane should never be empty.
+  void mark_for_strip () override { item_name = ""; };
+  bool is_marked_for_strip () const override { return item_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<NamedFunctionParam> &get_function_params ()
+  {
+    return function_params;
+  }
+  const std::vector<NamedFunctionParam> &get_function_params () const
+  {
+    return function_params;
+  }
+
+  std::vector<std::unique_ptr<GenericParam>> &get_generic_params ()
+  {
+    return generic_params;
+  }
+  const std::vector<std::unique_ptr<GenericParam>> &get_generic_params () const
+  {
+    return generic_params;
+  }
+
+  // TODO: is this better? Or is a "vis_block" better?
+  WhereClause &get_where_clause () { return where_clause; }
+
+  // TODO: is this better? Or is a "vis_block" better?
+  std::unique_ptr<Type> &get_return_type ()
+  {
+    rust_assert (has_return_type ());
+    return return_type;
+  }
+
+  Identifier get_identifier () const { return item_name; };
+
+protected:
+  /* Use covariance to implement clone function as returning this object
+   * rather than base */
+  ExternalFunctionItem *clone_external_item_impl () const override
+  {
+    return new ExternalFunctionItem (*this);
+  }
+};
+
+// An extern block AST node
+class ExternBlock : public VisItem
+{
+  // bool has_abi;
+  std::string abi;
+
+  // bool has_inner_attrs;
+  std::vector<Attribute> inner_attrs;
+
+  // bool has_extern_items;
+  std::vector<std::unique_ptr<ExternalItem>> extern_items;
+
+  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 extern block has inner attributes.
+  bool has_inner_attrs () const { return !inner_attrs.empty (); }
+
+  // Returns whether extern block has extern items.
+  bool has_extern_items () const { return !extern_items.empty (); }
+
+  // Returns whether extern block has ABI name.
+  bool has_abi () const { return !abi.empty (); }
+
+  std::string get_abi () const { return abi; }
+
+  ExternBlock (std::string abi,
+	       std::vector<std::unique_ptr<ExternalItem>> extern_items,
+	       Visibility vis, std::vector<Attribute> inner_attrs,
+	       std::vector<Attribute> outer_attrs, Location locus)
+    : VisItem (std::move (vis), std::move (outer_attrs)), abi (std::move (abi)),
+      inner_attrs (std::move (inner_attrs)),
+      extern_items (std::move (extern_items)), locus (locus)
+  {}
+
+  // Copy constructor with vector clone
+  ExternBlock (ExternBlock const &other)
+    : VisItem (other), abi (other.abi), inner_attrs (other.inner_attrs),
+      locus (other.locus), marked_for_strip (other.marked_for_strip)
+  {
+    extern_items.reserve (other.extern_items.size ());
+    for (const auto &e : other.extern_items)
+      extern_items.push_back (e->clone_external_item ());
+  }
+
+  // Overloaded assignment operator with vector clone
+  ExternBlock &operator= (ExternBlock const &other)
+  {
+    VisItem::operator= (other);
+    abi = other.abi;
+    inner_attrs = other.inner_attrs;
+    locus = other.locus;
+    marked_for_strip = other.marked_for_strip;
+
+    extern_items.reserve (other.extern_items.size ());
+    for (const auto &e : other.extern_items)
+      extern_items.push_back (e->clone_external_item ());
+
+    return *this;
+  }
+
+  // move constructors
+  ExternBlock (ExternBlock &&other) = default;
+  ExternBlock &operator= (ExternBlock &&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: think of better way to do this
+  const std::vector<std::unique_ptr<ExternalItem>> &get_extern_items () const
+  {
+    return extern_items;
+  }
+  std::vector<std::unique_ptr<ExternalItem>> &get_extern_items ()
+  {
+    return extern_items;
+  }
+
+  // TODO: think of better way to do this
+  const std::vector<Attribute> &get_inner_attrs () const { return inner_attrs; }
+  std::vector<Attribute> &get_inner_attrs () { return inner_attrs; }
+
+protected:
+  /* Use covariance to implement clone function as returning this object
+   * rather than base */
+  ExternBlock *clone_item_impl () const override
+  {
+    return new ExternBlock (*this);
+  }
+};
+
+// Replaced with forward decls - defined in "rust-macro.h"
+class MacroItem;
+class MacroRulesDefinition;
+} // namespace AST
+} // namespace Rust
+
+#endif