gccrs: Add AST to HIR lowering pass

This performs the lowering of the AST to HIR. The interesting piece here is
that we desugar much of the AST as mentioned in the previous pass, but
crucially, we also strip out all code that is "marked-for-strip" which failed
cfg-expansion from the expansion pass. After this, the HIR includes all code
required to compile for this crate.

	gcc/rust/
	* hir/rust-ast-lower-base.cc: New.
	* hir/rust-ast-lower-base.h: New.
	* hir/rust-ast-lower-block.h: New.
	* hir/rust-ast-lower-enumitem.h: New.
	* hir/rust-ast-lower-expr.h: New.
	* hir/rust-ast-lower-extern.h: New.
	* hir/rust-ast-lower-implitem.h: New.
	* hir/rust-ast-lower-item.cc: New.
	* hir/rust-ast-lower-item.h: New.
	* hir/rust-ast-lower-pattern.cc: New.
	* hir/rust-ast-lower-pattern.h: New.
	* hir/rust-ast-lower-stmt.h: New.
	* hir/rust-ast-lower-struct-field-expr.h: New.
	* hir/rust-ast-lower-type.h: New.
	* hir/rust-ast-lower.cc: New.
	* hir/rust-ast-lower.h: New.
	* hir/rust-hir-dump.cc: New.
	* hir/rust-hir-dump.h: New.

1 files changed, 1078 insertions, 0 deletions

diff --git a/gcc/rust/hir/rust-ast-lower-base.cc b/gcc/rust/hir/rust-ast-lower-base.cc
new file mode 100644
index 0000000..a674617
--- /dev/null
+++ b/gcc/rust/hir/rust-ast-lower-base.cc
@@ -0,0 +1,1078 @@
+// 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/>.
+
+#include "rust-ast-lower-base.h"
+#include "rust-ast-lower-type.h"
+#include "rust-ast-lower-pattern.h"
+#include "rust-ast-lower-extern.h"
+
+namespace Rust {
+namespace HIR {
+
+void
+ASTLoweringBase::visit (AST::Token &tok)
+{}
+void
+ASTLoweringBase::visit (AST::DelimTokenTree &delim_tok_tree)
+{}
+void
+ASTLoweringBase::visit (AST::AttrInputMetaItemContainer &input)
+{}
+//  void ASTLoweringBase::visit(MetaItem& meta_item) {}
+//  void vsit(Stmt& stmt) {}
+//  void ASTLoweringBase::visit(Expr& expr) {}
+void
+ASTLoweringBase::visit (AST::IdentifierExpr &ident_expr)
+{}
+//  void ASTLoweringBase::visit(Pattern& pattern) {}
+//  void ASTLoweringBase::visit(Type& type) {}
+//  void ASTLoweringBase::visit(TypeParamBound& type_param_bound) {}
+void
+ASTLoweringBase::visit (AST::Lifetime &lifetime)
+{}
+//  void ASTLoweringBase::visit(GenericParam& generic_param) {}
+void
+ASTLoweringBase::visit (AST::LifetimeParam &lifetime_param)
+{}
+void
+ASTLoweringBase::visit (AST::ConstGenericParam &const_param)
+{}
+//  void ASTLoweringBase::visit(TraitItem& trait_item) {}
+//  void ASTLoweringBase::visit(InherentImplItem& inherent_impl_item) {}
+//  void ASTLoweringBase::visit(TraitImplItem& trait_impl_item) {}
+
+// rust-path.h
+void
+ASTLoweringBase::visit (AST::PathInExpression &path)
+{}
+void
+ASTLoweringBase::visit (AST::TypePathSegment &segment)
+{}
+void
+ASTLoweringBase::visit (AST::TypePathSegmentGeneric &segment)
+{}
+void
+ASTLoweringBase::visit (AST::TypePathSegmentFunction &segment)
+{}
+void
+ASTLoweringBase::visit (AST::TypePath &path)
+{}
+void
+ASTLoweringBase::visit (AST::QualifiedPathInExpression &path)
+{}
+void
+ASTLoweringBase::visit (AST::QualifiedPathInType &path)
+{}
+
+// rust-expr.h
+void
+ASTLoweringBase::visit (AST::LiteralExpr &expr)
+{}
+void
+ASTLoweringBase::visit (AST::AttrInputLiteral &attr_input)
+{}
+void
+ASTLoweringBase::visit (AST::MetaItemLitExpr &meta_item)
+{}
+void
+ASTLoweringBase::visit (AST::MetaItemPathLit &meta_item)
+{}
+void
+ASTLoweringBase::visit (AST::BorrowExpr &expr)
+{}
+void
+ASTLoweringBase::visit (AST::DereferenceExpr &expr)
+{}
+void
+ASTLoweringBase::visit (AST::ErrorPropagationExpr &expr)
+{}
+void
+ASTLoweringBase::visit (AST::NegationExpr &expr)
+{}
+void
+ASTLoweringBase::visit (AST::ArithmeticOrLogicalExpr &expr)
+{}
+void
+ASTLoweringBase::visit (AST::ComparisonExpr &expr)
+{}
+void
+ASTLoweringBase::visit (AST::LazyBooleanExpr &expr)
+{}
+void
+ASTLoweringBase::visit (AST::TypeCastExpr &expr)
+{}
+void
+ASTLoweringBase::visit (AST::AssignmentExpr &expr)
+{}
+void
+ASTLoweringBase::visit (AST::CompoundAssignmentExpr &expr)
+{}
+void
+ASTLoweringBase::visit (AST::GroupedExpr &expr)
+{}
+//  void ASTLoweringBase::visit(ArrayElems& elems) {}
+void
+ASTLoweringBase::visit (AST::ArrayElemsValues &elems)
+{}
+void
+ASTLoweringBase::visit (AST::ArrayElemsCopied &elems)
+{}
+void
+ASTLoweringBase::visit (AST::ArrayExpr &expr)
+{}
+void
+ASTLoweringBase::visit (AST::ArrayIndexExpr &expr)
+{}
+void
+ASTLoweringBase::visit (AST::TupleExpr &expr)
+{}
+void
+ASTLoweringBase::visit (AST::TupleIndexExpr &expr)
+{}
+void
+ASTLoweringBase::visit (AST::StructExprStruct &expr)
+{}
+//  void ASTLoweringBase::visit(StructExprField& field) {}
+void
+ASTLoweringBase::visit (AST::StructExprFieldIdentifier &field)
+{}
+void
+ASTLoweringBase::visit (AST::StructExprFieldIdentifierValue &field)
+{}
+void
+ASTLoweringBase::visit (AST::StructExprFieldIndexValue &field)
+{}
+void
+ASTLoweringBase::visit (AST::StructExprStructFields &expr)
+{}
+void
+ASTLoweringBase::visit (AST::StructExprStructBase &expr)
+{}
+void
+ASTLoweringBase::visit (AST::CallExpr &expr)
+{}
+void
+ASTLoweringBase::visit (AST::MethodCallExpr &expr)
+{}
+void
+ASTLoweringBase::visit (AST::FieldAccessExpr &expr)
+{}
+void
+ASTLoweringBase::visit (AST::ClosureExprInner &expr)
+{}
+void
+ASTLoweringBase::visit (AST::BlockExpr &expr)
+{}
+void
+ASTLoweringBase::visit (AST::ClosureExprInnerTyped &expr)
+{}
+void
+ASTLoweringBase::visit (AST::ContinueExpr &expr)
+{}
+void
+ASTLoweringBase::visit (AST::BreakExpr &expr)
+{}
+void
+ASTLoweringBase::visit (AST::RangeFromToExpr &expr)
+{}
+void
+ASTLoweringBase::visit (AST::RangeFromExpr &expr)
+{}
+void
+ASTLoweringBase::visit (AST::RangeToExpr &expr)
+{}
+void
+ASTLoweringBase::visit (AST::RangeFullExpr &expr)
+{}
+void
+ASTLoweringBase::visit (AST::RangeFromToInclExpr &expr)
+{}
+void
+ASTLoweringBase::visit (AST::RangeToInclExpr &expr)
+{}
+void
+ASTLoweringBase::visit (AST::ReturnExpr &expr)
+{}
+void
+ASTLoweringBase::visit (AST::UnsafeBlockExpr &expr)
+{}
+void
+ASTLoweringBase::visit (AST::LoopExpr &expr)
+{}
+void
+ASTLoweringBase::visit (AST::WhileLoopExpr &expr)
+{}
+void
+ASTLoweringBase::visit (AST::WhileLetLoopExpr &expr)
+{}
+void
+ASTLoweringBase::visit (AST::ForLoopExpr &expr)
+{}
+void
+ASTLoweringBase::visit (AST::IfExpr &expr)
+{}
+void
+ASTLoweringBase::visit (AST::IfExprConseqElse &expr)
+{}
+void
+ASTLoweringBase::visit (AST::IfExprConseqIf &expr)
+{}
+void
+ASTLoweringBase::visit (AST::IfExprConseqIfLet &expr)
+{}
+void
+ASTLoweringBase::visit (AST::IfLetExpr &expr)
+{}
+void
+ASTLoweringBase::visit (AST::IfLetExprConseqElse &expr)
+{}
+void
+ASTLoweringBase::visit (AST::IfLetExprConseqIf &expr)
+{}
+void
+ASTLoweringBase::visit (AST::IfLetExprConseqIfLet &expr)
+{}
+//  void ASTLoweringBase::visit(MatchCase& match_case) {}
+// void ASTLoweringBase:: (AST::MatchCaseBlockExpr &match_case) {}
+// void ASTLoweringBase:: (AST::MatchCaseExpr &match_case) {}
+void
+ASTLoweringBase::visit (AST::MatchExpr &expr)
+{}
+void
+ASTLoweringBase::visit (AST::AwaitExpr &expr)
+{}
+void
+ASTLoweringBase::visit (AST::AsyncBlockExpr &expr)
+{}
+
+// rust-item.h
+void
+ASTLoweringBase::visit (AST::TypeParam &param)
+{}
+//  void ASTLoweringBase::visit(WhereClauseItem& item) {}
+void
+ASTLoweringBase::visit (AST::LifetimeWhereClauseItem &item)
+{}
+void
+ASTLoweringBase::visit (AST::TypeBoundWhereClauseItem &item)
+{}
+void
+ASTLoweringBase::visit (AST::Method &method)
+{}
+void
+ASTLoweringBase::visit (AST::Module &module)
+{}
+void
+ASTLoweringBase::visit (AST::ExternCrate &crate)
+{}
+//  void ASTLoweringBase::visit(UseTree& use_tree) {}
+void
+ASTLoweringBase::visit (AST::UseTreeGlob &use_tree)
+{}
+void
+ASTLoweringBase::visit (AST::UseTreeList &use_tree)
+{}
+void
+ASTLoweringBase::visit (AST::UseTreeRebind &use_tree)
+{}
+void
+ASTLoweringBase::visit (AST::UseDeclaration &use_decl)
+{}
+void
+ASTLoweringBase::visit (AST::Function &function)
+{}
+void
+ASTLoweringBase::visit (AST::TypeAlias &type_alias)
+{}
+void
+ASTLoweringBase::visit (AST::StructStruct &struct_item)
+{}
+void
+ASTLoweringBase::visit (AST::TupleStruct &tuple_struct)
+{}
+void
+ASTLoweringBase::visit (AST::EnumItem &item)
+{}
+void
+ASTLoweringBase::visit (AST::EnumItemTuple &item)
+{}
+void
+ASTLoweringBase::visit (AST::EnumItemStruct &item)
+{}
+void
+ASTLoweringBase::visit (AST::EnumItemDiscriminant &item)
+{}
+void
+ASTLoweringBase::visit (AST::Enum &enum_item)
+{}
+void
+ASTLoweringBase::visit (AST::Union &union_item)
+{}
+void
+ASTLoweringBase::visit (AST::ConstantItem &const_item)
+{}
+void
+ASTLoweringBase::visit (AST::StaticItem &static_item)
+{}
+void
+ASTLoweringBase::visit (AST::TraitItemFunc &item)
+{}
+void
+ASTLoweringBase::visit (AST::TraitItemMethod &item)
+{}
+void
+ASTLoweringBase::visit (AST::TraitItemConst &item)
+{}
+void
+ASTLoweringBase::visit (AST::TraitItemType &item)
+{}
+void
+ASTLoweringBase::visit (AST::Trait &trait)
+{}
+void
+ASTLoweringBase::visit (AST::InherentImpl &impl)
+{}
+void
+ASTLoweringBase::visit (AST::TraitImpl &impl)
+{}
+//  void ASTLoweringBase::visit(ExternalItem& item) {}
+void
+ASTLoweringBase::visit (AST::ExternalStaticItem &item)
+{}
+void
+ASTLoweringBase::visit (AST::ExternalFunctionItem &item)
+{}
+void
+ASTLoweringBase::visit (AST::ExternBlock &block)
+{}
+
+// rust-macro.h
+void
+ASTLoweringBase::visit (AST::MacroMatchFragment &match)
+{}
+void
+ASTLoweringBase::visit (AST::MacroMatchRepetition &match)
+{}
+void
+ASTLoweringBase::visit (AST::MacroMatcher &matcher)
+{}
+void
+ASTLoweringBase::visit (AST::MacroRulesDefinition &rules_def)
+{}
+void
+ASTLoweringBase::visit (AST::MacroInvocation &macro_invoc)
+{}
+void
+ASTLoweringBase::visit (AST::MetaItemPath &meta_item)
+{}
+void
+ASTLoweringBase::visit (AST::MetaItemSeq &meta_item)
+{}
+void
+ASTLoweringBase::visit (AST::MetaWord &meta_item)
+{}
+void
+ASTLoweringBase::visit (AST::MetaNameValueStr &meta_item)
+{}
+void
+ASTLoweringBase::visit (AST::MetaListPaths &meta_item)
+{}
+void
+ASTLoweringBase::visit (AST::MetaListNameValueStr &meta_item)
+{}
+
+// rust-pattern.h
+void
+ASTLoweringBase::visit (AST::LiteralPattern &pattern)
+{}
+void
+ASTLoweringBase::visit (AST::IdentifierPattern &pattern)
+{}
+void
+ASTLoweringBase::visit (AST::WildcardPattern &pattern)
+{}
+//  void ASTLoweringBase::visit(RangePatternBound& bound) {}
+void
+ASTLoweringBase::visit (AST::RangePatternBoundLiteral &bound)
+{}
+void
+ASTLoweringBase::visit (AST::RangePatternBoundPath &bound)
+{}
+void
+ASTLoweringBase::visit (AST::RangePatternBoundQualPath &bound)
+{}
+void
+ASTLoweringBase::visit (AST::RangePattern &pattern)
+{}
+void
+ASTLoweringBase::visit (AST::ReferencePattern &pattern)
+{}
+//  void ASTLoweringBase::visit(StructPatternField& field) {}
+void
+ASTLoweringBase::visit (AST::StructPatternFieldTuplePat &field)
+{}
+void
+ASTLoweringBase::visit (AST::StructPatternFieldIdentPat &field)
+{}
+void
+ASTLoweringBase::visit (AST::StructPatternFieldIdent &field)
+{}
+void
+ASTLoweringBase::visit (AST::StructPattern &pattern)
+{}
+//  void ASTLoweringBase::visit(TupleStructItems& tuple_items) {}
+void
+ASTLoweringBase::visit (AST::TupleStructItemsNoRange &tuple_items)
+{}
+void
+ASTLoweringBase::visit (AST::TupleStructItemsRange &tuple_items)
+{}
+void
+ASTLoweringBase::visit (AST::TupleStructPattern &pattern)
+{}
+//  void ASTLoweringBase::visit(TuplePatternItems& tuple_items) {}
+void
+ASTLoweringBase::visit (AST::TuplePatternItemsMultiple &tuple_items)
+{}
+void
+ASTLoweringBase::visit (AST::TuplePatternItemsRanged &tuple_items)
+{}
+void
+ASTLoweringBase::visit (AST::TuplePattern &pattern)
+{}
+void
+ASTLoweringBase::visit (AST::GroupedPattern &pattern)
+{}
+void
+ASTLoweringBase::visit (AST::SlicePattern &pattern)
+{}
+
+// rust-stmt.h
+void
+ASTLoweringBase::visit (AST::EmptyStmt &stmt)
+{}
+void
+ASTLoweringBase::visit (AST::LetStmt &stmt)
+{}
+void
+ASTLoweringBase::visit (AST::ExprStmtWithoutBlock &stmt)
+{}
+void
+ASTLoweringBase::visit (AST::ExprStmtWithBlock &stmt)
+{}
+
+// rust-type.h
+void
+ASTLoweringBase::visit (AST::TraitBound &bound)
+{}
+void
+ASTLoweringBase::visit (AST::ImplTraitType &type)
+{}
+void
+ASTLoweringBase::visit (AST::TraitObjectType &type)
+{}
+void
+ASTLoweringBase::visit (AST::ParenthesisedType &type)
+{}
+void
+ASTLoweringBase::visit (AST::ImplTraitTypeOneBound &type)
+{}
+void
+ASTLoweringBase::visit (AST::TraitObjectTypeOneBound &type)
+{}
+void
+ASTLoweringBase::visit (AST::TupleType &type)
+{}
+void
+ASTLoweringBase::visit (AST::NeverType &type)
+{}
+void
+ASTLoweringBase::visit (AST::RawPointerType &type)
+{}
+void
+ASTLoweringBase::visit (AST::ReferenceType &type)
+{}
+void
+ASTLoweringBase::visit (AST::ArrayType &type)
+{}
+void
+ASTLoweringBase::visit (AST::SliceType &type)
+{}
+void
+ASTLoweringBase::visit (AST::InferredType &type)
+{}
+void
+ASTLoweringBase::visit (AST::BareFunctionType &type)
+{}
+
+HIR::Lifetime
+ASTLoweringBase::lower_lifetime (AST::Lifetime &lifetime)
+{
+  auto crate_num = mappings->get_current_crate ();
+  Analysis::NodeMapping mapping (crate_num, lifetime.get_node_id (),
+				 mappings->get_next_hir_id (crate_num),
+				 UNKNOWN_LOCAL_DEFID);
+  mappings->insert_node_to_hir (mapping.get_nodeid (), mapping.get_hirid ());
+
+  return HIR::Lifetime (mapping, lifetime.get_lifetime_type (),
+			lifetime.get_lifetime_name (), lifetime.get_locus ());
+}
+
+HIR::LoopLabel
+ASTLoweringBase::lower_loop_label (AST::LoopLabel &loop_label)
+{
+  HIR::Lifetime life = lower_lifetime (loop_label.get_lifetime ());
+
+  auto crate_num = mappings->get_current_crate ();
+  Analysis::NodeMapping mapping (crate_num, loop_label.get_node_id (),
+				 mappings->get_next_hir_id (crate_num),
+				 UNKNOWN_LOCAL_DEFID);
+  mappings->insert_node_to_hir (mapping.get_nodeid (), mapping.get_hirid ());
+
+  return HIR::LoopLabel (mapping, std::move (life), loop_label.get_locus ());
+}
+
+std::vector<std::unique_ptr<HIR::GenericParam>>
+ASTLoweringBase::lower_generic_params (
+  std::vector<std::unique_ptr<AST::GenericParam>> &params)
+{
+  std::vector<std::unique_ptr<HIR::GenericParam>> lowered;
+  for (auto &ast_param : params)
+    {
+      auto hir_param = ASTLowerGenericParam::translate (ast_param.get ());
+      lowered.push_back (std::unique_ptr<HIR::GenericParam> (hir_param));
+    }
+
+  return lowered;
+}
+
+HIR::PathExprSegment
+ASTLoweringBase::lower_path_expr_seg (AST::PathExprSegment &s)
+{
+  auto crate_num = mappings->get_current_crate ();
+  Analysis::NodeMapping mapping (crate_num, s.get_node_id (),
+				 mappings->get_next_hir_id (crate_num),
+				 UNKNOWN_LOCAL_DEFID);
+
+  return HIR::PathExprSegment (
+    std::move (mapping),
+    HIR::PathIdentSegment (s.get_ident_segment ().as_string ()), s.get_locus (),
+    s.has_generic_args () ? lower_generic_args (s.get_generic_args ())
+			  : HIR::GenericArgs::create_empty ());
+}
+
+HIR::GenericArgsBinding
+ASTLoweringBase::lower_binding (AST::GenericArgsBinding &binding)
+{
+  HIR::Type *lowered_type
+    = ASTLoweringType::translate (binding.get_type ().get ());
+  return HIR::GenericArgsBinding (binding.get_identifier (),
+				  std::unique_ptr<HIR::Type> (lowered_type),
+				  binding.get_locus ());
+}
+
+HIR::GenericArgs
+ASTLoweringBase::lower_generic_args (AST::GenericArgs &args)
+{
+  std::vector<HIR::GenericArgsBinding> binding_args;
+  for (auto &binding : args.get_binding_args ())
+    {
+      HIR::GenericArgsBinding b = lower_binding (binding);
+      binding_args.push_back (std::move (b));
+    }
+
+  std::vector<HIR::Lifetime> lifetime_args;
+  for (auto &lifetime : args.get_lifetime_args ())
+    {
+      HIR::Lifetime l = lower_lifetime (lifetime);
+      lifetime_args.push_back (std::move (l));
+    }
+
+  std::vector<std::unique_ptr<HIR::Type>> type_args;
+  std::vector<HIR::ConstGenericArg> const_args;
+
+  for (auto &arg : args.get_generic_args ())
+    {
+      switch (arg.get_kind ())
+	{
+	  case AST::GenericArg::Kind::Type: {
+	    auto type = ASTLoweringType::translate (arg.get_type ().get ());
+	    type_args.emplace_back (std::unique_ptr<HIR::Type> (type));
+	    break;
+	  }
+	  case AST::GenericArg::Kind::Const: {
+	    auto expr
+	      = ASTLoweringExpr::translate (arg.get_expression ().get ());
+	    const_args.emplace_back (
+	      HIR::ConstGenericArg (std::unique_ptr<HIR::Expr> (expr),
+				    expr->get_locus ()));
+	    break;
+	  }
+	default:
+	  gcc_unreachable ();
+	}
+    }
+
+  return HIR::GenericArgs (std::move (lifetime_args), std::move (type_args),
+			   std::move (binding_args), std::move (const_args),
+			   args.get_locus ());
+}
+
+HIR::SelfParam
+ASTLoweringBase::lower_self (AST::SelfParam &self)
+{
+  auto crate_num = mappings->get_current_crate ();
+  Analysis::NodeMapping mapping (crate_num, self.get_node_id (),
+				 mappings->get_next_hir_id (crate_num),
+				 mappings->get_next_localdef_id (crate_num));
+
+  if (self.has_type ())
+    {
+      HIR::Type *type = ASTLoweringType::translate (self.get_type ().get ());
+      return HIR::SelfParam (mapping, std::unique_ptr<HIR::Type> (type),
+			     self.get_is_mut (), self.get_locus ());
+    }
+  else if (!self.get_has_ref ())
+    {
+      return HIR::SelfParam (mapping, std::unique_ptr<HIR::Type> (nullptr),
+			     self.get_is_mut (), self.get_locus ());
+    }
+
+  AST::Lifetime l = self.get_lifetime ();
+  return HIR::SelfParam (mapping, lower_lifetime (l), self.get_is_mut (),
+			 self.get_locus ());
+}
+
+void
+ASTLowerTypePath::visit (AST::TypePathSegmentGeneric &segment)
+{
+  std::vector<HIR::GenericArgsBinding> binding_args; // TODO
+
+  std::string segment_name = segment.get_ident_segment ().as_string ();
+  bool has_separating_scope_resolution
+    = segment.get_separating_scope_resolution ();
+
+  auto generic_args = lower_generic_args (segment.get_generic_args ());
+
+  auto crate_num = mappings->get_current_crate ();
+  auto hirid = mappings->get_next_hir_id (crate_num);
+  Analysis::NodeMapping mapping (crate_num, segment.get_node_id (), hirid,
+				 UNKNOWN_LOCAL_DEFID);
+
+  translated_segment
+    = new HIR::TypePathSegmentGeneric (std::move (mapping), segment_name,
+				       has_separating_scope_resolution,
+				       generic_args, segment.get_locus ());
+}
+
+void
+ASTLowerQualifiedPathInType::visit (AST::QualifiedPathInType &path)
+{
+  auto crate_num = mappings->get_current_crate ();
+  auto hirid = mappings->get_next_hir_id (crate_num);
+  Analysis::NodeMapping qual_mappings (
+    crate_num, path.get_qualified_path_type ().get_node_id (), hirid,
+    UNKNOWN_LOCAL_DEFID);
+
+  HIR::Type *qual_type = ASTLoweringType::translate (
+    path.get_qualified_path_type ().get_type ().get ());
+  HIR::TypePath *qual_trait = ASTLowerTypePath::translate (
+    path.get_qualified_path_type ().get_as_type_path ());
+
+  HIR::QualifiedPathType qual_path_type (
+    qual_mappings, std::unique_ptr<HIR::Type> (qual_type),
+    std::unique_ptr<HIR::TypePath> (qual_trait),
+    path.get_qualified_path_type ().get_locus ());
+
+  translated_segment = nullptr;
+  path.get_associated_segment ()->accept_vis (*this);
+  if (translated_segment == nullptr)
+    {
+      rust_fatal_error (path.get_associated_segment ()->get_locus (),
+			"failed to translate AST TypePathSegment");
+      return;
+    }
+  std::unique_ptr<HIR::TypePathSegment> associated_segment (translated_segment);
+
+  std::vector<std::unique_ptr<HIR::TypePathSegment>> translated_segments;
+  for (auto &seg : path.get_segments ())
+    {
+      translated_segment = nullptr;
+      seg->accept_vis (*this);
+      if (translated_segment == nullptr)
+	{
+	  rust_fatal_error (seg->get_locus (),
+			    "failed to translte AST TypePathSegment");
+	}
+      translated_segments.push_back (
+	std::unique_ptr<HIR::TypePathSegment> (translated_segment));
+    }
+
+  Analysis::NodeMapping mapping (crate_num, path.get_node_id (), hirid,
+				 mappings->get_next_localdef_id (crate_num));
+  translated = new HIR::QualifiedPathInType (std::move (mapping),
+					     std::move (qual_path_type),
+					     std::move (associated_segment),
+					     std::move (translated_segments),
+					     path.get_locus ());
+}
+
+void
+ASTLoweringType::visit (AST::TraitObjectTypeOneBound &type)
+{
+  std::vector<std::unique_ptr<HIR::TypeParamBound>> bounds;
+  HIR::TypeParamBound *translated_bound
+    = ASTLoweringTypeBounds::translate (&type.get_trait_bound ());
+  bounds.push_back (std::unique_ptr<HIR::TypeParamBound> (translated_bound));
+
+  auto crate_num = mappings->get_current_crate ();
+  Analysis::NodeMapping mapping (crate_num, type.get_node_id (),
+				 mappings->get_next_hir_id (crate_num),
+				 mappings->get_next_localdef_id (crate_num));
+
+  translated = new HIR::TraitObjectType (mapping, std::move (bounds),
+					 type.get_locus (), type.is_dyn ());
+}
+
+void
+ASTLoweringType::visit (AST::TraitObjectType &type)
+{
+  std::vector<std::unique_ptr<HIR::TypeParamBound>> bounds;
+
+  for (auto &bound : type.get_type_param_bounds ())
+    {
+      HIR::TypeParamBound *translated_bound
+	= ASTLoweringTypeBounds::translate (bound.get ());
+      bounds.push_back (
+	std::unique_ptr<HIR::TypeParamBound> (translated_bound));
+    }
+
+  auto crate_num = mappings->get_current_crate ();
+  Analysis::NodeMapping mapping (crate_num, type.get_node_id (),
+				 mappings->get_next_hir_id (crate_num),
+				 mappings->get_next_localdef_id (crate_num));
+
+  translated = new HIR::TraitObjectType (mapping, std::move (bounds),
+					 type.get_locus (), type.is_dyn ());
+}
+
+HIR::Type *
+ASTLoweringBase::lower_type_no_bounds (AST::TypeNoBounds *type)
+{
+  return ASTLoweringType::translate (type);
+}
+
+HIR::TypeParamBound *
+ASTLoweringBase::lower_bound (AST::TypeParamBound *bound)
+{
+  return ASTLoweringTypeBounds::translate (bound);
+}
+
+/* Checks whether the name of a field already exists.  Returns true
+   and produces an error if so.  */
+bool
+struct_field_name_exists (std::vector<HIR::StructField> &fields,
+			  HIR::StructField &new_field)
+{
+  for (auto &field : fields)
+    {
+      if (field.get_field_name ().compare (new_field.get_field_name ()) == 0)
+	{
+	  RichLocation r (new_field.get_locus ());
+	  r.add_range (field.get_locus ());
+	  rust_error_at (r, "duplicate field name %qs",
+			 field.get_field_name ().c_str ());
+	  return true;
+	}
+    }
+  return false;
+}
+
+HIR::FunctionQualifiers
+ASTLoweringBase::lower_qualifiers (const AST::FunctionQualifiers &qualifiers)
+{
+  Unsafety unsafety
+    = qualifiers.is_unsafe () ? Unsafety::Unsafe : Unsafety::Normal;
+  bool has_extern = qualifiers.is_extern ();
+
+  ABI abi = ABI::RUST;
+  if (qualifiers.has_abi ())
+    {
+      const std::string &extern_abi = qualifiers.get_extern_abi ();
+      abi = get_abi_from_string (extern_abi);
+      if (has_extern && abi == ABI::UNKNOWN)
+	rust_error_at (qualifiers.get_locus (), "unknown ABI option");
+    }
+
+  return HIR::FunctionQualifiers (qualifiers.get_const_status (), unsafety,
+				  has_extern, abi);
+}
+
+void
+ASTLoweringBase::handle_outer_attributes (const HIR::Item &item)
+{
+  for (const auto &attr : item.get_outer_attrs ())
+    {
+      const auto &str_path = attr.get_path ().as_string ();
+      if (!is_known_attribute (str_path))
+	{
+	  rust_error_at (attr.get_locus (), "unknown attribute");
+	  continue;
+	}
+
+      bool is_lang_item = str_path.compare ("lang") == 0
+			  && attr.has_attr_input ()
+			  && attr.get_attr_input ().get_attr_input_type ()
+			       == AST::AttrInput::AttrInputType::LITERAL;
+
+      bool is_doc_item = str_path.compare ("doc") == 0;
+
+      if (is_doc_item)
+	handle_doc_item_attribute (item, attr);
+      else if (is_lang_item)
+	handle_lang_item_attribute (item, attr);
+      else if (!attribute_handled_in_another_pass (str_path))
+	{
+	  rust_error_at (attr.get_locus (), "unhandled attribute: [%s]",
+			 attr.get_path ().as_string ().c_str ());
+	}
+    }
+}
+
+void
+ASTLoweringBase::handle_doc_item_attribute (const HIR::Item &item,
+					    const AST::Attribute &attr)
+{
+  auto simple_doc_comment = attr.has_attr_input ()
+			    && attr.get_attr_input ().get_attr_input_type ()
+				 == AST::AttrInput::AttrInputType::LITERAL;
+  if (simple_doc_comment)
+    return;
+
+  const AST::AttrInput &input = attr.get_attr_input ();
+  bool is_token_tree
+    = input.get_attr_input_type () == AST::AttrInput::AttrInputType::TOKEN_TREE;
+  rust_assert (is_token_tree);
+  const auto &option = static_cast<const AST::DelimTokenTree &> (input);
+  AST::AttrInputMetaItemContainer *meta_item = option.parse_to_meta_item ();
+
+  // TODO: add actual and complete checks for the doc attributes
+  //
+  // FIXME: Move this to the AttributeChecker visitor
+  rust_assert (meta_item);
+}
+
+void
+ASTLoweringBase::handle_lang_item_attribute (const HIR::Item &item,
+					     const AST::Attribute &attr)
+{
+  auto &literal = static_cast<AST::AttrInputLiteral &> (attr.get_attr_input ());
+  const auto &lang_item_type_str = literal.get_literal ().as_string ();
+  auto lang_item_type = Analysis::RustLangItem::Parse (lang_item_type_str);
+  if (lang_item_type == Analysis::RustLangItem::ItemType::UNKNOWN)
+    {
+      rust_error_at (attr.get_locus (), "unknown lang item");
+      return;
+    }
+  mappings->insert_lang_item (lang_item_type,
+			      item.get_mappings ().get_defid ());
+}
+
+bool
+ASTLoweringBase::is_known_attribute (const std::string &attribute_path) const
+{
+  const auto &lookup = attr_mappings->lookup_builtin (attribute_path);
+  return !lookup.is_error ();
+}
+
+bool
+ASTLoweringBase::attribute_handled_in_another_pass (
+  const std::string &attribute_path) const
+{
+  const auto &lookup = attr_mappings->lookup_builtin (attribute_path);
+  if (lookup.is_error ())
+    return false;
+
+  if (lookup.handler == Analysis::CompilerPass::UNKNOWN)
+    return false;
+
+  return lookup.handler != Analysis::CompilerPass::HIR_LOWERING;
+}
+
+std::unique_ptr<HIR::TuplePatternItems>
+ASTLoweringBase::lower_tuple_pattern_multiple (
+  AST::TuplePatternItemsMultiple &pattern)
+{
+  std::vector<std::unique_ptr<HIR::Pattern>> patterns;
+  for (auto &p : pattern.get_patterns ())
+    {
+      HIR::Pattern *translated = ASTLoweringPattern::translate (p.get ());
+      patterns.push_back (std::unique_ptr<HIR::Pattern> (translated));
+    }
+
+  return std::unique_ptr<HIR::TuplePatternItems> (
+    new HIR::TuplePatternItemsMultiple (std::move (patterns)));
+}
+
+std::unique_ptr<TuplePatternItems>
+ASTLoweringBase::lower_tuple_pattern_ranged (
+  AST::TuplePatternItemsRanged &pattern)
+{
+  std::vector<std::unique_ptr<HIR::Pattern>> lower_patterns;
+  std::vector<std::unique_ptr<HIR::Pattern>> upper_patterns;
+
+  for (auto &p : pattern.get_lower_patterns ())
+    {
+      HIR::Pattern *translated = ASTLoweringPattern::translate (p.get ());
+      lower_patterns.push_back (std::unique_ptr<HIR::Pattern> (translated));
+    }
+
+  for (auto &p : pattern.get_upper_patterns ())
+    {
+      HIR::Pattern *translated = ASTLoweringPattern::translate (p.get ());
+      upper_patterns.push_back (std::unique_ptr<HIR::Pattern> (translated));
+    }
+
+  return std::unique_ptr<HIR::TuplePatternItems> (
+    new HIR::TuplePatternItemsRanged (std::move (lower_patterns),
+				      std::move (upper_patterns)));
+}
+
+std::unique_ptr<HIR::RangePatternBound>
+ASTLoweringBase::lower_range_pattern_bound (AST::RangePatternBound *bound)
+{
+  std::unique_ptr<HIR::RangePatternBound> hir_bound = nullptr;
+  switch (bound->get_bound_type ())
+    {
+      case AST::RangePatternBound::RangePatternBoundType::LITERAL: {
+	AST::RangePatternBoundLiteral &ref
+	  = *static_cast<AST::RangePatternBoundLiteral *> (bound);
+
+	HIR::Literal literal = lower_literal (ref.get_literal ());
+
+	hir_bound = std::unique_ptr<HIR::RangePatternBound> (
+	  new HIR::RangePatternBoundLiteral (literal, ref.get_locus (),
+					     ref.get_has_minus ()));
+      }
+      break;
+      case AST::RangePatternBound::RangePatternBoundType::PATH: {
+	AST::RangePatternBoundPath &ref
+	  = *static_cast<AST::RangePatternBoundPath *> (bound);
+
+	HIR::PathInExpression *path
+	  = ASTLowerPathInExpression::translate (&ref.get_path ());
+
+	hir_bound = std::unique_ptr<HIR::RangePatternBound> (
+	  new HIR::RangePatternBoundPath (*path));
+      }
+      break;
+      case AST::RangePatternBound::RangePatternBoundType::QUALPATH: {
+	AST::RangePatternBoundQualPath &ref
+	  = *static_cast<AST::RangePatternBoundQualPath *> (bound);
+
+	HIR::QualifiedPathInExpression *qualpath
+	  = ASTLowerQualPathInExpression::translate (
+	    &ref.get_qualified_path ());
+
+	hir_bound = std::unique_ptr<HIR::RangePatternBound> (
+	  new HIR::RangePatternBoundQualPath (*qualpath));
+      }
+      break;
+    }
+
+  return hir_bound;
+}
+
+HIR::Literal
+ASTLoweringBase::lower_literal (const AST::Literal &literal)
+{
+  HIR::Literal::LitType type = HIR::Literal::LitType::CHAR;
+  switch (literal.get_lit_type ())
+    {
+    case AST::Literal::LitType::CHAR:
+      type = HIR::Literal::LitType::CHAR;
+      break;
+    case AST::Literal::LitType::STRING:
+      type = HIR::Literal::LitType::STRING;
+      break;
+    case AST::Literal::LitType::BYTE:
+      type = HIR::Literal::LitType::BYTE;
+      break;
+    case AST::Literal::LitType::BYTE_STRING:
+      type = HIR::Literal::LitType::BYTE_STRING;
+      break;
+    case AST::Literal::LitType::INT:
+      type = HIR::Literal::LitType::INT;
+      break;
+    case AST::Literal::LitType::FLOAT:
+      type = HIR::Literal::LitType::FLOAT;
+      break;
+    case AST::Literal::LitType::BOOL:
+      type = HIR::Literal::LitType::BOOL;
+      break;
+    case AST::Literal::LitType::ERROR:
+      gcc_unreachable ();
+      break;
+    }
+
+  return HIR::Literal (literal.as_string (), type, literal.get_type_hint ());
+}
+
+HIR::ExternBlock *
+ASTLoweringBase::lower_extern_block (AST::ExternBlock &extern_block)
+{
+  HIR::Visibility vis = translate_visibility (extern_block.get_visibility ());
+
+  auto crate_num = mappings->get_current_crate ();
+  Analysis::NodeMapping mapping (crate_num, extern_block.get_node_id (),
+				 mappings->get_next_hir_id (crate_num),
+				 mappings->get_next_localdef_id (crate_num));
+
+  std::vector<std::unique_ptr<HIR::ExternalItem>> extern_items;
+  for (auto &item : extern_block.get_extern_items ())
+    {
+      if (item->is_marked_for_strip ())
+	continue;
+
+      HIR::ExternalItem *lowered
+	= ASTLoweringExternItem::translate (item.get (), mapping.get_hirid ());
+      extern_items.push_back (std::unique_ptr<HIR::ExternalItem> (lowered));
+    }
+
+  ABI abi = ABI::RUST;
+  if (extern_block.has_abi ())
+    {
+      const std::string &extern_abi = extern_block.get_abi ();
+      abi = get_abi_from_string (extern_abi);
+      if (abi == ABI::UNKNOWN)
+	rust_error_at (extern_block.get_locus (), "unknown ABI option");
+    }
+
+  HIR::ExternBlock *hir_extern_block
+    = new HIR::ExternBlock (mapping, abi, std::move (extern_items),
+			    std::move (vis), extern_block.get_inner_attrs (),
+			    extern_block.get_outer_attrs (),
+			    extern_block.get_locus ());
+
+  mappings->insert_hir_extern_block (hir_extern_block);
+
+  return hir_extern_block;
+}
+
+} // namespace HIR
+} // namespace Rust