Adjust external crate lowering and type checking

The 2.0 name resolver is provided through
ImmutableNameResolutionContext after it is done being mutated. The
typechecker attempts to use ImmutableNameResolutionContext, so it needs
to be run after ImmutableNameResolutionContext has been initialized
(after all name resolution has been completed). Additionally, although I
haven't seen any issues with lowering AST to HIR before name resolution
2.0 is complete, it makes sense to perform all lowering in lockstep as
well.

gcc/rust/ChangeLog:

	* hir/rust-ast-lower-item.cc (ASTLoweringItem::visit): Add
	visitor for ExternCrate.
	* hir/rust-ast-lower-item.h (ASTLoweringItem::visit): Likewise.
	* rust-session-manager.cc (Session::load_extern_crate): Avoid
	lowering or type resolving external crates here.
	* typecheck/rust-hir-type-check-item.cc (TypeCheckItem::visit):
	Add visitor for ExternCrate.
	* typecheck/rust-hir-type-check-item.h (TypeCheckItem::visit):
	Replace empty definition with a declaration.

Signed-off-by: Owen Avery <[email protected]>

Author: powerboat9

gcc/rust/hir/rust-ast-lower-item.cc

@@ -732,6 +732,25 @@ ASTLoweringItem::visit (AST::MacroRulesDefinition &def)
   lower_macro_definition (def);
 }
 
+void
+ASTLoweringItem::visit (AST::ExternCrate &extern_crate)
+{
+  if (extern_crate.references_self ())
+    return;
+
+  auto &mappings = Analysis::Mappings::get ();
+  CrateNum num
+    = mappings.lookup_crate_name (extern_crate.get_referenced_crate ())
+	.value ();
+  AST::Crate &crate = mappings.get_ast_crate (num);
+
+  auto saved_crate_num = mappings.get_current_crate ();
+  mappings.set_current_crate (num);
+  auto lowered = ASTLowering::Resolve (crate);
+  mappings.insert_hir_crate (std::move (lowered));
+  mappings.set_current_crate (saved_crate_num);
+}
+
 HIR::SimplePath
 ASTLoweringSimplePath::translate (const AST::SimplePath &path)
 {

gcc/rust/hir/rust-ast-lower-item.h

@@ -45,6 +45,7 @@ class ASTLoweringItem : public ASTLoweringBase
   void visit (AST::TraitImpl &impl_block) override;
   void visit (AST::ExternBlock &extern_block) override;
   void visit (AST::MacroRulesDefinition &rules_def) override;
+  void visit (AST::ExternCrate &extern_crate) override;
 
 private:
   ASTLoweringItem () : translated (nullptr) {}

gcc/rust/rust-session-manager.cc

@@ -1182,14 +1182,6 @@ Session::load_extern_crate (const std::string &crate_name, location_t locus)
   // name resolve it
   Resolver::NameResolution::Resolve (parsed_crate);
 
-  // perform hir lowering
-  std::unique_ptr<HIR::Crate> lowered
-    = HIR::ASTLowering::Resolve (parsed_crate);
-  HIR::Crate &hir = mappings.insert_hir_crate (std::move (lowered));
-
-  // perform type resolution
-  Resolver::TypeResolution::Resolve (hir);
-
   // always restore the crate_num
   mappings.set_current_crate (saved_crate_num);
 

gcc/rust/typecheck/rust-hir-type-check-item.cc

@@ -737,6 +737,25 @@ TypeCheckItem::visit (HIR::ExternBlock &extern_block)
     }
 }
 
+void
+TypeCheckItem::visit (HIR::ExternCrate &extern_crate)
+{
+  if (extern_crate.references_self ())
+    return;
+
+  auto &mappings = Analysis::Mappings::get ();
+  CrateNum num
+    = mappings.lookup_crate_name (extern_crate.get_referenced_crate ())
+	.value ();
+  HIR::Crate &crate = mappings.get_hir_crate (num);
+
+  CrateNum saved_crate_num = mappings.get_current_crate ();
+  mappings.set_current_crate (num);
+  for (auto &item : crate.get_items ())
+    TypeCheckItem::Resolve (*item);
+  mappings.set_current_crate (saved_crate_num);
+}
+
 std::pair<std::vector<TyTy::SubstitutionParamMapping>, TyTy::RegionConstraints>
 TypeCheckItem::resolve_impl_block_substitutions (HIR::ImplBlock &impl_block,
 						 bool &failure_flag)

gcc/rust/typecheck/rust-hir-type-check-item.h

@@ -51,9 +51,9 @@ class TypeCheckItem : private TypeCheckBase, private HIR::HIRVisItemVisitor
   void visit (HIR::ImplBlock &impl_block) override;
   void visit (HIR::ExternBlock &extern_block) override;
   void visit (HIR::Trait &trait_block) override;
+  void visit (HIR::ExternCrate &extern_crate) override;
 
   // nothing to do
-  void visit (HIR::ExternCrate &) override {}
   void visit (HIR::UseDeclaration &) override {}
 
 protected: