gccrs: support use declaration to write the type into the correct namespace

This builds upon the previous path resolution fixes so that it returns the
resolved_node_id or UNKNOWN_NODEID on failure to resolve the use-path.
It then exports the name to the current module namespace so it can be used.

Fixes #850 #855

gcc/rust/ChangeLog:

	* ast/rust-ast.h: add const get_final_segment helper
	* hir/rust-ast-lower-enumitem.h: dont add an item mapping for enumitems
	* hir/rust-ast-lower-item.cc (ASTLoweringItem::visit): add enum to enum-items mappings
	* hir/rust-ast-lower-stmt.cc (ASTLoweringStmt::visit): likewise
	* hir/tree/rust-hir-item.h: add non const helper to get variants
	* resolve/rust-ast-resolve-item.cc (ResolveItem::visit): resolve the use declaration
	* resolve/rust-ast-resolve-path.cc (ResolvePath::resolve_path): handle self
	* resolve/rust-ast-resolve-toplevel.h: add enum item mappings to module mappings
	* typecheck/rust-hir-type-check-path.cc (TypeCheckExpr::resolve_root_path): ensure variant
	(TypeCheckExpr::resolve_segments): likewise
	* typecheck/rust-type-util.cc (query_type): lookup enum's
	* util/rust-hir-map.cc (Mappings::insert_hir_enumitem): enum item mappings
	(Mappings::lookup_hir_enumitem): likewise
	* util/rust-hir-map.h: likewise

gcc/testsuite/ChangeLog:

	* rust/compile/issue-850.rs: New test.
	* rust/compile/issue-855.rs: New test.

Signed-off-by: Philip Herron <herron.philip@googlemail.com>

4 files changed, 22 insertions, 11 deletions

diff --git a/gcc/rust/hir/rust-ast-lower-enumitem.h b/gcc/rust/hir/rust-ast-lower-enumitem.h
index cc3e9e5..a8aa45a 100644
--- a/gcc/rust/hir/rust-ast-lower-enumitem.h
+++ b/gcc/rust/hir/rust-ast-lower-enumitem.h
@@ -46,7 +46,6 @@ public:
     auto defid = resolver.translated->get_mappings ().get_defid ();
 
     resolver.mappings->insert_defid_mapping (defid, resolver.translated);
-    resolver.mappings->insert_hir_item (resolver.translated);
     resolver.mappings->insert_location (hirid,
 					resolver.translated->get_locus ());
 
diff --git a/gcc/rust/hir/rust-ast-lower-item.cc b/gcc/rust/hir/rust-ast-lower-item.cc
index 0ad4a84..eade1bc 100644
--- a/gcc/rust/hir/rust-ast-lower-item.cc
+++ b/gcc/rust/hir/rust-ast-lower-item.cc
@@ -274,11 +274,16 @@ ASTLoweringItem::visit (AST::Enum &enum_decl)
 				 mappings->get_next_hir_id (crate_num),
 				 mappings->get_next_localdef_id (crate_num));
 
-  translated = new HIR::Enum (mapping, enum_decl.get_identifier (), vis,
-			      std::move (generic_params),
-			      std::move (where_clause), /* is_unit, */
-			      std::move (items), enum_decl.get_outer_attrs (),
-			      enum_decl.get_locus ());
+  HIR::Enum *hir_enum
+    = new HIR::Enum (mapping, enum_decl.get_identifier (), vis,
+		     std::move (generic_params), std::move (where_clause),
+		     std::move (items), enum_decl.get_outer_attrs (),
+		     enum_decl.get_locus ());
+  translated = hir_enum;
+  for (auto &variant : hir_enum->get_variants ())
+    {
+      mappings->insert_hir_enumitem (hir_enum, variant.get ());
+    }
 }
 
 void
diff --git a/gcc/rust/hir/rust-ast-lower-stmt.cc b/gcc/rust/hir/rust-ast-lower-stmt.cc
index dbff8ad..5ba8db0 100644
--- a/gcc/rust/hir/rust-ast-lower-stmt.cc
+++ b/gcc/rust/hir/rust-ast-lower-stmt.cc
@@ -301,11 +301,16 @@ ASTLoweringStmt::visit (AST::Enum &enum_decl)
 				 mappings->get_next_hir_id (crate_num),
 				 mappings->get_next_localdef_id (crate_num));
 
-  translated = new HIR::Enum (mapping, enum_decl.get_identifier (), vis,
-			      std::move (generic_params),
-			      std::move (where_clause), /* is_unit, */
-			      std::move (items), enum_decl.get_outer_attrs (),
-			      enum_decl.get_locus ());
+  HIR::Enum *hir_enum
+    = new HIR::Enum (mapping, enum_decl.get_identifier (), vis,
+		     std::move (generic_params), std::move (where_clause),
+		     std::move (items), enum_decl.get_outer_attrs (),
+		     enum_decl.get_locus ());
+  translated = hir_enum;
+  for (auto &variant : hir_enum->get_variants ())
+    {
+      mappings->insert_hir_enumitem (hir_enum, variant.get ());
+    }
 }
 
 void
diff --git a/gcc/rust/hir/tree/rust-hir-item.h b/gcc/rust/hir/tree/rust-hir-item.h
index 7a2a39f..9ff9732 100644
--- a/gcc/rust/hir/tree/rust-hir-item.h
+++ b/gcc/rust/hir/tree/rust-hir-item.h
@@ -1966,6 +1966,8 @@ public:
     return items;
   }
 
+  std::vector<std::unique_ptr<EnumItem>> &get_variants () { return items; }
+
 protected:
   /* Use covariance to implement clone function as returning this object
    * rather than base */