ast: Refactor how lang item paths are handled.

Lang item typepaths were not handled properly, and required a complete overhaul.
All old classes that concerned lang item paths are now modified to use a simpler
version of `AST::LangItemPath`, which has been removed. TypePath segments can now
be lang items, as this is requied for having generic lang item paths such as
PhantomData<T>.

gcc/rust/ChangeLog:

	* ast/rust-path.h: Rework how lang item paths are represented.
	* ast/rust-path.cc: Likewise.
	* ast/rust-item.h: Likewise.
	* ast/rust-ast.cc: Likewise.
	* ast/rust-ast-collector.cc: Adapt to new lang item path system.
	* ast/rust-ast-collector.h: Likewise.
	* ast/rust-ast-visitor.cc (DefaultASTVisitor::visit): Likewise.
	* ast/rust-ast-visitor.h: Likewise.
	* expand/rust-derive-copy.cc: Likewise.
	* expand/rust-derive.h: Likewise.
	* hir/rust-ast-lower-base.cc (ASTLoweringBase::visit): Likewise.
	* hir/rust-ast-lower-base.h: Likewise.
	* hir/rust-ast-lower-type.cc (ASTLowerTypePath::translate): Likewise.
	(ASTLowerTypePath::visit): Likewise.
	* hir/rust-ast-lower-type.h: Likewise.
	* resolve/rust-ast-resolve-base.cc (ResolverBase::visit): Likewise.
	* resolve/rust-ast-resolve-base.h: Likewise.
	* resolve/rust-ast-resolve-item.cc (ResolveItem::visit): Likewise.
	* resolve/rust-ast-resolve-type.h: Likewise.
	* resolve/rust-ast-resolve-type.cc (ResolveRelativeTypePath::go): Likewise.
	* resolve/rust-late-name-resolver-2.0.cc (Late::visit): Likewise.
	* resolve/rust-late-name-resolver-2.0.h: Likewise.
	* hir/tree/rust-hir-path.cc (TypePathSegment::TypePathSegment): Likewise.
	(TypePathSegmentGeneric::TypePathSegmentGeneric): Likewise.
	* hir/tree/rust-hir-path.h: Likewise.
	* typecheck/rust-hir-type-check-type.cc (TypeCheckType::resolve_root_path): Likewise.
	* ast/rust-ast-builder.cc: Likewise.
	* ast/rust-ast-builder.h: Likewise.

1 files changed, 9 insertions, 22 deletions

diff --git a/gcc/rust/ast/rust-path.cc b/gcc/rust/ast/rust-path.cc
index 3a7e6e3..02f1f1b 100644
--- a/gcc/rust/ast/rust-path.cc
+++ b/gcc/rust/ast/rust-path.cc
@@ -136,8 +136,11 @@ PathExprSegment::as_string () const
 }
 
 std::string
-RegularPath::as_string () const
+Path::as_string () const
 {
+  // FIXME: Impl for lang items
+  rust_assert (kind == Kind::Regular);
+
   std::string str;
 
   for (const auto &segment : segments)
@@ -149,15 +152,11 @@ RegularPath::as_string () const
   return str;
 }
 
-std::string
-LangItemPath::as_string () const
-{
-  return "#[lang = \"" + LangItem::ToString (kind) + "\"]";
-}
-
 SimplePath
-RegularPath::convert_to_simple_path (bool with_opening_scope_resolution) const
+Path::convert_to_simple_path (bool with_opening_scope_resolution) const
 {
+  rust_assert (kind == Kind::Regular);
+
   if (!has_segments ())
     return SimplePath::create_empty ();
 
@@ -191,18 +190,6 @@ RegularPath::convert_to_simple_path (bool with_opening_scope_resolution) const
 }
 
 void
-RegularPath::accept_vis (ASTVisitor &vis)
-{
-  vis.visit (*this);
-}
-
-void
-LangItemPath::accept_vis (ASTVisitor &vis)
-{
-  vis.visit (*this);
-}
-
-void
 PathInExpression::accept_vis (ASTVisitor &vis)
 {
   vis.visit (*this);
@@ -216,7 +203,7 @@ PathInExpression::as_string () const
   if (has_opening_scope_resolution)
     str = "::";
 
-  return str + path->as_string ();
+  return str + Path::as_string ();
 }
 
 std::string
@@ -316,7 +303,7 @@ TypePathFunction::as_string () const
 std::string
 QualifiedPathInExpression::as_string () const
 {
-  return path_type.as_string () + "::" + path->as_string ();
+  return path_type.as_string () + "::" + Path::as_string ();
 }
 
 std::string