hir: Add ExternalTypeItem node

gcc/rust/ChangeLog:

	* hir/tree/rust-hir-item.h (class ExternalTypeItem): New class.
	* hir/tree/rust-hir.cc (ExternalTypeItem::as_string): Likewise.
	* backend/rust-compile-extern.h: Add base for handling HIR::ExternalTypeItem
	node.
	* checks/errors/borrowck/rust-bir-builder-struct.h: Likewise.
	* checks/errors/borrowck/rust-function-collector.h: Likewise.
	* checks/errors/rust-const-checker.cc (ConstChecker::visit): Likewise.
	* checks/errors/rust-const-checker.h: Likewise.
	* checks/errors/rust-unsafe-checker.cc (UnsafeChecker::visit): Likewise.
	* checks/errors/rust-unsafe-checker.h: Likewise.
	* hir/rust-ast-lower-extern.h: Likewise.
	* hir/rust-hir-dump.cc (Dump::visit): Likewise.
	* hir/rust-hir-dump.h: Likewise.
	* hir/tree/rust-hir-full-decls.h (class ExternalTypeItem): Likewise.
	* hir/tree/rust-hir-visitor.h: Likewise.
	(ExternalTypeItem::accept_vis): Likewise.
	* typecheck/rust-hir-type-check-implitem.cc (TypeCheckTopLevelExternItem::visit): Likewise.
	* typecheck/rust-hir-type-check-implitem.h: Likewise.

gcc/rust/backend/rust-compile-extern.h

@@ -22,6 +22,8 @@
 #include "rust-compile-base.h"
 #include "rust-compile-intrinsic.h"
 #include "rust-compile-type.h"
+#include "rust-diagnostics.h"
+#include "rust-hir-full-decls.h"
 
 namespace Rust {
 namespace Compile {
@@ -152,6 +154,11 @@ class CompileExternItem : public HIRCompileBase,
     reference = address_expression (fndecl, ref_locus);
   }
 
+  void visit (HIR::ExternalTypeItem &type) override
+  {
+    rust_sorry_at (type.get_locus (), "extern types are not supported yet");
+  }
+
 private:
   CompileExternItem (Context *ctx, TyTy::BaseType *concrete,
 		     location_t ref_locus)

gcc/rust/checks/errors/borrowck/rust-bir-builder-struct.h

@@ -189,6 +189,7 @@ class StructBuilder : public AbstractBuilder, public HIR::HIRFullVisitor
   void visit (HIR::ImplBlock &impl) override { rust_unreachable (); }
   void visit (HIR::ExternalStaticItem &item) override { rust_unreachable (); }
   void visit (HIR::ExternalFunctionItem &item) override { rust_unreachable (); }
+  void visit (HIR::ExternalTypeItem &item) override { rust_unreachable (); }
   void visit (HIR::ExternBlock &block) override { rust_unreachable (); }
   void visit (HIR::LiteralPattern &pattern) override { rust_unreachable (); }
   void visit (HIR::IdentifierPattern &pattern) override { rust_unreachable (); }

gcc/rust/checks/errors/borrowck/rust-function-collector.h

@@ -155,6 +155,7 @@ class FunctionCollector : public HIR::HIRFullVisitor
   void visit (HIR::ImplBlock &impl) override {}
   void visit (HIR::ExternalStaticItem &item) override {}
   void visit (HIR::ExternalFunctionItem &item) override {}
+  void visit (HIR::ExternalTypeItem &item) override {}
   void visit (HIR::ExternBlock &block) override {}
   void visit (HIR::LiteralPattern &pattern) override {}
   void visit (HIR::IdentifierPattern &pattern) override {}

gcc/rust/checks/errors/rust-const-checker.cc

@@ -714,6 +714,10 @@ void
 ConstChecker::visit (ExternalFunctionItem &)
 {}
 
+void
+ConstChecker::visit (ExternalTypeItem &)
+{}
+
 void
 ConstChecker::visit (ExternBlock &block)
 {

gcc/rust/checks/errors/rust-const-checker.h

@@ -162,6 +162,7 @@ class ConstChecker : public HIRFullVisitor
   virtual void visit (ImplBlock &impl) override;
   virtual void visit (ExternalStaticItem &item) override;
   virtual void visit (ExternalFunctionItem &item) override;
+  virtual void visit (ExternalTypeItem &item) override;
   virtual void visit (ExternBlock &block) override;
   virtual void visit (LiteralPattern &pattern) override;
   virtual void visit (IdentifierPattern &pattern) override;

gcc/rust/checks/errors/rust-unsafe-checker.cc

@@ -783,6 +783,10 @@ void
 UnsafeChecker::visit (ExternalFunctionItem &)
 {}
 
+void
+UnsafeChecker::visit (ExternalTypeItem &)
+{}
+
 void
 UnsafeChecker::visit (ExternBlock &block)
 {

gcc/rust/checks/errors/rust-unsafe-checker.h

@@ -144,6 +144,7 @@ class UnsafeChecker : public HIRFullVisitor
   virtual void visit (ImplBlock &impl) override;
   virtual void visit (ExternalStaticItem &item) override;
   virtual void visit (ExternalFunctionItem &item) override;
+  virtual void visit (ExternalTypeItem &item) override;
   virtual void visit (ExternBlock &block) override;
   virtual void visit (LiteralPattern &pattern) override;
   virtual void visit (IdentifierPattern &pattern) override;

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

@@ -114,6 +114,11 @@ class ASTLoweringExternItem : public ASTLoweringBase
       function.get_outer_attrs (), function.get_locus ());
   }
 
+  void visit (AST::ExternalTypeItem &type) override
+  {
+    rust_sorry_at (type.get_locus (), "extern types are not implemented yet");
+  }
+
 private:
   ASTLoweringExternItem () : translated (nullptr) {}
 

gcc/rust/hir/rust-hir-dump.cc

@@ -1999,6 +1999,16 @@ Dump::visit (ExternalFunctionItem &e)
   end ("ExternalFunctionItem");
 }
 
+void
+Dump::visit (ExternalTypeItem &e)
+{
+  begin ("ExternalTypeItem");
+
+  do_externalitem (e);
+
+  end ("ExternalTypeItem");
+}
+
 void
 Dump::visit (ExternBlock &e)
 {

gcc/rust/hir/rust-hir-dump.h

@@ -201,6 +201,7 @@ class Dump : public HIRFullVisitor
 
   virtual void visit (ExternalStaticItem &) override;
   virtual void visit (ExternalFunctionItem &) override;
+  virtual void visit (ExternalTypeItem &) override;
   virtual void visit (ExternBlock &) override;
 
   virtual void visit (LiteralPattern &) override;

gcc/rust/hir/tree/rust-hir-full-decls.h

@@ -177,6 +177,7 @@ class ExternalItem;
 class ExternalStaticItem;
 struct NamedFunctionParam;
 class ExternalFunctionItem;
+class ExternalTypeItem;
 class ExternBlock;
 
 // rust-pattern.h

gcc/rust/hir/tree/rust-hir-item.h

@@ -2859,6 +2859,7 @@ class ExternalItem : public Node
   {
     Static,
     Function,
+    Type,
   };
 
   virtual ~ExternalItem () {}
@@ -3084,11 +3085,13 @@ class ExternalFunctionItem : public ExternalItem
 
   // Copy constructor with clone
   ExternalFunctionItem (ExternalFunctionItem const &other)
-    : ExternalItem (other), return_type (other.return_type->clone_type ()),
-      where_clause (other.where_clause),
+    : ExternalItem (other), where_clause (other.where_clause),
       function_params (other.function_params),
       has_variadics (other.has_variadics)
   {
+    if (other.return_type)
+      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 ());
@@ -3098,11 +3101,14 @@ class ExternalFunctionItem : public ExternalItem
   ExternalFunctionItem &operator= (ExternalFunctionItem const &other)
   {
     ExternalItem::operator= (other);
-    return_type = other.return_type->clone_type ();
+
     where_clause = other.where_clause;
     function_params = other.function_params;
     has_variadics = other.has_variadics;
 
+    if (other.return_type)
+      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 ());
@@ -3144,6 +3150,33 @@ class ExternalFunctionItem : public ExternalItem
   }
 };
 
+class ExternalTypeItem : public ExternalItem
+{
+  ExternalTypeItem (Analysis::NodeMapping mappings, Identifier item_name,
+		    Visibility vis, AST::AttrVec outer_attrs, location_t locus)
+    : ExternalItem (std::move (mappings), std::move (item_name),
+		    std::move (vis), std::move (outer_attrs), locus)
+  {}
+
+  ExternalTypeItem (ExternalTypeItem const &other) : ExternalItem (other) {}
+
+  ExternalTypeItem (ExternalTypeItem &&other) = default;
+  ExternalTypeItem &operator= (ExternalTypeItem &&other) = default;
+
+  std::string as_string () const override;
+
+  void accept_vis (HIRFullVisitor &vis) override;
+  void accept_vis (HIRExternalItemVisitor &vis) override;
+
+  ExternKind get_extern_kind () override { return ExternKind::Type; }
+
+protected:
+  ExternalTypeItem *clone_external_item_impl () const override
+  {
+    return new ExternalTypeItem (*this);
+  }
+};
+
 // An extern block HIR node
 class ExternBlock : public VisItem, public WithInnerAttrs
 {

gcc/rust/hir/tree/rust-hir-visitor.h

@@ -114,6 +114,7 @@ class HIRFullVisitor
   virtual void visit (ImplBlock &impl) = 0;
   virtual void visit (ExternalStaticItem &item) = 0;
   virtual void visit (ExternalFunctionItem &item) = 0;
+  virtual void visit (ExternalTypeItem &item) = 0;
   virtual void visit (ExternBlock &block) = 0;
   virtual void visit (LiteralPattern &pattern) = 0;
   virtual void visit (IdentifierPattern &pattern) = 0;
@@ -255,6 +256,7 @@ class HIRFullVisitorBase : public HIRFullVisitor
 
   virtual void visit (ExternalStaticItem &) override {}
   virtual void visit (ExternalFunctionItem &) override {}
+  virtual void visit (ExternalTypeItem &) override {}
   virtual void visit (ExternBlock &) override {}
 
   virtual void visit (LiteralPattern &) override {}
@@ -306,6 +308,7 @@ class HIRExternalItemVisitor
 public:
   virtual void visit (ExternalStaticItem &item) = 0;
   virtual void visit (ExternalFunctionItem &item) = 0;
+  virtual void visit (ExternalTypeItem &item) = 0;
 };
 
 class HIRTraitItemVisitor

gcc/rust/hir/tree/rust-hir.cc

@@ -3256,6 +3256,19 @@ ExternalFunctionItem::as_string () const
   return str;
 }
 
+std::string
+ExternalTypeItem::as_string () const
+{
+  std::string str = ExternalItem::as_string ();
+
+  str += "type ";
+
+  // add name
+  str += get_item_name ().as_string ();
+
+  return str;
+}
+
 std::string
 NamedFunctionParam::as_string () const
 {
@@ -4272,6 +4285,12 @@ ExternalFunctionItem::accept_vis (HIRFullVisitor &vis)
   vis.visit (*this);
 }
 
+void
+ExternalTypeItem::accept_vis (HIRFullVisitor &vis)
+{
+  vis.visit (*this);
+}
+
 void
 ExternBlock::accept_vis (HIRFullVisitor &vis)
 {
@@ -4542,6 +4561,12 @@ ExternalFunctionItem::accept_vis (HIRExternalItemVisitor &vis)
   vis.visit (*this);
 }
 
+void
+ExternalTypeItem::accept_vis (HIRExternalItemVisitor &vis)
+{
+  vis.visit (*this);
+}
+
 void
 ExternalStaticItem::accept_vis (HIRExternalItemVisitor &vis)
 {