gccrs: ast: Add ExternalTypeItem node

gcc/rust/ChangeLog:

	* ast/rust-item.h (class ExternalTypeItem): New class.
	* ast/rust-ast.cc (ExternalTypeItem::as_string): New function.
	(ExternalTypeItem::accept_vis): Likewise.
	* ast/rust-ast-full-decls.h (class ExternalTypeItem): Declare class.
	* ast/rust-ast-dump.cc (Dump::visit): Add base visitor for ExternalTypeItem.
	* ast/rust-ast-dump.h: Likewise.
	* ast/rust-ast-visitor.h: Likewise.
	* checks/errors/rust-feature-gate.h: Likewise.
	* expand/rust-attribute-visitor.cc (AttrVisitor::visit): Likewise.
	* expand/rust-attribute-visitor.h: Likewise.
	* hir/rust-ast-lower-base.cc (ASTLoweringBase::visit): Likewise.
	* hir/rust-ast-lower-base.h: Likewise.
	* resolve/rust-ast-resolve-base.cc (ResolverBase::visit): Likewise.
	* resolve/rust-ast-resolve-base.h: Likewise.
	* resolve/rust-early-name-resolver.cc (EarlyNameResolver::visit): Likewise.
	* resolve/rust-early-name-resolver.h: Likewise.
	* util/rust-attributes.cc (AttributeChecker::visit): Likewise.
	* util/rust-attributes.h: Likewise.

6 files changed, 98 insertions, 0 deletions

diff --git a/gcc/rust/ast/rust-ast-dump.cc b/gcc/rust/ast/rust-ast-dump.cc
index a581c02..a5fce67 100644
--- a/gcc/rust/ast/rust-ast-dump.cc
+++ b/gcc/rust/ast/rust-ast-dump.cc
@@ -1433,6 +1433,10 @@ Dump::visit (TraitImpl &impl)
 }
 
 void
+Dump::visit (ExternalTypeItem &type)
+{}
+
+void
 Dump::visit (ExternalStaticItem &)
 {}
 
diff --git a/gcc/rust/ast/rust-ast-dump.h b/gcc/rust/ast/rust-ast-dump.h
index ea3e6f3..a6adab9 100644
--- a/gcc/rust/ast/rust-ast-dump.h
+++ b/gcc/rust/ast/rust-ast-dump.h
@@ -251,6 +251,7 @@ private:
   void visit (Trait &trait);
   void visit (InherentImpl &impl);
   void visit (TraitImpl &impl);
+  void visit (ExternalTypeItem &item);
   void visit (ExternalStaticItem &item);
   void visit (ExternalFunctionItem &item);
   void visit (ExternBlock &block);
diff --git a/gcc/rust/ast/rust-ast-full-decls.h b/gcc/rust/ast/rust-ast-full-decls.h
index 96a6f22..352c1b9 100644
--- a/gcc/rust/ast/rust-ast-full-decls.h
+++ b/gcc/rust/ast/rust-ast-full-decls.h
@@ -203,6 +203,7 @@ class Impl;
 class InherentImpl;
 class TraitImpl;
 class ExternalItem;
+class ExternalTypeItem;
 class ExternalStaticItem;
 struct NamedFunctionParam;
 class ExternalFunctionItem;
diff --git a/gcc/rust/ast/rust-ast-visitor.h b/gcc/rust/ast/rust-ast-visitor.h
index 9cde911..776e1e2 100644
--- a/gcc/rust/ast/rust-ast-visitor.h
+++ b/gcc/rust/ast/rust-ast-visitor.h
@@ -161,6 +161,7 @@ public:
   virtual void visit (InherentImpl &impl) = 0;
   virtual void visit (TraitImpl &impl) = 0;
   // virtual void visit(ExternalItem& item) = 0;
+  virtual void visit (ExternalTypeItem &type) = 0;
   virtual void visit (ExternalStaticItem &item) = 0;
   virtual void visit (ExternalFunctionItem &item) = 0;
   virtual void visit (ExternBlock &block) = 0;
diff --git a/gcc/rust/ast/rust-ast.cc b/gcc/rust/ast/rust-ast.cc
index 6692505..13d31cf 100644
--- a/gcc/rust/ast/rust-ast.cc
+++ b/gcc/rust/ast/rust-ast.cc
@@ -3407,6 +3407,16 @@ EnumItemDiscriminant::as_string () const
 }
 
 std::string
+ExternalTypeItem::as_string () const
+{
+  auto str = append_attributes (outer_attrs, OUTER);
+
+  str += "type " + item_name + ";";
+
+  return str;
+}
+
+std::string
 ExternalStaticItem::as_string () const
 {
   // outer attributes
@@ -5493,6 +5503,12 @@ TraitImpl::accept_vis (ASTVisitor &vis)
 }
 
 void
+ExternalTypeItem::accept_vis (ASTVisitor &vis)
+{
+  vis.visit (*this);
+}
+
+void
 ExternalStaticItem::accept_vis (ASTVisitor &vis)
 {
   vis.visit (*this);
diff --git a/gcc/rust/ast/rust-item.h b/gcc/rust/ast/rust-item.h
index 4385323..2abf781 100644
--- a/gcc/rust/ast/rust-item.h
+++ b/gcc/rust/ast/rust-item.h
@@ -3907,6 +3907,81 @@ protected:
 };
 #endif
 
+// A foreign type defined outside the current crate.
+// https://rust-lang.github.io/rfcs/1861-extern-types.html
+class ExternalTypeItem : public ExternalItem
+{
+  std::vector<Attribute> outer_attrs;
+
+  Visibility visibility;
+  Identifier item_name;
+  Location locus;
+
+  bool marked_for_strip;
+
+public:
+  ExternalTypeItem (Identifier item_name, Visibility vis,
+		    std::vector<Attribute> outer_attrs, Location locus)
+    : ExternalItem (), outer_attrs (std::move (outer_attrs)), visibility (vis),
+      item_name (std::move (item_name)), locus (locus), marked_for_strip (false)
+  {}
+
+  ExternalTypeItem (ExternalTypeItem const &other)
+    : outer_attrs (other.outer_attrs), visibility (other.visibility),
+      item_name (other.item_name), locus (other.locus),
+      marked_for_strip (other.marked_for_strip)
+  {
+    node_id = other.node_id;
+  }
+
+  ExternalTypeItem &operator= (ExternalTypeItem const &other)
+  {
+    node_id = other.node_id;
+    outer_attrs = other.outer_attrs;
+    visibility = other.visibility;
+    item_name = other.item_name;
+    locus = other.locus;
+    marked_for_strip = other.marked_for_strip;
+
+    return *this;
+  }
+
+  // move constructors
+  ExternalTypeItem (ExternalTypeItem &&other) = default;
+  ExternalTypeItem &operator= (ExternalTypeItem &&other) = default;
+
+  std::string as_string () const override;
+
+  void accept_vis (ASTVisitor &vis) override;
+
+  // Returns whether item has outer attributes.
+  bool has_outer_attrs () const { return !outer_attrs.empty (); }
+
+  // Returns whether item has non-default visibility.
+  bool has_visibility () const { return !visibility.is_error (); }
+
+  Location get_locus () const { return locus; }
+
+  void mark_for_strip () override { marked_for_strip = true; };
+  bool is_marked_for_strip () const override { return marked_for_strip; };
+
+  // TODO: this mutable getter seems really dodgy. Think up better way.
+  std::vector<Attribute> &get_outer_attrs () { return outer_attrs; }
+  const std::vector<Attribute> &get_outer_attrs () const { return outer_attrs; }
+
+  Identifier get_identifier () const { return item_name; }
+
+  const Visibility &get_visibility () const { return visibility; }
+
+protected:
+  /* Use covariance to implement clone function as returning this object
+   * rather than base */
+  ExternalTypeItem *clone_external_item_impl () const override
+  {
+    return new ExternalTypeItem (*this);
+  }
+};
+
 // A static item used in an extern block
 class ExternalStaticItem : public ExternalItem
 {