gccrs: Parse const with no value expression

Const with no value expression may exist either in trait or in disabled
blocks. This means we should be able to parse those correctly.

gcc/rust/ChangeLog:

	* ast/rust-item.h: Add a new constructor for const with no value
	expression.
	* parse/rust-parse-impl.h (Parser::parse_const_item): Allow const with
	no expression value.

Signed-off-by: Pierre-Emmanuel Patry <pierre-emmanuel.patry@embecosm.com>

2 files changed, 17 insertions, 0 deletions

diff --git a/gcc/rust/ast/rust-item.h b/gcc/rust/ast/rust-item.h
index b91e18d..eba86dc 100644
--- a/gcc/rust/ast/rust-item.h
+++ b/gcc/rust/ast/rust-item.h
@@ -2604,6 +2604,13 @@ public:
       const_expr (std::move (const_expr)), locus (locus)
   {}
 
+  ConstantItem (std::string ident, Visibility vis, std::unique_ptr<Type> type,
+		std::vector<Attribute> outer_attrs, location_t locus)
+    : VisItem (std::move (vis), std::move (outer_attrs)),
+      identifier (std::move (ident)), type (std::move (type)),
+      const_expr (nullptr), locus (locus)
+  {}
+
   ConstantItem (ConstantItem const &other)
     : VisItem (other), identifier (other.identifier), locus (other.locus)
   {
diff --git a/gcc/rust/parse/rust-parse-impl.h b/gcc/rust/parse/rust-parse-impl.h
index 7844f72..4738393 100644
--- a/gcc/rust/parse/rust-parse-impl.h
+++ b/gcc/rust/parse/rust-parse-impl.h
@@ -4783,6 +4783,16 @@ Parser<ManagedTokenSource>::parse_const_item (AST::Visibility vis,
   // parse constant type (required)
   std::unique_ptr<AST::Type> type = parse_type ();
 
+  // A const with no given expression value
+  if (lexer.peek_token ()->get_id () == SEMICOLON)
+    {
+      lexer.skip_token ();
+      return std::unique_ptr<AST::ConstantItem> (
+	new AST::ConstantItem (std::move (ident), std::move (vis),
+			       std::move (type), std::move (outer_attrs),
+			       locus));
+    }
+
   if (!skip_token (EQUAL))
     {
       skip_after_semicolon ();