Implement N4268, Do constant evaluation of all non-type template args.

gcc/c-family/
	* c-cppbuiltin.c (c_cpp_builtins): Define
	__cpp_nontype_template_args.
gcc/cp/
	* parser.c (cp_parser_template_argument): For C++1z just parse a
	constant-expression.
	* pt.c (convert_nontype_argument): For C++1z always call
	maybe_constant_value.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@229019 138bc75d-0d04-0410-961f-82ee72b054a4

1 files changed, 11 insertions, 0 deletions

diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index 14a5ddd9bb3..142245ad8e0 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -6233,6 +6233,17 @@ convert_nontype_argument (tree type, tree expr, tsubst_flags_t complain)
 	   CONSTRUCTOR.  */;
       else if (INTEGRAL_OR_ENUMERATION_TYPE_P (type))
 	expr = maybe_constant_value (expr);
+      else if (cxx_dialect >= cxx1z)
+	{
+	  if (TREE_CODE (type) != REFERENCE_TYPE)
+	    expr = maybe_constant_value (expr);
+	  else if (REFERENCE_REF_P (expr))
+	    {
+	      expr = TREE_OPERAND (expr, 0);
+	      expr = maybe_constant_value (expr);
+	      expr = convert_from_reference (expr);
+	    }
+	}
       else if (TYPE_PTR_OR_PTRMEM_P (type))
 	{
 	  tree folded = maybe_constant_value (expr);