Fix template/ref1.C, nontype15.C, addr-builtin1.C with -std=c++1z.

	* parser.c (cp_parser_template_argument): Handle references in
	C++1z mode.
	* constexpr.c (potential_constant_expression_1): Don't error about
	TREE_THIS_VOLATILE on declarations.
	[COMPONENT_REF]: Don't consider the object if we're dealing with an
	overloaded function.

From-SVN: r231351

gcc/cp/ChangeLog

 2015-12-06  Jason Merrill  <jason@redhat.com>
 
+	* parser.c (cp_parser_template_argument): Handle references in
+	C++1z mode.
+	* constexpr.c (potential_constant_expression_1): Don't error about
+	TREE_THIS_VOLATILE on declarations.
+	[COMPONENT_REF]: Don't consider the object if we're dealing with
+	an overloaded function.
+
 	* constraint.cc (strictly_subsumes): New.
 	* cp-tree.h: Declare it.
 	* pt.c (process_partial_specialization): Use it instead of

gcc/cp/constexpr.c

@@ -4130,7 +4130,7 @@ potential_constant_expression_1 (tree t, bool want_rval, bool strict,
     return false;
   if (t == NULL_TREE)
     return true;
-  if (TREE_THIS_VOLATILE (t))
+  if (TREE_THIS_VOLATILE (t) && !DECL_P (t))
     {
       if (flags & tf_error)
         error ("expression %qE has side-effects", t);
@@ -4345,6 +4345,8 @@ potential_constant_expression_1 (tree t, bool want_rval, bool strict,
             of literal type or of pointer to literal type.  */
       /* This test would be redundant, as it follows from the
 	 postfix-expression being a potential constant expression.  */
+      if (type_unknown_p (t))
+	return true;
       return RECUR (TREE_OPERAND (t, 0), want_rval);
 
     case EXPR_PACK_EXPANSION:

gcc/cp/parser.c

@@ -15364,7 +15364,16 @@ cp_parser_template_argument (cp_parser* parser)
      because the argument could really be a type-id.  */
   if (maybe_type_id)
     cp_parser_parse_tentatively (parser);
-  argument = cp_parser_constant_expression (parser);
+
+  if (cxx_dialect <= cxx14)
+    argument = cp_parser_constant_expression (parser);
+  else
+    {
+      /* With C++17 generalized non-type template arguments we need to handle
+	 lvalue constant expressions, too.  */
+      argument = cp_parser_assignment_expression (parser);
+      require_potential_constant_expression (argument);
+    }
 
   if (!maybe_type_id)
     return argument;

gcc/testsuite/g++.dg/template/nontype8.C

@@ -8,6 +8,6 @@ struct S { int m; static int s; } s;
 
 X<&a[2]> x3;                    // { dg-error "" } address of array element
 X<&s.m> x4;                     // { dg-error "" } address of non-static member
-X<&s.s> x5;                     // { dg-error "" } &S::s must be used
+X<&s.s> x5;                     // { dg-error "" "" { target { ! c++1z } } } &S::s must be used
 X<&S::s> x6;                    // OK: address of static member