re PR c++/54947 ([C++11] lambda cannot capture-by-copy inside braced-init-list)

	PR c++/54947
	* parser.c (cp_parser_initializer_list): Don't require an
	expression in [] to be constant until we know it's a C99
	designator.

From-SVN: r194256

gcc/cp/ChangeLog

 2012-12-06  Jason Merrill  <jason@redhat.com>
 
+	PR c++/54947
+	* parser.c (cp_parser_initializer_list): Don't require an
+	expression in [] to be constant until we know it's a C99
+	designator.
+
 	PR c++/55015
 	PR c++/53821
 	* semantics.c (maybe_add_lambda_conv_op): Revert earlier change.

gcc/cp/parser.c

@@ -17923,11 +17923,14 @@ cp_parser_initializer_list (cp_parser* parser, bool* non_constant_p)
 	  /* In C++11, [ could start a lambda-introducer.  */
 	  cp_parser_parse_tentatively (parser);
 	  cp_lexer_consume_token (parser->lexer);
-	  designator = cp_parser_constant_expression (parser, false, NULL);
+	  bool non_const = false;
+	  designator = cp_parser_constant_expression (parser, true, &non_const);
 	  cp_parser_require (parser, CPP_CLOSE_SQUARE, RT_CLOSE_SQUARE);
 	  cp_parser_require (parser, CPP_EQ, RT_EQ);
 	  if (!cp_parser_parse_definitely (parser))
 	    designator = NULL_TREE;
+	  else if (non_const)
+	    require_potential_rvalue_constant_expression (designator);
 	}
       else
 	designator = NULL_TREE;

gcc/testsuite/g++.dg/cpp0x/lambda/lambda-initlist2.C

+// PR c++/54947
+// { dg-options -std=gnu++11 }
+
+struct X
+{
+  template<typename L>
+    X(L)
+    { }
+};
+
+template<typename A>
+  void
+  test()
+  {
+    int i = 0;
+
+    A a_ok_1( [=] { return i; } );  // OK
+    A a_ok_2( [i] { return i; } );  // OK
+
+    A a_err_1{ [i] { return i; } };  // error
+    A a_err_2{ [=] { return i; } };  // error
+  }
+
+int main()
+{
+  test<X>();
+}