[C++ Patch] PR 51911 V2 ("G++ accepts new auto { list }")

[Paolo Carlini]

Hi,

this is a slightly reworked (simplified) version of a patch I sent a 
while ago. The issue is that we are not enforcing at all 5.3.4/2 in the 
parser, thus we end up rejecting the first test below with a misleading 
error message talking about list-initialization (and a wrong location), 
because we diagnose it too late like 'auto foo{3, 4, 5};', and simply 
accepting the second. Tested x86_64-linux.

Thanks,
Paolo.

////////////////////////
/cp
2015-09-11  Paolo Carlini  <paolo.carl...@oracle.com>

        PR c++/51911
        * parser.c (cp_parser_new_expression): Enforce 5.3.4/2.

/testsuite
2015-09-11  Paolo Carlini  <paolo.carl...@oracle.com>

        PR c++/51911
        * g++.dg/cpp0x/new-auto1.C: New.
Index: cp/parser.c
===================================================================
--- cp/parser.c (revision 227690)
+++ cp/parser.c (working copy)
@@ -7591,8 +7591,9 @@ cp_parser_new_expression (cp_parser* parser)
     type = cp_parser_new_type_id (parser, &nelts);
 
   /* If the next token is a `(' or '{', then we have a new-initializer.  */
-  if (cp_lexer_next_token_is (parser->lexer, CPP_OPEN_PAREN)
-      || cp_lexer_next_token_is (parser->lexer, CPP_OPEN_BRACE))
+  cp_token *token = cp_lexer_peek_token (parser->lexer);
+  if (token->type == CPP_OPEN_PAREN
+      || token->type == CPP_OPEN_BRACE)
     initializer = cp_parser_new_initializer (parser);
   else
     initializer = NULL;
@@ -7601,6 +7602,18 @@ cp_parser_new_expression (cp_parser* parser)
      expression.  */
   if (cp_parser_non_integral_constant_expression (parser, NIC_NEW))
     ret = error_mark_node;
+  /* 5.3.4/2: "If the auto type-specifier appears in the type-specifier-seq
+     of a new-type-id or type-id of a new-expression, the new-expression shall
+     contain a new-initializer of the form ( assignment-expression )".  */
+  else if (type_uses_auto (type)
+          && (token->type != CPP_OPEN_PAREN
+              || vec_safe_length (initializer) != 1))
+    {
+      error_at (token->location,
+               "initialization of new-expression for type %<auto%> "
+               "requires exactly one parenthesized expression");
+      ret = error_mark_node;
+    }
   else
     {
       /* Create a representation of the new-expression.  */
Index: testsuite/g++.dg/cpp0x/new-auto1.C
===================================================================
--- testsuite/g++.dg/cpp0x/new-auto1.C  (revision 0)
+++ testsuite/g++.dg/cpp0x/new-auto1.C  (working copy)
@@ -0,0 +1,7 @@
+// PR c++/51911
+// { dg-do compile { target c++11 } }
+
+#include <initializer_list>
+
+auto foo = new auto { 3, 4, 5 };  // { dg-error "21:initialization of 
new-expression for type 'auto'" }
+auto bar = new auto { 3 };  // { dg-error "21:initialization of new-expression 
for type 'auto'" }