[Bug c++/39858] "expected primary-expression" error could be more useful

["manu at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39858

Manuel LÃpez-IbÃÃez <manu at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |diagnostic

--- Comment #3 from Manuel LÃpez-IbÃÃez <manu at gcc dot gnu.org> 2012-03-31 01:25:53 UTC ---
This patch does what you want, but it probably fails in unexpected ways because
some callers to cp_parser_primary_expression expect it to give the error
itself, so they won't actually emit an error. One would need to check
error_mark_node in all callers and give an appropriate diagnostic. Even if
someone did that work, I still doubt it will be accepted.


Index: parser.c
===================================================================
--- parser.c    (revision 184424)
+++ parser.c    (working copy)
@@ -4379,11 +4379,11 @@ cp_parser_primary_expression (cp_parser 
        return decl;
       }

       /* Anything else is an error.  */
     default:
-      cp_parser_error (parser, "expected primary-expression");
+      /*      cp_parser_error (parser, "expected primary-expression");*/
       return error_mark_node;
     }
 }

 /* Parse an id-expression.
@@ -5862,12 +5862,14 @@ cp_parser_postfix_open_square_expression
        {
          bool expr_nonconst_p;
          maybe_warn_cpp0x (CPP0X_INITIALIZER_LISTS);
          index = cp_parser_braced_list (parser, &expr_nonconst_p);
        }
-      else
+      else 
        index = cp_parser_expression (parser, /*cast_p=*/false, NULL);
+      if (index == error_mark_node)
+       error_at (input_location, "missing subscript");
     }

   /* Look for the closing `]'.  */
   cp_parser_require (parser, CPP_CLOSE_SQUARE, RT_CLOSE_SQUARE);



An alternative would be to just give a normal error that is:

@@ -4379,11 +4379,11 @@ cp_parser_primary_expression (cp_parser 
        return decl;
       }

       /* Anything else is an error.  */
     default:
-      cp_parser_error (parser, "expected primary-expression");
+      error ("expected expression");
       return error_mark_node;
     }
 }

 /* Parse an id-expression.