Re: [C++ Patch] PR 84423 ("[6/7/8/9 Regression] [concepts] ICE with invalid using declaration")

[Paolo Carlini <paolo.carlini@oracle.com>]

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Hi again,

On 9/28/18 9:15 PM, Paolo Carlini wrote:
> Thanks. About the location, you are certainly right, but doesn't seem 
> trivial. Something we can do *now* is using 
> declspecs->locations[ds_typedef] and declspecs->locations[ds_alias], 
> but that gives us the location of the keyword 'typedef' and 'using', 
> respectively, whereas I think that we would like to have the location 
> of 'auto' itself. I could look into that as a follow-up piece work

In fact, completing the work turned out to be easy: ensure that 
cp_parser_alias_declaration saves the location of the defining-type-id 
too and then consistently use locations[ds_type_spec] in the error 
messages. Tested x86_64-linux. Still Ok? ;)

Thanks, Paolo.

///////////////////


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/cp
2018-09-29  Paolo Carlini  <paolo.carlini@oracle.com>

	PR c++/84423
	* pt.c (convert_template_argument): Immediately return error_mark_node
	if the second argument is erroneous.
	* parser.c (cp_parser_alias_declaration): Save the location
	of the type-id too. 
	* decl.c (grokdeclarator): Improve error message for 'auto' in
	alias declaration.

/testsuite
2018-09-29  Paolo Carlini  <paolo.carlini@oracle.com>

	PR c++/84423
	* g++.dg/concepts/pr84423.C: New.

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Index: cp/decl.c
===================================================================
--- cp/decl.c	(revision 264687)
+++ cp/decl.c	(working copy)
@@ -11879,6 +11879,7 @@ grokdeclarator (const cp_declarator *declarator,
   /* If this is declaring a typedef name, return a TYPE_DECL.  */
   if (typedef_p && decl_context != TYPENAME)
     {
+      bool alias_p = decl_spec_seq_has_spec_p (declspecs, ds_alias);
       tree decl;
 
       /* This declaration:
@@ -11901,7 +11902,12 @@ grokdeclarator (const cp_declarator *declarator,
 
       if (type_uses_auto (type))
 	{
-	  error ("typedef declared %<auto%>");
+	  if (alias_p)
+	    error_at (declspecs->locations[ds_type_spec],
+		      "%<auto%> not allowed in alias declaration");
+	  else
+	    error_at (declspecs->locations[ds_type_spec],
+		      "typedef declared %<auto%>");
 	  type = error_mark_node;
 	}
 
@@ -11961,7 +11967,7 @@ grokdeclarator (const cp_declarator *declarator,
 		      inlinep, friendp, raises != NULL_TREE,
 		      declspecs->locations);
 
-      if (decl_spec_seq_has_spec_p (declspecs, ds_alias))
+      if (alias_p)
 	/* Acknowledge that this was written:
 	     `using analias = atype;'.  */
 	TYPE_DECL_ALIAS_P (decl) = 1;
Index: cp/parser.c
===================================================================
--- cp/parser.c	(revision 264687)
+++ cp/parser.c	(working copy)
@@ -19073,6 +19073,7 @@ cp_parser_alias_declaration (cp_parser* parser)
 	G_("types may not be defined in alias template declarations");
     }
 
+  cp_token *type_token = cp_lexer_peek_token (parser->lexer);
   type = cp_parser_type_id (parser);
 
   /* Restore the error message if need be.  */
@@ -19107,6 +19108,9 @@ cp_parser_alias_declaration (cp_parser* parser)
   set_and_check_decl_spec_loc (&decl_specs,
 			       ds_alias,
 			       using_token);
+  set_and_check_decl_spec_loc (&decl_specs,
+			       ds_type_spec,
+			       type_token);
 
   if (parser->num_template_parameter_lists
       && !cp_parser_check_template_parameters (parser,
Index: cp/pt.c
===================================================================
--- cp/pt.c	(revision 264687)
+++ cp/pt.c	(working copy)
@@ -7776,7 +7776,7 @@ convert_template_argument (tree parm,
   tree val;
   int is_type, requires_type, is_tmpl_type, requires_tmpl_type;
 
-  if (parm == error_mark_node)
+  if (parm == error_mark_node || error_operand_p (arg))
     return error_mark_node;
 
   /* Trivially convert placeholders. */
Index: testsuite/g++.dg/concepts/pr84423.C
===================================================================
--- testsuite/g++.dg/concepts/pr84423.C	(nonexistent)
+++ testsuite/g++.dg/concepts/pr84423.C	(working copy)
@@ -0,0 +1,10 @@
+// { dg-do compile { target c++11 } }
+// { dg-additional-options "-fconcepts" }
+
+template<typename> using A = auto;  // { dg-error "30:.auto. not allowed in alias declaration" }
+
+template<template<typename> class> struct B {};
+
+B<A> b;
+
+typedef auto C;  // { dg-error "9:typedef declared .auto." }