C++ PATCH for c++/70622 (wrong error with multiple auto)

[Jason Merrill <jason at redhat dot com>]

My change to how we check for consistency of multiple declarators for 
the same auto type-specifier failed to consider declarators of different 
forms; we need to compare only the part of the declared type that 
corresponds to the type-specifier.

Tested x86_64-pc-linux-gnu, applying to trunk.

commit 824d6696c29b11ff8015f632c58272685c0bbfe6
Author: Jason Merrill <jason@redhat.com>
Date:   Thu Apr 14 15:05:44 2016 -0400

    	PR c++/70622
    
    	* parser.c (cp_parser_init_declarator): Add auto_result parm.
    	(cp_parser_simple_declaration): Pass it.
    	(strip_declarator_types): New.

diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
index 00e211e..cba2d65 100644
--- a/gcc/cp/parser.c
+++ b/gcc/cp/parser.c
@@ -2193,7 +2193,7 @@ static tree cp_parser_decltype
 
 static tree cp_parser_init_declarator
   (cp_parser *, cp_decl_specifier_seq *, vec<deferred_access_check, va_gc> *,
-   bool, bool, int, bool *, tree *, location_t *);
+   bool, bool, int, bool *, tree *, location_t *, tree *);
 static cp_declarator *cp_parser_declarator
   (cp_parser *, cp_parser_declarator_kind, int *, bool *, bool, bool);
 static cp_declarator *cp_parser_direct_declarator
@@ -12337,10 +12337,9 @@ cp_parser_simple_declaration (cp_parser* parser,
       && !cp_parser_error_occurred (parser))
     cp_parser_commit_to_tentative_parse (parser);
 
-  tree last_type, auto_node;
+  tree last_type;
 
   last_type = NULL_TREE;
-  auto_node = type_uses_auto (decl_specifiers.type);
 
   /* Keep going until we hit the `;' at the end of the simple
      declaration.  */
@@ -12351,6 +12350,7 @@ cp_parser_simple_declaration (cp_parser* parser,
       cp_token *token;
       bool function_definition_p;
       tree decl;
+      tree auto_result = NULL_TREE;
 
       if (saw_declarator)
 	{
@@ -12376,7 +12376,8 @@ cp_parser_simple_declaration (cp_parser* parser,
 					declares_class_or_enum,
 					&function_definition_p,
 					maybe_range_for_decl,
-					&init_loc);
+					&init_loc,
+					&auto_result);
       /* If an error occurred while parsing tentatively, exit quickly.
 	 (That usually happens when in the body of a function; each
 	 statement is treated as a declaration-statement until proven
@@ -12384,10 +12385,10 @@ cp_parser_simple_declaration (cp_parser* parser,
       if (cp_parser_error_occurred (parser))
 	goto done;
 
-      if (auto_node)
+      if (auto_result)
 	{
-	  tree type = TREE_TYPE (decl);
-	  if (last_type && !same_type_p (type, last_type))
+	  if (last_type && last_type != error_mark_node
+	      && !same_type_p (auto_result, last_type))
 	    {
 	      /* If the list of declarators contains more than one declarator,
 		 the type of each declared variable is determined as described
@@ -12395,10 +12396,11 @@ cp_parser_simple_declaration (cp_parser* parser,
 		 the same in each deduction, the program is ill-formed.  */
 	      error_at (decl_specifiers.locations[ds_type_spec],
 			"inconsistent deduction for %qT: %qT and then %qT",
-			decl_specifiers.type, last_type, type);
-	      auto_node = NULL_TREE;
+			decl_specifiers.type, last_type, auto_result);
+	      last_type = error_mark_node;
 	    }
-	  last_type = type;
+	  else
+	    last_type = auto_result;
 	}
 
       /* Handle function definitions specially.  */
@@ -18221,6 +18223,31 @@ cp_parser_asm_definition (cp_parser* parser)
     }
 }
 
+/* Given the type TYPE of a declaration with declarator DECLARATOR, return the
+   type that comes from the decl-specifier-seq.  */
+
+static tree
+strip_declarator_types (tree type, cp_declarator *declarator)
+{
+  for (cp_declarator *d = declarator; d;)
+    switch (d->kind)
+      {
+      case cdk_id:
+      case cdk_error:
+	d = NULL;
+	break;
+
+      default:
+	if (TYPE_PTRMEMFUNC_P (type))
+	  type = TYPE_PTRMEMFUNC_FN_TYPE (type);
+	type = TREE_TYPE (type);
+	d = d->declarator;
+	break;
+      }
+
+  return type;
+}
+
 /* Declarators [gram.dcl.decl] */
 
 /* Parse an init-declarator.
@@ -18286,7 +18313,8 @@ cp_parser_init_declarator (cp_parser* parser,
 			   int declares_class_or_enum,
 			   bool* function_definition_p,
 			   tree* maybe_range_for_decl,
-			   location_t* init_loc)
+			   location_t* init_loc,
+			   tree* auto_result)
 {
   cp_token *token = NULL, *asm_spec_start_token = NULL,
            *attributes_start_token = NULL;
@@ -18677,6 +18705,10 @@ cp_parser_init_declarator (cp_parser* parser,
 	finish_fully_implicit_template (parser, /*member_decl_opt=*/0);
     }
 
+  if (auto_result && is_initialized && decl_specifiers->type
+      && type_uses_auto (decl_specifiers->type))
+    *auto_result = strip_declarator_types (TREE_TYPE (decl), declarator);
+
   return decl;
 }
 
@@ -25808,7 +25840,7 @@ cp_parser_single_declaration (cp_parser* parser,
 				        member_p,
 				        declares_class_or_enum,
 				        &function_definition_p,
-					NULL, NULL);
+					NULL, NULL, NULL);
 
     /* 7.1.1-1 [dcl.stc]
 
diff --git a/gcc/testsuite/g++.dg/cpp0x/auto47.C b/gcc/testsuite/g++.dg/cpp0x/auto47.C
new file mode 100644
index 0000000..0d80be6
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/auto47.C
@@ -0,0 +1,7 @@
+// PR c++/70622
+// { dg-do compile { target c++11 } }
+
+int main()
+{
+    auto x = 0, *y = &x;
+}