C++ PATCH for c++/43321 (error on valid C++0x auto)

commit 9ffe8ed0665020e00f7923314fe2e9aa99a155b1
Author: Jason Merrill <jason@redhat.com>
Date:   Sat Jun 18 15:35:45 2011 -0400

    	PR c++/43321
    	* semantics.c (describable_type): Remove.
    	* cp-tree.h: Likewise.
    	* decl.c (cp_finish_decl): Don't call it.
    	* init.c (build_new): Likewise.
    	* parser.c (cp_parser_omp_for_loop): Likewise.
    	* pt.c (tsubst_decl): Likewise.
    	(do_auto_deduction): If we fail in a template, try again
    	at instantiation time.

diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
index 2773e34..904e44c 100644
--- a/gcc/cp/cp-tree.h
+++ b/gcc/cp/cp-tree.h
@@ -5445,7 +5445,6 @@  extern bool cxx_omp_create_clause_info		(tree, tree, bool, bool, bool);
 extern tree baselink_for_fns                    (tree);
 extern void finish_static_assert                (tree, tree, location_t,
                                                  bool);
-extern tree describable_type			(tree);
 extern tree finish_decltype_type                (tree, bool, tsubst_flags_t);
 extern tree finish_trait_expr			(enum cp_trait_kind, tree, tree);
 extern tree build_lambda_expr                   (void);
diff --git a/gcc/cp/decl.c b/gcc/cp/decl.c
index 59c4a4c..85249f1 100644
--- a/gcc/cp/decl.c
+++ b/gcc/cp/decl.c
@@ -5944,13 +5944,10 @@  cp_finish_decl (tree decl, tree init, bool init_const_expr_p,
 	d_init = build_x_compound_expr_from_list (d_init, ELK_INIT,
 						  tf_warning_or_error);
       d_init = resolve_nondeduced_context (d_init);
-      if (describable_type (d_init))
-	{
-	  type = TREE_TYPE (decl) = do_auto_deduction (type, d_init,
-						       auto_node);
-	  if (type == error_mark_node)
-	    return;
-	}
+      type = TREE_TYPE (decl) = do_auto_deduction (type, d_init,
+						   auto_node);
+      if (type == error_mark_node)
+	return;
     }
 
   if (!ensure_literal_type_for_constexpr_object (decl))
diff --git a/gcc/cp/init.c b/gcc/cp/init.c
index 3b92665..140e064 100644
--- a/gcc/cp/init.c
+++ b/gcc/cp/init.c
@@ -2600,8 +2600,7 @@  build_new (VEC(tree,gc) **placement, tree type, tree nelts,
 	{
 	  tree d_init = VEC_index (tree, *init, 0);
 	  d_init = resolve_nondeduced_context (d_init);
-	  if (describable_type (d_init))
-	    type = do_auto_deduction (type, d_init, auto_node);
+	  type = do_auto_deduction (type, d_init, auto_node);
 	}
     }
 
diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
index 75dac6a..856a8a7 100644
--- a/gcc/cp/parser.c
+++ b/gcc/cp/parser.c
@@ -24504,7 +24504,7 @@  cp_parser_omp_for_loop (cp_parser *parser, tree clauses, tree *par_clauses)
 						    &is_direct_init,
 						    &is_non_constant_init);
 
-		      if (auto_node && describable_type (init))
+		      if (auto_node)
 			{
 			  TREE_TYPE (decl)
 			    = do_auto_deduction (TREE_TYPE (decl), init,
diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index 85f2749..6f15101 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -10122,11 +10122,8 @@  tsubst_decl (tree t, tree args, tsubst_flags_t complain)
 	    if (auto_node && init)
 	      {
 		init = resolve_nondeduced_context (init);
-		if (describable_type (init))
-		  {
-		    type = do_auto_deduction (type, init, auto_node);
-		    TREE_TYPE (r) = type;
-		  }
+		TREE_TYPE (r) = type
+		  = do_auto_deduction (type, init, auto_node);
 	      }
 	  }
 	else
@@ -19302,6 +19299,12 @@  do_auto_deduction (tree type, tree init, tree auto_node)
   tree decl;
   int val;
 
+  if (processing_template_decl
+      && (TREE_TYPE (init) == NULL_TREE
+	  || BRACE_ENCLOSED_INITIALIZER_P (init)))
+    /* Not enough information to try this yet.  */
+    return type;
+
   /* The name of the object being declared shall not appear in the
      initializer expression.  */
   decl = cp_walk_tree_without_duplicates (&init, contains_auto_r, type);
@@ -19331,6 +19334,9 @@  do_auto_deduction (tree type, tree init, tree auto_node)
 			       DEDUCE_CALL, LOOKUP_NORMAL);
   if (val > 0)
     {
+      if (processing_template_decl)
+	/* Try again at instantiation time.  */
+	return type;
       if (type && type != error_mark_node)
 	/* If type is error_mark_node a diagnostic must have been
 	   emitted by now.  Also, having a mention to '<type error>'
diff --git a/gcc/cp/semantics.c b/gcc/cp/semantics.c
index 1f683c7..cfe3959 100644
--- a/gcc/cp/semantics.c
+++ b/gcc/cp/semantics.c
@@ -4803,65 +4803,6 @@  finish_static_assert (tree condition, tree message, location_t location,
     }
 }
 
-/* Returns the type of EXPR for cases where we can determine it even though
-   EXPR is a type-dependent expression.  */
-
-tree
-describable_type (tree expr)
-{
-  tree type = NULL_TREE;
-
-  if (! type_dependent_expression_p (expr)
-      && ! type_unknown_p (expr))
-    {
-      type = unlowered_expr_type (expr);
-      if (real_lvalue_p (expr))
-	type = build_reference_type (type);
-    }
-
-  if (type)
-    return type;
-
-  switch (TREE_CODE (expr))
-    {
-    case VAR_DECL:
-    case PARM_DECL:
-    case RESULT_DECL:
-    case FUNCTION_DECL:
-      return TREE_TYPE (expr);
-      break;
-
-    case NEW_EXPR:
-    case CONST_DECL:
-    case TEMPLATE_PARM_INDEX:
-    case CAST_EXPR:
-    case STATIC_CAST_EXPR:
-    case REINTERPRET_CAST_EXPR:
-    case CONST_CAST_EXPR:
-    case DYNAMIC_CAST_EXPR:
-      type = TREE_TYPE (expr);
-      break;
-
-    case INDIRECT_REF:
-      {
-	tree ptrtype = describable_type (TREE_OPERAND (expr, 0));
-	if (ptrtype && POINTER_TYPE_P (ptrtype))
-	  type = build_reference_type (TREE_TYPE (ptrtype));
-      }
-      break;
-
-    default:
-      if (TREE_CODE_CLASS (TREE_CODE (expr)) == tcc_constant)
-	type = TREE_TYPE (expr);
-      break;
-    }
-
-  if (type && type_uses_auto (type))
-    return NULL_TREE;
-  else
-    return type;
-}
-
 /* Implements the C++0x decltype keyword. Returns the type of EXPR,
    suitable for use as a type-specifier.
 
diff --git a/gcc/cp/typeck.c b/gcc/cp/typeck.c
index 39e974b..7af76b1 100644
--- a/gcc/cp/typeck.c
+++ b/gcc/cp/typeck.c
@@ -2681,8 +2681,7 @@  build_x_indirect_ref (tree expr, ref_operator errorstring,
 
   if (processing_template_decl)
     {
-      /* Retain the type if we know the operand is a pointer so that
-	 describable_type doesn't make auto deduction break.  */
+      /* Retain the type if we know the operand is a pointer.  */
       if (TREE_TYPE (expr) && POINTER_TYPE_P (TREE_TYPE (expr)))
 	return build_min (INDIRECT_REF, TREE_TYPE (TREE_TYPE (expr)), expr);
       if (type_dependent_expression_p (expr))
diff --git a/gcc/testsuite/g++.dg/cpp0x/auto26.C b/gcc/testsuite/g++.dg/cpp0x/auto26.C
new file mode 100644
index 0000000..6e55aa4
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/auto26.C
@@ -0,0 +1,21 @@ 
+// PR c++/43321
+// { dg-options -std=c++0x }
+
+template <class T>
+void f(T t)
+{
+  auto *p = t;
+}
+
+template <class T>
+void g(const T& tr)
+{
+  auto p = *tr;
+}
+
+int main()
+{
+  int b;
+  f(&b);
+  g(&b);
+}