PR c++/77790 - ICE with auto function in C++11 mode

* decl.c (undeduced_auto_decl): Remove C++14 limitation.
	(require_deduced_type): Add complain parm, return bool.
	* cp-tree.h: Adjust.
	* decl2.c (mark_used): Use require_deduced_type.

From-SVN: r245358

gcc/cp/ChangeLog

@@ -1,3 +1,11 @@
+2017-02-11  Jason Merrill  <jason@redhat.com>
+
+	PR c++/77790 - ICE with auto function in C++11 mode
+	* decl.c (undeduced_auto_decl): Remove C++14 limitation.
+	(require_deduced_type): Add complain parm, return bool.
+	* cp-tree.h: Adjust.
+	* decl2.c (mark_used): Use require_deduced_type.
+
 2017-02-10  Jason Merrill  <jason@redhat.com>
 
 	PR c++/78908 - template ops and bitfields

gcc/cp/cp-tree.h

@@ -5909,7 +5909,7 @@ extern tree reshape_init                        (tree, tree, tsubst_flags_t);
 extern tree next_initializable_field (tree);
 extern tree fndecl_declared_return_type		(tree);
 extern bool undeduced_auto_decl			(tree);
-extern void require_deduced_type		(tree);
+extern bool require_deduced_type		(tree, tsubst_flags_t = tf_warning_or_error);
 
 extern tree finish_case_label			(location_t, tree, tree);
 extern tree cxx_maybe_build_cleanup		(tree, tsubst_flags_t);

gcc/cp/decl.c

@@ -16138,24 +16138,29 @@ fndecl_declared_return_type (tree fn)
   return TREE_TYPE (TREE_TYPE (fn));
 }
 
-/* Returns true iff DECL was declared with an auto return type and it has
+/* Returns true iff DECL was declared with an auto type and it has
    not yet been deduced to a real type.  */
 
 bool
 undeduced_auto_decl (tree decl)
 {
-  if (cxx_dialect < cxx14)
+  if (cxx_dialect < cxx11)
     return false;
   return type_uses_auto (TREE_TYPE (decl));
 }
 
 /* Complain if DECL has an undeduced return type.  */
 
-void
+bool
-require_deduced_type (tree decl)
+require_deduced_type (tree decl, tsubst_flags_t complain)
 {
   if (undeduced_auto_decl (decl))
+    {
+      if (complain & tf_error)
 	error ("use of %qD before deduction of %<auto%>", decl);
+      return false;
+    }
+  return true;
 }
 
 #include "gt-cp-decl.h"

gcc/cp/decl2.c

@@ -5084,12 +5084,9 @@ mark_used (tree decl, tsubst_flags_t complain)
       || DECL_LANG_SPECIFIC (decl) == NULL
       || DECL_THUNK_P (decl))
     {
-      if (!processing_template_decl && type_uses_auto (TREE_TYPE (decl)))
+      if (!processing_template_decl
-	{
+	  && !require_deduced_type (decl, complain))
-	  if (complain & tf_error)
-	    error ("use of %qD before deduction of %<auto%>", decl);
 	return false;
-	}
       return true;
     }
 
@@ -5117,12 +5114,8 @@ mark_used (tree decl, tsubst_flags_t complain)
       && uses_template_parms (DECL_TI_ARGS (decl)))
     return true;
 
-  if (undeduced_auto_decl (decl))
+  if (!require_deduced_type (decl, complain))
-    {
-      if (complain & tf_error)
-	error ("use of %qD before deduction of %<auto%>", decl);
     return false;
-    }
 
   /* If we don't need a value, then we don't need to synthesize DECL.  */
   if (cp_unevaluated_operand || in_discarded_stmt)

gcc/testsuite/g++.dg/cpp0x/auto41.C

@@ -2,4 +2,4 @@
 // { dg-do compile { target c++11 } }
 
 auto foo();			// { dg-error "auto" "" { target { ! c++14 } } }
-auto fp = foo;			// { dg-error "auto" "" { target c++14 } }
+auto fp = foo;			// { dg-error "auto" }

gcc/testsuite/g++.dg/cpp1y/auto-fn35.C

@@ -0,0 +1,11 @@
+// PR c++/77790
+// { dg-do compile { target c++11 } }
+
+template < typename S > struct A
+{
+  // { dg-error "" "" { target c++11_only } .+1 }
+  template < typename T > static auto f () { return 0; } 
+  template < class U = decltype (f < S > ()) > int g () { return 0; }
+};
+
+auto a = A < int > {}.g ();