--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gcc/cp/type-utils.h	Fri Oct 27 22:46:09 2017 +0900
@@ -0,0 +1,55 @@
+/* Utilities for querying and manipulating type trees.
+   Copyright (C) 2013-2017 Free Software Foundation, Inc.
+
+This file is part of GCC.
+
+GCC is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 3, or (at your option)
+any later version.
+
+GCC is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with GCC; see the file COPYING3.  If not see
+<http://www.gnu.org/licenses/>.  */
+
+#ifndef GCC_CP_TYPE_UTILS_H
+#define GCC_CP_TYPE_UTILS_H
+
+/* Returns the first tree within T that is directly matched by PRED.  T may be a
+   type or PARM_DECL and is incrementally decomposed toward its type-specifier
+   until a match is found.  NULL_TREE is returned if PRED does not match any
+   part of T.
+
+   This is primarily intended for detecting whether T uses `auto' or a concept
+   identifier.  Since either of these can only appear as a type-specifier for
+   the declaration in question, only top-level qualifications are traversed;
+   find_type_usage does not look through the whole type.  */
+
+inline tree
+find_type_usage (tree t, bool (*pred) (const_tree))
+{
+  enum tree_code code;
+  if (pred (t))
+    return t;
+
+  code = TREE_CODE (t);
+
+  if (code == POINTER_TYPE || code == REFERENCE_TYPE
+      || code == PARM_DECL || code == OFFSET_TYPE
+      || code == FUNCTION_TYPE || code == METHOD_TYPE
+      || code == ARRAY_TYPE)
+    return find_type_usage (TREE_TYPE (t), pred);
+
+  if (TYPE_PTRMEMFUNC_P (t))
+    return find_type_usage
+      (TREE_TYPE (TYPE_PTRMEMFUNC_FN_TYPE (t)), pred);
+
+  return NULL_TREE;
+}
+
+#endif // GCC_CP_TYPE_UTILS_H