From 17c6c56b906d99b45dc5eefa5d39435188235051 Mon Sep 17 00:00:00 2001
From: Ryan Burn <contact@rnburn.com>
Date: Mon, 7 Dec 2015 21:45:13 +0000
Subject: [PATCH] re PR c++/68683 ([concepts] function
 satisfy_argument_deduction_constraint modifies a type tree node but leaves
 TYPE_CANONICAL unchanged)

	PR c++/68683
	* constraint.cc (satisfy_argument_deduction_constraint): Set
	TYPE_CANONICAL to NULL_TREE if PLACEHOLDER_TYPE_CONSTRAINTS are
	changed.

From-SVN: r231385
---
 gcc/cp/ChangeLog                        |  7 +++++++
 gcc/cp/constraint.cc                    |  3 +++
 gcc/testsuite/g++.dg/concepts/pr68683.C | 24 ++++++++++++++++++++++++
 3 files changed, 34 insertions(+)
 create mode 100644 gcc/testsuite/g++.dg/concepts/pr68683.C

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index 5232534dfd8..6b007e2aea3 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,10 @@
+2015-12-07  Ryan Burn  <contact@rnburn.com>
+
+	PR c++/68683
+	* constraint.cc (satisfy_argument_deduction_constraint): Set
+	TYPE_CANONICAL to NULL_TREE if PLACEHOLDER_TYPE_CONSTRAINTS are
+	changed.
+
 2015-12-07  Jason Merrill  <jason@redhat.com>
 
 	PR c++/68464
diff --git a/gcc/cp/constraint.cc b/gcc/cp/constraint.cc
index 89da6ecbf79..426d8f3f48b 100644
--- a/gcc/cp/constraint.cc
+++ b/gcc/cp/constraint.cc
@@ -1871,11 +1871,14 @@ satisfy_argument_deduction_constraint (tree t, tree args,
   tree pattern = DEDUCT_CONSTR_PATTERN (t);
   tree placeholder = DEDUCT_CONSTR_PLACEHOLDER (t);
   tree constr = PLACEHOLDER_TYPE_CONSTRAINTS (placeholder);
+  tree type_canonical = TYPE_CANONICAL (placeholder);
   PLACEHOLDER_TYPE_CONSTRAINTS (placeholder)
     = tsubst_constraint (constr, args, complain|tf_partial, in_decl);
+  TYPE_CANONICAL (placeholder) = NULL_TREE;
   tree type = do_auto_deduction (pattern, init, placeholder,
                                  complain, adc_requirement);
   PLACEHOLDER_TYPE_CONSTRAINTS (placeholder) = constr;
+  TYPE_CANONICAL (placeholder) = type_canonical;
   if (type == error_mark_node)
     return boolean_false_node;
 
diff --git a/gcc/testsuite/g++.dg/concepts/pr68683.C b/gcc/testsuite/g++.dg/concepts/pr68683.C
new file mode 100644
index 00000000000..a0d8fcf46b0
--- /dev/null
+++ b/gcc/testsuite/g++.dg/concepts/pr68683.C
@@ -0,0 +1,24 @@
+// { dg-options "-std=c++1z" }
+
+template <typename, typename>
+struct is_same {
+  static constexpr bool value = true;
+};
+
+template <typename T, typename U>
+concept bool Same = is_same<T, U>::value;
+
+template <typename T>
+concept bool Integral = requires {
+  { T () } -> Same<typename T::value_type>;
+};
+
+struct A {
+  using value_type = bool;
+};
+
+int main () {
+  Integral<A>;
+  Integral<A>;
+  return 0;
+}
-- 
2.30.2