From a8a3f32d583d9fde8e94c11c118c47c702bdea04 Mon Sep 17 00:00:00 2001
From: Jason Merrill <jason@redhat.com>
Date: Mon, 26 Feb 2018 00:05:15 -0500
Subject: [PATCH] PR c++/84015 - ICE with class deduction and auto template
 parm.

	* pt.c (rewrite_template_parm): Use tf_partial in first tsubst.

From-SVN: r257979
---
 gcc/cp/ChangeLog                               |  5 +++++
 gcc/cp/pt.c                                    |  2 +-
 gcc/testsuite/g++.dg/cpp1z/class-deduction49.C | 15 +++++++++++++++
 3 files changed, 21 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/g++.dg/cpp1z/class-deduction49.C

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index 3d4c946ad16..cb0dcd7c43e 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,8 @@
+2018-02-25  Jason Merrill  <jason@redhat.com>
+
+	PR c++/84015 - ICE with class deduction and auto template parm.
+	* pt.c (rewrite_template_parm): Use tf_partial in first tsubst.
+
 2018-02-24  Marek Polacek  <polacek@redhat.com>
 
 	PR c++/83692
diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index 85d1adbbe3c..9cf96e9fbe4 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -25596,7 +25596,7 @@ rewrite_template_parm (tree olddecl, unsigned index, unsigned level,
 	  // Substitute ttargs into ttparms to fix references to
 	  // other template parameters.
 	  ttparms = tsubst_template_parms_level (ttparms, ttargs,
-						 complain);
+						 complain|tf_partial);
 	  // Now substitute again with args based on tparms, to reduce
 	  // the level of the ttparms.
 	  ttargs = current_template_args ();
diff --git a/gcc/testsuite/g++.dg/cpp1z/class-deduction49.C b/gcc/testsuite/g++.dg/cpp1z/class-deduction49.C
new file mode 100644
index 00000000000..086f12ad3c6
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1z/class-deduction49.C
@@ -0,0 +1,15 @@
+// PR c++/84015
+// { dg-additional-options -std=c++17 }
+
+template <int I>
+struct A { };
+
+template <int I>
+struct B
+{
+  template<template<auto>class T>
+  B(T<I>);
+};
+
+A<42> a;
+B b (a);
-- 
2.30.2