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

+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

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 ();

gcc/testsuite/g++.dg/cpp1z/class-deduction49.C

+// 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);