PR c++/80096 - ICE with C++17 non-type auto.

	* pt.c (tsubst): Delay tsubst of type of template non-type
	parameter.

From-SVN: r246292

gcc/cp/ChangeLog

 2017-03-20  Jason Merrill  <jason@redhat.com>
 
+	PR c++/80096 - ICE with C++17 non-type auto.
+	* pt.c (tsubst): Delay tsubst of type of template non-type
+	parameter.
+
 	PR c++/79519 - ICE with deleted template friend.
 	* decl.c (grokdeclarator): Complain about misplaced function
 	definition using =, as well.

gcc/cp/pt.c

@@ -13388,6 +13388,7 @@ tsubst (tree t, tree args, tsubst_flags_t complain, tree in_decl)
   if (type
       && code != TYPENAME_TYPE
       && code != TEMPLATE_TYPE_PARM
+      && code != TEMPLATE_PARM_INDEX
       && code != IDENTIFIER_NODE
       && code != FUNCTION_TYPE
       && code != METHOD_TYPE)
@@ -13690,6 +13691,10 @@ tsubst (tree t, tree args, tsubst_flags_t complain, tree in_decl)
 	    break;
 
 	  case TEMPLATE_PARM_INDEX:
+	    /* OK, now substitute the type of the non-type parameter.  We
+	       couldn't do it earlier because it might be an auto parameter,
+	       and we wouldn't need to if we had an argument.  */
+	    type = tsubst (type, args, complain, in_decl);
 	    r = reduce_template_parm_level (t, type, levels, args, complain);
 	    break;
 

gcc/testsuite/g++.dg/cpp1z/nontype-auto10.C

+// PR c++/80096
+// { dg-options -std=c++1z }
+
+template<auto> struct A
+{
+  template<int> struct B {};
+};
+
+A<0> a;