PR c++/84080 - ICE with return type deduction and specialization.

	* pt.c (determine_specialization): Check uses_template_parms.

From-SVN: r257630

gcc/cp/ChangeLog

 2018-02-13  Jason Merrill  <jason@redhat.com>
 
+	PR c++/84080 - ICE with return type deduction and specialization.
+	* pt.c (determine_specialization): Check uses_template_parms.
+
 	Fix more variadic capture issues.
 	* pt.c (find_parameter_packs_r): Also look at explicit captures.
 	(check_for_bare_parameter_packs): Check current_class_type for

gcc/cp/pt.c

@@ -2203,6 +2203,11 @@ determine_specialization (tree template_id,
 	       specialize TMPL will produce DECL.  */
 	    continue;
 
+	  if (uses_template_parms (targs))
+	    /* We deduced something involving 'auto', which isn't a valid
+	       template argument.  */
+	    continue;
+
           /* Remove, from the set of candidates, all those functions
              whose constraints are not satisfied. */
           if (flag_concepts && !constraints_satisfied_p (fn, targs))

gcc/testsuite/g++.dg/cpp1y/auto-fn47.C

+// PR c++/84080
+// { dg-do compile { target c++14 } }
+
+template <int i, typename T> T foo();
+
+template <> auto foo<0>() { return 42; } // { dg-error "does not match" }