PR c++/85135 - ICE with omitted template arguments.

	* decl.c (grokdeclarator): Catch deduced class type in trailing
	return type.

From-SVN: r259092

gcc/cp/ChangeLog

 2018-04-04  Jason Merrill  <jason@redhat.com>
 
+	PR c++/85135 - ICE with omitted template arguments.
+	* decl.c (grokdeclarator): Catch deduced class type in trailing
+	return type.
+
 	PR c++/85133 - ICE with missing concept initializer.
 	* decl.c (cp_finish_decl): If a concept initializer is missing, use
 	true.

gcc/cp/decl.c

@@ -11100,20 +11100,29 @@ grokdeclarator (const cp_declarator *declarator,
 			       name, type);
 			return error_mark_node;
 		      }
-		    if (tree tmpl = CLASS_PLACEHOLDER_TEMPLATE (auto_node))
+		    tree tmpl = CLASS_PLACEHOLDER_TEMPLATE (auto_node);
+		    if (!tmpl)
+		      if (tree late_auto = type_uses_auto (late_return_type))
+			tmpl = CLASS_PLACEHOLDER_TEMPLATE (late_auto);
+		    if (tmpl)
 		      {
-			if (!late_return_type)
+			if (!dguide_name_p (unqualified_id))
 			  {
-			    if (dguide_name_p (unqualified_id))
-			      error_at (declarator->id_loc, "deduction guide "
-					"for %qT must have trailing return "
-					"type", TREE_TYPE (tmpl));
-			    else
-			      error_at (declarator->id_loc, "deduced class "
-					"type %qT in function return type",
-					type);
+			    error_at (declarator->id_loc, "deduced class "
+				      "type %qD in function return type",
+				      DECL_NAME (tmpl));
 			    inform (DECL_SOURCE_LOCATION (tmpl),
 				    "%qD declared here", tmpl);
+			    return error_mark_node;
+			  }
+			else if (!late_return_type)
+			  {
+			    error_at (declarator->id_loc, "deduction guide "
+				      "for %qT must have trailing return "
+				      "type", TREE_TYPE (tmpl));
+			    inform (DECL_SOURCE_LOCATION (tmpl),
+				    "%qD declared here", tmpl);
+			    return error_mark_node;
 			  }
 			else if (CLASS_TYPE_P (late_return_type)
 				 && CLASSTYPE_TEMPLATE_INFO (late_return_type)

gcc/testsuite/g++.dg/cpp1z/class-deduction53.C

+// PR c++/85135
+// { dg-do compile { target c++11 } }
+
+template<int> struct A {};
+
+auto foo() -> A;		// { dg-error "A" }
+
+template<typename> struct B {};
+
+auto foo() -> A;		// { dg-error "A" }