[flang] Make use of is_same<>

Original-commit: flang-compiler/f18@12cd530865
Reviewed-on: https://github.com/flang-compiler/f18/pull/170
Tree-same-pre-rewrite: false

flang/test/semantics/label10.f90

@@ -0,0 +1,23 @@
+! Copyright (c) 2018, NVIDIA CORPORATION.  All rights reserved.
+!
+! Licensed under the Apache License, Version 2.0 (the "License");
+! you may not use this file except in compliance with the License.
+! You may obtain a copy of the License at
+!
+!     http://www.apache.org/licenses/LICENSE-2.0
+!
+! Unless required by applicable law or agreed to in writing, software
+! distributed under the License is distributed on an "AS IS" BASIS,
+! WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+! See the License for the specific language governing permissions and
+! limitations under the License.
+
+! RUN: f18 < %s | FileCheck %s
+! CHECK: 
+
+subroutine s(a)
+  real a(10)
+  write(*,60) "Hi there"
+60 continue
+70 format (i8)
+end subroutine s