Tests: use helper function to assert compile-time and run-time type check

To cleanup warnings about useless cast or type check that is always true.

libraries/stdlib/test/internalAnnotations.kt

@@ -0,0 +1,22 @@
+/*
+ * Copyright 2010-2017 JetBrains s.r.o.
+ *
+ * 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.
+ */
+
+package kotlin.internal
+
+// to compile tests in jre/jdk/7/8 projects where stdlib internals are unavailable
+@Target(AnnotationTarget.TYPE)
+@Retention(AnnotationRetention.BINARY)
+internal annotation class NoInfer