[Tests] Migrate backend-independent tests from native to compiler/testData.

^KT-65979

compiler/testData/codegen/box/basics/safe_cast.kt

@@ -0,0 +1,31 @@
+/*
+ * Copyright 2010-2018 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license
+ * that can be found in the LICENSE file.
+ */
+// WITH_STDLIB
+import kotlin.test.*
+
+open class A
+class B : A()
+class C
+
+fun foo(a: Any) : A? = a as? A
+
+fun safe_cast_positive(): Boolean {
+  val b = B()
+  return foo(b) === b
+}
+
+fun safe_cast_negative(): Boolean {
+  val c = C()
+  return foo(c) == null
+}
+
+fun box(): String {
+  val safeCastPositive = safe_cast_positive().toString()
+  val safeCastNegative = safe_cast_negative().toString()
+  if (safeCastPositive != "true") return "FAIL safeCastPositive"
+  if (safeCastNegative != "true") return "FAIL safeCastNegative"
+
+  return "OK"
+}