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

^KT-65979

compiler/testData/codegen/box/boxing/boxing6.kt

@@ -0,0 +1,28 @@
+/*
+ * 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.
+ */
+// JVM_ABI_K1_K2_DIFF: KT-63864
+// WITH_STDLIB
+
+import kotlin.test.*
+
+val sb = StringBuilder()
+
+fun printInt(x: Int) = sb.appendLine(x)
+
+fun foo(arg: Any) {
+    printInt(arg as? Int ?: 16)
+}
+
+fun box(): String {
+    foo(42)
+    foo("Hello")
+    val nonConstInt = 42
+    val nonConstString = "Hello"
+    foo(nonConstInt)
+    foo(nonConstString)
+
+    assertEquals("42\n16\n42\n16\n", sb.toString())
+    return "OK"
+}