JS: move expressions test to box tests

js/js.translator/testData/box/expression/cast/safeCastToReifiedNullable.kt

@@ -0,0 +1,21 @@
+package foo
+
+// CHECK_NOT_CALLED: castTo
+
+class A
+class B
+
+inline
+fun <reified T> Any?.castTo(): T? = this as? T?
+
+fun box(): String {
+    val a: Any? = A()
+    val nil: Any? = null
+    val b: Any? = B()
+
+    assertEquals(a, a.castTo<A>(), "a")
+    assertEquals(null, nil.castTo<A>(), "nil")
+    assertEquals(null, b.castTo<A>(), "b")
+
+    return "OK"
+}