Add some data flow analysis tests on when

compiler/testData/diagnostics/tests/when/withSubjectVariable/smartcastToEnum.kt

@@ -0,0 +1,23 @@
+// !LANGUAGE: +VariableDeclarationInWhenSubject
+// !DIAGNOSTICS: -UNUSED_VARIABLE
+
+enum class E { FIRST, SECOND }
+
+fun testSmartcastToEnumInSubjectInitializer(e: E?) {
+    val x = <!NO_ELSE_IN_WHEN!>when<!> (val ne = e!!) { // TODO fix
+        E.FIRST -> "f"
+        E.SECOND -> "s"
+    }
+}
+
+
+sealed class Either
+class Left : Either()
+class Right : Either()
+
+fun testSmartcastToSealedInSubjectInitializer(x: Any?) {
+    val y = <!NO_ELSE_IN_WHEN!>when<!> (val either = x as Either) { // TODO fix
+        is Left -> "L"
+        is Right -> "R"
+    }
+}