Renamed *.jet to *.kt in test data of JetPsiCheckerTest.

idea/testData/checker/regression/Jet183.kt

@@ -0,0 +1,22 @@
+abstract enum class ProtocolState {
+  WAITING {
+    override fun signal() = ProtocolState.TALKING
+  }
+
+  TALKING {
+    override fun signal() = ProtocolState.WAITING
+  }
+
+  abstract fun signal() : ProtocolState
+}
+
+enum class Foo<T> {
+  <error>X</error>
+
+}
+
+
+
+fun box() {
+   val <warning>x</warning>: ProtocolState = ProtocolState.WAITING
+}