JET-183 Typechecker fails with enum constants

+
Tests for annotations

idea/testData/checker/regression/Jet183-1.jet

@@ -0,0 +1,21 @@
+enum class ProtocolState {
+  WAITING {
+    override fun signal() = ProtocolState.TALKING
+  }
+
+  TALKING {
+    override fun signal() = ProtocolState.WAITING
+  }
+
+  abstract fun signal() : ProtocolState
+}
+
+
+fun box(): String {
+   val x: ProtocolState = ProtocolState.WAITING
+   x = x.signal()
+   if (x != ProtocolState.TALKING) return "fail 1"
+   x = x.signal()
+   if (x != ProtocolState.WAITING) return "fail 2"
+   return "OK"
+}