Fix ClassCastException introduced in https://github.com/JetBrains/kotlin/commit/8d501bd7f4f1093bcf29165755aff3f2a945c88a

compiler/frontend/src/org/jetbrains/jet/lang/cfg/WhenChecker.java

@@ -96,8 +96,12 @@ public final class WhenChecker {
     ) {
         JetSimpleNameExpression reference = getReference(whenExpression.getExpression());
         if (reference == null) return false;
+
         DeclarationDescriptor target = trace.get(BindingContext.REFERENCE_TARGET, reference);
-        if (target == null) return false;
+        if (!(target instanceof VariableDescriptor)) {
+            return false;
+        }
+
         ClassDescriptor classDescriptor = trace.get(BindingContext.OBJECT_DECLARATION_CLASS, (VariableDescriptor) target);
         return classDescriptor == enumEntry;
     }

compiler/testData/diagnostics/tests/controlFlowAnalysis/kt1185enums.kt

@@ -9,6 +9,12 @@ enum class Direction {
     EAST
 }
 
+class A {
+    class object {
+
+    }
+}
+
 enum class Color(val rgb : Int) {
     RED : Color(0xFF0000)
     GREEN : Color(0x00FF00)
@@ -18,6 +24,7 @@ enum class Color(val rgb : Int) {
 fun foo(d: Direction) = when(d) { //no 'else' should be requested
     Direction.NORTH -> 1
     Direction.SOUTH -> 2
+    <!INCOMPATIBLE_TYPES!>A<!> -> 1
     Direction.WEST -> 3
     Direction.EAST -> 4
 }