Pattern matching: work-around for smart cast target type instability #KT-14705 Fixed

compiler/frontend/src/org/jetbrains/kotlin/types/expressions/PatternMatchingTypingVisitor.kt

@@ -245,15 +245,6 @@ class PatternMatchingTypingVisitor internal constructor(facade: ExpressionTyping
             possibleTypesForSubject: Set<KotlinType>
     ) {
         val subjectExpression = expression.subjectExpression ?: return
-        val isNullableType = TypeUtils.isNullableType(subjectType)
-        val bindingContext = contextBeforeSubject.trace.bindingContext
-        if (isNullableType && !WhenChecker.containsNullCase(expression, bindingContext)) {
-            val notNullableType = TypeUtils.makeNotNullable(subjectType)
-            if (checkSmartCastToExpectedTypeInSubject(contextBeforeSubject, subjectExpression, subjectType,
-                                                      notNullableType)) {
-                return
-            }
-        }
         for (possibleCastType in possibleTypesForSubject) {
             val possibleCastClass = possibleCastType.constructor.declarationDescriptor as? ClassDescriptor ?: continue
             if (possibleCastClass.kind == ClassKind.ENUM_CLASS || possibleCastClass.modality == Modality.SEALED) {
@@ -263,6 +254,15 @@ class PatternMatchingTypingVisitor internal constructor(facade: ExpressionTyping
                 }
             }
         }
+        val isNullableType = TypeUtils.isNullableType(subjectType)
+        val bindingContext = contextBeforeSubject.trace.bindingContext
+        if (isNullableType && !WhenChecker.containsNullCase(expression, bindingContext)) {
+            val notNullableType = TypeUtils.makeNotNullable(subjectType)
+            if (checkSmartCastToExpectedTypeInSubject(contextBeforeSubject, subjectExpression, subjectType,
+                                                      notNullableType)) {
+                return
+            }
+        }
     }
 
     private fun checkSmartCastToExpectedTypeInSubject(

idea/testData/checker/infos/SmartCastToEnum.kt

@@ -0,0 +1,14 @@
+package test2
+
+<info descr="null">enum</info> class En { A, B, С }
+
+fun main(args: Array<String>) {
+    val en2: Any? = En.A
+    if (en2 is En) {
+        when (<info descr="Smart cast to test2.En">en2</info>) {
+            En.A -> {}
+            En.B -> {}
+            En.С -> {}
+        }
+    }
+}

idea/tests/org/jetbrains/kotlin/checkers/PsiCheckerTestGenerated.java

@@ -917,6 +917,12 @@ public class PsiCheckerTestGenerated extends AbstractPsiCheckerTest {
             doTestWithInfos(fileName);
         }
 
+        @TestMetadata("SmartCastToEnum.kt")
+        public void testSmartCastToEnum() throws Exception {
+            String fileName = KotlinTestUtils.navigationMetadata("idea/testData/checker/infos/SmartCastToEnum.kt");
+            doTestWithInfos(fileName);
+        }
+
         @TestMetadata("SmartCasts.kt")
         public void testSmartCasts() throws Exception {
             String fileName = KotlinTestUtils.navigationMetadata("idea/testData/checker/infos/SmartCasts.kt");