DFA bug fix: assignment of unstable to stable uses predictable nullability (see test)

compiler/frontend/src/org/jetbrains/kotlin/resolve/calls/smartcasts/DelegatingDataFlowInfo.java

@@ -145,7 +145,7 @@ import static org.jetbrains.kotlin.resolve.calls.smartcasts.Nullability.NOT_NULL
     public Set<KotlinType> getPossibleTypes(@NotNull DataFlowValue key) {
         KotlinType originalType = key.getType();
         Set<KotlinType> types = collectTypesFromMeAndParents(key);
-        if (getNullability(key).canBeNull()) {
+        if (getPredictableNullability(key).canBeNull()) {
             return types;
         }
 
@@ -183,7 +183,7 @@ import static org.jetbrains.kotlin.resolve.calls.smartcasts.Nullability.NOT_NULL
     @NotNull
     public DataFlowInfo assign(@NotNull DataFlowValue a, @NotNull DataFlowValue b) {
         Map<DataFlowValue, Nullability> nullability = Maps.newHashMap();
-        Nullability nullabilityOfB = getNullability(b);
+        Nullability nullabilityOfB = getPredictableNullability(b);
         putNullability(nullability, a, nullabilityOfB);
 
         SetMultimap<DataFlowValue, KotlinType> newTypeInfo = newTypeInfo();
@@ -208,8 +208,8 @@ import static org.jetbrains.kotlin.resolve.calls.smartcasts.Nullability.NOT_NULL
     @NotNull
     public DataFlowInfo equate(@NotNull DataFlowValue a, @NotNull DataFlowValue b) {
         Map<DataFlowValue, Nullability> builder = Maps.newHashMap();
-        Nullability nullabilityOfA = getNullability(a);
-        Nullability nullabilityOfB = getNullability(b);
+        Nullability nullabilityOfA = getPredictableNullability(a);
+        Nullability nullabilityOfB = getPredictableNullability(b);
 
         boolean changed = false;
         changed |= putNullability(builder, a, nullabilityOfA.refine(nullabilityOfB));
@@ -267,8 +267,8 @@ import static org.jetbrains.kotlin.resolve.calls.smartcasts.Nullability.NOT_NULL
     @NotNull
     public DataFlowInfo disequate(@NotNull DataFlowValue a, @NotNull DataFlowValue b) {
         Map<DataFlowValue, Nullability> builder = Maps.newHashMap();
-        Nullability nullabilityOfA = getNullability(a);
-        Nullability nullabilityOfB = getNullability(b);
+        Nullability nullabilityOfA = getPredictableNullability(a);
+        Nullability nullabilityOfB = getPredictableNullability(b);
 
         boolean changed = false;
         changed |= putNullability(builder, a, nullabilityOfA.refine(nullabilityOfB.invert()));

compiler/testData/diagnostics/tests/smartCasts/unstableToStable.kt

@@ -0,0 +1,18 @@
+class Foo(var x: Int?) {
+    init {
+        if (x != null) {
+            val y = x
+            // Error: x is not stable, Type(y) = Int?
+            <!SMARTCAST_IMPOSSIBLE!>x<!>.hashCode()
+            y<!UNSAFE_CALL!>.<!>hashCode()
+            if (y == x) {
+                // Still error
+                y<!UNSAFE_CALL!>.<!>hashCode()
+            }
+            if (x == null && y != x) {
+                // Still error
+                y<!UNSAFE_CALL!>.<!>hashCode()
+            }
+        }
+    }
+}

compiler/testData/diagnostics/tests/smartCasts/unstableToStable.txt

@@ -0,0 +1,9 @@
+package
+
+public final class Foo {
+    public constructor Foo(/*0*/ x: kotlin.Int?)
+    public final var x: kotlin.Int?
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}

compiler/tests/org/jetbrains/kotlin/checkers/DiagnosticsTestGenerated.java

@@ -15060,6 +15060,12 @@ public class DiagnosticsTestGenerated extends AbstractDiagnosticsTest {
                 doTest(fileName);
             }
 
+            @TestMetadata("unstableToStable.kt")
+            public void testUnstableToStable() throws Exception {
+                String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/smartCasts/unstableToStable.kt");
+                doTest(fileName);
+            }
+
             @TestMetadata("varChangedInInitializer.kt")
             public void testVarChangedInInitializer() throws Exception {
                 String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/smartCasts/varChangedInInitializer.kt");