More precise diagnostics of smart cast impossible #KT-7240 Fixed

compiler/frontend/src/org/jetbrains/kotlin/resolve/calls/CandidateResolver.kt

@@ -475,7 +475,7 @@ public class CandidateResolver(
 
         val bindingContext = trace.bindingContext
         val receiverValue = DataFlowValueFactory.createDataFlowValue(receiverArgument, bindingContext, scope.ownerDescriptor)
-        if (safeAccess && !dataFlowInfo.getNullability(receiverValue).canBeNull()) {
+        if (safeAccess && !dataFlowInfo.getPredictableNullability(receiverValue).canBeNull()) {
             tracing.unnecessarySafeCall(trace, receiverArgument.type)
         }
 

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

@@ -37,9 +37,19 @@ public interface DataFlowInfo {
     @NotNull
     SetMultimap<DataFlowValue, KotlinType> getCompleteTypeInfo();
 
+    /**
+     * Returns collected nullability for the given value, NOT taking its predictability into account.
+     */
     @NotNull
     Nullability getNullability(@NotNull DataFlowValue key);
 
+    /**
+     * Returns collected nullability for the given value if it's predictable.
+     * Otherwise basic value nullability is returned
+     */
+    @NotNull
+    Nullability getPredictableNullability(@NotNull DataFlowValue key);
+
     /**
      * IMPORTANT: by default, the original (native) type for this value
      * are NOT included. So it's quite possible to get an empty set here.

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

@@ -111,7 +111,18 @@ import static org.jetbrains.kotlin.resolve.calls.smartcasts.Nullability.NOT_NULL
     @Override
     @NotNull
     public Nullability getNullability(@NotNull DataFlowValue key) {
-        if (!key.isPredictable()) return key.getImmanentNullability();
+        return getNullability(key, false);
+    }
+
+    @Override
+    @NotNull
+    public Nullability getPredictableNullability(@NotNull DataFlowValue key) {
+        return getNullability(key, true);
+    }
+
+    @NotNull
+    private Nullability getNullability(@NotNull DataFlowValue key, boolean predictableOnly) {
+        if (predictableOnly && !key.isPredictable()) return key.getImmanentNullability();
         Nullability nullability = nullabilityInfo.get(key);
         return nullability != null ? nullability :
                parent != null ? parent.getNullability(key) :
@@ -123,7 +134,6 @@ import static org.jetbrains.kotlin.resolve.calls.smartcasts.Nullability.NOT_NULL
             @NotNull DataFlowValue value,
             @NotNull Nullability nullability
     ) {
-        if (!value.isPredictable()) return false;
         map.put(value, nullability);
         return nullability != getNullability(value);
     }

compiler/frontend/src/org/jetbrains/kotlin/types/expressions/BasicExpressionTypingVisitor.java

@@ -892,7 +892,7 @@ public class BasicExpressionTypingVisitor extends ExpressionTypingVisitor {
 
     private static boolean isKnownToBeNotNull(KtExpression expression, KotlinType jetType, ExpressionTypingContext context) {
         DataFlowValue dataFlowValue = createDataFlowValue(expression, jetType, context);
-        return !context.dataFlowInfo.getNullability(dataFlowValue).canBeNull();
+        return !context.dataFlowInfo.getPredictableNullability(dataFlowValue).canBeNull();
     }
 
     /**
@@ -1191,7 +1191,7 @@ public class BasicExpressionTypingVisitor extends ExpressionTypingVisitor {
             DataFlowInfo rightDataFlowInfo = resolvedCall.getDataFlowInfoForArguments().getResultInfo();
             // left argument is considered not-null if it's not-null also in right part or if we have jump in right part
             if ((rightType != null && KotlinBuiltIns.isNothingOrNullableNothing(rightType) && !rightType.isMarkedNullable())
-                || !rightDataFlowInfo.getNullability(leftValue).canBeNull()) {
+                || !rightDataFlowInfo.getPredictableNullability(leftValue).canBeNull()) {
                 dataFlowInfo = dataFlowInfo.disequate(leftValue, DataFlowValue.nullValue(components.builtIns));
             }
         }
@@ -1298,7 +1298,7 @@ public class BasicExpressionTypingVisitor extends ExpressionTypingVisitor {
                         new Function1<DataFlowValue, Nullability>() {
                             @Override
                             public Nullability invoke(DataFlowValue value) {
-                                return context.dataFlowInfo.getNullability(value);
+                                return context.dataFlowInfo.getPredictableNullability(value);
                             }
                         });
             }