Values equality no more provides guarantee for their types equality (for open types or types with overridden equals) #KT-11280 Fixed

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

@@ -70,9 +70,10 @@ interface DataFlowInfo {
     fun assign(a: DataFlowValue, b: DataFlowValue): DataFlowInfo
 
     /**
-     * Call this function when it's known than a == b
+     * Call this function when it's known than a == b.
+     * sameTypes should be true iff we have guarantee that a and b have the same type
      */
-    fun equate(a: DataFlowValue, b: DataFlowValue): DataFlowInfo
+    fun equate(a: DataFlowValue, b: DataFlowValue, sameTypes: Boolean): DataFlowInfo
 
     /**
      * Call this function when it's known than a != b

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

@@ -151,7 +151,7 @@ internal class DelegatingDataFlowInfo private constructor(
         return create(this, ImmutableMap.copyOf(nullability), if (newTypeInfo.isEmpty) EMPTY_TYPE_INFO else newTypeInfo, a)
     }
 
-    override fun equate(a: DataFlowValue, b: DataFlowValue): DataFlowInfo {
+    override fun equate(a: DataFlowValue, b: DataFlowValue, sameTypes: Boolean): DataFlowInfo {
         val builder = Maps.newHashMap<DataFlowValue, Nullability>()
         val nullabilityOfA = getPredictableNullability(a)
         val nullabilityOfB = getPredictableNullability(b)
@@ -159,19 +159,22 @@ internal class DelegatingDataFlowInfo private constructor(
         var changed = putNullability(builder, a, nullabilityOfA.refine(nullabilityOfB)) or
                       putNullability(builder, b, nullabilityOfB.refine(nullabilityOfA))
 
+        // NB: == has no guarantees of type equality, see KT-11280 for the example
         val newTypeInfo = newTypeInfo()
-        newTypeInfo.putAll(a, getPredictableTypes(b, false))
-        newTypeInfo.putAll(b, getPredictableTypes(a, false))
-        if (a.type != b.type) {
-            // To avoid recording base types of own type
-            if (!a.type.isSubtypeOf(b.type)) {
-                newTypeInfo.put(a, b.type)
-            }
-            if (!b.type.isSubtypeOf(a.type)) {
-                newTypeInfo.put(b, a.type)
+        if (sameTypes) {
+            newTypeInfo.putAll(a, getPredictableTypes(b, false))
+            newTypeInfo.putAll(b, getPredictableTypes(a, false))
+            if (a.type != b.type) {
+                // To avoid recording base types of own type
+                if (!a.type.isSubtypeOf(b.type)) {
+                    newTypeInfo.put(a, b.type)
+                }
+                if (!b.type.isSubtypeOf(a.type)) {
+                    newTypeInfo.put(b, a.type)
+                }
             }
+            changed = changed or !newTypeInfo.isEmpty
         }
-        changed = changed or !newTypeInfo.isEmpty
 
         return if (!changed) {
             this

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

@@ -22,20 +22,25 @@ import com.intellij.psi.tree.IElementType;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 import org.jetbrains.kotlin.builtins.KotlinBuiltIns;
+import org.jetbrains.kotlin.descriptors.*;
 import org.jetbrains.kotlin.diagnostics.DiagnosticUtilsKt;
+import org.jetbrains.kotlin.incremental.KotlinLookupLocation;
 import org.jetbrains.kotlin.lexer.KtTokens;
 import org.jetbrains.kotlin.psi.*;
 import org.jetbrains.kotlin.resolve.BindingContext;
 import org.jetbrains.kotlin.resolve.BindingTrace;
+import org.jetbrains.kotlin.resolve.DescriptorUtils;
 import org.jetbrains.kotlin.resolve.calls.checkers.AdditionalTypeChecker;
 import org.jetbrains.kotlin.resolve.calls.context.ResolutionContext;
 import org.jetbrains.kotlin.resolve.calls.smartcasts.*;
 import org.jetbrains.kotlin.resolve.constants.*;
 import org.jetbrains.kotlin.resolve.constants.evaluate.ConstantExpressionEvaluator;
 import org.jetbrains.kotlin.types.KotlinType;
+import org.jetbrains.kotlin.types.TypeConstructor;
 import org.jetbrains.kotlin.types.TypeUtils;
 import org.jetbrains.kotlin.types.checker.KotlinTypeChecker;
 import org.jetbrains.kotlin.types.expressions.typeInfoFactory.TypeInfoFactoryKt;
+import org.jetbrains.kotlin.util.OperatorNameConventions;
 
 import java.util.Collection;
 
@@ -65,9 +70,52 @@ public class DataFlowAnalyzer {
         this.facade = facade;
     }
 
+    // NB: use this method only for functions from 'Any'
+    @Nullable
+    private static FunctionDescriptor getOverriddenDescriptorFromClass(@NotNull FunctionDescriptor descriptor) {
+        if (descriptor.getKind() != CallableMemberDescriptor.Kind.FAKE_OVERRIDE) return descriptor;
+        Collection<? extends FunctionDescriptor> overriddenDescriptors = descriptor.getOverriddenDescriptors();
+        if (overriddenDescriptors.isEmpty()) return descriptor;
+        for (FunctionDescriptor overridden : overriddenDescriptors) {
+            DeclarationDescriptor containingDeclaration = overridden.getContainingDeclaration();
+            if (DescriptorUtils.isClass(containingDeclaration) || DescriptorUtils.isObject(containingDeclaration)) {
+                // Exactly one class should exist in the list
+                return getOverriddenDescriptorFromClass(overridden);
+            }
+        }
+        return null;
+    }
+
+    private static boolean typeHasOverriddenEquals(@NotNull KotlinType type, @NotNull KtElement lookupElement) {
+        Collection<FunctionDescriptor> members = type.getMemberScope().getContributedFunctions(
+                OperatorNameConventions.EQUALS, new KotlinLookupLocation(lookupElement));
+        for (FunctionDescriptor member : members) {
+            KotlinType returnType = member.getReturnType();
+            if (returnType == null || !KotlinBuiltIns.isBoolean(returnType)) continue;
+            if (member.getValueParameters().size() != 1) continue;
+            KotlinType parameterType = member.getValueParameters().iterator().next().getType();
+            if (!KotlinBuiltIns.isNullableAny(parameterType)) continue;
+            FunctionDescriptor fromSuperClass = getOverriddenDescriptorFromClass(member);
+            if (fromSuperClass == null) return false;
+            ClassifierDescriptor superClassDescriptor = (ClassifierDescriptor) fromSuperClass.getContainingDeclaration();
+            // We should have override fun in class other than Any (to prove unknown behaviour)
+            return !KotlinBuiltIns.isAnyOrNullableAny(superClassDescriptor.getDefaultType());
+        }
+        return false;
+    }
+
+    // Returns true if we can prove that 'type' has equals method from 'Any' base type
+    public static boolean typeHasEqualsFromAny(@NotNull KotlinType type, @NotNull KtElement lookupElement) {
+        TypeConstructor constructor = type.getConstructor();
+        // Subtypes can override equals for non-final types
+        if (!constructor.isFinal()) return false;
+        // check whether 'equals' is overriden
+        return !typeHasOverriddenEquals(type, lookupElement);
+    }
+
     @NotNull
     public DataFlowInfo extractDataFlowInfoFromCondition(
-            @Nullable KtExpression condition,
+            @Nullable final KtExpression condition,
             final boolean conditionValue,
             final ExpressionTypingContext context
     ) {
@@ -126,7 +174,9 @@ public class DataFlowAnalyzer {
                     }
                     if (equals != null) {
                         if (equals == conditionValue) { // this means: equals && conditionValue || !equals && !conditionValue
-                            result.set(context.dataFlowInfo.equate(leftValue, rightValue).and(expressionFlowInfo));
+                            boolean byIdentity = operationToken == KtTokens.EQEQEQ || operationToken == KtTokens.EXCLEQEQEQ ||
+                                                 typeHasEqualsFromAny(lhsType, condition);
+                            result.set(context.dataFlowInfo.equate(leftValue, rightValue, byIdentity).and(expressionFlowInfo));
                         }
                         else {
                             result.set(context.dataFlowInfo.disequate(leftValue, rightValue).and(expressionFlowInfo));

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

@@ -335,7 +335,8 @@ class PatternMatchingTypingVisitor internal constructor(facade: ExpressionTyping
         val expressionDataFlowValue = DataFlowValueFactory.createDataFlowValue(expression, type, newContext)
         val result = noChange(newContext)
         return ConditionalDataFlowInfo(
-                result.thenInfo.equate(subjectDataFlowValue, expressionDataFlowValue),
+                result.thenInfo.equate(subjectDataFlowValue, expressionDataFlowValue,
+                                       DataFlowAnalyzer.typeHasEqualsFromAny(subjectType, expression)),
                 result.elseInfo.disequate(subjectDataFlowValue, expressionDataFlowValue))
     }
 

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

@@ -0,0 +1,95 @@
+abstract class Base {
+    override fun equals(other: Any?) = other is Base
+}
+
+class Derived1 : Base() {
+    fun foo() {}
+}
+
+class Derived2 : Base()
+
+fun check(x1: Derived1, x: Base) {
+    if (x1 == x) {
+        // Smart cast here will provoke CCA
+        x.<!UNRESOLVED_REFERENCE!>foo<!>()
+    }
+    if (x1 === x) {
+        // OK
+        <!DEBUG_INFO_SMARTCAST!>x<!>.foo()
+    }
+    if (x1 !== x) {} else {
+        // OK
+        <!DEBUG_INFO_SMARTCAST!>x<!>.foo()
+    }
+}
+
+class FinalClass { // <-- 'equals' on instances of this class is useful for smart casts
+    fun use() {}
+
+    fun equals(x: Int): Boolean = x > 42
+}
+
+fun foo(x: FinalClass?, y: Any) {
+    if (x == y) {
+        // OK
+        <!DEBUG_INFO_SMARTCAST!>x<!>.hashCode()
+        // OK
+        <!DEBUG_INFO_SMARTCAST!>y<!>.use()
+    }
+    when (x) {
+        // OK (equals from FinalClass)
+        y -> <!DEBUG_INFO_SMARTCAST!>y<!>.use()
+    }
+    when (y) {
+        // ERROR (equals from Any)
+        x -> y.<!UNRESOLVED_REFERENCE!>use<!>()
+    }
+}
+
+open class OpenClass {
+    override fun equals(other: Any?) = other is OpenClass
+}
+
+interface Dummy // should not influence anything
+
+class FinalClass2 : Dummy, OpenClass() { // but here not
+    fun use() {}
+}
+
+fun bar(x: FinalClass2?, y: Any) {
+    if (x == y) {
+        // OK
+        <!DEBUG_INFO_SMARTCAST!>x<!>.hashCode()
+        // ERROR
+        y.<!UNRESOLVED_REFERENCE!>use<!>()
+    }
+}
+
+open class OpenClass2 // and here too
+
+fun bar(x: OpenClass2?, y: Any) {
+    if (x == y) {
+        // OK
+        <!DEBUG_INFO_SMARTCAST!>x<!>.hashCode()
+        // ERROR
+        y.<!UNRESOLVED_REFERENCE!>use<!>()
+    }
+}
+
+sealed class Sealed {
+    override fun equals(other: Any?) = other is Sealed
+
+    class Sealed1 : Sealed() {
+        fun gav() {}
+    }
+
+    object Sealed2 : Sealed()
+
+    fun check(arg: Sealed1) {
+        if (arg == this) {
+            // Smart cast here will provoke CCA
+            this.<!UNRESOLVED_REFERENCE!>gav<!>()
+            <!UNRESOLVED_REFERENCE!>gav<!>()
+        }
+    }
+}

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

@@ -0,0 +1,90 @@
+package
+
+public fun bar(/*0*/ x: FinalClass2?, /*1*/ y: kotlin.Any): kotlin.Unit
+public fun bar(/*0*/ x: OpenClass2?, /*1*/ y: kotlin.Any): kotlin.Unit
+public fun check(/*0*/ x1: Derived1, /*1*/ x: Base): kotlin.Unit
+public fun foo(/*0*/ x: FinalClass?, /*1*/ y: kotlin.Any): kotlin.Unit
+
+public abstract class Base {
+    public constructor Base()
+    public open override /*1*/ 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
+}
+
+public final class Derived1 : Base {
+    public constructor Derived1()
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public final fun foo(): kotlin.Unit
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public final class Derived2 : Base {
+    public constructor Derived2()
+    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
+}
+
+public interface Dummy {
+    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
+}
+
+public final class FinalClass {
+    public constructor FinalClass()
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public final fun equals(/*0*/ x: kotlin.Int): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+    public final fun use(): kotlin.Unit
+}
+
+public final class FinalClass2 : Dummy, OpenClass {
+    public constructor FinalClass2()
+    public open override /*2*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*2*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*2*/ /*fake_override*/ fun toString(): kotlin.String
+    public final fun use(): kotlin.Unit
+}
+
+public open class OpenClass {
+    public constructor OpenClass()
+    public open override /*1*/ 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
+}
+
+public open class OpenClass2 {
+    public constructor OpenClass2()
+    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
+}
+
+public sealed class Sealed {
+    private constructor Sealed()
+    public final fun check(/*0*/ arg: Sealed.Sealed1): kotlin.Unit
+    public open override /*1*/ 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
+
+    public final class Sealed1 : Sealed {
+        public constructor Sealed1()
+        public final override /*1*/ /*fake_override*/ fun check(/*0*/ arg: Sealed.Sealed1): kotlin.Unit
+        public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        public final fun gav(): kotlin.Unit
+        public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+    }
+
+    public object Sealed2 : Sealed {
+        private constructor Sealed2()
+        public final override /*1*/ /*fake_override*/ fun check(/*0*/ arg: Sealed.Sealed1): kotlin.Unit
+        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/testData/diagnostics/tests/smartCasts/typeInComparison.kt

@@ -2,7 +2,7 @@ fun foo(): Int {
     val x: Any? = null
     val y = 2
     if (x == y) {
-        return <!DEBUG_INFO_SMARTCAST!>x<!> + y
+        return x <!UNRESOLVED_REFERENCE_WRONG_RECEIVER!>+<!> y
     }
     return y
 }

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

@@ -16170,6 +16170,12 @@ public class DiagnosticsTestGenerated extends AbstractDiagnosticsTest {
                 doTest(fileName);
             }
 
+            @TestMetadata("fakeSmartCastOnEquality.kt")
+            public void testFakeSmartCastOnEquality() throws Exception {
+                String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/smartCasts/fakeSmartCastOnEquality.kt");
+                doTest(fileName);
+            }
+
             @TestMetadata("falseReceiverSmartCast.kt")
             public void testFalseReceiverSmartCast() throws Exception {
                 String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/smartCasts/falseReceiverSmartCast.kt");