Support smart cast for nullability in LHS of class literal

#KT-16291 Fixed

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

@@ -40,6 +40,7 @@ import org.jetbrains.kotlin.resolve.calls.context.*
 import org.jetbrains.kotlin.resolve.calls.results.OverloadResolutionResults
 import org.jetbrains.kotlin.resolve.calls.results.OverloadResolutionResultsUtil
 import org.jetbrains.kotlin.resolve.calls.smartcasts.DataFlowInfo
+import org.jetbrains.kotlin.resolve.calls.smartcasts.DataFlowValueFactory
 import org.jetbrains.kotlin.resolve.calls.util.CallMaker
 import org.jetbrains.kotlin.resolve.calls.util.FakeCallableDescriptorForObject
 import org.jetbrains.kotlin.resolve.calls.util.createValueParametersForInvokeInFunctionType
@@ -54,6 +55,7 @@ import org.jetbrains.kotlin.types.TypeUtils.NO_EXPECTED_TYPE
 import org.jetbrains.kotlin.types.expressions.typeInfoFactory.createTypeInfo
 import org.jetbrains.kotlin.types.typeUtil.builtIns
 import org.jetbrains.kotlin.types.typeUtil.isSubtypeOf
+import org.jetbrains.kotlin.types.typeUtil.makeNotNullable
 import org.jetbrains.kotlin.types.typeUtil.makeNullable
 import org.jetbrains.kotlin.utils.addToStdlib.safeAs
 import java.lang.UnsupportedOperationException
@@ -107,16 +109,20 @@ class DoubleColonExpressionResolver(
         }
         else {
             val result = resolveDoubleColonLHS(expression, c)
-            val type = result?.type
-            if (type != null && !type.isError) {
-                checkClassLiteral(c, expression, result)
+            if (result != null && !result.type.isError) {
+                val inherentType = result.type
+                val dataFlowInfo = (result as? DoubleColonLHS.Expression)?.dataFlowInfo ?: c.dataFlowInfo
+                val dataFlowValue = DataFlowValueFactory.createDataFlowValue(expression.receiverExpression!!, inherentType, c)
+                val type =
+                        if (!dataFlowInfo.getStableNullability(dataFlowValue).canBeNull()) inherentType.makeNotNullable()
+                        else inherentType
+                checkClassLiteral(c, expression, type, result)
                 val variance =
                         if (result is DoubleColonLHS.Expression && !result.isObjectQualifier) Variance.OUT_VARIANCE else Variance.INVARIANT
                 val kClassType = reflectionTypes.getKClassType(Annotations.EMPTY, type, variance)
                 if (kClassType.isError) {
                     c.trace.report(MISSING_DEPENDENCY_CLASS.on(expression.receiverExpression!!, KotlinBuiltIns.FQ_NAMES.kClass.toSafe()))
                 }
-                val dataFlowInfo = (result as? DoubleColonLHS.Expression)?.dataFlowInfo ?: c.dataFlowInfo
                 return dataFlowAnalyzer.checkType(createTypeInfo(kClassType, dataFlowInfo), expression, c)
             }
         }
@@ -124,9 +130,12 @@ class DoubleColonExpressionResolver(
         return createTypeInfo(ErrorUtils.createErrorType("Unresolved class"), c)
     }
 
-    private fun checkClassLiteral(c: ExpressionTypingContext, expression: KtClassLiteralExpression, result: DoubleColonLHS) {
-        val type = result.type
-
+    private fun checkClassLiteral(
+            c: ExpressionTypingContext,
+            expression: KtClassLiteralExpression,
+            type: KotlinType,
+            result: DoubleColonLHS
+    ) {
         if (result is DoubleColonLHS.Expression) {
             if (!result.isObjectQualifier) {
                 if (!type.isSubtypeOf(type.builtIns.anyType)) {

compiler/testData/codegen/box/classLiteral/bound/smartCast.kt

@@ -0,0 +1,11 @@
+// KT-16291 Smart cast doesn't work when getting class of instance
+
+class Foo(val s: String) {
+    override fun equals(other: Any?): Boolean {
+        return other != null && other::class == this::class && s == (other as Foo).s
+    }
+}
+
+fun box(): String {
+    return if (Foo("a") == Foo("a")) "OK" else "Fail"
+}

compiler/testData/codegen/light-analysis/classLiteral/bound/smartCast.txt

@@ -0,0 +1,12 @@
+@kotlin.Metadata
+public final class Foo {
+    private final @org.jetbrains.annotations.NotNull field s: java.lang.String
+    public method <init>(@org.jetbrains.annotations.NotNull p0: java.lang.String): void
+    public method equals(@org.jetbrains.annotations.Nullable p0: java.lang.Object): boolean
+    public final @org.jetbrains.annotations.NotNull method getS(): java.lang.String
+}
+
+@kotlin.Metadata
+public final class SmartCastKt {
+    public final static @org.jetbrains.annotations.NotNull method box(): java.lang.String
+}

compiler/testData/diagnostics/tests/classLiteral/smartCast.kt

@@ -0,0 +1,23 @@
+// KT-16291 Smart cast doesn't work when getting class of instance
+
+import kotlin.reflect.KClass
+
+class Foo {
+    override fun equals(other: Any?): Boolean {
+        if (this === other) return true
+        if (other === null || other::class != this::class) return false
+
+        return true
+    }
+}
+
+fun test(f: Foo?): KClass<out Foo>? = if (f != null) f::class else null
+
+fun test2(): KClass<out Foo>? {
+    var f: Foo? = null
+    if (f != null) {
+        run { f = null }
+        return <!EXPRESSION_OF_NULLABLE_TYPE_IN_CLASS_LITERAL_LHS!>f<!>::class
+    }
+    return null
+}

compiler/testData/diagnostics/tests/classLiteral/smartCast.txt

@@ -0,0 +1,11 @@
+package
+
+public fun test(/*0*/ f: Foo?): kotlin.reflect.KClass<out Foo>?
+public fun test2(): kotlin.reflect.KClass<out Foo>?
+
+public final class Foo {
+    public constructor Foo()
+    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
+}

compiler/tests-ir-jvm/tests/org/jetbrains/kotlin/codegen/ir/IrBlackBoxCodegenTestGenerated.java

@@ -2613,6 +2613,12 @@ public class IrBlackBoxCodegenTestGenerated extends AbstractIrBlackBoxCodegenTes
                 String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/box/classLiteral/bound/simple.kt");
                 doTest(fileName);
             }
+
+            @TestMetadata("smartCast.kt")
+            public void testSmartCast() throws Exception {
+                String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/box/classLiteral/bound/smartCast.kt");
+                doTest(fileName);
+            }
         }
 
         @TestMetadata("compiler/testData/codegen/box/classLiteral/java")

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

@@ -3190,6 +3190,12 @@ public class DiagnosticsTestGenerated extends AbstractDiagnosticsTest {
                 doTest(fileName);
             }
 
+            @TestMetadata("smartCast.kt")
+            public void testSmartCast() throws Exception {
+                String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/classLiteral/smartCast.kt");
+                doTest(fileName);
+            }
+
             @TestMetadata("typealiases.kt")
             public void testTypealiases() throws Exception {
                 String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/classLiteral/typealiases.kt");

compiler/tests/org/jetbrains/kotlin/codegen/BlackBoxCodegenTestGenerated.java

@@ -2613,6 +2613,12 @@ public class BlackBoxCodegenTestGenerated extends AbstractBlackBoxCodegenTest {
                 String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/box/classLiteral/bound/simple.kt");
                 doTest(fileName);
             }
+
+            @TestMetadata("smartCast.kt")
+            public void testSmartCast() throws Exception {
+                String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/box/classLiteral/bound/smartCast.kt");
+                doTest(fileName);
+            }
         }
 
         @TestMetadata("compiler/testData/codegen/box/classLiteral/java")

js/js.tests/test/org/jetbrains/kotlin/js/test/semantics/JsCodegenBoxTestGenerated.java

@@ -3190,6 +3190,12 @@ public class JsCodegenBoxTestGenerated extends AbstractJsCodegenBoxTest {
                 }
                 throw new AssertionError("Looks like this test can be unmuted. Remove IGNORE_BACKEND directive for that.");
             }
+
+            @TestMetadata("smartCast.kt")
+            public void testSmartCast() throws Exception {
+                String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/box/classLiteral/bound/smartCast.kt");
+                doTest(fileName);
+            }
         }
 
         @TestMetadata("compiler/testData/codegen/box/classLiteral/java")