K2: fix enhancement building for Java methods with type parameters

Before this commit, we copied each type parameter during method
enhancement, while not copying the symbol. This led to symbol clashes
in MPP scenarios and various other problems.

Now we create a fully-functional type parameter copy in enhancement
and perform a substitution of old type parameters with new ones
in receiver type, value parameter types, return type,
and type parameter upper bounds.

#KT-59766 Fixed
#KT-59738 Fixed

compiler/fir/fir2ir/tests-gen/org/jetbrains/kotlin/test/runners/codegen/FirLightTreeBlackBoxCodegenTestGenerated.java

@@ -33460,6 +33460,12 @@ public class FirLightTreeBlackBoxCodegenTestGenerated extends AbstractFirLightTr
                 runTest("compiler/testData/codegen/box/multiplatform/k2/anonymousObjectAndSpecificImplementationInDeserializedIr.kt");
             }
 
+            @Test
+            @TestMetadata("javaMethodWithTypeParameter.kt")
+            public void testJavaMethodWithTypeParameter() throws Exception {
+                runTest("compiler/testData/codegen/box/multiplatform/k2/javaMethodWithTypeParameter.kt");
+            }
+
             @Nested
             @TestMetadata("compiler/testData/codegen/box/multiplatform/k2/annotations")
             @TestDataPath("$PROJECT_ROOT")

compiler/fir/fir2ir/tests-gen/org/jetbrains/kotlin/test/runners/codegen/FirPsiBlackBoxCodegenTestGenerated.java

@@ -33460,6 +33460,12 @@ public class FirPsiBlackBoxCodegenTestGenerated extends AbstractFirPsiBlackBoxCo
                 runTest("compiler/testData/codegen/box/multiplatform/k2/anonymousObjectAndSpecificImplementationInDeserializedIr.kt");
             }
 
+            @Test
+            @TestMetadata("javaMethodWithTypeParameter.kt")
+            public void testJavaMethodWithTypeParameter() throws Exception {
+                runTest("compiler/testData/codegen/box/multiplatform/k2/javaMethodWithTypeParameter.kt");
+            }
+
             @Nested
             @TestMetadata("compiler/testData/codegen/box/multiplatform/k2/annotations")
             @TestDataPath("$PROJECT_ROOT")

compiler/fir/java/src/org/jetbrains/kotlin/fir/java/enhancement/SignatureEnhancement.kt

@@ -31,6 +31,7 @@ import org.jetbrains.kotlin.fir.java.resolveIfJavaType
 import org.jetbrains.kotlin.fir.java.symbols.FirJavaOverriddenSyntheticPropertySymbol
 import org.jetbrains.kotlin.fir.java.toConeKotlinTypeProbablyFlexible
 import org.jetbrains.kotlin.fir.resolve.providers.symbolProvider
+import org.jetbrains.kotlin.fir.resolve.substitution.ConeSubstitutorByMap
 import org.jetbrains.kotlin.fir.scopes.jvm.computeJvmDescriptor
 import org.jetbrains.kotlin.fir.symbols.ConeClassLikeLookupTag
 import org.jetbrains.kotlin.fir.symbols.ConeTypeParameterLookupTag
@@ -251,6 +252,9 @@ class FirSignatureEnhancement(
         val functionSymbol: FirFunctionSymbol<*>
         var isJavaRecordComponent = false
 
+        val typeParameterSubstitutionMap = mutableMapOf<FirTypeParameterSymbol, ConeKotlinType>()
+        var typeParameterSubstitutor: ConeSubstitutorByMap? = null
+
         val function = when (firMethod) {
             is FirJavaConstructor -> {
                 val symbol = FirConstructorSymbol(methodId).also { functionSymbol = it }
@@ -288,6 +292,7 @@ class FirSignatureEnhancement(
                     moduleData = this@FirSignatureEnhancement.moduleData
                     resolvePhase = FirResolvePhase.ANALYZED_DEPENDENCIES
                     origin = FirDeclarationOrigin.Enhancement
+                    // TODO: we should set a new origin / containing declaration to type parameters (KT-60440)
                     this.typeParameters += (enhancedTypeParameters ?: firMethod.typeParameters)
                 }
             }
@@ -297,14 +302,6 @@ class FirSignatureEnhancement(
                     source = firMethod.source
                     moduleData = this@FirSignatureEnhancement.moduleData
                     origin = FirDeclarationOrigin.Enhancement
-                    returnTypeRef = newReturnTypeRef
-                    receiverParameter = newReceiverTypeRef?.let { receiverType ->
-                        buildReceiverParameter {
-                            typeRef = receiverType
-                            annotations += firMethod.valueParameters.first().annotations
-                            source = receiverType.source?.fakeElement(KtFakeSourceElementKind.ReceiverFromType)
-                        }
-                    }
 
                     this.name = name!!
                     status = firMethod.status
@@ -316,10 +313,39 @@ class FirSignatureEnhancement(
                             "Unexpected type parameter type: ${typeParameter::class.simpleName}"
                         }
 
-                        buildTypeParameterCopy(typeParameter) {
+                        // TODO: we probably shouldn't build a copy second time. See performFirstRoundOfBoundsResolution (KT-60446)
+                        val newTypeParameter = buildTypeParameterCopy(typeParameter) {
                             origin = FirDeclarationOrigin.Enhancement
+                            symbol = FirTypeParameterSymbol()
                             containingDeclarationSymbol = functionSymbol
                         }
+                        typeParameterSubstitutionMap[typeParameter.symbol] = ConeTypeParameterTypeImpl(
+                            newTypeParameter.symbol.toLookupTag(), isNullable = false
+                        )
+                        newTypeParameter
+                    }
+                    if (typeParameterSubstitutionMap.isNotEmpty()) {
+                        typeParameterSubstitutor = ConeSubstitutorByMap(typeParameterSubstitutionMap, session)
+                    }
+                    returnTypeRef = newReturnTypeRef.withReplacedConeType(
+                        typeParameterSubstitutor?.substituteOrNull(newReturnTypeRef.coneType)
+                    )
+                    val substitutedReceiverTypeRef = newReceiverTypeRef?.withReplacedConeType(
+                        typeParameterSubstitutor?.substituteOrNull(newReturnTypeRef.coneType)
+                    )
+                    receiverParameter = substitutedReceiverTypeRef?.let { receiverType ->
+                        buildReceiverParameter {
+                            typeRef = receiverType
+                            annotations += firMethod.valueParameters.first().annotations
+                            source = receiverType.source?.fakeElement(KtFakeSourceElementKind.ReceiverFromType)
+                        }
+                    }
+                    typeParameters.forEach { typeParameter ->
+                        typeParameter.replaceBounds(
+                            typeParameter.bounds.map { boundTypeRef ->
+                                boundTypeRef.withReplacedConeType(typeParameterSubstitutor?.substituteOrNull(boundTypeRef.coneType))
+                            }
+                        )
                     }
 
                     dispatchReceiverType = firMethod.dispatchReceiverType
@@ -336,7 +362,9 @@ class FirSignatureEnhancement(
                     containingFunctionSymbol = functionSymbol
                     moduleData = this@FirSignatureEnhancement.moduleData
                     origin = FirDeclarationOrigin.Enhancement
-                    returnTypeRef = enhancedReturnType
+                    returnTypeRef = enhancedReturnType.withReplacedConeType(
+                        typeParameterSubstitutor?.substituteOrNull(enhancedReturnType.coneType)
+                    )
                     this.name = valueParameter.name
                     symbol = FirValueParameterSymbol(this.name)
                     defaultValue = valueParameter.defaultValue
@@ -388,6 +416,7 @@ class FirSignatureEnhancement(
             typeParametersCopy += if (typeParameter is FirTypeParameter) {
                 initialBounds.add(typeParameter.bounds.toList())
                 buildTypeParameterCopy(typeParameter) {
+                    // TODO: we should create a new symbol to avoid clashing (KT-60445)
                     bounds.clear()
                     typeParameter.bounds.mapTo(bounds) {
                         it.resolveIfJavaType(session, javaTypeParameterStack, FirJavaTypeConversionMode.TYPE_PARAMETER_BOUND_FIRST_ROUND)

compiler/testData/codegen/box/multiplatform/k2/javaMethodWithTypeParameter.kt

@@ -0,0 +1,42 @@
+// LANGUAGE: +MultiPlatformProjects
+// ISSUE: KT-59766
+// WITH_STDLIB
+// TARGET_BACKEND: JVM_IR
+// FULL_JDK
+
+// MODULE: lib-jvm
+// FILE: lib.kt
+
+import java.util.concurrent.*
+
+fun <T> CompletionStage<T>.foo() {
+    handle { value, exception ->
+
+    }
+}
+
+// MODULE: jvm()()(lib-jvm)
+// FILE: jvm.kt
+
+package kotlinx.coroutines.future
+
+import java.util.concurrent.*
+import java.util.function.*
+
+fun <T> CompletionStage<T>.asDeferred() {
+    handle { value, exception ->
+
+    }
+}
+
+class ContinuationHandler<T> : BiFunction<T?, Throwable?, Unit> {
+    override fun apply(result: T?, exception: Throwable?) {
+
+    }
+}
+
+fun box(): String {
+    val handler = ContinuationHandler<String>()
+    CompletableFuture<String>().asDeferred()
+    return "OK"
+}

compiler/tests-common-new/tests-gen/org/jetbrains/kotlin/test/runners/codegen/IrBlackBoxCodegenTestGenerated.java

@@ -33460,6 +33460,12 @@ public class IrBlackBoxCodegenTestGenerated extends AbstractIrBlackBoxCodegenTes
                 runTest("compiler/testData/codegen/box/multiplatform/k2/anonymousObjectAndSpecificImplementationInDeserializedIr.kt");
             }
 
+            @Test
+            @TestMetadata("javaMethodWithTypeParameter.kt")
+            public void testJavaMethodWithTypeParameter() throws Exception {
+                runTest("compiler/testData/codegen/box/multiplatform/k2/javaMethodWithTypeParameter.kt");
+            }
+
             @Nested
             @TestMetadata("compiler/testData/codegen/box/multiplatform/k2/annotations")
             @TestDataPath("$PROJECT_ROOT")

compiler/tests-common-new/tests-gen/org/jetbrains/kotlin/test/runners/codegen/IrBlackBoxCodegenWithIrInlinerTestGenerated.java

@@ -33460,6 +33460,12 @@ public class IrBlackBoxCodegenWithIrInlinerTestGenerated extends AbstractIrBlack
                 runTest("compiler/testData/codegen/box/multiplatform/k2/anonymousObjectAndSpecificImplementationInDeserializedIr.kt");
             }
 
+            @Test
+            @TestMetadata("javaMethodWithTypeParameter.kt")
+            public void testJavaMethodWithTypeParameter() throws Exception {
+                runTest("compiler/testData/codegen/box/multiplatform/k2/javaMethodWithTypeParameter.kt");
+            }
+
             @Nested
             @TestMetadata("compiler/testData/codegen/box/multiplatform/k2/annotations")
             @TestDataPath("$PROJECT_ROOT")

compiler/tests-gen/org/jetbrains/kotlin/codegen/LightAnalysisModeTestGenerated.java

@@ -28487,6 +28487,11 @@ public class LightAnalysisModeTestGenerated extends AbstractLightAnalysisModeTes
                 runTest("compiler/testData/codegen/box/multiplatform/k2/anonymousObjectAndSpecificImplementationInDeserializedIr.kt");
             }
 
+            @TestMetadata("javaMethodWithTypeParameter.kt")
+            public void testJavaMethodWithTypeParameter() throws Exception {
+                runTest("compiler/testData/codegen/box/multiplatform/k2/javaMethodWithTypeParameter.kt");
+            }
+
             @TestMetadata("compiler/testData/codegen/box/multiplatform/k2/annotations")
             @TestDataPath("$PROJECT_ROOT")
             @RunWith(JUnit3RunnerWithInners.class)