JVM IR: Box inline classes in covariant overrides (KT-30419)

compiler/ir/backend.jvm/src/org/jetbrains/kotlin/backend/jvm/codegen/MethodSignatureMapper.kt

@@ -182,19 +182,17 @@ class MethodSignatureMapper(private val context: JvmBackendContext) {
     private fun forceBoxedReturnType(function: IrFunction): Boolean {
         if (isBoxMethodForInlineClass(function)) return true
 
-        return isJvmPrimitive(function.returnType) &&
-                function is IrSimpleFunction && function.allOverridden().any { !isJvmPrimitive(it.returnType) }
+        return isJvmPrimitiveOrInlineClass(function.returnType) &&
+                function is IrSimpleFunction && function.allOverridden().any { !isJvmPrimitiveOrInlineClass(it.returnType) }
     }
 
     private fun isBoxMethodForInlineClass(function: IrFunction): Boolean =
         function.parent.let { it is IrClass && it.isInline } &&
                 function.origin == JvmLoweredDeclarationOrigin.SYNTHETIC_INLINE_CLASS_MEMBER &&
                 function.name.asString() == "box-impl"
 
-    private fun isJvmPrimitive(type: IrType): Boolean {
-        if (type.isPrimitiveType()) return true
-        return type.getClass()?.isInline == true && AsmUtil.isPrimitive(typeMapper.mapType(type))
-    }
+    private fun isJvmPrimitiveOrInlineClass(type: IrType): Boolean =
+        type.isPrimitiveType() || type.getClass()?.isInline == true
 
     fun mapSignatureSkipGeneric(function: IrFunction): JvmMethodSignature =
         mapSignature(function, true)

compiler/ir/backend.jvm/src/org/jetbrains/kotlin/backend/jvm/lower/BridgeLowering.kt

@@ -15,7 +15,9 @@ import org.jetbrains.kotlin.backend.jvm.JvmBackendContext
 import org.jetbrains.kotlin.backend.jvm.JvmLoweredDeclarationOrigin
 import org.jetbrains.kotlin.backend.jvm.codegen.isJvmInterface
 import org.jetbrains.kotlin.backend.jvm.ir.eraseTypeParameters
+import org.jetbrains.kotlin.backend.jvm.ir.erasedUpperBound
 import org.jetbrains.kotlin.backend.jvm.ir.isJvmAbstract
+import org.jetbrains.kotlin.backend.jvm.lower.inlineclasses.unboxInlineClass
 import org.jetbrains.kotlin.codegen.AsmUtil
 import org.jetbrains.kotlin.descriptors.Modality
 import org.jetbrains.kotlin.descriptors.Visibilities
@@ -31,6 +33,7 @@ import org.jetbrains.kotlin.ir.util.*
 import org.jetbrains.kotlin.ir.visitors.IrElementTransformerVoid
 import org.jetbrains.kotlin.name.Name
 import org.jetbrains.kotlin.util.OperatorNameConventions
+import org.jetbrains.kotlin.utils.addToStdlib.safeAs
 import org.jetbrains.kotlin.utils.getOrPutNullable
 import org.jetbrains.org.objectweb.asm.Type
 import org.jetbrains.org.objectweb.asm.commons.Method
@@ -172,8 +175,10 @@ private class BridgeLowering(val context: JvmBackendContext) : FileLoweringPass,
             createBridges(declaration, member)
 
             // For lambda classes, we move overrides from the `invoke` function to its bridge. This will allow us to avoid boxing
-            // the return type of `invoke` in codegen for lambdas with primitive return type.
-            if (member.name == OperatorNameConventions.INVOKE && declaration.origin == JvmLoweredDeclarationOrigin.LAMBDA_IMPL) {
+            // the return type of `invoke` in codegen for lambdas with primitive return type. This does not apply to lambdas returning
+            // inline class types erasing to Any, which we need to box.
+            if (member.name == OperatorNameConventions.INVOKE && declaration.origin == JvmLoweredDeclarationOrigin.LAMBDA_IMPL
+                && !member.returnType.isInlineClassErasingToAny) {
                 member.overriddenSymbols = listOf()
             }
         }
@@ -354,10 +359,15 @@ private class BridgeLowering(val context: JvmBackendContext) : FileLoweringPass,
             copyParametersWithErasure(this@addBridge, bridge.overridden)
             body = context.createIrBuilder(symbol).run { irExprBody(delegatingCall(this@apply, target)) }
 
-            val redundantOverrides = bridge.overriddenSymbols.flatMapTo(mutableSetOf()) {
+            // The generated bridge method overrides all of the symbols which were overridden by its overrides.
+            // This is technically wrong, but it's necessary to generate a method which maps to the same signature.
+            val inheritedOverrides = bridge.overriddenSymbols.flatMapTo(mutableSetOf()) { function ->
+                function.owner.safeAs<IrSimpleFunction>()?.overriddenSymbols ?: emptyList()
+            }
+            val redundantOverrides = inheritedOverrides.flatMapTo(mutableSetOf()) {
                 it.owner.allOverridden().map { override -> override.symbol }.asIterable()
             }
-            overriddenSymbols = bridge.overriddenSymbols.filter { it !in redundantOverrides }
+            overriddenSymbols = inheritedOverrides.filter { it !in redundantOverrides }
         }
 
     private fun IrClass.addSpecialBridge(specialBridge: SpecialBridge, target: IrSimpleFunction): IrSimpleFunction =
@@ -492,3 +502,6 @@ private fun IrSimpleFunction.resolvesToClass(): Boolean {
 
 private fun IrSimpleFunction.overriddenFromClass(): IrSimpleFunction? =
     overriddenSymbols.singleOrNull { !it.owner.parentAsClass.isJvmInterface }?.owner
+
+private val IrType.isInlineClassErasingToAny: Boolean
+    get() = unboxInlineClass().let { unboxed -> unboxed != this && (unboxed.isAny() || unboxed.isNullableAny()) }

compiler/testData/codegen/box/inlineClasses/boxReturnValueInLambda/boxAny.kt

@@ -1,5 +1,4 @@
 // IGNORE_BACKEND_FIR: JVM_IR
-// IGNORE_BACKEND: JVM_IR
 
 inline class X(val x: Any)
 

compiler/testData/codegen/box/inlineClasses/boxReturnValueInLambda/boxFunLiteralAny.kt

@@ -1,5 +1,4 @@
 // IGNORE_BACKEND_FIR: JVM_IR
-// IGNORE_BACKEND: JVM_IR
 
 inline class X(val x: Any)
 

compiler/testData/codegen/box/inlineClasses/boxReturnValueInLambda/boxNullableAny.kt

@@ -1,5 +1,4 @@
 // IGNORE_BACKEND_FIR: JVM_IR
-// IGNORE_BACKEND: JVM_IR
 
 inline class X(val x: Any?)
 

compiler/testData/codegen/box/inlineClasses/boxReturnValueInLambda/boxNullableAnyNull.kt

@@ -1,5 +1,4 @@
 // IGNORE_BACKEND_FIR: JVM_IR
-// IGNORE_BACKEND: JVM_IR
 
 inline class X(val x: Any?)
 

compiler/testData/codegen/box/inlineClasses/boxReturnValueInLambda/kt27586_1.kt

@@ -1,6 +1,5 @@
 // WITH_RUNTIME
 // IGNORE_BACKEND_FIR: JVM_IR
-// IGNORE_BACKEND: JVM_IR
 
 fun f1(): () -> Result<String> {
     return {

compiler/testData/codegen/box/inlineClasses/boxReturnValueInLambda/kt27586_2.kt

@@ -1,6 +1,5 @@
 // WITH_RUNTIME
 // IGNORE_BACKEND_FIR: JVM_IR
-// IGNORE_BACKEND: JVM_IR
 
 fun f1() = lazy {
     runCatching {

compiler/testData/codegen/box/inlineClasses/boxReturnValueOnOverride/covariantOverrideChainErasedToAny.kt

@@ -1,5 +1,4 @@
 // IGNORE_BACKEND_FIR: JVM_IR
-// IGNORE_BACKEND: JVM_IR
 
 inline class X(val x: Any)
 

compiler/testData/codegen/box/inlineClasses/boxReturnValueOnOverride/covariantOverrideChainErasedToNullableAny.kt

@@ -1,5 +1,4 @@
 // IGNORE_BACKEND_FIR: JVM_IR
-// IGNORE_BACKEND: JVM_IR
 
 inline class X(val x: Any?)
 

compiler/testData/codegen/box/inlineClasses/boxReturnValueOnOverride/covariantOverrideErasedToAny.kt

@@ -1,5 +1,4 @@
 // IGNORE_BACKEND_FIR: JVM_IR
-// IGNORE_BACKEND: JVM_IR
 
 inline class X(val x: Any)
 

compiler/testData/codegen/box/inlineClasses/boxReturnValueOnOverride/covariantOverrideErasedToInterface.kt

@@ -1,5 +1,4 @@
 // IGNORE_BACKEND_FIR: JVM_IR
-// IGNORE_BACKEND: JVM_IR
 
 interface IFoo {
     fun foo(): String

compiler/testData/codegen/box/inlineClasses/boxReturnValueOnOverride/covariantOverrideListVsMutableList.kt

@@ -1,7 +1,6 @@
 // IGNORE_BACKEND_FIR: JVM_IR
 // WITH_RUNTIME
 // KJS_WITH_FULL_RUNTIME
-// IGNORE_BACKEND: JVM_IR
 
 interface IFooList {
     fun foo(): List<String>

compiler/testData/codegen/box/inlineClasses/boxReturnValueOnOverride/genericOverride.kt

@@ -1,5 +1,4 @@
 // IGNORE_BACKEND_FIR: JVM_IR
-// IGNORE_BACKEND: JVM_IR
 
 inline class X(val x: Any)
 

compiler/testData/codegen/box/inlineClasses/boxReturnValueOnOverride/kt28483.kt

@@ -1,5 +1,4 @@
 // IGNORE_BACKEND_FIR: JVM_IR
-// IGNORE_BACKEND: JVM_IR
 
 inline class ResultOrClosed(val x: Any?)
 

compiler/testData/codegen/box/inlineClasses/boxReturnValueOnOverride/relatedReturnTypes1a.kt

@@ -1,5 +1,4 @@
 // IGNORE_BACKEND_FIR: JVM_IR
-// IGNORE_BACKEND: JVM_IR
 
 interface IQ {
     fun ok(): String

compiler/testData/codegen/box/inlineClasses/boxReturnValueOnOverride/relatedReturnTypes1b.kt

@@ -1,5 +1,4 @@
 // IGNORE_BACKEND_FIR: JVM_IR
-// IGNORE_BACKEND: JVM_IR
 
 interface IQ {
     fun ok(): String

compiler/testData/codegen/box/inlineClasses/callableReferences/kt37986.kt

@@ -1,6 +1,3 @@
-// IGNORE_BACKEND: JVM_IR
-// IGNORE_BACKEND_FIR: JVM_IR
-
 inline class R(val x: Any)
 
 fun useR(r: R) {