Lower fun interface children's body during inline class lowering

#KT-51121 Fixed

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

@@ -122,10 +122,14 @@ private class JvmInlineClassLowering(private val context: JvmBackendContext) : F
             return null
         }
 
-        // If fun interface methods are already mangled, do not mangle them twice.
-        if (function is IrSimpleFunction && function.overriddenSymbols.any { it.owner.parentAsClass.isFun } &&
-            function.name.asString().substringAfterLast('-') == replacement.name.asString().substringAfterLast('-')
-        ) return null
+        if (function is IrSimpleFunction && function.overriddenSymbols.any { it.owner.parentAsClass.isFun }) {
+            // If fun interface methods are already mangled, do not mangle them twice.
+            val suffix = function.hashSuffix()
+            if (suffix != null && function.name.asString().endsWith(suffix)) {
+                function.transformChildrenVoid()
+                return null
+            }
+        }
 
         addBindingsFor(function, replacement)
         return when (function) {
@@ -135,6 +139,13 @@ private class JvmInlineClassLowering(private val context: JvmBackendContext) : F
         }
     }
 
+    private fun IrFunction.hashSuffix(): String? =
+        InlineClassAbi.hashSuffix(
+            this,
+            context.state.functionsWithInlineClassReturnTypesMangled,
+            context.state.useOldManglingSchemeForFunctionsWithInlineClassesInSignatures
+        )
+
     private fun transformSimpleFunctionFlat(function: IrSimpleFunction, replacement: IrSimpleFunction): List<IrDeclaration> {
         replacement.valueParameters.forEach {
             it.transformChildrenVoid()
@@ -460,6 +471,10 @@ private class JvmInlineClassLowering(private val context: JvmBackendContext) : F
 
     override fun visitReturn(expression: IrReturn): IrExpression {
         expression.returnTargetSymbol.owner.safeAs<IrFunction>()?.let { target ->
+            val suffix = target.hashSuffix()
+            if (suffix != null && target.name.asString().endsWith(suffix))
+                return super.visitReturn(expression)
+
             context.inlineClassReplacements.getReplacementFunction(target)?.let {
                 return context.createIrBuilder(it.symbol, expression.startOffset, expression.endOffset).irReturn(
                     expression.value.transform(this, null)

compiler/ir/backend.jvm/src/org/jetbrains/kotlin/backend/jvm/InlineClassAbi.kt

@@ -66,12 +66,7 @@ object InlineClassAbi {
             return Name.identifier("constructor-impl")
         }
 
-        val suffix = hashSuffix(
-            useOldMangleRules,
-            irFunction.fullValueParameterList.map { it.type },
-            irFunction.returnType.takeIf { mangleReturnTypes && irFunction.hasMangledReturnType },
-            irFunction.isSuspend
-        )
+        val suffix = hashSuffix(irFunction, mangleReturnTypes, useOldMangleRules)
         if (suffix == null && ((irFunction.parent as? IrClass)?.isSingleFieldValueClass != true || irFunction.origin == IrDeclarationOrigin.IR_BUILTINS_STUB)) {
             return irFunction.name
         }
@@ -90,6 +85,14 @@ object InlineClassAbi {
         return Name.identifier("$base-${suffix ?: "impl"}")
     }
 
+    fun hashSuffix(irFunction: IrFunction, mangleReturnTypes: Boolean, useOldMangleRules: Boolean): String? =
+        hashSuffix(
+            useOldMangleRules,
+            irFunction.fullValueParameterList.map { it.type },
+            irFunction.returnType.takeIf { mangleReturnTypes && irFunction.hasMangledReturnType },
+            irFunction.isSuspend
+        )
+
     fun hashSuffix(
         useOldMangleRules: Boolean,
         valueParameters: List<IrType>,