Mocking doesn't work for a functional interface returning a value class

[uwared]

Prerequisites

Please answer the following questions for yourself before submitting an issue.

• I am running the latest version
• I checked the documentation and found no answer
• I checked to make sure that this issue has not already been filed

Expected Behavior

The test below, which mocks a functional interface returning a value class, passes:

Minimal reproducible code

package com.example

import io.kotest.matchers.shouldBe
import io.mockk.every
import io.mockk.impl.annotations.InjectMockKs
import io.mockk.impl.annotations.MockK
import io.mockk.junit5.MockKExtension
import org.junit.jupiter.api.Test
import org.junit.jupiter.api.extension.ExtendWith
import org.springframework.stereotype.Component

@JvmInline
value class ValueClass(val value: Int)

interface ValueClassInterface : () -> ValueClass

@Component
class ExampleComponent(
    private val valueClassInterface: ValueClassInterface,
) {
    fun testFunction(): ValueClass {
        return valueClassInterface()
    }
}

@ExtendWith(MockKExtension::class)
class ValueClassTest {

    @MockK
    lateinit var valueClassInterface: ValueClassInterface

    @InjectMockKs
    lateinit var exampleComponent: ExampleComponent

    @Test
    fun test() {
        every { valueClassInterface() } returns ValueClass(1)
        exampleComponent.testFunction() shouldBe ValueClass(1)
    }
}

Current Behavior

The test is failing with an exception:

Stacktrace

Unknown origin of public abstract operator fun invoke(): R defined in kotlin.Function0[FunctionInvokeDescriptor@17ba57f0] (class kotlin.reflect.jvm.internal.impl.builtins.functions.FunctionInvokeDescriptor)
kotlin.reflect.jvm.internal.KotlinReflectionInternalError: Unknown origin of public abstract operator fun invoke(): R defined in kotlin.Function0[FunctionInvokeDescriptor@17ba57f0] (class kotlin.reflect.jvm.internal.impl.builtins.functions.FunctionInvokeDescriptor)
	at kotlin.reflect.jvm.internal.RuntimeTypeMapper.mapSignature(RuntimeTypeMapper.kt:226)
	at kotlin.reflect.jvm.internal.KFunctionImpl.<init>(KFunctionImpl.kt:52)
	at kotlin.reflect.jvm.internal.CreateKCallableVisitor.visitFunctionDescriptor(util.kt:314)
	at kotlin.reflect.jvm.internal.CreateKCallableVisitor.visitFunctionDescriptor(util.kt:291)
	at kotlin.reflect.jvm.internal.impl.descriptors.impl.FunctionDescriptorImpl.accept(FunctionDescriptorImpl.java:826)
	at kotlin.reflect.jvm.internal.KDeclarationContainerImpl.getMembers(KDeclarationContainerImpl.kt:62)
	at kotlin.reflect.jvm.internal.KClassImpl$Data$declaredNonStaticMembers$2.invoke(KClassImpl.kt:173)
	at kotlin.reflect.jvm.internal.KClassImpl$Data$declaredNonStaticMembers$2.invoke(KClassImpl.kt:173)
	at kotlin.reflect.jvm.internal.ReflectProperties$LazySoftVal.invoke(ReflectProperties.java:70)
	at kotlin.reflect.jvm.internal.ReflectProperties$Val.getValue(ReflectProperties.java:32)
	at kotlin.reflect.jvm.internal.KClassImpl$Data.getDeclaredNonStaticMembers(KClassImpl.kt:173)
	at kotlin.reflect.jvm.internal.KClassImpl$Data$allNonStaticMembers$2.invoke(KClassImpl.kt:182)
	at kotlin.reflect.jvm.internal.KClassImpl$Data$allNonStaticMembers$2.invoke(KClassImpl.kt:182)
	at kotlin.reflect.jvm.internal.ReflectProperties$LazySoftVal.invoke(ReflectProperties.java:70)
	at kotlin.reflect.jvm.internal.ReflectProperties$Val.getValue(ReflectProperties.java:32)
	at kotlin.reflect.jvm.internal.KClassImpl$Data.getAllNonStaticMembers(KClassImpl.kt:182)
	at kotlin.reflect.jvm.internal.KClassImpl$Data$allMembers$2.invoke(KClassImpl.kt:188)
	at kotlin.reflect.jvm.internal.KClassImpl$Data$allMembers$2.invoke(KClassImpl.kt:188)
	at kotlin.reflect.jvm.internal.ReflectProperties$LazySoftVal.invoke(ReflectProperties.java:70)
	at kotlin.reflect.jvm.internal.ReflectProperties$Val.getValue(ReflectProperties.java:32)
	at kotlin.reflect.jvm.internal.KClassImpl$Data.getAllMembers(KClassImpl.kt:188)
	at kotlin.reflect.jvm.internal.KClassImpl.getMembers(KClassImpl.kt:206)
	at kotlin.reflect.full.KClasses.getFunctions(KClasses.kt:89)
	at kotlin.reflect.jvm.ReflectJvmMapping.getKotlinFunction(ReflectJvmMapping.kt:144)
	at io.mockk.core.ValueClassSupport.maybeUnboxValueForMethodReturn(ValueClassSupport.kt:26)
	at io.mockk.proxy.jvm.advice.Interceptor.call(Interceptor.kt:22)
	at io.mockk.proxy.jvm.advice.BaseAdvice.handle(BaseAdvice.kt:42)
	at io.mockk.proxy.jvm.advice.jvm.JvmMockKProxyInterceptor.interceptNoSuper(JvmMockKProxyInterceptor.java:44)
	at com.example.ValueClassInterface$Subclass0.invoke(Unknown Source)
	at com.example.ValueClassInterface$Subclass0.invoke(Unknown Source)
	at com.example.ValueClassTest$test$1.invoke-oVKG3qc(ValueClassTest.kt:37)
	at com.example.ValueClassTest$test$1.invoke(ValueClassTest.kt:37)
	at io.mockk.impl.eval.RecordedBlockEvaluator$record$block$1.invoke(RecordedBlockEvaluator.kt:24)
	at io.mockk.impl.eval.RecordedBlockEvaluator$enhanceWithRethrow$1.invoke(RecordedBlockEvaluator.kt:76)
	at io.mockk.impl.recording.JvmAutoHinter.autoHint(JvmAutoHinter.kt:23)
	at io.mockk.impl.eval.RecordedBlockEvaluator.record(RecordedBlockEvaluator.kt:39)
	at io.mockk.impl.eval.EveryBlockEvaluator.every(EveryBlockEvaluator.kt:30)
	at io.mockk.MockKDsl.internalEvery(API.kt:94)
	at io.mockk.MockKKt.every(MockK.kt:143)
        at com.example.ValueClassTest.test(ValueClassTest.kt:37)

Context

• MockK version: 1.3.10
• OS: macOS Sonoma 14.4.1
• Kotlin version: 1.9.23
• JDK version: OpenJDK 21.0.2
• JUnit version: 5.10.2
• Type of test: unit test