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Mockito spying on kotlin class error

See original GitHub issue

Hello. I am getting error with a version of Mockito exactly from 2.6.7 (in 2.7.19 reproduced) (in 2.6.6 not reproduced) With a version of Mockito 2.2.9 my code is working. Seems something wrong with parsing while mocking, see a stacktrace:

org.mockito.exceptions.base.MockitoException: 
Mockito cannot mock this class: class com.example.myapplication.Samples.`
Mockito can only mock non-private & non-final classes.
If you're not sure why you're getting this error, please report to the mailing list.
Java               : 1.8
JVM vendor name    : JetBrains s.r.o
JVM vendor version : 25.112-b06
JVM name           : OpenJDK 64-Bit Server VM
JVM version        : 1.8.0_112-release-b06
JVM info           : mixed mode
OS name            : Mac OS X
OS version         : 10.12.3
Underlying exception : java.lang.IllegalArgumentException: Could not create type

	at com.example.mayudin.myapplication.ExampleUnitTest.addition_isCorrect(ExampleUnitTest.kt:22)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
	at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
	at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
	at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
	at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57)
	at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
	at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
	at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
	at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
	at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
	at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
	at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
	at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:117)
	at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:42)
	at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:262)
	at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:84)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at com.intellij.rt.execution.application.AppMain.main(AppMain.java:147)
Caused by: java.lang.IllegalArgumentException: Could not create type
	at net.bytebuddy.TypeCache.findOrInsert(TypeCache.java:140)
	at net.bytebuddy.TypeCache$WithInlineExpunction.findOrInsert(TypeCache.java:346)
	at net.bytebuddy.TypeCache.findOrInsert(TypeCache.java:161)
	at net.bytebuddy.TypeCache$WithInlineExpunction.findOrInsert(TypeCache.java:355)
	at org.mockito.internal.creation.bytebuddy.TypeCachingBytecodeGenerator.mockClass(TypeCachingBytecodeGenerator.java:32)
	at org.mockito.internal.creation.bytebuddy.SubclassByteBuddyMockMaker.createMockType(SubclassByteBuddyMockMaker.java:71)
	at org.mockito.internal.creation.bytebuddy.SubclassByteBuddyMockMaker.createMock(SubclassByteBuddyMockMaker.java:42)
	at org.mockito.internal.creation.bytebuddy.ByteBuddyMockMaker.createMock(ByteBuddyMockMaker.java:26)
	at org.mockito.internal.util.MockUtil.createMock(MockUtil.java:35)
	at org.mockito.internal.MockitoCore.mock(MockitoCore.java:65)
	at org.mockito.Mockito.spy(Mockito.java:1812)
	... 28 more
Caused by: java.lang.reflect.GenericSignatureFormatError: Signature Parse error: expected '<' or ';' but got .
	Remaining input: .SampleDelegate<TT;>;
	at sun.reflect.generics.parser.SignatureParser.error(SignatureParser.java:124)
	at sun.reflect.generics.parser.SignatureParser.parsePackageNameAndSimpleClassTypeSignature(SignatureParser.java:348)
	at sun.reflect.generics.parser.SignatureParser.parseClassTypeSignature(SignatureParser.java:310)
	at sun.reflect.generics.parser.SignatureParser.parseFieldTypeSignature(SignatureParser.java:289)
	at sun.reflect.generics.parser.SignatureParser.parseFieldTypeSignature(SignatureParser.java:283)
	at sun.reflect.generics.parser.SignatureParser.parseTypeSignature(SignatureParser.java:485)
	at sun.reflect.generics.parser.SignatureParser.parseReturnType(SignatureParser.java:627)
	at sun.reflect.generics.parser.SignatureParser.parseMethodTypeSignature(SignatureParser.java:577)
	at sun.reflect.generics.parser.SignatureParser.parseMethodSig(SignatureParser.java:171)
	at sun.reflect.generics.repository.ConstructorRepository.parse(ConstructorRepository.java:55)
	at sun.reflect.generics.repository.ConstructorRepository.parse(ConstructorRepository.java:43)
	at sun.reflect.generics.repository.AbstractRepository.<init>(AbstractRepository.java:74)
	at sun.reflect.generics.repository.GenericDeclRepository.<init>(GenericDeclRepository.java:49)
	at sun.reflect.generics.repository.ConstructorRepository.<init>(ConstructorRepository.java:51)
	at sun.reflect.generics.repository.MethodRepository.<init>(MethodRepository.java:46)
	at sun.reflect.generics.repository.MethodRepository.make(MethodRepository.java:59)
	at java.lang.reflect.Method.getGenericInfo(Method.java:102)
	at java.lang.reflect.Method.getGenericReturnType(Method.java:255)
	at net.bytebuddy.description.type.TypeDescription$Generic$LazyProjection$ForLoadedReturnType.resolve(TypeDescription.java:5656)
	at net.bytebuddy.description.type.TypeDescription$Generic$LazyProjection.accept(TypeDescription.java:5297)
	at net.bytebuddy.description.method.MethodDescription$TypeSubstituting.getReturnType(MethodDescription.java:1320)
	at net.bytebuddy.description.method.MethodDescription$AbstractBase.asSignatureToken(MethodDescription.java:704)
	at net.bytebuddy.matcher.SignatureTokenMatcher.matches(SignatureTokenMatcher.java:30)
	at net.bytebuddy.matcher.SignatureTokenMatcher.matches(SignatureTokenMatcher.java:11)
	at net.bytebuddy.matcher.ElementMatcher$Junction$Conjunction.matches(ElementMatcher.java:101)
	at net.bytebuddy.matcher.FilterableList$AbstractBase.filter(FilterableList.java:96)
	at net.bytebuddy.dynamic.scaffold.subclass.SubclassImplementationTarget.invokeConstructor(SubclassImplementationTarget.java:59)
	at net.bytebuddy.dynamic.scaffold.subclass.SubclassImplementationTarget.invokeSuper(SubclassImplementationTarget.java:45)
	at net.bytebuddy.implementation.Implementation$Target$AbstractBase.invokeDominant(Implementation.java:364)
	at net.bytebuddy.implementation.SuperMethodCall$Appender.apply(SuperMethodCall.java:95)
	at net.bytebuddy.dynamic.scaffold.TypeWriter$MethodPool$Record$ForDefinedMethod$WithBody.applyCode(TypeWriter.java:616)
	at net.bytebuddy.dynamic.scaffold.TypeWriter$MethodPool$Record$ForDefinedMethod$WithBody.applyBody(TypeWriter.java:605)
	at net.bytebuddy.dynamic.scaffold.TypeWriter$MethodPool$Record$ForDefinedMethod.apply(TypeWriter.java:523)
	at net.bytebuddy.dynamic.scaffold.TypeWriter$Default$ForCreation.create(TypeWriter.java:4118)
	at net.bytebuddy.dynamic.scaffold.TypeWriter$Default.make(TypeWriter.java:1628)
	at net.bytebuddy.dynamic.scaffold.subclass.SubclassDynamicTypeBuilder.make(SubclassDynamicTypeBuilder.java:174)
	at net.bytebuddy.dynamic.scaffold.subclass.SubclassDynamicTypeBuilder.make(SubclassDynamicTypeBuilder.java:155)
	at net.bytebuddy.dynamic.DynamicType$Builder$AbstractBase.make(DynamicType.java:2560)
	at net.bytebuddy.dynamic.DynamicType$Builder$AbstractBase$Delegator.make(DynamicType.java:2662)
	at org.mockito.internal.creation.bytebuddy.SubclassBytecodeGenerator.mockClass(SubclassBytecodeGenerator.java:94)
	at org.mockito.internal.creation.bytebuddy.TypeCachingBytecodeGenerator$1.call(TypeCachingBytecodeGenerator.java:37)
	at org.mockito.internal.creation.bytebuddy.TypeCachingBytecodeGenerator$1.call(TypeCachingBytecodeGenerator.java:34)
	at net.bytebuddy.TypeCache.findOrInsert(TypeCache.java:138)
	... 38 more
Process finished with exit code 255

I am doing this code (an simple class written in kotlin):

package com.example.myapplication

import java.util.*
import kotlin.reflect.KProperty

open class Samples {

    private val samplesMap = mutableMapOf<String, Sample<Any>>()

    @Suppress("UNCHECKED_CAST")
    open val samples: List<Sample<Any>>
        get() = Collections.unmodifiableList(samplesMap.values.toList())

    open operator fun get(key: String): Sample<Any>? = samplesMap[key]

    open val keySample: Sample<String> by createSample(key = "key", defaultValue = "value")

    private fun <T> createSample(
            key: String,
            defaultValue: T): SampleDelegate<T> {
        val sample = ReleaseSample(key, defaultValue)
        registerSample(sample as Sample<Any>)
        return SampleDelegate(key)
    }

    private inner class SampleDelegate<out T>(val key: String) {

        operator fun getValue(samples: Samples, property: KProperty<*>): Sample<T> {
            return samplesMap[key] as Sample<T>
        }

    }

    protected fun decorate(decorator: (sample: Sample<Any>) -> Sample<Any>) {
        samplesMap.forEach { entry ->
            val key = entry.key
            val value = entry.value
            samplesMap.put(key, decorator(value))
        }
    }

    private fun registerSample(sample: Sample<Any>) {
        samplesMap[sample.key] = sample
    }

}

class ReleaseSample<out T>(
        override val key: String,
        override val value: T
) : Sample<T>

interface Sample<out T> {
    val key: String
    val value: T
}

And this code in the test section getting me into error: Mockito.spy(Samples())