Mocking a function while using IR silently fails and returns null

[inktomi]

If you have a project using Kotlin 1.4.21 (and mockito-kotlin 2.2.0) and you turn on the new IR backend, the mocking behavior changes.

Without IR, this mock seems to work private val validator: (String?, String?) -> Boolean = mock() - but with IR enabled, validator is null.

With useIR = false the following test passes:

    private val function: (Int, Int) -> Int = mock()

    @Test
    fun addition_isCorrect() {
        whenever(function.invoke(any<Int>(), any<Int>())).thenReturn(4)

        val result = function.invoke(2, 2)
        assertEquals(4, 2 + 2)
    }

But switch it to useIR = true and you get

java.lang.NullPointerException
	at com.example.mocktiokotlinir.ExampleUnitTest.addition_isCorrect(ExampleUnitTest.kt:21)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.base/java.lang.reflect.Method.invoke(Method.java:566)
	at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:59)
	at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
	at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:56)
	at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
	at org.junit.runners.ParentRunner$3.evaluate(ParentRunner.java:306)
	at org.junit.runners.BlockJUnit4ClassRunner$1.evaluate(BlockJUnit4ClassRunner.java:100)
	at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:366)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:103)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:63)
	at org.junit.runners.ParentRunner$4.run(ParentRunner.java:331)
	at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:79)
	at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:329)
	at org.junit.runners.ParentRunner.access$100(ParentRunner.java:66)
	at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:293)
	at org.junit.runners.ParentRunner$3.evaluate(ParentRunner.java:306)
	at org.junit.runners.ParentRunner.run(ParentRunner.java:413)
	at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
	at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:69)
	at com.intellij.rt.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:33)
	at com.intellij.rt.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:220)
	at com.intellij.rt.junit.JUnitStarter.main(JUnitStarter.java:53)

[bohsen]

Reproducer: https://github.com/bohsen/TestProject

Failing tests: https://github.com/bohsen/TestProject/blob/0203ad78a35feeb861b442e64e6c45dff97ab41b/src/test/kotlin/com/mockito/mockitokotlin2/MockingTest.kt#L355

Problem persists whenever you mock a lambda (or a Function). Hopefully the new IR backend isn't about to be enabled by default just yet. Fails with both kotlin 1.4.21, 1.4.30-M1 and 1.4.30-RC.

Youtrack issue: https://youtrack.jetbrains.com/issue/KT-44429

[bohsen]

Fixed in kotlin 1.5.