Beans of generic interfaces with nested Kotlin type parameters are not found

[helmbold]

Interface implementations that use nested type parameters with Kotlin types are not found as implementations. The following example fails:

package com.example.demo

import org.springframework.stereotype.Component

interface MyInterface<T> {
    fun doit(): T
}

@Component
class MyImplementation1 : MyInterface<Sequence<Int>> {
    override fun doit(): Sequence<Int> {
        TODO("not implemented")
    }
}

@Component
class MyConsumer(private val my: MyInterface<Sequence<Int>>)

The error message is:

Parameter 0 of constructor in com.example.demo.MyConsumer required a bean of type 'com.example.demo.MyInterface' that could not be found.

But if I use the (similar) Java interface Stream everything is fine:

package com.example.demo

import org.springframework.stereotype.Component
import java.util.stream.Stream

interface MyInterface<T> {
    fun doit(): T
}

@Component
class MyImplementation1 : MyInterface<Stream<Int>> {
    override fun doit(): Stream<Int> {
        TODO("not implemented")
    }
}

@Component
class MyConsumer(private val my: MyInterface<Stream<Int>>)

The application file is identical in both cases:

package com.example.demo

import org.springframework.boot.autoconfigure.SpringBootApplication
import org.springframework.boot.runApplication

@SpringBootApplication
class DemoApplication

fun main(args: Array<String>) {
    runApplication<DemoApplication>(*args)
}

Possibly related to #22313

[encircled]

Hi,

Yes, this is the same issue as #22313, Kotlin Sequence class has out variance, which causes the problem.

[hpy1994-java]

oops~

[sdeleuze]

I close this issue since that's a duplicate of #22313 indeed.