Kotlin @Binds error with covariant type parameter

Given the interface:

interface Example<T>

The implementation:

class ExampleImpl: Example<List<String>>

The module:

@Module
interface ExampleModule {
    @Binds
    fun provideExample(example: ExampleImpl): Example<List<String>>
}

The error @Binds methods must have only one parameter whose type is assignable to the return type is thrown at compile-time.

Important notes

1. it happens only with @Binds and not with @Provides So, this works:

@Module
class ExampleModule {
    @Provides
    fun provideExample(example: ExampleImpl): Example<List<String>> = example
}

1. it happens only when T is used as a covariant type parameter in the implementation of Example. So, this works:

class ExampleImpl: Example<MutableList<String>>

@Module
interface ExampleModule {
    @Binds
    fun provideExample(example: ExampleImpl): Example<MutableList<String>>
}

[fondesa]

My last try was the right one, simply I forgot the @Inject annotation on the constructor of ExampleImpl. The following summary is for people who encounter the same problem. Thanks for your help, considering that now it works, I close the issue, feel free to re-open it if needed.

Short summary

Interface

interface Example<T>

Implementation

class ExampleImpl @Inject constructor() : Example<List<@JvmSuppressWildcards String>>

Module

@Module
interface ExampleModule {
    @Binds
    fun provideExample(example: ExampleImpl): Example<List<String>>
}

Consumer

class Consumer @Inject constructor(private val example: @JvmSuppressWildcards Example<List<String>>)

[fondesa]

I tried with @JvmSuppressWildcards but it doesn’t help in this case. It’s still needed using the @Provides annotation.

Example:

@Module
class ExampleModule {
    @Provides
    fun provideExample(example: ExampleImpl): Example<List<String>> = example
}

class Consumer @Inject constructor(private val example: @JvmSuppressWildcards Example<List<String>>)