Can't create Set<Interceptor> using Multibindings

Hi!

I trying to use multibinding to provide OkHttp Interceptors for the client.

    @Provides
    @Singleton
    fun provideOkHttpClient(interceptors: Set<Interceptor>): OkHttpClient {
        val builder = OkHttpClient.Builder()
        for (interceptor in interceptors) {
            builder.addNetworkInterceptor(interceptor)
        }
        return builder.build()
    }

    @Provides @IntoSet
    @Singleton
    fun provideLoggingInterceptor(): Interceptor =
            HttpLoggingInterceptor({ message -> Timber.tag("OkHttp").d(message) })

but can’t compile. There is an error:

error: java.util.Set<? extends okhttp3.Interceptor> cannot be provided without an @Provides-annotated method.

When I provide strings in the same way all works. But not with the Interceptor.

What I use: Kotlin 1.1.1 (kapt{generateStubs = true}) , Dagger 2.10

[tbroyer]

Dagger expects a java.util.Set<okhttp3.Interceptor>, not ? extends okhttp3.Interceptor. The problem is that you’re using Kotlin and Kotlin will by default translate a Set<X> into a Set<? extends X>: http://kotlinlang.org/docs/reference/java-to-kotlin-interop.html#variant-generics

Apparently (according to the docs), you should be able to make it work with Set<@JvmSuppressWildcards okhttp3.Interceptor>.

Wrt Set<String>, it works because String is final, so Kotlin emits a Set<String> as Set<? extends String> would have no sense. See this note in the docs:

NOTE: when the argument type is final, there’s usually no point in generating the wildcard, so Box<String> is always Box<String>, no matter what position it takes.

[ronshapiro]

This keeps coming up. I wonder if we should try to inspect the classpath for kotlin classes (if that’s possible?) and present an error when we see this