Handle an interface with suspend that returns a JS friendly type

[shama]

If we have an interface that contains a suspend that returns a type that would get converted back and forth for JS (Long <-> Double), I noticed it tries to cast the type (.toLong()) before the promise is awaited.

An example:

@KustomExport
interface Thing {
    suspend fun getThing(): Long
}

class NonJSThing : Thing {
    override suspend fun getThing(): Long {
        return 1
    }
}

@KustomExport
class JSThing : Thing {
    override suspend fun getThing(): Long {
        return 1
    }
}

would generate the following code:

private class ImportedThing(
    internal val exported: Thing,
) : CommonThing {
    public override suspend fun getThing(): Long {
        val abortController = AbortController()
        val abortSignal = abortController.signal
        coroutineContext.job.invokeOnCompletion { abortController.abort() }
        val result = exported.getThing(    abortSignal = abortSignal)
        // It is casting the result to long before the promise has been awaited
        return result.toLong().await()
    }
}

with this change it now generates:

private class ImportedThing(
    internal val exported: Thing,
) : CommonThing {
    public override suspend fun getThing(): Long {
        val abortController = AbortController()
        val abortSignal = abortController.signal
        coroutineContext.job.invokeOnCompletion { abortController.abort() }
        val result = exported.getThing(    abortSignal = abortSignal).await()
        // The result has awaited the promise to resolve and is now a Double to be casted toLong()
        return result.toLong()
    }
}

[glureau]

Nice catch, thanks for your contribution!