Error "illegal type constraint parameter"

[stephentetley]

I'm working on changing Iterable to have an associated Elm type rather than being Iterable[t: Type -> Type].

At the moment I'm not able to assert that Iterable's Elm associated type is an instance of Order. Have I got the syntax wrong or is this not implemented yet?

enqueueAll from MutQueue shows what I'm trying to do:

///
/// Enqueues each element in `l` into `mq`.
///
pub def enqueueAll(mq: MutQueue[Iterable.Elm[m], r], m: m): Unit \ r with Iterable[m], Order[Iterable.Elm[m]] =
    foreach(x <- m) {
        enqueue(mq, x)
    }

-- Syntax Error -------------------------------------------------- MutQueue.flix

>> Illegal type constraint parameter.

113 |     pub def enqueueAll(mq: MutQueue[Iterable.Elm[m], r], m: m): Unit \ r with Iterable[m], Order[Iterable.Elm[m]] =
                                                                                                 ^^^^^^^^^^^^^^^^^^^^^^
                                                                                                 illegal type constraint parameter
        

Thanks

[magnus-madsen]

@mlutze Does this work?

[mlutze]

It's indeed illegal at the moment; we need to discuss what exactly should be allowed.

Meanwhile, there is a workaround:

def enqueueAll(mq: MutQueue[Iterable.Elm[m], r], m: m): Unit \ r with Iterable[m], Order[freevar] where Iterable.Elm[m] ~ freevar
                                                                                         ^^^^^^^                          ^^^^^^^

We just add another type variable and associate it with both Iterable.Elm[m] and Order.

[stephentetley]

Thanks Matthew, I had to bind it within the "function part" of the type signature:

pub def enqueueAll(mq: MutQueue[elt, r], m: m): Unit \ r with Iterable[m], Order[elt] where Iterable.Elm[m] ~ elt =