Assertion failure: out_arg.mode != ty::mo_val

[eholk]

I'm guessing this should be caught earlier in the compiler.

fn main() {
    fn echo[T](chan[T] c, chan[chan[T]] oc) {
        let port[T] p = port();
        oc <| chan(p);

        auto x;
        p |> x;
        c <| x;
    }

    auto p = port[int]();
    auto p2 = port[chan[int]]();

    spawn echo(chan(p), chan(p2));
}

[msullivan]

I think this code should work, not get caught at the typechecker level. It definitely should be able to work in the bind case.

[msullivan]

As it turns out, the bind case is the only case, since the failure occurs during the implicit binding of echo's type params. I'll fix this.

[eholk]

I think it depends on what the final decision is about sending functions and type parameters. I think we're leaning very strongly towards allowing it though.

[msullivan]

Hm. It looks like there are other issues with spawn and type parameters. (It doesn't seem to work even when the argument is by alias).

[msullivan]

So, it looks like the situation is: spawn is missing a lot of support for being type parametric. bind was missing a little bit of support in one case, but your test case tripped up against that before it got to any of spawn's problems. I am going to reclose this bug and open a new one for just the bind issue. I'll fix the bind issue and have the typechecker continue to reject spawns with type parameters (although with a better error message).