As expected, the following trivial case works:

void main() {
    auto func = delegate(int i) {};  // expects int

    func(const(int)(42));            // passes const(int)
}


The following concurrency program fails at runtime:

import core.thread;
import std.concurrency;

void foo() {
    receiveOnly!int();            // expects int
}

void main() {
    auto worker = spawn(&foo);

    // Sends const(int)
    worker.send(const(int)(42));  // sends const(int)

    thread_joinAll;
}

std.concurrency.MessageMismatch@std/concurrency.d(224): Unexpected message type: expected 'int', got 'const(int)'


Feature or bug? (receive() is worse because as it simply ignores the message.)

Ali

On 3/30/16 8:01 PM, Ali Çehreli wrote:
> As expected, the following trivial case works:
>
> void main() {
>      auto func = delegate(int i) {};  // expects int
>
>      func(const(int)(42));            // passes const(int)
> }
>
>
> The following concurrency program fails at runtime:
>
> import core.thread;
> import std.concurrency;
>
> void foo() {
>      receiveOnly!int();            // expects int
> }
>
> void main() {
>      auto worker = spawn(&foo);
>
>      // Sends const(int)
>      worker.send(const(int)(42));  // sends const(int)
>
>      thread_joinAll;
> }
>
> std.concurrency.MessageMismatch@std/concurrency.d(224): Unexpected
> message type: expected 'int', got 'const(int)'
>
>
> Feature or bug? (receive() is worse because as it simply ignores the
> message.)

Bug, but probably of the enhancement variety I think (I don't think this is a small project). Receive should canonicalize the input and requested receive type. That is, receiveOnly!(const(int)) should really call receiveOnly!int, and send!(const(int)) should really call send!int.

Generous usage of Unqual should be done here.

-Steve

On Thursday, 31 March 2016 at 13:47:25 UTC, Steven Schveighoffer wrote:
> Bug, but probably of the enhancement variety I think (I don't think this is a small project). Receive should canonicalize the input and requested receive type. That is, receiveOnly!(const(int)) should really call receiveOnly!int, and send!(const(int)) should really call send!int.
>
> Generous usage of Unqual should be done here.
>
> -Steve

Doesn't receive use Algebraic under the hood? I know that Algebraic has various issues with const and immutable types that I run into every once and awhile.