When creating Tasks to run on a TaskPool using std.parallelism, it looks like I can't call functions that have immutable objects:

code:
import std.parallelism;

class Test {
}

void doSomething(immutable(Test) test) {
}

void main() {
        immutable(Test) test = new immutable(Test)();
        taskPool().put(task!(doSomething)(test));
}


compiler output:
Error: can only initialize const member __args_field_0 inside constructor
Error: this is not mutable
/usr/include/d2/4.6.0/std/parallelism.d:734: Error: template instance std.parallelism.Task!(doSomething,immutable(Test)) error instantiating
tasktest.d:11:        instantiated from here: task!(doSomething,immutable(Test))


Is this something that can be fixed, or does this depend on having tail const support (which would hopefully work for immutable as well)? This use case seems particularly important as immutability is the simplest way to ensure safe multithreading.

This should work, but I had neglected to put a test in for it.  Anyhow, the underlying reason it doesn't work is Bug 6588.

I found a workaround for 6588 and put it into a larger pull request with various improvements to std.parallelism:

https://github.com/D-Programming-Language/phobos/pull/217

This has been fixed for a few releases.  Closing.