Lazy arguments in general allocate, but who is to blame for the allocation?
Isn't the allocation at the calling point?

This code:


void foo(lazy int x) @nogc {
    auto r = x(); // Error
}
void main() {
    foo(1);
}


Gives:

test.d(2,15): Error: @nogc function 'test.foo' cannot call non-@nogc delegate 'x'

Is it right to refuse the @nogc annotation on foo()? I think here foo should be allowed to be @nogc, while the main() can't be @nogc. What do you think?

Bye,
bearophile

On Sunday, 27 April 2014 at 13:09:39 UTC, bearophile wrote:
> Lazy arguments in general allocate, but who is to blame for the allocation?
> Isn't the allocation at the calling point?
>
> This code:
>
>
> void foo(lazy int x) @nogc {
>     auto r = x(); // Error
> }
> void main() {
>     foo(1);
> }
>
>
> Gives:
>
> test.d(2,15): Error: @nogc function 'test.foo' cannot call non-@nogc delegate 'x'
>
> Is it right to refuse the @nogc annotation on foo()? I think here foo should be allowed to be @nogc, while the main() can't be @nogc. What do you think?
>
> Bye,
> bearophile

It happens because attribute inference does not work properly on generated delegated for lazy argument. I think it is a bug

"lazy int x" is effectively same as "int delegate() x" and @nogc states that you can only call other @nogc functions and delegates from something annotated as @nogc.

Dicebot:

> It happens because attribute inference does not work properly on generated delegated for lazy argument. I think it is a bug
>
> "lazy int x" is effectively same as "int delegate() x" and @nogc states that you can only call other @nogc functions and delegates from something annotated as @nogc.

https://issues.dlang.org/show_bug.cgi?id=12664

Bye,
bearophile