NativeCall void function returns Mu type object

[0rir]

Doc' that NativeCall's returns trait's default is Mu:U.

Emphasize void-is-only-for-pointers with its own paragraph.

Ref #5293

[0rir]

@raiph, thank you. My phrasing was meant to convey what the return value is, not the constraints it must meet.

NativeCall chokes on the Mu:D and Mu:U type-ishes. But by the definition of definedness the return is :U.

Should this be on the language/nativetypes page also or instead?

Should this be tagged as an Rakudo-ism?

[0rir]

There is a good case for the doc being more rigorous in its usage of defined versus DEFINITE; I am not sure that would be a net positive.

It is a flaw in the implementation or design that an is native sub's sig cannot bear a -->Mu:U which is why it is not in the PR.

Smileys are a fine refinement in @TimToady's design.

use NativeCall;
sub perror( Str $s) is native { … }
sub raku( Str $s -->Mu:U) { perror( $s) }
raku 'farewell';    # farewell: Success

[0rir]

@raiph, be relieved for I am not pained by our discussion. It is just a matter of disagreeing.
It is usual that I am not as quick to reply as most here; this time I regret my delay for the extention of you unease.

I agree with the info in your "shot". Depending on your target audience, I see varied improvements possible. If you are interested, let me know.