Mark f16 and f128 as incomplete features

[tgross35]

See #116909 (comment).

Unfortunately this will probably have a lot that needs to be updated, just getting this started to figure out exactly what that will be.

r? @scottmcm

[tgross35]

@rustbot author
@rustbot label +F-f16_and_F128

[tgross35]

Is there any guideline for what constitutes an incomplete feature? The ABI issues and maybe missing symbols definitely seem to qualify this, but it seems that a missing trait impl/method relative to f32 & f64 (as per the original comment) wouldn't necessarily be in the same boat.

[tgross35]

@rustbot label +rla-silenced

[scottmcm]

Thanks for making a PR!

I don't know if there's a concrete definition.

Personally, I tend to think of it as "we're not ready for experience reports because we know that if you try it you're going to hit stuff that doesn't work". Basically, a marker that you'll likely hit obvious problems and that we probably don't want bugs about those because we know it's not done yet. A "we need devs not users right now", kinda.

[scottmcm]

Oh, bleh

  error: the feature `f128` is incomplete and may not be safe to use and/or cause compiler crashes
     --> library/std/src/lib.rs:295:12
      |
  295 | #![feature(f128)]
      |            ^^^^

Maybe that means this can't be marked incomplete, because we don't want to allow incomplete features in core :/

[tgross35]

I just saw that, but it looks like this is enabled in core so maybe it's okay? It is a bit unfortunate that you can't enable a specific list of incomplete features, since the reason they are incomplete is quite a range.

[workingjubilee]

Mmh.

[workingjubilee]

Please open a bug for "incomplete features that std should not depend on" vs. "incomplete features that std... has to implement..." and cc Boxy and Nils about it.

[tgross35]

Good idea, opened #127741

[tgross35]

Unfortunately clippy uses these features too so that's another allow(incomplete_features) :(

[tgross35]

Ah, GH doesn't like me fixing a typo in my branch name. Reopened at #127743