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Should warn for enabling the same feature twice #53032

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scottmcm opened this issue Aug 3, 2018 · 1 comment · Fixed by #52644
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Should warn for enabling the same feature twice #53032

scottmcm opened this issue Aug 3, 2018 · 1 comment · Fixed by #52644

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@scottmcm
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scottmcm commented Aug 3, 2018 •
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I just noticed that rustc_mir is enabling in_band_lifetimes twice:

rust/src/librustc_mir/lib.rs

Line 18 in 88e0ff1

#![feature(in_band_lifetimes)]

rust/src/librustc_mir/lib.rs

Line 30 in 88e0ff1

#![feature(in_band_lifetimes)]

Would be good to have a warning to help people notice this kind of superfluous code.
@varkor
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varkor commented Aug 3, 2018

This is fixed by #52644.

@varkor varkor mentioned this issue Aug 3, 2018
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bors added a commit that referenced this issue Aug 6, 2018
@bors
Auto merge of #52644 - varkor:lib-feature-gate-2, r=withoutboats
b239743 
Add errors for unknown, stable and duplicate feature attributes

- Adds an error for unknown (lang and lib) features.
- Extends the lint for unnecessary feature attributes for stable features to libs features (this already exists for lang features).
- Adds an error for duplicate (lang and lib) features.

```rust
#![feature(fake_feature)] //~ ERROR unknown feature `fake_feature`

#![feature(i128_type)] //~ WARNING the feature `i128_type` has been stable since 1.26.0

#![feature(non_exhaustive)]
#![feature(non_exhaustive)] //~ ERROR duplicate `non_exhaustive` feature attribute
```

Fixes #52053, fixes #53032 and address some of the problems noted in #44232 (though not unused features).

There are a few outstanding problems, that I haven't narrowed down yet:
- [x] Stability attributes on macros do not seem to be taken into account.
- [x] Stability attributes behind `cfg` attributes are not taken into account.
- [x] There are failing incremental tests.
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Add errors for unknown, stable and duplicate feature attributes varkor/rust
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@varkor @scottmcm