Lint ignored #[inline] on function prototypes

[varkor]

Fixes #51280.

• Adds a unused_attribute lint for #[inline] on function prototypes.
• As a consequence, foreign items, impl items and trait items now have their attributes checked, which could cause some code to no longer compile (it was previously erroneously ignored).

[rust-highfive]

r? @matthewjasper

(rust_highfive has picked a reviewer for you, use r? to override)

[rust-highfive]

The job x86_64-gnu-llvm-6.0 of your PR failed (pretty log, raw log). Through arcane magic we have determined that the following fragments from the build log may contain information about the problem.

Click to expand the log.

2019-10-11T01:43:19.0836625Z ##[command]git remote add origin https://github.com/rust-lang/rust
2019-10-11T01:43:19.0923997Z ##[command]git config gc.auto 0
2019-10-11T01:43:19.1011319Z ##[command]git config --get-all http.https://github.com/rust-lang/rust.extraheader
2019-10-11T01:43:19.1078670Z ##[command]git config --get-all http.proxy
2019-10-11T01:43:19.1214486Z ##[command]git -c http.extraheader="AUTHORIZATION: basic ***" fetch --force --tags --prune --progress --no-recurse-submodules --depth=2 origin +refs/heads/*:refs/remotes/origin/* +refs/pull/65294/merge:refs/remotes/pull/65294/merge
---
2019-10-11T02:15:09.5374260Z    Compiling jobserver v0.1.16
2019-10-11T02:15:11.9251952Z    Compiling env_logger v0.7.0
2019-10-11T02:15:12.5820649Z    Compiling rustc-hash v1.0.1
2019-10-11T02:15:12.6895384Z    Compiling rustc_apfloat v0.0.0 (/checkout/src/librustc_apfloat)
2019-10-11T02:15:12.8708523Z error[E0518]: attribute should be applied to function or closure
2019-10-11T02:15:12.8708962Z    --> <::bitflags::__impl_bitflags macros>:73:22
2019-10-11T02:15:12.8709318Z     |
2019-10-11T02:15:12.8711001Z 1   |   /   ($ BitFlags : ident : $ T : ty
2019-10-11T02:15:12.8711767Z 3   |   |        $
2019-10-11T02:15:12.8711767Z 3   |   |        $
2019-10-11T02:15:12.8712190Z 4   |   |        ($ (# [$ attr : ident $ ($ args : tt) *]) * $ Flag : ident = $ value :
2019-10-11T02:15:12.8712510Z ...     |
2019-10-11T02:15:12.8712925Z 73  |   |                   { $ (# [inline] const $ Flag : $ T = 0 ;) + } impl __BitFlags
2019-10-11T02:15:12.8713675Z     |   |                        ^^^^^^^^^^ ------------------------ not a function or closure
2019-10-11T02:15:12.8714041Z ...     |
2019-10-11T02:15:12.8714456Z 248 |   |   } ; ($ (# [$ filtered : meta]) * const $ ($ item : tt) *) =>
2019-10-11T02:15:12.8714856Z 249 |   |   { $ (# [$ filtered]) * const $ ($ item) * } ;
2019-10-11T02:15:12.8715668Z     |   |_______________________________________________- in this expansion of `__impl_bitflags!` (#3)
2019-10-11T02:15:12.8715986Z     | 
2019-10-11T02:15:12.8716573Z    ::: <::bitflags::__bitflags macros>:1:1
2019-10-11T02:15:12.8716882Z     |
2019-10-11T02:15:12.8717323Z 1   |     / ($ (# [$ outer : meta]) * ($ ($ vis : tt) *) $ BitFlags : ident : $ T : ty
2019-10-11T02:15:12.8717724Z 2   |     |  {
2019-10-11T02:15:12.8718091Z 3   |     |      $
2019-10-11T02:15:12.8718539Z 4   |     |      ($ (# [$ inner : ident $ ($ args : tt) *]) * $ Flag : ident = $ value :
2019-10-11T02:15:12.8718871Z ...       |
2019-10-11T02:15:12.8719303Z 10  |     |     struct $ BitFlags { bits : $ T, } __impl_bitflags !
2019-10-11T02:15:12.8719684Z     |  ___|_______________________________________-
2019-10-11T02:15:12.8720091Z 11  | |   |     {
2019-10-11T02:15:12.8720497Z 12  | |   |         $ BitFlags : $ T
2019-10-11T02:15:12.8720983Z 13  | |   |         { $ ($ (# [$ inner $ ($ args) *]) * $ Flag = $ value ;) + }
2019-10-11T02:15:12.8721776Z     | |___|_____- in this macro invocation (#3)
2019-10-11T02:15:12.8722165Z 15  |     | } ;
2019-10-11T02:15:12.8722165Z 15  |     | } ;
2019-10-11T02:15:12.8722571Z     |     |___- in this expansion of `__bitflags!` (#2)
2019-10-11T02:15:12.8722862Z     | 
2019-10-11T02:15:12.8723176Z    ::: <::bitflags::bitflags macros>:1:1
2019-10-11T02:15:12.8723433Z     |
2019-10-11T02:15:12.8723878Z 1   |    /  ($ (# [$ outer : meta]) * pub struct $ BitFlags : ident : $ T : ty
2019-10-11T02:15:12.8724238Z 2   |    |   {
2019-10-11T02:15:12.8724617Z 3   |    |       $
2019-10-11T02:15:12.8725582Z 4   |    |       ($ (# [$ inner : ident $ ($ args : tt) *]) * const $ Flag : ident = $
2019-10-11T02:15:12.8725935Z ...      |
2019-10-11T02:15:12.8726309Z 8   |  / |      __bitflags !
2019-10-11T02:15:12.8726720Z 9   |  | |      {
2019-10-11T02:15:12.8727185Z 10  |  | |          $ (# [$ outer]) * (pub) $ BitFlags : $ T
2019-10-11T02:15:12.8727820Z 11  |  | |          { $ ($ (# [$ inner $ ($ args) *]) * $ Flag = $ value ;) + }
2019-10-11T02:15:12.8773575Z     |  |_|______- in this macro invocation (#2)
2019-10-11T02:15:12.8773931Z ...      |
2019-10-11T02:15:12.8774269Z 39  |    |      }
2019-10-11T02:15:12.8774600Z 40  |    |  } ;
2019-10-11T02:15:12.8774600Z 40  |    |  } ;
2019-10-11T02:15:12.8775333Z     |    |____- in this expansion of `bitflags::bitflags!` (#1)
2019-10-11T02:15:12.8775992Z    ::: src/librustc_apfloat/lib.rs:48:1
2019-10-11T02:15:12.8776244Z     |
2019-10-11T02:15:12.8776583Z 48  | /     bitflags::bitflags! {
2019-10-11T02:15:12.8776583Z 48  | /     bitflags::bitflags! {
2019-10-11T02:15:12.8776975Z 49  | |         /// IEEE-754R 7: Default exception handling.
2019-10-11T02:15:12.8777312Z 50  | |         ///
2019-10-11T02:15:12.8777702Z 51  | |         /// UNDERFLOW or OVERFLOW are always returned or-ed with INEXACT.
2019-10-11T02:15:12.8778344Z 60  | |         }
2019-10-11T02:15:12.8778662Z 61  | |     }
2019-10-11T02:15:12.8779031Z     | |_____- in this macro invocation (#1)
2019-10-11T02:15:12.8779124Z 
---
2019-10-11T02:15:14.2458568Z == clock drift check ==
2019-10-11T02:15:14.2477280Z   local time: Fri Oct 11 02:15:14 UTC 2019
2019-10-11T02:15:14.3990238Z   network time: Fri, 11 Oct 2019 02:15:14 GMT
2019-10-11T02:15:14.3995582Z == end clock drift check ==
2019-10-11T02:15:15.3551616Z ##[error]Bash exited with code '1'.
2019-10-11T02:15:15.3604602Z ##[section]Starting: Checkout
2019-10-11T02:15:15.3607259Z ==============================================================================
2019-10-11T02:15:15.3607327Z Task         : Get sources
2019-10-11T02:15:15.3607382Z Description  : Get sources from a repository. Supports Git, TfsVC, and SVN repositories.

I'm a bot! I can only do what humans tell me to, so if this was not helpful or you have suggestions for improvements, please ping or otherwise contact @TimNN. (Feature Requests)

[Centril]

cc @rust-lang/lang This seems like a reasonable extension of the unused_attributes lint so I'm not going to I-nominate the PR for a language team meeting to save us time but I thought y'all should be aware. :)

[varkor]

We should do a crater run of this once it builds, because it's possible (as seen in bitflags) that there are accidental #[inline] attributes on trait or extern items that don't permit them. Hopefully we can just fix the fallout; it'd be ugly to have to continue to allow these for some time.

[cramertj]

Hopefully we can just fix the fallout; it'd be ugly to have to continue to allow these for some time.

This is just a lint, right? I don't think we need a crater run to ward off ecosystem breakage for new lints, especially on one that's so niche.

[Centril]

If you look at the diff it introduces both warnings and errors in different places.

[nikomatsakis]

Based on my skimming of the tests, is it correct that the errors arise when #[inline] is applied to non-functions, like consts or statics? And this used to just be ignored or something?

[varkor]

Errors were previously emitted on #[inline] on consts or statics (any non-functions), but they were not being emitted on associated/foreign items (which was an oversight). Now they're emitted on any item, which was a natural consequence of adding the lint for #[inline] on prototypes.

So this adds both a lint, but also errors that had previously accidentally been left out.

[varkor]

@bors try

[bors]

⌛ Trying commit 185b013a9f9d1286e7ae78ff1593d10dcca8b2f8 with merge 38f08371587f97c145dedb2c055ac7b01bf1e788...

[bors]

☀️ Try build successful - checks-azure
Build commit: 38f08371587f97c145dedb2c055ac7b01bf1e788 (38f08371587f97c145dedb2c055ac7b01bf1e788)

[varkor]

@craterbot check

[craterbot]

👌 Experiment pr-65294 created and queued.
🤖 Automatically detected try build 38f08371587f97c145dedb2c055ac7b01bf1e788
🔍 You can check out the queue and this experiment's details.

ℹ️ Crater is a tool to run experiments across parts of the Rust ecosystem. Learn more

[craterbot]

🚧 Experiment pr-65294 is now running

ℹ️ Crater is a tool to run experiments across parts of the Rust ecosystem. Learn more

[craterbot]

🎉 Experiment pr-65294 is completed!
📊 2540 regressed and 0 fixed (74234 total)
📰 Open the full report.

⚠️ If you notice any spurious failure please add them to the blacklist!
ℹ️ Crater is a tool to run experiments across parts of the Rust ecosystem. Learn more

[bors]

⌛ Testing commit f47f530 with merge a77114b5f48a74317d731c20883212038125667b...

[Centril]

@bors retry

[bors]

⌛ Testing commit f47f530 with merge 2dd4e73...

[bors]

☔ The latest upstream changes (presumably #65919) made this pull request unmergeable. Please resolve the merge conflicts.