elided lifetime #46254

Dylan-DPC-zz · 2017-11-25T12:46:24Z

Hey
Having a problem with my config so decided to make a WIP PR nevertheless. Will add some more tests.

rust-highfive · 2017-11-25T12:46:35Z

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @michaelwoerister (or someone else) soon.

If any changes to this PR are deemed necessary, please add them as extra commits. This ensures that the reviewer can see what has changed since they last reviewed the code. Due to the way GitHub handles out-of-date commits, this should also make it reasonably obvious what issues have or haven't been addressed. Large or tricky changes may require several passes of review and changes.

Please see the contribution instructions for more information.

michaelwoerister · 2017-11-27T09:28:18Z

Unassigning myself since this isn't really my area. Please make sure to make the appropriate folks from @rust-lang/compiler aware of your PR, @Dylan-DPC.

Dylan-DPC-zz · 2017-11-27T09:52:05Z

@nikomatsakis

bors · 2017-12-02T00:17:01Z

☔ The latest upstream changes (presumably #46430) made this pull request unmergeable. Please resolve the merge conflicts.

eddyb · 2017-12-03T00:01:24Z

BTW you should rebase instead of merging.

Dylan-DPC-zz · 2017-12-03T06:53:29Z

Yeah thanks. But i resolved the conflicts on the Github UI (since it were minor conflicts) which i assume merges by default.

eddyb · 2017-12-03T13:19:55Z

You can still rebase, and it will remove the merge commit.

Dylan-DPC-zz · 2017-12-03T18:06:41Z

Yeah sure

bors · 2017-12-05T03:00:28Z

☔ The latest upstream changes (presumably #46305) made this pull request unmergeable. Please resolve the merge conflicts.

nikomatsakis · 2017-12-06T15:05:23Z

r? @nikomatsakis

Sorry, somehow this didn't wind up assigned to me.

nikomatsakis · 2017-12-06T18:08:01Z

@Dylan-DPC so it seems like you're not actually issuing the lint anywhere -- is that right? Do you need help with just how to do this?

nikomatsakis · 2017-12-06T18:10:49Z

Ah, actually, you're probably going to hit the same issue that @gaurikholkar hit in #46441. In particular, we can't issue lints from resolve_lifetimes right now because of when it executes. I fixed this as part of this commit in Gauri's PR. You should probably rebase atop that commit, but maybe I should factor it out into a separate PR so you are not blocked on #46441 having landed.

nikomatsakis · 2017-12-06T18:11:07Z

That said, #46441 is a good PR to look at for how to issue lints in general. =)

Dylan-DPC-zz · 2017-12-06T18:25:43Z

Yeah i will rebase ontop of it.

aidanhs · 2017-12-14T10:36:39Z

Hi @Dylan-DPC, how are you doing with this? #46657 is merged so I think you can rebase on top of that now.

gaurikholkar-zz · 2017-12-30T12:27:48Z

src/librustc/lint/builtin.rs

@@ -292,6 +298,7 @@ impl LintPass for HardwiredLints {
 COERCE_NEVER,
 SINGLE_USE_LIFETIME,
 TYVAR_BEHIND_RAW_POINTER
+ ELIDED_LIFETIME_IN_PATH


Missing a comma on the line above

Thanks fixed

Dylan-DPC-zz · 2017-12-30T12:28:26Z

hi @nikomatsakis

so it seems like you're not actually issuing the lint anywhere -- is that right? Do you need help with just how to do this?

yeah trying to figure out how to issue. Should i just issue it when deprecated is true?

gaurikholkar-zz · 2017-12-30T12:29:21Z

src/test/ui/in-band-lifetimes/ellided_lifetimes.rs

@@ -0,0 +1,16 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT


Add the .stderr file for the ui test

You can run ./x.py test --stage 1 src/test/ui to get the stderr file

Ya thanks. Just have to work on some stuff before that

nikomatsakis

Obviously you have to add the code that actually issues the lint =) let me know if you need any tips on that

nikomatsakis · 2017-12-06T18:07:19Z

src/librustc/lint/builtin.rs

+declare_lint! {
+ pub ELIDED_LIFETIME_IN_PATH,
+ Allow,
+ "hidden lifetime parameters are deprecated, try `Foo<'_>`"


Let's change the message to:

elided lifetime parameters from structs, enums, or such types are deprecated; use '_ instead

nikomatsakis · 2018-01-03T19:51:44Z

src/test/ui/in-band-lifetimes/ellided_lifetimes.rs

+#![deny(elided_lifetime_in_path)]
+struct Foo<'a> { x: &'a u32 }
+fn foo(x: &Foo) {
+// ^^^ warning: hidden lifetime parameters are deprecated, try `Foo<'_>`


This should be //~^ ERROR: ...

That is an annotation that indicates that we expect an error on the line above. The .stderr file will give more precise information.

nikomatsakis · 2018-01-03T19:52:52Z

Oh, I missed this comment:

yeah trying to figure out how to issue. Should i just issue it when deprecated is true?

Yep, I think so.

nikomatsakis · 2018-01-03T19:54:31Z

To issue the lint (i.e., when deprecated is true), you would want something like this:

rust/src/librustc/middle/resolve_lifetime.rs

Lines 1228 to 1234 in 78493ed

 this.tcx 

 .struct_span_lint_node(lint::builtin::SINGLE_USE_LIFETIME, 

 id, 

 span, 

 &format!("lifetime name `{}` only used once", 

 hir_lifetime.name.name())) 

 .emit();

Dylan-DPC-zz · 2018-01-04T11:06:41Z

Thanks. My question was do i need to do perform any other check?

eddyb · 2018-02-01T20:50:25Z

@Dylan-DPC git reflog means you only lose commits if you don't look at them for a month or so.

Dylan-DPC-zz · 2018-02-01T21:00:43Z

@eddyb nice. Thanks

Dylan-DPC-zz · 2018-02-02T06:59:55Z

@bors r+

bors · 2018-02-02T06:59:56Z

@Dylan-DPC: 🔑 Insufficient privileges: Not in reviewers

estebank · 2018-02-02T16:30:39Z

@bors r=nikomatsakis

bors · 2018-02-02T16:30:40Z

📌 Commit accd997 has been approved by nikomatsakis

bors · 2018-02-02T22:26:11Z

⌛ Testing commit accd997 with merge 2575f9713fc5cbfffc83cc99ed2430d4cbba2ecd...

bors · 2018-02-03T01:26:53Z

💔 Test failed - status-travis

shepmaster · 2018-02-03T02:04:11Z

The job exceeded the maximum time limit for jobs, and has been terminated.

@bors retry

bors · 2018-02-03T07:12:34Z

⌛ Testing commit accd997 with merge d1c54614c99d7227d5ed8c15ace39887e1e8a582...

bors · 2018-02-03T09:16:10Z

💔 Test failed - status-travis

kennytm · 2018-02-03T14:13:43Z

@bors retry #43283

bors · 2018-02-03T14:38:58Z

⌛ Testing commit accd997 with merge aa0a5a8...

elided lifetime Closes #45992 Hey Having a problem with my config so decided to make a WIP PR nevertheless. Will add some more tests.

bors · 2018-02-03T17:28:04Z

☀️ Test successful - status-appveyor, status-travis
Approved by: nikomatsakis
Pushing aa0a5a8 to master...

The existing elided-lifetimes-in-paths lint (introduced in Nov. 2017's accd997 / rust-lang#46254) lacked stuctured suggestions and—much more alarmingly—produced false positives on associated functions (like `Ref::clone`) and on anonymous '_ lifetimes (!!—yes, the very anonymous lifetimes that we meant to suggest "instead"). That this went apparently unnoticed for so long maybe tells you something about how many people actually bother to flip on allow-by-default lints. After many hours of good old-fashioned American elbow grease—and a little help from expert reviewers—it turns out that getting the right answer is a lot easier if we fire the lint while lowering the Higher Intermediate Representation. The lint is promoted to the idioms-2018 group. Also, in the matter of test filenames, "elided" only has one 'l' (see, e.g., https://en.wiktionary.org/wiki/elide). Resolves rust-lang#52041.

@nikomatsakis

…_re-pub-lic, r=nikomatsakis add structured suggestions and fix false-positive for elided-lifetimes-in-paths lint This adds structured suggestions to the elided-lifetimes-in-paths lint (introduced in Nov. 2017's #46254), prevents it from emitting a false-positive on anonymous (underscore) lifetimes (!), and adds it to the idioms-2018 group (#52041). ~~As an aside, "elided-lifetimes-in-paths" seems like an unfortunate name, because it's not clear exactly what "elided" means. The motivation for this lint (see original issue #45992, and [RFC 2115](https:/rust-lang/rfcs/blob/e978a8d3017a01d632f916140c98802505cd1324/text/2115-argument-lifetimes.md#motivation)) seems to be specifically about not supplying angle-bracketed lifetime arguments to non-`&` types, but (1) the phrase "lifetime elision" has historically also referred to the ability to not supply a lifetime name to `&` references, and (2) an `is_elided` method in the HIR returns true for anoymous/underscore lifetimes, which is _not_ what we're trying to lint here. (That naming confusion is almost certainly what led to the false positive addressed here.) Given that the lint is relatively new and is allow-by-default, is it too late to rename it ... um, _again_ (#50879)?~~ ~~This does _not_ address a couple of other false positives discovered in #52041 (comment) ![elided_states](https://user-images.githubusercontent.com/1076988/42302137-2bf9479c-7fce-11e8-8bd0-f29aefc802b6.png) r? @nikomatsakis cc @nrc @petrochenkov

rust-highfive assigned michaelwoerister Nov 25, 2017

michaelwoerister removed their assignment Nov 27, 2017

rust-highfive assigned nikomatsakis Dec 6, 2017

Dylan-DPC-zz force-pushed the ellided-lifetime branch 2 times, most recently from 09343db to ee254cb Compare December 30, 2017 11:02

gaurikholkar-zz reviewed Dec 30, 2017

View reviewed changes

nikomatsakis reviewed Jan 3, 2018

View reviewed changes

kennytm added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Feb 2, 2018

bors added a commit that referenced this pull request Feb 3, 2018

Auto merge of #46254 - Dylan-DPC:ellided-lifetime, r=nikomatsakis

aa0a5a8

elided lifetime Closes #45992 Hey Having a problem with my config so decided to make a WIP PR nevertheless. Will add some more tests.

bors merged commit accd997 into rust-lang:master Feb 3, 2018

Dylan-DPC-zz deleted the ellided-lifetime branch February 3, 2018 17:38

nikomatsakis mentioned this pull request Feb 5, 2018

lint against "silent elision" in structs/enums/etc #45992

Closed

This was referenced Jul 4, 2018

edition lint: prefer '_ to lifetime elision in types #52041

Closed

add structured suggestions and fix false-positive for elided-lifetimes-in-paths lint #52069

Merged

		@@ -0,0 +1,16 @@
		// Copyright 2017 The Rust Project Developers. See the COPYRIGHT

elided lifetime #46254

elided lifetime #46254

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Dylan-DPC-zz commented Nov 25, 2017

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michaelwoerister commented Nov 27, 2017

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