Improve SubSupConflict with a named and an anonymous lifetime parameter #42701 #44167

cengiz-io · 2017-08-29T21:24:03Z

Hello!

This fixes #42701.

UPDATE 01

Tests are producing different results between different env builds.
This inconsistency might take a long time to investigate and fix. So, be patient

UPDATE 02

Changed an FxHashMap with a BTreeMap. Inconsistency seems to be resolved for now.

rust-highfive · 2017-08-29T21:24:14Z

r? @pnkfelix

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

gaurikholkar-zz · 2017-08-30T03:45:46Z

src/test/ui/lifetime-errors/one_named_and_one_anonymous.stderr

@@ -0,0 +1,41 @@
+error[E0495]: cannot infer an appropriate lifetime for borrow expression due to conflicting requirements


#42700
The first snippet of code, that's how the ui test must output

gaurikholkar-zz · 2017-08-30T03:46:27Z

src/test/ui/lifetime-errors/two_anonymous.rs

@@ -0,0 +1,24 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT


This is of type ConcreteFailure, not SubSupConflict

gaurikholkar-zz · 2017-08-30T16:08:07Z

src/librustc/infer/error_reporting/named_anon_conflict.rs

    pub fn try_report_named_anon_conflict(&self, error: &RegionResolutionError<'tcx>) -> bool {
        let (span, sub, sup) = match *error {
            ConcreteFailure(ref origin, sub, sup) => (origin.span(), sub, sup),
+            SubSupConflict(_, ref origin, sub, _, sup) => (origin.span(), sub, sup),
            _ => return false, // inapplicable
        };



You will have to remove the is_self_anon check. Maybe you can try an example without self, that should work.

nikomatsakis · 2017-08-30T16:15:10Z

r? @nikomatsakis

nikomatsakis · 2017-08-30T19:17:43Z

I think this is a good test case:

struct Foo {
    field: i32,
}

fn foo2<'a>(a: &'a Foo, x: &i32) -> &'a i32 {
    if true {
        let p: &i32 = &a.field;
        &*p
    } else {
        &*x
    }
}

fn main() { }

arielb1 · 2017-09-05T18:17:17Z

Hi @cengizio! Nice PR! Can you add @nikomatsakis's test so we can see how the errors look and fix this?

gaurikholkar-zz · 2017-09-07T05:52:15Z

@nikomatsakis can you suggest a test case for anon_anon conflicts too?

nikomatsakis · 2017-09-08T15:11:10Z

@gaurikholkar I guess that's a bit harder. If you just remove the named lifetime, then the elision rules will fail. You can use an &self to still create a conflict, but then we get into the rules that disable anon-anon reporting around self, I believe.

bors · 2017-09-10T18:39:05Z

☔ The latest upstream changes (presumably #44079) made this pull request unmergeable. Please resolve the merge conflicts.

nikomatsakis · 2017-09-14T13:40:44Z

@cengizio

Maybe try this example too?

struct Foo {
    field: i32, 
}

fn foo2<'a, 'b>(a: &'a Foo, x: &'b i32) -> &'a i32 {
    if true {
        let p: &i32 = &a.field;
        &*p
    } else {
        &*x
    }
}

fn main() { }

I imagine this will exercise the "different lifetimes" code a bit.

arielb1 · 2017-09-19T20:46:43Z

You have a tidy error:

[00:03:51] tidy error: /checkout/src/test/ui/lifetime-errors/42701_one_named_and_one_anonymous.rs:12: trailing whitespace

arielb1 · 2017-09-26T17:02:24Z

This PR is basically ready to land, you just have to fix the tidy error. Just a ping to make sure this isn't getting lost.

cengiz-io · 2017-09-26T19:40:41Z

Hello @arielb1

Thanks for notifying. I'm still trying to resolve this example case #44167 (comment)

Whenever that finishes, I'll fix tidy error and push them.

cengiz-io · 2017-09-26T22:11:42Z

Just fixed tidy error.

Also, while rebasing, it turned out to change 3 ui tests. I'm not sure about this because it was an implicit change. 314bb98

@nikomatsakis maybe can shed some light to this implicit change

cengiz-io · 2017-09-27T05:55:34Z

There seems to be some changes which are breaking other tests also. Back to the drawing board...

nikomatsakis · 2017-09-27T21:44:06Z

@cengizio those 3 ui tests appear to be bug fixes =) that is, thanks to your change, the 'new and improved' errors are triggering more often. seems good!

nikomatsakis · 2017-09-27T21:51:36Z

@cengizio also those test errors are not unexpected. I think you just have to update the tests to change them to expect the new error message. However, these tests are a bit surprising to me:

object-lifetime-default-from-box-error.rs
issue-40288-2.rs

I'm not sure what's up with those two cases!

cengiz-io · 2017-10-02T23:00:03Z

@nikomatsakis update-references.sh doesn't help much on compile-fail tests (there's a bash issue but even solving that didn't work out) so I'm updating them manually.

I will also check those two surprising cases and report here.
Thank you!

nikomatsakis · 2017-10-03T10:50:44Z

@cengizio yes, compile-fail tests have to be edited manually.

cengiz-io · 2017-10-08T16:53:23Z

@nikomatsakis @arielb1 @gaurikholkar hello again!

I've updated the test cases.

NOTE: I decided to make test assertions in compile-fail tests as specific as possible. Please let me know if that's not the general case.

gaurikholkar-zz · 2017-10-08T20:26:22Z

@cengizio this test fails
src/test/compile-fail/associated-types/cache/project-fn-ret-invariant.rs

[01:00:24]     Error {
[01:00:24]         line_num: 50,
[01:00:24]         kind: Some(
[01:00:24]             Error
[01:00:24]         ),
[01:00:24]         msg: "50:5: 50:6: lifetime mismatch [E0623]"
[01:00:24]     }
[01:00:24] ]
[01:00:24]

I guess you have given the wrong column no for the error

cengiz-io · 2017-10-08T20:36:56Z

@gaurikholkar thanks for noticing. The annoying part is, all tests are passing on my local machine. (with latest HEAD).

Let's see if this fixes the problem.

cengiz-io · 2017-10-08T22:32:10Z

Argh! There seems to be line differences between my git clone and travis' copy. I'll investigate this further tomorrow.

gaurikholkar-zz · 2017-10-09T04:37:33Z

gaurikholkar-zz@cb0d746
Maybe this should work

gaurikholkar-zz · 2017-10-09T11:29:51Z

Ignore the indentation mess

bors · 2017-11-09T06:34:17Z

☀️ Test successful - status-travis
State: approved= try=True

kennytm · 2017-11-09T06:36:25Z

@rust-lang/infra Perf check wanted (44a477ee0833eef8007499fec6ebd88c5289da8a).

nikomatsakis · 2017-11-10T11:16:35Z

Looks like try build is ready. cc @rust-lang/infra

Mark-Simulacrum · 2017-11-11T18:46:16Z

http://perf.rust-lang.org/compare.html?start=fc77b623d3072005f35e320e652f2b31695d493c&end=44a477ee0833eef8007499fec6ebd88c5289da8a&stat=instructions%3Au

nikomatsakis · 2017-11-11T19:30:20Z

OK so -- the perf results seem fine, but @cengizio and I were discussing that maybe it's still worth replacing the BTreeMap with a Vec and a FxHashSet for duplicate checking. That would achieve the same results and seems better.

nikomatsakis · 2017-11-12T12:59:03Z

@arielb1 and I were talking. We think we'll r+ this PR and then do any perf experiments in follow-up work.

@bors r+

bors · 2017-11-12T12:59:04Z

📌 Commit dad7d94 has been approved by nikomatsakis

bors · 2017-11-12T14:42:10Z

⌛ Testing commit dad7d94 with merge 5b1b7b6c84a3e8e723a0416485a228abf756918c...

bors · 2017-11-12T15:38:09Z

💔 Test failed - status-travis

…rameter #42701

nikomatsakis · 2017-11-12T19:13:59Z

@bors r+

bors · 2017-11-12T19:13:59Z

📌 Commit f53fc57 has been approved by nikomatsakis

bors · 2017-11-12T21:04:46Z

⌛ Testing commit f53fc57 with merge 79cfce3...

Improve SubSupConflict with a named and an anonymous lifetime parameter #42701 Hello! This fixes #42701. ## UPDATE 01 Tests are producing different results between different env builds. This inconsistency might take a long time to investigate and fix. So, be patient ## UPDATE 02 Changed an `FxHashMap` with a `BTreeMap`. Inconsistency seems to be resolved for now.

bors · 2017-11-12T23:31:53Z

☀️ Test successful - status-appveyor, status-travis
Approved by: nikomatsakis
Pushing 79cfce3 to master...

rust-highfive assigned pnkfelix Aug 29, 2017

gaurikholkar-zz suggested changes Aug 30, 2017

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gaurikholkar-zz reviewed Aug 30, 2017

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rust-highfive assigned nikomatsakis and unassigned pnkfelix Aug 30, 2017

aidanhs added the S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. label Aug 31, 2017

nikomatsakis approved these changes Oct 9, 2017

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nikomatsakis approved these changes Nov 11, 2017

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kennytm added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Nov 12, 2017

nikomatsakis mentioned this pull request Nov 12, 2017

Simplify higher-ranked LUB/GLB #45853

Merged

cengiz-io added 7 commits November 12, 2017 18:56

Improve SubSupConflict case with one named, one anonymous lifetime pa…

da52563

…rameter #42701

Update fn-ret-invariant test assertion

ee839b3

use BTreeMap for region constraints

501c558

update failing E0621 tests

090669d

add reasons of using BTreeMap to a comment

5aac7a5

remove trailing whitespace from comment block

1719971

update project-fn-test-invariant test

f53fc57

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 Nov 12, 2017

bors merged commit f53fc57 into rust-lang:master Nov 12, 2017

bors mentioned this pull request Nov 12, 2017

Various refactorings towards universe-based regions #45657

Closed

		@@ -0,0 +1,41 @@
		error[E0495]: cannot infer an appropriate lifetime for borrow expression due to conflicting requirements

		@@ -0,0 +1,24 @@
		// Copyright 2017 The Rust Project Developers. See the COPYRIGHT

Improve SubSupConflict with a named and an anonymous lifetime parameter #42701 #44167

Improve SubSupConflict with a named and an anonymous lifetime parameter #42701 #44167

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