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Spurious additional lifetime appearing in printout of type involving HRT lifetimes #102392

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steffahn opened this issue Sep 28, 2022 · 4 comments · Fixed by #102514
Closed

Spurious additional lifetime appearing in printout of type involving HRT lifetimes #102392

steffahn opened this issue Sep 28, 2022 · 4 comments · Fixed by #102514
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A-diagnostics Area: Messages for errors, warnings, and lints P-low Low priority regression-from-stable-to-stable Performance or correctness regression from one stable version to another. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue.

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@steffahn
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steffahn commented Sep 28, 2022 •
edited

“Related” to #102346, and #101280, as this, too, is about diagnostic printing of types with HRT lifetimes (unlike the former related issue, this issue is not a recent regression):

fn g(f: for<'a> fn(fn(&str, &'a str))) -> bool {
    f
}
error[E0308]: mismatched types
 --> src/lib.rs:2:5
  |
1 | fn g(f: for<'a> fn(fn(&str, &'a str))) -> bool {
  |                                           ---- expected `bool` because of return type
2 |     f
  |     ^ expected `bool`, found fn pointer
  |
  = note:    expected type `bool`
          found fn pointer `for<'a> fn(for<'b, 'a> fn(&'b str, &'a str))`

The way this type is displayed includes an additional superflous/confusing/wrong quantification of 'a in the inner for. Correct would be for<'a> fn(for<'b> fn(&'b str, &'a str)), not for<'a> fn(for<'b, 'a> fn(&'b str, &'a str)).

cc @b-naber who is currently working on the above-mentioned “related” issues.

@rustbot label regression-from-stable-to-stable, E-needs-bisection

Regresses between 1.54 and 1.55:

1.54

  = note:    expected type `bool`
          found fn pointer `for<'a> fn(for<'r> fn(&'r str, &'a str))`

1.55

  = note:    expected type `bool`
          found fn pointer `for<'a> fn(for<'r, 'a> fn(&'r str, &'a str))`
@steffahn steffahn added A-diagnostics Area: Messages for errors, warnings, and lints T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Sep 28, 2022
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rustbot commented Sep 28, 2022

Error: Label needs-bisection can only be set by Rust team members

Please file an issue on GitHub at triagebot if there's a problem with this bot, or reach out on #t-infra on Zulip.

@rustbot rustbot added E-needs-bisection Call for participation: This issue needs bisection: https://github.com/rust-lang/cargo-bisect-rustc regression-from-stable-to-stable Performance or correctness regression from one stable version to another. I-prioritize Issue: Indicates that prioritization has been requested for this issue. labels Sep 28, 2022
@apiraino
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WG-prioritization assigning priority (Zulip discussion).

@rustbot label -I-prioritize +P-low

@rustbot rustbot added P-low Low priority and removed I-prioritize Issue: Indicates that prioritization has been requested for this issue. labels Sep 28, 2022
@apiraino
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apiraino commented Sep 28, 2022 •
edited

Bisection seems to indicate this group of PRs in the range --start 2021-07-01 --end 2021-12-01.

********************************************************************************
Regression in nightly-2021-07-23
********************************************************************************

  commit[0] 2021-07-21UTC: Auto merge of #87351 - ehuss:rollup-pga85az, r=ehuss
  commit[1] 2021-07-21UTC: Auto merge of #86946 - Aaron1011:eval-proj-obligation, r=nikomatsakis
  commit[2] 2021-07-22UTC: Auto merge of #87246 - rust-lang:placeholder-pretty, r=nikomatsakis
  commit[3] 2021-07-22UTC: Auto merge of #87250 - robojumper:87199-sized-relaxation, r=nikomatsakis
  commit[4] 2021-07-22UTC: Auto merge of #87265 - Aaron1011:hir-wf-fn, r=estebank
  commit[5] 2021-07-22UTC: Auto merge of #86619 - rylev:incr-hashing-profiling, r=wesleywiser
  commit[6] 2021-07-22UTC: Auto merge of #87366 - GuillaumeGomez:rollup-7muueab, r=GuillaumeGomez
  commit[7] 2021-07-22UTC: Auto merge of #87371 - ehuss:update-cargo, r=ehuss
  commit[8] 2021-07-22UTC: Auto merge of #86212 - pnkfelix:mainline-targetted-revert-81473-warn-write-only-fields, r=simulacrum

but due to the age I could not pinpoint a specific nightly.

Also, as pointed out in the previous comment at some point the diagnostic changed and decided to use another wording (for<'a> fn(for<'b, 'a> fn(&'b str, &'a str))) which I wonder if it's related to one of the mentioned other 2 issues

@rustbot label -E-needs-bisection

@rustbot rustbot removed the E-needs-bisection Call for participation: This issue needs bisection: https://github.com/rust-lang/cargo-bisect-rustc label Sep 28, 2022
@steffahn
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Looking through this list, #87246 seems likely.

@b-naber b-naber mentioned this issue Sep 30, 2022
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matthiaskrgr added a commit to matthiaskrgr/rust that referenced this issue Oct 8, 2022
@matthiaskrgr
Rollup merge of rust-lang#102514 - b-naber:binder-print-fixes, r=jack…
fa186e4 
…h726

Don't repeat lifetime names from outer binder in print

Fixes rust-lang#102392
Fixes rust-lang#102414

r? `@lcnr`
matthiaskrgr added a commit to matthiaskrgr/rust that referenced this issue Oct 8, 2022
@matthiaskrgr
Rollup merge of rust-lang#102514 - b-naber:binder-print-fixes, r=jack…
dd81098 
…h726

Don't repeat lifetime names from outer binder in print

Fixes rust-lang#102392
Fixes rust-lang#102414

r? ``@lcnr``
@bors bors closed this as completed in 5ba30a6 Oct 9, 2022
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Don't repeat lifetime names from outer binder in print b-naber/rust
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