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On irrefutable let pattern lint point only at pattern #81366

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On irrefutable let pattern lint point only at pattern #81366

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estebank
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Add Span to let desugaring MatchSource variants to point only at
the let pattern when linting against irrefutable patterns in if let
and while let.

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r? @matthewjasper

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@rust-highfive rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Jan 25, 2021
camelid
camelid reviewed Jan 25, 2021
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src/test/ui/consts/const_limit/const_eval_limit_reached.stderr Outdated
Comment on lines 4 to 12
LL | / const X: usize = {
LL | | let mut x = 0;
LL | | while x != 1000 {
| |_____^
LL | ||
LL | || x += 1;
LL | || }
| ||_____^ exceeded interpreter step limit (see `#[const_eval_limit]`)
LL | |
LL | | x
LL | | };
| |__-
LL | / const X: usize = {
LL | | let mut x = 0;
LL | | while x != 1000 {
| | ^^^^^^^^^ exceeded interpreter step limit (see `#[const_eval_limit]`)
LL | |
... |
LL | | x
LL | | };
| |__-
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This feels like a regression :/

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Reverted this change.

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It looked fine to me. The span got more precise, so that was good. The interpreter spans never were very good around the resource limits

src/test/ui/pattern/usefulness/deny-irrefutable-let-patterns.stderr Outdated Show resolved Hide resolved
src/test/ui/while-let.stderr Outdated
Comment on lines 18 to 19
LL | while let $p = $e $b
| ^^^^^^^^^^^^^^^^^^^^
| ^^^
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This doesn't look right.

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Spans involving macros are sometimes less than ideal :-/

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camelid commented Jan 25, 2021 •
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Can you also do this for if-let guards? (Unless they do this already, I forget 😄)

@camelid camelid added the A-diagnostics Area: Messages for errors, warnings, and lints label Jan 25, 2021
@estebank estebank force-pushed the if-let-pattern branch 2 times, most recently from cd71894 to b1fb8a7 Compare January 25, 2021 03:19
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estebank commented Jan 25, 2021 •
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Can you also do this for if-let guards?

I'll check, but I think those are handled elsewhere.

Edit: for the if let guard case we point at only the pattern, which isn't terrible, but I'll add the correct span for them to be consistent.

Edit: Done.

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bors commented Feb 18, 2021

☔ The latest upstream changes (presumably #81993) made this pull request unmergeable. Please resolve the merge conflicts.

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r? @oli-obk

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@estebank
On irrefutable let pattern lint point only at pattern
cc85d1f 
Add `Span` to let desugaring `MatchSource` variants to point only at
the `let` pattern when linting against irrefutable patterns in `if let`
and `while let`.
@estebank
Point at whole let guard on irrefutable let pattern
5b7c07d
@estebank
Add more detail to irrefutable let pattern lint
9fe2500
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Heads up, @rust-lang/clippy. Small changes incoming that would break clippy with fixes in the same PR.

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Seems fine, we have an easy sync process now

oli-obk
oli-obk reviewed Feb 26, 2021
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I feel like I'm missing something fundamental. Where do the spans that encompass entire if let or while let expressions come from? To me it seems that you replaced a lot of (or only?) arm.pat.spans with let_spans, which has some regressions, but also some improvements in situations that seem indistinguishable (to me) from situations that were good before. So...

  • Are there some pat.spans that refer to the entire match?
  • Do these point to the entire match only after compute_match_usefulness
  • Do these point to the entire match already during lowering?

I think we should first find out where these bad spans come from and if we can address them at the source instead of tracking additional spans.

compiler/rustc_mir_build/src/thir/pattern/check_match.rs
diag.help("consider instead using a `loop { ... }` with a `let` inside it");
diag
}
hir::MatchSource::IfLetGuardDesugar { .. }=> {
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Suggested change
hir::MatchSource::IfLetGuardDesugar { .. }=> {
hir::MatchSource::IfLetGuardDesugar { .. } => {

not sure why rustfmt didn't catch this

src/test/ui/uninhabited/uninhabited-patterns.stderr
Comment on lines 34 to +35
LL | while let Some(_y) = foo() {
| ^^^^^^^^
| ^^^^^^^^^^^^^^^^^^^^
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This is a regression. That refutable let binding is not a pattern, the previous span was pointing to a pattern.

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bors commented Mar 9, 2021

☔ The latest upstream changes (presumably #82911) made this pull request unmergeable. Please resolve the merge conflicts.

@camelid camelid 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 Mar 25, 2021
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@estebank this is waiting for you to resolve conflicts + reply to the above review. Thanks

@JohnCSimon JohnCSimon 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-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Apr 12, 2021
@camelid camelid 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-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Apr 30, 2021
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Ping again from triage:
@estebank this is waiting for you to resolve conflicts + reply to the above review. Thanks

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This heavily collides with #80357 to a point where it has probably be redone once that is merged.

@crlf0710 crlf0710 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-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Jun 5, 2021
@JohnCSimon JohnCSimon 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-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Jun 22, 2021
@JohnCSimon JohnCSimon added the S-blocked Status: Marked as blocked ❌ on something else such as an RFC or other implementation work. label Jul 6, 2021
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Blocked on #80357

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oli-obk commented Jul 18, 2021

This heavily collides with #80357 to a point where it has probably be redone once that is merged.

needs a rewrite, closing

@oli-obk oli-obk closed this Jul 18, 2021
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