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Fix suggestion for removing &mut from &mut macro!(). #85939

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Merged
merged 2 commits into from
Jun 5, 2021
Merged

Fix suggestion for removing &mut from &mut macro!(). #85939

merged 2 commits into from
Jun 5, 2021

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m-ou-se
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@m-ou-se m-ou-se commented Jun 2, 2021

Fixes #85933

Before: (Note the suggestions.)

error[E0308]: mismatched types
 --> src/main.rs:2:21
  |
2 |     let _: String = &mut format!("");
  |            ------   ^^^^^^^^^^^^^^^^
  |            |        |
  |            |        expected struct `String`, found `&mut String`
  |            |        help: consider removing the borrow: `mut format!("")`
  |            expected due to this

error[E0308]: mismatched types
 --> src/main.rs:3:21
  |
3 |     let _: String = &mut (format!(""));
  |            ------   ^^^^^^^^^^^^^^^^^^
  |            |        |
  |            |        expected struct `String`, found `&mut String`
  |            |        help: consider removing the borrow: `mut (format!(""))`
  |            expected due to this

After:

error[E0308]: mismatched types
 --> src/main.rs:2:21
  |
2 |     let _: String = &mut format!("");
  |            ------   ^^^^^^^^^^^^^^^^
  |            |        |
  |            |        expected struct `String`, found `&mut String`
  |            |        help: consider removing the borrow: `format!("")`
  |            expected due to this

error[E0308]: mismatched types
 --> src/main.rs:3:21
  |
3 |     let _: String = &mut (format!(""));
  |            ------   ^^^^^^^^^^^^^^^^^^
  |            |        |
  |            |        expected struct `String`, found `&mut String`
  |            |        help: consider removing the borrow: `format!("")`
  |            expected due to this

@m-ou-se m-ou-se requested a review from estebank June 2, 2021 17:09
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r? @jackh726

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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 Jun 2, 2021
m-ou-se
m-ou-se commented Jun 2, 2021
View reviewed changes
compiler/rustc_typeck/src/check/demand.rs
// E.g. for `&format!("")`, where we want the span to the
// `format!()` invocation instead of its expansion.
if let Some(call_span) =
iter::successors(Some(expr.span), |s| s.parent()).find(|&s| sp.contains(s))
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@m-ou-se m-ou-se Jun 2, 2021 •
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@estebank What do you think about adding this as a function on Span (e.g. span.find_parent_within(span) or something)?

I have a feeling more diagnostics can/should use this, but I haven't written enough diagnostics yet to know if that's true.

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I agree with your assessment and we should have something like that (bikeshed notwithstanding).

m-ou-se
m-ou-se commented Jun 2, 2021
View reviewed changes
compiler/rustc_typeck/src/check/demand.rs
Comment on lines -585 to +593
src.to_string(),
code,
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In another diagnostic, I emitted (potentially multiple) suggestions for removing the parts that need to be removed, instead of a single suggestion that contains a copy of (part of) the original source. Is there a guideline for which to prefer?

Basically:
A. "replace &mut (format!("")) by format!("")
B. "remove &mut ( and remove )"

Most diagnostics seem to use A, which surprises me a bit. The suggestion for A can get quite large for large expressions.

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@estebank estebank Jun 3, 2021 •
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The later didn't exist until "recently" (2019?), so there's a historical component. There's also a bug that needs to be fixed on rustc's side to allow rustfix apply multipart suggestions, which it can't today.

Even with that caveat, I push for multipart suggestions in all new diagnostics when possible/necessary.

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Thanks!

There's also a bug that needs to be fixed on rustc's side to allow rustfix apply multipart suggestions, which it can't today.

That should be fixed by rust-lang/rustfix#195

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Awesome! That should also allow us to add a // run-rustfix to a bunch of tests that don't have it today because of that 😄

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estebank commented Jun 3, 2021

@bors r+, but feel free to change the suggestion to be multipart, if you so desire.

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estebank commented Jun 3, 2021

r? @estebank

@rust-highfive rust-highfive assigned estebank and unassigned jackh726 Jun 3, 2021
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m-ou-se commented Jun 4, 2021

@bors r+, but feel free to change the suggestion to be multipart, if you so desire.

Might do that in another PR. :)

Hm, looks like bors didn't understand r+,

@bors r=estebank

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bors commented Jun 4, 2021

📌 Commit ecebb66 has been approved by estebank

@bors bors 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-review Status: Awaiting review from the assignee but also interested parties. labels Jun 4, 2021
@JohnTitor JohnTitor mentioned this pull request Jun 4, 2021
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bors added a commit to rust-lang-ci/rust that referenced this pull request Jun 4, 2021
@bors
Auto merge of rust-lang#86006 - JohnTitor:rollup-97iuoi3, r=JohnTitor
704934d 
Rollup of 10 pull requests

Successful merges:

 - rust-lang#83653 (Remove unused code from `rustc_data_structures::sync`)
 - rust-lang#84466 (rustdoc: Remove `PrimitiveType::{to_url_str, as_str}`)
 - rust-lang#84880 (Make match in `register_res` easier to read)
 - rust-lang#84942 (rustdoc: link to stable/beta docs consistently in documentation)
 - rust-lang#85853 (Warn against boxed DST in `improper_ctypes_definitions` lint)
 - rust-lang#85939 (Fix suggestion for removing &mut from &mut macro!().)
 - rust-lang#85966 (wasm: Make simd types passed via indirection again)
 - rust-lang#85979 (don't suggest unsized indirection in where-clauses)
 - rust-lang#85983 (Update to semver 1.0.3)
 - rust-lang#85988 (Note that `ninja = false` goes under `[llvm]`)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup
@bors bors merged commit 5ebc4d3 into rust-lang:master Jun 5, 2021
@rustbot rustbot added this to the 1.54.0 milestone Jun 5, 2021
@m-ou-se m-ou-se deleted the fix-remove-ref-macro-invocation branch June 14, 2021 20:16
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@estebank estebank Awaiting requested review from estebank

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"consider removing the borrow" suggests to only remove & and not mut
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