Rustc misunderstands when an @ is missing in a pattern and the error message is confusing #88404
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A-diagnostics
Area: Messages for errors, warnings, and lints
A-patterns
Relating to patterns and pattern matching
A-slice-patterns
Area: Slice patterns, https://github.com/rust-lang/rust/issues/23121
A-suggestion-diagnostics
Area: Suggestions generated by the compiler applied by `cargo fix`
C-enhancement
Category: An issue proposing an enhancement or a PR with one.
D-confusing
Diagnostics: Confusing error or lint that should be reworked.
T-compiler
Relevant to the compiler team, which will review and decide on the PR/issue.
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A-diagnostics
matthiaskrgr
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Nov 17, 2023
On resolve error of `[rest..]`, suggest `[rest @ ..]`
When writing a pattern to collect multiple entries of a slice in a single binding, it is easy to misremember or typo the appropriate syntax to do so, instead writing the experimental `X..` pattern syntax. When we encounter a resolve error because `X` isn't available, we suggest `X @ ..` as an alternative.
```
error[E0425]: cannot find value `rest` in this scope
--> $DIR/range-pattern-meant-to-be-slice-rest-pattern.rs:3:13
|
LL | [1, rest..] => println!("{rest:?}"),
| ^^^^ not found in this scope
|
help: if you meant to collect the rest of the slice in `rest`, use the at operator
|
LL | [1, rest @ ..] => println!("{rest:?}"),
| +
```
Fix rust-lang#88404.
rust-timer
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Nov 17, 2023
Rollup merge of rust-lang#117998 - estebank:issue-88404, r=TaKO8Ki On resolve error of `[rest..]`, suggest `[rest @ ..]` When writing a pattern to collect multiple entries of a slice in a single binding, it is easy to misremember or typo the appropriate syntax to do so, instead writing the experimental `X..` pattern syntax. When we encounter a resolve error because `X` isn't available, we suggest `X @ ..` as an alternative. ``` error[E0425]: cannot find value `rest` in this scope --> $DIR/range-pattern-meant-to-be-slice-rest-pattern.rs:3:13 | LL | [1, rest..] => println!("{rest:?}"), | ^^^^ not found in this scope | help: if you meant to collect the rest of the slice in `rest`, use the at operator | LL | [1, rest @ ..] => println!("{rest:?}"), | + ``` Fix rust-lang#88404.
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I should have typed
rest @ .., and to fix my problem I need to add the@betweenrestand..Instead rustc tries to tell me three different ways that "rest.." is wrong, none of which are "hey did you forget the @ sign?"
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