Improve suggestion for tuple struct pattern matching errors. #81235
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Currently, when a user uses a struct pattern to pattern match on a tuple struct, the errors we emit generally suggest adding fields using their field names, which are numbers. However, numbers are not valid identifiers, so the suggestions, which use the shorthand notation, are not valid syntax. This commit changes those errors to suggest using the actual tuple struct pattern syntax instead, which is a more actionable suggestion.
| match self.tcx.sess.source_map().span_to_snippet(field.pat.span) { | ||
| Ok(f) => { | ||
| // Field names are numbers, but numbers | ||
| // are not valid identifiers | ||
| if variant_field_idents.contains(&field.ident) { | ||
| String::from("_") | ||
| } else { | ||
| f | ||
| } | ||
| } | ||
| Err(_) => rustc_hir_pretty::to_string(rustc_hir_pretty::NO_ANN, |s| { | ||
| s.print_pat(field.pat) | ||
| }), | ||
| } |
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This code is fair (as you're just copying from existing logic), but ideally we would not be using span_to_snippet here. (No need to change this now.)
| LL | if let S { a, b, c, d } = S(1, 2, 3, 4) { | ||
| | ^^^^^^^^^^^^^^^^ help: use the tuple variant pattern syntax instead: `S(a, b, c, d)` | ||
| | -^^^^^^^^^^^^^^^ | ||
| | | | ||
| | help: use the tuple variant pattern syntax instead: `(a, b, c, d)` |
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The span in all of the tests' suggestions seems to now be wrong. The resulting code would be (a, b, c, d) instead of the desired S(a, b, c, d).
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The suggestion here seemed like you were suggesting to remove the path from the help text. It seems like I misunderstood the intent there, what were you suggesting to use instead of the path?
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My proposal is to use span_suggestion_verbose to have a separate suggestion subwindow, but for the suggestion to be correctly displayed you need to make a span trimming the S from the beginning. The suggestion has to have the correct span for it to be rendered correctly.
In the case highlighted above, you had a span pointing at S { a, b, c, d }. You now have a span pointing at S. Creating a new span that starts at the end of S's span, you'll have a span pointing at { a, b, c, d } which would do then render correctly.
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Gotcha, having that suggestion with span_suggestion_verbose makes a lot of sense. Thanks for the clarification, still figuring out all the options for these diagnostics 😅
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@bors r+ |
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📌 Commit d8540ae has been approved by |
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Improve suggestion for tuple struct pattern matching errors. Closes rust-lang#80174 This change allows numbers to be parsed as field names when pattern matching on structs, which allows us to provide better error messages when tuple structs are matched using a struct pattern. r? `@estebank`
Rollup of 12 pull requests Successful merges: - rust-lang#79423 (Enable smart punctuation) - rust-lang#81154 (Improve design of `assert_len`) - rust-lang#81235 (Improve suggestion for tuple struct pattern matching errors.) - rust-lang#81769 (Suggest `return`ing tail expressions that match return type) - rust-lang#81837 (Slight perf improvement on char::to_ascii_lowercase) - rust-lang#81969 (Avoid `cfg_if` in `std::os`) - rust-lang#81984 (Make WASI's `hard_link` behavior match other platforms.) - rust-lang#82091 (use PlaceRef abstractions more consistently) - rust-lang#82128 (add diagnostic items for OsString/PathBuf/Owned as well as to_vec on slice) - rust-lang#82166 (add s390x-unknown-linux-musl target) - rust-lang#82234 (Remove query parameters when skipping search results) - rust-lang#82255 (Make `treat_err_as_bug` Option<NonZeroUsize>) Failed merges: r? `@ghost` `@rustbot` modify labels: rollup
Closes #80174
This change allows numbers to be parsed as field names when pattern matching on structs, which allows us to provide better error messages when tuple structs are matched using a struct pattern.
r? @estebank