Rework trait parameter patterns #1771
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| r[items.traits.params.restriction-patterns.edition2018] | ||
| > [!EDITION-2018] | ||
| > Prior to the 2018 edition, parameters in associated functions with a body are limited to the following kinds of patterns: | ||
| > | ||
| > * [IDENTIFIER] | ||
| > * `mut` [IDENTIFIER] | ||
| > * [`_`][WildcardPattern] | ||
| > * `&` [IDENTIFIER] | ||
| > * `&&` [IDENTIFIER] | ||
| > | ||
| > ```rust,edition2015,compile_fail,E0642 | ||
| > // 2015 Edition | ||
| > trait T { | ||
| > fn f1((a, b): (i32, i32)) {} // ERROR: pattern not allowed | ||
| > } | ||
| > ``` | ||
| > | ||
| > Beginning in 2018, all irrefutable patterns are allowed as described in [items.traits.params.patterns-with-body]. |
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It's a thought for another PR, but I wonder whether it'd be useful for us to link from these edition differences blocks to the relevant chapter of the edition guide.
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| * `&&` [IDENTIFIER] | ||
| ```rust,compile_fail,E0642 | ||
| trait T { | ||
| fn f2(&x: &i32); // ERROR: Patterns aren't allowed in functions without bodies |
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This should be lowercased to match the others. I'll fix.
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| > ```rust,edition2015 | ||
| > // 2015 Edition | ||
| > trait T { | ||
| > fn f(i32); // Parameter identifiers are not required. |
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Other things here are going with the // OK: .. pattern, so I'll edit to match that.
This updates the description of trait parameter patterns, primarily to shift it to the style where the main text describes the behavior in the current edition, and changes in the edition are moved to separate edition blocks. The specific changes: - Rework the edition presentation (as per our style guide). - Try to use more consistent wording. - Add examples. - Rename some of the rules to switch to the updated edition style, and try to be a little clearer about their intent. - Change the way it refers to "methods". The reference used to define methods as a separate kind of associated item, but we changed it so that functions allow an optional _SelfParam_, and methods aren't as special as they used to be. This text was still written assuming the previous presentation.
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Update books ## rust-lang/reference 12 commits in e95ebdfee02514d93f79ec92ae310a804e87f01f..46435cd4eba11b66acaa42c01da5c80ad88aee4b 2025-04-07 14:21:21 UTC to 2025-03-25 20:13:17 UTC - Update book.toml fix the authors field (rust-lang/reference#1780) - Update precedence table for borrow operators (rust-lang/reference#1776) - Add the ability for rules to be specified in link definitions (rust-lang/reference#1775) - Rework trait parameter patterns (rust-lang/reference#1771) - Fix header rules (rust-lang/reference#1770) - Add test wrappers (rust-lang/reference#1774) - Update tools to Rust 2024 (rust-lang/reference#1773) - Define byte (rust-lang/reference#1772) - Fix CSS for new footnote style (rust-lang/reference#1777) - do not reference LLVM in our definition of UB (rust-lang/reference#1750) - Tweak reference for precise capturing in traits (rust-lang/reference#1769) - Add edition admonitions (rust-lang/reference#1764) ## rust-lang/rust-by-example 2 commits in 6f69823c28ae8d929d6c815181c73d3e99ef16d3..0d7964d5b22cf920237ef1282d869564b4883b88 2025-04-07 11:19:31 UTC to 2025-03-29 02:25:52 UTC - Rename count to index for clarity (rust-lang/rust-by-example#1920) - Fixing grammar in panic section (rust-lang/rust-by-example#1916)
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Update books ## rust-lang/reference 12 commits in e95ebdfee02514d93f79ec92ae310a804e87f01f..46435cd4eba11b66acaa42c01da5c80ad88aee4b 2025-04-07 14:21:21 UTC to 2025-03-25 20:13:17 UTC - Update book.toml fix the authors field (rust-lang/reference#1780) - Update precedence table for borrow operators (rust-lang/reference#1776) - Add the ability for rules to be specified in link definitions (rust-lang/reference#1775) - Rework trait parameter patterns (rust-lang/reference#1771) - Fix header rules (rust-lang/reference#1770) - Add test wrappers (rust-lang/reference#1774) - Update tools to Rust 2024 (rust-lang/reference#1773) - Define byte (rust-lang/reference#1772) - Fix CSS for new footnote style (rust-lang/reference#1777) - do not reference LLVM in our definition of UB (rust-lang/reference#1750) - Tweak reference for precise capturing in traits (rust-lang/reference#1769) - Add edition admonitions (rust-lang/reference#1764) ## rust-lang/rust-by-example 2 commits in 6f69823c28ae8d929d6c815181c73d3e99ef16d3..0d7964d5b22cf920237ef1282d869564b4883b88 2025-04-07 11:19:31 UTC to 2025-03-29 02:25:52 UTC - Rename count to index for clarity (rust-lang/rust-by-example#1920) - Fixing grammar in panic section (rust-lang/rust-by-example#1916)
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Rollup merge of rust-lang#139491 - rustbot:docs-update, r=ehuss Update books ## rust-lang/reference 12 commits in e95ebdfee02514d93f79ec92ae310a804e87f01f..46435cd4eba11b66acaa42c01da5c80ad88aee4b 2025-04-07 14:21:21 UTC to 2025-03-25 20:13:17 UTC - Update book.toml fix the authors field (rust-lang/reference#1780) - Update precedence table for borrow operators (rust-lang/reference#1776) - Add the ability for rules to be specified in link definitions (rust-lang/reference#1775) - Rework trait parameter patterns (rust-lang/reference#1771) - Fix header rules (rust-lang/reference#1770) - Add test wrappers (rust-lang/reference#1774) - Update tools to Rust 2024 (rust-lang/reference#1773) - Define byte (rust-lang/reference#1772) - Fix CSS for new footnote style (rust-lang/reference#1777) - do not reference LLVM in our definition of UB (rust-lang/reference#1750) - Tweak reference for precise capturing in traits (rust-lang/reference#1769) - Add edition admonitions (rust-lang/reference#1764) ## rust-lang/rust-by-example 2 commits in 6f69823c28ae8d929d6c815181c73d3e99ef16d3..0d7964d5b22cf920237ef1282d869564b4883b88 2025-04-07 11:19:31 UTC to 2025-03-29 02:25:52 UTC - Rename count to index for clarity (rust-lang/rust-by-example#1920) - Fixing grammar in panic section (rust-lang/rust-by-example#1916)
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This updates the description of trait parameter patterns, primarily to shift it to the style where the main text describes the behavior in the current edition, and changes in the edition are moved to separate edition blocks.
The specific changes: