Rework trait parameter patterns #1771
Merged
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
rustbot
added
the
S-waiting-on-review
traviscross
reviewed
Apr 1, 2025
Comment on lines
+336
to
+353
| 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]. |
There was a problem hiding this comment.
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.
traviscross
reviewed
Apr 1, 2025
src/items/traits.md
Outdated
| * `&&` [IDENTIFIER] | ||
| ```rust,compile_fail,E0642 | ||
| trait T { | ||
| fn f2(&x: &i32); // ERROR: Patterns aren't allowed in functions without bodies |
There was a problem hiding this comment.
This should be lowercased to match the others. I'll fix.
traviscross
force-pushed
the
trait-pattern-edition-rework
branch
from
e9890c7 to
a319552
Compare
traviscross
reviewed
Apr 1, 2025
src/items/traits.md
Outdated
| > ```rust,edition2015 | ||
| > // 2015 Edition | ||
| > trait T { | ||
| > fn f(i32); // Parameter identifiers are not required. |
There was a problem hiding this comment.
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.
traviscross
force-pushed
the
trait-pattern-edition-rework
branch
from
a319552 to
7cdad30
Compare
traviscross
approved these changes
Apr 1, 2025
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
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: