rust-lang / rust-lang/reference
Page on structs implies that unit struct definition is the same as struct struct definition + named constant
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Description
From https://doc.rust-lang.org/reference/items/structs.html:
A unit-like struct is a struct without any fields, defined by leaving off the list of fields entirely. Such a struct implicitly defines a constant of its type with the same name. For example:
struct Cookie; let c = [Cookie, Cookie {}, Cookie, Cookie {}];is equivalent to
struct Cookie {} const Cookie: Cookie = Cookie {}; let c = [Cookie, Cookie {}, Cookie, Cookie {}];
Which seems to imply that a curly-brace struct / struct struct definition with no fields + a named constant of the same name is exactly the same thing as a unit struct definiton. However, this is not true when it comes to patterns: Cookie can be used as a pattern with the first declaration, but not with the second.
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Start with the unit-like structs section of the Rust Reference's structs page and compare its equivalence example with the pattern behavior described in the issue. Check the Rust language rules for unit-struct patterns and named constants; done means the page no longer implies the two declarations are interchangeable and accurately explains the distinction.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- rust
- Domain
- documentation
- Issue type
- Documentation
- Difficulty
- 3/5
- Estimated time
- 1-2 days
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 38/100