rust-lang / rust-lang/reference
Document when associated types may be omitted from dyn Trait type
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Description
We accept this,
pub trait Tr {
type Ty;
}
fn f(_: &dyn Tr<Ty = ()>) {}
and we accept this (as of https://github.com/rust-lang/rust/pull/112319),
pub trait Tr {
type Ty where Self: Sized;
}
fn f(_: &dyn Tr) {}
but we of course don't accept this:
pub trait Tr {
type Ty;
}
fn f(_: &dyn Tr) {} //~ ERROR
The Reference should speak to this in our chapter on trait object types, but is silent on this matter.
cc @ehuss https://github.com/rust-lang/reference/issues/1932 https://github.com/rust-lang/rust/issues/127251
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 Reference's trait object types chapter linked in the issue and compare its current wording with the three Rust examples. Document when associated types may be omitted, including the Self: Sized case, and explain the rejected form. Done means the chapter clearly covers all shown cases.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- rust
- Domain
- documentation
- Issue type
- Documentation
- Difficulty
- 2/5
- Estimated time
- 1-3 hours
- Activity status
- Stale
- Clarity
- Clearly specified
- Newbie friendliness
- 68/100