RFC: Trait Implementation Privacy with permits
#3903
Conversation
| Introduce a new syntax for restricting trait implementations to specific crates: | ||
|
|
||
| ```rust | ||
| trait Test permits mycrate_extra, crate { |
There was a problem hiding this comment.
how does the upstream trait declaration knows the name of the downstream crate name provide the impls? any crate can call themselves mycrate_extra, so this does not prevent "malicious impls" mentioned on line 21 at all
ehuss
added
T-lang
|
|
||
| Accidental or malicious impls: External crates can implement traits in ways that break invariants. | ||
|
|
||
| Audit difficulty: It is hard to know which crates are allowed to implement a trait. |
There was a problem hiding this comment.
It is generally very simple to work out how the Orphan Rule applies. The fundamental types work a little different, but there's only a handful of such types.
kennytm
changed the title
permits
|
|
||
| crate refers to the defining crate. | ||
|
|
||
| Other identifiers refer to external crates by name. |
There was a problem hiding this comment.
Is there a use for "I want this crate and a specific set of dependent crates named here to be the only crates who can implement this trait" restrictions? I can't think of any Rust code I've read/written where anything between "only this crate can implement" or "the whole world can implement" would be useful.
6 participants
Rendered