non_local_definitions common issues: impl for &Local, From<Local> for Global, ... (original) (raw)
I wonder whether the following code should be triggering non_local_definitions. It currently does and I think it's a bug:
pub trait Trait {}
fn main() { struct Thing; impl Trait for &Thing {} }
warning: non-local impl definition, they should be avoided as they go against expectation
--> src/main.rs:5:5
|
5 | impl Trait for &Thing {}
| ^^^^^^^^^^^^^^^^^^^^^^^^
|
= help: move this impl block outside the of the current function main
= note: an impl definition is non-local if it is nested inside an item and neither the type nor the trait are at the same nesting level as the impl block
= note: one exception to the rule are anon-const (const _: () = { ... }) at top-level module and anon-const at the same nesting as the trait or type
= note: this lint may become deny-by-default in the edition 2024 and higher, see the tracking issue https://github.com/rust-lang/rust/issues/120363
= note: #[warn(non_local_definitions)] on by default
A real-world occurrence can be seen in https://github.com/serde-rs/json/blob/e1b3a6d8a161ff5ec4865b487d148c17d0188e3e/tests/test.rs#L2334-L2346.
In general #[fundamental] exists to allow what would otherwise be a coherence violation, and it would make sense for the same exception to be applied here for the non_local_definitions lint.