Open
Description
Code
fn test() -> Option<impl Fn(&String)> {
if false {
return None;
}
Some(|_| {})
}Current output
error: implementation of `Fn` is not general enough
--> src/lib.rs:3:16
|
3 | return None;
| ^^^^ implementation of `Fn` is not general enough
|
= note: closure with signature `fn(&'2 String)` must implement `Fn<(&'1 String,)>`, for any lifetime `'1`...
= note: ...but it actually implements `Fn<(&'2 String,)>`, for some specific lifetime `'2`
error: implementation of `FnOnce` is not general enough
--> src/lib.rs:3:16
|
3 | return None;
| ^^^^ implementation of `FnOnce` is not general enough
|
= note: closure with signature `fn(&'2 String)` must implement `FnOnce<(&'1 String,)>`, for any lifetime `'1`...
= note: ...but it actually implements `FnOnce<(&'2 String,)>`, for some specific lifetime `'2`
error: implementation of `Fn` is not general enough
--> src/lib.rs:5:5
|
5 | Some(|_| {})
| ^^^^^^^^^^^^ implementation of `Fn` is not general enough
|
= note: closure with signature `fn(&'0 String)` must implement `Fn<(&String,)>`, for some specific lifetime `'0`...
= note: ...but it actually implements `Fn<(&'1 String,)>`, for some specific lifetime `'1`
error: could not compile `playground` (lib) due to 3 previous errors
Desired output
I think ideally there would only be an error pointing at the actual closure and not None.
Rationale and extra context
It's made worse that there are two errors on None so the "good" error is buried further.
A broader issue is that this doesn't compile in the first place.
Other cases
Rust Version
1.88.0Anything else?
No response
Metadata
Metadata
Assignees
Labels
Area: The borrow checkerArea: Messages for errors, warnings, and lintsArea: Higher-ranked things (e.g., lifetimes, types, trait bounds aka HRTBs)Diagnostics: spans don't point to exactly the erroneous codeDiagnostics: Too much output caused by a single piece of incorrect code.Relevant to the compiler team, which will review and decide on the PR/issue.