-
Notifications
You must be signed in to change notification settings - Fork 12.7k
New issue
Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.
By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.
Already on GitHub? Sign in to your account
Incomprehensible error message involving lifetimes adding extension methods to dyn Trait
#71341
Comments
Current output:
|
Minimized: trait OtherTrait<'a> {}
impl<'a> OtherTrait<'a> for &'a () {}
trait ObjectTrait {}
trait MyTrait {
fn use_self(&self) -> &();
}
impl MyTrait for dyn ObjectTrait {
fn use_self(&self) -> &() { panic!() }
}
fn use_it<'a>(val: &'a dyn ObjectTrait) -> impl OtherTrait<'a> + 'a {
val.use_self()
}
The very non-obvious fix is to change The issue here is that |
@Aaron1011 with #73783 applied: I would love it if we could have a more reliable way of addressing this, but at least it is a start. |
…time, r=nikomatsakis Detect when `'static` obligation might come from an `impl` Partly address rust-lang#71341.
…time, r=nikomatsakis Detect when `'static` obligation might come from an `impl` Partly address rust-lang#71341.
…time, r=nikomatsakis Detect when `'static` obligation might come from an `impl` Partly address rust-lang#71341.
Current output:
I think this ticket can be closed now, but for some reason I didn't with the PR (and I don't recall why). |
I agree, thanks for fixing this!!! |
I'm defining a trait that adds extension methods to
dyn <another-trait>
:Complete example: https://play.rust-lang.org/?version=stable&mode=debug&edition=2018&gist=9918f3c4541601415f65606b4bfa0790
Rust stable and nightly both give
This is confusing. Obviously, adding a lifetime parameter identical to one already present doesn't seem sensible. Furthermore there is no clue here indicating what the error actually is. I spent over an hour thrashing around and ended up with https://play.rust-lang.org/?version=stable&mode=debug&edition=2018&gist=fda63d48e1652dcfd0923002f723163c --- i.e. I need to add a lifetime bound to the
dyn
type I'm extending, not just the method(s) on the extension.I'm assuming that the compiler is correct here and it just needs a better error message. I'm not 100% sure about that though.
The text was updated successfully, but these errors were encountered: