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improve error message on attempt to impl on type alias #39249
Description
As seen previously in #9767, messaging when attempting to impl a trait involving a type alias could be improved (using current nightly):
error[E0117]: only traits defined in the current crate can be implemented for arbitrary types
--> manifest/mod.rs:169:1
|
169 | impl<'a> FromIterator<io::Result<String>> for Result<Manifest<'a>> {
| _^ starting here...
170 | | fn from_iter<I: IntoIterator<Item = io::Result<String>>>(iter: I) -> Result<Self> {
171 | | let mut m = Manifest::new();
172 | | Ok(m)
173 | | }
174 | | }
| |_^ ...ending here: impl doesn't use types inside crate
|
= note: the impl does not reference any types defined in this crate
From line 86 of that file:
pub type Result<Manifest> = ::std::result::Result<Manifest, ManifestError>;I had expected to see = note: define and implement a trait or new type instead as described in #9767, but did not, so perhaps this is a regression or a subtly different case?
As someone relatively new to rust, it seems like I should be able to impl in this case since it is specialized such that it's only for a Result using my types, but I guess not.
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durka commentedon Jan 23, 2017
Looks like we could just duplicate this line to here?