Inspired by this question on discord:
no method named extend found for struct Map<std::iter::Chain<Map<Windows<'_, Point>, [closure@src\graphics\slider.rs:39:22: 47:18]>, std::iter::Once<Point>>, [closure@src\graphics\slider.rs:49:22: 49:60]> in the current scope
how does map not have .extend
Repro: https://play.rust-lang.org/?version=nightly&mode=debug&edition=2018&gist=e270ca9a0ae009a8f34af6bc31c0ce90
fn main() {
let v = vec![1_i32, 2, 3];
v.iter().map(|x| x * x).extend(std::iter::once(100));
}Error:
error[E0599]: no method named `extend` found for struct `Map<std::slice::Iter<'_, i32>, [closure@src/main.rs:3:18: 3:27]>` in the current scope
--> src/main.rs:3:29
|
3 | v.iter().map(|x| x * x).extend(std::iter::once(100));
| ^^^^^^ method not found in `Map<std::slice::Iter<'_, i32>, [closure@src/main.rs:3:18: 3:27]>`
It would be nice if rustc could notice that Map<T> never has extend for any T, and use that information to simplify the error message to just
error[E0599]: no method named `extend` found for struct `Map<_>` in the current scope
in order to focus the user better on the relevant part.
Can the name resolution engine do that? (It can for a generic parameter, of course, but then it's only looking at the known trait bounds, which is a little different.)
Inspired by this question on discord:
Repro: https://play.rust-lang.org/?version=nightly&mode=debug&edition=2018&gist=e270ca9a0ae009a8f34af6bc31c0ce90
Error:
It would be nice if rustc could notice that
Map<T>never hasextendfor anyT, and use that information to simplify the error message to justin order to focus the user better on the relevant part.
Can the name resolution engine do that? (It can for a generic parameter, of course, but then it's only looking at the known trait bounds, which is a little different.)