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author | bors[bot] <26634292+bors[bot]@users.noreply.github.com> | 2020-05-18 08:44:44 +0100 |
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committer | GitHub <[email protected]> | 2020-05-18 08:44:44 +0100 |
commit | ad03e4de185f0f19ae75a8a9c4095ee1b0d82a47 (patch) | |
tree | 86f1b44509075a54f0887d56fe84e8ae42df5766 /crates/ra_assists/src/handlers/add_derive.rs | |
parent | c6ed08967193cadc927dfaf422601bcd160a6fc9 (diff) | |
parent | 68db49c8534fa99768c7f600455ea76176f61994 (diff) |
Merge #4493
4493: Provide builtin impls of Fn traits for fn-pointers r=flodiebold a=hban
Meant to be, but isn't actually a fix for #2880.
Consider this snippet:
```rust
use std::marker::PhantomData;
use std::ops::Deref;
struct Lazy<T, F/* = fn() -> T*/>(F, PhantomData<T>);
impl<T, F> Lazy<T, F> {
pub fn new(f: F) -> Lazy<T, F> {
Lazy(f, PhantomData)
}
}
impl<T, F: FnOnce() -> T> Deref for Lazy<T, F> {
type Target = T;
fn deref(&self) -> &T { todo!() }
}
fn test() {
let lazy1: Lazy<u32, _> = Lazy::new(|| 0u32);
let r1 = lazy1.to_string();
fn make_u32_fn() -> u32 { todo!() }
let make_u32_fn_ptr: fn() -> u32 = make_u32_fn;
let lazy2: Lazy<u32, _> = Lazy::new(make_u32_fn_ptr);
let r2 = lazy2.to_string();
}
```
* On current master:
* When type default is commented-out, `r1` is correctly inferred, `r2` in _{unknown}_.
* When type default is not commented-out, both `r1` and `r2` are _{unknown}_.
* With this PR:
* When type default is commented-out, both `r1` and `r2` are correctly inferred.
* When type default is not commented-out, both `r1` and `r2` are _{unknown}_.
Well, it's a improvement at least. I guess this thing with type defaults is a different problem.
I also tried add Fn impls for fn items, but wasn't successful. So this PR only adds those impls for fn pointers.
Co-authored-by: Hrvoje Ban <[email protected]>
Diffstat (limited to 'crates/ra_assists/src/handlers/add_derive.rs')
0 files changed, 0 insertions, 0 deletions