mikros/rust
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

Rollup merge of #56402 - scottmcm:better-marker-trait-example, r=Centril

Browse Source 
Improve the unstable book example for #[marker] trait

The previous one didn't actually use the Display&Debug bounds in any way, so I think this one is a bit more meaningful.
This commit is contained in:
kennytm 2018-12-03 18:07:10 +08:00 committed by GitHub
commit 65e67025c8
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
1 changed files with 8 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

14
src/doc/unstable-book/src/language-features/marker-trait-attr.md
View File

@ -17,15 +17,17 @@ when they'd need to do the same thing for every type anyway).
```rust
#![feature(marker_trait_attr)]
use std::fmt::{Debug, Display};
#[marker] trait CheapToClone: Clone {}
#[marker] trait MyMarker {}
impl<T: Copy> CheapToClone for T {}
impl<T: Debug> MyMarker for T {}
impl<T: Display> MyMarker for T {}
// These could potentally overlap with the blanket implementation above,
// so are only allowed because CheapToClone is a marker trait.
impl<T: CheapToClone, U: CheapToClone> CheapToClone for (T, U) {}
impl<T: CheapToClone> CheapToClone for std::ops::Range<T> {}
fn foo<T: MyMarker>(t: T) -> T {
t
fn cheap_clone<T: CheapToClone>(t: T) -> T {
t.clone()
}
```