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

Rollup merge of #74781 - GuillaumeGomez:cleanup-e0733, r=jyn514

Browse Source 
Clean up E0733 explanation

r? @Dylan-DPC
This commit is contained in:
Yuki Okushi 2020-08-03 01:05:15 +09:00 committed by GitHub
commit 5323b9fd9c
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
1 changed files with 9 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

14
src/librustc_error_codes/error_codes/E0733.md
View File

@ -1,4 +1,6 @@
Recursion in an `async fn` requires boxing. For example, this will not compile: An [`async`] function used recursion without boxing.
Erroneous code example:
```edition2018,compile_fail,E0733 ```edition2018,compile_fail,E0733
async fn foo(n: usize) { async fn foo(n: usize) {
@ -8,8 +10,8 @@ async fn foo(n: usize) {
} }
``` ```
To achieve async recursion, the `async fn` needs to be desugared To perform async recursion, the `async fn` needs to be desugared such that the
such that the `Future` is explicit in the return type: `Future` is explicit in the return type:
```edition2018,compile_fail,E0720 ```edition2018,compile_fail,E0720
use std::future::Future; use std::future::Future;
@ -36,5 +38,7 @@ fn foo_recursive(n: usize) -> Pin<Box<dyn Future<Output = ()>>> {
} }
``` ```
The `Box<...>` ensures that the result is of known size, The `Box<...>` ensures that the result is of known size, and the pin is
and the pin is required to keep it in the same place in memory. required to keep it in the same place in memory.
[`async`]: https://doc.rust-lang.org/std/keyword.async.html