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Rollup merge of #129034 - henryksloan:coroutine-must-use, r=joboet

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Add `#[must_use]` attribute to `Coroutine` trait

[Coroutines tracking issue](https://github.com/rust-lang/rust/issues/43122)

Like closures (`FnOnce`, `AsyncFn`, etc.), coroutines are lazy and do nothing unless called (resumed). Closure traits like `FnOnce` have `#[must_use = "closures are lazy and do nothing unless called"]` to catch likely bugs for users of APIs that produce them. This PR adds such a `#[must_use]` attribute to `trait Coroutine`.
This commit is contained in:
Matthias Krüger 2024-08-13 21:11:13 +02:00 • committed by GitHub
commit d4f5a89f6e
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2 changed files with 4 additions and 2 deletions
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1
library/core/src/ops/coroutine.rs
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@ -69,6 +69,7 @@ pub enum CoroutineState<Y, R> {
#[lang = "coroutine"] #[lang = "coroutine"]
#[unstable(feature = "coroutine_trait", issue = "43122")] #[unstable(feature = "coroutine_trait", issue = "43122")]
#[fundamental] #[fundamental]
#[must_use = "coroutines are lazy and do nothing unless resumed"]
pub trait Coroutine<R = ()> { pub trait Coroutine<R = ()> {
/// The type of value this coroutine yields. /// The type of value this coroutine yields.
/// ///

5
tests/ui/coroutine/issue-58888.rs
View file

@ -13,7 +13,8 @@ impl Database {
} }
fn check_connection(&self) -> impl Coroutine<Yield = (), Return = ()> + '_ { fn check_connection(&self) -> impl Coroutine<Yield = (), Return = ()> + '_ {
#[coroutine] move || { #[coroutine]
move || {
let iter = self.get_connection(); let iter = self.get_connection();
for i in iter { for i in iter {
yield i yield i
@ -23,5 +24,5 @@ impl Database {
} }
fn main() { fn main() {
Database.check_connection(); let _ = Database.check_connection();
} }