struct Test(String);
impl Test {
async fn borrow_async(&self) {}
fn borrow(&self) {}
fn with(&mut self, s: &str) -> &mut Self {
self.0 = s.into();
self
}
}
async fn test() {
// error[E0716]: temporary value dropped while borrowed
Test("".to_string()).with("123").borrow_async().await;
}
fn main() {
// Temporary outlives the borrow() call
Test("".to_string()).with("123").borrow();
}https://play.rust-lang.org/?version=nightly&mode=release&edition=2018&gist=2649e4f172c54090d759b2f9484b31e1
A fairly common pattern is to use builder functions that takes &mut self and returns &mut Self so that multiple builder methods can be used in a row followed by building/using the final value. With normal, sync functions this works fine since the created temporary lives as long as the enclosing statement but if the final result is awaited on then we instead get an error.
This forces such builders to use moving functions fn (self) -> Self which can limit their use or to always write the builder as
let mut init = Init();
init.modify();
init.build();
Is it possible and/or planned that temporaries can be used in this way with await?
https://play.rust-lang.org/?version=nightly&mode=release&edition=2018&gist=2649e4f172c54090d759b2f9484b31e1
A fairly common pattern is to use builder functions that takes
&mut selfand returns&mut Selfso that multiple builder methods can be used in a row followed by building/using the final value. With normal, sync functions this works fine since the created temporary lives as long as the enclosing statement but if the final result isawaited on then we instead get an error.This forces such builders to use moving functions
fn (self) -> Selfwhich can limit their use or to always write the builder asIs it possible and/or planned that temporaries can be used in this way with await?