Incremental compilation bug with async fn method capturing multiple lifetimes #98890
Description
Regression since 1.62.0
The following diff:
struct Foo;
impl Foo {
async fn f(&self, _: &&()) -> &() {
&()
}
}
+ enum Bar {}if done in between cargo checks, makes the second check fail with:
error: lifetime may not live long enough
--> src/lib.rs:5:43
|
5 | async fn f(&self, _: &&()) -> &() {
| ____________________-__________-___________^
| | | |
| | | let's call the lifetime of this reference `'2`
| | let's call the lifetime of this reference `'1`
6 | | &()
7 | | }
| |_________^ associated function was supposed to return data with lifetime `'2` but it is returning data with lifetime `'1`- Aside: that error is printed twice, which is also curious.
To reproduce, the following snippet fails on the Playground:
fn main(){let _=std::process::Command::new("/bin/bash").args(&["-c", concat!(r##"{
set -euo pipefail
cd $(mktemp -d)
cargo init -q --name example --lib
cat> src/lib.rs <<'EOF'
#![allow(unused)]
struct Foo;
impl Foo {
async fn f(&self, _: &&()) -> &() {
&()
}
}
EOF
(set -x
cargo c -q
{ set +x; echo 'enum Bar {}'; } 2>/dev/null | tee -a src/lib.rs
cargo c -q
)
echo ✅
} 2>&1"##)]).status();}I've reported it over #96655 to avoid defining a duplicate issue, but now that I've noticed it's a regression, I prefer to risk it being a dup than it going unnoticed.
I've also mentioned this over: https://rust-lang.zulipchat.com/#narrow/stream/131828-t-compiler/topic/incremental.20bug.20with.20async.20fns.20and.20lifetimes
Context
This is causing major breakage with users of async-graphql who have switched to Rust 1.62.0 or up, as showcased by:
@rustbot modify labels: +regression-from-stable-to-stable -regression-untriaged