Code
struct Foo(String);
struct Bar;
fn foo(foos: &[Foo], bar: &'static Bar) {
let (tx, _rx) = tokio::sync::mpsc::unbounded_channel();
for foo in foos {
let tx = tx.clone();
tokio::spawn(async move {
tx.send(foo.0.clone()).unwrap();
});
}
}Current output
error[E0521]: borrowed data escapes outside of function
--> src/lib.rs:5:16
|
3 | fn foo(foos: &[Foo], bar: &'static Bar) {
| ---- - --- `bar` declared here, outside of the function body
| | |
| | let's call the lifetime of this reference `'1`
| `foos` is a reference that is only valid in the function body
4 | let (tx, _rx) = tokio::sync::mpsc::unbounded_channel();
5 | for foo in foos {
| ^^^^
| |
| `foos` escapes the function body here
| argument requires that `'1` must outlive `'static`
For more information about this error, try `rustc --explain E0521`.Desired output
I'm not sure what the perfect diagnostic would be here.
If you were the modify the code and not use a for loop/slice, you get something closer to this:
error[E0521]: borrowed data escapes outside of function
--> src/lib.rs:517:9
|
3 | fn foo(foos: &[Foo], bar: &'static Bar) {
| --- - --- `bar` declared here, outside of the function body
| | |
| | let's call the lifetime of this reference `'1`
| `foos` is a reference that is only valid in the function body
...
7 | / tokio::spawn(async move {
8 | | tx.send(foo.0.clone()).unwrap();
9 | | });
| | ^
| | |
| |__________`foos` escapes the function body here
| argument requires that `'1` must outlive `'static`
For more information about this error, try `rustc --explain E0521`.If you modify the original code to use std::sync::mpsc/std::thread::spawn you get the same error above.
But the
--- `bar` declared here, outside of the function body
is still a red herring. I think the perfect diagnostic would point to foo.0.clone and the tokio::spawn's F: 'static requirement.
Rationale and extra context
The problem is that the foo is moved by reference, so the task is not 'static. Pointing the error at the for loop is incorrect as it's not the culprit of the issue. This might be a lifetime inference bug
Other cases
No response
Anything else?
No response
Code
Current output
Desired output
I'm not sure what the perfect diagnostic would be here.
If you were the modify the code and not use a for loop/slice, you get something closer to this:
If you modify the original code to use std::sync::mpsc/std::thread::spawn you get the same error above.
But the
is still a red herring. I think the perfect diagnostic would point to
foo.0.cloneand thetokio::spawn'sF: 'staticrequirement.Rationale and extra context
The problem is that the
fooismoved by reference, so the task is not'static. Pointing the error at the for loop is incorrect as it's not the culprit of the issue. This might be a lifetime inference bugOther cases
No response
Anything else?
No response