Closed
Description
Reduced from an example given on the users forum.
This code (playground) fails to compile:
fn main() {
let v = vec![""];
runner(&v);
}
fn runner<'p>(v: &Vec<&'p str>) -> impl Iterator<Item = &'p str> {
find(&vec![0], v)
}
fn find<'n, 'p, I, S>(_: &'n I, _: &Vec<&'p str>) -> impl Iterator<Item = &'p str>
where
&'n I: IntoIterator<Item = S>,
{
std::iter::empty()
}error[E0597]: borrowed value does not live long enough
--> src/main.rs:7:11
|
7 | find(&vec![0], v)
| ^^^^^^^ temporary value does not live long enough
8 | }
| - temporary value only lives until here
|
note: borrowed value must be valid for the lifetime 'p as defined on the function body at 6:1...
--> src/main.rs:6:1
|
6 | fn runner<'p>(v: &Vec<&'p str>) -> impl Iterator<Item = &'p str> {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
= note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
It seems the 'n lifetime is getting tied into the return type somehow.
It works if you make find return an explicit type:
fn find<'n, 'p, I, S>(_: &'n I, _: &Vec<&'p str>) -> std::iter::Empty<&'p str>
where
&'n I: IntoIterator<Item = S>,
{
std::iter::empty()
}It also works if you instead remove the S parameter:
fn find<'n, 'p, I>(_: &'n I, _: &Vec<&'p str>) -> impl Iterator<Item = &'p str>
where
&'n I: IntoIterator,
{
std::iter::empty()
}