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A lifetime didn't match what was expected.
Erroneous code example:
```compile_fail,E0623
struct Foo<'a, 'b, T>(std::marker::PhantomData<(&'a (), &'b (), T)>)
where
T: Convert<'a, 'b>;
trait Convert<'a, 'b>: Sized {
fn cast(&'a self) -> &'b Self;
}
impl<'long: 'short, 'short, T> Convert<'long, 'short> for T {
fn cast(&'long self) -> &'short T {
self
}
}
// error
fn badboi<'in_, 'out, T>(
x: Foo<'in_, 'out, T>,
sadness: &'in_ T
) -> &'out T {
sadness.cast()
}
```
In this example, we tried to set a value with an incompatible lifetime to
another one (`'in_` is unrelated to `'out`). We can solve this issue in
two different ways:
Either we make `'in_` live at least as long as `'out`:
```
struct Foo<'a, 'b, T>(std::marker::PhantomData<(&'a (), &'b (), T)>)
where
T: Convert<'a, 'b>;
trait Convert<'a, 'b>: Sized {
fn cast(&'a self) -> &'b Self;
}
impl<'long: 'short, 'short, T> Convert<'long, 'short> for T {
fn cast(&'long self) -> &'short T {
self
}
}
fn badboi<'in_: 'out, 'out, T>(
x: Foo<'in_, 'out, T>,
sadness: &'in_ T
) -> &'out T {
sadness.cast()
}
```
Or we use only one lifetime:
```
struct Foo<'a, 'b, T>(std::marker::PhantomData<(&'a (), &'b (), T)>)
where
T: Convert<'a, 'b>;
trait Convert<'a, 'b>: Sized {
fn cast(&'a self) -> &'b Self;
}
impl<'long: 'short, 'short, T> Convert<'long, 'short> for T {
fn cast(&'long self) -> &'short T {
self
}
}
fn badboi<'out, T>(x: Foo<'out, 'out, T>, sadness: &'out T) -> &'out T {
sadness.cast()
}
```
|
