Closed
Description
I tried this code:
trait MyTrait {
}
struct MyTraitStruct;
impl MyTrait for MyTraitStruct {
}
fn inner<F>(writer: F) -> impl MyTrait + 'static
where F: FnOnce(&mut [u8]) {
MyTraitStruct
}
fn outer(data: &[u8]) -> impl MyTrait + 'static {
inner(|dst| {
dst.copy_from_slice(data)
})
}I expected to see this compile.
Instead, I get this error:
error[E0700]: hidden type for `impl MyTrait + 'static` captures lifetime that does not appear in bounds
--> core\src\pipeline\sbt.rs:222:5
|
221 | fn outer(data: &[u8]) -> impl MyTrait + 'static {
| ----- hidden type `impl MyTrait + 'static` captures the anonymous lifetime defined here
222 | / inner(|dst| {
223 | | dst.copy_from_slice(data)
224 | | })
| |______^
For more information about this error, try `rustc --explain E0700`.
The writer argument is just a impl FnOnce(&mut [u8]) with no lifetime bounds.
The lifetime there is a HRTB, the full trait def is for<'a> FnOnce(&'a mut [u8])
It says the closure needs to accept any mutable byte slice, regardless of the slices lifetime.
It should have no impact on the lifetime of the closure.
Meta
rustc --version --verbose:
rustc 1.69.0-nightly (34e6673a0 2023-02-25)
binary: rustc
commit-hash: 34e6673a0473e90ef01a18eb575392c9e3859747
commit-date: 2023-02-25
host: x86_64-pc-windows-msvc
release: 1.69.0-nightly
LLVM version: 15.0.7