error: `impl` item signature doesn't match `trait` item signature
  --> $DIR/signature-mismatch.rs:15:5
   |
LL |     fn async_fn(&self, buff: &[u8]) -> impl Future<Output = Vec<u8>>;
   |     ----------------------------------------------------------------- expected `fn(&'1 Struct, &'2 [u8]) -> impl Future<Output = Vec<u8>> + '3`
...
LL |     fn async_fn<'a>(&self, buff: &'a [u8]) -> impl Future<Output = Vec<u8>> + 'a {
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ found `fn(&'1 Struct, &'2 [u8]) -> impl Future<Output = Vec<u8>> + '2`
   |
   = note: expected signature `fn(&'1 Struct, &'2 [u8]) -> impl Future<Output = Vec<u8>> + '3`
              found signature `fn(&'1 Struct, &'2 [u8]) -> impl Future<Output = Vec<u8>> + '2`
   = help: the lifetime requirements from the `impl` do not correspond to the requirements in the `trait`
   = help: verify the lifetime relationships in the `trait` and `impl` between the `self` argument, the other inputs and its output

error: aborting due to previous error