error[E0623]: lifetime mismatch --> $DIR/signature-mismatch.rs:79:10 | LL | &'a self, | -------- this parameter and the return type are declared with different lifetimes... ... LL | ) -> impl Future> { | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ | | | ...but data from `buff` is returned here error: aborting due to 1 previous error For more information about this error, try `rustc --explain E0623`.