error: manual implementation of `Instant::elapsed`
  --> $DIR/manual_instant_elapsed.rs:18:20
   |
LL |     let duration = Instant::now() - prev_instant;
   |                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `prev_instant.elapsed()`
   |
   = note: `-D clippy::manual-instant-elapsed` implied by `-D warnings`

error: manual implementation of `Instant::elapsed`
  --> $DIR/manual_instant_elapsed.rs:27:5
   |
LL |     Instant::now() - *ref_to_instant; // to ensure parens are added correctly
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `(*ref_to_instant).elapsed()`

error: aborting due to 2 previous errors