error: unnecessary parentheses around type
  --> $DIR/unused-parens-false-positive-issue-143653.rs:10:43
   |
LL | fn bar(_: Box<dyn FnMut(&mut u32) -> &mut (dyn MyTrait)>) {}
   |                                           ^           ^
   |
note: the lint level is defined here
  --> $DIR/unused-parens-false-positive-issue-143653.rs:3:9
   |
LL | #![deny(unused_parens)]
   |         ^^^^^^^^^^^^^
help: remove these parentheses
   |
LL - fn bar(_: Box<dyn FnMut(&mut u32) -> &mut (dyn MyTrait)>) {}
LL + fn bar(_: Box<dyn FnMut(&mut u32) -> &mut dyn MyTrait>) {}
   |

error: aborting due to 1 previous error