error: Try not to call a closure in the expression where it is declared.
  --> $DIR/redundant_closure_call_fixable.rs:7:13
   |
LL |     let a = (|| 42)();
   |             ^^^^^^^^^ help: Try doing something like: : `42`
   |
   = note: `-D clippy::redundant-closure-call` implied by `-D warnings`

error: aborting due to previous error