warning: use of a double negation
  --> $DIR/lint-double-negations-macro.rs:9:9
   |
LL |         --$e
   |         ^^^^
...
LL |     bad_macro!(1);
   |     ------------- in this macro invocation
   |
   = note: the prefix `--` could be misinterpreted as a decrement operator which exists in other languages
   = note: use `-= 1` if you meant to decrement the value
   = note: `#[warn(double_negations)]` on by default
   = note: this warning originates in the macro `bad_macro` (in Nightly builds, run with -Z macro-backtrace for more info)
help: add parentheses for clarity
   |
LL |         -(-$e)
   |          +   +

warning: 1 warning emitted