error: unused `error_stack::Report` that must be used
  --> tests/ui/must_use.rs:19:5
   |
19 |     Report::new(RootError);
   |     ^^^^^^^^^^^^^^^^^^^^^^
   |
note: the lint level is defined here
  --> tests/ui/must_use.rs:1:9
   |
1  | #![deny(unused_must_use)]
   |         ^^^^^^^^^^^^^^^
help: use `let _ = ...` to ignore the resulting value
   |
19 |     let _ = Report::new(RootError);
   |     +++++++