error: used binding `_foo` which is prefixed with an underscore. A leading underscore signals that a binding will not be used
  --> tests/ui/used_underscore_binding.rs:23:5
   |
LL |     _foo + 1
   |     ^^^^
   |
note: `_foo` is defined here
  --> tests/ui/used_underscore_binding.rs:22:22
   |
LL | fn prefix_underscore(_foo: u32) -> u32 {
   |                      ^^^^
   = note: `-D clippy::used-underscore-binding` implied by `-D warnings`
   = help: to override `-D warnings` add `#[allow(clippy::used_underscore_binding)]`

error: used binding `_foo` which is prefixed with an underscore. A leading underscore signals that a binding will not be used
  --> tests/ui/used_underscore_binding.rs:28:20
   |
LL |     println!("{}", _foo);
   |                    ^^^^
   |
note: `_foo` is defined here
  --> tests/ui/used_underscore_binding.rs:27:24
   |
LL | fn in_macro_or_desugar(_foo: u32) {
   |                        ^^^^

error: used binding `_foo` which is prefixed with an underscore. A leading underscore signals that a binding will not be used
  --> tests/ui/used_underscore_binding.rs:29:16
   |
LL |     assert_eq!(_foo, _foo);
   |                ^^^^
   |
note: `_foo` is defined here
  --> tests/ui/used_underscore_binding.rs:27:24
   |
LL | fn in_macro_or_desugar(_foo: u32) {
   |                        ^^^^

error: used binding `_foo` which is prefixed with an underscore. A leading underscore signals that a binding will not be used
  --> tests/ui/used_underscore_binding.rs:29:22
   |
LL |     assert_eq!(_foo, _foo);
   |                      ^^^^
   |
note: `_foo` is defined here
  --> tests/ui/used_underscore_binding.rs:27:24
   |
LL | fn in_macro_or_desugar(_foo: u32) {
   |                        ^^^^

error: used binding `_underscore_field` which is prefixed with an underscore. A leading underscore signals that a binding will not be used
  --> tests/ui/used_underscore_binding.rs:42:5
   |
LL |     s._underscore_field += 1;
   |     ^^^^^^^^^^^^^^^^^^^
   |
note: `_underscore_field` is defined here
  --> tests/ui/used_underscore_binding.rs:36:5
   |
LL |     _underscore_field: u32,
   |     ^^^^^^^^^^^^^^^^^^^^^^

error: used binding `_i` which is prefixed with an underscore. A leading underscore signals that a binding will not be used
  --> tests/ui/used_underscore_binding.rs:103:16
   |
LL |         uses_i(_i);
   |                ^^
   |
note: `_i` is defined here
  --> tests/ui/used_underscore_binding.rs:102:13
   |
LL |         let _i = 5;
   |             ^^

error: aborting due to 6 previous errors