Prevent clippy::ignored_unit_patterns in macro expansions
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This is a pedantic lint added in 1.73.0. Because it occurs inside a
macro expansion, the lint is triggered from user code. The justification
given by the lint definition is:
> Matching with `()` explicitly instead of `_` outlines the fact that
> the pattern contains no data. Also it would detect a type change that
> `_` would ignore.
Removing the lint requires a trivial change. It does introduce the
possibility for compilation errors in the event the return type of the
function currently returning `()` changes, but that seems like more of a
benefit than a drawback. In these cases, it seems unlikely that the
return type in question will change in the future.
The user experience can be seen by linting the examples:
```
% cargo +nightly clippy --examples -- -A clippy::all -W clippy::ignored_unit_patterns -Z macro-backtrace
Compiling prometheus v0.13.3 (/home/matt/src/rust-prometheus)
...
warning: matching over `()` is more explicit
--> /home/matt/src/rust-prometheus/src/macros.rs:217:58
|
214 | macro_rules! register_counter {
| -----------------------------
| |
| in this expansion of `register_counter!` (tikv#1)
| in this expansion of `register_counter!` (tikv#2)
| in this expansion of `register_counter!` (tikv#3)
...
217 | $crate::register(Box::new(counter.clone())).map(|_| counter)
| ^
...
221 | register_counter!(@of_type Counter, $OPTS)
| ------------------------------------------ in this macro invocation (tikv#3)
...
225 | register_counter!(opts!($NAME, $HELP))
| -------------------------------------- in this macro invocation (tikv#2)
|
::: examples/example_push.rs:16:40
|
16 | static ref PUSH_COUNTER: Counter = register_counter!(
| ________________________________________-
17 | | "example_push_total",
18 | | "Total number of prometheus client pushed."
19 | | )
| |_____- in this macro invocation (tikv#1)
|
= help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#ignored_unit_patterns
= note: requested on the command line with `-W clippy::ignored-unit-patterns`
...
```
Signed-off-by: Matt Weber <30441572+mweber15@users.noreply.github.com>
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This is a pedantic lint added in 1.73.0. Because it occurs inside a macro expansion, the lint is triggered from user code. The justification given by the lint definition is:
Removing the lint requires a trivial change. It does introduce the possibility for compilation errors in the event the return type of the function currently returning
()changes, but that seems like more of a benefit than a drawback. In these cases, it seems unlikely that the return type in question will change in the future.The user experience can be seen by linting the examples: