diff --git a/CHANGELOG.md b/CHANGELOG.md
index 251f32d2e6e..370772498e4 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4890,6 +4890,7 @@ Released 2018-09-13
[`if_same_then_else`]: https://rust-lang.github.io/rust-clippy/master/index.html#if_same_then_else
[`if_then_some_else_none`]: https://rust-lang.github.io/rust-clippy/master/index.html#if_then_some_else_none
[`ifs_same_cond`]: https://rust-lang.github.io/rust-clippy/master/index.html#ifs_same_cond
+[`ignored_unit_patterns`]: https://rust-lang.github.io/rust-clippy/master/index.html#ignored_unit_patterns
[`impl_trait_in_params`]: https://rust-lang.github.io/rust-clippy/master/index.html#impl_trait_in_params
[`implicit_clone`]: https://rust-lang.github.io/rust-clippy/master/index.html#implicit_clone
[`implicit_hasher`]: https://rust-lang.github.io/rust-clippy/master/index.html#implicit_hasher
diff --git a/clippy_dev/src/main.rs b/clippy_dev/src/main.rs
index 43eaccdf5a3..fca750fafc7 100644
--- a/clippy_dev/src/main.rs
+++ b/clippy_dev/src/main.rs
@@ -41,7 +41,7 @@ fn main() {
matches.get_one::<String>("type").map(String::as_str),
matches.get_flag("msrv"),
) {
- Ok(_) => update_lints::update(update_lints::UpdateMode::Change),
+ Ok(()) => update_lints::update(update_lints::UpdateMode::Change),
Err(e) => eprintln!("Unable to create lint: {e}"),
}
},
diff --git a/clippy_dev/src/setup/vscode.rs b/clippy_dev/src/setup/vscode.rs
index dbcdc9b59e5..204f4af2cf1 100644
--- a/clippy_dev/src/setup/vscode.rs
+++ b/clippy_dev/src/setup/vscode.rs
@@ -47,7 +47,7 @@ fn check_install_precondition(force_override: bool) -> bool {
}
} else {
match fs::create_dir(vs_dir_path) {
- Ok(_) => {
+ Ok(()) => {
println!("info: created `{VSCODE_DIR}` directory for clippy");
},
Err(err) => {
diff --git a/clippy_lints/src/declared_lints.rs b/clippy_lints/src/declared_lints.rs
index e084471433d..413025dafcb 100644
--- a/clippy_lints/src/declared_lints.rs
+++ b/clippy_lints/src/declared_lints.rs
@@ -203,6 +203,7 @@ pub(crate) static LINTS: &[&crate::LintInfo] = &[
crate::if_let_mutex::IF_LET_MUTEX_INFO,
crate::if_not_else::IF_NOT_ELSE_INFO,
crate::if_then_some_else_none::IF_THEN_SOME_ELSE_NONE_INFO,
+ crate::ignored_unit_patterns::IGNORED_UNIT_PATTERNS_INFO,
crate::implicit_hasher::IMPLICIT_HASHER_INFO,
crate::implicit_return::IMPLICIT_RETURN_INFO,
crate::implicit_saturating_add::IMPLICIT_SATURATING_ADD_INFO,
diff --git a/clippy_lints/src/ignored_unit_patterns.rs b/clippy_lints/src/ignored_unit_patterns.rs
new file mode 100644
index 00000000000..c635120b882
--- /dev/null
+++ b/clippy_lints/src/ignored_unit_patterns.rs
@@ -0,0 +1,52 @@
+use clippy_utils::diagnostics::span_lint_and_sugg;
+use hir::PatKind;
+use rustc_errors::Applicability;
+use rustc_hir as hir;
+use rustc_lint::{LateContext, LateLintPass};
+use rustc_session::{declare_lint_pass, declare_tool_lint};
+
+declare_clippy_lint! {
+ /// ### What it does
+ /// Checks for usage of `_` in patterns of type `()`.
+ ///
+ /// ### Why is this bad?
+ /// Matching with `()` explicitly instead of `_` outlines
+ /// the fact that the pattern contains no data. Also it
+ /// would detect a type change that `_` would ignore.
+ ///
+ /// ### Example
+ /// ```rust
+ /// match std::fs::create_dir("tmp-work-dir") {
+ /// Ok(_) => println!("Working directory created"),
+ /// Err(s) => eprintln!("Could not create directory: {s}"),
+ /// }
+ /// ```
+ /// Use instead:
+ /// ```rust
+ /// match std::fs::create_dir("tmp-work-dir") {
+ /// Ok(()) => println!("Working directory created"),
+ /// Err(s) => eprintln!("Could not create directory: {s}"),
+ /// }
+ /// ```
+ #[clippy::version = "1.73.0"]
+ pub IGNORED_UNIT_PATTERNS,
+ pedantic,
+ "suggest replacing `_` by `()` in patterns where appropriate"
+}
+declare_lint_pass!(IgnoredUnitPatterns => [IGNORED_UNIT_PATTERNS]);
+
+impl<'tcx> LateLintPass<'tcx> for IgnoredUnitPatterns {
+ fn check_pat(&mut self, cx: &LateContext<'tcx>, pat: &'tcx hir::Pat<'tcx>) {
+ if matches!(pat.kind, PatKind::Wild) && cx.typeck_results().pat_ty(pat).is_unit() {
+ span_lint_and_sugg(
+ cx,
+ IGNORED_UNIT_PATTERNS,
+ pat.span,
+ "matching over `()` is more explicit",
+ "use `()` instead of `_`",
+ String::from("()"),
+ Applicability::MachineApplicable,
+ );
+ }
+ }
+}
diff --git a/clippy_lints/src/lib.rs b/clippy_lints/src/lib.rs
index 9d6096ccb2a..358004cf460 100644
--- a/clippy_lints/src/lib.rs
+++ b/clippy_lints/src/lib.rs
@@ -147,6 +147,7 @@ mod future_not_send;
mod if_let_mutex;
mod if_not_else;
mod if_then_some_else_none;
+mod ignored_unit_patterns;
mod implicit_hasher;
mod implicit_return;
mod implicit_saturating_add;
@@ -1093,6 +1094,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
})
});
store.register_late_pass(|_| Box::new(redundant_locals::RedundantLocals));
+ store.register_late_pass(|_| Box::new(ignored_unit_patterns::IgnoredUnitPatterns));
// add lints here, do not remove this comment, it's used in `new_lint`
}
diff --git a/clippy_lints/src/option_if_let_else.rs b/clippy_lints/src/option_if_let_else.rs
index 40da002f4ff..a7a7f4fd8fa 100644
--- a/clippy_lints/src/option_if_let_else.rs
+++ b/clippy_lints/src/option_if_let_else.rs
@@ -155,7 +155,7 @@ fn try_get_option_occurrence<'tcx>(
});
if let ExprKind::Path(QPath::Resolved(None, Path { res: Res::Local(local_id), .. })) = e.kind {
match some_captures.get(local_id)
- .or_else(|| (method_sugg == "map_or_else").then_some(()).and_then(|_| none_captures.get(local_id)))
+ .or_else(|| (method_sugg == "map_or_else").then_some(()).and_then(|()| none_captures.get(local_id)))
{
Some(CaptureKind::Value | CaptureKind::Ref(Mutability::Mut)) => return None,
Some(CaptureKind::Ref(Mutability::Not)) if as_mut => return None,
diff --git a/tests/ui/ignored_unit_patterns.fixed b/tests/ui/ignored_unit_patterns.fixed
new file mode 100644
index 00000000000..492219fe447
--- /dev/null
+++ b/tests/ui/ignored_unit_patterns.fixed
@@ -0,0 +1,17 @@
+//@run-rustfix
+
+#![warn(clippy::ignored_unit_patterns)]
+#![allow(clippy::redundant_pattern_matching, clippy::single_match)]
+
+fn foo() -> Result<(), ()> {
+ unimplemented!()
+}
+
+fn main() {
+ match foo() {
+ Ok(()) => {},
+ Err(()) => {},
+ }
+ if let Ok(()) = foo() {}
+ let _ = foo().map_err(|()| todo!());
+}
diff --git a/tests/ui/ignored_unit_patterns.rs b/tests/ui/ignored_unit_patterns.rs
new file mode 100644
index 00000000000..90af36f8e5e
--- /dev/null
+++ b/tests/ui/ignored_unit_patterns.rs
@@ -0,0 +1,17 @@
+//@run-rustfix
+
+#![warn(clippy::ignored_unit_patterns)]
+#![allow(clippy::redundant_pattern_matching, clippy::single_match)]
+
+fn foo() -> Result<(), ()> {
+ unimplemented!()
+}
+
+fn main() {
+ match foo() {
+ Ok(_) => {},
+ Err(_) => {},
+ }
+ if let Ok(_) = foo() {}
+ let _ = foo().map_err(|_| todo!());
+}
diff --git a/tests/ui/ignored_unit_patterns.stderr b/tests/ui/ignored_unit_patterns.stderr
new file mode 100644
index 00000000000..8feea3cc2a8
--- /dev/null
+++ b/tests/ui/ignored_unit_patterns.stderr
@@ -0,0 +1,28 @@
+error: matching over `()` is more explicit
+ --> $DIR/ignored_unit_patterns.rs:12:12
+ |
+LL | Ok(_) => {},
+ | ^ help: use `()` instead of `_`: `()`
+ |
+ = note: `-D clippy::ignored-unit-patterns` implied by `-D warnings`
+
+error: matching over `()` is more explicit
+ --> $DIR/ignored_unit_patterns.rs:13:13
+ |
+LL | Err(_) => {},
+ | ^ help: use `()` instead of `_`: `()`
+
+error: matching over `()` is more explicit
+ --> $DIR/ignored_unit_patterns.rs:15:15
+ |
+LL | if let Ok(_) = foo() {}
+ | ^ help: use `()` instead of `_`: `()`
+
+error: matching over `()` is more explicit
+ --> $DIR/ignored_unit_patterns.rs:16:28
+ |
+LL | let _ = foo().map_err(|_| todo!());
+ | ^ help: use `()` instead of `_`: `()`
+
+error: aborting due to 4 previous errors
+