1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
|
use clippy_utils::diagnostics::span_lint_and_sugg;
use hir::{Node, PatKind};
use rustc_errors::Applicability;
use rustc_hir as hir;
use rustc_lint::{LateContext, LateLintPass};
use rustc_session::declare_lint_pass;
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
/// ```no_run
/// match std::fs::create_dir("tmp-work-dir") {
/// Ok(_) => println!("Working directory created"),
/// Err(s) => eprintln!("Could not create directory: {s}"),
/// }
/// ```
/// Use instead:
/// ```no_run
/// 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)
&& !pat.span.from_expansion()
&& cx.typeck_results().pat_ty(pat).peel_refs().is_unit()
{
match cx.tcx.parent_hir_node(pat.hir_id) {
Node::Param(param) if matches!(cx.tcx.parent_hir_node(param.hir_id), Node::Item(_)) => {
// Ignore function parameters
return;
},
Node::LetStmt(local) if local.ty.is_some() => {
// Ignore let bindings with explicit type
return;
},
_ => {},
}
span_lint_and_sugg(
cx,
IGNORED_UNIT_PATTERNS,
pat.span,
"matching over `()` is more explicit",
"use `()` instead of `_`",
String::from("()"),
Applicability::MachineApplicable,
);
}
}
}
|
