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
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
|
use clippy_utils::diagnostics::span_lint_and_sugg;
use clippy_utils::is_wild;
use clippy_utils::source::snippet_with_applicability;
use rustc_ast::{Attribute, LitKind};
use rustc_errors::Applicability;
use rustc_hir::{Arm, BorrowKind, Expr, ExprKind, Guard, Pat};
use rustc_lint::LateContext;
use rustc_middle::ty;
use rustc_span::source_map::Spanned;
use super::MATCH_LIKE_MATCHES_MACRO;
/// Lint a `match` or `if let .. { .. } else { .. }` expr that could be replaced by `matches!`
pub(crate) fn check_if_let<'tcx>(
cx: &LateContext<'tcx>,
expr: &'tcx Expr<'_>,
let_pat: &'tcx Pat<'_>,
let_expr: &'tcx Expr<'_>,
then_expr: &'tcx Expr<'_>,
else_expr: &'tcx Expr<'_>,
) {
find_matches_sugg(
cx,
let_expr,
IntoIterator::into_iter([
(&[][..], Some(let_pat), then_expr, None),
(&[][..], None, else_expr, None),
]),
expr,
true,
);
}
pub(super) fn check_match<'tcx>(
cx: &LateContext<'tcx>,
e: &'tcx Expr<'_>,
scrutinee: &'tcx Expr<'_>,
arms: &'tcx [Arm<'tcx>],
) -> bool {
find_matches_sugg(
cx,
scrutinee,
arms.iter().map(|arm| {
(
cx.tcx.hir().attrs(arm.hir_id),
Some(arm.pat),
arm.body,
arm.guard.as_ref(),
)
}),
e,
false,
)
}
/// Lint a `match` or `if let` for replacement by `matches!`
fn find_matches_sugg<'a, 'b, I>(
cx: &LateContext<'_>,
ex: &Expr<'_>,
mut iter: I,
expr: &Expr<'_>,
is_if_let: bool,
) -> bool
where
'b: 'a,
I: Clone
+ DoubleEndedIterator
+ ExactSizeIterator
+ Iterator<
Item = (
&'a [Attribute],
Option<&'a Pat<'b>>,
&'a Expr<'b>,
Option<&'a Guard<'b>>,
),
>,
{
if_chain! {
if iter.len() >= 2;
if cx.typeck_results().expr_ty(expr).is_bool();
if let Some((_, last_pat_opt, last_expr, _)) = iter.next_back();
let iter_without_last = iter.clone();
if let Some((first_attrs, _, first_expr, first_guard)) = iter.next();
if let Some(b0) = find_bool_lit(&first_expr.kind);
if let Some(b1) = find_bool_lit(&last_expr.kind);
if b0 != b1;
if first_guard.is_none() || iter.len() == 0;
if first_attrs.is_empty();
if iter
.all(|arm| {
find_bool_lit(&arm.2.kind).map_or(false, |b| b == b0) && arm.3.is_none() && arm.0.is_empty()
});
then {
if let Some(last_pat) = last_pat_opt {
if !is_wild(last_pat) {
return false;
}
}
// The suggestion may be incorrect, because some arms can have `cfg` attributes
// evaluated into `false` and so such arms will be stripped before.
let mut applicability = Applicability::MaybeIncorrect;
let pat = {
use itertools::Itertools as _;
iter_without_last
.filter_map(|arm| {
let pat_span = arm.1?.span;
Some(snippet_with_applicability(cx, pat_span, "..", &mut applicability))
})
.join(" | ")
};
let pat_and_guard = if let Some(Guard::If(g)) = first_guard {
format!("{} if {}", pat, snippet_with_applicability(cx, g.span, "..", &mut applicability))
} else {
pat
};
// strip potential borrows (#6503), but only if the type is a reference
let mut ex_new = ex;
if let ExprKind::AddrOf(BorrowKind::Ref, .., ex_inner) = ex.kind {
if let ty::Ref(..) = cx.typeck_results().expr_ty(ex_inner).kind() {
ex_new = ex_inner;
}
};
span_lint_and_sugg(
cx,
MATCH_LIKE_MATCHES_MACRO,
expr.span,
&format!("{} expression looks like `matches!` macro", if is_if_let { "if let .. else" } else { "match" }),
"try this",
format!(
"{}matches!({}, {})",
if b0 { "" } else { "!" },
snippet_with_applicability(cx, ex_new.span, "..", &mut applicability),
pat_and_guard,
),
applicability,
);
true
} else {
false
}
}
}
/// Extract a `bool` or `{ bool }`
fn find_bool_lit(ex: &ExprKind<'_>) -> Option<bool> {
match ex {
ExprKind::Lit(Spanned {
node: LitKind::Bool(b), ..
}) => Some(*b),
ExprKind::Block(
rustc_hir::Block {
stmts: &[],
expr: Some(exp),
..
},
_,
) => {
if let ExprKind::Lit(Spanned {
node: LitKind::Bool(b), ..
}) = exp.kind
{
Some(b)
} else {
None
}
},
_ => None,
}
}
|
