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
|
use clippy_utils::consts::{constant_context, Constant};
use clippy_utils::diagnostics::span_lint_and_sugg;
use clippy_utils::source::snippet;
use clippy_utils::ty::is_type_diagnostic_item;
use if_chain::if_chain;
use rustc_errors::Applicability;
use rustc_hir::{Expr, ExprKind};
use rustc_lint::{LateContext, LateLintPass};
use rustc_session::{declare_lint_pass, declare_tool_lint};
use rustc_span::sym;
declare_clippy_lint! {
/// ### What it does
/// Checks for usage of `.repeat(1)` and suggest the following method for each types.
/// - `.to_string()` for `str`
/// - `.clone()` for `String`
/// - `.to_vec()` for `slice`
///
/// The lint will evaluate constant expressions and values as arguments of `.repeat(..)` and emit a message if
/// they are equivalent to `1`. (Related discussion in [rust-clippy#7306](https://github.com/rust-lang/rust-clippy/issues/7306))
///
/// ### Why is this bad?
/// For example, `String.repeat(1)` is equivalent to `.clone()`. If cloning
/// the string is the intention behind this, `clone()` should be used.
///
/// ### Example
/// ```rust
/// fn main() {
/// let x = String::from("hello world").repeat(1);
/// }
/// ```
/// Use instead:
/// ```rust
/// fn main() {
/// let x = String::from("hello world").clone();
/// }
/// ```
#[clippy::version = "1.47.0"]
pub REPEAT_ONCE,
complexity,
"using `.repeat(1)` instead of `String.clone()`, `str.to_string()` or `slice.to_vec()` "
}
declare_lint_pass!(RepeatOnce => [REPEAT_ONCE]);
impl<'tcx> LateLintPass<'tcx> for RepeatOnce {
fn check_expr(&mut self, cx: &LateContext<'_>, expr: &'tcx Expr<'_>) {
if_chain! {
if let ExprKind::MethodCall(path, [receiver, count], _) = &expr.kind;
if path.ident.name == sym!(repeat);
if constant_context(cx, cx.typeck_results()).expr(count) == Some(Constant::Int(1));
if !receiver.span.from_expansion();
then {
let ty = cx.typeck_results().expr_ty(receiver).peel_refs();
if ty.is_str() {
span_lint_and_sugg(
cx,
REPEAT_ONCE,
expr.span,
"calling `repeat(1)` on str",
"consider using `.to_string()` instead",
format!("{}.to_string()", snippet(cx, receiver.span, r#""...""#)),
Applicability::MachineApplicable,
);
} else if ty.builtin_index().is_some() {
span_lint_and_sugg(
cx,
REPEAT_ONCE,
expr.span,
"calling `repeat(1)` on slice",
"consider using `.to_vec()` instead",
format!("{}.to_vec()", snippet(cx, receiver.span, r#""...""#)),
Applicability::MachineApplicable,
);
} else if is_type_diagnostic_item(cx, ty, sym::String) {
span_lint_and_sugg(
cx,
REPEAT_ONCE,
expr.span,
"calling `repeat(1)` on a string literal",
"consider using `.clone()` instead",
format!("{}.clone()", snippet(cx, receiver.span, r#""...""#)),
Applicability::MachineApplicable,
);
}
}
}
}
}
|
