1 use clippy_utils
::consts
::{constant_context, Constant}
;
2 use clippy_utils
::diagnostics
::span_lint_and_sugg
;
3 use clippy_utils
::in_macro
;
4 use clippy_utils
::source
::snippet
;
5 use clippy_utils
::ty
::is_type_diagnostic_item
;
6 use if_chain
::if_chain
;
7 use rustc_errors
::Applicability
;
8 use rustc_hir
::{Expr, ExprKind}
;
9 use rustc_lint
::{LateContext, LateLintPass}
;
10 use rustc_session
::{declare_lint_pass, declare_tool_lint}
;
13 declare_clippy_lint
! {
15 /// Checks for usage of `.repeat(1)` and suggest the following method for each types.
16 /// - `.to_string()` for `str`
17 /// - `.clone()` for `String`
18 /// - `.to_vec()` for `slice`
20 /// The lint will evaluate constant expressions and values as arguments of `.repeat(..)` and emit a message if
21 /// they are equivalent to `1`. (Related discussion in [rust-clippy#7306](https://github.com/rust-lang/rust-clippy/issues/7306))
23 /// ### Why is this bad?
24 /// For example, `String.repeat(1)` is equivalent to `.clone()`. If cloning
25 /// the string is the intention behind this, `clone()` should be used.
30 /// let x = String::from("hello world").repeat(1);
36 /// let x = String::from("hello world").clone();
41 "using `.repeat(1)` instead of `String.clone()`, `str.to_string()` or `slice.to_vec()` "
44 declare_lint_pass
!(RepeatOnce
=> [REPEAT_ONCE
]);
46 impl<'tcx
> LateLintPass
<'tcx
> for RepeatOnce
{
47 fn check_expr(&mut self, cx
: &LateContext
<'_
>, expr
: &'tcx Expr
<'_
>) {
49 if let ExprKind
::MethodCall(path
, _
, [receiver
, count
], _
) = &expr
.kind
;
50 if path
.ident
.name
== sym
!(repeat
);
51 if let Some(Constant
::Int(1)) = constant_context(cx
, cx
.typeck_results()).expr(count
);
52 if !in_macro(receiver
.span
);
54 let ty
= cx
.typeck_results().expr_ty(receiver
).peel_refs();
60 "calling `repeat(1)` on str",
61 "consider using `.to_string()` instead",
62 format
!("{}.to_string()", snippet(cx
, receiver
.span
, r
#""...""#)),
63 Applicability
::MachineApplicable
,
65 } else if ty
.builtin_index().is_some() {
70 "calling `repeat(1)` on slice",
71 "consider using `.to_vec()` instead",
72 format
!("{}.to_vec()", snippet(cx
, receiver
.span
, r
#""...""#)),
73 Applicability
::MachineApplicable
,
75 } else if is_type_diagnostic_item(cx
, ty
, sym
::string_type
) {
80 "calling `repeat(1)` on a string literal",
81 "consider using `.clone()` instead",
82 format
!("{}.clone()", snippet(cx
, receiver
.span
, r
#""...""#)),
83 Applicability
::MachineApplicable
,