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
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
|
use clippy_utils::diagnostics::{span_lint_and_help, span_lint_and_sugg};
use clippy_utils::source::{snippet, snippet_with_macro_callsite};
use clippy_utils::sugg::Sugg;
use clippy_utils::ty::{is_type_diagnostic_item, same_type_and_consts};
use clippy_utils::{get_parent_expr, is_trait_method, match_def_path, paths};
use if_chain::if_chain;
use rustc_errors::Applicability;
use rustc_hir::{Expr, ExprKind, HirId, MatchSource};
use rustc_lint::{LateContext, LateLintPass};
use rustc_middle::ty;
use rustc_session::{declare_tool_lint, impl_lint_pass};
use rustc_span::sym;
declare_clippy_lint! {
/// ### What it does
/// Checks for `Into`, `TryInto`, `From`, `TryFrom`, or `IntoIter` calls
/// which uselessly convert to the same type.
///
/// ### Why is this bad?
/// Redundant code.
///
/// ### Example
/// ```rust
/// // format!() returns a `String`
/// let s: String = format!("hello").into();
/// ```
///
/// Use instead:
/// ```rust
/// let s: String = format!("hello");
/// ```
#[clippy::version = "1.45.0"]
pub USELESS_CONVERSION,
complexity,
"calls to `Into`, `TryInto`, `From`, `TryFrom`, or `IntoIter` which perform useless conversions to the same type"
}
#[derive(Default)]
pub struct UselessConversion {
try_desugar_arm: Vec<HirId>,
}
impl_lint_pass!(UselessConversion => [USELESS_CONVERSION]);
#[expect(clippy::too_many_lines)]
impl<'tcx> LateLintPass<'tcx> for UselessConversion {
fn check_expr(&mut self, cx: &LateContext<'tcx>, e: &'tcx Expr<'_>) {
if e.span.from_expansion() {
return;
}
if Some(&e.hir_id) == self.try_desugar_arm.last() {
return;
}
match e.kind {
ExprKind::Match(_, arms, MatchSource::TryDesugar) => {
let e = match arms[0].body.kind {
ExprKind::Ret(Some(e)) | ExprKind::Break(_, Some(e)) => e,
_ => return,
};
if let ExprKind::Call(_, [arg, ..]) = e.kind {
self.try_desugar_arm.push(arg.hir_id);
}
},
ExprKind::MethodCall(name, recv, ..) => {
if is_trait_method(cx, e, sym::Into) && name.ident.as_str() == "into" {
let a = cx.typeck_results().expr_ty(e);
let b = cx.typeck_results().expr_ty(recv);
if same_type_and_consts(a, b) {
let sugg = snippet_with_macro_callsite(cx, recv.span, "<expr>").to_string();
span_lint_and_sugg(
cx,
USELESS_CONVERSION,
e.span,
&format!("useless conversion to the same type: `{}`", b),
"consider removing `.into()`",
sugg,
Applicability::MachineApplicable, // snippet
);
}
}
if is_trait_method(cx, e, sym::IntoIterator) && name.ident.name == sym::into_iter {
if let Some(parent_expr) = get_parent_expr(cx, e) {
if let ExprKind::MethodCall(parent_name, ..) = parent_expr.kind {
if parent_name.ident.name != sym::into_iter {
return;
}
}
}
let a = cx.typeck_results().expr_ty(e);
let b = cx.typeck_results().expr_ty(recv);
if same_type_and_consts(a, b) {
let sugg = snippet(cx, recv.span, "<expr>").into_owned();
span_lint_and_sugg(
cx,
USELESS_CONVERSION,
e.span,
&format!("useless conversion to the same type: `{}`", b),
"consider removing `.into_iter()`",
sugg,
Applicability::MachineApplicable, // snippet
);
}
}
if_chain! {
if is_trait_method(cx, e, sym::TryInto) && name.ident.name == sym::try_into;
let a = cx.typeck_results().expr_ty(e);
let b = cx.typeck_results().expr_ty(recv);
if is_type_diagnostic_item(cx, a, sym::Result);
if let ty::Adt(_, substs) = a.kind();
if let Some(a_type) = substs.types().next();
if same_type_and_consts(a_type, b);
then {
span_lint_and_help(
cx,
USELESS_CONVERSION,
e.span,
&format!("useless conversion to the same type: `{}`", b),
None,
"consider removing `.try_into()`",
);
}
}
},
ExprKind::Call(path, [arg]) => {
if_chain! {
if let ExprKind::Path(ref qpath) = path.kind;
if let Some(def_id) = cx.qpath_res(qpath, path.hir_id).opt_def_id();
then {
let a = cx.typeck_results().expr_ty(e);
let b = cx.typeck_results().expr_ty(arg);
if_chain! {
if match_def_path(cx, def_id, &paths::TRY_FROM);
if is_type_diagnostic_item(cx, a, sym::Result);
if let ty::Adt(_, substs) = a.kind();
if let Some(a_type) = substs.types().next();
if same_type_and_consts(a_type, b);
then {
let hint = format!("consider removing `{}()`", snippet(cx, path.span, "TryFrom::try_from"));
span_lint_and_help(
cx,
USELESS_CONVERSION,
e.span,
&format!("useless conversion to the same type: `{}`", b),
None,
&hint,
);
}
}
if_chain! {
if match_def_path(cx, def_id, &paths::FROM_FROM);
if same_type_and_consts(a, b);
then {
let sugg = Sugg::hir_with_macro_callsite(cx, arg, "<expr>").maybe_par();
let sugg_msg =
format!("consider removing `{}()`", snippet(cx, path.span, "From::from"));
span_lint_and_sugg(
cx,
USELESS_CONVERSION,
e.span,
&format!("useless conversion to the same type: `{}`", b),
&sugg_msg,
sugg.to_string(),
Applicability::MachineApplicable, // snippet
);
}
}
}
}
},
_ => {},
}
}
fn check_expr_post(&mut self, _: &LateContext<'tcx>, e: &'tcx Expr<'_>) {
if Some(&e.hir_id) == self.try_desugar_arm.last() {
self.try_desugar_arm.pop();
}
}
}
|
