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
|
use clippy_utils::diagnostics::{span_lint_and_sugg, span_lint_and_then};
use clippy_utils::get_parent_node;
use clippy_utils::source::snippet_with_context;
use clippy_utils::sugg;
use clippy_utils::ty::is_copy;
use rustc_errors::Applicability;
use rustc_hir::{BindingAnnotation, ByRef, Expr, ExprKind, MatchSource, Node, PatKind, QPath};
use rustc_lint::LateContext;
use rustc_middle::ty::{self, adjustment::Adjust};
use rustc_span::symbol::{sym, Symbol};
use super::CLONE_DOUBLE_REF;
use super::CLONE_ON_COPY;
/// Checks for the `CLONE_ON_COPY` lint.
#[allow(clippy::too_many_lines)]
pub(super) fn check(
cx: &LateContext<'_>,
expr: &Expr<'_>,
method_name: Symbol,
receiver: &Expr<'_>,
args: &[Expr<'_>],
) {
let arg = if method_name == sym::clone && args.is_empty() {
receiver
} else {
return;
};
if cx
.typeck_results()
.type_dependent_def_id(expr.hir_id)
.and_then(|id| cx.tcx.trait_of_item(id))
.zip(cx.tcx.lang_items().clone_trait())
.map_or(true, |(x, y)| x != y)
{
return;
}
let arg_adjustments = cx.typeck_results().expr_adjustments(arg);
let arg_ty = arg_adjustments
.last()
.map_or_else(|| cx.typeck_results().expr_ty(arg), |a| a.target);
let ty = cx.typeck_results().expr_ty(expr);
if let ty::Ref(_, inner, _) = arg_ty.kind() {
if let ty::Ref(_, innermost, _) = inner.kind() {
span_lint_and_then(
cx,
CLONE_DOUBLE_REF,
expr.span,
&format!(
"using `clone` on a double-reference; \
this will copy the reference of type `{}` instead of cloning the inner type",
ty
),
|diag| {
if let Some(snip) = sugg::Sugg::hir_opt(cx, arg) {
let mut ty = innermost;
let mut n = 0;
while let ty::Ref(_, inner, _) = ty.kind() {
ty = inner;
n += 1;
}
let refs = "&".repeat(n + 1);
let derefs = "*".repeat(n);
let explicit = format!("<{}{}>::clone({})", refs, ty, snip);
diag.span_suggestion(
expr.span,
"try dereferencing it",
format!("{}({}{}).clone()", refs, derefs, snip.deref()),
Applicability::MaybeIncorrect,
);
diag.span_suggestion(
expr.span,
"or try being explicit if you are sure, that you want to clone a reference",
explicit,
Applicability::MaybeIncorrect,
);
}
},
);
return; // don't report clone_on_copy
}
}
if is_copy(cx, ty) {
let parent_is_suffix_expr = match get_parent_node(cx.tcx, expr.hir_id) {
Some(Node::Expr(parent)) => match parent.kind {
// &*x is a nop, &x.clone() is not
ExprKind::AddrOf(..) => return,
// (*x).func() is useless, x.clone().func() can work in case func borrows self
ExprKind::MethodCall(_, self_arg, ..)
if expr.hir_id == self_arg.hir_id && ty != cx.typeck_results().expr_ty_adjusted(expr) =>
{
return;
},
// ? is a Call, makes sure not to rec *x?, but rather (*x)?
ExprKind::Call(hir_callee, _) => matches!(
hir_callee.kind,
ExprKind::Path(QPath::LangItem(rustc_hir::LangItem::TryTraitBranch, _, _))
),
ExprKind::MethodCall(_, self_arg, ..) if expr.hir_id == self_arg.hir_id => true,
ExprKind::Match(_, _, MatchSource::TryDesugar | MatchSource::AwaitDesugar)
| ExprKind::Field(..)
| ExprKind::Index(..) => true,
_ => false,
},
// local binding capturing a reference
Some(Node::Local(l)) if matches!(l.pat.kind, PatKind::Binding(BindingAnnotation(ByRef::Yes, _), ..)) => {
return;
},
_ => false,
};
let mut app = Applicability::MachineApplicable;
let snip = snippet_with_context(cx, arg.span, expr.span.ctxt(), "_", &mut app).0;
let deref_count = arg_adjustments
.iter()
.take_while(|adj| matches!(adj.kind, Adjust::Deref(_)))
.count();
let (help, sugg) = if deref_count == 0 {
("try removing the `clone` call", snip.into())
} else if parent_is_suffix_expr {
("try dereferencing it", format!("({}{})", "*".repeat(deref_count), snip))
} else {
("try dereferencing it", format!("{}{}", "*".repeat(deref_count), snip))
};
span_lint_and_sugg(
cx,
CLONE_ON_COPY,
expr.span,
&format!("using `clone` on type `{}` which implements the `Copy` trait", ty),
help,
sugg,
app,
);
}
}
|
