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
|
use clippy_utils::consts::{ConstEvalCtxt, Constant};
use clippy_utils::diagnostics::span_lint_and_then;
use clippy_utils::sext;
use rustc_hir::{BinOpKind, Expr, ExprKind, Node};
use rustc_lint::LateContext;
use rustc_middle::ty::{self, Ty};
use std::fmt::Display;
use super::MODULO_ARITHMETIC;
pub(super) fn check<'tcx>(
cx: &LateContext<'tcx>,
e: &'tcx Expr<'_>,
op: BinOpKind,
lhs: &'tcx Expr<'_>,
rhs: &'tcx Expr<'_>,
allow_comparison_to_zero: bool,
) {
if op == BinOpKind::Rem {
if allow_comparison_to_zero && used_in_comparison_with_zero(cx, e) {
return;
}
let lhs_operand = analyze_operand(lhs, cx, e);
let rhs_operand = analyze_operand(rhs, cx, e);
if let Some(lhs_operand) = lhs_operand
&& let Some(rhs_operand) = rhs_operand
{
check_const_operands(cx, e, &lhs_operand, &rhs_operand);
} else {
check_non_const_operands(cx, e, lhs);
}
}
}
fn used_in_comparison_with_zero(cx: &LateContext<'_>, expr: &Expr<'_>) -> bool {
let Node::Expr(parent_expr) = cx.tcx.parent_hir_node(expr.hir_id) else {
return false;
};
let ExprKind::Binary(op, lhs, rhs) = parent_expr.kind else {
return false;
};
if op.node == BinOpKind::Eq || op.node == BinOpKind::Ne {
let ecx = ConstEvalCtxt::new(cx);
matches!(ecx.eval(lhs), Some(Constant::Int(0))) || matches!(ecx.eval(rhs), Some(Constant::Int(0)))
} else {
false
}
}
struct OperandInfo {
string_representation: Option<String>,
is_negative: bool,
is_integral: bool,
}
fn analyze_operand(operand: &Expr<'_>, cx: &LateContext<'_>, expr: &Expr<'_>) -> Option<OperandInfo> {
match ConstEvalCtxt::new(cx).eval(operand) {
Some(Constant::Int(v)) => match *cx.typeck_results().expr_ty(expr).kind() {
ty::Int(ity) => {
let value = sext(cx.tcx, v, ity);
return Some(OperandInfo {
string_representation: Some(value.to_string()),
is_negative: value < 0,
is_integral: true,
});
},
ty::Uint(_) => {
return Some(OperandInfo {
string_representation: None,
is_negative: false,
is_integral: true,
});
},
_ => {},
},
// FIXME(f16_f128): add when casting is available on all platforms
Some(Constant::F32(f)) => {
return Some(floating_point_operand_info(&f));
},
Some(Constant::F64(f)) => {
return Some(floating_point_operand_info(&f));
},
_ => {},
}
None
}
fn floating_point_operand_info<T: Display + PartialOrd + From<f32>>(f: &T) -> OperandInfo {
OperandInfo {
string_representation: Some(format!("{:.3}", *f)),
is_negative: *f < 0.0.into(),
is_integral: false,
}
}
fn might_have_negative_value(t: Ty<'_>) -> bool {
t.is_signed() || t.is_floating_point()
}
fn check_const_operands<'tcx>(
cx: &LateContext<'tcx>,
expr: &'tcx Expr<'_>,
lhs_operand: &OperandInfo,
rhs_operand: &OperandInfo,
) {
if lhs_operand.is_negative ^ rhs_operand.is_negative {
span_lint_and_then(
cx,
MODULO_ARITHMETIC,
expr.span,
format!(
"you are using modulo operator on constants with different signs: `{} % {}`",
lhs_operand.string_representation.as_ref().unwrap(),
rhs_operand.string_representation.as_ref().unwrap()
),
|diag| {
diag.note("double check for expected result especially when interoperating with different languages");
if lhs_operand.is_integral {
diag.note("or consider using `rem_euclid` or similar function");
}
},
);
}
}
fn check_non_const_operands<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>, operand: &Expr<'_>) {
let operand_type = cx.typeck_results().expr_ty(operand);
if might_have_negative_value(operand_type) {
span_lint_and_then(
cx,
MODULO_ARITHMETIC,
expr.span,
"you are using modulo operator on types that might have different signs",
|diag| {
diag.note("double check for expected result especially when interoperating with different languages");
if operand_type.is_integral() {
diag.note("or consider using `rem_euclid` or similar function");
}
},
);
}
}
|
