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
|
use clippy_utils::consts::{constant_simple, Constant};
use clippy_utils::diagnostics::span_lint_and_help;
use rustc_hir::{BinOpKind, Expr, ExprKind};
use rustc_lint::{LateContext, LateLintPass};
use rustc_session::declare_lint_pass;
declare_clippy_lint! {
/// ### What it does
/// Checks for `0.0 / 0.0`.
///
/// ### Why is this bad?
/// It's less readable than `f32::NAN` or `f64::NAN`.
///
/// ### Example
/// ```no_run
/// let nan = 0.0f32 / 0.0;
/// ```
///
/// Use instead:
/// ```no_run
/// let nan = f32::NAN;
/// ```
#[clippy::version = "pre 1.29.0"]
pub ZERO_DIVIDED_BY_ZERO,
complexity,
"usage of `0.0 / 0.0` to obtain NaN instead of `f32::NAN` or `f64::NAN`"
}
declare_lint_pass!(ZeroDiv => [ZERO_DIVIDED_BY_ZERO]);
impl<'tcx> LateLintPass<'tcx> for ZeroDiv {
fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
// check for instances of 0.0/0.0
if let ExprKind::Binary(ref op, left, right) = expr.kind
&& op.node == BinOpKind::Div
// TODO - constant_simple does not fold many operations involving floats.
// That's probably fine for this lint - it's pretty unlikely that someone would
// do something like 0.0/(2.0 - 2.0), but it would be nice to warn on that case too.
&& let Some(lhs_value) = constant_simple(cx, cx.typeck_results(), left)
&& let Some(rhs_value) = constant_simple(cx, cx.typeck_results(), right)
&& (Constant::F32(0.0) == lhs_value || Constant::F64(0.0) == lhs_value)
&& (Constant::F32(0.0) == rhs_value || Constant::F64(0.0) == rhs_value)
{
// since we're about to suggest a use of f32::NAN or f64::NAN,
// match the precision of the literals that are given.
let float_type = match (lhs_value, rhs_value) {
(Constant::F64(_), _) | (_, Constant::F64(_)) => "f64",
_ => "f32",
};
span_lint_and_help(
cx,
ZERO_DIVIDED_BY_ZERO,
expr.span,
"constant division of `0.0` with `0.0` will always result in NaN",
None,
&format!("consider using `{float_type}::NAN` if you would like a constant representing NaN",),
);
}
}
}
|
