1 use clippy_utils::consts::{constant_simple, Constant};
2 use clippy_utils::diagnostics::span_lint_and_help;
3 use if_chain::if_chain;
4 use rustc_hir::{BinOpKind, Expr, ExprKind};
5 use rustc_lint::{LateContext, LateLintPass};
6 use rustc_session::{declare_lint_pass, declare_tool_lint};
10 /// Checks for `0.0 / 0.0`.
12 /// ### Why is this bad?
13 /// It's less readable than `f32::NAN` or `f64::NAN`.
18 /// let nan = 0.0f32 / 0.0;
21 /// let nan = f32::NAN;
23 #[clippy::version = "pre 1.29.0"]
24 pub ZERO_DIVIDED_BY_ZERO,
26 "usage of `0.0 / 0.0` to obtain NaN instead of `f32::NAN` or `f64::NAN`"
29 declare_lint_pass!(ZeroDiv => [ZERO_DIVIDED_BY_ZERO]);
31 impl<'tcx> LateLintPass<'tcx> for ZeroDiv {
32 fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
33 // check for instances of 0.0/0.0
35 if let ExprKind::Binary(ref op, left, right) = expr.kind;
36 if op.node == BinOpKind::Div;
37 // TODO - constant_simple does not fold many operations involving floats.
38 // That's probably fine for this lint - it's pretty unlikely that someone would
39 // do something like 0.0/(2.0 - 2.0), but it would be nice to warn on that case too.
40 if let Some(lhs_value) = constant_simple(cx, cx.typeck_results(), left);
41 if let Some(rhs_value) = constant_simple(cx, cx.typeck_results(), right);
42 if Constant::F32(0.0) == lhs_value || Constant::F64(0.0) == lhs_value;
43 if Constant::F32(0.0) == rhs_value || Constant::F64(0.0) == rhs_value;
45 // since we're about to suggest a use of f32::NAN or f64::NAN,
46 // match the precision of the literals that are given.
47 let float_type = match (lhs_value, rhs_value) {
49 | (_, Constant::F64(_)) => "f64",
56 "constant division of `0.0` with `0.0` will always result in NaN",
59 "consider using `{}::NAN` if you would like a constant representing NaN",