1 use crate::consts::{constant_simple, Constant};
2 use crate::utils::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};
9 /// **What it does:** Checks for `0.0 / 0.0`.
11 /// **Why is this bad?** It's less readable than `f32::NAN` or `f64::NAN`.
13 /// **Known problems:** None.
18 /// let nan = 0.0f32 / 0.0;
21 /// let nan = f32::NAN;
23 pub ZERO_DIVIDED_BY_ZERO,
25 "usage of `0.0 / 0.0` to obtain NaN instead of `f32::NAN` or `f64::NAN`"
28 declare_lint_pass!(ZeroDiv => [ZERO_DIVIDED_BY_ZERO]);
30 impl<'tcx> LateLintPass<'tcx> for ZeroDiv {
31 fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
32 // check for instances of 0.0/0.0
34 if let ExprKind::Binary(ref op, ref left, ref right) = expr.kind;
35 if let BinOpKind::Div = op.node;
36 // TODO - constant_simple does not fold many operations involving floats.
37 // That's probably fine for this lint - it's pretty unlikely that someone would
38 // do something like 0.0/(2.0 - 2.0), but it would be nice to warn on that case too.
39 if let Some(lhs_value) = constant_simple(cx, cx.typeck_results(), left);
40 if let Some(rhs_value) = constant_simple(cx, cx.typeck_results(), right);
41 if Constant::F32(0.0) == lhs_value || Constant::F64(0.0) == lhs_value;
42 if Constant::F32(0.0) == rhs_value || Constant::F64(0.0) == rhs_value;
44 // since we're about to suggest a use of f32::NAN or f64::NAN,
45 // match the precision of the literals that are given.
46 let float_type = match (lhs_value, rhs_value) {
48 | (_, Constant::F64(_)) => "f64",
55 "constant division of `0.0` with `0.0` will always result in NaN",
58 "Consider using `{}::NAN` if you would like a constant representing NaN",