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.
19 pub ZERO_DIVIDED_BY_ZERO,
21 "usage of `0.0 / 0.0` to obtain NaN instead of `f32::NAN` or `f64::NAN`"
24 declare_lint_pass!(ZeroDiv => [ZERO_DIVIDED_BY_ZERO]);
26 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for ZeroDiv {
27 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr<'_>) {
28 // check for instances of 0.0/0.0
30 if let ExprKind::Binary(ref op, ref left, ref right) = expr.kind;
31 if let BinOpKind::Div = op.node;
32 // TODO - constant_simple does not fold many operations involving floats.
33 // That's probably fine for this lint - it's pretty unlikely that someone would
34 // do something like 0.0/(2.0 - 2.0), but it would be nice to warn on that case too.
35 if let Some(lhs_value) = constant_simple(cx, cx.tables, left);
36 if let Some(rhs_value) = constant_simple(cx, cx.tables, right);
37 if Constant::F32(0.0) == lhs_value || Constant::F64(0.0) == lhs_value;
38 if Constant::F32(0.0) == rhs_value || Constant::F64(0.0) == rhs_value;
40 // since we're about to suggest a use of f32::NAN or f64::NAN,
41 // match the precision of the literals that are given.
42 let float_type = match (lhs_value, rhs_value) {
44 | (_, Constant::F64(_)) => "f64",
51 "constant division of `0.0` with `0.0` will always result in NaN",
54 "Consider using `{}::NAN` if you would like a constant representing NaN",