use consts::{Constant, constant_simple, FloatWidth};
use rustc::lint::*;
use rustc::hir::*;
use utils::span_help_and_lint;
declare_lint! {
pub ZERO_DIVIDED_BY_ZERO,
Warn,
"usage of `0.0 / 0.0` to obtain NaN instead of std::f32::NaN or std::f64::NaN"
}
pub struct Pass;
impl LintPass for Pass {
fn get_lints(&self) -> LintArray {
lint_array!(ZERO_DIVIDED_BY_ZERO)
}
}
impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Pass {
fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
if_let_chain! {[
let ExprBinary(ref op, ref left, ref right) = expr.node,
let BinOp_::BiDiv = op.node,
let Some(Constant::Float(ref lhs_value, lhs_width)) = constant_simple(cx, left),
let Some(Constant::Float(ref rhs_value, rhs_width)) = constant_simple(cx, right),
Ok(0.0) == lhs_value.parse(),
Ok(0.0) == rhs_value.parse()
], {
let float_type = match (lhs_width, rhs_width) {
(FloatWidth::F64, _)
| (_, FloatWidth::F64) => "f64",
_ => "f32"
};
span_help_and_lint(cx, ZERO_DIVIDED_BY_ZERO, expr.span,
"constant division of 0.0 with 0.0 will always result in NaN",
&format!("Consider using `std::{}::NAN` if you would like a constant representing NaN", float_type));
}}
}
}