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use consts::{constant_simple, Constant, 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_chain! {
if let ExprBinary(ref op, ref left, ref right) = expr.node;
if let BinOp_::BiDiv = op.node;
if let Some(Constant::Float(ref lhs_value, lhs_width)) = constant_simple(cx, left);
if let Some(Constant::Float(ref rhs_value, rhs_width)) = constant_simple(cx, right);
if Ok(0.0) == lhs_value.parse();
if Ok(0.0) == rhs_value.parse();
then {
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,
),
);
}
}
}
}