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use super::CAST_NAN_TO_INT;
use clippy_utils::consts::{constant, Constant};
use clippy_utils::diagnostics::span_lint_and_note;
use rustc_hir::Expr;
use rustc_lint::LateContext;
use rustc_middle::ty::Ty;
pub(super) fn check(cx: &LateContext<'_>, expr: &Expr<'_>, cast_expr: &Expr<'_>, from_ty: Ty<'_>, to_ty: Ty<'_>) {
if from_ty.is_floating_point() && to_ty.is_integral() && is_known_nan(cx, cast_expr) {
span_lint_and_note(
cx,
CAST_NAN_TO_INT,
expr.span,
&format!("casting a known NaN to {to_ty}"),
None,
"this always evaluates to 0",
);
}
}
fn is_known_nan(cx: &LateContext<'_>, e: &Expr<'_>) -> bool {
match constant(cx, cx.typeck_results(), e) {
Some((Constant::F64(n), _)) => n.is_nan(),
Some((Constant::F32(n), _)) => n.is_nan(),
_ => false,
}
}
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