1 files changed, 28 insertions, 0 deletions
diff --git a/src/tools/clippy/clippy_lints/src/casts/cast_nan_to_int.rs b/src/tools/clippy/clippy_lints/src/casts/cast_nan_to_int.rs
new file mode 100644
index 000000000..322dc41b3
--- /dev/null
+++ b/src/tools/clippy/clippy_lints/src/casts/cast_nan_to_int.rs
@@ -0,0 +1,28 @@
+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,
+    }
+}