1 use clippy_utils::diagnostics::span_lint;
2 use clippy_utils::ty::implements_trait;
3 use if_chain::if_chain;
4 use rustc_hir::{BinOpKind, Expr, ExprKind, UnOp};
5 use rustc_lint::{LateContext, LateLintPass, LintContext};
6 use rustc_middle::lint::in_external_macro;
7 use rustc_session::{declare_lint_pass, declare_tool_lint};
10 declare_clippy_lint! {
12 /// Checks for the usage of negated comparison operators on types which only implement
13 /// `PartialOrd` (e.g., `f64`).
15 /// ### Why is this bad?
16 /// These operators make it easy to forget that the underlying types actually allow not only three
17 /// potential Orderings (Less, Equal, Greater) but also a fourth one (Uncomparable). This is
18 /// especially easy to miss if the operator based comparison result is negated.
25 /// let not_less_or_equal = !(a <= b);
30 /// use std::cmp::Ordering;
32 /// # let b = f64::NAN;
34 /// let _not_less_or_equal = match a.partial_cmp(&b) {
35 /// None | Some(Ordering::Greater) => true,
39 #[clippy::version = "pre 1.29.0"]
40 pub NEG_CMP_OP_ON_PARTIAL_ORD,
42 "The use of negated comparison operators on partially ordered types may produce confusing code."
45 declare_lint_pass!(NoNegCompOpForPartialOrd => [NEG_CMP_OP_ON_PARTIAL_ORD]);
47 impl<'tcx> LateLintPass<'tcx> for NoNegCompOpForPartialOrd {
48 fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
50 if !in_external_macro(cx.sess(), expr.span);
51 if let ExprKind::Unary(UnOp::Not, inner) = expr.kind;
52 if let ExprKind::Binary(ref op, left, _) = inner.kind;
53 if let BinOpKind::Le | BinOpKind::Ge | BinOpKind::Lt | BinOpKind::Gt = op.node;
56 let ty = cx.typeck_results().expr_ty(left);
58 let implements_ord = {
59 if let Some(id) = cx.tcx.get_diagnostic_item(sym::Ord) {
60 implements_trait(cx, ty, id, &[])
66 let implements_partial_ord = {
67 if let Some(id) = cx.tcx.lang_items().partial_ord_trait() {
68 implements_trait(cx, ty, id, &[ty.into()])
74 if implements_partial_ord && !implements_ord {
77 NEG_CMP_OP_ON_PARTIAL_ORD,
79 "the use of negated comparison operators on partially ordered \
80 types produces code that is hard to read and refactor, please \
81 consider using the `partial_cmp` method instead, to make it \
82 clear that the two values could be incomparable",