1 use clippy_utils::diagnostics::span_lint_hir;
2 use if_chain::if_chain;
3 use rustc_hir::{Impl, Item, ItemKind};
4 use rustc_lint::{LateContext, LateLintPass};
5 use rustc_session::{declare_lint_pass, declare_tool_lint};
10 /// Checks for manual re-implementations of `PartialEq::ne`.
12 /// ### Why is this bad?
13 /// `PartialEq::ne` is required to always return the
14 /// negated result of `PartialEq::eq`, which is exactly what the default
15 /// implementation does. Therefore, there should never be any need to
22 /// impl PartialEq for Foo {
23 /// fn eq(&self, other: &Foo) -> bool { true }
24 /// fn ne(&self, other: &Foo) -> bool { !(self == other) }
27 #[clippy::version = "pre 1.29.0"]
28 pub PARTIALEQ_NE_IMPL,
30 "re-implementing `PartialEq::ne`"
33 declare_lint_pass!(PartialEqNeImpl => [PARTIALEQ_NE_IMPL]);
35 impl<'tcx> LateLintPass<'tcx> for PartialEqNeImpl {
36 fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx Item<'_>) {
38 if let ItemKind::Impl(Impl { of_trait: Some(ref trait_ref), items: impl_items, .. }) = item.kind;
39 if !cx.tcx.has_attr(item.def_id.to_def_id(), sym::automatically_derived);
40 if let Some(eq_trait) = cx.tcx.lang_items().eq_trait();
41 if trait_ref.path.res.def_id() == eq_trait;
43 for impl_item in *impl_items {
44 if impl_item.ident.name == sym::ne {
48 impl_item.id.hir_id(),
50 "re-implementing `PartialEq::ne` is unnecessary",