1 use crate::utils::{is_automatically_derived, 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};
9 /// **What it does:** Checks for manual re-implementations of `PartialEq::ne`.
11 /// **Why is this bad?** `PartialEq::ne` is required to always return the
12 /// negated result of `PartialEq::eq`, which is exactly what the default
13 /// implementation does. Therefore, there should never be any need to
16 /// **Known problems:** None.
22 /// impl PartialEq for Foo {
23 /// fn eq(&self, other: &Foo) -> bool { true }
24 /// fn ne(&self, other: &Foo) -> bool { !(self == other) }
27 pub PARTIALEQ_NE_IMPL,
29 "re-implementing `PartialEq::ne`"
32 declare_lint_pass!(PartialEqNeImpl => [PARTIALEQ_NE_IMPL]);
34 impl<'tcx> LateLintPass<'tcx> for PartialEqNeImpl {
35 fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx Item<'_>) {
37 if let ItemKind::Impl(Impl { of_trait: Some(ref trait_ref), items: impl_items, .. }) = item.kind;
38 let attrs = cx.tcx.hir().attrs(item.hir_id());
39 if !is_automatically_derived(attrs);
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",