1 use crate::utils::{is_automatically_derived, span_lint_node};
2 use if_chain::if_chain;
4 use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
5 use rustc::{declare_tool_lint, lint_array};
8 /// **What it does:** Checks for manual re-implementations of `PartialEq::ne`.
10 /// **Why is this bad?** `PartialEq::ne` is required to always return the
11 /// negated result of `PartialEq::eq`, which is exactly what the default
12 /// implementation does. Therefore, there should never be any need to
15 /// **Known problems:** None.
21 /// impl PartialEq for Foo {
22 /// fn eq(&self, other: &Foo) -> bool { ... }
23 /// fn ne(&self, other: &Foo) -> bool { !(self == other) }
26 pub PARTIALEQ_NE_IMPL,
28 "re-implementing `PartialEq::ne`"
31 #[derive(Clone, Copy)]
34 impl LintPass for Pass {
35 fn get_lints(&self) -> LintArray {
36 lint_array!(PARTIALEQ_NE_IMPL)
39 fn name(&self) -> &'static str {
44 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Pass {
45 fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx Item) {
47 if let ItemKind::Impl(_, _, _, _, Some(ref trait_ref), _, ref impl_items) = item.node;
48 if !is_automatically_derived(&*item.attrs);
49 if let Some(eq_trait) = cx.tcx.lang_items().eq_trait();
50 if trait_ref.path.def.def_id() == eq_trait;
52 for impl_item in impl_items {
53 if impl_item.ident.name == "ne" {
59 "re-implementing `PartialEq::ne` is unnecessary",