| use clippy_utils::diagnostics::span_lint_hir; |
| use if_chain::if_chain; |
| use rustc_hir::{Impl, Item, ItemKind}; |
| use rustc_lint::{LateContext, LateLintPass}; |
| use rustc_session::{declare_lint_pass, declare_tool_lint}; |
| use rustc_span::sym; |
| |
| declare_clippy_lint! { |
| /// ### What it does |
| /// Checks for manual re-implementations of `PartialEq::ne`. |
| /// |
| /// ### Why is this bad? |
| /// `PartialEq::ne` is required to always return the |
| /// negated result of `PartialEq::eq`, which is exactly what the default |
| /// implementation does. Therefore, there should never be any need to |
| /// re-implement it. |
| /// |
| /// ### Example |
| /// ```no_run |
| /// struct Foo; |
| /// |
| /// impl PartialEq for Foo { |
| /// fn eq(&self, other: &Foo) -> bool { true } |
| /// fn ne(&self, other: &Foo) -> bool { !(self == other) } |
| /// } |
| /// ``` |
| #[clippy::version = "pre 1.29.0"] |
| pub PARTIALEQ_NE_IMPL, |
| complexity, |
| "re-implementing `PartialEq::ne`" |
| } |
| |
| declare_lint_pass!(PartialEqNeImpl => [PARTIALEQ_NE_IMPL]); |
| |
| impl<'tcx> LateLintPass<'tcx> for PartialEqNeImpl { |
| fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx Item<'_>) { |
| if_chain! { |
| if let ItemKind::Impl(Impl { of_trait: Some(ref trait_ref), items: impl_items, .. }) = item.kind; |
| if !cx.tcx.has_attr(item.owner_id, sym::automatically_derived); |
| if let Some(eq_trait) = cx.tcx.lang_items().eq_trait(); |
| if trait_ref.path.res.def_id() == eq_trait; |
| then { |
| for impl_item in *impl_items { |
| if impl_item.ident.name == sym::ne { |
| span_lint_hir( |
| cx, |
| PARTIALEQ_NE_IMPL, |
| impl_item.id.hir_id(), |
| impl_item.span, |
| "re-implementing `PartialEq::ne` is unnecessary", |
| ); |
| } |
| } |
| } |
| }; |
| } |
| } |