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