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use crate::utils::{is_automatically_derived, span_lint_hir};
use if_chain::if_chain;
use rustc_hir::*;
use rustc_lint::{LateContext, LateLintPass};
use rustc_session::{declare_lint_pass, declare_tool_lint};
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.
///
/// **Known problems:** None.
///
/// **Example:**
/// ```rust
/// struct Foo;
///
/// impl PartialEq for Foo {
/// fn eq(&self, other: &Foo) -> bool { true }
/// fn ne(&self, other: &Foo) -> bool { !(self == other) }
/// }
/// ```
pub PARTIALEQ_NE_IMPL,
complexity,
"re-implementing `PartialEq::ne`"
}
declare_lint_pass!(PartialEqNeImpl => [PARTIALEQ_NE_IMPL]);
impl<'a, 'tcx> LateLintPass<'a, 'tcx> for PartialEqNeImpl {
fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx Item<'_>) {
if_chain! {
if let ItemKind::Impl{ of_trait: Some(ref trait_ref), items: impl_items, .. } = item.kind;
if !is_automatically_derived(&*item.attrs);
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",
);
}
}
}
};
}
}
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