57 lines
1.6 KiB
Rust
57 lines
1.6 KiB
Rust
use rustc::lint::*;
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use rustc::hir::*;
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use utils::{is_automatically_derived, span_lint};
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/// **What it does:** Checks for manual re-implementations of `PartialEq::ne`.
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///
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/// **Why is this bad?** `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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/// **Known problems:** None.
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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 { ... }
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/// fn ne(&self, other: &Foo) -> bool { !(self == other) }
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/// }
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/// ```
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declare_lint! {
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pub PARTIALEQ_NE_IMPL,
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Warn,
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"re-implementing `PartialEq::ne`"
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}
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#[derive(Clone, Copy)]
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pub struct Pass;
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impl LintPass for Pass {
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fn get_lints(&self) -> LintArray {
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lint_array!(PARTIALEQ_NE_IMPL)
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}
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}
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impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Pass {
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fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx Item) {
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if_let_chain! {[
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let ItemImpl(_, _, _, _, Some(ref trait_ref), _, ref impl_items) = item.node,
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!is_automatically_derived(&*item.attrs),
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let Some(eq_trait) = cx.tcx.lang_items().eq_trait(),
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trait_ref.path.def.def_id() == eq_trait
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], {
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for impl_item in impl_items {
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if impl_item.name == "ne" {
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span_lint(cx,
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PARTIALEQ_NE_IMPL,
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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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