1 use crate::utils::paths;
2 use crate::utils::{is_automatically_derived, is_copy, match_path, span_lint_and_then};
3 use if_chain::if_chain;
5 use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
6 use rustc::ty::{self, Ty};
7 use rustc::{declare_tool_lint, lint_array};
8 use syntax::source_map::Span;
10 /// **What it does:** Checks for deriving `Hash` but implementing `PartialEq`
11 /// explicitly or vice versa.
13 /// **Why is this bad?** The implementation of these traits must agree (for
14 /// example for use with `HashMap`) so it’s probably a bad idea to use a
15 /// default-generated `Hash` implementation with an explicitly defined
16 /// `PartialEq`. In particular, the following must hold for any type:
19 /// k1 == k2 ⇒ hash(k1) == hash(k2)
22 /// **Known problems:** None.
29 /// impl PartialEq for Foo {
33 declare_clippy_lint! {
34 pub DERIVE_HASH_XOR_EQ,
36 "deriving `Hash` but implementing `PartialEq` explicitly"
39 /// **What it does:** Checks for explicit `Clone` implementations for `Copy`
42 /// **Why is this bad?** To avoid surprising behaviour, these traits should
43 /// agree and the behaviour of `Copy` cannot be overridden. In almost all
44 /// situations a `Copy` type should have a `Clone` implementation that does
45 /// nothing more than copy the object, which is what `#[derive(Copy, Clone)]`
48 /// **Known problems:** Bounds of generic types are sometimes wrong: https://github.com/rust-lang/rust/issues/26925
55 /// impl Clone for Foo {
59 declare_clippy_lint! {
60 pub EXPL_IMPL_CLONE_ON_COPY,
62 "implementing `Clone` explicitly on `Copy` types"
67 impl LintPass for Derive {
68 fn get_lints(&self) -> LintArray {
69 lint_array!(EXPL_IMPL_CLONE_ON_COPY, DERIVE_HASH_XOR_EQ)
72 fn name(&self) -> &'static str {
77 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Derive {
78 fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx Item) {
79 if let ItemKind::Impl(_, _, _, _, Some(ref trait_ref), _, _) = item.node {
80 let ty = cx.tcx.type_of(cx.tcx.hir().local_def_id(item.id));
81 let is_automatically_derived = is_automatically_derived(&*item.attrs);
83 check_hash_peq(cx, item.span, trait_ref, ty, is_automatically_derived);
85 if !is_automatically_derived {
86 check_copy_clone(cx, item, trait_ref, ty);
92 /// Implementation of the `DERIVE_HASH_XOR_EQ` lint.
93 fn check_hash_peq<'a, 'tcx>(
94 cx: &LateContext<'a, 'tcx>,
98 hash_is_automatically_derived: bool,
101 if match_path(&trait_ref.path, &paths::HASH);
102 if let Some(peq_trait_def_id) = cx.tcx.lang_items().eq_trait();
104 // Look for the PartialEq implementations for `ty`
105 cx.tcx.for_each_relevant_impl(peq_trait_def_id, ty, |impl_id| {
106 let peq_is_automatically_derived = is_automatically_derived(&cx.tcx.get_attrs(impl_id));
108 if peq_is_automatically_derived == hash_is_automatically_derived {
112 let trait_ref = cx.tcx.impl_trait_ref(impl_id).expect("must be a trait implementation");
114 // Only care about `impl PartialEq<Foo> for Foo`
115 // For `impl PartialEq<B> for A, input_types is [A, B]
116 if trait_ref.substs.type_at(1) == ty {
117 let mess = if peq_is_automatically_derived {
118 "you are implementing `Hash` explicitly but have derived `PartialEq`"
120 "you are deriving `Hash` but have implemented `PartialEq` explicitly"
124 cx, DERIVE_HASH_XOR_EQ, span,
127 if let Some(node_id) = cx.tcx.hir().as_local_node_id(impl_id) {
129 cx.tcx.hir().span(node_id),
130 "`PartialEq` implemented here"
140 /// Implementation of the `EXPL_IMPL_CLONE_ON_COPY` lint.
141 fn check_copy_clone<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, item: &Item, trait_ref: &TraitRef, ty: Ty<'tcx>) {
142 if match_path(&trait_ref.path, &paths::CLONE_TRAIT) {
143 if !is_copy(cx, ty) {
148 ty::Adt(def, _) if def.is_union() => return,
150 // Some types are not Clone by default but could be cloned “by hand” if necessary
151 ty::Adt(def, substs) => {
152 for variant in &def.variants {
153 for field in &variant.fields {
154 if let ty::FnDef(..) = field.ty(cx.tcx, substs).sty {
158 for subst in substs {
159 if let ty::subst::UnpackedKind::Type(subst) = subst.unpack() {
160 if let ty::Param(_) = subst.sty {
172 EXPL_IMPL_CLONE_ON_COPY,
174 "you are implementing `Clone` explicitly on a `Copy` type",
176 db.span_note(item.span, "consider deriving `Clone` or removing `Copy`");