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;
4 use rustc::declare_lint_pass;
6 use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
7 use rustc::ty::{self, Ty};
8 use rustc_session::declare_tool_lint;
9 use syntax::source_map::Span;
11 declare_clippy_lint! {
12 /// **What it does:** Checks for deriving `Hash` but implementing `PartialEq`
13 /// explicitly or vice versa.
15 /// **Why is this bad?** The implementation of these traits must agree (for
16 /// example for use with `HashMap`) so it’s probably a bad idea to use a
17 /// default-generated `Hash` implementation with an explicitly defined
18 /// `PartialEq`. In particular, the following must hold for any type:
21 /// k1 == k2 ⇒ hash(k1) == hash(k2)
24 /// **Known problems:** None.
31 /// impl PartialEq for Foo {
35 pub DERIVE_HASH_XOR_EQ,
37 "deriving `Hash` but implementing `PartialEq` explicitly"
40 declare_clippy_lint! {
41 /// **What it does:** Checks for explicit `Clone` implementations for `Copy`
44 /// **Why is this bad?** To avoid surprising behaviour, these traits should
45 /// agree and the behaviour of `Copy` cannot be overridden. In almost all
46 /// situations a `Copy` type should have a `Clone` implementation that does
47 /// nothing more than copy the object, which is what `#[derive(Copy, Clone)]`
50 /// **Known problems:** Bounds of generic types are sometimes wrong: https://github.com/rust-lang/rust/issues/26925
57 /// impl Clone for Foo {
61 pub EXPL_IMPL_CLONE_ON_COPY,
63 "implementing `Clone` explicitly on `Copy` types"
66 declare_lint_pass!(Derive => [EXPL_IMPL_CLONE_ON_COPY, DERIVE_HASH_XOR_EQ]);
68 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Derive {
69 fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx Item) {
70 if let ItemKind::Impl(_, _, _, _, Some(ref trait_ref), _, _) = item.kind {
71 let ty = cx.tcx.type_of(cx.tcx.hir().local_def_id(item.hir_id));
72 let is_automatically_derived = is_automatically_derived(&*item.attrs);
74 check_hash_peq(cx, item.span, trait_ref, ty, is_automatically_derived);
76 if !is_automatically_derived {
77 check_copy_clone(cx, item, trait_ref, ty);
83 /// Implementation of the `DERIVE_HASH_XOR_EQ` lint.
84 fn check_hash_peq<'a, 'tcx>(
85 cx: &LateContext<'a, 'tcx>,
89 hash_is_automatically_derived: bool,
92 if match_path(&trait_ref.path, &paths::HASH);
93 if let Some(peq_trait_def_id) = cx.tcx.lang_items().eq_trait();
94 if !&trait_ref.trait_def_id().is_local();
96 // Look for the PartialEq implementations for `ty`
97 cx.tcx.for_each_relevant_impl(peq_trait_def_id, ty, |impl_id| {
98 let peq_is_automatically_derived = is_automatically_derived(&cx.tcx.get_attrs(impl_id));
100 if peq_is_automatically_derived == hash_is_automatically_derived {
104 let trait_ref = cx.tcx.impl_trait_ref(impl_id).expect("must be a trait implementation");
106 // Only care about `impl PartialEq<Foo> for Foo`
107 // For `impl PartialEq<B> for A, input_types is [A, B]
108 if trait_ref.substs.type_at(1) == ty {
109 let mess = if peq_is_automatically_derived {
110 "you are implementing `Hash` explicitly but have derived `PartialEq`"
112 "you are deriving `Hash` but have implemented `PartialEq` explicitly"
116 cx, DERIVE_HASH_XOR_EQ, span,
119 if let Some(node_id) = cx.tcx.hir().as_local_hir_id(impl_id) {
121 cx.tcx.hir().span(node_id),
122 "`PartialEq` implemented here"
132 /// Implementation of the `EXPL_IMPL_CLONE_ON_COPY` lint.
133 fn check_copy_clone<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, item: &Item, trait_ref: &TraitRef, ty: Ty<'tcx>) {
134 if match_path(&trait_ref.path, &paths::CLONE_TRAIT) {
135 if !is_copy(cx, ty) {
140 ty::Adt(def, _) if def.is_union() => return,
142 // Some types are not Clone by default but could be cloned “by hand” if necessary
143 ty::Adt(def, substs) => {
144 for variant in &def.variants {
145 for field in &variant.fields {
146 if let ty::FnDef(..) = field.ty(cx.tcx, substs).kind {
150 for subst in substs {
151 if let ty::subst::GenericArgKind::Type(subst) = subst.unpack() {
152 if let ty::Param(_) = subst.kind {
164 EXPL_IMPL_CLONE_ON_COPY,
166 "you are implementing `Clone` explicitly on a `Copy` type",
168 db.span_note(item.span, "consider deriving `Clone` or removing `Copy`");