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)
73 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Derive {
74 fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx Item) {
75 if let ItemKind::Impl(_, _, _, _, Some(ref trait_ref), _, _) = item.node {
76 let ty = cx.tcx.type_of(cx.tcx.hir().local_def_id(item.id));
77 let is_automatically_derived = is_automatically_derived(&*item.attrs);
79 check_hash_peq(cx, item.span, trait_ref, ty, is_automatically_derived);
81 if !is_automatically_derived {
82 check_copy_clone(cx, item, trait_ref, ty);
88 /// Implementation of the `DERIVE_HASH_XOR_EQ` lint.
89 fn check_hash_peq<'a, 'tcx>(
90 cx: &LateContext<'a, 'tcx>,
94 hash_is_automatically_derived: bool,
97 if match_path(&trait_ref.path, &paths::HASH);
98 if let Some(peq_trait_def_id) = cx.tcx.lang_items().eq_trait();
100 // Look for the PartialEq implementations for `ty`
101 cx.tcx.for_each_relevant_impl(peq_trait_def_id, ty, |impl_id| {
102 let peq_is_automatically_derived = is_automatically_derived(&cx.tcx.get_attrs(impl_id));
104 if peq_is_automatically_derived == hash_is_automatically_derived {
108 let trait_ref = cx.tcx.impl_trait_ref(impl_id).expect("must be a trait implementation");
110 // Only care about `impl PartialEq<Foo> for Foo`
111 // For `impl PartialEq<B> for A, input_types is [A, B]
112 if trait_ref.substs.type_at(1) == ty {
113 let mess = if peq_is_automatically_derived {
114 "you are implementing `Hash` explicitly but have derived `PartialEq`"
116 "you are deriving `Hash` but have implemented `PartialEq` explicitly"
120 cx, DERIVE_HASH_XOR_EQ, span,
123 if let Some(node_id) = cx.tcx.hir().as_local_node_id(impl_id) {
125 cx.tcx.hir().span(node_id),
126 "`PartialEq` implemented here"
136 /// Implementation of the `EXPL_IMPL_CLONE_ON_COPY` lint.
137 fn check_copy_clone<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, item: &Item, trait_ref: &TraitRef, ty: Ty<'tcx>) {
138 if match_path(&trait_ref.path, &paths::CLONE_TRAIT) {
139 if !is_copy(cx, ty) {
144 ty::Adt(def, _) if def.is_union() => return,
146 // Some types are not Clone by default but could be cloned “by hand” if necessary
147 ty::Adt(def, substs) => {
148 for variant in &def.variants {
149 for field in &variant.fields {
150 if let ty::FnDef(..) = field.ty(cx.tcx, substs).sty {
154 for subst in substs {
155 if let ty::subst::UnpackedKind::Type(subst) = subst.unpack() {
156 if let ty::Param(_) = subst.sty {
168 EXPL_IMPL_CLONE_ON_COPY,
170 "you are implementing `Clone` explicitly on a `Copy` type",
172 db.span_note(item.span, "consider deriving `Clone` or removing `Copy`");