2 use rustc::ty::{self, Ty};
4 use syntax::codemap::Span;
6 use utils::{is_automatically_derived, span_lint_and_then, match_path_old, is_copy};
8 /// **What it does:** Checks for deriving `Hash` but implementing `PartialEq`
11 /// **Why is this bad?** The implementation of these traits must agree (for
12 /// example for use with `HashMap`) so it’s probably a bad idea to use a
13 /// default-generated `Hash` implementation with an explicitly defined
14 /// `PartialEq`. In particular, the following must hold for any type:
17 /// k1 == k2 ⇒ hash(k1) == hash(k2)
20 /// **Known problems:** None.
27 /// impl PartialEq for Foo {
32 pub DERIVE_HASH_XOR_EQ,
34 "deriving `Hash` but implementing `PartialEq` explicitly"
37 /// **What it does:** Checks for explicit `Clone` implementations for `Copy`
40 /// **Why is this bad?** To avoid surprising behaviour, these traits should
41 /// agree and the behaviour of `Copy` cannot be overridden. In almost all
42 /// situations a `Copy` type should have a `Clone` implementation that does
43 /// nothing more than copy the object, which is what `#[derive(Copy, Clone)]`
46 /// **Known problems:** None.
53 /// impl Clone for Foo {
58 pub EXPL_IMPL_CLONE_ON_COPY,
60 "implementing `Clone` explicitly on `Copy` types"
65 impl LintPass for Derive {
66 fn get_lints(&self) -> LintArray {
67 lint_array!(EXPL_IMPL_CLONE_ON_COPY, DERIVE_HASH_XOR_EQ)
71 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Derive {
72 fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx Item) {
73 if let ItemImpl(_, _, _, _, Some(ref trait_ref), _, _) = item.node {
74 let ty = cx.tcx.type_of(cx.tcx.hir.local_def_id(item.id));
75 let is_automatically_derived = is_automatically_derived(&*item.attrs);
77 check_hash_peq(cx, item.span, trait_ref, ty, is_automatically_derived);
79 if !is_automatically_derived {
80 check_copy_clone(cx, item, trait_ref, ty);
86 /// Implementation of the `DERIVE_HASH_XOR_EQ` lint.
87 fn check_hash_peq<'a, 'tcx>(
88 cx: &LateContext<'a, 'tcx>,
92 hash_is_automatically_derived: bool
95 match_path_old(&trait_ref.path, &paths::HASH),
96 let Some(peq_trait_def_id) = cx.tcx.lang_items.eq_trait()
98 // Look for the PartialEq implementations for `ty`
99 cx.tcx.for_each_relevant_impl(peq_trait_def_id, ty, |impl_id| {
100 let peq_is_automatically_derived = is_automatically_derived(&cx.tcx.get_attrs(impl_id));
102 if peq_is_automatically_derived == hash_is_automatically_derived {
106 let trait_ref = cx.tcx.impl_trait_ref(impl_id).expect("must be a trait implementation");
108 // Only care about `impl PartialEq<Foo> for Foo`
109 // For `impl PartialEq<B> for A, input_types is [A, B]
110 if trait_ref.substs.type_at(1) == ty {
111 let mess = if peq_is_automatically_derived {
112 "you are implementing `Hash` explicitly but have derived `PartialEq`"
114 "you are deriving `Hash` but have implemented `PartialEq` explicitly"
118 cx, DERIVE_HASH_XOR_EQ, span,
121 if let Some(node_id) = cx.tcx.hir.as_local_node_id(impl_id) {
123 cx.tcx.hir.span(node_id),
124 "`PartialEq` implemented here"
133 /// Implementation of the `EXPL_IMPL_CLONE_ON_COPY` lint.
134 fn check_copy_clone<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, item: &Item, trait_ref: &TraitRef, ty: Ty<'tcx>) {
135 if match_path_old(&trait_ref.path, &paths::CLONE_TRAIT) {
136 if !is_copy(cx, ty) {
141 ty::TyAdt(def, _) if def.is_union() => return,
143 // Some types are not Clone by default but could be cloned “by hand” if necessary
144 ty::TyAdt(def, substs) => {
145 for variant in &def.variants {
146 for field in &variant.fields {
147 match field.ty(cx.tcx, substs).sty {
148 ty::TyArray(_, size) if size > 32 => {
154 ty::TyTuple(tys, _) if tys.len() > 12 => {
165 span_lint_and_then(cx,
166 EXPL_IMPL_CLONE_ON_COPY,
168 "you are implementing `Clone` explicitly on a `Copy` type",
169 |db| { db.span_note(item.span, "consider deriving `Clone` or removing `Copy`"); });