1 use clippy_utils::diagnostics::{span_lint_and_help, span_lint_and_note, span_lint_and_sugg, span_lint_and_then};
2 use clippy_utils::paths;
3 use clippy_utils::ty::{implements_trait, implements_trait_with_env, is_copy};
4 use clippy_utils::{is_lint_allowed, match_def_path};
5 use if_chain::if_chain;
6 use rustc_errors::Applicability;
7 use rustc_hir::intravisit::{walk_expr, walk_fn, walk_item, FnKind, Visitor};
9 self as hir, BlockCheckMode, BodyId, Expr, ExprKind, FnDecl, HirId, Impl, Item, ItemKind, UnsafeSource, Unsafety,
11 use rustc_lint::{LateContext, LateLintPass};
12 use rustc_middle::hir::nested_filter;
13 use rustc_middle::ty::subst::GenericArg;
14 use rustc_middle::ty::{self, BoundConstness, ImplPolarity, ParamEnv, PredicateKind, TraitPredicate, TraitRef, Ty};
15 use rustc_session::{declare_lint_pass, declare_tool_lint};
16 use rustc_span::source_map::Span;
19 declare_clippy_lint! {
21 /// Checks for deriving `Hash` but implementing `PartialEq`
22 /// explicitly or vice versa.
24 /// ### Why is this bad?
25 /// The implementation of these traits must agree (for
26 /// example for use with `HashMap`) so it’s probably a bad idea to use a
27 /// default-generated `Hash` implementation with an explicitly defined
28 /// `PartialEq`. In particular, the following must hold for any type:
31 /// k1 == k2 ⇒ hash(k1) == hash(k2)
39 /// impl PartialEq for Foo {
43 #[clippy::version = "pre 1.29.0"]
44 pub DERIVE_HASH_XOR_EQ,
46 "deriving `Hash` but implementing `PartialEq` explicitly"
49 declare_clippy_lint! {
51 /// Checks for deriving `Ord` but implementing `PartialOrd`
52 /// explicitly or vice versa.
54 /// ### Why is this bad?
55 /// The implementation of these traits must agree (for
56 /// example for use with `sort`) so it’s probably a bad idea to use a
57 /// default-generated `Ord` implementation with an explicitly defined
58 /// `PartialOrd`. In particular, the following must hold for any type
59 /// implementing `Ord`:
62 /// k1.cmp(&k2) == k1.partial_cmp(&k2).unwrap()
67 /// #[derive(Ord, PartialEq, Eq)]
70 /// impl PartialOrd for Foo {
76 /// #[derive(PartialEq, Eq)]
79 /// impl PartialOrd for Foo {
80 /// fn partial_cmp(&self, other: &Foo) -> Option<Ordering> {
81 /// Some(self.cmp(other))
85 /// impl Ord for Foo {
89 /// or, if you don't need a custom ordering:
91 /// #[derive(Ord, PartialOrd, PartialEq, Eq)]
94 #[clippy::version = "1.47.0"]
95 pub DERIVE_ORD_XOR_PARTIAL_ORD,
97 "deriving `Ord` but implementing `PartialOrd` explicitly"
100 declare_clippy_lint! {
102 /// Checks for explicit `Clone` implementations for `Copy`
105 /// ### Why is this bad?
106 /// To avoid surprising behavior, these traits should
107 /// agree and the behavior of `Copy` cannot be overridden. In almost all
108 /// situations a `Copy` type should have a `Clone` implementation that does
109 /// nothing more than copy the object, which is what `#[derive(Copy, Clone)]`
117 /// impl Clone for Foo {
121 #[clippy::version = "pre 1.29.0"]
122 pub EXPL_IMPL_CLONE_ON_COPY,
124 "implementing `Clone` explicitly on `Copy` types"
127 declare_clippy_lint! {
129 /// Checks for deriving `serde::Deserialize` on a type that
130 /// has methods using `unsafe`.
132 /// ### Why is this bad?
133 /// Deriving `serde::Deserialize` will create a constructor
134 /// that may violate invariants hold by another constructor.
138 /// use serde::Deserialize;
140 /// #[derive(Deserialize)]
146 /// pub fn new() -> Self {
150 /// pub unsafe fn parts() -> (&str, &str) {
151 /// // assumes invariants hold
155 #[clippy::version = "1.45.0"]
156 pub UNSAFE_DERIVE_DESERIALIZE,
158 "deriving `serde::Deserialize` on a type that has methods using `unsafe`"
161 declare_clippy_lint! {
163 /// Checks for types that derive `PartialEq` and could implement `Eq`.
165 /// ### Why is this bad?
166 /// If a type `T` derives `PartialEq` and all of its members implement `Eq`,
167 /// then `T` can always implement `Eq`. Implementing `Eq` allows `T` to be used
168 /// in APIs that require `Eq` types. It also allows structs containing `T` to derive
173 /// #[derive(PartialEq)]
176 /// i_am_eq_too: Vec<String>,
181 /// #[derive(PartialEq, Eq)]
184 /// i_am_eq_too: Vec<String>,
187 #[clippy::version = "1.62.0"]
188 pub DERIVE_PARTIAL_EQ_WITHOUT_EQ,
190 "deriving `PartialEq` on a type that can implement `Eq`, without implementing `Eq`"
193 declare_lint_pass!(Derive => [
194 EXPL_IMPL_CLONE_ON_COPY,
196 DERIVE_ORD_XOR_PARTIAL_ORD,
197 UNSAFE_DERIVE_DESERIALIZE,
198 DERIVE_PARTIAL_EQ_WITHOUT_EQ
201 impl<'tcx> LateLintPass<'tcx> for Derive {
202 fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx Item<'_>) {
203 if let ItemKind::Impl(Impl {
204 of_trait: Some(ref trait_ref),
208 let ty = cx.tcx.type_of(item.def_id);
209 let is_automatically_derived = cx.tcx.has_attr(item.def_id.to_def_id(), sym::automatically_derived);
211 check_hash_peq(cx, item.span, trait_ref, ty, is_automatically_derived);
212 check_ord_partial_ord(cx, item.span, trait_ref, ty, is_automatically_derived);
214 if is_automatically_derived {
215 check_unsafe_derive_deserialize(cx, item, trait_ref, ty);
216 check_partial_eq_without_eq(cx, item.span, trait_ref, ty);
218 check_copy_clone(cx, item, trait_ref, ty);
224 /// Implementation of the `DERIVE_HASH_XOR_EQ` lint.
225 fn check_hash_peq<'tcx>(
226 cx: &LateContext<'tcx>,
228 trait_ref: &hir::TraitRef<'_>,
230 hash_is_automatically_derived: bool,
233 if let Some(peq_trait_def_id) = cx.tcx.lang_items().eq_trait();
234 if let Some(def_id) = trait_ref.trait_def_id();
235 if cx.tcx.is_diagnostic_item(sym::Hash, def_id);
237 // Look for the PartialEq implementations for `ty`
238 cx.tcx.for_each_relevant_impl(peq_trait_def_id, ty, |impl_id| {
239 let peq_is_automatically_derived = cx.tcx.has_attr(impl_id, sym::automatically_derived);
241 if peq_is_automatically_derived == hash_is_automatically_derived {
245 let trait_ref = cx.tcx.impl_trait_ref(impl_id).expect("must be a trait implementation");
247 // Only care about `impl PartialEq<Foo> for Foo`
248 // For `impl PartialEq<B> for A, input_types is [A, B]
249 if trait_ref.substs.type_at(1) == ty {
250 let mess = if peq_is_automatically_derived {
251 "you are implementing `Hash` explicitly but have derived `PartialEq`"
253 "you are deriving `Hash` but have implemented `PartialEq` explicitly"
262 if let Some(local_def_id) = impl_id.as_local() {
263 let hir_id = cx.tcx.hir().local_def_id_to_hir_id(local_def_id);
265 cx.tcx.hir().span(hir_id),
266 "`PartialEq` implemented here"
277 /// Implementation of the `DERIVE_ORD_XOR_PARTIAL_ORD` lint.
278 fn check_ord_partial_ord<'tcx>(
279 cx: &LateContext<'tcx>,
281 trait_ref: &hir::TraitRef<'_>,
283 ord_is_automatically_derived: bool,
286 if let Some(ord_trait_def_id) = cx.tcx.get_diagnostic_item(sym::Ord);
287 if let Some(partial_ord_trait_def_id) = cx.tcx.lang_items().partial_ord_trait();
288 if let Some(def_id) = &trait_ref.trait_def_id();
289 if *def_id == ord_trait_def_id;
291 // Look for the PartialOrd implementations for `ty`
292 cx.tcx.for_each_relevant_impl(partial_ord_trait_def_id, ty, |impl_id| {
293 let partial_ord_is_automatically_derived = cx.tcx.has_attr(impl_id, sym::automatically_derived);
295 if partial_ord_is_automatically_derived == ord_is_automatically_derived {
299 let trait_ref = cx.tcx.impl_trait_ref(impl_id).expect("must be a trait implementation");
301 // Only care about `impl PartialOrd<Foo> for Foo`
302 // For `impl PartialOrd<B> for A, input_types is [A, B]
303 if trait_ref.substs.type_at(1) == ty {
304 let mess = if partial_ord_is_automatically_derived {
305 "you are implementing `Ord` explicitly but have derived `PartialOrd`"
307 "you are deriving `Ord` but have implemented `PartialOrd` explicitly"
312 DERIVE_ORD_XOR_PARTIAL_ORD,
316 if let Some(local_def_id) = impl_id.as_local() {
317 let hir_id = cx.tcx.hir().local_def_id_to_hir_id(local_def_id);
319 cx.tcx.hir().span(hir_id),
320 "`PartialOrd` implemented here"
331 /// Implementation of the `EXPL_IMPL_CLONE_ON_COPY` lint.
332 fn check_copy_clone<'tcx>(cx: &LateContext<'tcx>, item: &Item<'_>, trait_ref: &hir::TraitRef<'_>, ty: Ty<'tcx>) {
333 let clone_id = match cx.tcx.lang_items().clone_trait() {
334 Some(id) if trait_ref.trait_def_id() == Some(id) => id,
337 let copy_id = match cx.tcx.lang_items().copy_trait() {
341 let (ty_adt, ty_subs) = match *ty.kind() {
342 // Unions can't derive clone.
343 ty::Adt(adt, subs) if !adt.is_union() => (adt, subs),
346 // If the current self type doesn't implement Copy (due to generic constraints), search to see if
347 // there's a Copy impl for any instance of the adt.
348 if !is_copy(cx, ty) {
349 if ty_subs.non_erasable_generics().next().is_some() {
350 let has_copy_impl = cx.tcx.all_local_trait_impls(()).get(©_id).map_or(false, |impls| {
353 .any(|&id| matches!(cx.tcx.type_of(id).kind(), ty::Adt(adt, _) if ty_adt.did() == adt.did()))
362 // Derive constrains all generic types to requiring Clone. Check if any type is not constrained for
364 if ty_subs.types().any(|ty| !implements_trait(cx, ty, clone_id, &[])) {
370 EXPL_IMPL_CLONE_ON_COPY,
372 "you are implementing `Clone` explicitly on a `Copy` type",
374 "consider deriving `Clone` or removing `Copy`",
378 /// Implementation of the `UNSAFE_DERIVE_DESERIALIZE` lint.
379 fn check_unsafe_derive_deserialize<'tcx>(
380 cx: &LateContext<'tcx>,
382 trait_ref: &hir::TraitRef<'_>,
385 fn has_unsafe<'tcx>(cx: &LateContext<'tcx>, item: &'tcx Item<'_>) -> bool {
386 let mut visitor = UnsafeVisitor { cx, has_unsafe: false };
387 walk_item(&mut visitor, item);
392 if let Some(trait_def_id) = trait_ref.trait_def_id();
393 if match_def_path(cx, trait_def_id, &paths::SERDE_DESERIALIZE);
394 if let ty::Adt(def, _) = ty.kind();
395 if let Some(local_def_id) = def.did().as_local();
396 let adt_hir_id = cx.tcx.hir().local_def_id_to_hir_id(local_def_id);
397 if !is_lint_allowed(cx, UNSAFE_DERIVE_DESERIALIZE, adt_hir_id);
398 if cx.tcx.inherent_impls(def.did())
400 .map(|imp_did| cx.tcx.hir().expect_item(imp_did.expect_local()))
401 .any(|imp| has_unsafe(cx, imp));
405 UNSAFE_DERIVE_DESERIALIZE,
407 "you are deriving `serde::Deserialize` on a type that has methods using `unsafe`",
409 "consider implementing `serde::Deserialize` manually. See https://serde.rs/impl-deserialize.html"
415 struct UnsafeVisitor<'a, 'tcx> {
416 cx: &'a LateContext<'tcx>,
420 impl<'tcx> Visitor<'tcx> for UnsafeVisitor<'_, 'tcx> {
421 type NestedFilter = nested_filter::All;
423 fn visit_fn(&mut self, kind: FnKind<'tcx>, decl: &'tcx FnDecl<'_>, body_id: BodyId, span: Span, id: HirId) {
429 if let Some(header) = kind.header();
430 if header.unsafety == Unsafety::Unsafe;
432 self.has_unsafe = true;
436 walk_fn(self, kind, decl, body_id, span, id);
439 fn visit_expr(&mut self, expr: &'tcx Expr<'_>) {
444 if let ExprKind::Block(block, _) = expr.kind {
445 if block.rules == BlockCheckMode::UnsafeBlock(UnsafeSource::UserProvided) {
446 self.has_unsafe = true;
450 walk_expr(self, expr);
453 fn nested_visit_map(&mut self) -> Self::Map {
458 /// Implementation of the `DERIVE_PARTIAL_EQ_WITHOUT_EQ` lint.
459 fn check_partial_eq_without_eq<'tcx>(cx: &LateContext<'tcx>, span: Span, trait_ref: &hir::TraitRef<'_>, ty: Ty<'tcx>) {
461 if let ty::Adt(adt, substs) = ty.kind();
462 if let Some(eq_trait_def_id) = cx.tcx.get_diagnostic_item(sym::Eq);
463 if let Some(peq_trait_def_id) = cx.tcx.get_diagnostic_item(sym::PartialEq);
464 if let Some(def_id) = trait_ref.trait_def_id();
465 if cx.tcx.is_diagnostic_item(sym::PartialEq, def_id);
466 // New `ParamEnv` replacing `T: PartialEq` with `T: Eq`
467 let param_env = ParamEnv::new(
468 cx.tcx.mk_predicates(cx.param_env.caller_bounds().iter().map(|p| {
470 match kind.skip_binder() {
471 PredicateKind::Trait(p)
472 if p.trait_ref.def_id == peq_trait_def_id
473 && p.trait_ref.substs.get(0) == p.trait_ref.substs.get(1)
474 && matches!(p.trait_ref.self_ty().kind(), ty::Param(_))
475 && p.constness == BoundConstness::NotConst
476 && p.polarity == ImplPolarity::Positive =>
478 cx.tcx.mk_predicate(kind.rebind(PredicateKind::Trait(TraitPredicate {
479 trait_ref: TraitRef::new(
481 cx.tcx.mk_substs([GenericArg::from(p.trait_ref.self_ty())].into_iter()),
483 constness: BoundConstness::NotConst,
484 polarity: ImplPolarity::Positive,
490 cx.param_env.reveal(),
491 cx.param_env.constness(),
493 if !implements_trait_with_env(cx.tcx, param_env, ty, eq_trait_def_id, substs);
495 // If all of our fields implement `Eq`, we can implement `Eq` too
496 for variant in adt.variants() {
497 for field in &variant.fields {
498 let ty = field.ty(cx.tcx, substs);
500 if !implements_trait(cx, ty, eq_trait_def_id, substs) {
508 DERIVE_PARTIAL_EQ_WITHOUT_EQ,
509 span.ctxt().outer_expn_data().call_site,
510 "you are deriving `PartialEq` and can implement `Eq`",
511 "consider deriving `Eq` as well",
512 "PartialEq, Eq".to_string(),
513 Applicability::MachineApplicable,