src/tools/clippy/clippy_lints/src/derive.rs - third_party/rust - Git at Google

 use clippy_utils::diagnostics::{span_lint_and_help, span_lint_and_note, span_lint_and_sugg, span_lint_and_then};
 use clippy_utils::ty::{implements_trait, implements_trait_with_env, is_copy};
 use clippy_utils::{has_non_exhaustive_attr, is_lint_allowed, match_def_path, paths};
 use rustc_errors::Applicability;
 use rustc_hir::def_id::DefId;
 use rustc_hir::intravisit::{walk_expr, walk_fn, walk_item, FnKind, Visitor};
 use rustc_hir::{
     self as hir, BlockCheckMode, BodyId, Expr, ExprKind, FnDecl, Impl, Item, ItemKind, UnsafeSource, Unsafety,
 };
 use rustc_lint::{LateContext, LateLintPass};
 use rustc_middle::hir::nested_filter;
 use rustc_middle::traits::Reveal;
 use rustc_middle::ty::{
     self, ClauseKind, GenericArgKind, GenericParamDefKind, ParamEnv, ToPredicate, TraitPredicate, Ty, TyCtxt,
 };
 use rustc_session::declare_lint_pass;
 use rustc_span::def_id::LocalDefId;
 use rustc_span::{sym, Span};

 declare_clippy_lint! {
     /// ### What it does
     /// Lints against manual `PartialEq` implementations for types with a derived `Hash`
     /// implementation.
     ///
     /// ### Why is this bad?
     /// The implementation of these traits must agree (for
     /// example for use with `HashMap`) so it’s probably a bad idea to use a
     /// default-generated `Hash` implementation with an explicitly defined
     /// `PartialEq`. In particular, the following must hold for any type:
     ///
     /// ```text
     /// k1 == k2 ⇒ hash(k1) == hash(k2)
     /// ```
     ///
     /// ### Example
     /// ```ignore
     /// #[derive(Hash)]
     /// struct Foo;
     ///
     /// impl PartialEq for Foo {
     ///     ...
     /// }
     /// ```
     #[clippy::version = "pre 1.29.0"]
     pub DERIVED_HASH_WITH_MANUAL_EQ,
     correctness,
     "deriving `Hash` but implementing `PartialEq` explicitly"
 }

 declare_clippy_lint! {
     /// ### What it does
     /// Lints against manual `PartialOrd` and `Ord` implementations for types with a derived `Ord`
     /// or `PartialOrd` implementation.
     ///
     /// ### Why is this bad?
     /// The implementation of these traits must agree (for
     /// example for use with `sort`) so it’s probably a bad idea to use a
     /// default-generated `Ord` implementation with an explicitly defined
     /// `PartialOrd`. In particular, the following must hold for any type
     /// implementing `Ord`:
     ///
     /// ```text
     /// k1.cmp(&k2) == k1.partial_cmp(&k2).unwrap()
     /// ```
     ///
     /// ### Example
     /// ```rust,ignore
     /// #[derive(Ord, PartialEq, Eq)]
     /// struct Foo;
     ///
     /// impl PartialOrd for Foo {
     ///     ...
     /// }
     /// ```
     /// Use instead:
     /// ```rust,ignore
     /// #[derive(PartialEq, Eq)]
     /// struct Foo;
     ///
     /// impl PartialOrd for Foo {
     ///     fn partial_cmp(&self, other: &Foo) -> Option<Ordering> {
     ///        Some(self.cmp(other))
     ///     }
     /// }
     ///
     /// impl Ord for Foo {
     ///     ...
     /// }
     /// ```
     /// or, if you don't need a custom ordering:
     /// ```rust,ignore
     /// #[derive(Ord, PartialOrd, PartialEq, Eq)]
     /// struct Foo;
     /// ```
     #[clippy::version = "1.47.0"]
     pub DERIVE_ORD_XOR_PARTIAL_ORD,
     correctness,
     "deriving `Ord` but implementing `PartialOrd` explicitly"
 }

 declare_clippy_lint! {
     /// ### What it does
     /// Checks for explicit `Clone` implementations for `Copy`
     /// types.
     ///
     /// ### Why is this bad?
     /// To avoid surprising behavior, these traits should
     /// agree and the behavior of `Copy` cannot be overridden. In almost all
     /// situations a `Copy` type should have a `Clone` implementation that does
     /// nothing more than copy the object, which is what `#[derive(Copy, Clone)]`
     /// gets you.
     ///
     /// ### Example
     /// ```rust,ignore
     /// #[derive(Copy)]
     /// struct Foo;
     ///
     /// impl Clone for Foo {
     ///     // ..
     /// }
     /// ```
     #[clippy::version = "pre 1.29.0"]
     pub EXPL_IMPL_CLONE_ON_COPY,
     pedantic,
     "implementing `Clone` explicitly on `Copy` types"
 }

 declare_clippy_lint! {
     /// ### What it does
     /// Checks for deriving `serde::Deserialize` on a type that
     /// has methods using `unsafe`.
     ///
     /// ### Why is this bad?
     /// Deriving `serde::Deserialize` will create a constructor
     /// that may violate invariants held by another constructor.
     ///
     /// ### Example
     /// ```rust,ignore
     /// use serde::Deserialize;
     ///
     /// #[derive(Deserialize)]
     /// pub struct Foo {
     ///     // ..
     /// }
     ///
     /// impl Foo {
     ///     pub fn new() -> Self {
     ///         // setup here ..
     ///     }
     ///
     ///     pub unsafe fn parts() -> (&str, &str) {
     ///         // assumes invariants hold
     ///     }
     /// }
     /// ```
     #[clippy::version = "1.45.0"]
     pub UNSAFE_DERIVE_DESERIALIZE,
     pedantic,
     "deriving `serde::Deserialize` on a type that has methods using `unsafe`"
 }

 declare_clippy_lint! {
     /// ### What it does
     /// Checks for types that derive `PartialEq` and could implement `Eq`.
     ///
     /// ### Why is this bad?
     /// If a type `T` derives `PartialEq` and all of its members implement `Eq`,
     /// then `T` can always implement `Eq`. Implementing `Eq` allows `T` to be used
     /// in APIs that require `Eq` types. It also allows structs containing `T` to derive
     /// `Eq` themselves.
     ///
     /// ### Example
     /// ```no_run
     /// #[derive(PartialEq)]
     /// struct Foo {
     ///     i_am_eq: i32,
     ///     i_am_eq_too: Vec<String>,
     /// }
     /// ```
     /// Use instead:
     /// ```no_run
     /// #[derive(PartialEq, Eq)]
     /// struct Foo {
     ///     i_am_eq: i32,
     ///     i_am_eq_too: Vec<String>,
     /// }
     /// ```
     #[clippy::version = "1.63.0"]
     pub DERIVE_PARTIAL_EQ_WITHOUT_EQ,
     nursery,
     "deriving `PartialEq` on a type that can implement `Eq`, without implementing `Eq`"
 }

 declare_lint_pass!(Derive => [
     EXPL_IMPL_CLONE_ON_COPY,
     DERIVED_HASH_WITH_MANUAL_EQ,
     DERIVE_ORD_XOR_PARTIAL_ORD,
     UNSAFE_DERIVE_DESERIALIZE,
     DERIVE_PARTIAL_EQ_WITHOUT_EQ
 ]);

 impl<'tcx> LateLintPass<'tcx> for Derive {
     fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx Item<'_>) {
         if let ItemKind::Impl(Impl {
             of_trait: Some(ref trait_ref),
             ..
         }) = item.kind
         {
             let ty = cx.tcx.type_of(item.owner_id).instantiate_identity();
             let is_automatically_derived = cx.tcx.has_attr(item.owner_id, sym::automatically_derived);

             check_hash_peq(cx, item.span, trait_ref, ty, is_automatically_derived);
             check_ord_partial_ord(cx, item.span, trait_ref, ty, is_automatically_derived);

             if is_automatically_derived {
                 check_unsafe_derive_deserialize(cx, item, trait_ref, ty);
                 check_partial_eq_without_eq(cx, item.span, trait_ref, ty);
             } else {
                 check_copy_clone(cx, item, trait_ref, ty);
             }
         }
     }
 }

 /// Implementation of the `DERIVED_HASH_WITH_MANUAL_EQ` lint.
 fn check_hash_peq<'tcx>(
     cx: &LateContext<'tcx>,
     span: Span,
     trait_ref: &hir::TraitRef<'_>,
     ty: Ty<'tcx>,
     hash_is_automatically_derived: bool,
 ) {
     if let Some(peq_trait_def_id) = cx.tcx.lang_items().eq_trait()
         && let Some(def_id) = trait_ref.trait_def_id()
         && cx.tcx.is_diagnostic_item(sym::Hash, def_id)
     {
         // Look for the PartialEq implementations for `ty`
         cx.tcx.for_each_relevant_impl(peq_trait_def_id, ty, |impl_id| {
             let peq_is_automatically_derived = cx.tcx.has_attr(impl_id, sym::automatically_derived);

             if !hash_is_automatically_derived || peq_is_automatically_derived {
                 return;
             }

             let trait_ref = cx.tcx.impl_trait_ref(impl_id).expect("must be a trait implementation");

             // Only care about `impl PartialEq<Foo> for Foo`
             // For `impl PartialEq<B> for A, input_types is [A, B]
             if trait_ref.instantiate_identity().args.type_at(1) == ty {
                 span_lint_and_then(
                     cx,
                     DERIVED_HASH_WITH_MANUAL_EQ,
                     span,
                     "you are deriving `Hash` but have implemented `PartialEq` explicitly",
                     |diag| {
                         if let Some(local_def_id) = impl_id.as_local() {
                             let hir_id = cx.tcx.local_def_id_to_hir_id(local_def_id);
                             diag.span_note(cx.tcx.hir().span(hir_id), "`PartialEq` implemented here");
                         }
                     },
                 );
             }
         });
     }
 }

 /// Implementation of the `DERIVE_ORD_XOR_PARTIAL_ORD` lint.
 fn check_ord_partial_ord<'tcx>(
     cx: &LateContext<'tcx>,
     span: Span,
     trait_ref: &hir::TraitRef<'_>,
     ty: Ty<'tcx>,
     ord_is_automatically_derived: bool,
 ) {
     if let Some(ord_trait_def_id) = cx.tcx.get_diagnostic_item(sym::Ord)
         && let Some(partial_ord_trait_def_id) = cx.tcx.lang_items().partial_ord_trait()
         && let Some(def_id) = &trait_ref.trait_def_id()
         && *def_id == ord_trait_def_id
     {
         // Look for the PartialOrd implementations for `ty`
         cx.tcx.for_each_relevant_impl(partial_ord_trait_def_id, ty, |impl_id| {
             let partial_ord_is_automatically_derived = cx.tcx.has_attr(impl_id, sym::automatically_derived);

             if partial_ord_is_automatically_derived == ord_is_automatically_derived {
                 return;
             }

             let trait_ref = cx.tcx.impl_trait_ref(impl_id).expect("must be a trait implementation");

             // Only care about `impl PartialOrd<Foo> for Foo`
             // For `impl PartialOrd<B> for A, input_types is [A, B]
             if trait_ref.instantiate_identity().args.type_at(1) == ty {
                 let mess = if partial_ord_is_automatically_derived {
                     "you are implementing `Ord` explicitly but have derived `PartialOrd`"
                 } else {
                     "you are deriving `Ord` but have implemented `PartialOrd` explicitly"
                 };

                 span_lint_and_then(cx, DERIVE_ORD_XOR_PARTIAL_ORD, span, mess, |diag| {
                     if let Some(local_def_id) = impl_id.as_local() {
                         let hir_id = cx.tcx.local_def_id_to_hir_id(local_def_id);
                         diag.span_note(cx.tcx.hir().span(hir_id), "`PartialOrd` implemented here");
                     }
                 });
             }
         });
     }
 }

 /// Implementation of the `EXPL_IMPL_CLONE_ON_COPY` lint.
 fn check_copy_clone<'tcx>(cx: &LateContext<'tcx>, item: &Item<'_>, trait_ref: &hir::TraitRef<'_>, ty: Ty<'tcx>) {
     let clone_id = match cx.tcx.lang_items().clone_trait() {
         Some(id) if trait_ref.trait_def_id() == Some(id) => id,
         _ => return,
     };
     let Some(copy_id) = cx.tcx.lang_items().copy_trait() else {
         return;
     };
     let (ty_adt, ty_subs) = match *ty.kind() {
         // Unions can't derive clone.
         ty::Adt(adt, subs) if !adt.is_union() => (adt, subs),
         _ => return,
     };
     // If the current self type doesn't implement Copy (due to generic constraints), search to see if
     // there's a Copy impl for any instance of the adt.
     if !is_copy(cx, ty) {
         if ty_subs.non_erasable_generics(cx.tcx, ty_adt.did()).next().is_some() {
             let has_copy_impl = cx.tcx.all_local_trait_impls(()).get(&copy_id).map_or(false, |impls| {
                 impls.iter().any(|&id| {
                     matches!(cx.tcx.type_of(id).instantiate_identity().kind(), ty::Adt(adt, _)
                                         if ty_adt.did() == adt.did())
                 })
             });
             if !has_copy_impl {
                 return;
             }
         } else {
             return;
         }
     }
     // Derive constrains all generic types to requiring Clone. Check if any type is not constrained for
     // this impl.
     if ty_subs.types().any(|ty| !implements_trait(cx, ty, clone_id, &[])) {
         return;
     }
     // `#[repr(packed)]` structs with type/const parameters can't derive `Clone`.
     // https://github.com/rust-lang/rust-clippy/issues/10188
     if ty_adt.repr().packed()
         && ty_subs
             .iter()
             .any(|arg| matches!(arg.unpack(), GenericArgKind::Type(_) | GenericArgKind::Const(_)))
     {
         return;
     }

     span_lint_and_note(
         cx,
         EXPL_IMPL_CLONE_ON_COPY,
         item.span,
         "you are implementing `Clone` explicitly on a `Copy` type",
         Some(item.span),
         "consider deriving `Clone` or removing `Copy`",
     );
 }

 /// Implementation of the `UNSAFE_DERIVE_DESERIALIZE` lint.
 fn check_unsafe_derive_deserialize<'tcx>(
     cx: &LateContext<'tcx>,
     item: &Item<'_>,
     trait_ref: &hir::TraitRef<'_>,
     ty: Ty<'tcx>,
 ) {
     fn has_unsafe<'tcx>(cx: &LateContext<'tcx>, item: &'tcx Item<'_>) -> bool {
         let mut visitor = UnsafeVisitor { cx, has_unsafe: false };
         walk_item(&mut visitor, item);
         visitor.has_unsafe
     }

     if let Some(trait_def_id) = trait_ref.trait_def_id()
         && match_def_path(cx, trait_def_id, &paths::SERDE_DESERIALIZE)
         && let ty::Adt(def, _) = ty.kind()
         && let Some(local_def_id) = def.did().as_local()
         && let adt_hir_id = cx.tcx.local_def_id_to_hir_id(local_def_id)
         && !is_lint_allowed(cx, UNSAFE_DERIVE_DESERIALIZE, adt_hir_id)
         && cx
             .tcx
             .inherent_impls(def.did())
             .into_iter()
             .flatten()
             .map(|imp_did| cx.tcx.hir().expect_item(imp_did.expect_local()))
             .any(|imp| has_unsafe(cx, imp))
     {
         span_lint_and_help(
             cx,
             UNSAFE_DERIVE_DESERIALIZE,
             item.span,
             "you are deriving `serde::Deserialize` on a type that has methods using `unsafe`",
             None,
             "consider implementing `serde::Deserialize` manually. See https://serde.rs/impl-deserialize.html",
         );
     }
 }

 struct UnsafeVisitor<'a, 'tcx> {
     cx: &'a LateContext<'tcx>,
     has_unsafe: bool,
 }

 impl<'tcx> Visitor<'tcx> for UnsafeVisitor<'_, 'tcx> {
     type NestedFilter = nested_filter::All;

     fn visit_fn(&mut self, kind: FnKind<'tcx>, decl: &'tcx FnDecl<'_>, body_id: BodyId, _: Span, id: LocalDefId) {
         if self.has_unsafe {
             return;
         }

         if let Some(header) = kind.header()
             && header.unsafety == Unsafety::Unsafe
         {
             self.has_unsafe = true;
         }

         walk_fn(self, kind, decl, body_id, id);
     }

     fn visit_expr(&mut self, expr: &'tcx Expr<'_>) {
         if self.has_unsafe {
             return;
         }

         if let ExprKind::Block(block, _) = expr.kind {
             if block.rules == BlockCheckMode::UnsafeBlock(UnsafeSource::UserProvided) {
                 self.has_unsafe = true;
             }
         }

         walk_expr(self, expr);
     }

     fn nested_visit_map(&mut self) -> Self::Map {
         self.cx.tcx.hir()
     }
 }

 /// Implementation of the `DERIVE_PARTIAL_EQ_WITHOUT_EQ` lint.
 fn check_partial_eq_without_eq<'tcx>(cx: &LateContext<'tcx>, span: Span, trait_ref: &hir::TraitRef<'_>, ty: Ty<'tcx>) {
     if let ty::Adt(adt, args) = ty.kind()
         && cx.tcx.visibility(adt.did()).is_public()
         && let Some(eq_trait_def_id) = cx.tcx.get_diagnostic_item(sym::Eq)
         && let Some(def_id) = trait_ref.trait_def_id()
         && cx.tcx.is_diagnostic_item(sym::PartialEq, def_id)
         && !has_non_exhaustive_attr(cx.tcx, *adt)
         && !ty_implements_eq_trait(cx.tcx, ty, eq_trait_def_id)
         && let param_env = param_env_for_derived_eq(cx.tcx, adt.did(), eq_trait_def_id)
         // If all of our fields implement `Eq`, we can implement `Eq` too
         && adt
             .all_fields()
             .map(|f| f.ty(cx.tcx, args))
             .all(|ty| implements_trait_with_env(cx.tcx, param_env, ty, eq_trait_def_id, None, &[]))
     {
         span_lint_and_sugg(
             cx,
             DERIVE_PARTIAL_EQ_WITHOUT_EQ,
             span.ctxt().outer_expn_data().call_site,
             "you are deriving `PartialEq` and can implement `Eq`",
             "consider deriving `Eq` as well",
             "PartialEq, Eq".to_string(),
             Applicability::MachineApplicable,
         );
     }
 }

 fn ty_implements_eq_trait<'tcx>(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>, eq_trait_id: DefId) -> bool {
     tcx.non_blanket_impls_for_ty(eq_trait_id, ty).next().is_some()
 }

 /// Creates the `ParamEnv` used for the give type's derived `Eq` impl.
 fn param_env_for_derived_eq(tcx: TyCtxt<'_>, did: DefId, eq_trait_id: DefId) -> ParamEnv<'_> {
     // Initial map from generic index to param def.
     // Vec<(param_def, needs_eq)>
     let mut params = tcx
         .generics_of(did)
         .own_params
         .iter()
         .map(|p| (p, matches!(p.kind, GenericParamDefKind::Type { .. })))
         .collect::<Vec<_>>();

     let ty_predicates = tcx.predicates_of(did).predicates;
     for (p, _) in ty_predicates {
         if let ClauseKind::Trait(p) = p.kind().skip_binder()
             && p.trait_ref.def_id == eq_trait_id
             && let ty::Param(self_ty) = p.trait_ref.self_ty().kind()
         {
             // Flag types which already have an `Eq` bound.
             params[self_ty.index as usize].1 = false;
         }
     }

     ParamEnv::new(
         tcx.mk_clauses_from_iter(ty_predicates.iter().map(|&(p, _)| p).chain(
             params.iter().filter(|&&(_, needs_eq)| needs_eq).map(|&(param, _)| {
                 ClauseKind::Trait(TraitPredicate {
                     trait_ref: ty::TraitRef::new(tcx, eq_trait_id, [tcx.mk_param_from_def(param)]),
                     polarity: ty::PredicatePolarity::Positive,
                 })
                 .to_predicate(tcx)
             }),
         )),
         Reveal::UserFacing,
     )
 }
	use clippy_utils::diagnostics::{span_lint_and_help, span_lint_and_note, span_lint_and_sugg, span_lint_and_then};
	use clippy_utils::ty::{implements_trait, implements_trait_with_env, is_copy};
	use clippy_utils::{has_non_exhaustive_attr, is_lint_allowed, match_def_path, paths};
	use rustc_errors::Applicability;
	use rustc_hir::def_id::DefId;
	use rustc_hir::intravisit::{walk_expr, walk_fn, walk_item, FnKind, Visitor};
	use rustc_hir::{
	self as hir, BlockCheckMode, BodyId, Expr, ExprKind, FnDecl, Impl, Item, ItemKind, UnsafeSource, Unsafety,
	};
	use rustc_lint::{LateContext, LateLintPass};
	use rustc_middle::hir::nested_filter;
	use rustc_middle::traits::Reveal;
	use rustc_middle::ty::{
	self, ClauseKind, GenericArgKind, GenericParamDefKind, ParamEnv, ToPredicate, TraitPredicate, Ty, TyCtxt,
	};
	use rustc_session::declare_lint_pass;
	use rustc_span::def_id::LocalDefId;
	use rustc_span::{sym, Span};

	declare_clippy_lint! {
	/// ### What it does
	/// Lints against manual `PartialEq` implementations for types with a derived `Hash`
	/// implementation.
	///
	/// ### Why is this bad?
	/// The implementation of these traits must agree (for
	/// example for use with `HashMap`) so it’s probably a bad idea to use a
	/// default-generated `Hash` implementation with an explicitly defined
	/// `PartialEq`. In particular, the following must hold for any type:
	///
	/// ```text
	/// k1 == k2 ⇒ hash(k1) == hash(k2)
	/// ```
	///
	/// ### Example
	/// ```ignore
	/// #[derive(Hash)]
	/// struct Foo;
	///
	/// impl PartialEq for Foo {
	/// ...
	/// }
	/// ```
	#[clippy::version = "pre 1.29.0"]
	pub DERIVED_HASH_WITH_MANUAL_EQ,
	correctness,
	"deriving `Hash` but implementing `PartialEq` explicitly"
	}

	declare_clippy_lint! {
	/// ### What it does
	/// Lints against manual `PartialOrd` and `Ord` implementations for types with a derived `Ord`
	/// or `PartialOrd` implementation.
	///
	/// ### Why is this bad?
	/// The implementation of these traits must agree (for
	/// example for use with `sort`) so it’s probably a bad idea to use a
	/// default-generated `Ord` implementation with an explicitly defined
	/// `PartialOrd`. In particular, the following must hold for any type
	/// implementing `Ord`:
	///
	/// ```text
	/// k1.cmp(&k2) == k1.partial_cmp(&k2).unwrap()
	/// ```
	///
	/// ### Example
	/// ```rust,ignore
	/// #[derive(Ord, PartialEq, Eq)]
	/// struct Foo;
	///
	/// impl PartialOrd for Foo {
	/// ...
	/// }
	/// ```
	/// Use instead:
	/// ```rust,ignore
	/// #[derive(PartialEq, Eq)]
	/// struct Foo;
	///
	/// impl PartialOrd for Foo {
	/// fn partial_cmp(&self, other: &Foo) -> Option<Ordering> {
	/// Some(self.cmp(other))
	/// }
	/// }
	///
	/// impl Ord for Foo {
	/// ...
	/// }
	/// ```
	/// or, if you don't need a custom ordering:
	/// ```rust,ignore
	/// #[derive(Ord, PartialOrd, PartialEq, Eq)]
	/// struct Foo;
	/// ```
	#[clippy::version = "1.47.0"]
	pub DERIVE_ORD_XOR_PARTIAL_ORD,
	correctness,
	"deriving `Ord` but implementing `PartialOrd` explicitly"
	}

	declare_clippy_lint! {
	/// ### What it does
	/// Checks for explicit `Clone` implementations for `Copy`
	/// types.
	///
	/// ### Why is this bad?
	/// To avoid surprising behavior, these traits should
	/// agree and the behavior of `Copy` cannot be overridden. In almost all
	/// situations a `Copy` type should have a `Clone` implementation that does
	/// nothing more than copy the object, which is what `#[derive(Copy, Clone)]`
	/// gets you.
	///
	/// ### Example
	/// ```rust,ignore
	/// #[derive(Copy)]
	/// struct Foo;
	///
	/// impl Clone for Foo {
	/// // ..
	/// }
	/// ```
	#[clippy::version = "pre 1.29.0"]
	pub EXPL_IMPL_CLONE_ON_COPY,
	pedantic,
	"implementing `Clone` explicitly on `Copy` types"
	}

	declare_clippy_lint! {
	/// ### What it does
	/// Checks for deriving `serde::Deserialize` on a type that
	/// has methods using `unsafe`.
	///
	/// ### Why is this bad?
	/// Deriving `serde::Deserialize` will create a constructor
	/// that may violate invariants held by another constructor.
	///
	/// ### Example
	/// ```rust,ignore
	/// use serde::Deserialize;
	///
	/// #[derive(Deserialize)]
	/// pub struct Foo {
	/// // ..
	/// }
	///
	/// impl Foo {
	/// pub fn new() -> Self {
	/// // setup here ..
	/// }
	///
	/// pub unsafe fn parts() -> (&str, &str) {
	/// // assumes invariants hold
	/// }
	/// }
	/// ```
	#[clippy::version = "1.45.0"]
	pub UNSAFE_DERIVE_DESERIALIZE,
	pedantic,
	"deriving `serde::Deserialize` on a type that has methods using `unsafe`"
	}

	declare_clippy_lint! {
	/// ### What it does
	/// Checks for types that derive `PartialEq` and could implement `Eq`.
	///
	/// ### Why is this bad?
	/// If a type `T` derives `PartialEq` and all of its members implement `Eq`,
	/// then `T` can always implement `Eq`. Implementing `Eq` allows `T` to be used
	/// in APIs that require `Eq` types. It also allows structs containing `T` to derive
	/// `Eq` themselves.
	///
	/// ### Example
	/// ```no_run
	/// #[derive(PartialEq)]
	/// struct Foo {
	/// i_am_eq: i32,
	/// i_am_eq_too: Vec<String>,
	/// }
	/// ```
	/// Use instead:
	/// ```no_run
	/// #[derive(PartialEq, Eq)]
	/// struct Foo {
	/// i_am_eq: i32,
	/// i_am_eq_too: Vec<String>,
	/// }
	/// ```
	#[clippy::version = "1.63.0"]
	pub DERIVE_PARTIAL_EQ_WITHOUT_EQ,
	nursery,
	"deriving `PartialEq` on a type that can implement `Eq`, without implementing `Eq`"
	}

	declare_lint_pass!(Derive => [
	EXPL_IMPL_CLONE_ON_COPY,
	DERIVED_HASH_WITH_MANUAL_EQ,
	DERIVE_ORD_XOR_PARTIAL_ORD,
	UNSAFE_DERIVE_DESERIALIZE,
	DERIVE_PARTIAL_EQ_WITHOUT_EQ
	]);

	impl<'tcx> LateLintPass<'tcx> for Derive {
	fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx Item<'_>) {
	if let ItemKind::Impl(Impl {
	of_trait: Some(ref trait_ref),
	..
	}) = item.kind
	{
	let ty = cx.tcx.type_of(item.owner_id).instantiate_identity();
	let is_automatically_derived = cx.tcx.has_attr(item.owner_id, sym::automatically_derived);

	check_hash_peq(cx, item.span, trait_ref, ty, is_automatically_derived);
	check_ord_partial_ord(cx, item.span, trait_ref, ty, is_automatically_derived);

	if is_automatically_derived {
	check_unsafe_derive_deserialize(cx, item, trait_ref, ty);
	check_partial_eq_without_eq(cx, item.span, trait_ref, ty);
	} else {
	check_copy_clone(cx, item, trait_ref, ty);
	}
	}
	}
	}

	/// Implementation of the `DERIVED_HASH_WITH_MANUAL_EQ` lint.
	fn check_hash_peq<'tcx>(
	cx: &LateContext<'tcx>,
	span: Span,
	trait_ref: &hir::TraitRef<'_>,
	ty: Ty<'tcx>,
	hash_is_automatically_derived: bool,
	) {
	if let Some(peq_trait_def_id) = cx.tcx.lang_items().eq_trait()
	&& let Some(def_id) = trait_ref.trait_def_id()
	&& cx.tcx.is_diagnostic_item(sym::Hash, def_id)
	{
	// Look for the PartialEq implementations for `ty`
	cx.tcx.for_each_relevant_impl(peq_trait_def_id, ty, \|impl_id\| {
	let peq_is_automatically_derived = cx.tcx.has_attr(impl_id, sym::automatically_derived);

	if !hash_is_automatically_derived \|\| peq_is_automatically_derived {
	return;
	}

	let trait_ref = cx.tcx.impl_trait_ref(impl_id).expect("must be a trait implementation");

	// Only care about `impl PartialEq<Foo> for Foo`
	// For `impl PartialEq<B> for A, input_types is [A, B]
	if trait_ref.instantiate_identity().args.type_at(1) == ty {
	span_lint_and_then(
	cx,
	DERIVED_HASH_WITH_MANUAL_EQ,
	span,
	"you are deriving `Hash` but have implemented `PartialEq` explicitly",
	\|diag\| {
	if let Some(local_def_id) = impl_id.as_local() {
	let hir_id = cx.tcx.local_def_id_to_hir_id(local_def_id);
	diag.span_note(cx.tcx.hir().span(hir_id), "`PartialEq` implemented here");
	}
	},
	);
	}
	});
	}
	}

	/// Implementation of the `DERIVE_ORD_XOR_PARTIAL_ORD` lint.
	fn check_ord_partial_ord<'tcx>(
	cx: &LateContext<'tcx>,
	span: Span,
	trait_ref: &hir::TraitRef<'_>,
	ty: Ty<'tcx>,
	ord_is_automatically_derived: bool,
	) {
	if let Some(ord_trait_def_id) = cx.tcx.get_diagnostic_item(sym::Ord)
	&& let Some(partial_ord_trait_def_id) = cx.tcx.lang_items().partial_ord_trait()
	&& let Some(def_id) = &trait_ref.trait_def_id()
	&& *def_id == ord_trait_def_id
	{
	// Look for the PartialOrd implementations for `ty`
	cx.tcx.for_each_relevant_impl(partial_ord_trait_def_id, ty, \|impl_id\| {
	let partial_ord_is_automatically_derived = cx.tcx.has_attr(impl_id, sym::automatically_derived);

	if partial_ord_is_automatically_derived == ord_is_automatically_derived {
	return;
	}

	let trait_ref = cx.tcx.impl_trait_ref(impl_id).expect("must be a trait implementation");

	// Only care about `impl PartialOrd<Foo> for Foo`
	// For `impl PartialOrd<B> for A, input_types is [A, B]
	if trait_ref.instantiate_identity().args.type_at(1) == ty {
	let mess = if partial_ord_is_automatically_derived {
	"you are implementing `Ord` explicitly but have derived `PartialOrd`"
	} else {
	"you are deriving `Ord` but have implemented `PartialOrd` explicitly"
	};

	span_lint_and_then(cx, DERIVE_ORD_XOR_PARTIAL_ORD, span, mess, \|diag\| {
	if let Some(local_def_id) = impl_id.as_local() {
	let hir_id = cx.tcx.local_def_id_to_hir_id(local_def_id);
	diag.span_note(cx.tcx.hir().span(hir_id), "`PartialOrd` implemented here");
	}
	});
	}
	});
	}
	}

	/// Implementation of the `EXPL_IMPL_CLONE_ON_COPY` lint.
	fn check_copy_clone<'tcx>(cx: &LateContext<'tcx>, item: &Item<'_>, trait_ref: &hir::TraitRef<'_>, ty: Ty<'tcx>) {
	let clone_id = match cx.tcx.lang_items().clone_trait() {
	Some(id) if trait_ref.trait_def_id() == Some(id) => id,
	_ => return,
	};
	let Some(copy_id) = cx.tcx.lang_items().copy_trait() else {
	return;
	};
	let (ty_adt, ty_subs) = match *ty.kind() {
	// Unions can't derive clone.
	ty::Adt(adt, subs) if !adt.is_union() => (adt, subs),
	_ => return,
	};
	// If the current self type doesn't implement Copy (due to generic constraints), search to see if
	// there's a Copy impl for any instance of the adt.
	if !is_copy(cx, ty) {
	if ty_subs.non_erasable_generics(cx.tcx, ty_adt.did()).next().is_some() {
	let has_copy_impl = cx.tcx.all_local_trait_impls(()).get(&copy_id).map_or(false, \|impls\| {
	impls.iter().any(\|&id\| {
	matches!(cx.tcx.type_of(id).instantiate_identity().kind(), ty::Adt(adt, _)
	if ty_adt.did() == adt.did())
	})
	});
	if !has_copy_impl {
	return;
	}
	} else {
	return;
	}
	}
	// Derive constrains all generic types to requiring Clone. Check if any type is not constrained for
	// this impl.
	if ty_subs.types().any(\|ty\| !implements_trait(cx, ty, clone_id, &[])) {
	return;
	}
	// `#[repr(packed)]` structs with type/const parameters can't derive `Clone`.
	// https://github.com/rust-lang/rust-clippy/issues/10188
	if ty_adt.repr().packed()
	&& ty_subs
	.iter()
	.any(\|arg\| matches!(arg.unpack(), GenericArgKind::Type(_) \| GenericArgKind::Const(_)))
	{
	return;
	}

	span_lint_and_note(
	cx,
	EXPL_IMPL_CLONE_ON_COPY,
	item.span,
	"you are implementing `Clone` explicitly on a `Copy` type",
	Some(item.span),
	"consider deriving `Clone` or removing `Copy`",
	);
	}

	/// Implementation of the `UNSAFE_DERIVE_DESERIALIZE` lint.
	fn check_unsafe_derive_deserialize<'tcx>(
	cx: &LateContext<'tcx>,
	item: &Item<'_>,
	trait_ref: &hir::TraitRef<'_>,
	ty: Ty<'tcx>,
	) {
	fn has_unsafe<'tcx>(cx: &LateContext<'tcx>, item: &'tcx Item<'_>) -> bool {
	let mut visitor = UnsafeVisitor { cx, has_unsafe: false };
	walk_item(&mut visitor, item);
	visitor.has_unsafe
	}

	if let Some(trait_def_id) = trait_ref.trait_def_id()
	&& match_def_path(cx, trait_def_id, &paths::SERDE_DESERIALIZE)
	&& let ty::Adt(def, _) = ty.kind()
	&& let Some(local_def_id) = def.did().as_local()
	&& let adt_hir_id = cx.tcx.local_def_id_to_hir_id(local_def_id)
	&& !is_lint_allowed(cx, UNSAFE_DERIVE_DESERIALIZE, adt_hir_id)
	&& cx
	.tcx
	.inherent_impls(def.did())
	.into_iter()
	.flatten()
	.map(\|imp_did\| cx.tcx.hir().expect_item(imp_did.expect_local()))
	.any(\|imp\| has_unsafe(cx, imp))
	{
	span_lint_and_help(
	cx,
	UNSAFE_DERIVE_DESERIALIZE,
	item.span,
	"you are deriving `serde::Deserialize` on a type that has methods using `unsafe`",
	None,
	"consider implementing `serde::Deserialize` manually. See https://serde.rs/impl-deserialize.html",
	);
	}
	}

	struct UnsafeVisitor<'a, 'tcx> {
	cx: &'a LateContext<'tcx>,
	has_unsafe: bool,
	}

	impl<'tcx> Visitor<'tcx> for UnsafeVisitor<'_, 'tcx> {
	type NestedFilter = nested_filter::All;

	fn visit_fn(&mut self, kind: FnKind<'tcx>, decl: &'tcx FnDecl<'_>, body_id: BodyId, _: Span, id: LocalDefId) {
	if self.has_unsafe {
	return;
	}

	if let Some(header) = kind.header()
	&& header.unsafety == Unsafety::Unsafe
	{
	self.has_unsafe = true;
	}

	walk_fn(self, kind, decl, body_id, id);
	}

	fn visit_expr(&mut self, expr: &'tcx Expr<'_>) {
	if self.has_unsafe {
	return;
	}

	if let ExprKind::Block(block, _) = expr.kind {
	if block.rules == BlockCheckMode::UnsafeBlock(UnsafeSource::UserProvided) {
	self.has_unsafe = true;
	}
	}

	walk_expr(self, expr);
	}

	fn nested_visit_map(&mut self) -> Self::Map {
	self.cx.tcx.hir()
	}
	}

	/// Implementation of the `DERIVE_PARTIAL_EQ_WITHOUT_EQ` lint.
	fn check_partial_eq_without_eq<'tcx>(cx: &LateContext<'tcx>, span: Span, trait_ref: &hir::TraitRef<'_>, ty: Ty<'tcx>) {
	if let ty::Adt(adt, args) = ty.kind()
	&& cx.tcx.visibility(adt.did()).is_public()
	&& let Some(eq_trait_def_id) = cx.tcx.get_diagnostic_item(sym::Eq)
	&& let Some(def_id) = trait_ref.trait_def_id()
	&& cx.tcx.is_diagnostic_item(sym::PartialEq, def_id)
	&& !has_non_exhaustive_attr(cx.tcx, *adt)
	&& !ty_implements_eq_trait(cx.tcx, ty, eq_trait_def_id)
	&& let param_env = param_env_for_derived_eq(cx.tcx, adt.did(), eq_trait_def_id)
	// If all of our fields implement `Eq`, we can implement `Eq` too
	&& adt
	.all_fields()
	.map(\|f\| f.ty(cx.tcx, args))
	.all(\|ty\| implements_trait_with_env(cx.tcx, param_env, ty, eq_trait_def_id, None, &[]))
	{
	span_lint_and_sugg(
	cx,
	DERIVE_PARTIAL_EQ_WITHOUT_EQ,
	span.ctxt().outer_expn_data().call_site,
	"you are deriving `PartialEq` and can implement `Eq`",
	"consider deriving `Eq` as well",
	"PartialEq, Eq".to_string(),
	Applicability::MachineApplicable,
	);
	}
	}

	fn ty_implements_eq_trait<'tcx>(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>, eq_trait_id: DefId) -> bool {
	tcx.non_blanket_impls_for_ty(eq_trait_id, ty).next().is_some()
	}

	/// Creates the `ParamEnv` used for the give type's derived `Eq` impl.
	fn param_env_for_derived_eq(tcx: TyCtxt<'_>, did: DefId, eq_trait_id: DefId) -> ParamEnv<'_> {
	// Initial map from generic index to param def.
	// Vec<(param_def, needs_eq)>
	let mut params = tcx
	.generics_of(did)
	.own_params
	.iter()
	.map(\|p\| (p, matches!(p.kind, GenericParamDefKind::Type { .. })))
	.collect::<Vec<_>>();

	let ty_predicates = tcx.predicates_of(did).predicates;
	for (p, _) in ty_predicates {
	if let ClauseKind::Trait(p) = p.kind().skip_binder()
	&& p.trait_ref.def_id == eq_trait_id
	&& let ty::Param(self_ty) = p.trait_ref.self_ty().kind()
	{
	// Flag types which already have an `Eq` bound.
	params[self_ty.index as usize].1 = false;
	}
	}

	ParamEnv::new(
	tcx.mk_clauses_from_iter(ty_predicates.iter().map(\|&(p, _)\| p).chain(
	params.iter().filter(\|&&(_, needs_eq)\| needs_eq).map(\|&(param, _)\| {
	ClauseKind::Trait(TraitPredicate {
	trait_ref: ty::TraitRef::new(tcx, eq_trait_id, [tcx.mk_param_from_def(param)]),
	polarity: ty::PredicatePolarity::Positive,
	})
	.to_predicate(tcx)
	}),
	)),
	Reveal::UserFacing,
	)
	}