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

 use crate::utils::paths;
 use crate::utils::{
     get_trait_def_id, is_allowed, is_automatically_derived, is_copy, match_path, span_lint_and_help,
     span_lint_and_note, span_lint_and_then,
 };
 use if_chain::if_chain;
 use rustc_hir::def_id::DefId;
 use rustc_hir::intravisit::{walk_expr, walk_fn, walk_item, FnKind, NestedVisitorMap, Visitor};
 use rustc_hir::{
     BlockCheckMode, BodyId, Expr, ExprKind, FnDecl, HirId, Item, ItemKind, TraitRef, UnsafeSource, Unsafety,
 };
 use rustc_lint::{LateContext, LateLintPass};
 use rustc_middle::hir::map::Map;
 use rustc_middle::ty::{self, Ty};
 use rustc_session::{declare_lint_pass, declare_tool_lint};
 use rustc_span::source_map::Span;

 declare_clippy_lint! {
     /// **What it does:** Checks for deriving `Hash` but implementing `PartialEq`
     /// explicitly or vice versa.
     ///
     /// **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)
     /// ```
     ///
     /// **Known problems:** None.
     ///
     /// **Example:**
     /// ```ignore
     /// #[derive(Hash)]
     /// struct Foo;
     ///
     /// impl PartialEq for Foo {
     ///     ...
     /// }
     /// ```
     pub DERIVE_HASH_XOR_EQ,
     correctness,
     "deriving `Hash` but implementing `PartialEq` explicitly"
 }

 declare_clippy_lint! {
     /// **What it does:** Checks for deriving `Ord` but implementing `PartialOrd`
     /// explicitly or vice versa.
     ///
     /// **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()
     /// ```
     ///
     /// **Known problems:** None.
     ///
     /// **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;
     /// ```
     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 behaviour, these traits should
     /// agree and the behaviour 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.
     ///
     /// **Known problems:** Bounds of generic types are sometimes wrong: https://github.com/rust-lang/rust/issues/26925
     ///
     /// **Example:**
     /// ```rust,ignore
     /// #[derive(Copy)]
     /// struct Foo;
     ///
     /// impl Clone for Foo {
     ///     // ..
     /// }
     /// ```
     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 hold by another constructor.
     ///
     /// **Known problems:** None.
     ///
     /// **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
     ///     }
     /// }
     /// ```
     pub UNSAFE_DERIVE_DESERIALIZE,
     pedantic,
     "deriving `serde::Deserialize` on a type that has methods using `unsafe`"
 }

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

 impl<'tcx> LateLintPass<'tcx> for Derive {
     fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx Item<'_>) {
         if let ItemKind::Impl {
             of_trait: Some(ref trait_ref),
             ..
         } = item.kind
         {
             let ty = cx.tcx.type_of(cx.tcx.hir().local_def_id(item.hir_id));
             let is_automatically_derived = is_automatically_derived(&*item.attrs);

             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);
             } else {
                 check_copy_clone(cx, item, trait_ref, ty);
             }
         }
     }
 }

 /// Implementation of the `DERIVE_HASH_XOR_EQ` lint.
 fn check_hash_peq<'tcx>(
     cx: &LateContext<'tcx>,
     span: Span,
     trait_ref: &TraitRef<'_>,
     ty: Ty<'tcx>,
     hash_is_automatically_derived: bool,
 ) {
     if_chain! {
         if match_path(&trait_ref.path, &paths::HASH);
         if let Some(peq_trait_def_id) = cx.tcx.lang_items().eq_trait();
         if let Some(def_id) = &trait_ref.trait_def_id();
         if !def_id.is_local();
         then {
             // 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 = is_automatically_derived(&cx.tcx.get_attrs(impl_id));

                 if peq_is_automatically_derived == hash_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.substs.type_at(1) == ty {
                     let mess = if peq_is_automatically_derived {
                         "you are implementing `Hash` explicitly but have derived `PartialEq`"
                     } else {
                         "you are deriving `Hash` but have implemented `PartialEq` explicitly"
                     };

                     span_lint_and_then(
                         cx,
                         DERIVE_HASH_XOR_EQ,
                         span,
                         mess,
                         |diag| {
                             if let Some(local_def_id) = impl_id.as_local() {
                                 let hir_id = cx.tcx.hir().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: &TraitRef<'_>,
     ty: Ty<'tcx>,
     ord_is_automatically_derived: bool,
 ) {
     if_chain! {
         if let Some(ord_trait_def_id) = get_trait_def_id(cx, &paths::ORD);
         if let Some(partial_ord_trait_def_id) = cx.tcx.lang_items().partial_ord_trait();
         if let Some(def_id) = &trait_ref.trait_def_id();
         if *def_id == ord_trait_def_id;
         then {
             // 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 = is_automatically_derived(&cx.tcx.get_attrs(impl_id));

                 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.substs.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.hir().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: &TraitRef<'_>, ty: Ty<'tcx>) {
     if match_path(&trait_ref.path, &paths::CLONE_TRAIT) {
         if !is_copy(cx, ty) {
             return;
         }

         match *ty.kind() {
             ty::Adt(def, _) if def.is_union() => return,

             // Some types are not Clone by default but could be cloned “by hand” if necessary
             ty::Adt(def, substs) => {
                 for variant in &def.variants {
                     for field in &variant.fields {
                         if let ty::FnDef(..) = field.ty(cx.tcx, substs).kind() {
                             return;
                         }
                     }
                     for subst in substs {
                         if let ty::subst::GenericArgKind::Type(subst) = subst.unpack() {
                             if let ty::Param(_) = subst.kind() {
                                 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: &TraitRef<'_>,
     ty: Ty<'tcx>,
 ) {
     fn item_from_def_id<'tcx>(cx: &LateContext<'tcx>, def_id: DefId) -> &'tcx Item<'tcx> {
         let hir_id = cx.tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
         cx.tcx.hir().expect_item(hir_id)
     }

     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_chain! {
         if match_path(&trait_ref.path, &paths::SERDE_DESERIALIZE);
         if let ty::Adt(def, _) = ty.kind();
         if let Some(local_def_id) = def.did.as_local();
         let adt_hir_id = cx.tcx.hir().local_def_id_to_hir_id(local_def_id);
         if !is_allowed(cx, UNSAFE_DERIVE_DESERIALIZE, adt_hir_id);
         if cx.tcx.inherent_impls(def.did)
             .iter()
             .map(|imp_did| item_from_def_id(cx, *imp_did))
             .any(|imp| has_unsafe(cx, imp));
         then {
             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 Map = Map<'tcx>;

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

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

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

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

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

         walk_expr(self, expr);
     }

     fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
         NestedVisitorMap::All(self.cx.tcx.hir())
     }
 }
	use crate::utils::paths;
	use crate::utils::{
	get_trait_def_id, is_allowed, is_automatically_derived, is_copy, match_path, span_lint_and_help,
	span_lint_and_note, span_lint_and_then,
	};
	use if_chain::if_chain;
	use rustc_hir::def_id::DefId;
	use rustc_hir::intravisit::{walk_expr, walk_fn, walk_item, FnKind, NestedVisitorMap, Visitor};
	use rustc_hir::{
	BlockCheckMode, BodyId, Expr, ExprKind, FnDecl, HirId, Item, ItemKind, TraitRef, UnsafeSource, Unsafety,
	};
	use rustc_lint::{LateContext, LateLintPass};
	use rustc_middle::hir::map::Map;
	use rustc_middle::ty::{self, Ty};
	use rustc_session::{declare_lint_pass, declare_tool_lint};
	use rustc_span::source_map::Span;

	declare_clippy_lint! {
	/// What it does: Checks for deriving `Hash` but implementing `PartialEq`
	/// explicitly or vice versa.
	///
	/// 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)
	/// ```
	///
	/// Known problems: None.
	///
	/// Example:
	/// ```ignore
	/// #[derive(Hash)]
	/// struct Foo;
	///
	/// impl PartialEq for Foo {
	/// ...
	/// }
	/// ```
	pub DERIVE_HASH_XOR_EQ,
	correctness,
	"deriving `Hash` but implementing `PartialEq` explicitly"
	}

	declare_clippy_lint! {
	/// What it does: Checks for deriving `Ord` but implementing `PartialOrd`
	/// explicitly or vice versa.
	///
	/// 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()
	/// ```
	///
	/// Known problems: None.
	///
	/// 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;
	/// ```
	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 behaviour, these traits should
	/// agree and the behaviour 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.
	///
	/// Known problems: Bounds of generic types are sometimes wrong: https://github.com/rust-lang/rust/issues/26925
	///
	/// Example:
	/// ```rust,ignore
	/// #[derive(Copy)]
	/// struct Foo;
	///
	/// impl Clone for Foo {
	/// // ..
	/// }
	/// ```
	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 hold by another constructor.
	///
	/// Known problems: None.
	///
	/// 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
	/// }
	/// }
	/// ```
	pub UNSAFE_DERIVE_DESERIALIZE,
	pedantic,
	"deriving `serde::Deserialize` on a type that has methods using `unsafe`"
	}

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

	impl<'tcx> LateLintPass<'tcx> for Derive {
	fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx Item<'_>) {
	if let ItemKind::Impl {
	of_trait: Some(ref trait_ref),
	..
	} = item.kind
	{
	let ty = cx.tcx.type_of(cx.tcx.hir().local_def_id(item.hir_id));
	let is_automatically_derived = is_automatically_derived(&*item.attrs);

	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);
	} else {
	check_copy_clone(cx, item, trait_ref, ty);
	}
	}
	}
	}

	/// Implementation of the `DERIVE_HASH_XOR_EQ` lint.
	fn check_hash_peq<'tcx>(
	cx: &LateContext<'tcx>,
	span: Span,
	trait_ref: &TraitRef<'_>,
	ty: Ty<'tcx>,
	hash_is_automatically_derived: bool,
	) {
	if_chain! {
	if match_path(&trait_ref.path, &paths::HASH);
	if let Some(peq_trait_def_id) = cx.tcx.lang_items().eq_trait();
	if let Some(def_id) = &trait_ref.trait_def_id();
	if !def_id.is_local();
	then {
	// 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 = is_automatically_derived(&cx.tcx.get_attrs(impl_id));

	if peq_is_automatically_derived == hash_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.substs.type_at(1) == ty {
	let mess = if peq_is_automatically_derived {
	"you are implementing `Hash` explicitly but have derived `PartialEq`"
	} else {
	"you are deriving `Hash` but have implemented `PartialEq` explicitly"
	};

	span_lint_and_then(
	cx,
	DERIVE_HASH_XOR_EQ,
	span,
	mess,
	\|diag\| {
	if let Some(local_def_id) = impl_id.as_local() {
	let hir_id = cx.tcx.hir().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: &TraitRef<'_>,
	ty: Ty<'tcx>,
	ord_is_automatically_derived: bool,
	) {
	if_chain! {
	if let Some(ord_trait_def_id) = get_trait_def_id(cx, &paths::ORD);
	if let Some(partial_ord_trait_def_id) = cx.tcx.lang_items().partial_ord_trait();
	if let Some(def_id) = &trait_ref.trait_def_id();
	if *def_id == ord_trait_def_id;
	then {
	// 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 = is_automatically_derived(&cx.tcx.get_attrs(impl_id));

	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.substs.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.hir().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: &TraitRef<'_>, ty: Ty<'tcx>) {
	if match_path(&trait_ref.path, &paths::CLONE_TRAIT) {
	if !is_copy(cx, ty) {
	return;
	}

	match *ty.kind() {
	ty::Adt(def, _) if def.is_union() => return,

	// Some types are not Clone by default but could be cloned “by hand” if necessary
	ty::Adt(def, substs) => {
	for variant in &def.variants {
	for field in &variant.fields {
	if let ty::FnDef(..) = field.ty(cx.tcx, substs).kind() {
	return;
	}
	}
	for subst in substs {
	if let ty::subst::GenericArgKind::Type(subst) = subst.unpack() {
	if let ty::Param(_) = subst.kind() {
	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: &TraitRef<'_>,
	ty: Ty<'tcx>,
	) {
	fn item_from_def_id<'tcx>(cx: &LateContext<'tcx>, def_id: DefId) -> &'tcx Item<'tcx> {
	let hir_id = cx.tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
	cx.tcx.hir().expect_item(hir_id)
	}

	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_chain! {
	if match_path(&trait_ref.path, &paths::SERDE_DESERIALIZE);
	if let ty::Adt(def, _) = ty.kind();
	if let Some(local_def_id) = def.did.as_local();
	let adt_hir_id = cx.tcx.hir().local_def_id_to_hir_id(local_def_id);
	if !is_allowed(cx, UNSAFE_DERIVE_DESERIALIZE, adt_hir_id);
	if cx.tcx.inherent_impls(def.did)
	.iter()
	.map(\|imp_did\| item_from_def_id(cx, *imp_did))
	.any(\|imp\| has_unsafe(cx, imp));
	then {
	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 Map = Map<'tcx>;

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

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

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

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

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

	walk_expr(self, expr);
	}

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