[rustc.git] / src / tools / clippy / clippy_lints / src / derive.rs

use clippy_utils::diagnostics::{span_lint_and_help, span_lint_and_note, span_lint_and_then};
use clippy_utils::paths;
use clippy_utils::ty::{implements_trait, is_copy};
use clippy_utils::{get_trait_def_id, is_automatically_derived, is_lint_allowed, match_def_path};
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, Impl, 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(Impl {
            of_trait: Some(ref trait_ref),
            ..
        }) = item.kind
        {
            let ty = cx.tcx.type_of(item.def_id);
            let attrs = cx.tcx.hir().attrs(item.hir_id());
            let is_automatically_derived = is_automatically_derived(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 let Some(peq_trait_def_id) = cx.tcx.lang_items().eq_trait();
        if let Some(def_id) = trait_ref.trait_def_id();
        if match_def_path(cx, def_id, &paths::HASH);
        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>) {
    let clone_id = match cx.tcx.lang_items().clone_trait() {
        Some(id) if trait_ref.trait_def_id() == Some(id) => id,
        _ => return,
    };
    let copy_id = match cx.tcx.lang_items().copy_trait() {
        Some(id) => id,
        None => 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().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).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;
    }

    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 let Some(trait_def_id) = trait_ref.trait_def_id();
        if match_def_path(cx, trait_def_id, &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_lint_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 {
            if let BlockCheckMode::UnsafeBlock(UnsafeSource::UserProvided) = block.rules {
                self.has_unsafe = true;
            }
        }

        walk_expr(self, expr);
    }

    fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
        NestedVisitorMap::All(self.cx.tcx.hir())
    }
}
Commit	Line	Data
cdc7bbd5 XL	1	use clippy_utils::diagnostics::{span_lint_and_help, span_lint_and_note, span_lint_and_then};
	2	use clippy_utils::paths;
	3	use clippy_utils::ty::{implements_trait, is_copy};
136023e0	4	use clippy_utils::{get_trait_def_id, is_automatically_derived, is_lint_allowed, match_def_path};
f20569fa XL	5	use if_chain::if_chain;
	6	use rustc_hir::def_id::DefId;
	7	use rustc_hir::intravisit::{walk_expr, walk_fn, walk_item, FnKind, NestedVisitorMap, Visitor};
	8	use rustc_hir::{
	9	BlockCheckMode, BodyId, Expr, ExprKind, FnDecl, HirId, Impl, Item, ItemKind, TraitRef, UnsafeSource, Unsafety,
	10	};
	11	use rustc_lint::{LateContext, LateLintPass};
	12	use rustc_middle::hir::map::Map;
	13	use rustc_middle::ty::{self, Ty};
	14	use rustc_session::{declare_lint_pass, declare_tool_lint};
17df50a5	15	use rustc_span::source_map::Span;
f20569fa XL	16
	17	declare_clippy_lint! {
	18	/// What it does: Checks for deriving `Hash` but implementing `PartialEq`
	19	/// explicitly or vice versa.
	20	///
	21	/// Why is this bad? The implementation of these traits must agree (for
	22	/// example for use with `HashMap`) so it’s probably a bad idea to use a
	23	/// default-generated `Hash` implementation with an explicitly defined
	24	/// `PartialEq`. In particular, the following must hold for any type:
	25	///
	26	/// ```text
	27	/// k1 == k2 ⇒ hash(k1) == hash(k2)
	28	/// ```
	29	///
	30	/// Known problems: None.
	31	///
	32	/// Example:
	33	/// ```ignore
	34	/// #[derive(Hash)]
	35	/// struct Foo;
	36	///
	37	/// impl PartialEq for Foo {
	38	/// ...
	39	/// }
	40	/// ```
	41	pub DERIVE_HASH_XOR_EQ,
	42	correctness,
	43	"deriving `Hash` but implementing `PartialEq` explicitly"
	44	}
	45
	46	declare_clippy_lint! {
	47	/// What it does: Checks for deriving `Ord` but implementing `PartialOrd`
	48	/// explicitly or vice versa.
	49	///
	50	/// Why is this bad? The implementation of these traits must agree (for
	51	/// example for use with `sort`) so it’s probably a bad idea to use a
	52	/// default-generated `Ord` implementation with an explicitly defined
	53	/// `PartialOrd`. In particular, the following must hold for any type
	54	/// implementing `Ord`:
	55	///
	56	/// ```text
	57	/// k1.cmp(&k2) == k1.partial_cmp(&k2).unwrap()
	58	/// ```
	59	///
	60	/// Known problems: None.
	61	///
	62	/// Example:
	63	///
	64	/// ```rust,ignore
	65	/// #[derive(Ord, PartialEq, Eq)]
	66	/// struct Foo;
	67	///
	68	/// impl PartialOrd for Foo {
	69	/// ...
	70	/// }
	71	/// ```
	72	/// Use instead:
	73	/// ```rust,ignore
	74	/// #[derive(PartialEq, Eq)]
	75	/// struct Foo;
	76	///
	77	/// impl PartialOrd for Foo {
	78	/// fn partial_cmp(&self, other: &Foo) -> Option<Ordering> {
	79	/// Some(self.cmp(other))
80	/// }
81	/// }
82	///
83	/// impl Ord for Foo {
84	/// ...
85	/// }
86	/// ```
87	/// or, if you don't need a custom ordering:
88	/// ```rust,ignore
89	/// #[derive(Ord, PartialOrd, PartialEq, Eq)]
90	/// struct Foo;
91	/// ```
92	pub DERIVE_ORD_XOR_PARTIAL_ORD,
93	correctness,
94	"deriving `Ord` but implementing `PartialOrd` explicitly"
95	}
96
97	declare_clippy_lint! {
98	/// What it does: Checks for explicit `Clone` implementations for `Copy`
99	/// types.
100	///
101	/// Why is this bad? To avoid surprising behaviour, these traits should
102	/// agree and the behaviour of `Copy` cannot be overridden. In almost all
103	/// situations a `Copy` type should have a `Clone` implementation that does
104	/// nothing more than copy the object, which is what `#[derive(Copy, Clone)]`
105	/// gets you.
106	///
107	/// Known problems: Bounds of generic types are sometimes wrong: https://github.com/rust-lang/rust/issues/26925
108	///
109	/// Example:
110	/// ```rust,ignore
111	/// #[derive(Copy)]
112	/// struct Foo;
113	///
114	/// impl Clone for Foo {
115	/// // ..
116	/// }
117	/// ```
118	pub EXPL_IMPL_CLONE_ON_COPY,
119	pedantic,
120	"implementing `Clone` explicitly on `Copy` types"
121	}
122
123	declare_clippy_lint! {
124	/// What it does: Checks for deriving `serde::Deserialize` on a type that
125	/// has methods using `unsafe`.
126	///
127	/// Why is this bad? Deriving `serde::Deserialize` will create a constructor
128	/// that may violate invariants hold by another constructor.
129	///
130	/// Known problems: None.
131	///
132	/// Example:
133	///
134	/// ```rust,ignore
135	/// use serde::Deserialize;
136	///
137	/// #[derive(Deserialize)]
138	/// pub struct Foo {
139	/// // ..
140	/// }
141	///
142	/// impl Foo {
143	/// pub fn new() -> Self {
144	/// // setup here ..
145	/// }
146	///
147	/// pub unsafe fn parts() -> (&str, &str) {
148	/// // assumes invariants hold
149	/// }
150	/// }
151	/// ```
152	pub UNSAFE_DERIVE_DESERIALIZE,
153	pedantic,
154	"deriving `serde::Deserialize` on a type that has methods using `unsafe`"
155	}
156
157	declare_lint_pass!(Derive => [
158	EXPL_IMPL_CLONE_ON_COPY,
159	DERIVE_HASH_XOR_EQ,
160	DERIVE_ORD_XOR_PARTIAL_ORD,
161	UNSAFE_DERIVE_DESERIALIZE
162	]);
163
164	impl<'tcx> LateLintPass<'tcx> for Derive {
165	fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx Item<'_>) {
166	if let ItemKind::Impl(Impl {
167	of_trait: Some(ref trait_ref),
168	..
169	}) = item.kind
170	{
171	let ty = cx.tcx.type_of(item.def_id);
172	let attrs = cx.tcx.hir().attrs(item.hir_id());
173	let is_automatically_derived = is_automatically_derived(attrs);
174
175	check_hash_peq(cx, item.span, trait_ref, ty, is_automatically_derived);
176	check_ord_partial_ord(cx, item.span, trait_ref, ty, is_automatically_derived);
177
178	if is_automatically_derived {
179	check_unsafe_derive_deserialize(cx, item, trait_ref, ty);
180	} else {
181	check_copy_clone(cx, item, trait_ref, ty);
182	}
183	}
184	}
185	}
186
187	/// Implementation of the `DERIVE_HASH_XOR_EQ` lint.
188	fn check_hash_peq<'tcx>(
189	cx: &LateContext<'tcx>,
190	span: Span,
191	trait_ref: &TraitRef<'_>,
192	ty: Ty<'tcx>,
193	hash_is_automatically_derived: bool,
194	) {
195	if_chain! {
196	if let Some(peq_trait_def_id) = cx.tcx.lang_items().eq_trait();
197	if let Some(def_id) = trait_ref.trait_def_id();
198	if match_def_path(cx, def_id, &paths::HASH);
199	then {
200	// Look for the PartialEq implementations for `ty`
201	cx.tcx.for_each_relevant_impl(peq_trait_def_id, ty, \|impl_id\| {
cdc7bbd5	202	let peq_is_automatically_derived = is_automatically_derived(cx.tcx.get_attrs(impl_id));
f20569fa XL	203
	204	if peq_is_automatically_derived == hash_is_automatically_derived {
	205	return;
	206	}
	207
	208	let trait_ref = cx.tcx.impl_trait_ref(impl_id).expect("must be a trait implementation");
	209
	210	// Only care about `impl PartialEq<Foo> for Foo`
	211	// For `impl PartialEq<B> for A, input_types is [A, B]
	212	if trait_ref.substs.type_at(1) == ty {
	213	let mess = if peq_is_automatically_derived {
	214	"you are implementing `Hash` explicitly but have derived `PartialEq`"
	215	} else {
	216	"you are deriving `Hash` but have implemented `PartialEq` explicitly"
	217	};
	218
	219	span_lint_and_then(
	220	cx,
	221	DERIVE_HASH_XOR_EQ,
	222	span,
	223	mess,
	224	\|diag\| {
	225	if let Some(local_def_id) = impl_id.as_local() {
	226	let hir_id = cx.tcx.hir().local_def_id_to_hir_id(local_def_id);
	227	diag.span_note(
	228	cx.tcx.hir().span(hir_id),
	229	"`PartialEq` implemented here"
	230	);
	231	}
	232	}
	233	);
	234	}
	235	});
	236	}
	237	}
	238	}
	239
	240	/// Implementation of the `DERIVE_ORD_XOR_PARTIAL_ORD` lint.
	241	fn check_ord_partial_ord<'tcx>(
	242	cx: &LateContext<'tcx>,
	243	span: Span,
	244	trait_ref: &TraitRef<'_>,
	245	ty: Ty<'tcx>,
	246	ord_is_automatically_derived: bool,
	247	) {
	248	if_chain! {
	249	if let Some(ord_trait_def_id) = get_trait_def_id(cx, &paths::ORD);
	250	if let Some(partial_ord_trait_def_id) = cx.tcx.lang_items().partial_ord_trait();
	251	if let Some(def_id) = &trait_ref.trait_def_id();
	252	if *def_id == ord_trait_def_id;
	253	then {
	254	// Look for the PartialOrd implementations for `ty`
	255	cx.tcx.for_each_relevant_impl(partial_ord_trait_def_id, ty, \|impl_id\| {
cdc7bbd5	256	let partial_ord_is_automatically_derived = is_automatically_derived(cx.tcx.get_attrs(impl_id));
f20569fa XL	257
	258	if partial_ord_is_automatically_derived == ord_is_automatically_derived {
	259	return;
	260	}
	261
	262	let trait_ref = cx.tcx.impl_trait_ref(impl_id).expect("must be a trait implementation");
	263
	264	// Only care about `impl PartialOrd<Foo> for Foo`
	265	// For `impl PartialOrd<B> for A, input_types is [A, B]
	266	if trait_ref.substs.type_at(1) == ty {
	267	let mess = if partial_ord_is_automatically_derived {
	268	"you are implementing `Ord` explicitly but have derived `PartialOrd`"
	269	} else {
	270	"you are deriving `Ord` but have implemented `PartialOrd` explicitly"
	271	};
	272
	273	span_lint_and_then(
	274	cx,
	275	DERIVE_ORD_XOR_PARTIAL_ORD,
	276	span,
	277	mess,
	278	\|diag\| {
	279	if let Some(local_def_id) = impl_id.as_local() {
	280	let hir_id = cx.tcx.hir().local_def_id_to_hir_id(local_def_id);
	281	diag.span_note(
	282	cx.tcx.hir().span(hir_id),
	283	"`PartialOrd` implemented here"
	284	);
	285	}
	286	}
	287	);
	288	}
	289	});
	290	}
	291	}
	292	}
	293
	294	/// Implementation of the `EXPL_IMPL_CLONE_ON_COPY` lint.
	295	fn check_copy_clone<'tcx>(cx: &LateContext<'tcx>, item: &Item<'_>, trait_ref: &TraitRef<'_>, ty: Ty<'tcx>) {
cdc7bbd5 XL	296	let clone_id = match cx.tcx.lang_items().clone_trait() {
	297	Some(id) if trait_ref.trait_def_id() == Some(id) => id,
	298	_ => return,
	299	};
	300	let copy_id = match cx.tcx.lang_items().copy_trait() {
	301	Some(id) => id,
	302	None => return,
	303	};
	304	let (ty_adt, ty_subs) = match *ty.kind() {
	305	// Unions can't derive clone.
	306	ty::Adt(adt, subs) if !adt.is_union() => (adt, subs),
	307	_ => return,
	308	};
	309	// If the current self type doesn't implement Copy (due to generic constraints), search to see if
	310	// there's a Copy impl for any instance of the adt.
	311	if !is_copy(cx, ty) {
	312	if ty_subs.non_erasable_generics().next().is_some() {
17df50a5 XL	313	let has_copy_impl = cx.tcx.all_local_trait_impls(()).get(&copy_id).map_or(false, \|impls\| {
	314	impls
	315	.iter()
	316	.any(\|&id\| matches!(cx.tcx.type_of(id).kind(), ty::Adt(adt, _) if ty_adt.did == adt.did))
	317	});
cdc7bbd5 XL	318	if !has_copy_impl {
	319	return;
	320	}
	321	} else {
f20569fa XL	322	return;
f20569fa XL	323	}
f20569fa	324	}
cdc7bbd5 XL	325	// Derive constrains all generic types to requiring Clone. Check if any type is not constrained for
	326	// this impl.
	327	if ty_subs.types().any(\|ty\| !implements_trait(cx, ty, clone_id, &[])) {
	328	return;
	329	}
	330
	331	span_lint_and_note(
	332	cx,
	333	EXPL_IMPL_CLONE_ON_COPY,
	334	item.span,
	335	"you are implementing `Clone` explicitly on a `Copy` type",
	336	Some(item.span),
	337	"consider deriving `Clone` or removing `Copy`",
	338	);
f20569fa XL	339	}
	340
	341	/// Implementation of the `UNSAFE_DERIVE_DESERIALIZE` lint.
	342	fn check_unsafe_derive_deserialize<'tcx>(
	343	cx: &LateContext<'tcx>,
	344	item: &Item<'_>,
	345	trait_ref: &TraitRef<'_>,
	346	ty: Ty<'tcx>,
	347	) {
	348	fn item_from_def_id<'tcx>(cx: &LateContext<'tcx>, def_id: DefId) -> &'tcx Item<'tcx> {
	349	let hir_id = cx.tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
	350	cx.tcx.hir().expect_item(hir_id)
	351	}
	352
	353	fn has_unsafe<'tcx>(cx: &LateContext<'tcx>, item: &'tcx Item<'_>) -> bool {
	354	let mut visitor = UnsafeVisitor { cx, has_unsafe: false };
	355	walk_item(&mut visitor, item);
	356	visitor.has_unsafe
	357	}
	358
	359	if_chain! {
	360	if let Some(trait_def_id) = trait_ref.trait_def_id();
	361	if match_def_path(cx, trait_def_id, &paths::SERDE_DESERIALIZE);
	362	if let ty::Adt(def, _) = ty.kind();
	363	if let Some(local_def_id) = def.did.as_local();
	364	let adt_hir_id = cx.tcx.hir().local_def_id_to_hir_id(local_def_id);
136023e0	365	if !is_lint_allowed(cx, UNSAFE_DERIVE_DESERIALIZE, adt_hir_id);
f20569fa XL	366	if cx.tcx.inherent_impls(def.did)
	367	.iter()
	368	.map(\|imp_did\| item_from_def_id(cx, *imp_did))
	369	.any(\|imp\| has_unsafe(cx, imp));
	370	then {
	371	span_lint_and_help(
	372	cx,
	373	UNSAFE_DERIVE_DESERIALIZE,
	374	item.span,
	375	"you are deriving `serde::Deserialize` on a type that has methods using `unsafe`",
	376	None,
	377	"consider implementing `serde::Deserialize` manually. See https://serde.rs/impl-deserialize.html"
	378	);
	379	}
	380	}
	381	}
	382
	383	struct UnsafeVisitor<'a, 'tcx> {
	384	cx: &'a LateContext<'tcx>,
	385	has_unsafe: bool,
	386	}
	387
	388	impl<'tcx> Visitor<'tcx> for UnsafeVisitor<'_, 'tcx> {
	389	type Map = Map<'tcx>;
	390
	391	fn visit_fn(&mut self, kind: FnKind<'tcx>, decl: &'tcx FnDecl<'_>, body_id: BodyId, span: Span, id: HirId) {
	392	if self.has_unsafe {
	393	return;
	394	}
	395
	396	if_chain! {
	397	if let Some(header) = kind.header();
	398	if let Unsafety::Unsafe = header.unsafety;
	399	then {
	400	self.has_unsafe = true;
	401	}
	402	}
	403
	404	walk_fn(self, kind, decl, body_id, span, id);
	405	}
	406
	407	fn visit_expr(&mut self, expr: &'tcx Expr<'_>) {
	408	if self.has_unsafe {
	409	return;
	410	}
	411
	412	if let ExprKind::Block(block, _) = expr.kind {
136023e0 XL	413	if let BlockCheckMode::UnsafeBlock(UnsafeSource::UserProvided) = block.rules {
136023e0 XL	414	self.has_unsafe = true;
f20569fa XL	415	}
	416	}
	417
	418	walk_expr(self, expr);
	419	}
	420
	421	fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
	422	NestedVisitorMap::All(self.cx.tcx.hir())
	423	}
	424	}