rust-clippy/clippy_lints/src/derive.rs

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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,
};
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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,
};
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use rustc_lint::{LateContext, LateLintPass};
use rustc_middle::hir::map::Map;
use rustc_middle::ty::{self, Ty};
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use rustc_session::{declare_lint_pass, declare_tool_lint};
use rustc_span::source_map::Span;
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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 its 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:
///
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/// ```text
/// k1 == k2 ⇒ hash(k1) == hash(k2)
/// ```
///
/// **Known problems:** None.
///
/// **Example:**
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/// ```ignore
/// #[derive(Hash)]
/// struct Foo;
///
/// impl PartialEq for Foo {
/// ...
/// }
/// ```
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pub DERIVE_HASH_XOR_EQ,
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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 its 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"
}
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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,
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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 {
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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);
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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);
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if is_automatically_derived {
check_unsafe_derive_deserialize(cx, item, trait_ref, ty);
} else {
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check_copy_clone(cx, item, trait_ref, ty);
}
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}
}
}
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/// Implementation of the `DERIVE_HASH_XOR_EQ` lint.
fn check_hash_peq<'tcx>(
cx: &LateContext<'tcx>,
span: Span,
trait_ref: &TraitRef<'_>,
ty: Ty<'tcx>,
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hash_is_automatically_derived: bool,
) {
if_chain! {
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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));
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if peq_is_automatically_derived == hash_is_automatically_derived {
return;
}
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let trait_ref = cx.tcx.impl_trait_ref(impl_id).expect("must be a trait implementation");
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// 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"
};
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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>) {
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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,
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// Some types are not Clone by default but could be cloned “by hand” if necessary
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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;
}
}
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for subst in substs {
if let ty::subst::GenericArgKind::Type(subst) = subst.unpack() {
if let ty::Param(_) = subst.kind() {
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return;
}
}
}
}
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},
_ => (),
}
span_lint_and_note(
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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`",
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);
}
}
/// 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())
}
}