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Fix FP when using raw pointers as hashed keys

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This commit is contained in:
Kneasle 2021-09-05 21:58:47 +01:00
parent a64b7698a4
commit e0090735f1
3 changed files with 40 additions and 15 deletions
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33
clippy_lints/src/mut_key.rs
View File

@ -103,26 +103,39 @@ fn check_sig<'tcx>(cx: &LateContext<'tcx>, item_hir_id: hir::HirId, decl: &hir::
fn check_ty<'tcx>(cx: &LateContext<'tcx>, span: Span, ty: Ty<'tcx>) {
let ty = ty.peel_refs();
if let Adt(def, substs) = ty.kind() {
if [sym::hashmap_type, sym::BTreeMap, sym::hashset_type, sym::BTreeMap]
let is_map_type = [sym::hashmap_type, sym::BTreeMap, sym::hashset_type, sym::BTreeMap]
.iter()
.any(|diag_item| cx.tcx.is_diagnostic_item(*diag_item, def.did))
&& is_mutable_type(cx, substs.type_at(0), span)
{
.any(|diag_item| cx.tcx.is_diagnostic_item(*diag_item, def.did));
if is_map_type && is_mutable_type(cx, substs.type_at(0), span, true) {
span_lint(cx, MUTABLE_KEY_TYPE, span, "mutable key type");
}
}
}
fn is_mutable_type<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>, span: Span) -> bool {
fn is_mutable_type<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>, span: Span, is_top_level_type: bool) -> bool {
match *ty.kind() {
RawPtr(TypeAndMut { ty: inner_ty, mutbl }) | Ref(_, inner_ty, mutbl) => {
mutbl == hir::Mutability::Mut || is_mutable_type(cx, inner_ty, span)
RawPtr(TypeAndMut { ty: inner_ty, mutbl }) => {
if is_top_level_type {
// Raw pointers are hashed by the address they point to, not what is pointed to.
// Therefore, using a raw pointer to any type as the top-level key type is OK.
// Using raw pointers _in_ the key type is not, because the wrapper type could
// provide a custom `impl` for `Hash` (which could deref the raw pointer).
//
// see:
// - clippy issue: https://github.com/rust-lang/rust-clippy/issues/6745
// - std code: https://github.com/rust-lang/rust/blob/1.54.0/library/core/src/hash/mod.rs#L717-L736
false
} else {
mutbl == hir::Mutability::Mut || is_mutable_type(cx, inner_ty, span, false)
}
},
Slice(inner_ty) => is_mutable_type(cx, inner_ty, span),
Ref(_, inner_ty, mutbl) => mutbl == hir::Mutability::Mut || is_mutable_type(cx, inner_ty, span, false),
Slice(inner_ty) => is_mutable_type(cx, inner_ty, span, false),
Array(inner_ty, size) => {
size.try_eval_usize(cx.tcx, cx.param_env).map_or(true, |u| u != 0) && is_mutable_type(cx, inner_ty, span)
size.try_eval_usize(cx.tcx, cx.param_env).map_or(true, |u| u != 0)
&& is_mutable_type(cx, inner_ty, span, false)
},
Tuple(..) => ty.tuple_fields().any(|ty| is_mutable_type(cx, ty, span)),
Tuple(..) => ty.tuple_fields().any(|ty| is_mutable_type(cx, ty, span, false)),
Adt(..) => {
!ty.has_escaping_bound_vars()
&& cx.tcx.layout_of(cx.param_env.and(ty)).is_ok()

14
tests/ui/mut_key.rs
View File

@ -1,3 +1,4 @@
use std::cell::Cell;
use std::collections::{HashMap, HashSet};
use std::hash::{Hash, Hasher};
use std::sync::atomic::{AtomicUsize, Ordering::Relaxed};
@ -31,11 +32,19 @@ fn should_not_take_this_arg(m: &mut HashMap<Key, usize>, _n: usize) -> HashSet<K
fn this_is_ok(_m: &mut HashMap<usize, Key>) {}
// Raw pointers are hashed by the address they point to, so it doesn't matter if they point to a
// type with interior mutability. See:
// - clippy issue: https://github.com/rust-lang/rust-clippy/issues/6745
// - std lib: https://github.com/rust-lang/rust/blob/1.54.0/library/core/src/hash/mod.rs#L717-L736
// So these are OK:
fn raw_ptr_is_ok(_m: &mut HashMap<*const Key, ()>) {}
fn raw_mut_ptr_is_ok(_m: &mut HashMap<*mut Key, ()>) {}
#[allow(unused)]
trait Trait {
type AssociatedType;
fn trait_fn(&self, set: std::collections::HashSet<Self::AssociatedType>);
fn trait_fn(&self, set: HashSet<Self::AssociatedType>);
}
fn generics_are_ok_too<K>(_m: &mut HashSet<K>) {
@ -52,4 +61,7 @@ fn main() {
tuples::<Key>(&mut HashMap::new());
tuples::<()>(&mut HashMap::new());
tuples_bad::<()>(&mut HashMap::new());
raw_ptr_is_ok(&mut HashMap::new());
raw_mut_ptr_is_ok(&mut HashMap::new());
}

8
tests/ui/mut_key.stderr
View File

@ -1,5 +1,5 @@
error: mutable key type
--> $DIR/mut_key.rs:27:32
--> $DIR/mut_key.rs:28:32
|
LL | fn should_not_take_this_arg(m: &mut HashMap<Key, usize>, _n: usize) -> HashSet<Key> {
| ^^^^^^^^^^^^^^^^^^^^^^^^
@ -7,19 +7,19 @@ LL | fn should_not_take_this_arg(m: &mut HashMap<Key, usize>, _n: usize) -> Hash
= note: `-D clippy::mutable-key-type` implied by `-D warnings`
error: mutable key type
--> $DIR/mut_key.rs:27:72
--> $DIR/mut_key.rs:28:72
|
LL | fn should_not_take_this_arg(m: &mut HashMap<Key, usize>, _n: usize) -> HashSet<Key> {
| ^^^^^^^^^^^^
error: mutable key type
--> $DIR/mut_key.rs:28:5
--> $DIR/mut_key.rs:29:5
|
LL | let _other: HashMap<Key, bool> = HashMap::new();
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error: mutable key type
--> $DIR/mut_key.rs:47:22
--> $DIR/mut_key.rs:56:22
|
LL | fn tuples_bad<U>(_m: &mut HashMap<(Key, U), bool>) {}
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^