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fix a FP in interior_mutable_const

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fix a false positive in two `interior_mutable_const` lints where a constant with enums gets linted
even if it uses a clearly unfrozen variant. Note that the code uses the MIR interpreter, which
the author of #3962 thought unlikely to be a solution. This might be over-engineering;
but, I think it's important to be able to work with the 'http' crate (#3825).
This commit is contained in:
rail 2020-10-01 10:51:49 +13:00
parent be8160878a
commit f58a1695a6
6 changed files with 539 additions and 35 deletions
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170
clippy_lints/src/non_copy_const.rs
View File

@ -5,11 +5,15 @@
use std::ptr;
use rustc_hir::def::{DefKind, Res};
use rustc_hir::{Expr, ExprKind, ImplItem, ImplItemKind, Item, ItemKind, Node, TraitItem, TraitItemKind, UnOp};
use rustc_hir::def_id::DefId;
use rustc_hir::{
BodyId, Expr, ExprKind, HirId, ImplItem, ImplItemKind, Item, ItemKind, Node, TraitItem, TraitItemKind, UnOp,
};
use rustc_infer::traits::specialization_graph;
use rustc_lint::{LateContext, LateLintPass, Lint};
use rustc_middle::mir::interpret::{ConstValue, ErrorHandled};
use rustc_middle::ty::adjustment::Adjust;
use rustc_middle::ty::{AssocKind, Ty};
use rustc_middle::ty::{self, AssocKind, Const, Ty};
use rustc_session::{declare_lint_pass, declare_tool_lint};
use rustc_span::{InnerSpan, Span, DUMMY_SP};
use rustc_typeck::hir_ty_to_ty;
@ -36,14 +40,17 @@ declare_clippy_lint! {
/// `std::sync::ONCE_INIT` constant). In this case the use of `const` is legit,
/// and this lint should be suppressed.
///
/// When an enum has variants with interior mutability, use of its non interior mutable
/// variants can generate false positives. See issue
/// [#3962](https://github.com/rust-lang/rust-clippy/issues/3962)
/// Even though the lint avoids triggering on a constant whose type has enums that have variants
/// with interior mutability, and its value uses non interior mutable variants (see
/// [#3962](https://github.com/rust-lang/rust-clippy/issues/3962) and
/// [#3825](https://github.com/rust-lang/rust-clippy/issues/3825) for examples);
/// it complains about associated constants without default values only based on its types;
/// which might not be preferable.
/// There're other enums plus associated constants cases that the lint cannot handle.
///
/// Types that have underlying or potential interior mutability trigger the lint whether
/// the interior mutable field is used or not. See issues
/// [#5812](https://github.com/rust-lang/rust-clippy/issues/5812) and
/// [#3825](https://github.com/rust-lang/rust-clippy/issues/3825)
///
/// **Example:**
/// ```rust
@ -105,6 +112,79 @@ declare_clippy_lint! {
"referencing `const` with interior mutability"
}
fn is_unfrozen<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>) -> bool {
// Ignore types whose layout is unknown since `is_freeze` reports every generic types as `!Freeze`,
// making it indistinguishable from `UnsafeCell`. i.e. it isn't a tool to prove a type is
// 'unfrozen'. However, this code causes a false negative in which
// a type contains a layout-unknown type, but also a unsafe cell like `const CELL: Cell<T>`.
// Yet, it's better than `ty.has_type_flags(TypeFlags::HAS_TY_PARAM | TypeFlags::HAS_PROJECTION)`
// since it works when a pointer indirection involves (`Cell<*const T>`).
// Making up a `ParamEnv` where every generic params and assoc types are `Freeze`is another option;
// but I'm not sure whether it's a decent way, if possible.
cx.tcx.layout_of(cx.param_env.and(ty)).is_ok() && !ty.is_freeze(cx.tcx.at(DUMMY_SP), cx.param_env)
}
fn is_value_unfrozen_raw<'tcx>(
cx: &LateContext<'tcx>,
result: Result<ConstValue<'tcx>, ErrorHandled>,
ty: Ty<'tcx>,
) -> bool {
fn inner<'tcx>(cx: &LateContext<'tcx>, val: &'tcx Const<'tcx>) -> bool {
match val.ty.kind() {
// the fact that we have to dig into every structs to search enums
// leads us to the point checking `UnsafeCell` directly is the only option.
ty::Adt(ty_def, ..) if Some(ty_def.did) == cx.tcx.lang_items().unsafe_cell_type() => true,
ty::Array(..) | ty::Adt(..) | ty::Tuple(..) => {
let val = cx.tcx.destructure_const(cx.param_env.and(val));
val.fields.iter().any(|field| inner(cx, field))
},
_ => false,
}
}
result.map_or_else(
|err| {
// Consider `TooGeneric` cases as being unfrozen.
// This causes a false positive where an assoc const whose type is unfrozen
// have a value that is a frozen variant with a generic param (an example is
// `declare_interior_mutable_const::enums::BothOfCellAndGeneric::GENERIC_VARIANT`).
// However, it prevents a number of false negatives that is, I think, important:
// 1. assoc consts in trait defs referring to consts of themselves
// (an example is `declare_interior_mutable_const::traits::ConcreteTypes::ANOTHER_ATOMIC`).
// 2. a path expr referring to assoc consts whose type is doesn't have
// any frozen variants in trait defs (i.e. without substitute for `Self`).
// (e.g. borrowing `borrow_interior_mutable_const::trait::ConcreteTypes::ATOMIC`)
// 3. similar to the false positive above;
// but the value is an unfrozen variant, or the type has no enums. (An example is
// `declare_interior_mutable_const::enums::BothOfCellAndGeneric::UNFROZEN_VARIANT`
// and `declare_interior_mutable_const::enums::BothOfCellAndGeneric::NO_ENUM`).
// One might be able to prevent these FNs correctly, and replace this with `false`;
// e.g. implementing `has_frozen_variant` described above, and not running this function
// when the type doesn't have any frozen variants would be the 'correct' way for the 2nd
// case (that actually removes another suboptimal behavior (I won't say 'false positive') where,
// similar to 2., but with the a frozen variant) (e.g. borrowing
// `borrow_interior_mutable_const::enums::AssocConsts::TO_BE_FROZEN_VARIANT`).
// I chose this way because unfrozen enums as assoc consts are rare (or, hopefully, none).
err == ErrorHandled::TooGeneric
},
|val| inner(cx, Const::from_value(cx.tcx, val, ty)),
)
}
fn is_value_unfrozen_poly<'tcx>(cx: &LateContext<'tcx>, body_id: BodyId, ty: Ty<'tcx>) -> bool {
let result = cx.tcx.const_eval_poly(body_id.hir_id.owner.to_def_id());
is_value_unfrozen_raw(cx, result, ty)
}
fn is_value_unfrozen_expr<'tcx>(cx: &LateContext<'tcx>, hir_id: HirId, def_id: DefId, ty: Ty<'tcx>) -> bool {
let substs = cx.typeck_results().node_substs(hir_id);
let result = cx
.tcx
.const_eval_resolve(cx.param_env, ty::WithOptConstParam::unknown(def_id), substs, None, None);
is_value_unfrozen_raw(cx, result, ty)
}
#[derive(Copy, Clone)]
enum Source {
Item { item: Span },
@ -130,19 +210,7 @@ impl Source {
}
}
fn verify_ty_bound<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>, source: Source) {
// Ignore types whose layout is unknown since `is_freeze` reports every generic types as `!Freeze`,
// making it indistinguishable from `UnsafeCell`. i.e. it isn't a tool to prove a type is
// 'unfrozen'. However, this code causes a false negative in which
// a type contains a layout-unknown type, but also a unsafe cell like `const CELL: Cell<T>`.
// Yet, it's better than `ty.has_type_flags(TypeFlags::HAS_TY_PARAM | TypeFlags::HAS_PROJECTION)`
// since it works when a pointer indirection involves (`Cell<*const T>`).
// Making up a `ParamEnv` where every generic params and assoc types are `Freeze`is another option;
// but I'm not sure whether it's a decent way, if possible.
if cx.tcx.layout_of(cx.param_env.and(ty)).is_err() || ty.is_freeze(cx.tcx.at(DUMMY_SP), cx.param_env) {
return;
}
fn lint(cx: &LateContext<'_>, source: Source) {
let (lint, msg, span) = source.lint();
span_lint_and_then(cx, lint, span, msg, |diag| {
if span.from_expansion() {
@ -165,24 +233,44 @@ declare_lint_pass!(NonCopyConst => [DECLARE_INTERIOR_MUTABLE_CONST, BORROW_INTER
impl<'tcx> LateLintPass<'tcx> for NonCopyConst {
fn check_item(&mut self, cx: &LateContext<'tcx>, it: &'tcx Item<'_>) {
if let ItemKind::Const(hir_ty, ..) = &it.kind {
if let ItemKind::Const(hir_ty, body_id) = it.kind {
let ty = hir_ty_to_ty(cx.tcx, hir_ty);
verify_ty_bound(cx, ty, Source::Item { item: it.span });
if is_unfrozen(cx, ty) && is_value_unfrozen_poly(cx, body_id, ty) {
lint(cx, Source::Item { item: it.span });
}
}
}
fn check_trait_item(&mut self, cx: &LateContext<'tcx>, trait_item: &'tcx TraitItem<'_>) {
if let TraitItemKind::Const(hir_ty, ..) = &trait_item.kind {
if let TraitItemKind::Const(hir_ty, body_id_opt) = &trait_item.kind {
let ty = hir_ty_to_ty(cx.tcx, hir_ty);
// Normalize assoc types because ones originated from generic params
// bounded other traits could have their bound.
let normalized = cx.tcx.normalize_erasing_regions(cx.param_env, ty);
verify_ty_bound(cx, normalized, Source::Assoc { item: trait_item.span });
if is_unfrozen(cx, normalized)
// When there's no default value, lint it only according to its type;
// in other words, lint consts whose value *could* be unfrozen, not definitely is.
// This feels inconsistent with how the lint treats generic types,
// which avoids linting types which potentially become unfrozen.
// One could check whether a unfrozen type have a *frozen variant*
// (like `body_id_opt.map_or_else(|| !has_frozen_variant(...), ...)`),
// and do the same as the case of generic types at impl items.
// Note that it isn't sufficient to check if it has an enum
// since all of that enum's variants can be unfrozen:
// i.e. having an enum doesn't necessary mean a type has a frozen variant.
// And, implementing it isn't a trivial task; it'll probably end up
// re-implementing the trait predicate evaluation specific to `Freeze`.
&& body_id_opt.map_or(true, |body_id| is_value_unfrozen_poly(cx, body_id, normalized))
{
lint(cx, Source::Assoc { item: trait_item.span });
}
}
}
fn check_impl_item(&mut self, cx: &LateContext<'tcx>, impl_item: &'tcx ImplItem<'_>) {
if let ImplItemKind::Const(hir_ty, ..) = &impl_item.kind {
if let ImplItemKind::Const(hir_ty, body_id) = &impl_item.kind {
let item_hir_id = cx.tcx.hir().get_parent_node(impl_item.hir_id);
let item = cx.tcx.hir().expect_item(item_hir_id);
@ -209,16 +297,23 @@ impl<'tcx> LateLintPass<'tcx> for NonCopyConst {
),
))
.is_err();
// If there were a function like `has_frozen_variant` described above,
// we should use here as a frozen variant is a potential to be frozen
// similar to unknown layouts.
// e.g. `layout_of(...).is_err() || has_frozen_variant(...);`
then {
let ty = hir_ty_to_ty(cx.tcx, hir_ty);
let normalized = cx.tcx.normalize_erasing_regions(cx.param_env, ty);
verify_ty_bound(
cx,
normalized,
Source::Assoc {
item: impl_item.span,
},
);
if is_unfrozen(cx, normalized)
&& is_value_unfrozen_poly(cx, *body_id, normalized)
{
lint(
cx,
Source::Assoc {
item: impl_item.span,
},
);
}
}
}
},
@ -226,7 +321,10 @@ impl<'tcx> LateLintPass<'tcx> for NonCopyConst {
let ty = hir_ty_to_ty(cx.tcx, hir_ty);
// Normalize assoc types originated from generic params.
let normalized = cx.tcx.normalize_erasing_regions(cx.param_env, ty);
verify_ty_bound(cx, normalized, Source::Assoc { item: impl_item.span });
if is_unfrozen(cx, ty) && is_value_unfrozen_poly(cx, *body_id, normalized) {
lint(cx, Source::Assoc { item: impl_item.span });
}
},
_ => (),
}
@ -241,8 +339,8 @@ impl<'tcx> LateLintPass<'tcx> for NonCopyConst {
}
// Make sure it is a const item.
match qpath_res(cx, qpath, expr.hir_id) {
Res::Def(DefKind::Const | DefKind::AssocConst, _) => {},
let item_def_id = match qpath_res(cx, qpath, expr.hir_id) {
Res::Def(DefKind::Const | DefKind::AssocConst, did) => did,
_ => return,
};
@ -319,7 +417,9 @@ impl<'tcx> LateLintPass<'tcx> for NonCopyConst {
cx.typeck_results().expr_ty(dereferenced_expr)
};
verify_ty_bound(cx, ty, Source::Expr { expr: expr.span });
if is_unfrozen(cx, ty) && is_value_unfrozen_expr(cx, expr.hir_id, item_def_id, ty) {
lint(cx, Source::Expr { expr: expr.span });
}
}
}
}

16
tests/ui/borrow_interior_mutable_const/auxiliary/helper.rs Normal file
View File

@ -0,0 +1,16 @@
// this file solely exists to test constants defined in foreign crates.
// As the most common case is the `http` crate, it replicates `http::HeadewrName`'s structure.
#![allow(clippy::declare_interior_mutable_const)]
use std::sync::atomic::AtomicUsize;
enum Private<T> {
ToBeUnfrozen(T),
Frozen(usize),
}
pub struct Wrapper(Private<AtomicUsize>);
pub const WRAPPED_PRIVATE_UNFROZEN_VARIANT: Wrapper = Wrapper(Private::ToBeUnfrozen(AtomicUsize::new(6)));
pub const WRAPPED_PRIVATE_FROZEN_VARIANT: Wrapper = Wrapper(Private::Frozen(7));

101
tests/ui/borrow_interior_mutable_const/enums.rs Normal file
View File

@ -0,0 +1,101 @@
// aux-build:helper.rs
#![warn(clippy::borrow_interior_mutable_const)]
#![allow(clippy::declare_interior_mutable_const)]
// this file (mostly) replicates its `declare` counterpart. Please see it for more discussions.
extern crate helper;
use std::cell::Cell;
use std::sync::atomic::AtomicUsize;
enum OptionalCell {
Unfrozen(Cell<bool>),
Frozen,
}
const UNFROZEN_VARIANT: OptionalCell = OptionalCell::Unfrozen(Cell::new(true));
const FROZEN_VARIANT: OptionalCell = OptionalCell::Frozen;
fn borrow_optional_cell() {
let _ = &UNFROZEN_VARIANT; //~ ERROR interior mutability
let _ = &FROZEN_VARIANT;
}
trait AssocConsts {
const TO_BE_UNFROZEN_VARIANT: OptionalCell;
const TO_BE_FROZEN_VARIANT: OptionalCell;
const DEFAULTED_ON_UNFROZEN_VARIANT: OptionalCell = OptionalCell::Unfrozen(Cell::new(false));
const DEFAULTED_ON_FROZEN_VARIANT: OptionalCell = OptionalCell::Frozen;
fn function() {
// This is the "suboptimal behavior" mentioned in `is_value_unfrozen`
// caused by a similar reason to unfrozen types without any default values
// get linted even if it has frozen variants'.
let _ = &Self::TO_BE_FROZEN_VARIANT; //~ ERROR interior mutable
// The lint ignores default values because an impl of this trait can set
// an unfrozen variant to `DEFAULTED_ON_FROZEN_VARIANT` and use the default impl for `function`.
let _ = &Self::DEFAULTED_ON_FROZEN_VARIANT; //~ ERROR interior mutable
}
}
impl AssocConsts for u64 {
const TO_BE_UNFROZEN_VARIANT: OptionalCell = OptionalCell::Unfrozen(Cell::new(false));
const TO_BE_FROZEN_VARIANT: OptionalCell = OptionalCell::Frozen;
fn function() {
let _ = &<Self as AssocConsts>::TO_BE_UNFROZEN_VARIANT; //~ ERROR interior mutable
let _ = &<Self as AssocConsts>::TO_BE_FROZEN_VARIANT;
let _ = &Self::DEFAULTED_ON_UNFROZEN_VARIANT; //~ ERROR interior mutable
let _ = &Self::DEFAULTED_ON_FROZEN_VARIANT;
}
}
trait AssocTypes {
type ToBeUnfrozen;
const TO_BE_UNFROZEN_VARIANT: Option<Self::ToBeUnfrozen>;
const TO_BE_FROZEN_VARIANT: Option<Self::ToBeUnfrozen>;
// there's no need to test here because it's the exactly same as `trait::AssocTypes`
fn function();
}
impl AssocTypes for u64 {
type ToBeUnfrozen = AtomicUsize;
const TO_BE_UNFROZEN_VARIANT: Option<Self::ToBeUnfrozen> = Some(Self::ToBeUnfrozen::new(4)); //~ ERROR interior mutable
const TO_BE_FROZEN_VARIANT: Option<Self::ToBeUnfrozen> = None;
fn function() {
let _ = &<Self as AssocTypes>::TO_BE_UNFROZEN_VARIANT; //~ ERROR interior mutable
let _ = &<Self as AssocTypes>::TO_BE_FROZEN_VARIANT;
}
}
enum BothOfCellAndGeneric<T> {
Unfrozen(Cell<*const T>),
Generic(*const T),
Frozen(usize),
}
impl<T> BothOfCellAndGeneric<T> {
const UNFROZEN_VARIANT: BothOfCellAndGeneric<T> = BothOfCellAndGeneric::Unfrozen(Cell::new(std::ptr::null())); //~ ERROR interior mutable
const GENERIC_VARIANT: BothOfCellAndGeneric<T> = BothOfCellAndGeneric::Generic(std::ptr::null()); //~ ERROR interior mutable
const FROZEN_VARIANT: BothOfCellAndGeneric<T> = BothOfCellAndGeneric::Frozen(5);
fn function() {
let _ = &Self::UNFROZEN_VARIANT; //~ ERROR interior mutability
let _ = &Self::GENERIC_VARIANT; //~ ERROR interior mutability
let _ = &Self::FROZEN_VARIANT;
}
}
fn main() {
// constants defined in foreign crates
let _ = &helper::WRAPPED_PRIVATE_UNFROZEN_VARIANT; //~ ERROR interior mutability
let _ = &helper::WRAPPED_PRIVATE_FROZEN_VARIANT;
}

75
tests/ui/borrow_interior_mutable_const/enums.stderr Normal file
View File

@ -0,0 +1,75 @@
error: a `const` item with interior mutability should not be borrowed
--> $DIR/enums.rs:22:14
|
LL | let _ = &UNFROZEN_VARIANT; //~ ERROR interior mutability
| ^^^^^^^^^^^^^^^^
|
= note: `-D clippy::borrow-interior-mutable-const` implied by `-D warnings`
= help: assign this const to a local or static variable, and use the variable here
error: a `const` item with interior mutability should not be borrowed
--> $DIR/enums.rs:37:18
|
LL | let _ = &Self::TO_BE_FROZEN_VARIANT; //~ ERROR interior mutable
| ^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= help: assign this const to a local or static variable, and use the variable here
error: a `const` item with interior mutability should not be borrowed
--> $DIR/enums.rs:41:18
|
LL | let _ = &Self::DEFAULTED_ON_FROZEN_VARIANT; //~ ERROR interior mutable
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= help: assign this const to a local or static variable, and use the variable here
error: a `const` item with interior mutability should not be borrowed
--> $DIR/enums.rs:50:18
|
LL | let _ = &<Self as AssocConsts>::TO_BE_UNFROZEN_VARIANT; //~ ERROR interior mutable
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= help: assign this const to a local or static variable, and use the variable here
error: a `const` item with interior mutability should not be borrowed
--> $DIR/enums.rs:52:18
|
LL | let _ = &Self::DEFAULTED_ON_UNFROZEN_VARIANT; //~ ERROR interior mutable
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= help: assign this const to a local or static variable, and use the variable here
error: a `const` item with interior mutability should not be borrowed
--> $DIR/enums.rs:74:18
|
LL | let _ = &<Self as AssocTypes>::TO_BE_UNFROZEN_VARIANT; //~ ERROR interior mutable
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= help: assign this const to a local or static variable, and use the variable here
error: a `const` item with interior mutability should not be borrowed
--> $DIR/enums.rs:91:18
|
LL | let _ = &Self::UNFROZEN_VARIANT; //~ ERROR interior mutability
| ^^^^^^^^^^^^^^^^^^^^^^
|
= help: assign this const to a local or static variable, and use the variable here
error: a `const` item with interior mutability should not be borrowed
--> $DIR/enums.rs:92:18
|
LL | let _ = &Self::GENERIC_VARIANT; //~ ERROR interior mutability
| ^^^^^^^^^^^^^^^^^^^^^
|
= help: assign this const to a local or static variable, and use the variable here
error: a `const` item with interior mutability should not be borrowed
--> $DIR/enums.rs:99:14
|
LL | let _ = &helper::WRAPPED_PRIVATE_UNFROZEN_VARIANT; //~ ERROR interior mutability
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= help: assign this const to a local or static variable, and use the variable here
error: aborting due to 9 previous errors

123
tests/ui/declare_interior_mutable_const/enums.rs Normal file
View File

@ -0,0 +1,123 @@
#![warn(clippy::declare_interior_mutable_const)]
use std::cell::Cell;
use std::sync::atomic::AtomicUsize;
enum OptionalCell {
Unfrozen(Cell<bool>),
Frozen,
}
// a constant with enums should be linted only when the used variant is unfrozen (#3962).
const UNFROZEN_VARIANT: OptionalCell = OptionalCell::Unfrozen(Cell::new(true)); //~ ERROR interior mutable
const FROZEN_VARIANT: OptionalCell = OptionalCell::Frozen;
const fn unfrozen_variant() -> OptionalCell {
OptionalCell::Unfrozen(Cell::new(false))
}
const fn frozen_variant() -> OptionalCell {
OptionalCell::Frozen
}
const UNFROZEN_VARIANT_FROM_FN: OptionalCell = unfrozen_variant(); //~ ERROR interior mutable
const FROZEN_VARIANT_FROM_FN: OptionalCell = frozen_variant();
enum NestedInnermost {
Unfrozen(AtomicUsize),
Frozen,
}
struct NestedInner {
inner: NestedInnermost,
}
enum NestedOuter {
NestedInner(NestedInner),
NotNested(usize),
}
struct NestedOutermost {
outer: NestedOuter,
}
// a constant with enums should be linted according to its value, no matter how structs involve.
const NESTED_UNFROZEN_VARIANT: NestedOutermost = NestedOutermost {
outer: NestedOuter::NestedInner(NestedInner {
inner: NestedInnermost::Unfrozen(AtomicUsize::new(2)),
}),
}; //~ ERROR interior mutable
const NESTED_FROZEN_VARIANT: NestedOutermost = NestedOutermost {
outer: NestedOuter::NestedInner(NestedInner {
inner: NestedInnermost::Frozen,
}),
};
trait AssocConsts {
// When there's no default value, lint it only according to its type.
// Further details are on the corresponding code (`NonCopyConst::check_trait_item`).
const TO_BE_UNFROZEN_VARIANT: OptionalCell; //~ ERROR interior mutable
const TO_BE_FROZEN_VARIANT: OptionalCell; //~ ERROR interior mutable
// Lint default values accordingly.
const DEFAULTED_ON_UNFROZEN_VARIANT: OptionalCell = OptionalCell::Unfrozen(Cell::new(false)); //~ ERROR interior mutable
const DEFAULTED_ON_FROZEN_VARIANT: OptionalCell = OptionalCell::Frozen;
}
// The lint doesn't trigger for an assoc constant in a trait impl with an unfrozen type even if it
// has enums. Further details are on the corresponding code in 'NonCopyConst::check_impl_item'.
impl AssocConsts for u64 {
const TO_BE_UNFROZEN_VARIANT: OptionalCell = OptionalCell::Unfrozen(Cell::new(false));
const TO_BE_FROZEN_VARIANT: OptionalCell = OptionalCell::Frozen;
// even if this sets an unfrozen variant, the lint ignores it.
const DEFAULTED_ON_FROZEN_VARIANT: OptionalCell = OptionalCell::Unfrozen(Cell::new(false));
}
// At first, I thought I'd need to check every patterns in `trait.rs`; but, what matters
// here are values; and I think substituted generics at definitions won't appear in MIR.
trait AssocTypes {
type ToBeUnfrozen;
const TO_BE_UNFROZEN_VARIANT: Option<Self::ToBeUnfrozen>;
const TO_BE_FROZEN_VARIANT: Option<Self::ToBeUnfrozen>;
}
impl AssocTypes for u64 {
type ToBeUnfrozen = AtomicUsize;
const TO_BE_UNFROZEN_VARIANT: Option<Self::ToBeUnfrozen> = Some(Self::ToBeUnfrozen::new(4)); //~ ERROR interior mutable
const TO_BE_FROZEN_VARIANT: Option<Self::ToBeUnfrozen> = None;
}
// Use raw pointers since direct generics have a false negative at the type level.
enum BothOfCellAndGeneric<T> {
Unfrozen(Cell<*const T>),
Generic(*const T),
Frozen(usize),
}
impl<T> BothOfCellAndGeneric<T> {
const UNFROZEN_VARIANT: BothOfCellAndGeneric<T> = BothOfCellAndGeneric::Unfrozen(Cell::new(std::ptr::null())); //~ ERROR interior mutable
// This is a false positive. The argument about this is on `is_value_unfrozen_raw`
const GENERIC_VARIANT: BothOfCellAndGeneric<T> = BothOfCellAndGeneric::Generic(std::ptr::null()); //~ ERROR interior mutable
const FROZEN_VARIANT: BothOfCellAndGeneric<T> = BothOfCellAndGeneric::Frozen(5);
// This is what is likely to be a false negative when one tries to fix
// the `GENERIC_VARIANT` false positive.
const NO_ENUM: Cell<*const T> = Cell::new(std::ptr::null()); //~ ERROR interior mutable
}
// associated types here is basically the same as the one above.
trait BothOfCellAndGenericWithAssocType {
type AssocType;
const UNFROZEN_VARIANT: BothOfCellAndGeneric<Self::AssocType> =
BothOfCellAndGeneric::Unfrozen(Cell::new(std::ptr::null())); //~ ERROR interior mutable
const GENERIC_VARIANT: BothOfCellAndGeneric<Self::AssocType> = BothOfCellAndGeneric::Generic(std::ptr::null()); //~ ERROR interior mutable
const FROZEN_VARIANT: BothOfCellAndGeneric<Self::AssocType> = BothOfCellAndGeneric::Frozen(5);
}
fn main() {}

89
tests/ui/declare_interior_mutable_const/enums.stderr Normal file
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@ -0,0 +1,89 @@
error: a `const` item should never be interior mutable
--> $DIR/enums.rs:12:1
|
LL | const UNFROZEN_VARIANT: OptionalCell = OptionalCell::Unfrozen(Cell::new(true)); //~ ERROR interior mutable
| -----^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
| |
| make this a static item (maybe with lazy_static)
|
= note: `-D clippy::declare-interior-mutable-const` implied by `-D warnings`
error: a `const` item should never be interior mutable
--> $DIR/enums.rs:23:1
|
LL | const UNFROZEN_VARIANT_FROM_FN: OptionalCell = unfrozen_variant(); //~ ERROR interior mutable
| -----^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
| |
| make this a static item (maybe with lazy_static)
error: a `const` item should never be interior mutable
--> $DIR/enums.rs:45:1
|
LL | const NESTED_UNFROZEN_VARIANT: NestedOutermost = NestedOutermost {
| ^----
| |
| _make this a static item (maybe with lazy_static)
| |
LL | | outer: NestedOuter::NestedInner(NestedInner {
LL | | inner: NestedInnermost::Unfrozen(AtomicUsize::new(2)),
LL | | }),
LL | | }; //~ ERROR interior mutable
| |__^
error: a `const` item should never be interior mutable
--> $DIR/enums.rs:59:5
|
LL | const TO_BE_UNFROZEN_VARIANT: OptionalCell; //~ ERROR interior mutable
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error: a `const` item should never be interior mutable
--> $DIR/enums.rs:60:5
|
LL | const TO_BE_FROZEN_VARIANT: OptionalCell; //~ ERROR interior mutable
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error: a `const` item should never be interior mutable
--> $DIR/enums.rs:63:5
|
LL | const DEFAULTED_ON_UNFROZEN_VARIANT: OptionalCell = OptionalCell::Unfrozen(Cell::new(false)); //~ ERROR interior mutable
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error: a `const` item should never be interior mutable
--> $DIR/enums.rs:89:5
|
LL | const TO_BE_UNFROZEN_VARIANT: Option<Self::ToBeUnfrozen> = Some(Self::ToBeUnfrozen::new(4)); //~ ERROR interior mutable
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error: a `const` item should never be interior mutable
--> $DIR/enums.rs:101:5
|
LL | const UNFROZEN_VARIANT: BothOfCellAndGeneric<T> = BothOfCellAndGeneric::Unfrozen(Cell::new(std::ptr::null())); //~ ERROR interior mut...
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error: a `const` item should never be interior mutable
--> $DIR/enums.rs:104:5
|
LL | const GENERIC_VARIANT: BothOfCellAndGeneric<T> = BothOfCellAndGeneric::Generic(std::ptr::null()); //~ ERROR interior mutable
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error: a `const` item should never be interior mutable
--> $DIR/enums.rs:110:5
|
LL | const NO_ENUM: Cell<*const T> = Cell::new(std::ptr::null()); //~ ERROR interior mutable
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error: a `const` item should never be interior mutable
--> $DIR/enums.rs:117:5
|
LL | / const UNFROZEN_VARIANT: BothOfCellAndGeneric<Self::AssocType> =
LL | | BothOfCellAndGeneric::Unfrozen(Cell::new(std::ptr::null())); //~ ERROR interior mutable
| |____________________________________________________________________^
error: a `const` item should never be interior mutable
--> $DIR/enums.rs:119:5
|
LL | const GENERIC_VARIANT: BothOfCellAndGeneric<Self::AssocType> = BothOfCellAndGeneric::Generic(std::ptr::null()); //~ ERROR interior mu...
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error: aborting due to 12 previous errors