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Disallow impl autotrait for trait object

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This commit is contained in:
David Tolnay 2023-01-18 22:43:05 -08:00
parent a94b9fd0ac
commit 9e1c600f74
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6 changed files with 269 additions and 70 deletions
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4
compiler/rustc_data_structures/src/sync.rs
View file

@ -31,8 +31,8 @@ cfg_if! {
pub auto trait Send {}
pub auto trait Sync {}
impl<T: ?Sized> Send for T {}
impl<T: ?Sized> Sync for T {}
impl<T> Send for T {}
impl<T> Sync for T {}
#[macro_export]
macro_rules! rustc_erase_owner {

167
compiler/rustc_hir_analysis/src/coherence/orphan.rs
View file

@ -8,7 +8,7 @@ use rustc_hir as hir;
use rustc_middle::ty::subst::InternalSubsts;
use rustc_middle::ty::util::IgnoreRegions;
use rustc_middle::ty::{
self, ImplPolarity, Ty, TyCtxt, TypeSuperVisitable, TypeVisitable, TypeVisitor,
self, AliasKind, ImplPolarity, Ty, TyCtxt, TypeSuperVisitable, TypeVisitable, TypeVisitor,
};
use rustc_session::lint;
use rustc_span::def_id::{DefId, LocalDefId};
@ -86,7 +86,7 @@ fn do_orphan_check_impl<'tcx>(
// struct B { }
// impl Foo for A { }
// impl Foo for B { }
// impl !Send for (A, B) { }
// impl !Foo for (A, B) { }
// ```
//
// This final impl is legal according to the orphan
@ -99,24 +99,148 @@ fn do_orphan_check_impl<'tcx>(
tcx.trait_is_auto(trait_def_id)
);
if tcx.trait_is_auto(trait_def_id) && !trait_def_id.is_local() {
if tcx.trait_is_auto(trait_def_id) {
let self_ty = trait_ref.self_ty();
let opt_self_def_id = match *self_ty.kind() {
ty::Adt(self_def, _) => Some(self_def.did()),
ty::Foreign(did) => Some(did),
_ => None,
// If the impl is in the same crate as the auto-trait, almost anything
// goes.
//
// impl MyAuto for Rc<Something> {} // okay
// impl<T> !MyAuto for *const T {} // okay
// impl<T> MyAuto for T {} // okay
//
// But there is one important exception: implementing for a trait object
// is not allowed.
//
// impl MyAuto for dyn Trait {} // NOT OKAY
// impl<T: ?Sized> MyAuto for T {} // NOT OKAY
//
enum LocalImpl {
Allow,
Disallow { problematic_kind: &'static str },
}
// If the auto-trait is from a dependency, it must only be getting
// implemented for a nominal type, and specifically one local to the
// current crate.
//
// impl<T> Sync for MyStruct<T> {} // okay
//
// impl Sync for Rc<MyStruct> {} // NOT OKAY
enum NonlocalImpl {
Allow,
DisallowBecauseNonlocal,
DisallowOther,
}
// Exhaustive match considering that this logic is essential for
// soundness.
let (local_impl, nonlocal_impl) = match self_ty.kind() {
// struct Struct<T>;
// impl AutoTrait for Struct<Foo> {}
ty::Adt(self_def, _) => (
LocalImpl::Allow,
if self_def.did().is_local() {
NonlocalImpl::Allow
} else {
NonlocalImpl::DisallowBecauseNonlocal
},
),
// extern { type OpaqueType; }
// impl AutoTrait for OpaqueType {}
ty::Foreign(did) => (
LocalImpl::Allow,
if did.is_local() {
NonlocalImpl::Allow
} else {
NonlocalImpl::DisallowBecauseNonlocal
},
),
// impl AutoTrait for dyn Trait {}
ty::Dynamic(..) => (
LocalImpl::Disallow { problematic_kind: "trait object" },
NonlocalImpl::DisallowOther,
),
// impl<T> AutoTrait for T {}
// impl<T: ?Sized> AutoTrait for T {}
ty::Param(..) => (
if self_ty.is_sized(tcx, tcx.param_env(def_id)) {
LocalImpl::Allow
} else {
LocalImpl::Disallow { problematic_kind: "generic type" }
},
NonlocalImpl::DisallowOther,
),
// trait Id { type This: ?Sized; }
// impl<T: ?Sized> Id for T {
// type This = T;
// }
// impl<T: ?Sized> AutoTrait for <T as Id>::This {}
ty::Alias(AliasKind::Projection, _) => (
LocalImpl::Disallow { problematic_kind: "associated type" },
NonlocalImpl::DisallowOther,
),
// type Opaque = impl Trait;
// impl AutoTrait for Opaque {}
ty::Alias(AliasKind::Opaque, _) => (
LocalImpl::Disallow { problematic_kind: "opaque type" },
NonlocalImpl::DisallowOther,
),
ty::Bool
| ty::Char
| ty::Int(..)
| ty::Uint(..)
| ty::Float(..)
| ty::Str
| ty::Array(..)
| ty::Slice(..)
| ty::RawPtr(..)
| ty::Ref(..)
| ty::FnDef(..)
| ty::FnPtr(..)
| ty::Never
| ty::Tuple(..) => (LocalImpl::Allow, NonlocalImpl::DisallowOther),
ty::Closure(..)
| ty::Generator(..)
| ty::GeneratorWitness(..)
| ty::GeneratorWitnessMIR(..)
| ty::Bound(..)
| ty::Placeholder(..)
| ty::Infer(..) => span_bug!(sp, "weird self type for autotrait impl"),
ty::Error(..) => (LocalImpl::Allow, NonlocalImpl::Allow),
};
let msg = match opt_self_def_id {
// We only want to permit nominal types, but not *all* nominal types.
// They must be local to the current crate, so that people
// can't do `unsafe impl Send for Rc<SomethingLocal>` or
// `impl !Send for Box<SomethingLocalAndSend>`.
Some(self_def_id) => {
if self_def_id.is_local() {
None
if trait_def_id.is_local() {
match local_impl {
LocalImpl::Allow => {}
LocalImpl::Disallow { problematic_kind } => {
let msg = format!(
"traits with a default impl, like `{trait}`, \
cannot be implemented for {problematic_kind} `{self_ty}`",
trait = tcx.def_path_str(trait_def_id),
);
let label = format!(
"a trait object implements `{trait}` if and only if `{trait}` \
is one of the trait object's trait bounds",
trait = tcx.def_path_str(trait_def_id),
);
let reported =
struct_span_err!(tcx.sess, sp, E0321, "{}", msg).note(label).emit();
return Err(reported);
}
}
} else {
Some((
if let Some((msg, label)) = match nonlocal_impl {
NonlocalImpl::Allow => None,
NonlocalImpl::DisallowBecauseNonlocal => Some((
format!(
"cross-crate traits with a default impl, like `{}`, \
can only be implemented for a struct/enum type \
@ -124,10 +248,8 @@ fn do_orphan_check_impl<'tcx>(
tcx.def_path_str(trait_def_id)
),
"can't implement cross-crate trait for type in another crate",
))
}
}
_ => Some((
)),
NonlocalImpl::DisallowOther => Some((
format!(
"cross-crate traits with a default impl, like `{}`, can \
only be implemented for a struct/enum type, not `{}`",
@ -137,14 +259,13 @@ fn do_orphan_check_impl<'tcx>(
"can't implement cross-crate trait with a default impl for \
non-struct/enum type",
)),
};
if let Some((msg, label)) = msg {
} {
let reported =
struct_span_err!(tcx.sess, sp, E0321, "{}", msg).span_label(sp, label).emit();
return Err(reported);
}
}
}
Ok(())
}

17
tests/ui/coherence/coherence-impl-trait-for-marker-trait-negative.rs
View file

@ -13,18 +13,25 @@ trait Object: Marker1 {}
// A supertrait marker is illegal...
impl !Marker1 for dyn Object + Marker2 {} //~ ERROR E0371
//~^ ERROR 0321
// ...and also a direct component.
impl !Marker2 for dyn Object + Marker2 {} //~ ERROR E0371
// But implementing a marker if it is not present is OK.
impl !Marker2 for dyn Object {} // OK
//~^ ERROR 0321
// A non-principal trait-object type is orphan even in its crate.
impl !Send for dyn Marker2 {} //~ ERROR E0117
// And impl'ing a remote marker for a local trait object is forbidden
// by one of these special orphan-like rules.
// Implementing a marker for a local trait object is forbidden by a special
// orphan-like rule.
impl !Marker2 for dyn Object {} //~ ERROR E0321
impl !Send for dyn Object {} //~ ERROR E0321
impl !Send for dyn Object + Marker2 {} //~ ERROR E0321
// Blanket impl that applies to dyn Object is equally problematic.
auto trait Marker3 {}
impl<T: ?Sized> !Marker3 for T {} //~ ERROR E0321
auto trait Marker4 {}
impl<T> !Marker4 for T {} // okay
fn main() {}

38
tests/ui/coherence/coherence-impl-trait-for-marker-trait-negative.stderr
View file

@ -4,14 +4,38 @@ error[E0371]: the object type `(dyn Object + Marker2 + 'static)` automatically i
LL | impl !Marker1 for dyn Object + Marker2 {}
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `(dyn Object + Marker2 + 'static)` automatically implements trait `Marker1`
error[E0321]: traits with a default impl, like `Marker1`, cannot be implemented for trait object `(dyn Object + Marker2 + 'static)`
--> $DIR/coherence-impl-trait-for-marker-trait-negative.rs:15:1
|
LL | impl !Marker1 for dyn Object + Marker2 {}
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= note: a trait object implements `Marker1` if and only if `Marker1` is one of the trait object's trait bounds
error[E0371]: the object type `(dyn Object + Marker2 + 'static)` automatically implements the trait `Marker2`
--> $DIR/coherence-impl-trait-for-marker-trait-negative.rs:17:1
--> $DIR/coherence-impl-trait-for-marker-trait-negative.rs:18:1
|
LL | impl !Marker2 for dyn Object + Marker2 {}
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `(dyn Object + Marker2 + 'static)` automatically implements trait `Marker2`
error[E0321]: traits with a default impl, like `Marker2`, cannot be implemented for trait object `(dyn Object + Marker2 + 'static)`
--> $DIR/coherence-impl-trait-for-marker-trait-negative.rs:18:1
|
LL | impl !Marker2 for dyn Object + Marker2 {}
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= note: a trait object implements `Marker2` if and only if `Marker2` is one of the trait object's trait bounds
error[E0321]: traits with a default impl, like `Marker2`, cannot be implemented for trait object `(dyn Object + 'static)`
--> $DIR/coherence-impl-trait-for-marker-trait-negative.rs:26:1
|
LL | impl !Marker2 for dyn Object {}
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= note: a trait object implements `Marker2` if and only if `Marker2` is one of the trait object's trait bounds
error[E0117]: only traits defined in the current crate can be implemented for arbitrary types
--> $DIR/coherence-impl-trait-for-marker-trait-negative.rs:23:1
--> $DIR/coherence-impl-trait-for-marker-trait-negative.rs:22:1
|
LL | impl !Send for dyn Marker2 {}
| ^^^^^^^^^^^^^^^-----------
@ -33,7 +57,15 @@ error[E0321]: cross-crate traits with a default impl, like `Send`, can only be i
LL | impl !Send for dyn Object + Marker2 {}
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ can't implement cross-crate trait with a default impl for non-struct/enum type
error: aborting due to 5 previous errors
error[E0321]: traits with a default impl, like `Marker3`, cannot be implemented for generic type `T`
--> $DIR/coherence-impl-trait-for-marker-trait-negative.rs:32:1
|
LL | impl<T: ?Sized> !Marker3 for T {}
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= note: a trait object implements `Marker3` if and only if `Marker3` is one of the trait object's trait bounds
error: aborting due to 9 previous errors
Some errors have detailed explanations: E0117, E0321, E0371.
For more information about an error, try `rustc --explain E0117`.

17
tests/ui/coherence/coherence-impl-trait-for-marker-trait-positive.rs
View file

@ -13,18 +13,25 @@ trait Object: Marker1 {}
// A supertrait marker is illegal...
impl Marker1 for dyn Object + Marker2 {} //~ ERROR E0371
//~^ ERROR E0321
// ...and also a direct component.
impl Marker2 for dyn Object + Marker2 {} //~ ERROR E0371
// But implementing a marker if it is not present is OK.
impl Marker2 for dyn Object {} // OK
//~^ ERROR E0321
// A non-principal trait-object type is orphan even in its crate.
unsafe impl Send for dyn Marker2 {} //~ ERROR E0117
// And impl'ing a remote marker for a local trait object is forbidden
// by one of these special orphan-like rules.
// Implementing a marker for a local trait object is forbidden by a special
// orphan-like rule.
impl Marker2 for dyn Object {} //~ ERROR E0321
unsafe impl Send for dyn Object {} //~ ERROR E0321
unsafe impl Send for dyn Object + Marker2 {} //~ ERROR E0321
// Blanket impl that applies to dyn Object is equally problematic.
auto trait Marker3 {}
impl<T: ?Sized> Marker3 for T {} //~ ERROR E0321
auto trait Marker4 {}
impl<T> Marker4 for T {} // okay
fn main() {}

38
tests/ui/coherence/coherence-impl-trait-for-marker-trait-positive.stderr
View file

@ -4,14 +4,38 @@ error[E0371]: the object type `(dyn Object + Marker2 + 'static)` automatically i
LL | impl Marker1 for dyn Object + Marker2 {}
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `(dyn Object + Marker2 + 'static)` automatically implements trait `Marker1`
error[E0321]: traits with a default impl, like `Marker1`, cannot be implemented for trait object `(dyn Object + Marker2 + 'static)`
--> $DIR/coherence-impl-trait-for-marker-trait-positive.rs:15:1
|
LL | impl Marker1 for dyn Object + Marker2 {}
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= note: a trait object implements `Marker1` if and only if `Marker1` is one of the trait object's trait bounds
error[E0371]: the object type `(dyn Object + Marker2 + 'static)` automatically implements the trait `Marker2`
--> $DIR/coherence-impl-trait-for-marker-trait-positive.rs:17:1
--> $DIR/coherence-impl-trait-for-marker-trait-positive.rs:18:1
|
LL | impl Marker2 for dyn Object + Marker2 {}
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `(dyn Object + Marker2 + 'static)` automatically implements trait `Marker2`
error[E0321]: traits with a default impl, like `Marker2`, cannot be implemented for trait object `(dyn Object + Marker2 + 'static)`
--> $DIR/coherence-impl-trait-for-marker-trait-positive.rs:18:1
|
LL | impl Marker2 for dyn Object + Marker2 {}
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= note: a trait object implements `Marker2` if and only if `Marker2` is one of the trait object's trait bounds
error[E0321]: traits with a default impl, like `Marker2`, cannot be implemented for trait object `(dyn Object + 'static)`
--> $DIR/coherence-impl-trait-for-marker-trait-positive.rs:26:1
|
LL | impl Marker2 for dyn Object {}
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= note: a trait object implements `Marker2` if and only if `Marker2` is one of the trait object's trait bounds
error[E0117]: only traits defined in the current crate can be implemented for arbitrary types
--> $DIR/coherence-impl-trait-for-marker-trait-positive.rs:23:1
--> $DIR/coherence-impl-trait-for-marker-trait-positive.rs:22:1
|
LL | unsafe impl Send for dyn Marker2 {}
| ^^^^^^^^^^^^^^^^^^^^^-----------
@ -33,7 +57,15 @@ error[E0321]: cross-crate traits with a default impl, like `Send`, can only be i
LL | unsafe impl Send for dyn Object + Marker2 {}
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ can't implement cross-crate trait with a default impl for non-struct/enum type
error: aborting due to 5 previous errors
error[E0321]: traits with a default impl, like `Marker3`, cannot be implemented for generic type `T`
--> $DIR/coherence-impl-trait-for-marker-trait-positive.rs:32:1
|
LL | impl<T: ?Sized> Marker3 for T {}
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= note: a trait object implements `Marker3` if and only if `Marker3` is one of the trait object's trait bounds
error: aborting due to 9 previous errors
Some errors have detailed explanations: E0117, E0321, E0371.
For more information about an error, try `rustc --explain E0117`.