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Point at reason in object unsafe trait with Self in supertraits or where-clause

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This commit is contained in:
Esteban Küber 2020-02-02 12:51:30 -08:00
parent 16d935e725
commit 865216b3ad
8 changed files with 78 additions and 30 deletions
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54
src/librustc/traits/object_safety.rs
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@ -32,7 +32,7 @@ pub enum ObjectSafetyViolation {
/// Supertrait reference references `Self` an in illegal location
/// (e.g., `trait Foo : Bar<Self>`).
SupertraitSelf,
SupertraitSelf(SmallVec<[Span; 1]>),
/// Method has something illegal.
Method(ast::Name, MethodViolationCode, Span),
@ -45,9 +45,13 @@ impl ObjectSafetyViolation {
pub fn error_msg(&self) -> Cow<'static, str> {
match *self {
ObjectSafetyViolation::SizedSelf(_) => "it requires `Self: Sized`".into(),
ObjectSafetyViolation::SupertraitSelf => {
"it cannot use `Self` as a type parameter in the supertraits or `where`-clauses"
.into()
ObjectSafetyViolation::SupertraitSelf(ref spans) => {
if spans.iter().any(|sp| *sp != DUMMY_SP) {
"it uses `Self` as a type parameter in this".into()
} else {
"it cannot use `Self` as a type parameter in a supertrait or `where`-clause"
.into()
}
}
ObjectSafetyViolation::Method(name, MethodViolationCode::StaticMethod(_), _) => {
format!("associated function `{}` has no `self` parameter", name).into()
@ -87,7 +91,7 @@ pub fn error_msg(&self) -> Cow<'static, str> {
pub fn solution(&self) -> Option<(String, Option<(String, Span)>)> {
Some(match *self {
ObjectSafetyViolation::SizedSelf(_) | ObjectSafetyViolation::SupertraitSelf => {
ObjectSafetyViolation::SizedSelf(_) | ObjectSafetyViolation::SupertraitSelf(_) => {
return None;
}
ObjectSafetyViolation::Method(name, MethodViolationCode::StaticMethod(sugg), _) => (
@ -118,7 +122,8 @@ pub fn solution(&self) -> Option<(String, Option<(String, Span)>)> {
// When `span` comes from a separate crate, it'll be `DUMMY_SP`. Treat it as `None` so
// diagnostics use a `note` instead of a `span_label`.
match self {
ObjectSafetyViolation::SizedSelf(spans) => spans.clone(),
ObjectSafetyViolation::SupertraitSelf(spans)
| ObjectSafetyViolation::SizedSelf(spans) => spans.clone(),
ObjectSafetyViolation::AssocConst(_, span)
| ObjectSafetyViolation::Method(_, _, span)
if *span != DUMMY_SP =>
@ -162,8 +167,9 @@ pub fn astconv_object_safety_violations(
) -> Vec<ObjectSafetyViolation> {
debug_assert!(tcx.generics_of(trait_def_id).has_self);
let violations = traits::supertrait_def_ids(tcx, trait_def_id)
.filter(|&def_id| predicates_reference_self(tcx, def_id, true))
.map(|_| ObjectSafetyViolation::SupertraitSelf)
.map(|def_id| predicates_reference_self(tcx, def_id, true))
.filter(|spans| !spans.is_empty())
.map(|spans| ObjectSafetyViolation::SupertraitSelf(spans))
.collect();
debug!("astconv_object_safety_violations(trait_def_id={:?}) = {:?}", trait_def_id, violations);
@ -266,8 +272,9 @@ fn object_safety_violations_for_trait(
let spans = get_sized_bounds(tcx, trait_def_id);
violations.push(ObjectSafetyViolation::SizedSelf(spans));
}
if predicates_reference_self(tcx, trait_def_id, false) {
violations.push(ObjectSafetyViolation::SupertraitSelf);
let spans = predicates_reference_self(tcx, trait_def_id, false);
if !spans.is_empty() {
violations.push(ObjectSafetyViolation::SupertraitSelf(spans));
}
violations.extend(
@ -337,7 +344,11 @@ fn object_safety_violations_for_trait(
.unwrap_or_else(SmallVec::new)
}
fn predicates_reference_self(tcx: TyCtxt<'_>, trait_def_id: DefId, supertraits_only: bool) -> bool {
fn predicates_reference_self(
tcx: TyCtxt<'_>,
trait_def_id: DefId,
supertraits_only: bool,
) -> SmallVec<[Span; 1]> {
let trait_ref = ty::Binder::dummy(ty::TraitRef::identity(tcx, trait_def_id));
let predicates = if supertraits_only {
tcx.super_predicates_of(trait_def_id)
@ -349,12 +360,16 @@ fn predicates_reference_self(tcx: TyCtxt<'_>, trait_def_id: DefId, supertraits_o
predicates
.predicates
.iter()
.map(|(predicate, _)| predicate.subst_supertrait(tcx, &trait_ref))
.any(|predicate| {
.map(|(predicate, sp)| (predicate.subst_supertrait(tcx, &trait_ref), sp))
.filter_map(|(predicate, &sp)| {
match predicate {
ty::Predicate::Trait(ref data, _) => {
// In the case of a trait predicate, we can skip the "self" type.
data.skip_binder().input_types().skip(1).any(has_self_ty)
if data.skip_binder().input_types().skip(1).any(has_self_ty) {
Some(sp)
} else {
None
}
}
ty::Predicate::Projection(ref data) => {
// And similarly for projections. This should be redundant with
@ -369,12 +384,18 @@ fn predicates_reference_self(tcx: TyCtxt<'_>, trait_def_id: DefId, supertraits_o
//
// This is ALT2 in issue #56288, see that for discussion of the
// possible alternatives.
data.skip_binder()
if data
.skip_binder()
.projection_ty
.trait_ref(tcx)
.input_types()
.skip(1)
.any(has_self_ty)
{
Some(sp)
} else {
None
}
}
ty::Predicate::WellFormed(..)
| ty::Predicate::ObjectSafe(..)
@ -382,9 +403,10 @@ fn predicates_reference_self(tcx: TyCtxt<'_>, trait_def_id: DefId, supertraits_o
| ty::Predicate::RegionOutlives(..)
| ty::Predicate::ClosureKind(..)
| ty::Predicate::Subtype(..)
| ty::Predicate::ConstEvaluatable(..) => false,
| ty::Predicate::ConstEvaluatable(..) => None,
}
})
.collect()
}
fn trait_has_sized_self(tcx: TyCtxt<'_>, trait_def_id: DefId) -> bool {

7
src/test/ui/issues/issue-26056.stderr
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@ -1,10 +1,13 @@
error[E0038]: the trait `Map` cannot be made into an object
--> $DIR/issue-26056.rs:20:13
|
LL | trait Map: MapLookup<<Self as Map>::Key> {
| --- ----------------------------- ...because it uses `Self` as a type parameter in this
| |
| this trait cannot be made into an object...
...
LL | as &dyn Map<Key=u32,MapValue=u32>;
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `Map` cannot be made into an object
|
= note: the trait cannot be made into an object because it cannot use `Self` as a type parameter in the supertraits or `where`-clauses
error: aborting due to previous error

9
src/test/ui/issues/issue-28576.stderr
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@ -1,11 +1,16 @@
error[E0038]: the trait `Bar` cannot be made into an object
--> $DIR/issue-28576.rs:7:12
|
LL | pub trait Bar: Foo<Assoc=()> {
| --- -------------
| | | |
| | | ...because it uses `Self` as a type parameter in this
| | ...because it uses `Self` as a type parameter in this
| this trait cannot be made into an object...
LL | fn new(&self, b: &
LL | / dyn Bar
LL | | <Assoc=()>
| |________________________^ the trait `Bar` cannot be made into an object
|
= note: the trait cannot be made into an object because it cannot use `Self` as a type parameter in the supertraits or `where`-clauses
error: aborting due to previous error

6
src/test/ui/issues/issue-38404.stderr
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@ -1,10 +1,12 @@
error[E0038]: the trait `B` cannot be made into an object
--> $DIR/issue-38404.rs:3:15
|
LL | trait A<T>: std::ops::Add<Self> + Sized {}
| ------------------- ...because it uses `Self` as a type parameter in this
LL | trait B<T>: A<T> {}
| - this trait cannot be made into an object...
LL | trait C<T>: A<dyn B<T, Output=usize>> {}
| ^^^^^^^^^^^^^^^^^^^^^^ the trait `B` cannot be made into an object
|
= note: the trait cannot be made into an object because it cannot use `Self` as a type parameter in the supertraits or `where`-clauses
error: aborting due to previous error

13
src/test/ui/issues/issue-38604.stderr
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@ -1,18 +1,25 @@
error[E0038]: the trait `Foo` cannot be made into an object
--> $DIR/issue-38604.rs:14:13
|
LL | trait Foo where u32: Q<Self> {
| --- ------- ...because it uses `Self` as a type parameter in this
| |
| this trait cannot be made into an object...
...
LL | let _f: Box<dyn Foo> =
| ^^^^^^^^^^^^ the trait `Foo` cannot be made into an object
|
= note: the trait cannot be made into an object because it cannot use `Self` as a type parameter in the supertraits or `where`-clauses
error[E0038]: the trait `Foo` cannot be made into an object
--> $DIR/issue-38604.rs:15:9
|
LL | trait Foo where u32: Q<Self> {
| --- ------- ...because it uses `Self` as a type parameter in this
| |
| this trait cannot be made into an object...
...
LL | Box::new(());
| ^^^^^^^^^^^^ the trait `Foo` cannot be made into an object
|
= note: the trait cannot be made into an object because it cannot use `Self` as a type parameter in the supertraits or `where`-clauses
= note: required because of the requirements on the impl of `std::ops::CoerceUnsized<std::boxed::Box<dyn Foo>>` for `std::boxed::Box<()>`
= note: required by cast to type `std::boxed::Box<dyn Foo>`

7
src/test/ui/object-safety/object-safety-issue-22040.stderr
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@ -1,10 +1,13 @@
error[E0038]: the trait `Expr` cannot be made into an object
--> $DIR/object-safety-issue-22040.rs:12:23
|
LL | trait Expr: Debug + PartialEq {
| ---- --------- ...because it uses `Self` as a type parameter in this
| |
| this trait cannot be made into an object...
...
LL | elements: Vec<Box<dyn Expr + 'x>>,
| ^^^^^^^^^^^^^ the trait `Expr` cannot be made into an object
|
= note: the trait cannot be made into an object because it cannot use `Self` as a type parameter in the supertraits or `where`-clauses
error: aborting due to previous error

7
src/test/ui/object-safety/object-safety-supertrait-mentions-Self.stderr
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@ -1,10 +1,13 @@
error[E0038]: the trait `Baz` cannot be made into an object
--> $DIR/object-safety-supertrait-mentions-Self.rs:15:31
|
LL | trait Baz : Bar<Self> {
| --- --------- ...because it uses `Self` as a type parameter in this
| |
| this trait cannot be made into an object...
...
LL | fn make_baz<T:Baz>(t: &T) -> &dyn Baz {
| ^^^^^^^ the trait `Baz` cannot be made into an object
|
= note: the trait cannot be made into an object because it cannot use `Self` as a type parameter in the supertraits or `where`-clauses
error: aborting due to previous error

5
src/test/ui/traits/trait-alias/trait-alias-object-fail.stderr
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@ -3,8 +3,11 @@ error[E0038]: the trait `std::cmp::Eq` cannot be made into an object
|
LL | let _: &dyn EqAlias = &123;
| ^^^^^^^^^^^ the trait `std::cmp::Eq` cannot be made into an object
|
::: $SRC_DIR/libcore/cmp.rs:LL:COL
|
= note: the trait cannot be made into an object because it cannot use `Self` as a type parameter in the supertraits or `where`-clauses
LL | pub trait Eq: PartialEq<Self> {
| --------------- the trait cannot be made into an object because it uses `Self` as a type parameter in this
error[E0191]: the value of the associated type `Item` (from trait `std::iter::Iterator`) must be specified
--> $DIR/trait-alias-object-fail.rs:9:17