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Require Drop impls to have the same constness on its bounds as the bounds on the struct have #103351

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Merged
merged 2 commits into from
Oct 22, 2022
Merged

Require Drop impls to have the same constness on its bounds as the bounds on the struct have #103351

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349ba6b
Remove needless special cases and dead code
oli-obk Oct 21, 2022
d6cf893
Require Drop impls to have the same constness on its bounds as the bo…
oli-obk Oct 21, 2022
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52 changes: 3 additions & 49 deletions compiler/rustc_ast_passes/src/ast_validation.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -251,20 +251,6 @@ impl<'a> AstValidator<'a> {
}
}

fn visit_struct_field_def(&mut self, field: &'a FieldDef) {
if let Some(ident) = field.ident {
if ident.name == kw::Underscore {
self.visit_vis(&field.vis);
self.visit_ident(ident);
self.visit_ty_common(&field.ty);
self.walk_ty(&field.ty);
walk_list!(self, visit_attribute, &field.attrs);
return;
}
}
self.visit_field_def(field);
}

fn err_handler(&self) -> &rustc_errors::Handler {
&self.session.diagnostic()
}
Expand Down Expand Up @@ -1005,8 +991,8 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
visit::walk_lifetime(self, lifetime);
}

fn visit_field_def(&mut self, s: &'a FieldDef) {
visit::walk_field_def(self, s)
fn visit_field_def(&mut self, field: &'a FieldDef) {
visit::walk_field_def(self, field)
}

fn visit_item(&mut self, item: &'a Item) {
Expand Down Expand Up @@ -1194,42 +1180,10 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
self.check_mod_file_item_asciionly(item.ident);
}
}
ItemKind::Struct(ref vdata, ref generics) => match vdata {
// Duplicating the `Visitor` logic allows catching all cases
// of `Anonymous(Struct, Union)` outside of a field struct or union.
//
// Inside `visit_ty` the validator catches every `Anonymous(Struct, Union)` it
// encounters, and only on `ItemKind::Struct` and `ItemKind::Union`
// it uses `visit_ty_common`, which doesn't contain that specific check.
VariantData::Struct(ref fields, ..) => {
self.visit_vis(&item.vis);
self.visit_ident(item.ident);
self.visit_generics(generics);
self.with_banned_assoc_ty_bound(|this| {
walk_list!(this, visit_struct_field_def, fields);
});
walk_list!(self, visit_attribute, &item.attrs);
return;
}
_ => {}
},
ItemKind::Union(ref vdata, ref generics) => {
ItemKind::Union(ref vdata, ..) => {
if vdata.fields().is_empty() {
self.err_handler().span_err(item.span, "unions cannot have zero fields");
}
match vdata {
VariantData::Struct(ref fields, ..) => {
self.visit_vis(&item.vis);
self.visit_ident(item.ident);
self.visit_generics(generics);
self.with_banned_assoc_ty_bound(|this| {
walk_list!(this, visit_struct_field_def, fields);
});
walk_list!(self, visit_attribute, &item.attrs);
return;
}
_ => {}
}
}
ItemKind::Const(def, .., None) => {
self.check_defaultness(item.span, def);
Expand Down
8 changes: 1 addition & 7 deletions compiler/rustc_hir_analysis/src/check/dropck.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -184,13 +184,7 @@ fn ensure_drop_predicates_are_implied_by_item_defn<'tcx>(
let p = p.kind();
match (predicate.skip_binder(), p.skip_binder()) {
(ty::PredicateKind::Trait(a), ty::PredicateKind::Trait(b)) => {
// Since struct predicates cannot have ~const, project the impl predicate
// onto one that ignores the constness. This is equivalent to saying that
// we match a `Trait` bound on the struct with a `Trait` or `~const Trait`
// in the impl.
let non_const_a =
ty::TraitPredicate { constness: ty::BoundConstness::NotConst, ..a };
relator.relate(predicate.rebind(non_const_a), p.rebind(b)).is_ok()
relator.relate(predicate.rebind(a), p.rebind(b)).is_ok()
}
(ty::PredicateKind::Projection(a), ty::PredicateKind::Projection(b)) => {
relator.relate(predicate.rebind(a), p.rebind(b)).is_ok()
Expand Down
65 changes: 43 additions & 22 deletions src/test/ui/rfc-2632-const-trait-impl/const-drop-fail.precise.stderr
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Original file line number Diff line number Diff line change
Expand Up @@ -45,34 +45,55 @@ note: required by a bound in `check`
LL | const fn check<T: ~const Destruct>(_: T) {}
| ^^^^^^^^^^^^^^^ required by this bound in `check`

error[E0277]: the trait bound `ConstDropImplWithBounds<NonTrivialDrop>: ~const Destruct` is not satisfied
error[E0277]: the trait bound `NonTrivialDrop: ~const A` is not satisfied
--> $DIR/const-drop-fail.rs:48:47
|
LL | ConstDropImplWithBounds::<NonTrivialDrop>(PhantomData),
| ----------------------------------------- ^^^^^^^^^^^ the trait `~const A` is not implemented for `NonTrivialDrop`
| |
| required by a bound introduced by this call
|
note: the trait `A` is implemented for `NonTrivialDrop`, but that implementation is not `const`
--> $DIR/const-drop-fail.rs:48:47
|
LL | ConstDropImplWithBounds::<NonTrivialDrop>(PhantomData),
| ^^^^^^^^^^^
note: required by a bound in `ConstDropImplWithBounds`
--> $DIR/const-drop-fail.rs:27:35
|
LL | struct ConstDropImplWithBounds<T: ~const A>(PhantomData<T>);
| ^^^^^^^^ required by this bound in `ConstDropImplWithBounds`

error[E0277]: the trait bound `NonTrivialDrop: ~const A` is not satisfied
--> $DIR/const-drop-fail.rs:48:5
|
LL | ConstDropImplWithBounds::<NonTrivialDrop>(PhantomData),
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `~const A` is not implemented for `NonTrivialDrop`
|
note: the trait `A` is implemented for `NonTrivialDrop`, but that implementation is not `const`
--> $DIR/const-drop-fail.rs:48:5
|
LL | const _: () = check($exp);
| ----- required by a bound introduced by this call
...
LL | ConstDropImplWithBounds::<NonTrivialDrop>(PhantomData),
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `~const Destruct` is not implemented for `ConstDropImplWithBounds<NonTrivialDrop>`
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
note: required by a bound in `ConstDropImplWithBounds`
--> $DIR/const-drop-fail.rs:27:35
|
note: required for `ConstDropImplWithBounds<NonTrivialDrop>` to implement `~const Destruct`
--> $DIR/const-drop-fail.rs:29:25
LL | struct ConstDropImplWithBounds<T: ~const A>(PhantomData<T>);
| ^^^^^^^^ required by this bound in `ConstDropImplWithBounds`

error[E0367]: `Drop` impl requires `T: ~const A` but the struct it is implemented for does not
--> $DIR/const-drop-fail.rs:55:9
|
LL | impl<T: ~const A> const Drop for ConstDropImplWithBounds<T> {
| ^^^^ ^^^^^^^^^^^^^^^^^^^^^^^^^^
= note: 1 redundant requirement hidden
= note: required for `ConstDropImplWithBounds<NonTrivialDrop>` to implement `~const Destruct`
note: required by a bound in `check`
--> $DIR/const-drop-fail.rs:35:19
LL | impl<T: ~const A> const Drop for ConstDropImplWithNonConstBounds<T> {
| ^^^^^^^^
|
LL | const fn check<T: ~const Destruct>(_: T) {}
| ^^^^^^^^^^^^^^^ required by this bound in `check`
help: consider borrowing here
note: the implementor must specify the same requirement
--> $DIR/const-drop-fail.rs:53:1
|
LL | &ConstDropImplWithBounds::<NonTrivialDrop>(PhantomData),
| +
LL | &mut ConstDropImplWithBounds::<NonTrivialDrop>(PhantomData),
| ++++
LL | struct ConstDropImplWithNonConstBounds<T: A>(PhantomData<T>);
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error: aborting due to 3 previous errors
error: aborting due to 5 previous errors

For more information about this error, try `rustc --explain E0277`.
Some errors have detailed explanations: E0277, E0367.
For more information about an error, try `rustc --explain E0277`.
12 changes: 11 additions & 1 deletion src/test/ui/rfc-2632-const-trait-impl/const-drop-fail.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -24,7 +24,7 @@ trait A { fn a() { } }

impl A for NonTrivialDrop {}

struct ConstDropImplWithBounds<T: A>(PhantomData<T>);
struct ConstDropImplWithBounds<T: ~const A>(PhantomData<T>);

impl<T: ~const A> const Drop for ConstDropImplWithBounds<T> {
fn drop(&mut self) {
Expand All @@ -47,6 +47,16 @@ check_all! {
//~^ ERROR can't drop
ConstDropImplWithBounds::<NonTrivialDrop>(PhantomData),
//~^ ERROR the trait bound
//~| ERROR the trait bound
}

struct ConstDropImplWithNonConstBounds<T: A>(PhantomData<T>);

impl<T: ~const A> const Drop for ConstDropImplWithNonConstBounds<T> {
//~^ ERROR `Drop` impl requires `T: ~const A` but the struct it is implemented for does not
fn drop(&mut self) {
T::a();
}
}

fn main() {}
65 changes: 43 additions & 22 deletions src/test/ui/rfc-2632-const-trait-impl/const-drop-fail.stock.stderr
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Original file line number Diff line number Diff line change
Expand Up @@ -45,34 +45,55 @@ note: required by a bound in `check`
LL | const fn check<T: ~const Destruct>(_: T) {}
| ^^^^^^^^^^^^^^^ required by this bound in `check`

error[E0277]: the trait bound `ConstDropImplWithBounds<NonTrivialDrop>: ~const Destruct` is not satisfied
error[E0277]: the trait bound `NonTrivialDrop: ~const A` is not satisfied
--> $DIR/const-drop-fail.rs:48:47
|
LL | ConstDropImplWithBounds::<NonTrivialDrop>(PhantomData),
| ----------------------------------------- ^^^^^^^^^^^ the trait `~const A` is not implemented for `NonTrivialDrop`
| |
| required by a bound introduced by this call
|
note: the trait `A` is implemented for `NonTrivialDrop`, but that implementation is not `const`
--> $DIR/const-drop-fail.rs:48:47
|
LL | ConstDropImplWithBounds::<NonTrivialDrop>(PhantomData),
| ^^^^^^^^^^^
note: required by a bound in `ConstDropImplWithBounds`
--> $DIR/const-drop-fail.rs:27:35
|
LL | struct ConstDropImplWithBounds<T: ~const A>(PhantomData<T>);
| ^^^^^^^^ required by this bound in `ConstDropImplWithBounds`

error[E0277]: the trait bound `NonTrivialDrop: ~const A` is not satisfied
--> $DIR/const-drop-fail.rs:48:5
|
LL | ConstDropImplWithBounds::<NonTrivialDrop>(PhantomData),
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `~const A` is not implemented for `NonTrivialDrop`
|
note: the trait `A` is implemented for `NonTrivialDrop`, but that implementation is not `const`
--> $DIR/const-drop-fail.rs:48:5
|
LL | const _: () = check($exp);
| ----- required by a bound introduced by this call
...
LL | ConstDropImplWithBounds::<NonTrivialDrop>(PhantomData),
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `~const Destruct` is not implemented for `ConstDropImplWithBounds<NonTrivialDrop>`
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
note: required by a bound in `ConstDropImplWithBounds`
--> $DIR/const-drop-fail.rs:27:35
|
note: required for `ConstDropImplWithBounds<NonTrivialDrop>` to implement `~const Destruct`
--> $DIR/const-drop-fail.rs:29:25
LL | struct ConstDropImplWithBounds<T: ~const A>(PhantomData<T>);
| ^^^^^^^^ required by this bound in `ConstDropImplWithBounds`

error[E0367]: `Drop` impl requires `T: ~const A` but the struct it is implemented for does not
--> $DIR/const-drop-fail.rs:55:9
|
LL | impl<T: ~const A> const Drop for ConstDropImplWithBounds<T> {
| ^^^^ ^^^^^^^^^^^^^^^^^^^^^^^^^^
= note: 1 redundant requirement hidden
= note: required for `ConstDropImplWithBounds<NonTrivialDrop>` to implement `~const Destruct`
note: required by a bound in `check`
--> $DIR/const-drop-fail.rs:35:19
LL | impl<T: ~const A> const Drop for ConstDropImplWithNonConstBounds<T> {
| ^^^^^^^^
|
LL | const fn check<T: ~const Destruct>(_: T) {}
| ^^^^^^^^^^^^^^^ required by this bound in `check`
help: consider borrowing here
note: the implementor must specify the same requirement
--> $DIR/const-drop-fail.rs:53:1
|
LL | &ConstDropImplWithBounds::<NonTrivialDrop>(PhantomData),
| +
LL | &mut ConstDropImplWithBounds::<NonTrivialDrop>(PhantomData),
| ++++
LL | struct ConstDropImplWithNonConstBounds<T: A>(PhantomData<T>);
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error: aborting due to 3 previous errors
error: aborting due to 5 previous errors

For more information about this error, try `rustc --explain E0277`.
Some errors have detailed explanations: E0277, E0367.
For more information about an error, try `rustc --explain E0277`.
2 changes: 1 addition & 1 deletion src/test/ui/rfc-2632-const-trait-impl/const-drop.rs
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Expand Up @@ -60,7 +60,7 @@ mod t {
fn foo() {}
}

pub struct ConstDropWithBound<T: SomeTrait>(pub core::marker::PhantomData<T>);
pub struct ConstDropWithBound<T: ~const SomeTrait>(pub core::marker::PhantomData<T>);

impl<T: ~const SomeTrait> const Drop for ConstDropWithBound<T> {
fn drop(&mut self) {
Expand Down
17 changes: 17 additions & 0 deletions src/test/ui/rfc-2632-const-trait-impl/tilde_const_on_impl_bound.rs
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@@ -0,0 +1,17 @@
// check-pass
#![feature(const_trait_impl)]

#[const_trait]
trait Foo {
fn foo(&self) {}
}

struct Bar<T>(T);

impl<T: ~const Foo> Bar<T> {
const fn foo(&self) {
self.0.foo()
}
}

fn main() {}