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Allow constraining opaque types during subtyping in the trait system

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This commit is contained in:
Oli Scherer 2024-05-27 11:49:05 +00:00
parent 9889a6f5d3
commit ba4510ece8
5 changed files with 37 additions and 87 deletions
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4
compiler/rustc_infer/src/infer/mod.rs
View File

@ -878,9 +878,9 @@ pub fn subtype_predicate(
self.enter_forall(predicate, |ty::SubtypePredicate { a_is_expected, a, b }| {
if a_is_expected {
Ok(self.at(cause, param_env).sub(DefineOpaqueTypes::No, a, b))
Ok(self.at(cause, param_env).sub(DefineOpaqueTypes::Yes, a, b))
} else {
Ok(self.at(cause, param_env).sup(DefineOpaqueTypes::No, b, a))
Ok(self.at(cause, param_env).sup(DefineOpaqueTypes::Yes, b, a))
}
})
}

63
tests/ui/impl-trait/lazy_subtyping_of_opaques.rs
View File

@ -2,58 +2,23 @@
//! No hidden types are being constrained in the subtyping predicate, but type and
//! lifetime variables get subtyped in the generic parameter list of the opaque.
use std::iter;
//@ check-pass
mod either {
pub enum Either<L, R> {
Left(L),
Right(R),
}
fn foo() -> impl Default + Copy {
if false {
let x = Default::default();
// add `Subtype(?x, ?y)` obligation
let y = x;
impl<L: Iterator, R: Iterator<Item = L::Item>> Iterator for Either<L, R> {
type Item = L::Item;
fn next(&mut self) -> Option<Self::Item> {
todo!()
}
}
pub use self::Either::{Left, Right};
}
pub enum BabeConsensusLogRef<'a> {
NextEpochData(BabeNextEpochRef<'a>),
NextConfigData,
}
impl<'a> BabeConsensusLogRef<'a> {
pub fn scale_encoding(
&self,
) -> impl Iterator<Item = impl AsRef<[u8]> + Clone + 'a> + Clone + 'a {
//~^ ERROR is not satisfied
//~| ERROR is not satisfied
//~| ERROR is not satisfied
match self {
BabeConsensusLogRef::NextEpochData(digest) => either::Left(either::Left(
digest.scale_encoding().map(either::Left).map(either::Left),
)),
BabeConsensusLogRef::NextConfigData => either::Right(
// The Opaque type from ``scale_encoding` gets used opaquely here, while the `R`
// generic parameter of `Either` contains type variables that get subtyped and the
// opaque type contains lifetime variables that get subtyped.
iter::once(either::Right(either::Left([1])))
.chain(std::iter::once([1]).map(either::Right).map(either::Right)),
),
}
}
}
pub struct BabeNextEpochRef<'a>(&'a ());
impl<'a> BabeNextEpochRef<'a> {
pub fn scale_encoding(
&self,
) -> impl Iterator<Item = impl AsRef<[u8]> + Clone + 'a> + Clone + 'a {
std::iter::once([1])
// Make a tuple `(?x, ?y)` and equate it with `(impl Default, u32)`.
// For us to try and prove a `Subtype(impl Default, u32)` obligation,
// we have to instantiate both `?x` and `?y` without any
// `select_where_possible` calls inbetween.
let mut tup = &mut (x, y);
let assign_tup = &mut (foo(), 1u32);
tup = assign_tup;
}
1u32
}
fn main() {}

21
tests/ui/impl-trait/lazy_subtyping_of_opaques.stderr
View File

@ -1,21 +0,0 @@
error[E0277]: the trait bound `Either<Either<Map<Map<impl Iterator<Item = impl AsRef<[u8]> + Clone + '_> + Clone + '_, fn(impl AsRef<[u8]> + Clone + '_) -> Either<impl AsRef<[u8]> + Clone + '_, _> {Either::<impl AsRef<[u8]> + Clone + '_, _>::Left}>, fn(Either<impl AsRef<[u8]> + Clone + '_, _>) -> Either<Either<impl AsRef<[u8]> + Clone + '_, _>, Either<[{integer}; 1], [{integer}; 1]>> {Either::<Either<impl AsRef<[u8]> + Clone + '_, _>, Either<[{integer}; 1], [{integer}; 1]>>::Left}>, _>, std::iter::Chain<std::iter::Once<Either<Either<impl AsRef<[u8]> + Clone + '_, _>, Either<[{integer}; 1], [{integer}; 1]>>>, Map<Map<std::iter::Once<[{integer}; 1]>, fn([{integer}; 1]) -> Either<[{integer}; 1], [{integer}; 1]> {Either::<[{integer}; 1], [{integer}; 1]>::Right}>, fn(Either<[{integer}; 1], [{integer}; 1]>) -> Either<Either<impl AsRef<[u8]> + Clone + '_, _>, Either<[{integer}; 1], [{integer}; 1]>> {Either::<Either<impl AsRef<[u8]> + Clone + '_, _>, Either<[{integer}; 1], [{integer}; 1]>>::Right}>>>: Clone` is not satisfied
--> $DIR/lazy_subtyping_of_opaques.rs:30:10
|
LL | ) -> impl Iterator<Item = impl AsRef<[u8]> + Clone + 'a> + Clone + 'a {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `Clone` is not implemented for `Either<Either<Map<Map<impl Iterator<Item = impl AsRef<[u8]> + Clone + '_> + Clone + '_, fn(impl AsRef<[u8]> + Clone + '_) -> Either<impl AsRef<[u8]> + Clone + '_, _> {Either::<impl AsRef<[u8]> + Clone + '_, _>::Left}>, fn(Either<impl AsRef<[u8]> + Clone + '_, _>) -> Either<Either<impl AsRef<[u8]> + Clone + '_, _>, Either<[{integer}; 1], [{integer}; 1]>> {Either::<Either<impl AsRef<[u8]> + Clone + '_, _>, Either<[{integer}; 1], [{integer}; 1]>>::Left}>, _>, std::iter::Chain<std::iter::Once<Either<Either<impl AsRef<[u8]> + Clone + '_, _>, Either<[{integer}; 1], [{integer}; 1]>>>, Map<Map<std::iter::Once<[{integer}; 1]>, fn([{integer}; 1]) -> Either<[{integer}; 1], [{integer}; 1]> {Either::<[{integer}; 1], [{integer}; 1]>::Right}>, fn(Either<[{integer}; 1], [{integer}; 1]>) -> Either<Either<impl AsRef<[u8]> + Clone + '_, _>, Either<[{integer}; 1], [{integer}; 1]>> {Either::<Either<impl AsRef<[u8]> + Clone + '_, _>, Either<[{integer}; 1], [{integer}; 1]>>::Right}>>>`
error[E0277]: the trait bound `Either<Either<impl AsRef<[u8]> + Clone + '_, _>, Either<[{integer}; 1], [{integer}; 1]>>: AsRef<[u8]>` is not satisfied
--> $DIR/lazy_subtyping_of_opaques.rs:30:31
|
LL | ) -> impl Iterator<Item = impl AsRef<[u8]> + Clone + 'a> + Clone + 'a {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `AsRef<[u8]>` is not implemented for `Either<Either<impl AsRef<[u8]> + Clone + '_, _>, Either<[{integer}; 1], [{integer}; 1]>>`
error[E0277]: the trait bound `Either<Either<impl AsRef<[u8]> + Clone + '_, _>, Either<[{integer}; 1], [{integer}; 1]>>: Clone` is not satisfied
--> $DIR/lazy_subtyping_of_opaques.rs:30:31
|
LL | ) -> impl Iterator<Item = impl AsRef<[u8]> + Clone + 'a> + Clone + 'a {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `Clone` is not implemented for `Either<Either<impl AsRef<[u8]> + Clone + '_, _>, Either<[{integer}; 1], [{integer}; 1]>>`
error: aborting due to 3 previous errors
For more information about this error, try `rustc --explain E0277`.

3
tests/ui/type-alias-impl-trait/lazy_subtyping_of_opaques.rs
View File

@ -7,9 +7,10 @@
type Tait = impl FnOnce() -> ();
fn reify_as_tait() -> Thunk<Tait> {
//~^ ERROR: expected a `FnOnce()` closure, found `()`
Thunk::new(|cont| cont)
//~^ ERROR: mismatched types
//~| ERROR: mismatched types
//~| ERROR: expected a `FnOnce()` closure, found `()`
}
struct Thunk<F>(F);

31
tests/ui/type-alias-impl-trait/lazy_subtyping_of_opaques.stderr
View File

@ -1,26 +1,31 @@
error[E0308]: mismatched types
--> $DIR/lazy_subtyping_of_opaques.rs:10:23
error[E0277]: expected a `FnOnce()` closure, found `()`
--> $DIR/lazy_subtyping_of_opaques.rs:11:23
|
LL | type Tait = impl FnOnce() -> ();
| ------------------- the found opaque type
...
LL | Thunk::new(|cont| cont)
| ^^^^ expected `()`, found opaque type
| ^^^^ expected an `FnOnce()` closure, found `()`
|
= note: expected unit type `()`
found opaque type `Tait`
= help: the trait `FnOnce()` is not implemented for `()`
= note: wrap the `()` in a closure with no arguments: `|| { /* code */ }`
error[E0308]: mismatched types
--> $DIR/lazy_subtyping_of_opaques.rs:10:5
error[E0277]: expected a `FnOnce()` closure, found `()`
--> $DIR/lazy_subtyping_of_opaques.rs:9:23
|
LL | fn reify_as_tait() -> Thunk<Tait> {
| ----------- expected `Thunk<_>` because of return type
| ^^^^^^^^^^^ expected an `FnOnce()` closure, found `()`
|
= help: the trait `FnOnce()` is not implemented for `()`
= note: wrap the `()` in a closure with no arguments: `|| { /* code */ }`
error[E0308]: mismatched types
--> $DIR/lazy_subtyping_of_opaques.rs:11:5
|
LL | Thunk::new(|cont| cont)
| ^^^^^^^^^^^^^^^^^^^^^^^ expected `Thunk<_>`, found `()`
|
= note: expected struct `Thunk<_>`
found unit type `()`
error: aborting due to 2 previous errors
error: aborting due to 3 previous errors
For more information about this error, try `rustc --explain E0308`.
Some errors have detailed explanations: E0277, E0308.
For more information about an error, try `rustc --explain E0277`.