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Merged
merged 6 commits into from
Mar 7, 2024
Merged

silence mismatched types errors for implied projections #121863

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6fa58be
add test for assoc type mismatch in supertrait
Feb 29, 2024
189e784
adjust obligation spans for super projections
Feb 8, 2024
443c816
rename `ast_*` to `hir_*` in wfcheck
Mar 1, 2024
aa55f6d
suppress fulfillment errors for super projections
Mar 1, 2024
6bd970d
address review feedback
Mar 4, 2024
db48b93
improve debug logging
Mar 7, 2024
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suppress fulfillment errors for super projections
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Lukas Markeffsky committed Mar 4, 2024
commit aa55f6daa2c83020a271077bb15590755f4119d9
69 changes: 38 additions & 31 deletions compiler/rustc_trait_selection/src/traits/error_reporting/type_err_ctxt_ext.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1389,38 +1389,45 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
return true;
}

// FIXME: It should be possible to deal with `ForAll` in a cleaner way.
let bound_error = error.kind();
let (cond, error) = match (cond.kind().skip_binder(), bound_error.skip_binder()) {
(
ty::PredicateKind::Clause(ty::ClauseKind::Trait(..)),
ty::PredicateKind::Clause(ty::ClauseKind::Trait(error)),
) => (cond, bound_error.rebind(error)),
_ => {
// FIXME: make this work in other cases too.
return false;
}
};

for pred in elaborate(self.tcx, std::iter::once(cond)) {
let bound_predicate = pred.kind();
if let ty::PredicateKind::Clause(ty::ClauseKind::Trait(implication)) =
bound_predicate.skip_binder()
{
let error = error.to_poly_trait_ref();
let implication = bound_predicate.rebind(implication.trait_ref);
// FIXME: I'm just not taking associated types at all here.
// Eventually I'll need to implement param-env-aware
// `Γ₁ ⊦ φ₁ => Γ₂ ⊦ φ₂` logic.
let param_env = ty::ParamEnv::empty();
if self.can_sub(param_env, error, implication) {
debug!("error_implies: {:?} -> {:?} -> {:?}", cond, error, implication);
return true;
}
}
if let Some(error) = error.to_opt_poly_trait_pred() {
elaborate(self.tcx, std::iter::once(cond))
.filter_map(|implied| implied.to_opt_poly_trait_pred())
.any(|implied| {
if error.polarity() != implied.polarity() {
return false;
}
let error = error.to_poly_trait_ref();
let implied = implied.to_poly_trait_ref();
// FIXME: I'm just not taking associated types at all here.
// Eventually I'll need to implement param-env-aware
// `Γ₁ ⊦ φ₁ => Γ₂ ⊦ φ₂` logic.
let param_env = ty::ParamEnv::empty();
let is_implied = self.can_sub(param_env, error, implied);
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can you also use self.enter_forall(error, ...) here and manually instantiate implied with infer vars?

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Isn't that exactly what can_sub already does for PolyTraitRefs?

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@lcnr lcnr Mar 4, 2024 •
edited
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yes, that's something I dislike though. It's subtle and hard to understand, I've already seem other people accidentally using sub inside of the trait system for non-binders because that's what they've seen used. To prevent bugs when using Ty<'tcx> instead of Binder<Ty<'tcx>>, I prefer manually instantiating binders everywhere.

if is_implied {
debug!("error_implies: {:?} -> {:?} -> {:?}", cond, error, implied);
}
is_implied
})
} else if let Some(error) = error.to_opt_poly_projection_pred() {
self.enter_forall(error, |error| {
elaborate(self.tcx, std::iter::once(cond))
.filter_map(|implied| implied.to_opt_poly_projection_pred())
.any(|implied| {
self.enter_forall(implied, |implied| {
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you should instantiate cond with existentials here, not forall. You want to prove cond -> error (forall<T> cond<T> => forall<U> error<U>). This holds if forall<U> exists<T> cond<T> eq errorU> holds

let param_env = ty::ParamEnv::empty();
let is_implied =
self.can_eq(param_env, error.projection_ty, implied.projection_ty)
&& self.can_eq(param_env, error.term, implied.term);
if is_implied {
debug!("error_implies: {:?} -> {:?} -> {:?}", cond, error, implied);
}
is_implied
})
})
})
} else {
false
}

false
}

#[instrument(skip(self), level = "debug")]
Expand Down
1 change: 0 additions & 1 deletion tests/ui/issues/issue-33941.rs
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Expand Up @@ -5,5 +5,4 @@ use std::collections::HashMap;
fn main() {
for _ in HashMap::new().iter().cloned() {} //~ ERROR expected `Iter<'_, _, _>` to be an iterator that yields `&_`, but it yields `(&_, &_)`
//~^ ERROR expected `Iter<'_, _, _>` to be an iterator that yields `&_`, but it yields `(&_, &_)`
//~| ERROR expected `Iter<'_, _, _>` to be an iterator that yields `&_`, but it yields `(&_, &_)`
}
12 changes: 1 addition & 11 deletions tests/ui/issues/issue-33941.stderr
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Expand Up @@ -27,16 +27,6 @@ LL | for _ in HashMap::new().iter().cloned() {}
= note: required for `Cloned<std::collections::hash_map::Iter<'_, _, _>>` to implement `Iterator`
= note: required for `Cloned<std::collections::hash_map::Iter<'_, _, _>>` to implement `IntoIterator`

error[E0271]: expected `Iter<'_, _, _>` to be an iterator that yields `&_`, but it yields `(&_, &_)`
--> $DIR/issue-33941.rs:6:14
|
LL | for _ in HashMap::new().iter().cloned() {}
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `(&_, &_)`, found `&_`
|
= note: expected tuple `(&_, &_)`
found reference `&_`
= note: required for `Cloned<std::collections::hash_map::Iter<'_, _, _>>` to implement `Iterator`

error: aborting due to 3 previous errors
error: aborting due to 2 previous errors

For more information about this error, try `rustc --explain E0271`.
5 changes: 0 additions & 5 deletions tests/ui/trait-bounds/super-assoc-mismatch.rs
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Expand Up @@ -9,20 +9,17 @@ trait Sub: Super<Assoc = u16> {}
trait BoundOnSelf: Sub {}
impl BoundOnSelf for () {}
//~^ ERROR the trait bound `(): Sub` is not satisfied
//~| ERROR type mismatch resolving `<() as Super>::Assoc == u16`

trait BoundOnParam<T: Sub> {}
impl BoundOnParam<()> for () {}
//~^ ERROR the trait bound `(): Sub` is not satisfied
//~| ERROR type mismatch resolving `<() as Super>::Assoc == u16`

trait BoundOnAssoc {
type Assoc: Sub;
}
impl BoundOnAssoc for () {
type Assoc = ();
//~^ ERROR the trait bound `(): Sub` is not satisfied
//~| ERROR type mismatch resolving `<() as Super>::Assoc == u16`
}

trait BoundOnGat where Self::Assoc<u8>: Sub {
Expand All @@ -31,11 +28,9 @@ trait BoundOnGat where Self::Assoc<u8>: Sub {
impl BoundOnGat for u8 {
type Assoc<T> = ();
//~^ ERROR the trait bound `(): Sub` is not satisfied
//~| ERROR type mismatch resolving `<() as Super>::Assoc == u16`
}

fn trivial_bound() where (): Sub {}
//~^ ERROR the trait bound `(): Sub` is not satisfied
//~| ERROR type mismatch resolving `<() as Super>::Assoc == u16`

fn main() {}
121 changes: 9 additions & 112 deletions tests/ui/trait-bounds/super-assoc-mismatch.stderr
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Expand Up @@ -15,30 +15,8 @@ note: required by a bound in `BoundOnSelf`
LL | trait BoundOnSelf: Sub {}
| ^^^ required by this bound in `BoundOnSelf`

error[E0271]: type mismatch resolving `<() as Super>::Assoc == u16`
--> $DIR/super-assoc-mismatch.rs:10:22
|
LL | impl BoundOnSelf for () {}
| ^^ type mismatch resolving `<() as Super>::Assoc == u16`
|
note: expected this to be `u16`
--> $DIR/super-assoc-mismatch.rs:5:18
|
LL | type Assoc = u8;
| ^^
note: required for `()` to implement `Sub`
--> $DIR/super-assoc-mismatch.rs:7:7
|
LL | trait Sub: Super<Assoc = u16> {}
| ^^^
note: required by a bound in `BoundOnSelf`
--> $DIR/super-assoc-mismatch.rs:9:20
|
LL | trait BoundOnSelf: Sub {}
| ^^^ required by this bound in `BoundOnSelf`

error[E0277]: the trait bound `(): Sub` is not satisfied
--> $DIR/super-assoc-mismatch.rs:15:27
--> $DIR/super-assoc-mismatch.rs:14:27
|
LL | impl BoundOnParam<()> for () {}
| ^^ the trait `Sub` is not implemented for `()`
Expand All @@ -49,35 +27,13 @@ help: this trait has no implementations, consider adding one
LL | trait Sub: Super<Assoc = u16> {}
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
note: required by a bound in `BoundOnParam`
--> $DIR/super-assoc-mismatch.rs:14:23
|
LL | trait BoundOnParam<T: Sub> {}
| ^^^ required by this bound in `BoundOnParam`

error[E0271]: type mismatch resolving `<() as Super>::Assoc == u16`
--> $DIR/super-assoc-mismatch.rs:15:27
|
LL | impl BoundOnParam<()> for () {}
| ^^ type mismatch resolving `<() as Super>::Assoc == u16`
|
note: expected this to be `u16`
--> $DIR/super-assoc-mismatch.rs:5:18
|
LL | type Assoc = u8;
| ^^
note: required for `()` to implement `Sub`
--> $DIR/super-assoc-mismatch.rs:7:7
|
LL | trait Sub: Super<Assoc = u16> {}
| ^^^
note: required by a bound in `BoundOnParam`
--> $DIR/super-assoc-mismatch.rs:14:23
--> $DIR/super-assoc-mismatch.rs:13:23
|
LL | trait BoundOnParam<T: Sub> {}
| ^^^ required by this bound in `BoundOnParam`

error[E0277]: the trait bound `(): Sub` is not satisfied
--> $DIR/super-assoc-mismatch.rs:23:18
--> $DIR/super-assoc-mismatch.rs:21:18
|
LL | type Assoc = ();
| ^^ the trait `Sub` is not implemented for `()`
Expand All @@ -88,35 +44,13 @@ help: this trait has no implementations, consider adding one
LL | trait Sub: Super<Assoc = u16> {}
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
note: required by a bound in `BoundOnAssoc::Assoc`
--> $DIR/super-assoc-mismatch.rs:20:17
|
LL | type Assoc: Sub;
| ^^^ required by this bound in `BoundOnAssoc::Assoc`

error[E0271]: type mismatch resolving `<() as Super>::Assoc == u16`
--> $DIR/super-assoc-mismatch.rs:23:18
|
LL | type Assoc = ();
| ^^ type mismatch resolving `<() as Super>::Assoc == u16`
|
note: expected this to be `u16`
--> $DIR/super-assoc-mismatch.rs:5:18
|
LL | type Assoc = u8;
| ^^
note: required for `<() as BoundOnAssoc>::Assoc` to implement `Sub`
--> $DIR/super-assoc-mismatch.rs:7:7
|
LL | trait Sub: Super<Assoc = u16> {}
| ^^^
note: required by a bound in `BoundOnAssoc::Assoc`
--> $DIR/super-assoc-mismatch.rs:20:17
--> $DIR/super-assoc-mismatch.rs:18:17
|
LL | type Assoc: Sub;
| ^^^ required by this bound in `BoundOnAssoc::Assoc`

error[E0277]: the trait bound `(): Sub` is not satisfied
--> $DIR/super-assoc-mismatch.rs:32:21
--> $DIR/super-assoc-mismatch.rs:29:21
|
LL | type Assoc<T> = ();
| ^^ the trait `Sub` is not implemented for `()`, which is required by `<u8 as BoundOnGat>::Assoc<u8>: Sub`
Expand All @@ -127,35 +61,13 @@ help: this trait has no implementations, consider adding one
LL | trait Sub: Super<Assoc = u16> {}
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
note: required by a bound in `BoundOnGat`
--> $DIR/super-assoc-mismatch.rs:28:41
|
LL | trait BoundOnGat where Self::Assoc<u8>: Sub {
| ^^^ required by this bound in `BoundOnGat`

error[E0271]: type mismatch resolving `<() as Super>::Assoc == u16`
--> $DIR/super-assoc-mismatch.rs:32:21
|
LL | type Assoc<T> = ();
| ^^ type mismatch resolving `<() as Super>::Assoc == u16`
|
note: expected this to be `u16`
--> $DIR/super-assoc-mismatch.rs:5:18
|
LL | type Assoc = u8;
| ^^
note: required for `<u8 as BoundOnGat>::Assoc<u8>` to implement `Sub`
--> $DIR/super-assoc-mismatch.rs:7:7
|
LL | trait Sub: Super<Assoc = u16> {}
| ^^^
note: required by a bound in `BoundOnGat`
--> $DIR/super-assoc-mismatch.rs:28:41
--> $DIR/super-assoc-mismatch.rs:25:41
|
LL | trait BoundOnGat where Self::Assoc<u8>: Sub {
| ^^^ required by this bound in `BoundOnGat`

error[E0277]: the trait bound `(): Sub` is not satisfied
--> $DIR/super-assoc-mismatch.rs:37:26
--> $DIR/super-assoc-mismatch.rs:33:26
|
LL | fn trivial_bound() where (): Sub {}
| ^^^^^^^ the trait `Sub` is not implemented for `()`
Expand All @@ -168,21 +80,6 @@ LL | trait Sub: Super<Assoc = u16> {}
= help: see issue #48214
= help: add `#![feature(trivial_bounds)]` to the crate attributes to enable

error[E0271]: type mismatch resolving `<() as Super>::Assoc == u16`
--> $DIR/super-assoc-mismatch.rs:37:26
|
LL | fn trivial_bound() where (): Sub {}
| ^^^^^^^ type mismatch resolving `<() as Super>::Assoc == u16`
|
note: expected this to be `u8`
--> $DIR/super-assoc-mismatch.rs:5:18
|
LL | type Assoc = u8;
| ^^
= help: see issue #48214
= help: add `#![feature(trivial_bounds)]` to the crate attributes to enable

error: aborting due to 10 previous errors
error: aborting due to 5 previous errors

Some errors have detailed explanations: E0271, E0277.
For more information about an error, try `rustc --explain E0271`.
For more information about this error, try `rustc --explain E0277`.