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hir_analysis: add missing sizedness bounds #142712

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8 changes: 8 additions & 0 deletions compiler/rustc_hir_analysis/src/collect/predicates_of.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -658,6 +658,14 @@ pub(super) fn implied_predicates_with_filter<'tcx>(
| PredicateFilter::SelfOnly
| PredicateFilter::SelfTraitThatDefines(_)
| PredicateFilter::SelfAndAssociatedTypeBounds => {
icx.lowerer().add_sizedness_bounds(
&mut bounds,
self_param_ty,
superbounds,
None,
Some(trait_def_id),
item.span,
);
icx.lowerer().add_default_super_traits(
trait_def_id,
&mut bounds,
Expand Down
18 changes: 11 additions & 7 deletions compiler/rustc_hir_analysis/src/hir_ty_lowering/bounds.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -215,14 +215,18 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
&& !collected.meta_sized.any()
&& !collected.pointee_sized.any()
{
// `?Sized` is equivalent to `MetaSized` (but only add the bound if there aren't any
// other explicit ones) - this can happen for trait aliases as well as bounds.
add_trait_bound(tcx, bounds, self_ty, meta_sized_did, span);
} else if !collected.any() {
if trait_did.is_some() {
// If there are no explicit sizedness bounds on a trait then add a default
// `MetaSized` supertrait.
if trait_did.map(|did| !tcx.is_trait_alias(did.to_def_id())).unwrap_or(true) {
// `?Sized` is equivalent to `MetaSized` (but only add the bound if there aren't any
// other explicit ones and it isn't a trait alias).
add_trait_bound(tcx, bounds, self_ty, meta_sized_did, span);
}
} else if !collected.any() {
if let Some(trait_did) = trait_did {
if !tcx.is_trait_alias(trait_did.to_def_id()) {
// If there are no explicit sizedness bounds on a trait and it is not a trait
// alias then add a default `MetaSized` supertrait.
add_trait_bound(tcx, bounds, self_ty, meta_sized_did, span);
}
} else {
// If there are no explicit sizedness bounds on a parameter then add a default
// `Sized` bound.
Expand Down
15 changes: 15 additions & 0 deletions tests/ui/sized-hierarchy/bound-on-assoc-type-projection.rs
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@fmease fmease Jun 19, 2025 •
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Do you think it would be worth adding the following regression test, too? It's probably redundant but it would be smaller:

#![feature(sized_hierarchy)]

trait Trait {}

fn f<T: Trait + std::marker::PointeeSized>() {}

On master it yields the error

error[E0277]: the size for values of type `T` cannot be known
 --> t.rs:5:9
  |
5 | fn f<T: Trait + std::marker::PointeeSized>() {}
  |         ^^^^^ doesn't have a known size

Trait should still imply MetaSized here in f's bounds, right?

Original file line number Diff line number Diff line change
@@ -0,0 +1,15 @@
//@ check-pass
#![crate_type = "lib"]
#![feature(sized_hierarchy)]

trait FalseDeref {
type Target: std::marker::PointeeSized;
}

trait Bar {}

fn foo<T: FalseDeref>()
where
T::Target: Bar,
{
}
5 changes: 1 addition & 4 deletions tests/ui/sized-hierarchy/default-supertrait.rs
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Expand Up @@ -47,14 +47,11 @@ fn with_pointeesized_supertrait<T: PointeeSized + PointeeSized_>() {
requires_pointeesized::<T>();
}

// `T` won't inherit the `const MetaSized` implicit supertrait of `Bare`, so there is an error on
// the bound, which is expected.
// `T` inherits the `const MetaSized` implicit supertrait of `Bare`.
fn with_bare_trait<T: PointeeSized + Bare>() {
//~^ ERROR the size for values of type `T` cannot be known
requires_sized::<T>();
//~^ ERROR the size for values of type `T` cannot be known
requires_metasized::<T>();
//~^ ERROR the size for values of type `T` cannot be known
requires_pointeesized::<T>();
}

Expand Down
37 changes: 2 additions & 35 deletions tests/ui/sized-hierarchy/default-supertrait.stderr
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Expand Up @@ -28,22 +28,6 @@ LL | trait NegPointeeSized: ?PointeeSized { }
= help: add `#![feature(more_maybe_bounds)]` to the crate attributes to enable
= note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

error[E0277]: the size for values of type `T` cannot be known
--> $DIR/default-supertrait.rs:52:38
|
LL | fn with_bare_trait<T: PointeeSized + Bare>() {
| ^^^^ doesn't have a known size
|
note: required by a bound in `Bare`
--> $DIR/default-supertrait.rs:22:1
|
LL | trait Bare {}
| ^^^^^^^^^^^^^ required by this bound in `Bare`
help: consider further restricting type parameter `T` with unstable trait `MetaSized`
|
LL | fn with_bare_trait<T: PointeeSized + Bare + std::marker::MetaSized>() {
| ++++++++++++++++++++++++

error[E0277]: the size for values of type `T` cannot be known at compilation time
--> $DIR/default-supertrait.rs:35:22
|
Expand Down Expand Up @@ -89,11 +73,10 @@ LL | fn with_pointeesized_supertrait<T: PointeeSized + PointeeSized_ + std::mark
| ++++++++++++++++++++++++

error[E0277]: the size for values of type `T` cannot be known at compilation time
--> $DIR/default-supertrait.rs:54:22
--> $DIR/default-supertrait.rs:52:22
|
LL | fn with_bare_trait<T: PointeeSized + Bare>() {
| - this type parameter needs to be `Sized`
LL |
LL | requires_sized::<T>();
| ^ doesn't have a size known at compile-time
|
Expand All @@ -103,23 +86,7 @@ note: required by a bound in `requires_sized`
LL | fn requires_sized<T: Sized>() {}
| ^^^^^ required by this bound in `requires_sized`

error[E0277]: the size for values of type `T` cannot be known
--> $DIR/default-supertrait.rs:56:26
|
LL | requires_metasized::<T>();
| ^ doesn't have a known size
|
note: required by a bound in `requires_metasized`
--> $DIR/default-supertrait.rs:25:26
|
LL | fn requires_metasized<T: MetaSized>() {}
| ^^^^^^^^^ required by this bound in `requires_metasized`
help: consider further restricting type parameter `T` with unstable trait `MetaSized`
|
LL | fn with_bare_trait<T: PointeeSized + Bare + std::marker::MetaSized>() {
| ++++++++++++++++++++++++

error: aborting due to 9 previous errors
error: aborting due to 7 previous errors

Some errors have detailed explanations: E0277, E0658.
For more information about an error, try `rustc --explain E0277`.
19 changes: 1 addition & 18 deletions tests/ui/traits/next-solver/normalize/normalize-param-env-2.stderr
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Original file line number Diff line number Diff line change
Expand Up @@ -19,23 +19,6 @@ error[E0275]: overflow evaluating the requirement `<() as A<T>>::Assoc: A<T>`
LL | Self::Assoc: A<T>,
| ^^^^

error[E0275]: overflow evaluating the requirement `<() as A<T>>::Assoc: MetaSized`
--> $DIR/normalize-param-env-2.rs:24:22
|
LL | Self::Assoc: A<T>,
| ^^^^
|
note: required by a bound in `A`
--> $DIR/normalize-param-env-2.rs:9:1
|
LL | / trait A<T> {
LL | | type Assoc;
LL | |
LL | | fn f()
... |
LL | | }
| |_^ required by this bound in `A`

error[E0275]: overflow evaluating the requirement `<() as A<T>>::Assoc well-formed`
--> $DIR/normalize-param-env-2.rs:24:22
|
Expand Down Expand Up @@ -63,6 +46,6 @@ LL | where
LL | Self::Assoc: A<T>,
| ^^^^ required by this bound in `A::f`

error: aborting due to 6 previous errors
error: aborting due to 5 previous errors

For more information about this error, try `rustc --explain E0275`.
16 changes: 1 addition & 15 deletions tests/ui/traits/next-solver/normalize/normalize-param-env-4.next.stderr
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Expand Up @@ -4,20 +4,6 @@ error[E0275]: overflow evaluating the requirement `<T as Trait>::Assoc: Trait`
LL | <T as Trait>::Assoc: Trait,
| ^^^^^

error[E0275]: overflow evaluating the requirement `<T as Trait>::Assoc: MetaSized`
--> $DIR/normalize-param-env-4.rs:19:26
|
LL | <T as Trait>::Assoc: Trait,
| ^^^^^
|
note: required by a bound in `Trait`
--> $DIR/normalize-param-env-4.rs:7:1
|
LL | / trait Trait {
LL | | type Assoc;
LL | | }
| |_^ required by this bound in `Trait`

error: aborting due to 2 previous errors
error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0275`.
17 changes: 12 additions & 5 deletions tests/ui/traits/non_lifetime_binders/drop-impl-pred.no.stderr
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@@ -1,5 +1,5 @@
warning: the feature `non_lifetime_binders` is incomplete and may not be safe to use and/or cause compiler crashes
--> $DIR/drop-impl-pred.rs:6:12
--> $DIR/drop-impl-pred.rs:5:12
|
LL | #![feature(non_lifetime_binders)]
| ^^^^^^^^^^^^^^^^^^^^
Expand All @@ -8,17 +8,24 @@ LL | #![feature(non_lifetime_binders)]
= note: `#[warn(incomplete_features)]` on by default

error[E0367]: `Drop` impl requires `H: Foo` but the struct it is implemented for does not
--> $DIR/drop-impl-pred.rs:19:15
--> $DIR/drop-impl-pred.rs:20:15
|
LL | for<H> H: Foo,
| ^^^
|
note: the implementor must specify the same requirement
--> $DIR/drop-impl-pred.rs:12:1
--> $DIR/drop-impl-pred.rs:11:1
|
LL | struct Bar<T>(T) where T: Foo;
| ^^^^^^^^^^^^^

error: aborting due to 1 previous error; 1 warning emitted
error[E0282]: type annotations needed
--> $DIR/drop-impl-pred.rs:16:18
|
LL | impl<T> Drop for Bar<T>
| ^^^^^^ cannot infer type for struct `Bar<T>`

error: aborting due to 2 previous errors; 1 warning emitted

For more information about this error, try `rustc --explain E0367`.
Some errors have detailed explanations: E0282, E0367.
For more information about an error, try `rustc --explain E0282`.
3 changes: 2 additions & 1 deletion tests/ui/traits/non_lifetime_binders/drop-impl-pred.rs
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Original file line number Diff line number Diff line change
@@ -1,5 +1,4 @@
//@ revisions: no yes
//@[yes] check-pass

// Issue 110557

Expand All @@ -15,6 +14,8 @@ struct Bar<T>(T) where T: Foo;
struct Bar<T>(T) where for<H> H: Foo;

impl<T> Drop for Bar<T>
//[yes]~^ ERROR type annotations needed
//[no]~^^ ERROR type annotations needed
where
for<H> H: Foo,
//[no]~^ ERROR `Drop` impl requires `H: Foo` but the struct it is implemented for does not
Expand Down
11 changes: 9 additions & 2 deletions tests/ui/traits/non_lifetime_binders/drop-impl-pred.yes.stderr
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@@ -1,11 +1,18 @@
warning: the feature `non_lifetime_binders` is incomplete and may not be safe to use and/or cause compiler crashes
--> $DIR/drop-impl-pred.rs:6:12
--> $DIR/drop-impl-pred.rs:5:12
|
LL | #![feature(non_lifetime_binders)]
| ^^^^^^^^^^^^^^^^^^^^
|
= note: see issue #108185 <https://github.com/rust-lang/rust/issues/108185> for more information
= note: `#[warn(incomplete_features)]` on by default

warning: 1 warning emitted
error[E0282]: type annotations needed
--> $DIR/drop-impl-pred.rs:16:18
|
LL | impl<T> Drop for Bar<T>
| ^^^^^^ cannot infer type for struct `Bar<T>`

error: aborting due to 1 previous error; 1 warning emitted

For more information about this error, try `rustc --explain E0282`.
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