Skip to content

Forbid generic parameters in types of #[type_const] items #150650

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
bors merged 1 commit into from
Jan 4, 2026
Merged

Forbid generic parameters in types of #[type_const] items #150650

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
58 changes: 55 additions & 3 deletions compiler/rustc_resolve/src/late.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -2855,6 +2855,7 @@ impl<'a, 'ast, 'ra, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
ref define_opaque,
..
}) => {
let is_type_const = attr::contains_name(&item.attrs, sym::type_const);
self.with_generic_param_rib(
&generics.params,
RibKind::Item(
Expand All @@ -2873,7 +2874,22 @@ impl<'a, 'ast, 'ra, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {

this.with_lifetime_rib(
LifetimeRibKind::Elided(LifetimeRes::Static),
|this| this.visit_ty(ty),
|this| {
if is_type_const
&& !this.r.tcx.features().generic_const_parameter_types()
{
this.with_rib(TypeNS, RibKind::ConstParamTy, |this| {
this.with_rib(ValueNS, RibKind::ConstParamTy, |this| {
this.with_lifetime_rib(
LifetimeRibKind::ConstParamTy,
|this| this.visit_ty(ty),
)
})
});
} else {
this.visit_ty(ty);
}
},
);

if let Some(rhs) = rhs {
Expand Down Expand Up @@ -3213,6 +3229,7 @@ impl<'a, 'ast, 'ra, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
define_opaque,
..
}) => {
let is_type_const = attr::contains_name(&item.attrs, sym::type_const);
self.with_generic_param_rib(
&generics.params,
RibKind::AssocItem,
Expand All @@ -3227,7 +3244,20 @@ impl<'a, 'ast, 'ra, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
},
|this| {
this.visit_generics(generics);
this.visit_ty(ty);
if is_type_const
&& !this.r.tcx.features().generic_const_parameter_types()
{
this.with_rib(TypeNS, RibKind::ConstParamTy, |this| {
this.with_rib(ValueNS, RibKind::ConstParamTy, |this| {
this.with_lifetime_rib(
LifetimeRibKind::ConstParamTy,
|this| this.visit_ty(ty),
)
})
});
} else {
this.visit_ty(ty);
}

// Only impose the restrictions of `ConstRibKind` for an
// actual constant expression in a provided default.
Expand Down Expand Up @@ -3422,6 +3452,7 @@ impl<'a, 'ast, 'ra, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
..
}) => {
debug!("resolve_implementation AssocItemKind::Const");
let is_type_const = attr::contains_name(&item.attrs, sym::type_const);
self.with_generic_param_rib(
&generics.params,
RibKind::AssocItem,
Expand Down Expand Up @@ -3458,7 +3489,28 @@ impl<'a, 'ast, 'ra, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
);

this.visit_generics(generics);
this.visit_ty(ty);
if is_type_const
&& !this
.r
.tcx
.features()
.generic_const_parameter_types()
{
this.with_rib(TypeNS, RibKind::ConstParamTy, |this| {
this.with_rib(
ValueNS,
RibKind::ConstParamTy,
|this| {
this.with_lifetime_rib(
LifetimeRibKind::ConstParamTy,
|this| this.visit_ty(ty),
)
},
)
});
} else {
this.visit_ty(ty);
}
if let Some(rhs) = rhs {
// We allow arbitrary const expressions inside of associated consts,
// even if they are potentially not const evaluatable.
Expand Down
1 change: 1 addition & 0 deletions tests/ui/associated-consts/assoc-const-eq-bound-var-in-ty-not-wf.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -5,6 +5,7 @@
min_generic_const_args,
adt_const_params,
unsized_const_params,
generic_const_parameter_types,
)]
#![allow(incomplete_features)]

Expand Down
4 changes: 2 additions & 2 deletions tests/ui/associated-consts/assoc-const-eq-bound-var-in-ty-not-wf.stderr
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -1,11 +1,11 @@
error: higher-ranked subtype error
--> $DIR/assoc-const-eq-bound-var-in-ty-not-wf.rs:21:13
--> $DIR/assoc-const-eq-bound-var-in-ty-not-wf.rs:22:13
|
LL | K = const { () }
| ^^^^^^^^^^^^

error: higher-ranked subtype error
--> $DIR/assoc-const-eq-bound-var-in-ty-not-wf.rs:21:13
--> $DIR/assoc-const-eq-bound-var-in-ty-not-wf.rs:22:13
|
LL | K = const { () }
| ^^^^^^^^^^^^
Expand Down
1 change: 1 addition & 0 deletions tests/ui/associated-consts/assoc-const-eq-bound-var-in-ty.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -8,6 +8,7 @@
min_generic_const_args,
adt_const_params,
unsized_const_params,
generic_const_parameter_types,
)]
#![allow(incomplete_features)]

Expand Down
7 changes: 6 additions & 1 deletion tests/ui/associated-consts/assoc-const-eq-esc-bound-var-in-ty.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -1,6 +1,11 @@
// Detect and reject escaping late-bound generic params in
// the type of assoc consts used in an equality bound.
#![feature(associated_const_equality, min_generic_const_args, unsized_const_params)]
#![feature(
associated_const_equality,
min_generic_const_args,
unsized_const_params,
generic_const_parameter_types,
)]
#![allow(incomplete_features)]

trait Trait<'a> {
Expand Down
2 changes: 1 addition & 1 deletion tests/ui/associated-consts/assoc-const-eq-esc-bound-var-in-ty.stderr
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -1,5 +1,5 @@
error: the type of the associated constant `K` cannot capture late-bound generic parameters
--> $DIR/assoc-const-eq-esc-bound-var-in-ty.rs:11:35
--> $DIR/assoc-const-eq-esc-bound-var-in-ty.rs:16:35
|
LL | fn take(_: impl for<'r> Trait<'r, K = const { &() }>) {}
| -- ^ its type cannot capture the late-bound lifetime parameter `'r`
Expand Down
1 change: 1 addition & 0 deletions tests/ui/associated-consts/assoc-const-eq-param-in-ty.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -5,6 +5,7 @@
min_generic_const_args,
adt_const_params,
unsized_const_params,
generic_const_parameter_types,
)]
#![allow(incomplete_features)]

Expand Down
22 changes: 11 additions & 11 deletions tests/ui/associated-consts/assoc-const-eq-param-in-ty.stderr
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -1,5 +1,5 @@
error: the type of the associated constant `K` must not depend on generic parameters
--> $DIR/assoc-const-eq-param-in-ty.rs:22:29
--> $DIR/assoc-const-eq-param-in-ty.rs:23:29
|
LL | fn take0<'r, A: 'r + ConstParamTy_, const Q: usize>(
| -- the lifetime parameter `'r` is defined here
Expand All @@ -10,7 +10,7 @@ LL | _: impl Trait<'r, A, Q, K = const { loop {} }>
= note: `K` has type `&'r [A; Q]`

error: the type of the associated constant `K` must not depend on generic parameters
--> $DIR/assoc-const-eq-param-in-ty.rs:22:29
--> $DIR/assoc-const-eq-param-in-ty.rs:23:29
|
LL | fn take0<'r, A: 'r + ConstParamTy_, const Q: usize>(
| - the type parameter `A` is defined here
Expand All @@ -21,7 +21,7 @@ LL | _: impl Trait<'r, A, Q, K = const { loop {} }>
= note: `K` has type `&'r [A; Q]`

error: the type of the associated constant `K` must not depend on generic parameters
--> $DIR/assoc-const-eq-param-in-ty.rs:22:29
--> $DIR/assoc-const-eq-param-in-ty.rs:23:29
|
LL | fn take0<'r, A: 'r + ConstParamTy_, const Q: usize>(
| - the const parameter `Q` is defined here
Expand All @@ -32,7 +32,7 @@ LL | _: impl Trait<'r, A, Q, K = const { loop {} }>
= note: `K` has type `&'r [A; Q]`

error: the type of the associated constant `SELF` must not depend on `impl Trait`
--> $DIR/assoc-const-eq-param-in-ty.rs:39:26
--> $DIR/assoc-const-eq-param-in-ty.rs:40:26
|
LL | fn take1(_: impl Project<SELF = const {}>) {}
| -------------^^^^------------
Expand All @@ -41,7 +41,7 @@ LL | fn take1(_: impl Project<SELF = const {}>) {}
| the `impl Trait` is specified here

error: the type of the associated constant `SELF` must not depend on generic parameters
--> $DIR/assoc-const-eq-param-in-ty.rs:44:21
--> $DIR/assoc-const-eq-param-in-ty.rs:45:21
|
LL | fn take2<P: Project<SELF = const {}>>(_: P) {}
| - ^^^^ its type must not depend on the type parameter `P`
Expand All @@ -51,7 +51,7 @@ LL | fn take2<P: Project<SELF = const {}>>(_: P) {}
= note: `SELF` has type `P`

error: the type of the associated constant `K` must not depend on generic parameters
--> $DIR/assoc-const-eq-param-in-ty.rs:53:52
--> $DIR/assoc-const-eq-param-in-ty.rs:54:52
|
LL | trait Iface<'r>: ConstParamTy_ {
| -- the lifetime parameter `'r` is defined here
Expand All @@ -62,15 +62,15 @@ LL | type Assoc<const Q: usize>: Trait<'r, Self, Q, K = const { loop {} }>
= note: `K` has type `&'r [Self; Q]`

error: the type of the associated constant `K` must not depend on `Self`
--> $DIR/assoc-const-eq-param-in-ty.rs:53:52
--> $DIR/assoc-const-eq-param-in-ty.rs:54:52
|
LL | type Assoc<const Q: usize>: Trait<'r, Self, Q, K = const { loop {} }>
| ^ its type must not depend on `Self`
|
= note: `K` has type `&'r [Self; Q]`

error: the type of the associated constant `K` must not depend on generic parameters
--> $DIR/assoc-const-eq-param-in-ty.rs:53:52
--> $DIR/assoc-const-eq-param-in-ty.rs:54:52
|
LL | type Assoc<const Q: usize>: Trait<'r, Self, Q, K = const { loop {} }>
| - ^ its type must not depend on the const parameter `Q`
Expand All @@ -80,7 +80,7 @@ LL | type Assoc<const Q: usize>: Trait<'r, Self, Q, K = const { loop {} }>
= note: `K` has type `&'r [Self; Q]`

error: the type of the associated constant `K` must not depend on generic parameters
--> $DIR/assoc-const-eq-param-in-ty.rs:53:52
--> $DIR/assoc-const-eq-param-in-ty.rs:54:52
|
LL | trait Iface<'r>: ConstParamTy_ {
| -- the lifetime parameter `'r` is defined here
Expand All @@ -92,7 +92,7 @@ LL | type Assoc<const Q: usize>: Trait<'r, Self, Q, K = const { loop {} }>
= note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`

error: the type of the associated constant `K` must not depend on `Self`
--> $DIR/assoc-const-eq-param-in-ty.rs:53:52
--> $DIR/assoc-const-eq-param-in-ty.rs:54:52
|
LL | type Assoc<const Q: usize>: Trait<'r, Self, Q, K = const { loop {} }>
| ^ its type must not depend on `Self`
Expand All @@ -101,7 +101,7 @@ LL | type Assoc<const Q: usize>: Trait<'r, Self, Q, K = const { loop {} }>
= note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`

error: the type of the associated constant `K` must not depend on generic parameters
--> $DIR/assoc-const-eq-param-in-ty.rs:53:52
--> $DIR/assoc-const-eq-param-in-ty.rs:54:52
|
LL | type Assoc<const Q: usize>: Trait<'r, Self, Q, K = const { loop {} }>
| - ^ its type must not depend on the const parameter `Q`
Expand Down
1 change: 1 addition & 0 deletions tests/ui/associated-consts/assoc-const-eq-supertraits.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -8,6 +8,7 @@
min_generic_const_args,
adt_const_params,
unsized_const_params,
generic_const_parameter_types,
)]
#![allow(incomplete_features)]

Expand Down
38 changes: 38 additions & 0 deletions tests/ui/const-generics/mgca/type_const-generic-param-in-type.gate.stderr
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -0,0 +1,38 @@
error: anonymous constants referencing generics are not yet supported
--> $DIR/type_const-generic-param-in-type.rs:9:53
|
LL | const FOO<T: core::marker::ConstParamTy_>: [T; 0] = const { [] };
| ^^^^^^^^^^^^

error: anonymous constants referencing generics are not yet supported
--> $DIR/type_const-generic-param-in-type.rs:14:38
|
LL | const BAR<const N: usize>: [(); N] = const { [] };
| ^^^^^^^^^^^^

error: anonymous constants with lifetimes in their type are not yet supported
--> $DIR/type_const-generic-param-in-type.rs:19:30
|
LL | const BAZ<'a>: [&'a (); 0] = const { [] };
| ^^^^^^^^^^^^

error: anonymous constants referencing generics are not yet supported
--> $DIR/type_const-generic-param-in-type.rs:39:59
|
LL | const ASSOC<T: core::marker::ConstParamTy_>: [T; 0] = const { [] };
| ^^^^^^^^^^^^

error: anonymous constants referencing generics are not yet supported
--> $DIR/type_const-generic-param-in-type.rs:44:50
|
LL | const ASSOC_CONST<const N: usize>: [(); N] = const { [] };
| ^^^^^^^^^^^^

error: anonymous constants with lifetimes in their type are not yet supported
--> $DIR/type_const-generic-param-in-type.rs:49:39
|
LL | const ASSOC_LT<'a>: [&'a (); 0] = const { [] };
| ^^^^^^^^^^^^

error: aborting due to 6 previous errors

57 changes: 57 additions & 0 deletions tests/ui/const-generics/mgca/type_const-generic-param-in-type.nogate.stderr
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -0,0 +1,57 @@
error[E0770]: the type of const parameters must not depend on other generic parameters
--> $DIR/type_const-generic-param-in-type.rs:9:45
|
LL | const FOO<T: core::marker::ConstParamTy_>: [T; 0] = const { [] };
| ^ the type must not depend on the parameter `T`

error[E0770]: the type of const parameters must not depend on other generic parameters
--> $DIR/type_const-generic-param-in-type.rs:14:33
|
LL | const BAR<const N: usize>: [(); N] = const { [] };
| ^ the type must not depend on the parameter `N`

error[E0770]: the type of const parameters must not depend on other generic parameters
--> $DIR/type_const-generic-param-in-type.rs:19:18
|
LL | const BAZ<'a>: [&'a (); 0] = const { [] };
| ^^ the type must not depend on the parameter `'a`

error[E0770]: the type of const parameters must not depend on other generic parameters
--> $DIR/type_const-generic-param-in-type.rs:25:51
|
LL | const ASSOC<T: core::marker::ConstParamTy_>: [T; 0];
| ^ the type must not depend on the parameter `T`

error[E0770]: the type of const parameters must not depend on other generic parameters
--> $DIR/type_const-generic-param-in-type.rs:29:45
|
LL | const ASSOC_CONST<const N: usize>: [(); N];
| ^ the type must not depend on the parameter `N`

error[E0770]: the type of const parameters must not depend on other generic parameters
--> $DIR/type_const-generic-param-in-type.rs:33:27
|
LL | const ASSOC_LT<'a>: [&'a (); 0];
| ^^ the type must not depend on the parameter `'a`

error[E0770]: the type of const parameters must not depend on other generic parameters
--> $DIR/type_const-generic-param-in-type.rs:39:51
|
LL | const ASSOC<T: core::marker::ConstParamTy_>: [T; 0] = const { [] };
| ^ the type must not depend on the parameter `T`

error[E0770]: the type of const parameters must not depend on other generic parameters
--> $DIR/type_const-generic-param-in-type.rs:44:45
|
LL | const ASSOC_CONST<const N: usize>: [(); N] = const { [] };
| ^ the type must not depend on the parameter `N`

error[E0770]: the type of const parameters must not depend on other generic parameters
--> $DIR/type_const-generic-param-in-type.rs:49:27
|
LL | const ASSOC_LT<'a>: [&'a (); 0] = const { [] };
| ^^ the type must not depend on the parameter `'a`

error: aborting due to 9 previous errors

For more information about this error, try `rustc --explain E0770`.
Loading
Loading