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Do not feed anon const a type that references generics that it does not have

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This commit is contained in:
Michael Goulet 2025-03-09 18:23:17 +00:00
parent 385970f0c1
commit ed6dfddfeb
5 changed files with 76 additions and 13 deletions
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25
compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs
View file

@ -2294,18 +2294,14 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
{
let anon_const_type = tcx.type_of(param_def_id).instantiate(tcx, args);
// We must error if the instantiated type has any inference variables as we will
// use this type to feed the `type_of` and query results must not contain inference
// variables otherwise we will ICE.
//
// FIXME(generic_const_parameter_types): Ideally we remove these errors below when
// we have the ability to intermix typeck of anon const const args with the parent
// bodies typeck.
// We also error if the type contains any regions as effectively any region will wind
// up as a region variable in mir borrowck. It would also be somewhat concerning if
// hir typeck was using equality but mir borrowck wound up using subtyping as that could
// result in a non-infer in hir typeck but a region variable in borrowck.
//
// FIXME(generic_const_parameter_types): Ideally we remove these errors one day when
// we have the ability to intermix typeck of anon const const args with the parent
// bodies typeck.
if tcx.features().generic_const_parameter_types()
&& (anon_const_type.has_free_regions() || anon_const_type.has_erased_regions())
{
@ -2316,6 +2312,9 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
tcx.feed_anon_const_type(anon.def_id, ty::EarlyBinder::bind(Ty::new_error(tcx, e)));
return ty::Const::new_error(tcx, e);
}
// We must error if the instantiated type has any inference variables as we will
// use this type to feed the `type_of` and query results must not contain inference
// variables otherwise we will ICE.
if anon_const_type.has_non_region_infer() {
let e = tcx.dcx().span_err(
const_arg.span(),
@ -2324,6 +2323,16 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
tcx.feed_anon_const_type(anon.def_id, ty::EarlyBinder::bind(Ty::new_error(tcx, e)));
return ty::Const::new_error(tcx, e);
}
// We error when the type contains unsubstituted generics since we do not currently
// give the anon const any of the generics from the parent.
if anon_const_type.has_non_region_param() {
let e = tcx.dcx().span_err(
const_arg.span(),
"anonymous constants referencing generics are not yet supported",
);
tcx.feed_anon_const_type(anon.def_id, ty::EarlyBinder::bind(Ty::new_error(tcx, e)));
return ty::Const::new_error(tcx, e);
}
tcx.feed_anon_const_type(
anon.def_id,

5
tests/crashes/137865.rs
View file

@ -1,5 +0,0 @@
//@ known-bug: #137865
trait Foo {
type Assoc<const N: Self>;
fn foo() -> Self::Assoc<3>;
}

25
tests/ui/const-generics/generic_const_parameter_types/references-parent-generics.feat.stderr Normal file
View file

@ -0,0 +1,25 @@
warning: the feature `generic_const_parameter_types` is incomplete and may not be safe to use and/or cause compiler crashes
--> $DIR/references-parent-generics.rs:3:27
|
LL | #![cfg_attr(feat, feature(generic_const_parameter_types))]
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= note: see issue #137626 <https://github.com/rust-lang/rust/issues/137626> for more information
= note: `#[warn(incomplete_features)]` on by default
error: `Self` is forbidden as the type of a const generic parameter
--> $DIR/references-parent-generics.rs:7:25
|
LL | type Assoc<const N: Self>;
| ^^^^
|
= note: the only supported types are integers, `bool`, and `char`
error: anonymous constants referencing generics are not yet supported
--> $DIR/references-parent-generics.rs:14:21
|
LL | let x: T::Assoc<3>;
| ^
error: aborting due to 2 previous errors; 1 warning emitted

16
tests/ui/const-generics/generic_const_parameter_types/references-parent-generics.nofeat.stderr Normal file
View file

@ -0,0 +1,16 @@
error: `Self` is forbidden as the type of a const generic parameter
--> $DIR/references-parent-generics.rs:7:25
|
LL | type Assoc<const N: Self>;
| ^^^^
|
= note: the only supported types are integers, `bool`, and `char`
error: anonymous constants referencing generics are not yet supported
--> $DIR/references-parent-generics.rs:14:21
|
LL | let x: T::Assoc<3>;
| ^
error: aborting due to 2 previous errors

18
tests/ui/const-generics/generic_const_parameter_types/references-parent-generics.rs Normal file
View file

@ -0,0 +1,18 @@
//@ revisions: feat nofeat
#![cfg_attr(feat, feature(generic_const_parameter_types))]
//[feat]~^ WARN the feature `generic_const_parameter_types` is incomplete
trait Foo {
type Assoc<const N: Self>;
//~^ ERROR `Self` is forbidden as the type of a const generic parameter
}
fn foo<T: Foo>() {
// We used to end up feeding the type of this anon const to be `T`, but the anon const
// doesn't inherit the generics of `foo`, which led to index oob errors.
let x: T::Assoc<3>;
//~^ ERROR anonymous constants referencing generics are not yet supported
}
fn main() {}