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Rollup merge of #138256 - compiler-errors:anon-const-ty, r=BoxyUwU

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

Fixes #137865

See the comment I left in the code. We could alternatively give these anon consts the generics from the parent, but that would be moving in a GCE-esque direction that we may not want. Open to tweaks here.

r? BoxyUwU
This commit is contained in:
Matthias Krüger 2025-03-11 19:35:31 +01:00 • committed by GitHub
commit 4ff58c9103
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5 changed files with 76 additions and 13 deletions
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25
compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs
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@ -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,