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generic_const_args: fix unreachable #162937

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generic_const_args: fix unreachable #162937

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7 changes: 3 additions & 4 deletions compiler/rustc_mir_build/src/builder/expr/as_constant.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -80,9 +80,8 @@ pub(crate) fn as_constant_inner<'tcx>(
// FIXME(generic_const_args): there's a lot to consider here! `Const::Ty` uses valtrees
// and `Const::Unevaluated` does not, we should revisit this before stabilization.
let def_kind = tcx.def_kind(def_id);
if tcx.features().generic_const_args()
|| matches!(def_kind, DefKind::Const | DefKind::AssocConst)
&& tcx.is_direct_const(def_id)
if matches!(def_kind, DefKind::Const | DefKind::AssocConst)

@BoxyUwU BoxyUwU Sep 18, 2026 •
edited by rustbot
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haha when I was reviewing that PR I thought about how I hate precedence on these things and can never tell where the parens go 😆

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&& (tcx.features().generic_const_args() || tcx.is_direct_const(def_id))
{
let kind = match def_kind {
DefKind::AssocConst => {
Expand All @@ -94,7 +93,7 @@ pub(crate) fn as_constant_inner<'tcx>(
}
}
DefKind::Const => ty::AliasConstKind::Free { def_id },
_ => unreachable!(),
kind => bug!("unexpected DefKind in THIR ExprKind::NamedConst: {kind:?}"),
};
let alias = ty::AliasConst::new(tcx, kind, args);
let ct = ty::Const::new_alias(tcx, ty::IsRigid::No, alias);
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10 changes: 10 additions & 0 deletions tests/ui/const-generics/gca/const-reference-to-constructor.rs
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Original file line number Diff line number Diff line change
@@ -0,0 +1,10 @@
//@ check-pass
//@ compile-flags: -Znext-solver
//! https://github.com/rust-lang/rust/issues/162923
#![feature(min_generic_const_args)]
#![feature(generic_const_args)]
enum T<const N: u8 = { T::<0>::B as u8 }> {
A = 2,
B,
}
fn main() {}
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