From d32dd9e452b1575d9a93830e194c1d0133844327 Mon Sep 17 00:00:00 2001
From: khyperia <953151+khyperia@users.noreply.github.com>
Date: Fri, 18 Sep 2026 08:25:39 +0200
Subject: [PATCH] gca: fix unreachable

---
 .../rustc_mir_build/src/builder/expr/as_constant.rs    |  7 +++----
 .../gca/const-reference-to-constructor.rs              | 10 ++++++++++
 2 files changed, 13 insertions(+), 4 deletions(-)
 create mode 100644 tests/ui/const-generics/gca/const-reference-to-constructor.rs

diff --git a/compiler/rustc_mir_build/src/builder/expr/as_constant.rs b/compiler/rustc_mir_build/src/builder/expr/as_constant.rs
index eb9f56d887684..7592c48c3a35c 100644
--- a/compiler/rustc_mir_build/src/builder/expr/as_constant.rs
+++ b/compiler/rustc_mir_build/src/builder/expr/as_constant.rs
@@ -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)
+                && (tcx.features().generic_const_args() || tcx.is_direct_const(def_id))
             {
                 let kind = match def_kind {
                     DefKind::AssocConst => {
@@ -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);
diff --git a/tests/ui/const-generics/gca/const-reference-to-constructor.rs b/tests/ui/const-generics/gca/const-reference-to-constructor.rs
new file mode 100644
index 0000000000000..bafaf9f532545
--- /dev/null
+++ b/tests/ui/const-generics/gca/const-reference-to-constructor.rs
@@ -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() {}