fix for the issue #92464

Author: ouz-a

compiler/rustc_middle/src/ty/layout.rs

@@ -1310,7 +1310,10 @@ impl<'tcx> LayoutCx<'tcx, TyCtxt<'tcx>> {
                     },
                 };
                 let mut abi = Abi::Aggregate { sized: true };
-                if tag.value.size(dl) == size {
+
+                // Without latter check aligned enums with custom discriminant values
+                // Would result in ICE see the issue #92464 for more info
+                if tag.value.size(dl) == size || variants.iter().all(|layout| layout.is_empty()) {
                     abi = Abi::Scalar(tag);
                 } else {
                     // Try to use a ScalarPair for all tagged enums.

src/test/ui/aligned_enum_cast.rs

@@ -0,0 +1,15 @@
+// run-pass
+// allows aligned custom discriminant enums to cast into other types
+// See the issue #92464 for more info
+#[allow(dead_code)]
+#[repr(align(8))]
+enum Aligned {
+    Zero = 0,
+    One = 1,
+}
+
+fn main() {
+    let aligned = Aligned::Zero;
+    let fo = aligned as u8;
+    println!("foo {}",fo);
+}