silence warning for enums with only one variant

crates/fayalite-proc-macros-impl/src/hdl_enum.rs

@@ -888,6 +888,7 @@ impl ToTokens for ParsedEnum {
                         #(#sim_value_from_opaque_match_arms)*
                     }
                 }
+                #[allow(irrefutable_let_patterns)]
                 fn sim_value_clone_from_opaque(
                     &self,
                     value: &mut <Self as ::fayalite::ty::Type>::SimValue,

crates/fayalite/tests/hdl_types.rs

@@ -244,3 +244,13 @@ pub struct MyTypeWithPrivateMembersWithArg<T> {
     pub(crate) b: MyPubCrateTypeWithArg<T>,
     pub c: T,
 }
+
+#[hdl(outline_generated)]
+pub enum EnumWithOnlyOneVariant {
+    A,
+}
+
+#[hdl(outline_generated)]
+pub enum EnumWithOnlyOneVariant2<T> {
+    A(T),
+}