Consider for IsVariant

impl/src/is_variant.rs

@@ -53,6 +53,7 @@ pub fn expand(input: &DeriveInput, trait_name: &'static str) -> Result<TokenStre
     }
 
     let imp = quote! {
+        #[allow(unreachable_code)] // omit warnings for `!` and other unreachable types
         #[automatically_derived]
         impl #imp_generics #enum_name #type_generics #where_clause {
             #(#funcs)*

tests/is_variant.rs

@@ -1,4 +1,5 @@
 #![cfg_attr(not(feature = "std"), no_std)]
+#![cfg_attr(nightly, feature(never_type))]
 #![allow(dead_code)] // some code is tested for type checking only
 
 use derive_more::IsVariant;
@@ -161,3 +162,16 @@ const _: () = {
     assert!(!ks.is_never_mind());
     assert!(ks.is_nothing_to_see_here());
 };
+
+#[cfg(nightly)]
+mod never {
+    use super::*;
+
+    #[derive(IsVariant)]
+    enum Enum {
+        Tuple(!),
+        Struct { field: ! },
+        TupleMulti(i32, !),
+        StructMulti { field: !, other: i32 },
+    }
+}