fix benches; seems good

bench/Main.hs

@@ -29,8 +29,8 @@ data X3
     | X33 Word8 (NullTerminated B.ByteString) X3
     deriving stock (Generic)
 
-instance BLen X3 where blen = blenGenericSum cDef
-instance Put  X3 where put  = putGenericSum  cDef
+instance BLen X3 where blen = blenGenericSum $ blen . nullTermCstrPfxTag
+instance Put  X3 where put  =  putGenericSum $  put . nullTermCstrPfxTag
 
 x33 :: X3
 x33 =

src/Binrep/Generic.hs

@@ -9,8 +9,7 @@ import Refined.Unsafe
 -- | Turn a constructor name into a prefix tag by adding a null terminator.
 --
 -- Not common in binary data representations, but safe and useful for debugging.
---
--- The refine force is safe under the assumption that Haskell constructor names
--- are UTF-8 with no null bytes allowed. Fairly certain that's true.
 nullTermCstrPfxTag :: String -> NullTerminated B.ByteString
 nullTermCstrPfxTag = reallyUnsafeRefine . Text.encodeUtf8 . Text.pack
+-- ^ reallyUnsafeRefine : safe assuming Haskell constructor names are UTF-8 with
+-- no null bytes allowed