-- The substitution is extended only if the variable is cloned, because
-- we *don't* need to use it to track occurrence info.
simplBinder env bndr
- | isTyVar bndr = do { let (env', tv) = substTyVarBndr env bndr
+ | isTyCoVar bndr = do { let (env', tv) = substTyVarBndr env bndr
; seqTyVar tv `seq` return (env', tv) }
| otherwise = do { let (env', id) = substIdBndr env bndr
; seqId id `seq` return (env', id) }