T3406.hs:11:6:
    The type variables ‘a, b’
    should be bound by the pattern signature ‘ItemColID a b’
    but are actually discarded by a type synonym
    To fix this, expand the type synonym
    [Note: I hope to lift this restriction in due course]
    In the pattern: x :: ItemColID a b
    In an equation for ‘get’:
        get (x :: ItemColID a b) = x :: ItemColID a b