It just makes programs ambigious when reading. The amount of typing you save is the amount of type information the reader loses. It's okay if there's just one i

It just makes programs ambigious when reading. The amount of typing you save is the amount of type information the reader loses. It's okay if there's just one instance of IsString you're actually using, but if you're using few of them in the same module it turns out to not be satisfactory for my tastes.