Generic instance of Binary is broken for types with 256 constructors #175
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The current implementation uses the output type to store the number of constructors (e.g. parameter size of putSum). This will fail if we try to serialize a type with 256 constructors, which can be encoded in Word8 but its size does not. This is slightly inefficient: We could use Word8 if getSum and putSum were implemented differently (which would make them more complicated and probably slower).
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Word8 is used to store the constructor. While this is big enough to store the constructors, the size parameter of getSum and putSum will wrap to zero. We get this error when round-tripping any value of such a type:
This PR applies the quick&dirty fix: Use Word16 for such types. This is less space-efficient than using Word8. Alternatively, we could change getSum and putSum to cope with this edge case.