Throw exception on type error in JsonDeserializer

[Maxxen]

Found by @Wang-Ji20 in #6919

[carlopi]

As mentioned live, there is an attribute [[noreturn]] that could be used to decorate the function, basically to add a consistency check / clarify expectations to whoever passes by.

Looking around the codebase it's already in use in a couple of places, so I guess it has to be supported.

[Mytherin]

Thanks for the PR! LGTM - but it seems this breaks one of the existing tests.

[Wang-Ji20]

That's caused by the type check during json deserialization.
seems when the number is positive, 3 in this case, the number is recognized as unsigned number, rather than signed integer. so the test case failed.

[Maxxen]

Ill continue with this once I pick up the serialization work again next week.

[Maxxen]

@taniabogatsch This also now fixes the ugly (void)field_id in the JsonDeserializer

[taniabogatsch]

Ah, that's a neat solution!