feat: unnamed union

[MatrixEditor]

New Feature: Unnamed Unions

This pull request introduces a new Unnamed field (Unnamed[TypeA, TypeB, ...]), a fixed-size, positionally-typed C-union-style field.

@struct
class Packet:
    tag: uint8_t
    payload: Unnamed[uint8_t, uint16_t, uint32_t]

p = unpack(Packet, bytes([0xAB, 0x11, 0x22, 0x33, 0x44]))

assert repr(p.payload) == "Unnamed(?, ?, ?)"
assert p.payload[0] == 0x11   # typing will automatically infer the integer type
assert p.payload._1 == 0x2211
assert p.payload[2] == 0x44332211
assert len(p.payload) == 3