This won't work because the conditionally-compiled platform-specific code is expected to not typecheck (or to use fields that do not exist, etc.) The same feat

This won't work because the conditionally-compiled platform-specific code is expected to not typecheck (or to use fields that do not exist, etc.) The same feature is also used for specializing generic containers to specific types (an idea that became famous after the resounding success of std::vector<bool>) so that for example arraylists of u8 expose a Writer but arraylists of f64 do not. Most code that is conditional on T == u8 won't typecheck if T != u8. I guess more generally these features are used for implementing fmt, json encoders and decoders, etc. None of these thing would work if code conditional on the type had to typecheck for all types.