pfr VS nanoserde

This single feature opens a world of new possiblities. For example, it makes implementing "getting the number of fields" trivial. Furthrmore, and much more importantly, it enables turning a struct into a tuple. Currently, this can only be done by enumerating cases (therefore it's not fully generic), as with Boost PFR. By the way, PFR greatly simplifies our codebases, especially for parts with serialization and/or reflection.

The code is relatively short and can be groked with a few coffees: https://github.com/boostorg/pfr/tree/develop/include/boost/pfr ; if you're using C++17 it uses a binary search (https://github.com/boostorg/pfr/blob/develop/include/boost/pfr/detail/fields_count.hpp) to count the number of fields in a struct, by starting by the observation that a likely majorant on the number of fields in a struct is sizeof(the struct) * CHAR_BIT, assuming not too many [[no_unique_address]] tomfooleries. Then once this count is known it's possible to simply map them as a tuple through sheer brute force and destructuring: https://github.com/boostorg/pfr/blob/develop/include/boost/pfr/detail/core17_generated.hpp

I wonder if the c++ approach of boost.pfr would be portable to rust ? It allows reflection on aggregates without needing to annotate anything: https://github.com/boostorg/pfr

It is an 'interesting' meta-programming problem though (wasted many weeks on it myself, fixed a small gcc bug - a 'uniform init' edge case and filed an issue with magic_get Reflecting array members of aggregate structs).

what do you think of the parser in nanoserde? https://github.com/not-fl3/nanoserde/blob/master/derive/src/parse.rs

Yeah proc macros have a massive hole in their user experience. Nobody actually wants to use them without syn + quote functionality, so the majority of people just pay the compile time cost of syn/quote/procmacro2. But then a subset of people can't afford to pay the compile time cost, so they either: 1. Don't use them. And remove all of their deps that use them ... which is generally a lot. 2. Hand-manage the TokenStream (which is very much not fun). Macroquad doesn't want syn + quote in their tree because they care _deeply about compile times, so they opted to re-implement serde. Serde is the crowned jewel of the rust ecosystem. Someone feeling unable to use it is a massive failure of the system.