here all the reasons why
- the code base is in C/C++ and it is a huge code base
the effort would be enormous for not any gain at all
- there are many old issues and code patches that can be found
see Bugzilla Tamarin Graveyard, those patches use C/C++
here few examples:
- in fact just suggesting to port this huge code base to anything else shows that whoever made this suggestion is not familiar at all with the said code base
- just porting the C++ to C++ 14 standard would be a lot of work
- you would not be able to integrate with something like CrossBridge
- you would make integrating with 3rd party C/C++ libraries harder
for ex: zlib, openSSL, etc.
- from time to time Adobe does update the avmplus source code
it's rare but it did happen a couple of times and it could happen again
if the code base is ported to Rust then you can not integrate their changes
- by keeping the code C/C++ you can also "export" some native Redtamarin features to Adobe AIR with an ANE, eg. you port the C++ code to work as an ANE for the desktop and/or mobile
- Redtamarin was possible because Adobe did open source the avmplus,
they could open source other stuff in the futur and those would probably be in C/C++ too
Those are merely the technical reasons, there are also design and maybe philosophical reasons
Redtamarin provide runtimes, API, native code, libraries, tools, etc.
which in a certain way could be put in competition directly with Rust, Go, Dart, Swift, etc.
Finally, there are many things to do in an open source project like Redtamarin, this is called moving forward, porting everything to Rust would be felt like "going backward" and a waste of time, everything else would have to stop while waiting for the C++ code to be ported to Rust.
LOL not gonna happen, but feel free to fork the project and do whatever you want.