So the initial implementation doesn't allow any inputs/outputs besides the tokenstreams, but some proc macros do access the filesystem. There's definitely more

So the initial implementation doesn't allow any inputs/outputs besides the tokenstreams, but some proc macros do access the filesystem. There's definitely more exploration to be done both with proc macros, and the general build system (which allows execution of arbitrary rust code as well, but which tends to touch the file system a lot more). This definitely seems like a good starting point for adding security to the build system.