I’m not a big fan of this. It feels “worse than C”. At least in C or C++, you need to #include <platform_specific.h> before using any platform specific APIs. I would rather have any platform specific APIs stuck in some sort of std::sys, which says “if you use these, your code is not guaranteed to compile everywhere”, kind of a thing… I’m not sure, though.
I want Rust code to be, by default, portable.