Can Dada put a value on the stack and pass any sort of mutable reference to it to a function? I don’t know the syntax, but maybe:
let x: given i32 = 42
f(x.mut)
// now x == 43
If all permission variants of a type are shallowly laid out like the raw type, then x and x.mut are literally 32-bit integers, so how does one mutate it from a function body? A special boxed i32?