Aliasing syntax
===============

There are two types of aliasing:
1. items that alias *something*, so reads/writes need to be done in order
   with regard to external or other accesses to aliased items.
2. items that alias a specific other item. This is useful for shallow
   copy functions, for example.


Syntax for case 1:
- simply a qualifier
- this probably only makes sense when there are function pointers
  inside an object, that may modify the object.

    func f(aliased Obj a)
    func g(Thing b) -> aliased Obj   # Does it make sense at all for return values?

Syntax for case 2:
- could work similar to lifetime specifiers:

    func f(Obj a, Obj b)
        aliasing a, b
    func g(Obj a) -> Obj
        aliasing a, return

- which separator token to use?
        aliasing a, b
        aliasing a & b
        aliasing a/b
        aliasing a+b
        aliasing a b

Simplified solution
-------------------
* Disallow the "aliased" qualifier, and only use "aliasing" specifiers.
* Regarding internal aliasing:
    - Do we need to specify it at all? The struct would have aliasing
      specifiers inside it anyway.
    - If yes, which syntax to use:
        - "aliasing internal a"?
        - or specify which fields? "aliasing a.f1, a.f2"