Qualifier syntax
================

Current syntax:

    int i
    var int i
    Obj o
    var Obj o
    var ref Obj o
    var ref var Obj o
    arena Obj o

Problems:
* The distinction between re-assignable ("var ref") and modifiable ("var")
  might not be obvious for the programmer.
    - But on the other hand, there is no such distinction for e.g. the
      elementary types (int, bool, etc), enums, strings and "value" types.
* Whether arena access is given, is actually a property of the
  reference(or parameter/variable) rather than the object.
  For this reason, it would make more sense to put the arena
  qualifier on the parameter/variable.
* arena access for allocation only and arena access for performing system
  operations (such as I/O) is lumped together.


Alternative syntax 1:

    int i
    int =i
    Obj o
    var Obj o
    Obj =o
    var Obj =o

How to indicate that something is an "allocation arena"?
How to indicate that something is a "system arena"?
How to indicate that something is an arena and is modifiable?
How to indicate that something is an owned reference?
Syntax idea 1:

    Obj +o      # Allocation arena
    Obj !o      # System arena
    var Obj +o  # Allocation arena. Modifiable object
    var Obj =+o # Allocation arena, re-assignable (changeable reference). Modifiable object
    var @Obj o  # Owned allocation

    type T = struct {
        ref var Obj o
        # This ordering is a bit strange... (ref and = on opposite sides)
        ref var Obj =p
    }

    Problem 1: This isn't that intuitive either...

Syntax idea 2:

    Obj arena o
    Obj sys o
    var Obj arena o
    var Obj arena var o
    var own Obj o