Function arguments passed by reference

[cardillan]

The new variable indirection would allow to pass function arguments by reference: the caller would pass a variable name as an argument, and the function would use read or write on @this to access the variable.

However, allowing to do so has some drawbacks:

• It would introduce variable aliasing into the language, making optimizations much more difficult.
• The set of variables accessed by a function would depend on all function calls (probably a subproblem of the previous point).
• Only variables backed by a processor variable could be passed by reference. This means that e.g. external variables or array elements with non-constant indexes couldn't be passed by reference. It's not that difficult to implement the restriction, but it would introduce inconsistencies into the language.
• Accessing variables this way is costlier and would prevent some optimizations within the function, compared to existing output parameters.

Given the above points, support for passing function arguments by reference is not currently planned.