More radical ideas about gc and reference counting

[Walter Bright via Digitalmars-d]

On 4/30/2014 11:57 PM, bearophile wrote:
> I agree the people are reluctant to add annotations, but I think it's also
> depends on the return of investment of the specific annotation. I am annotating
> all my code carefully with "pure", but the ROI of all those purity annotations
> is not great.

That's why I want to move more towards attribute inference.


> And I agree the piling of special cases is a not clean design. It's now simpler
> to ask the compiler if a certain assignment to immutable is allowed or not.
> Because I can't remember the supported cases.
 > So I suggest a more principled and visible approach at the problem of ownership
 > and uniqueness.

The "supported cases" are not random special case hacks. They are based on a 
solid principle - if the expression represents a unique reference to an object, 
then it is implicitly convertible to immutable or shared.

For example,

     new int;

Formerly, that created a pointer to a mutable int object. It could not be 
implicitly cast to a pointer to an immutable int. But we know that operator new 
returns the only pointer to what it created, so it should be convertible. This 
knowledge was simply added to the compiler.

I don't see anything unprincipled about that, or hard to understand, or hackish, 
or whatever.