First Draft: Static Single Assignment

[Walter Bright]

Ironically, C++ head const is routinely used "as if" it was transitive const (as 
C++ has no way to specify transitive const). In my experience with C++ (and C), 
types that are legitimately "pointer to const pointer to pointer to int" are 
extremely rate.

This is a giant hole in C++'s type system.

Some C++ programmers make use of this to create "logical const" objects, where 
they pretend it is constant when it isn't. It is used for self-initializing 
objects. There are better ways to do this, though. And lying to the user is not 
a good strategy.

It isn't a good idea for D to adopt this.