On 2010-12-01 06:17:24 -0500, Jonathan M Davis <[email protected]> said:
I proposed the following a while ago. First allow the class reference
to (optionally) be made explicit:
C a; // mutable reference to mutable class
C ref b; // mutable reference to mutable class
And now you can apply tail-const to it:
const(C)ref c; // mutable reference to const class
const(C ref) d; // const reference to const class
const(C) e; // const reference to const class
The real issue is not syntax but getting it into the compiler.
Apparently, there
are difficulties in implementing tail const in the compiler which made
Walter give
up on it in the past. It should be doable, but Walter is totally sick of the
issue and doesn't want to put the time in to do it - he has plenty on his plate
as it is. So, if it's going to be done, someone else has to step up to
the plate
and do it. And with the general lack of dmd developers, that hasn't
happened. No
one thus far has had both the inclination and the time.
Well... I just took a quick look at the problem from inside the
compiler. The issue is this: the compiler has a type hierarchy, and
TypeClass is one type in it. There is no separate type for a class
reference, it just uses TypeClass do designate a class reference, which
means that if your TypeClass has the const or immutable modifier, so
does your reference. So either we create a TypeClassRef to designate
the reference, or we add additional flags to TypeClass for the
reference's modifier; in either case many parts of the semantic
analysis has to be revised to take this into account.
--
Michel Fortin
[email protected]
http://michelf.com/
