Stripping away const/invariant in D 2.0

[Christian Kamm]

>> I've been trying to work this out for a few hours now, and I'm drawing a
>> blank.  In D 2.0, there doesn't appear to be any way of deriving the
>> type of T given either (const T) or (invariant T).
> 
> Use "typeof(T)". For example if T is invariant char , then typeof(T) ==
> char. typeof() kinda works like a declaration, so it removes the top
> level const/invariant.

This works for plan data like char (since const(char) really is the same
type as char, if I understand it right - there's no 'tail' that could be
const), but not for reference types:

class T {}
const(T) var;
writefln(typeid(typeof(var)));
produces
const T

However, I think templates are broken with regard to const, since:

class T {}
const(T) var;
pragma(msg, typeof(var));
errors with
consttest.d(14): Error: string expected for message, not 'const T'

and

template Foo(Q) {
  pragma(msg, Q);
}

class T {}
const(T) var;
Foo!(typeof(var));
errors with
consttest.d(7): pragma msg string expected for message, not 'T'