To further explain what I mean:
struct A if (!is(this == immutable) && !is(this == shared))
{
}shared a = A() // error auto a = A() // ok immutable a = A() // error const a = A() // ok Fake syntax above of course.I was thinking about this because I read a few posts about const, and approaching it via allowing an object to define a head mutable version of itself (see post in general forum by Simon for details [1])
And there're few constructs like RefCounted which don't make sense with an immutable qualifier.
And then there're situations where a mutable version does not make sense (I think this would be a much bigger application), ie: handles, resource identifiers, application configuration details, etc.
[1] https://forum.dlang.org/thread/cpxfgdmklgusodqou...@forum.dlang.org
