On Sat, 26 Jun 2010 20:19:44 -0400, Michal Minich
<michal.min...@gmail.com> wrote:
On Sun, 27 Jun 2010 09:36:04 +0930, Justin Johansson wrote:
immutable class Foo
{
static private Foo instance;
static this() { // line 9
instance = new Foo;
}
static Foo opCall() { // line 13
return instance;
}
}
test.d(9): Error: function test.Foo._staticCtor2 without 'this' cannot
be const/immutable
test.d(13): Error: function test.Foo.opCall without 'this' cannot be
const/immutable
there is bug report on this subject
http://d.puremagic.com/issues/show_bug.cgi?id=3598
Your example also uses static variable, which was not considered in the
bug report. This makes things more complex to design properly, because it
seems now that one does not want static functions to be affected by
immutable attribute of class, but it should affect static data...
static variables inside an immutable class should be immutable. That was
considered in the bug report and purposefully left out.
The issue is that the compiler incorrectly labels static *functions* as
immutable which makes no sense, static functions cannot be immutable
ever. Static data can be.
BTW, you can work around this problem like this:
class Foo
{
static immutable instance; // no need to make private, it can never
change
static this() {
instance = new Foo; // not sure if this works, you may have to cast.
}
static immutable(Foo) opCall() {
return instance;
}
immutable:
// member functions
}
-Steve
