I cannot initialize immutable class members inside a static this() constructor. Is there any reason for that?

Example:
class Test
{
    public immutable(int) x;
    static this()
    {
        x = 1; // Error: variable Test.x can only initialize const x
inside constructor
    }
}

On Mon, 21 Mar 2011 22:27:17 +0100, teo <teo.ubuntu@yahoo.com> wrote:

> I cannot initialize immutable class members inside a static this()
> constructor. Is there any reason for that?
>
> Example:
> class Test
> {
>     public immutable(int) x;
>     static this()
>     {
>         x = 1; // Error: variable Test.x can only initialize const x
> inside constructor
>     }
> }

Non-static class members require a this pointer, and thus cannot be
initialized in a static constructor. However, if that is the error
message you get, it is clearly misleading.

-- 
Simen

> On Mon, 21 Mar 2011 22:27:17 +0100, teo <teo.ubuntu@yahoo.com> wrote:
> > I cannot initialize immutable class members inside a static this() constructor. Is there any reason for that?
> > 
> > Example:
> > class Test
> > {
> > 
> >     public immutable(int) x;
> >     static this()
> >     {
> > 
> >         x = 1; // Error: variable Test.x can only initialize const x
> > 
> > inside constructor
> > 
> >     }
> > 
> > }
> 
> Non-static class members require a this pointer, and thus cannot be initialized in a static constructor. However, if that is the error message you get, it is clearly misleading.

No. Error message is essentially correct, just confusing. In this case, x is a member variable, _not_ a class/static variable. So, it must either be directly initialized

public immutable int x = 1;

or in a constructor (and in this case the constructor would have to be immutable).

public immutable int x;

this() immutable
{
    int x = 1;
}

static this() in a class is for initializing class/static variables only, so if you did

public static immutable int x;

static this()
{
    int x = 1;
}

that would work. The fact that it is immutable has nothing to do with whether it is a member variable or a class/static variable, so it has no effect on whether a normal or static constructor is used.

- Jonathan M Davis

On Mon, 21 Mar 2011 22:27:53 +0100, Simen kjaeraas wrote:

> On Mon, 21 Mar 2011 22:27:17 +0100, teo <teo.ubuntu@yahoo.com> wrote:
> 
>> I cannot initialize immutable class members inside a static this() constructor. Is there any reason for that?
>>
>> Example:
>> class Test
>> {
>>     public immutable(int) x;
>>     static this()
>>     {
>>         x = 1; // Error: variable Test.x can only initialize const x
>> inside constructor
>>     }
>> }
> 
> Non-static class members require a this pointer, and thus cannot be initialized in a static constructor. However, if that is the error message you get, it is clearly misleading.

Yes, that is the message. Thanks for the hint.