I couldn't find any information about this on the dlang web site.

What is the effect adding the immutable attribute to a class like this

immutable class MyClass { ... }

The compiler doesn't complain.
Will it add the immutable attribute to all members ?

On Thursday, 26 May 2016 at 14:12:23 UTC, chmike wrote:
> I couldn't find any information about this on the dlang web site.
>
> What is the effect adding the immutable attribute to a class like this
>
> immutable class MyClass { ... }
>
> The compiler doesn't complain.
> Will it add the immutable attribute to all members ?

auto mc = new MyClass;

typeof(mc.someFieldOrFun).stringof.writeln; says yes

and if you define opCall you need to use
auto mc = new immutable MyClass;

On Thursday, May 26, 2016 14:12:23 chmike via Digitalmars-d-learn wrote:
> I couldn't find any information about this on the dlang web site.
>
> What is the effect adding the immutable attribute to a class like this
>
> immutable class MyClass { ... }
>
> The compiler doesn't complain.
> Will it add the immutable attribute to all members ?

If you put any attribute on a class that's not specifically for a class (like abstract or final), then it will mark all of its members with that attribute, which is almost never what you want. It's equivalent to doing something like

immutable
{
    class MyClass
    {
    }
}

or

class MyClass
{
immutable:
}

- Jonathan M Davis

On Thursday, 26 May 2016 at 14:12:23 UTC, chmike wrote:
> I couldn't find any information about this on the dlang web site.
>
> What is the effect adding the immutable attribute to a class like this
>
> immutable class MyClass { ... }
>
> The compiler doesn't complain.
> Will it add the immutable attribute to all members ?

Since immutable is transitive everything in your class will be. So basically the only thing you can do is

- create a new immutable(MyClass)
- sets the instances variables in the ctor.
- calls the method (which can't do anything on the variables).

And that's all, e.g:

----
immutable class Foo
{
    int i;
    this(int i){this.i = i;}
    void method(){}
}

void main()
{
    immutable(Foo) foo = new immutable(Foo)(1);
    //foo.i = 8; // not possible since i is immutable
    Foo foo1 = cast(Foo) foo; // cast away immutable from the type.
    //foo1.method; // not pissible since method is immutable
}
----

So it's more or less useless, unless you want to wrap some variables in a class to simplify completion in the IDE or whatever other reasons.

_________________

By the way the doc for "immutable class Stuff" is here: https://dlang.org/spec/const3.html#immutable_type, it's a type constructor. "immutable" is fully part of the type.