dmd 2.063 beta 5

[Don]

On Thursday, 23 May 2013 at 10:17:00 UTC, Peter Alexander wrote:
> On Thursday, 23 May 2013 at 09:05:02 UTC, Don wrote:
>> This means that the const variable x has been initialized 
>> TWICE!
>
> That's no different from non-const members.

It's perfectly OK to modify a non-const member as many times as 
you like. That doesn't cause confusion.

> struct Foo { int x = 1; }
> Foo f = Foo(2); // f.x is 2
>
> The initialiser is a default value if you don't provide one in 
> the constructor. If you don't mark a variable as static then it 
> is not static and needs to be initialised like any other member 
> variable.

What gives you that idea? It's listed as an initializer in the 
spec.
It's implemented as an initializer in the compiler.


>> This new behaviour is counter-intuitive and introduces a 
>> horrible inconsistency.
>
> It is exactly what happens in C++ and causes no confusion there.

I don't think it's legal in C++:

struct S
{
   const int x = 5;
};

w.cpp:4:17: error: ISO C++ forbids initialization of member ‘x’ 
[-fpermissive]


>> This is totally different to what happens with module 
>> constructors (you get a compile error if you try to set a 
>> const global if it already has an initializer).
>
> In structs/classes, it is not an initialiser, it is a default 
> value in case you don't provide a different value.
>
>
>> As far as I can tell, this new feature exists only to create 
>> bugs. No use cases for it have been given. I cannot imagine a 
>> case where using this feature would not be a bug.
>
> The use case is simple: to allow non-static const member 
> variables.

Not correct. You've always been able to have non-static const 
member variables, as long as they have no initializer.

What this feature does, is allow you to add an initializer which 
is ignored.