[dmd-beta] dmd 2.064 beta take 2

[Kenji Hara]

> I can accept the consistency argument against the existing behaviour.
> However, I cannot imagine a scenario where this new behaviour would be
desirable. Are there any use cases?

import std.typecons;
void main()
{
    alias Typedef!(immutable int, 1) MyInt;
    MyInt x;  // did not work witn 2.062 and earlier
}

In D2, 'immutabe' and 'const' are type qualifier, and it should not have
"manifest constant" meaning. That is completely different from the 'const'
in D1. Yes' this would be a big change for someone, because it was the long
term bug bug FROM THE BEGINNING OF D2. We must fix the bug AS FAR AS
POSSIBLE FAST. It's a time now.

Kenji Hara


2013/5/15 Don Clugston <dclugston at gmail.com>

> On 15 May 2013 13:54, Kenji Hara <k.hara.pg at gmail.com> wrote:
>
>> 2013/5/15 Don Clugston <dclugston at gmail.com>
>>
>>> This absolutely must not be released in this form.
>>> This has a silent, massive breaking change --
>>> struct  S { const int x = 7; }
>>> Previously, x was just a manifest constant. Now, S now has an int inside
>>> every instance.
>>> It's OK to turn that into an error. It's not OK to silently change the
>>> meaning of existing code.
>>> Especially in such a radical manner.
>>>
>>
>> It will be properly documented at the top of the language changes.
>>
>> https://github.com/D-Programming-Language/d-programming-language.org/pull/303/files#L0R60
>>
>> Certainly it will change object layout silently. But semantic meaning
>> would not be changed in most cases,
>>
>
> Sorry, but that is absolute rubbish.
> (1) Any existing instance of this silently introduces a *severe*
> performance bug.
> (2) Any storage of this struct silently fails.
>
> For example, for us, we serialize objects and store them in a database.
> This now fails because they are the wrong size.
>
> I can accept the consistency argument against the existing behaviour.
> However, I cannot imagine a scenario where this new behaviour would be
> desirable. Are there any use cases?
>
>
>  So just once full-recompilation would be necessary.
>>
>
> No, this is wrong. Every existing instance must be changed. And there is
> no way to find them.
>
> Seriously, this is one of the most breaking changes I can ever remember in
> the history of D.
>
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