Final by default?

[Walter Bright]

On 3/12/2014 6:18 PM, Chris Williams wrote:
> On Thursday, 13 March 2014 at 00:48:15 UTC, Walter Bright wrote:
>> On 3/12/2014 5:18 PM, Andrei Alexandrescu wrote:
>>> We are opposed to having compiler flags define language semantics.
>>
>> Yeah, that's one of those things that always seems like a reasonable idea, but
>> experience with it isn't happy.
>
> I would imagine that the reasons for this goal are 1) to keep the compiler and
> language sane, and 2) insufficient personel to maintain legacy variants.

Maybe surprisingly, it isn't either.

It's because every one of those switches splits the language into two languages. 
8 switches means 256 languages. When you're a library vendor, which of those 256 
languages are you writing for? What happens when you mix code for language #63 
with language #121? It's a nightmare - confusing to people trying to understand 
it, and frustrating for those who do.

The combinatorics alone are daunting - 256 times through the test suite. You 
have to add introspection so the program can tell which language it is today.

The punishment goes on and on.