Which language constructs could be done as a library if we accept some breaking changes?

[user1234]

On Monday, 29 November 2021 at 11:12:16 UTC, Ola Fosheim Grøstad 
wrote:
> On Sunday, 28 November 2021 at 21:01:53 UTC, Elronnd wrote:
>> On Sunday, 28 November 2021 at 20:47:28 UTC, Ola Fosheim 
>> Grøstad wrote:
>>> Which features that are currently in the language could with 
>>> some adjustments be done as a library feature?
>>>
>>> Class?
>>
>> Classes should be a language feature in any case, for 
>> performance reasons
>
> A good compiler will detect standard library features and use a 
> fast-path/optimized-path for those. So there should be no 
> performance impact.

static casts, devirtualization, are reasons for built-in classes.
Things for classes that can be done in the library are already 
done there, e.g dynamic casts.