Explcit impure function attribute

[Richard (Rikki) Andrew Cattermole]

On 27/06/2024 5:35 AM, Quirin Schroll wrote:
> On Monday, 24 June 2024 at 16:47:06 UTC, Richard (Rikki) Andrew 
> Cattermole wrote:
>> On 25/06/2024 4:38 AM, Quirin Schroll wrote:
>>> Make `@impure` a compiler-recognized AtAttribute. This has the 
>>> downside of being asymmetric: `pure` has no `@`, but its inverse 
>>> `@impure` would have it.
>>
>> So add it.
>>
>> Deprecate, then remove without ``@`` in newer editions.
> 
> So, you favor (effectively) adding `@impure`, and adding `@pure` as an 
> alias for `pure`, while deprecating `pure`. Did I understand that 
> correctly?

Yes.

Get all the attributes to be the same, clean it up!

>> Making all attributes consistent with using ``@`` is a good thing.
> 
> There are still `throw` and `nothrow`. If I had to lay a bet on it, I’d 
> say they don’t go anywhere. The value of replacing _them_ with something 
> with `@` is negligible.

They'll both be going away at some point in favor of a throws set, to 
allow for value type exceptions.

No other way to get the sumtype style exceptions working and there is 
significant desire by core developers for it.