Simplification of @trusted

[Ola Fosheim Grøstad]

On Wednesday, 23 June 2021 at 06:25:08 UTC, Andrei Alexandrescu 
wrote:
> Non-sequitur. The problem is there is no @system/@trusted/@safe 
> troika for pure. It's either pure or not, no way to express (as 
> is needed in key parts) "this function shall be trusted to be 
> pure".

Then you need to list explicitly what `pure` means in terms of 
allowed optimizations. Otherwise you'll end up with something 
that is too weak to be useful for compiler authors.