Not all effects, but a select set which are covered by the `effect` keyword. That set could change over edition bounds. The reason for that is because we don't

Not all effects, but a select set which are covered by the `effect` keyword. That set could change over edition bounds. The reason for that is because we don't just care about maximum expressivity, we also care about ensuring good readability. It would be really bad if every function, type, and argument had to repeat `?const ?try ?async ?panic ?send ?leak ?sized` and other effects over and over and over. Having a keyword to represent a set of effects which functions are expected to be generic over seems like the better option. I do hope that in maybe 2027 or 2030 we can switch the stdlib over to const-by-default, so `const` would no longer has to be part of the effect set. But it's unlikely we'll ever want to implement "async-by-default" or "try-by-default". So there likely will always be a need to name a set of effects which functions can be generic over.