"Everywhere"-style proposals

Summary

Everywhere-style proposals have a keyword that represents "some set of effects". This keyword is used consistently...

on the trait, to indicate that it may contain effect-generic methods
on functions that are generic over effects
in an impl and in trait bounds, to indicate the effects of the methods defined in the trait

Question mark:

When you call a function that is effect-generic, do you need to acknowledge that?

"const and async should feel the same". They are more similar than they are different -- const lets you work in const blocks, async in async blocks. Users will expect to be able to sprinkle const/async/await in roughly the right places and have things work.
- Just as we support trait Foo { async fn foo() } we therefore support trait Foo { const fn foo() }.
const-is-const
- when you say that something is const it means you can use it in a const block
but we want a syntax that COULD be just about const
- just in case we never go further
you should be able to declare a maybe-const function without understanding effects
the most common pattern will be X Trait where all fns become X
every trait in libstd that becomes a "const trait" will want to be an "async trait" too
- and for the rest, it won't hurt them