In case the wording tripped anyone, generators (blocks and functions) have been available for a while as an unstable feature.

This works (playground):

#![feature(gen_blocks)]

gen fn gfn() -> i32 {
    for i in 1..=10 {
        yield i;
    }
}

fn gblock() -> impl Iterator<Item = i32> {
    gen {
        for i in 1..=10 {
            yield i;
        }
    }
}

fn main() {
    for i in gfn() {
        println!("{i} from gfn()");
    }
    for i in gblock() {
        println!("{i} from gblock()");
    }
}

Note that the block-in-fn version works better at this moment (from a developer's PoV) because rust-analyzer currently treats gfn() as an i32 value. But the block-in-fn pattern works perfectly already.