Vim: yaf in typescript is not the same as vafy for arrow functions

[thomasheartman]

Summary

Using yaf (or daf) inside an arrow function doesn't include the function declaration (const x = ). However, vafy/vafd does.

Steps to trigger the problem:

1. Be in typescript mode
2. Define an arrow function:

const f = (x: unknown) => {
  return x
}

const g = () => (x: unknown) => {
  return x
}

3. Place cursor inside function body.
4. yaf

Actual Behavior:
yaf only yanks from the last set of arguments. Both examples above yield the following when yanked from inside the braces:

(x: unknown) => {
    return x
}

Expected Behavior:
Similarly to vaf, the entire function (including the definition etc) is used. In other words, I'd expect them to yield

const f = (x: unknown) => {
    return x
}

and

const g = () => (x: unknown) => {
    return x
}

respectively.

Maybe related, vaf also has a problem when called from the name/declaration of the function.

Using the same function f, typing vaf with the cursor somewhere in const f = yields a selection that only includes const f = (x: unknown) => {. I'd expect it to be the entire function, not just the first line.

Screenies:
vaf from the body:

vaf from the declaration

Zed Version and System Specs

Zed: v0.171.6 (Zed)
OS: macOS 14.6.1
Memory: 16 GiB
Architecture: aarch64

[ConradIrwin]

I think the proximate cause here is that we target visual line mode for the selection. We should update yank to look for the target visual mode of the object to fix this.