Support dot completion inside case branches

[Toucan4Life]

Add dot-autocomplete for case branch heads in Par completion.

either branch heads

Before, typing inside a branch head like this did not propose the valid branches:

type Stream = either {
  .end!,
  .chunk !,
}

def StreamValue : Stream = external
def Main : ! = StreamValue.case {
  .
}

Now it suggests:

• chunk()
• end!

choice branch heads

For begin case, branch-head completion now works here:

type Sequence = iterative choice {
  .close => !,
  .next => self,
}

def Main : Sequence = begin case {
  .
}

and suggests:

• close
• next

Recursive / named types

This also works when the branch set comes from a recursive or named type rather than from text already present in the current case block.

Example:

type Repeat = recursive either {
  .end!,
  .step self,
}

def RepeatValue : Repeat = external
def Main : ! = do {
RepeatValue.begin.case {
  .
}
} in !

Now it suggests:

• end!
• step()

Anything that might be missing?

My next target is to work on the description of the autocomplete, and when the todo keyword is implemented, I would like that when choosing a suggestion from the autocomplete automatically insert some code snippet. Like for the branch that this PR worked on, instead of inserting only .step(), it would insert .step() => todo.

I would also like to work on the hover tooltip; I would like that when you hover a function or a reserved keyword of par, it show an hover of the usage of that function/keyword, like in rust.

Or do you want me to work on another things for my next PR?

Also congrats on the paper :D

[faiface]

Nice, this looks good, thank you @Toucan4Life, merging!