Support destination pseudo-scopes

[pokey]

The problem

Consider the following code

const aaa = 0;

In this case, there is no type. However, we want the following to work:

• "change type" from within the statement should insert a : after the aaa and leave your cursor after the :
• "bring bat to type air" should insert a : after the aaa, followed by "bat"

The solution

Query language update

• In our query language, support @myScopeType.destination

• Could be used as follows:

  (
    (lexical_declaration
       (variable_declarator
          name: (_) @type.destination.endOf
          !type
       )
    )
    (#leading-insertion-delimiter! @type.destination ": ")
  )

How to handle these queries

The naive approach is to create a stub target that only has a getDestination method and throws on everything else. Unfortunately the problem is that this would break the following:

function aaa(): void {
    const bbb = 0;
}

If you say "copy type bat", you'll get an error, because it will get trapped in the pseudo-scope. Maybe that's fine because it could be confusing to have "copy type bat" and "change type bat" refer to different scopes (the latter is legitimately a destination pseudo-scope that allows adding a type to bbb)

[pokey]

update from meet-up, taking "type" as our running example:

• "drink", "pour", and "change" all do the same thing when you have no type
• "drink" and "pour" don't work when you have a type (unless you're in a language which suppers multiple types)
• If you say "take type" from within something that has no type but could (ie has a destination pseudo-scope), it is an error. This is useful when combined with Filter / forgiving adverbs #1015
• for something that can have more than one (eg "name" in scm), then "drink" and "pour" work
• Add (#prefix-insertion-delimiter! ": ") predicate
• Add (#postfix-insertion-delimiter! ": ") predicate
• Rename (#insertion-delimiter!) to #infix-insertion-delimiter?
• if no infix, then we don't support "drink" and "pour" when there is already 1

[pokey]

Note that the interaction with #1015 is a bit nontrivial because for eg "pour soft type" or "bring air to soft type", we actually want "soft" to apply to the conversion to a destination rather than to the modifier after it. Not sure how to distinguish that from wanting it to apply to the modifier after it 🤔

[pokey]

There's also an interesting interaction with the pattern we're proposing in #1742. For the case of "name" in the .scm language, which we're using to refer to @foo captures, then we get the captures as multiple targets when you're not directly in one of them. For example:

(aaa) @bbb @ccc

In this case, if you say "name air", you'll get bbb and ccc. The problem is that if you now have something like the following:

(aaa) @bbb @ccc
(ddd) @eee

If you say "bring name drum to air", you'll get

(aaa) @eee @eee
(ddd) @eee

Which is obviously not desirable. In this case, it seems like the destination "to name air" should possibly be the range bbb @ccc, rather than as separate targets. Or we could just have that be the target "name air" as well.

Maybe the answer here is that for #1742 we should have them be one target that is the union of their ranges if they're adjacent? They can still use "every name" if they want them separately