fix: handle interpolations without spaces and $$ in interpolated strings

[johannescoetzee]

The Scala syntax summary doesn't describe the $identifier-type interpolations in interpolated/processed strings correctly. While a$b_<operator_chars> is a valid identifier name, in the interpolated string s"$a$b_<operator_chars>, this is actually treated as two identifier interpolations $a and $b_, followed by the string part <operator_chars>.

To fix this, I've added a new rule, _interpolation_identifier to describe identifiers in simple interpolations that matches the regex /[A-Za-z_][A-Z_a-z0-9]/; instead of the full regex in _alpha_identifier. This does mean that queries relating to interpolated strings will need to be updated, but the changes to the queries in this repo are minimal. I've aliased the rule to $.identifier instead, so this will work without query changes.

This also includes a smaller change to handle $$ patterns in interpolated strings (which evaluate to just $) without errors. These don't appear in the tree, similar to regular escape sequences.

[eed3si9n]

Thanks for the contribution @johannescoetzee!

Could you provide some highlighting tests under here plz?

tree-sitter-scala/test/highlight/basics.scala

Lines 80 to 81 in 8062487

	val hello2 = c"some $meth"
	// ^method

[johannescoetzee]

@eed3si9n Done! I think the added test covers everything, but please let me know if I should add more.

[eed3si9n]

Thanks @johannescoetzee!

[eed3si9n]

Note Different editors maintain their own queries for tree-sitter-scala (#283), so:

1. after this lands, we need to propagate the new highlight queries to different repos to take effect
2. however, since this adds a new token interpolation_identifier, if the end user somehow gets the updated queries but not the updated tree-sitter-scala, it may crash their editor?

[johannescoetzee]

however, since this adds a new token interpolation_identifier, if the end user somehow gets the updated queries but not the updated tree-sitter-scala, it may crash their editor?

There are 2 potential crashes when updating tree-sitter-scala and the queries:

1. If the queries are updated first, tree-sitter will crash on the unknown token.
2. If tree-sitter-scala is updated first, then at least nvim-treesitter crashes since (interpolation (identifier)) is no longer a possible pattern.

[eed3si9n]

If tree-sitter-scala is updated first, then at least nvim-treesitter crashes since (interpolation (identifier)) is no longer a possible pattern.

Could we somehow prevent this by creating a dummy token that can return (interpolation (identifier))? By nature of the tree-sitter, the parser becomes available immediately when the *.c is checked into the master branch.

[johannescoetzee]

It turns out it's possible to alias rules, so I've pushed a change to alias $._interpolation_identifier to $.identifier. This means queries won't have to be updated at all.

[johannescoetzee]

@eed3si9n I realised this morning that this doesn't handle the $" dollar escape, so I've updated the dollar_escape rule to include that case. To confirm that it's valid, I tested both scala 2 and 3 (results only shown for scala 3)

❯ scala
Welcome to Scala 3.3.0 (19.0.2, Java OpenJDK 64-Bit Server VM).
Type in expressions for evaluation. Or try :help.
                                                                                                                                                               
scala> val a = 2
val a: Int = 2
                                                                                                                                                               
scala> s"$"$a"
val res0: String = "2