Fix incorrect spans assigned in some cases

[jadenPete]

I've observed tasty-query occasionally reading the wrong position for certain trees.

Consider this example:

class InferredTypeArgs {
  def id[T](x: T): T = x

  val a = id(42)
}

Here, the compiler inserts an inferred type annotation, so in TASTy, the ValDef statement looks like this:

val a: scala.Int = id[scala.Int](42)

The scala.Int type annotation should have a zero-width span because it doesn't exist in the source text, but tasty-query incorrectly reads its span as the same as that of id(42). Also, the scala.Int type argument should have the same span as the function it's applied to (id), but it's instead the same as that of the entire function call (id(42)).

This PR fixes both of these issues. I've verified that the tests I added fail before the fix, and succeed after the fix.

[sjrd]

Very nice. Thank you. I have some comments.

[sjrd]

I find it suspicious that this item disappears, instead of being fixed. Same thing below. Could you explain why that happens?

[jadenPete]

I think it's because of the !pos.isZeroExtent check here:
https://github.com/scalacenter/tasty-query/blob/main/tasty-query/shared/src/test/scala/tastyquery/PositionSuite.scala#L27

The type has no bounds, so the returned string is empty. If I remove that check, I get this error:

==> X tastyquery.PositionSuite.type-definition-tree-1  0.011s munit.ComparisonFailException: /home/jpeterson/lucid/tasty-query/tasty-query/shared/src/test/scala/tastyquery/PositionSuite.scala:404
403:      )
404:    )
405:  }
values are not the same
=> Obtained
List(
  "Int",
  "",
  ">: Null <: Product",
  "Int",
  "Null <: Product = Null",
  "Null <: Product"
)
=> Diff (- obtained, + expected)
   "Int",
-  "",
   ">: Null <: Product",
    at munit.Assertions.failComparison(Assertions.scala:278)

[sjrd]

Ah that makes sense.