➜  ~ scala -Yrangepos
Welcome to Scala 2.13.3 (OpenJDK 64-Bit Server VM, Java 14.0.1).
Type in expressions for evaluation. Or try :help.

scala> :power
Power mode enabled. :phase is at typer.
import scala.tools.nsc._, intp.global._, definitions._
Try :help or completions for vals._ and power._

scala> object Other { var x: Int = _; var y: Int = 42 }
object Other

scala> val trees = lastRequest.trees
val trees: List[$r.intp.global.Tree] =
List(<stable> object Other extends scala.AnyRef {
  def <init>(): Other.type = {
    super.<init>();
    ()
  };
  private[this] var x: Int = _;
  private[this] var y: Int = 42
})

scala> val List(x, y) = trees.flatMap(_.collect { case vd: ValDef => vd } ).takeRight(2)
val x: $r.intp.global.ValDef = private[this] var x: Int = _
val y: $r.intp.global.ValDef = private[this] var y: Int = 42

scala> y.pos.source.content(y.pos.end)
val res0: Char =

scala> y.pos.source.content(y.pos.end - 1)
val res1: Char = 2

scala> y.pos.source.content.slice(y.pos.start, y.pos.end)
val res2: Array[Char] = Array(v, a, r,  , y, :,  , I, n, t,  , =,  , 4, 2)

scala> new String(y.pos.source.content(y.pos.start, y.pos.end))
                                                          ^
       error: too many arguments (found 2, expected 1) for method apply: (i: Int): Char in class Array

scala> new String(y.pos.source.content.slice(y.pos.start, y.pos.end)
     |
     | )
     |
val res4: String = var y: Int = 42

scala> new String(y.pos.source.content.slice(y.pos.start, y.pos.end))
val res5: String = var y: Int = 42

scala> new String(x.pos.source.content.slice(y.pos.start, y.pos.end))
val res6: String = var y: Int = 42

scala> new String(x.pos.source.content.slice(x.pos.start, x.pos.end))
val res7: String = var x: Int

scala>  // BUG: Parser doesn't include `= _` in the range position of the ValDef!

scala> val scanner = newUnitScanner(new CompilationUnit(x.pos.source))
val scanner: $r.intp.global.syntaxAnalyzer.UnitScanner = '<-3>'

scala> scanner.ch = ' '; scanner.lastOffset = x.pos.end; scanner.offset = scanner.lastOffset + 1; scanner.charOffset = scanner.offset
// mutated scanner.ch
// mutated scanner.lastOffset
// mutated scanner.offset
// mutated scanner.charOffset

scala> scanner.nextToken(); val token = scanner.token
val token: $r.intp.global.syntaxAnalyzer.Token = 124

scala> Predef.assert(token == scala.tools.nsc.ast.parser.Tokens.EQUALS)

scala> scanner.nextToken(); val token = scanner.token
val token: $r.intp.global.syntaxAnalyzer.Token = 131

scala> Predef.assert(token == scala.tools.nsc.ast.parser.Tokens.USCORE)

scala> val realEnd = scanner.offset
val realEnd: $r.intp.global.syntaxAnalyzer.Offset = 28

scala> new String(x.pos.source.content.slice(x.pos.start, realEnd + 1))
val res11: String = var x: Int = _

scala> scanner.lastOffset
val res13: $r.intp.global.syntaxAnalyzer.Offset = 27

scala> scanner.offset
val res14: $r.intp.global.syntaxAnalyzer.Offset = 28


scala> new String(x.pos.source.content.slice(scanner.lastOffset + 1, scanner.offset + 1))
val res18: String = _