Fix docs and typo

Author: nicolasstucki

compiler/src/dotty/tools/dotc/core/tasty/PositionPickler.scala

@@ -34,7 +34,7 @@ class PositionPickler(
 
   def picklePositions(source: SourceFile, roots: List[Tree], warnings: mutable.ListBuffer[String]): Unit = {
     /** Pickle the number of lines followed by the length of each line */
-    def pickleLineOffsetts(): Unit = {
+    def pickleLineOffsets(): Unit = {
       val content = source.content()
       buf.writeInt(content.count(_ == '\n') + 1) // number of lines
       var lastIndex = content.indexOf('\n', 0)
@@ -45,7 +45,7 @@ class PositionPickler(
         buf.writeInt(end - lastIndex - 1) // size of the next line
         lastIndex = nextIndex
     }
-    pickleLineOffsetts()
+    pickleLineOffsets()
 
     var lastIndex = 0
     var lastSpan = Span(0, 0)

tasty/src/dotty/tools/tasty/TastyFormat.scala

@@ -230,7 +230,7 @@ Note: Tree tags are grouped into 5 categories that determine what follows, and t
 
 Standard-Section: "Positions" LinesSizes Assoc*
 
-  LinesSizes    = Int Int*                 // Number of lines followed by the size of each line not counting the trailing `\n`
+  LinesSizes    = Nat Nat*                 // Number of lines followed by the size of each line not counting the trailing `\n`
 
   Assoc         = Header offset_Delta? offset_Delta? point_Delta?
                 | SOURCE nameref_Int