Address other review comments

Author: odersky

compiler/src/dotty/tools/dotc/core/Symbols.scala

@@ -655,9 +655,6 @@ object Symbols {
 
     /** The position of this symbol, or NoSpan if the symbol was not loaded
      *  from source or from TASTY. This is always a zero-extent position.
-     *
-     *  NOTE: If the symbol was not loaded from the current compilation unit,
-     *  the implicit conversion `sourcePos` will return the wrong result, careful!
      */
     final def span: Span = if (coord.isSpan) coord.toSpan else NoSpan
 

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

@@ -228,7 +228,9 @@ Standard Section: "Positions" Assoc*
                                             // offset_Deltas give difference of start/end offset wrt to the
                                             // same offset in the previously recorded node (or 0 for the first recorded node)
   Delta         = Int                       // Difference between consecutive offsets,
-  SOURCE        = 4                         // Impossible as header
+  SOURCE        = 4                         // Impossible as header, since addr_Delta = 0 implies that we refer to the
+                                            // same treeas the previous one, but then hasStartDiff = 1 implies that
+                                            // the tree's range starts later than the range of itself.
 
 All elements of a position section are serialized as Ints
 

compiler/src/dotty/tools/dotc/util/SourceFile.scala

@@ -190,7 +190,7 @@ class SourceFile(val file: AbstractFile, computeContent: => Array[Char]) extends
   }
 }
 object SourceFile {
-  implicit def eqSurce: Eq[SourceFile, SourceFile] = Eq
+  implicit def eqSource: Eq[SourceFile, SourceFile] = Eq
 
   implicit def fromContext(implicit ctx: Context): SourceFile = ctx.source
 
@@ -202,6 +202,8 @@ object SourceFile {
 
   private final val ChunkSizeLog = 10
   private final val ChunkSize = 1 << ChunkSizeLog
+
+  // These two vars are sharable because they're only used in the synchronized block in newChunk
   @sharable private var chunks: Int = 0
   @sharable private var sourceOfChunk: Array[SourceFile] = new Array[SourceFile](2000)
 }