comment tweak

Author: rintaro

Sources/SwiftSyntax/RawSyntax.swift

@@ -24,10 +24,17 @@ internal struct RawSyntaxData {
   /// Token with lazy trivia parsing.
   ///
   /// The RawSyntax's `arena` must have a valid trivia parsing function to
-  /// lazily materialize the leading/trailing trivia.
+  /// lazily materialize the leading/trailing trivia pieces.
   struct ParsedToken {
     var tokenKind: RawTokenKind
+
+    /// Whole of this token including leading/trailing trivia.
     var wholeText: SyntaxText
+
+    /// Range of the actual token’s text.
+    ///
+    /// Text in `wholeText` before `textRange.lowerBound` is leading trivia and
+    /// after `textRange.upperBound` is trailing trivia.
     var textRange: Range<SyntaxText.Index>
   }