Fixes #5169 Added ability to highlight comments in repl

Author: mrveera

compiler/src/dotty/tools/dotc/parsing/Scanners.scala

@@ -177,6 +177,12 @@ object Scanners {
     /** All doc comments kept by their end position in a `Map` */
     private[this] var docstringMap: SortedMap[Int, Comment] = SortedMap.empty
 
+    /* A Buffer for comment positions */
+    private[this] val commentPosBuf = new mutable.ListBuffer[Position]
+
+    /** Return a list of all the comment positions */
+    def commentPositions: List[Position] = commentPosBuf.toList
+
     private[this] def addComment(comment: Comment): Unit = {
       val lookahead = lookaheadReader()
       def nextPos: Int = (lookahead.getc(): @switch) match {
@@ -616,6 +622,7 @@ object Scanners {
         if (keepComments) {
           val pos = Position(start, charOffset - 1, start)
           val comment = Comment(pos, flushBuf(commentBuf))
+          commentPosBuf += pos
 
           if (comment.isDocComment) {
             addComment(comment)

compiler/src/dotty/tools/dotc/printing/SyntaxHighlighting.scala

@@ -81,6 +81,9 @@ object SyntaxHighlighting {
         }
       }
 
+      for (pos <- scanner.commentPositions)
+        highlightPosition(pos, CommentColor)
+
       object TreeHighlighter extends untpd.UntypedTreeTraverser {
         import untpd._
 

compiler/src/dotty/tools/repl/ReplDriver.scala

@@ -282,14 +282,7 @@ class ReplDriver(settings: Array[String],
           x.symbol
       }
       .foreach { sym =>
-        // FIXME syntax highlighting on comment is currently not working
-        // out.println(SyntaxHighlighting.highlight("// defined " + sym.showUser))
-        val message = "// defined " + sym.showUser
-        if (ctx.settings.color.value != "never") {
-          println(SyntaxHighlighting.CommentColor + message + SyntaxHighlighting.NoColor)
-        } else {
-          println(message)
-        }
+        out.println(SyntaxHighlighting.highlight("// defined " + sym.showUser))
       }
 
 

compiler/test/dotty/tools/dotc/printing/SyntaxHighlightingTests.scala

@@ -28,7 +28,6 @@ class SyntaxHighlightingTests extends DottyTest {
   }
 
   @Test
-  @Ignore("Comments are currently not supported")
   def comments = {
     test("// a", "<C|// a>")
     test("/** a */", "<C|/** a */>")