Fix cheeky comment in nested scope

Author: felixmulder

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

@@ -178,12 +178,21 @@ object Scanners {
     /** All doc comments kept by their end position in a `Map` */
     private[this] var docstringMap: SortedMap[Int, Comment] = SortedMap.empty
 
-    private[this] def addComment(comment: Comment): Unit =
-      docstringMap = docstringMap + (comment.pos.end -> comment)
+    private[this] def addComment(comment: Comment): Unit = {
+      val lookahead = lookaheadReader
+      def nextPos: Int = (lookahead.getc(): @switch) match {
+        case ' ' | '\t' => nextPos
+        case CR | LF | FF =>
+          // if we encounter line delimitng whitespace we don't count it, since
+          // it seems not to affect positions in source
+          nextPos - 1
+        case _ => lookahead.charOffset - 1
+      }
+      docstringMap = docstringMap + (nextPos -> comment)
+    }
 
     /** Returns the closest docstring preceding the position supplied */
-    def getDocComment(pos: Int): Option[Comment] =
-      docstringMap.to(pos).lastOption.map(_._2)
+    def getDocComment(pos: Int): Option[Comment] = docstringMap.get(pos)
 
     /** A buffer for comments */
     val commentBuf = new StringBuilder
@@ -589,10 +598,12 @@ object Scanners {
       val start = lastCharOffset
       def finishComment(): Boolean = {
         if (keepComments) {
-          val pos = Position(start, charOffset, start)
+          val pos = Position(start, charOffset - 1, start)
           val comment = Comment(pos, flushBuf(commentBuf))
 
-          if (comment.isDocComment) addComment(comment)
+          if (comment.isDocComment) {
+            addComment(comment)
+          }
         }
 
         true

compiler/test/dotty/tools/dotc/parsing/DocstringTests.scala

@@ -488,4 +488,34 @@ class DocstringTests extends DocstringTest {
         checkDocString(c.rawComment.map(_.raw), "/** Class1 */")
     }
   }
+
+  @Test def nestedComment = {
+    val source =
+      """
+      |trait T {
+      |  /** Cheeky comment */
+      |}
+      |class C
+      """.stripMargin
+
+    import dotty.tools.dotc.ast.untpd._
+    checkFrontend(source) {
+      case p @ PackageDef(_, Seq(_, c: TypeDef)) =>
+        assert(c.rawComment == None, s"class C is not supposed to have a docstring (${c.rawComment.get}) in:$source")
+    }
+  }
+
+  @Test def eofComment = {
+    val source =
+      """
+      |class C
+      |/** Cheeky comment */
+      """.stripMargin
+
+    import dotty.tools.dotc.ast.untpd._
+    checkFrontend(source) {
+      case p @ PackageDef(_, Seq(c: TypeDef)) =>
+        assert(c.rawComment == None, s"class C is not supposed to have a docstring (${c.rawComment.get}) in:$source")
+    }
+  }
 } /* End class */