Fix issues with attaching doc comments in parser

Author: abgruszecki

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

@@ -190,11 +190,7 @@ object Scanners {
     private 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 delimiting whitespace we don't count it, since
-          // it seems not to affect positions in source
-          nextPos - 1
+        case ' ' | '\t' | CR | LF | FF => nextPos
         case _ => lookahead.charOffset - 1
       }
       docstringMap = docstringMap + (nextPos -> comment)
@@ -854,6 +850,9 @@ object Scanners {
 
           if (comment.isDocComment)
             addComment(comment)
+          else
+            // "forward" doc comments over normal ones
+            getDocComment(start).foreach(addComment)
         }
 
         true

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

@@ -474,6 +474,37 @@ class DocstringTests extends DocstringTest {
     }
   }
 
+
+  @Test def overNL = {
+    val source =
+      """
+      |/** Class1 */
+      |
+      |class Class1
+      """.stripMargin
+
+    import dotty.tools.dotc.ast.untpd._
+    checkFrontend(source) {
+      case p @ PackageDef(_, Seq(c: TypeDef)) =>
+        checkDocString(c.rawComment.map(_.raw), "/** Class1 */")
+    }
+  }
+
+  @Test def overComment = {
+    val source =
+      """
+      |/** Class1 */
+      |// foo
+      |class Class1
+      """.stripMargin
+
+    import dotty.tools.dotc.ast.untpd._
+    checkFrontend(source) {
+      case p @ PackageDef(_, Seq(c: TypeDef)) =>
+        checkDocString(c.rawComment.map(_.raw), "/** Class1 */")
+    }
+  }
+
   @Test def withAnnotation = {
     val source =
       """
@@ -489,6 +520,22 @@ class DocstringTests extends DocstringTest {
     }
   }
 
+  @Test def withAnnotationOverComment = {
+    val source =
+      """
+      |/** Class1 */
+      |// foo
+      |@SerialVersionUID(1)
+      |class Class1
+      """.stripMargin
+
+    import dotty.tools.dotc.ast.untpd._
+    checkFrontend(source) {
+      case p @ PackageDef(_, Seq(c: TypeDef)) =>
+        checkDocString(c.rawComment.map(_.raw), "/** Class1 */")
+    }
+  }
+
   @Test def nestedComment = {
     val source =
       """

scala3doc-testcases/src/tests/tests.scala

@@ -210,3 +210,11 @@ class Methods:
  def primitives(a: Int, b: Double, c: Short): Byte = 0
  def strings(a: String): String = ""
  def arrays(a: Array[String], b: Array[Int]): Array[Double] = ???
+
+/** @define foo O's foo.
+  */
+object O:
+
+  /** This is foo: $foo
+    */
+  def method(s: String) = s