Fix association of docstrings based on posisition

This commit fixes errors that would've occurred in this situation:

```
/** Docstring 1 */ <- this one would've been chosen
/** Docstring 2 */
/** Docstring 3 */
class Class
```

And this situation:

```
/** Docstring 1 */
trait Trait
/** Docstring 2 */ <- this one would've been chosen
```

1 files changed, 50 insertions, 1 deletions

diff --git a/test/test/DottyDocTests.scala b/test/test/DottyDocTests.scala
index 2a60e7e7d..5161f98b8 100644
--- a/test/test/DottyDocTests.scala
+++ b/test/test/DottyDocTests.scala
@@ -53,6 +53,7 @@ trait DottyDocTest extends DottyTest { self =>
 /** Add tests to the `tests` sequence */
 object DottyDocTests extends DottyTest {
   private[this] val tests = Seq(
+    NoComment,
     SingleClassInPackage,
     MultipleOpenedOnSingleClassInPackage,
     MultipleClassesInPackage,
@@ -64,7 +65,9 @@ object DottyDocTests extends DottyTest {
     NestedClassThenOuter,
     Objects,
     ObjectsNestedClass,
-    PackageObject
+    PackageObject,
+    MultipleDocStringsBeforeEntity,
+    MultipleDocStringsBeforeAndAfter
   )
 
   def main(args: Array[String]): Unit = {
@@ -74,6 +77,16 @@ object DottyDocTests extends DottyTest {
   }
 }
 
+case object NoComment extends DottyDocTest {
+  override val source = "class Class"
+
+  import dotty.tools.dotc.ast.untpd._
+  override def assertion = {
+    case PackageDef(_, Seq(c: TypeDef)) =>
+      assert(c.rawComment == None, "Should not have a comment, mainly used for exhaustive tests")
+  }
+}
+
 case object SingleClassInPackage extends DottyDocTest {
   override val source =
     """
@@ -322,3 +335,39 @@ case object PackageObject extends DottyDocTest {
     }
   }
 }
+
+case object MultipleDocStringsBeforeEntity extends DottyDocTest {
+  override val source =
+    """
+    |/** First comment */
+    |/** Second comment */
+    |/** Real comment */
+    |class Class
+    """.stripMargin
+
+  import dotty.tools.dotc.ast.untpd._
+  override def assertion = {
+    case PackageDef(_, Seq(c: TypeDef)) =>
+      checkDocString(c.rawComment, "/** Real comment */")
+  }
+}
+
+case object MultipleDocStringsBeforeAndAfter extends DottyDocTest {
+  override val source =
+    """
+    |/** First comment */
+    |/** Second comment */
+    |/** Real comment */
+    |class Class
+    |/** Following comment 1 */
+    |/** Following comment 2 */
+    |/** Following comment 3 */
+    """.stripMargin
+
+  import dotty.tools.dotc.ast.untpd._
+  override def assertion = {
+    case PackageDef(_, Seq(c: TypeDef)) =>
+      checkDocString(c.rawComment, "/** Real comment */")
+  }
+
+}