No warn when discarding r.f(): r.type

The paradigm is `def add(x: X): Unit = listBuffer += x`.

The value that is discarded is not new information.

Also cleans up the recent tweaks to help messaging.

Adds newlines in case they ask for multiple helps.

1 files changed, 6 insertions, 0 deletions

diff --git a/test/files/pos/t9020.scala b/test/files/pos/t9020.scala
index 16e31e2572..c77a63cb1a 100644
--- a/test/files/pos/t9020.scala
+++ b/test/files/pos/t9020.scala
@@ -8,3 +8,9 @@ test/files/pos/t9020.scala:2: warning: discarded non-Unit value
       ^
 one warning found
 */
+
+trait DiscardThis {
+  import collection.mutable.ListBuffer
+  val b = ListBuffer.empty[String]
+  def add(s: String): Unit = b += s
+}