Merge pull request #10070 from griggt/fix-#6655

Fix #6655: Add regression test

Author: nicolasstucki

tests/pos/i6655.scala

@@ -0,0 +1,10 @@
+class Test {
+  def foo(): Unit = {
+    val x: String|Null = ???
+    if (x != null) {
+      val y = x.length
+    } else {
+      val y = x
+    }
+  }
+}