patch 8.0.0040
Problem:    Whole line highlighting with matchaddpos() does not work.
Solution:   Check for zero length. (Hirohito Higashi)
diff --git a/src/testdir/test_match.vim b/src/testdir/test_match.vim
index 3b20d5d..9398ef2 100644
--- a/src/testdir/test_match.vim
+++ b/src/testdir/test_match.vim
@@ -191,7 +191,15 @@
   call assert_equal(screenattr(2,2), screenattr(1,7))
   call assert_notequal(screenattr(2,2), screenattr(1,8))
 
+  call clearmatches()
+  call matchaddpos('Error', [[1], [2,2]])
+  redraw!
+  call assert_equal(screenattr(2,2), screenattr(1,1))
+  call assert_equal(screenattr(2,2), screenattr(1,10))
+  call assert_notequal(screenattr(2,2), screenattr(1,11))
+
   nohl
+  call clearmatches()
   syntax off
   set hlsearch&
 endfunc