patch 8.1.1993: more functions can be used as methods

Problem:    More functions can be used as methods.
Solution:   Make various functions usable as a method.
diff --git a/src/testdir/test_functions.vim b/src/testdir/test_functions.vim
index dfd6a93..1d8d74d 100644
--- a/src/testdir/test_functions.vim
+++ b/src/testdir/test_functions.vim
@@ -1137,7 +1137,7 @@
   wincmd h
   let wh = winheight('.')
   let dummy_buf = bufnr('dummy_buf2', v:true)
-  call setbufvar(dummy_buf, '&buftype', 'nofile')
+  eval 'nofile'->setbufvar(dummy_buf, '&buftype')
   execute 'belowright vertical split #' . dummy_buf
   call assert_equal(wh, winheight('.'))
 
@@ -1413,7 +1413,7 @@
   " is invalid in that buffer.
   call writefile(['just one line'], 'Xfuncrange2')
   new
-  call setline(1, 10->range())
+  eval 10->range()->setline(1)
   write Xfuncrange1
   call assert_fails('5,8call EditAnotherFile()', 'E16:')