patch 8.2.0270: some code not covered by tests

Problem:    Some code not covered by tests.
Solution:   Add test cases. (Yegappan Lakshmanan, closes #5649)

src/testdir/test_vimscript.vim

@@ -2061,6 +2061,16 @@ func Test_deep_nest()
   call delete('Xscript')
 endfunc
 
+" Test for <sfile>, <slnum> in a function                           {{{1
+func Test_sfile_in_function()
+  func Xfunc()
+    call assert_match('..Test_sfile_in_function\[5]..Xfunc', expand('<sfile>'))
+    call assert_equal('2', expand('<slnum>'))
+  endfunc
+  call Xfunc()
+  delfunc Xfunc
+endfunc
+
 "-------------------------------------------------------------------------------
 " Modelines								    {{{1
 " vim: ts=8 sw=2 sts=2 expandtab tw=80 fdm=marker