patch 8.1.0053: first argument of 'completefunc' has inconsistent type

Problem:    The first argument given to 'completefunc' can be Number or
            String, depending on the value.
Solution:   Avoid guessing the type of an argument, use typval_T in the
            callers of call_vim_function(). (Ozaki Kiichi, closes #2993)
diff --git a/src/testdir/test_ins_complete.vim b/src/testdir/test_ins_complete.vim
index 020e228..2b4356e 100644
--- a/src/testdir/test_ins_complete.vim
+++ b/src/testdir/test_ins_complete.vim
@@ -117,6 +117,31 @@
   set omnifunc=
 endfunc
 
+func Test_completefunc_args()
+  let s:args = []
+  func! CompleteFunc(findstart, base)
+    let s:args += [[a:findstart, empty(a:base)]]
+  endfunc
+  new
+
+  set completefunc=CompleteFunc
+  call feedkeys("i\<C-X>\<C-U>\<Esc>", 'x')
+  call assert_equal(s:args[0], [1, 1])
+  call assert_equal(s:args[1][0], 0)
+  set completefunc=
+
+  let s:args = []
+  set omnifunc=CompleteFunc
+  call feedkeys("i\<C-X>\<C-O>\<Esc>", 'x')
+  call assert_equal(s:args[0], [1, 1])
+  call assert_equal(s:args[1][0], 0)
+  set omnifunc=
+
+  bwipe!
+  unlet s:args
+  delfunc CompleteFunc
+endfunc
+
 function! s:CompleteDone_CompleteFuncDict( findstart, base )
   if a:findstart
     return 0