patch 9.0.0480: cannot use a :def varargs function with substitute()

Problem:    Cannot use a :def varargs function with substitute().
Solution:   Use has_varargs(). (closes #11146)

src/regexp.c

@@ -1824,7 +1824,7 @@ fill_submatch_list(int argc UNUSED, typval_T *argv, int argskip, ufunc_T *fp)
     char_u	*s;
     typval_T	*listarg = argv + argskip;
 
-    if (!fp->uf_varargs && fp->uf_args.ga_len <= argskip)
+    if (!has_varargs(fp) && fp->uf_args.ga_len <= argskip)
 	// called function doesn't take a submatches argument
 	return argskip;
 

src/testdir/test_substitute.vim

@@ -442,6 +442,9 @@ endfunc
 func SubReplacerVar(text, ...)
   return a:text .. a:1[0] .. a:text
 endfunc
+def SubReplacerVar9(text: string, ...args: list<list<string>>): string
+  return text .. args[0][0] .. text
+enddef
 func SubReplacer20(t1, t2, t3, t4, t5, t6, t7, t8, t9, t10, t11, t12, t13, t14, t15, t16, t17, t18, t19, submatches)
   return a:t3 .. a:submatches[0] .. a:t11
 endfunc
@@ -449,6 +452,7 @@ endfunc
 func Test_substitute_partial()
   call assert_equal('1foo2foo3', substitute('123', '2', function('SubReplacer', ['foo']), 'g'))
   call assert_equal('1foo2foo3', substitute('123', '2', function('SubReplacerVar', ['foo']), 'g'))
+  call assert_equal('1foo2foo3', substitute('123', '2', function('SubReplacerVar9', ['foo']), 'g'))
 
   " 19 arguments plus one is just OK
   let Replacer = function('SubReplacer20', repeat(['foo'], 19))

src/version.c

@@ -703,6 +703,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    480,
 /**/
     479,
 /**/