patch 8.2.1302: Vim9: varargs arg after optional arg does not work

Problem:    Vim9: varargs arg after optional arg does not work
Solution:   Check for the "..." first. (issue #6507)

Author: brammool

src/testdir/test_vim9_func.vim

@@ -376,6 +376,28 @@ def Test_call_funcref()
     assert_equal([1, 2, 3], g:echo)
   END
   CheckScriptSuccess(lines)
+
+  lines =<< trim END
+    vim9script
+    def OptAndVar(nr: number, opt = 12, ...l: list<number>): number
+      g:optarg = opt
+      g:listarg = l
+      return nr
+    enddef
+    let Funcref: func(number, ?number, ...list<number>): number = function('OptAndVar')
+    assert_equal(10, Funcref(10))
+    assert_equal(12, g:optarg)
+    assert_equal([], g:listarg)
+
+    assert_equal(11, Funcref(11, 22))
+    assert_equal(22, g:optarg)
+    assert_equal([], g:listarg)
+
+    assert_equal(17, Funcref(17, 18, 1, 2, 3))
+    assert_equal(18, g:optarg)
+    assert_equal([1, 2, 3], g:listarg)
+  END
+  CheckScriptSuccess(lines)
 enddef
 
 let SomeFunc = function('len')

src/version.c

@@ -754,6 +754,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1302,
 /**/
     1301,
 /**/

src/vim9compile.c

@@ -2106,16 +2106,16 @@ parse_type(char_u **arg, garray_T *type_gap)
 				first_optional = argcount;
 			    ++p;
 			}
-			else if (first_optional != -1)
-			{
-			    emsg(_("E1007: mandatory argument after optional argument"));
-			    return &t_any;
-			}
 			else if (STRNCMP(p, "...", 3) == 0)
 			{
 			    flags |= TTFLAG_VARARGS;
 			    p += 3;
 			}
+			else if (first_optional != -1)
+			{
+			    emsg(_("E1007: mandatory argument after optional argument"));
+			    return &t_any;
+			}
 
 			arg_type[argcount++] = parse_type(&p, type_gap);