vim-patch:7.4.1816 (#5833)

Problem:    Looping over a null list throws an error.
Solution:   Skip over the for loop.

d8585eded6

src/nvim/eval.c

@@ -2621,9 +2621,12 @@ void *eval_for_line(char_u *arg, int *errp, char_u **nextcmdp, int skip)
     *errp = FALSE;
     if (!skip) {
       l = tv.vval.v_list;
-      if (tv.v_type != VAR_LIST || l == NULL) {
+      if (tv.v_type != VAR_LIST) {
         EMSG(_(e_listreq));
         clear_tv(&tv);
+      } else if (l == NULL) {
+        // a null list is like an empty list: do nothing
+        clear_tv(&tv);
       } else {
         /* No need to increment the refcount, it's already set for the
          * list being used in "tv". */

src/nvim/testdir/test_expr.vim

@@ -74,3 +74,10 @@ func Test_dict()
   call assert_equal('none', d[''])
   call assert_equal('aaa', d['a'])
 endfunc
+
+func Test_loop_over_null_list()
+  let null_list = submatch(1, 1)
+  for i in null_list
+    call assert_true(0, 'should not get here')
+  endfor
+endfunc

src/nvim/version.c

@@ -623,7 +623,7 @@ static int included_patches[] = {
   // 1819 NA
   1818,
   // 1817 NA
-  // 1816,
+  1816,
   // 1815,
   // 1814 NA
   // 1813,