patch 8.2.2033: Vim9: :def without argument gives compilation error

Problem:    Vim9: :def without argument gives compilation error.
Solution:   Add the DEF instruction. (closes #7344)
diff --git a/src/testdir/test_vim9_func.vim b/src/testdir/test_vim9_func.vim
index dd2f576..80d564e 100644
--- a/src/testdir/test_vim9_func.vim
+++ b/src/testdir/test_vim9_func.vim
@@ -288,6 +288,33 @@
   CheckScriptFailure(lines, "E1073:")
 enddef
 
+def DefListAll()
+  def
+enddef
+
+def DefListOne()
+  def DefListOne
+enddef
+
+def DefListMatches()
+  def /DefList
+enddef
+
+def Test_nested_def_list()
+  var funcs = split(execute('call DefListAll()'), "\n")
+  assert_true(len(funcs) > 10)
+  assert_true(funcs->index('def DefListAll()') >= 0)
+
+  funcs = split(execute('call DefListOne()'), "\n")
+  assert_equal(['   def DefListOne()', '1    def DefListOne', '   enddef'], funcs)
+
+  funcs = split(execute('call DefListMatches()'), "\n")
+  assert_true(len(funcs) >= 3)
+  assert_true(funcs->index('def DefListAll()') >= 0)
+  assert_true(funcs->index('def DefListOne()') >= 0)
+  assert_true(funcs->index('def DefListMatches()') >= 0)
+enddef
+
 def Test_global_local_function()
   var lines =<< trim END
       vim9script