patch 8.2.4006: Vim9: crash when declaring variable on the command line

Problem:    Vim9: crash when declaring variable on the command line.
Solution:   Use a temporary type list. (closes #9474)

src/testdir/test_vim9_assign.vim

@@ -2,6 +2,7 @@
 
 source check.vim
 source vim9.vim
+source term_util.vim
 
 let s:appendToMe = 'xxx'
 let s:addToMe = 111
@@ -2281,6 +2282,23 @@ def Test_abort_after_error()
   delete('Xtestscript')
 enddef
 
+func Test_declare_command_line()
+  CheckRunVimInTerminal
+  call Run_Test_declare_command_line()
+endfunc
+
+def Run_Test_declare_command_line()
+  # On the command line the type is parsed but not used.
+  # To get rid of the script context have to run this in another Vim instance.
+  var buf = RunVimInTerminal('', {'rows': 6})
+  term_sendkeys(buf, ":vim9 var abc: list<list<number>> = [ [1, 2, 3], [4, 5, 6] ]\<CR>")
+  TermWait(buf)
+  term_sendkeys(buf, ":echo abc\<CR>")
+  TermWait(buf)
+  WaitForAssert(() => assert_match('\[\[1, 2, 3\], \[4, 5, 6\]\]', term_getline(buf, 6)))
+  StopVimInTerminal(buf)
+enddef
+
 
 
 " vim: ts=8 sw=2 sts=2 expandtab tw=80 fdm=marker