patch 8.2.1244: Vim9: in lambda index assumes a list

Problem:    Vim9: in lambda index assumes a list.
Solution:   Use the value type to decide about list or dict. (closes #6479)
diff --git a/src/testdir/test_vim9_expr.vim b/src/testdir/test_vim9_expr.vim
index 4c8e6e1..a922543 100644
--- a/src/testdir/test_vim9_expr.vim
+++ b/src/testdir/test_vim9_expr.vim
@@ -1115,7 +1115,7 @@
   call CheckDefExecFailure(["let x = g:anint[3]"], 'E714:')
   call CheckDefFailure(["let x = g:list_mixed[xxx]"], 'E1001:')
   call CheckDefFailure(["let x = [1,2,3]"], 'E1069:')
-  call CheckDefExecFailure(["let x = g:list_mixed['xx']"], 'E39:')
+  call CheckDefExecFailure(["let x = g:list_mixed['xx']"], 'E1029:')
   call CheckDefFailure(["let x = g:list_mixed["], 'E1097:')
   call CheckDefFailure(["let x = g:list_mixed[0"], 'E1097:')
   call CheckDefExecFailure(["let x = g:list_empty[3]"], 'E684:')
@@ -1173,6 +1173,9 @@
 	})
   assert_equal([111, 222, 111], ll)
 
+  let dl = [{'key': 0}, {'key': 22}]->filter({ _, v -> v['key'] })
+  assert_equal([{'key': 22}], dl)
+
   call CheckDefFailure(["filter([1, 2], {k,v -> 1})"], 'E1069:')
 enddef