patch 8.2.1459: Vim9: declaring script var in script does not infer the type

Problem:    Vim9: declaring ascript variable at the script level does not
            infer the type.
Solution:   Get the type from the value. (closes #6716)
diff --git a/src/testdir/test_vim9_script.vim b/src/testdir/test_vim9_script.vim
index 163b948..d8e20e1 100644
--- a/src/testdir/test_vim9_script.vim
+++ b/src/testdir/test_vim9_script.vim
@@ -2914,12 +2914,20 @@
     let s:other: number
     other = 1234
     g:other_var = other
+
+    # type is inferred
+    s:dict = {'a': 222}
+    def GetDictVal(key: any)
+      g:dict_val = s:dict[key]
+    enddef
+    GetDictVal('a')
   END
   CheckScriptSuccess(lines)
   assert_equal('', g:var_uninit)
   assert_equal('text', g:var_test)
   assert_equal('prefixed', g:var_prefixed)
   assert_equal(1234, g:other_var)
+  assert_equal(222, g:dict_val)
 
   unlet g:var_uninit
   unlet g:var_test