symbol is missing from vscode outline

Prerequisites

Please put an X between the brackets as you perform the following steps:

• Check that your issue is not already filed:
  https://github.com/leanprover/lean4/issues
• Reduce the issue to a minimal, self-contained, reproducible test case.
  Avoid dependencies to Mathlib or Batteries.
• Test your test case against the latest nightly release, for example on
  https://live.lean-lang.org/#project=lean-nightly
  (You can also use the settings there to switch to “Lean nightly”)

Description

open Nat in
def x := 0

set_option pp.all true in
def y := 0

x and y can't be shown in vscode outline.

Context

zulip discussion is here

Steps to Reproduce

1. copy the above code to vscode
2. see the outline

Expected behavior:
There are x and y in the outline.

Actual behavior:
x and y are missing.

Versions

Lean: 4.9.0
vscode: 1.84.2

Additional Information

Impact

Add 👍 to issues you consider important. If others are impacted by this issue, please ask them to add 👍 to it.

Start by copying the minimal Lean snippet into VS Code with Lean 4.9.0 and reproduce the missing outline entries. Compare the reported behavior with the expected outline containing both x and y; done means both definitions appear, including those using open Nat and set_option pp.all.