Adding an attribute to a variable prevents its appearance in the Outline

Prerequisites

• I have written a descriptive issue title.
• I have searched all issues to ensure it has not already been reported.
• I have read the troubleshooting guide.
• I am sure this issue is with the extension itself and does not reproduce in a standalone PowerShell instance.
• I have verified that I am using the latest version of Visual Studio Code and the PowerShell extension.
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Summary

When adding an attribute to a variable (in this case System.Diagnostics.CodeAnalysis.SuppressMessageAttribute, but the outcome is the same for other attributes such as ValidateSetAttribute), the variable will no longer appear the the 'Outline' panel.

Take this script for example:

$MyVariable = 'foobar'

The variable MyVariable appears in the 'Outline' panel. Now, add an attribute to it. In this case, I added the System.Diagnostics.CodeAnalysis.SuppressMessageAttribute attribute to disable the PSUserDeclaredVarsMoreThanAssignments warning from not using the variable in the current script.

[Diagnostics.CodeAnalysis.SuppressMessageAttribute('PSUserDeclaredVarsMoreThanAssignments', '')]
$MyVariable = 'foobar'

The script works correctly, and the attribute correctly disables the warning, but the variable no longer appears in the 'Outline' panel.

PowerShell Version

Name                           Value
----                           -----
PSVersion                      7.2.2
PSEdition                      Core
GitCommitId                    7.2.2
OS                             Microsoft Windows 10.0.19043
Platform                       Win32NT
PSCompatibleVersions           {1.0, 2.0, 3.0, 4.0…}
PSRemotingProtocolVersion      2.3
SerializationVersion           1.1.0.1
WSManStackVersion              3.0

Visual Studio Code Version

1.66.1
8dfae7a5cd50421d10cd99cb873990460525a898
x64

Extension Version

ms-vscode.powershell@2021.12.0

Steps to Reproduce

1. Create a variable in the top-level scope. (It appears in the Outline.)
2. Add an attribute to it. (It no longer appears in the Outline)

Visuals

No response

Logs

No response

Reproduce the issue with the two PowerShell examples and trace how the extension produces Outline symbols for top-level variables, comparing the unannotated and attributed forms. Done when an attributed variable appears in the Outline panel without changing the script's behavior.