Variables, defined with "-Option AllScope", in Nested Function reports "assigned but never used".

Issue Description

I'm learning PowerShell, and also new to Visual Studio Code, and ran into a situation where it would be useful to create nested functions that access the parent function's variables. To my pleasant surprise PowerShell can do this and I created the below code to try it out. But Visual Studio Code continues to complain "The variable 'Data' is assigned but never used." and "The variable 'Return' is assigned but never used." But PowerShell itself seems to be quite happy with the code and produces the results I expected.

It appears that Visual Studio code is not recognizing the work that "Set-Variable", with the "AllScope" option, does in making these variables accessible throughout the GetMatchingIndex method (I wouldn't be surprised if "AllScope" makes it accessible outside the class - coming from a C# background, PowerShell does some really weird things).

If VSCode is working correctly, and there really are 2 bugs in my code, then I guess I need someone to explain how to fix the code.

class FERMI {   # ForEachReturnMatchingIndex
    [string[]]$CharSets
    FERMI() {
        $this.CharSets = 'ab', 'cd', 'ef', 'gh'
    }
    [int] GetMatchingIndex([string]$StringToFind) {
        Write-Host
        Set-Variable -Name ItemIndex, UpperOuterBounds, Data, Return -Option AllScope
        [int]$Return = [int]$ItemIndex = -1
        $UpperOuterBounds = $this.CharSets.Length
        function AbleToGetAnotherItem {
            [OutputType([bool])]
            param ()
            if ($atgaiReturn = ++$ItemIndex -lt $UpperOuterBounds) { $Data = $this.CharSets[$ItemIndex]}
            return $atgaiReturn
        }
        function ProcessData {
            Write-Host "Data: $Data, Index: $ItemIndex"
            if($Data -eq $StringToFind){
                $Return = $ItemIndex
            }
        }
        While (AbleToGetAnotherItem) {
            ProcessData
        }
        return $Return
    }
}

[FERMI] $MyFERMI = [FERMI]::New()
Write-Host "ef: $($MyFERMI.GetMatchingIndex('ef'))"
Write-Host "cd: $($MyFERMI.GetMatchingIndex('cd'))"
Write-Host "ij: $($MyFERMI.GetMatchingIndex('ij'))"
Write-Host "gh: $($MyFERMI.GetMatchingIndex('gh'))"
Write-Host "ab: $($MyFERMI.GetMatchingIndex('ab'))"

Environment Information

Visual Studio Code

PowerShell Information

Visual Studio Code Extensions

首先，使用报告中所述的 PowerShell 和 VS Code 扩展版本运行随附的 FERMI 复现，然后检查 analyzer 如何跟踪在嵌套函数中通过 Set-Variable -Option AllScope 创建的变量。完成的标准是：诊断能够正确计入这些变量的使用情况，或者 issue 清楚地说明这些警告为何有效。