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

Comienza ejecutando la reproducción de FERMI proporcionada con las versiones indicadas de PowerShell y de la extensión de VS Code; después, inspecciona cómo el analizador realiza el seguimiento de las variables creadas con Set-Variable -Option AllScope dentro de funciones anidadas. Se considera terminado cuando los diagnósticos tienen correctamente en cuenta los usos de las variables o el issue documenta claramente por qué las advertencias son válidas.