Basic powershell completions

Basic Completions.ps1

function New.CompletionResult {
    [Alias('New.CR')]
    param(
        # original base text
        [Alias('Item', 'Text')]
        [Parameter(Mandatory)]
        [ValidateNotNullOrEmpty()]
        [ValidateNotNullOrWhiteSpace()]
        [string]$ListItemText,

        # actual value used in replacement, if not the same as ListItem
        [AllowEmptyString()]
        [AllowNull()]
        [Alias('Replacement', 'Replace')]
        [Parameter()]
        [string]$CompletionText,

        # Is there a better default?
        [Parameter()]
        [CompletionResultType]
        $ResultType  = ([CompletionResultType]::ParameterValue),

        # multi-line text displayed when using listcompletion
        [Parameter()]
        [Alias('Description', 'Help', 'RenderText')]
        [string[]]$Tooltip
    )
    [System.ArgumentException]::ThrowIfNullOrWhiteSpace( $ListItemText , 'ListItemText' )

    $Tooltip =  $Tooltip -join "`n"
    if( [string]::IsNullOrEmpty( $Tooltip )) {
        $Tooltip = '[⋯]'
    }
    if( [string]::IsNullOrEmpty( $CompletionText )) {
        $CompletionText = $ListItemText
    }
    [CompletionResult]::new(
        <# completionText: #> $completionText,
        <# listItemText  : #> $listItemText,
        <# resultType    : #> $resultType,
        <# toolTip       : #> $toolTip)
}