PSUseOutputTypeCorrectly/[OutputType()] fires incorrectly, reporting that a fn should return string when the function actually return array of strings

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Steps to reproduce

function Split-KeyValuePairFormatter {
  [OutputType('System.String[]')]
  [CmdletBinding()]
  param (
    [Parameter(Mandatory = $true)]
    [string]
    $Format,

    [string]
    $KeyConstituent,

    [string]
    $ValueConstituent,

    [string]
    $KeyPlaceHolder = "<%KEY%>",

    [string]
    $ValuePlaceHolder = "<%VALUE%>"
  )
  [string[]]$constituents = @();

   # IMPLEMENTATION CODE OMITTED, but you can see that the return statement
   # just returns the array declared as string[]

   return $constituents;
}

Expected behavior

No warning expected

Actual behavior

Error:

RuleName                            Severity     ScriptName Line  Message
--------                            --------     ---------- ----  -------
PSUseOutputTypeCorrectly            Information  split-key- 152   The cmdlet 'Split-KeyValuePairFormatter' returns an  
                                                 value-pair       object of type 'System.String' but this type is not  
                                                 -formatter       declared in the OutputType attribute.
                                                 .ps1

If I change OutputType to: [OutputType('System.String')], which is clearly wrong as it doesn't reflect the behaviour of the actual code, then there is no error. This does not seem right. As a work around, I'm having to declare an incorrect return type, ie System.string in [OutputType()], and put in a comment to indicate as such. Luckily, there is no effect on the functinality, but I can't omit the OutputType without PSScriptAnalyzer reporting a warning.

Environment data

> $PSVersionTable

Name                           Value
----                           -----
PSVersion                      7.0.0
PSEdition                      Core
GitCommitId                    7.0.0
OS                             Microsoft Windows 10.0.18362
Platform                       Win32NT
PSCompatibleVersions           {1.0, 2.0, 3.0, 4.0…}
PSRemotingProtocolVersion      2.3
SerializationVersion           1.1.0.1
WSManStackVersion              3.0

> (Get-Module -ListAvailable PSScriptAnalyzer).Version | ForEach-Object { $_.ToString() }
1.19.0
1.18.3

Bắt đầu bằng cách tái hiện cảnh báo PSUseOutputTypeCorrectly với ví dụ Split-KeyValuePairFormatter và kiểm tra cách quy tắc xử lý OutputType('System.String[]'). So sánh kiểu trả về được suy luận với kiểu mảng đã khai báo. Hoàn tất khi quy tắc chấp nhận giá trị trả về là mảng chuỗi mà không yêu cầu khai báo System.String không chính xác.