"Variable assigned but never used" false positive in a script block passed to `ForEach-Object`

[ForNeVeR]

Steps to reproduce

(Initially reported in downstream repo, see ant-druha/intellij-powershell#96, but with my adjustments to better demonstrate the behavior.)

(1..3) | ForEach-Object {
    $Hashes = "test"
} {
    $Hashes += "Some-String "
} {
    $Hashes
}

Expected behavior

There should be no warnings about the initial value of the $Hashes variable not being used in this code.

To demonstrate that it is in fact used, run the code, and you'll see output testSome-String Some-String Some-String: test value was used.

Actual behavior

The variable 'Hashes' is assigned but never used.PSScriptAnalyzer(PSUseDeclaredVarsMoreThanAssignments)

Environment data

While it was reported in intellij-powershell where we bundle v1.21.0, I was also able to reproduce the same in VSCode.

> $PSVersionTable
Name                           Value
----                           -----
PSVersion                      7.3.7
PSEdition                      Core
GitCommitId                    7.3.7
OS                             Microsoft Windows 10.0.22621
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() }
1.21.0

Additional Information

From a quick look, it may be related to #1472.

[iRon7]

Duplicate with #1163?

[ForNeVeR]

I think it's a duplicate. Thank you!

[iRon7]

Anyways, I think that these two rules (PSUseDeclaredVarsMoreThanAssignments and PSReviewUnusedParameter) have been overcomplicated the issue were it could just be: don't warn if the concerned variable can be found back (anywhere) in the script (even this might not capture everything, it is better than a false-possitive)