Suppression with SuppressMessageAttribute is completely broken for variables

[BalassaMarton]

Steps to reproduce

Consider this code:

$foo = "never used" # Should generate PSUseDeclaredVarsMoreThanAssignments

$global:var1 = $null # Should generate PSAvoidGlobalVars

Now let's try to add these suppressions:

[Diagnostics.CodeAnalysis.SuppressMessage('NonexistentRule', '')]
$foo = "never used" # Should still generate PSUseDeclaredVarsMoreThanAssignments

[Diagnostics.CodeAnalysis.SuppressMessage('PSAvoidGlobalVars', '')]
$global:var1 = $null # Should NOT generate PSAvoidGlobalVars

Expected behavior

I should still see the PSUseDeclaredVarsMoreThanAssignments warning, but not the PSAvoidGlobalVars one.

Actual behavior

The opposite happens, the first message is suppressed, but the second is not:

RuleName                             Severity     ScriptName Line  Message
--------                             --------     ---------- ----  -------
PSAvoidGlobalVars                    Warning      Test.ps1      5     Found global variable 'global:var1'.

Environment data

> $PSVersionTable

Name                           Value
----                           -----
PSVersion                      7.4.5
PSEdition                      Core
GitCommitId                    7.4.5
OS                             Microsoft Windows 10.0.22631
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() }
1.23.0

[MartinGC94]

Variables that are assigned with attributes are not handled by the PSUseDeclaredVarsMoreThanAssignments rule. For example, this: [ValidateNotNull()]$var1 = 1 is also not handled by that rule because of the validation attribute. Multiple type conversions/constraints also don't work: [string] [int] $var1 = 1.

The root cause and fix is likely the same that I recently found in the ast analyzer for variable completion: PowerShell/PowerShell#25016
Here I was only looking at ConvertExpressions and assuming the child would be the variable when I should have looked for AttributedExpressions and traverse through the children until I found the variable expression.