NullReferenceException in PSAvoidAssignmentToAutomaticVariable rule when assigning .Net property to .Net property (v 1.17.0)

[bergmeister]

Thanks to Oliver Lipkau (@lipkau) for the initial bug report in Slack.

Steps to reproduce

Invoke-ScriptAnalyzer -ScriptDefinition '[foo]::bar = [baz]::qux'

Expected behavior

Normal behaviour, no warnings.

Actual behavior

Invoke-ScriptAnalyzer : Object reference not set to an instance of an object.
At line:1 char:2
+  Invoke-ScriptAnalyzer -ScriptDefinition '[foo]::SecurityProtocol = [ ...
+  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : InvalidOperation: (:) [Invoke-ScriptAnalyzer], NullReferenceException
    + FullyQualifiedErrorId : RULE_ERROR,Microsoft.Windows.PowerShell.ScriptAnalyzer.Commands.InvokeScriptAnalyzerCommand

If an unexpected error was thrown then please report the full error details using e.g. $error[0] | Select-Object *

writeErrorStream      : True
PSMessageDetails      :
Exception             : System.NullReferenceException: Object reference not set to an instance of an object.
                           at Microsoft.Windows.PowerShell.ScriptAnalyzer.BuiltinRules.AvoidAssignmentToAutomaticVariable.<AnalyzeScript>d__2.MoveNext()
                           at System.Collections.Generic.List`1..ctor(IEnumerable`1 collection)
                           at System.Linq.Enumerable.ToList[TSource](IEnumerable`1 source)
                           at Microsoft.Windows.PowerShell.ScriptAnalyzer.ScriptAnalyzer.<>c__DisplayClass82_1.<AnalyzeSyntaxTree>b__2()
TargetObject          :
CategoryInfo          : InvalidOperation: (:) [Invoke-ScriptAnalyzer], NullReferenceException
FullyQualifiedErrorId : RULE_ERROR,Microsoft.Windows.PowerShell.ScriptAnalyzer.Commands.InvokeScriptAnalyzerCommand
ErrorDetails          :
InvocationInfo        : System.Management.Automation.InvocationInfo
ScriptStackTrace      : at <ScriptBlock>, <No file>: line 1
PipelineIterationInfo : {0, 1}
writeErrorStream      : True
PSMessageDetails      :
Exception             : System.NullReferenceException: Object reference not set to an instance of an object.
                           at Microsoft.Windows.PowerShell.ScriptAnalyzer.BuiltinRules.AvoidAssignmentToAutomaticVariable.<AnalyzeScript>d__2.MoveNext()
                           at System.Collections.Generic.List`1..ctor(IEnumerable`1 collection)
                           at System.Linq.Enumerable.ToList[TSource](IEnumerable`1 source)
                           at Microsoft.Windows.PowerShell.ScriptAnalyzer.ScriptAnalyzer.<>c__DisplayClass82_1.<AnalyzeSyntaxTree>b__2()
TargetObject          :
CategoryInfo          : InvalidOperation: (:) [Invoke-ScriptAnalyzer], NullReferenceException
FullyQualifiedErrorId : RULE_ERROR,Microsoft.Windows.PowerShell.ScriptAnalyzer.Commands.InvokeScriptAnalyzerCommand
ErrorDetails          :
InvocationInfo        : System.Management.Automation.InvocationInfo
ScriptStackTrace      : at <ScriptBlock>, <No file>: line 1
PipelineIterationInfo : {0, 1}

Environment data

This bug was introduced in 1.17.0 in the new PSAvoidAssignmentToAutomaticVariable

> $PSVersionTable
Name                           Value
----                           -----
PSVersion                      5.1.17134.81
PSEdition                      Desktop
PSCompatibleVersions           {1.0, 2.0, 3.0, 4.0...}
BuildVersion                   10.0.17134.81
CLRVersion                     4.0.30319.42000
WSManStackVersion              3.0
PSRemotingProtocolVersion      2.3
SerializationVersion           1.1.0.1
> (Get-Module -ListAvailable PSScriptAnalyzer).Version | ForEach-Object { $_.ToString() }
1.17.0

[bergmeister]

Oliver Lipkau (@lipkau) The fix of this has been released as part of the new 1.17.1 release