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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Unexpected behavior of AutomationNull in object initializers using [pscustomobject]","articleBody":"### Prerequisites\r\n\r\n- [X] Write a descriptive title.\r\n- [X] Make sure you are able to repro it on the [latest released version](https://github.com/PowerShell/PowerShell/releases)\r\n- [X] Search the existing issues.\r\n- [X] Refer to the [FAQ](https://github.com/PowerShell/PowerShell/blob/master/docs/FAQ.md).\r\n- [X] Refer to [Differences between Windows PowerShell 5.1 and PowerShell](https://docs.microsoft.com/powershell/scripting/whats-new/differences-from-windows-powershell).\r\n\r\n### Steps to reproduce\r\n\r\nNote: Initializing via `[hashtable]` used to break too, but that was fixed in #19402 / #19415.\r\n\r\nIn an array-type-constrained variable (as in expressions in general), AutomationNull is treated like `$null`; e.g.:\r\n\r\n```powershell\r\n# Note: \u0026 { } is a simple way to return the AutomationNull singleton.\r\n# OK: no error\r\n[string[]] $arr = \u0026 { }\r\n```\r\n\r\nBy contrast, using AutomationNull in `[pscustomobject]`-based object initializers fails:\r\n\r\n```powershell\r\nclass Example {\r\n   [string[]]$LogMessage\r\n}\r\n\r\n$automationNull = \u0026 {}\r\n\r\n# !! BREAKS: \"\"Type 'System.String[]' does not have a default constructor (Parameter 'type')\"\"\r\n[Example] [pscustomobject] @{ 'LogMessage' = $automationNull }\r\n```\r\n\r\nThe symptom is reminiscent of https://github.com/PowerShell/PowerShell/issues/19384#issuecomment-1478411266\r\n\r\n### Expected behavior\r\n \r\nAn `[Example]` instance should be constructed, with `$null` returned from its .LogMessage property.\r\n\r\nNote: If this is resolved in the same way as for _hashtable_ initializers, it is actually `[System.Management.Automation.Internal.AutomationNull]::Value` that is _stored_ in the property, but on _accessing_ (getting) it, it turns to `$null`.\r\n\r\nOutside of a class this behavior is directly visible:\r\n\r\n```powershell\r\n# -\u003e $true\r\n [object]::ReferenceEquals((\r\n  [string[]] $arr = \u0026 { }), \r\n  [System.Management.Automation.Internal.AutomationNull]::Value\r\n)\r\n```\r\n\r\n### Actual behavior\r\n\r\n```console\r\nInvalidArgument: \r\nCannot convert value \"@{LogMessage=}\" to type \"Example\". \r\nError: \"Type 'System.String[]' does not have a default constructor (Parameter 'type')\"\r\n```\r\n\r\n\r\n### Error details\r\n\r\n_No response_\r\n\r\n### Environment data\r\n\r\n```powershell\r\nPowerShell Core 7.4.0-preview.3\r\n```\r\n\r\n\r\n### Visuals\r\n\r\n_No response_","author":{"url":"https://github.com/mklement0","@type":"Person","name":"mklement0"},"datePublished":"2023-04-20T19:13:01.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":4},"url":"https://github.com/19552/PowerShell/issues/19552"}