Why is [pscustomobject] the same as [psobject], even though a distinct [System.Management.Automation.PSCustomObject] type exists? #4344
Description
Surprisingly, [pscustomobject] is the same as [psobject]: both these type accelerators point to type [System.Management.Automation.PSObject], even though there is a distinct [System.Management.Automation.PSCustomObject] type.
Mostly, this conflation goes unnoticed (and has come up before - see #2295), but:
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what is the rationale for it?
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it makes for surprising behavior on occasion - see below.
# Even though their names strongly suggest identity, they are different types.
> [pscustomobject] -eq [System.Management.Automation.PSCustomObject]
False
# Any object returned by a *command* (as opposed to an expression)
# returns $True for -is [psobject], and therefore also [pscustomobject]
> (Get-Item /) -is [pscustomobject]
True
# Casting anything other than a hashtable literal to [psobject] is a no-op,
# and therefore also with [pscustomobject]
> ([pscustomobject] 666).GetType().Name
Int32Environment data
PowerShell Core v6.0.0-beta.4