Why @($null) is $false, but @($null, $null) is $true?

Question

Curious, what is the idea behind this:

@() -as [bool]
# False

@($null) -as [bool] 
# False

@($null, $null) -as [bool]
# True

I would expect either False/True/True or False/False/False, but not False/False/True.

Answer 1

As outlined in the Powershell Quick reference¹:

True                                                 False 
~~~~                                                 ~~~~~
$TRUE                                                $FALSE 
Any string of length > 0, except the word “false”    Empty string or the string “false” 
Any number ≠ 0                                       Any number = 0 
Array of length > 1                                  Array of length 0 
Array of length 1 whose element is true              Array of length 1 whose element is false 
A reference to any object                            Null 

I think the idea behind it was that an array with just one element $false can easily happen if you put the output of a cmdlet/function into an array. You might expect more values but some error made it to return $false, but $false twice in the array might be unlikely in that case.

Or maybe we should wait for Jeffrey Snover to answer here :-)

¹ C:\Windows\System32\WindowsPowerShell\v1.0\Documents\en-US\QuadFold.rtf on my machine