Incorrect information on Count/Length properties of an array

[surfingoldelephant]

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Links

https://learn.microsoft.com/en-us/powershell/module/microsoft.powershell.core/about/about_arrays#count-or-length-or-longlength
https://learn.microsoft.com/en-us/powershell/module/microsoft.powershell.core/about/about_arrays#arrays-of-zero-or-one

Summary

In about_arrays, information on Count/Length is either incorrect or misleading. The documentation states:

To determine how many items are in an array, use the Length property or its Count alias.

• An array's Count is not an alias of Length in PS v6+. See the details below.
• Count should not be referred to as an alias. For consistency across different collection types, Count should be recommended as the preferred method to retrieve the number of elements of a collection. See Recommend using Count to retrieve the number of elements in an in-memory collection #11614.

Arrays of zero or one
Beginning in Windows PowerShell 3.0, a collection of zero or one object has the Count and Length properties.
[...]

• I think this section in general could be improved. The section is titled "Arrays of [...]", but the first two examples are for scalars, which is confusing. Perhaps retitle the section and focus it specifically on PS's implicit enumeration and other pipeline semantics that may yield either a scalar or collection result.
• An array, regardless of element count, has a Count and Length that reflects the number of elements.
• Other collection types may only have a Count or a Length or neither. See Incorrect assertion that intrinsic Count/Length properties are available to all collection types #11613.

Details

Count is only added as an ETS AliasProperty to arrays in Windows PowerShell v5.1 or lower. This was due to PS v2's inability to expose explicit interface implementations.

This limitation was addressed in PS v3 and as of PS v6, the AliasProperty is no longer added to the [array] type (it was obsolete and removal of it addressed issues such as PowerShell/PowerShell#3153).

In PS v6+, arrays have a Count property from explicit ICollection implementation.