new feature: unusable parameters warning

Problem to be solved

PowerShell (theoretically) supports parameters whose name can consist only from numbers. For example, this is a valid declaration:

function p1([switch]$1) {if ($1) {'Yes'} else {'No'}}

However, it is very hard to call properly this script. This one will not work:

PS /home/iiric> p1
No
PS /home/iiric> p1 -1
No

This is because parser will think -1 is a negative number rather than a parameter name in this instance.

Proper (=hard) way would be to use splatting.

$params = @{ '1' = $true }
PS> p1 @params
Yes

Generally, this is not the only example of such unusable parameters. See response by @vexx32 in PowerShell repo issue.

Summary of the new feature

Create a PSSA rule that warns when such parameters are created, so users are aware ahead of time that they're making parameters that they won't be able to refer to.

Start by reviewing existing PSScriptAnalyzer rules and how they report diagnostics, then examine the linked PowerShell issue for the cases considered unusable. Done means the analyzer warns when a parameter cannot be referred to normally, including a numeric-only parameter such as $1.