REQ: Don't throw for a class with member names differing by only by casing

Steps to reproduce

Add-Type -TypeDefinition 'public enum Testing { Yes, yes }'
[Testing] | Get-Member -Static

Expected behavior

Either get both “Yes” members, or just the last one processed. Mainly I’d expect it not to throw.

Actual behavior

Get-Member : The field or property: "yes" for type: "Testing" differs only in letter casing from the field or property: "Yes". The type must be Common Language Specification (CLS) compliant.
At line:1 char:13
+ [Testing] | Get-Member -Static
+             ~~~~~~~~~~~~~~~~~~
+ CategoryInfo          : NotSpecified: (:) [Get-Member], ExtendedTypeSystemException
+ FullyQualifiedErrorId : NotACLSComplaintField,Microsoft.PowerShell.Commands.GetMemberCommand

Environment data

Name                           Value
----                           -----
PSVersion                      7.0.0-preview.2
PSEdition                      Core
GitCommitId                    7.0.0-preview.2
OS                             Microsoft Windows 10.0.18362
Platform                       Win32NT
PSCompatibleVersions           {1.0, 2.0, 3.0, 4.0…}
PSRemotingProtocolVersion      2.3
SerializationVersion           1.1.0.1
WSManStackVersion              3.0

Other

Here’s where it throws in DotNetAdapter.

I ran into this while writing something that uses dnlib. Their MethodAttributes enum has two values for PInvokeImpl (~I’d guess they had the one with the incorrect casing originally and just added one with the right casing as to not break anyone. That’s just a guess though~ Actually looking at the rest, I think it’s because they’re using both the System.Reflection names as well as the EMCA spec names.)

[SteveL-MSFT]

@PowerShell/powershell-committee reviewed this, we propose the following behavior:

• if there is a single member, the casing you provide doesn’t matter and we will continue to match on that member
• if there are two members differing by casing, and you provide casing that matches one of them exactly, we will return that member
• if there are two members differing by casing, and you provide casing that doesn’t match any, then we will return an new error indicating such (nothing about CLS compliance)

[0xd4d]

I think most .NET libraries are not CLS compliant and the reason is simple, most people use C#.

PowerShell shouldn’t throw in this case, it’s fine to say this is undefined behavior as long as it doesn’t throw.