`nameof` doesn't work with extension properties

[ds5678]

Version Used:

Visual Studio 17.14.0 Preview 7.0

Steps to Reproduce:

internal static class Extensions
{
    extension (object)
    {
        public static string Name => nameof(Name);
    }
}

Diagnostic Id:

CS0103: The name 'Name' does not exist in the current context

Expected Behavior:

I expect it to compile and return "Name";

Actual Behavior:

Only nameof(get_Name) compiles.

[jcouv]

From discussion with extensions WG last week, this behavior is expected. You can't refer to extension members by simple name.
This scenario will be allowed with nameof(object.Name), although that's not working yet.
I'll keep this issue open until then.

[jcouv]

From latest discussion in LDM, we decided to block this scenario until we can find a satisfactory design:
https://github.com/dotnet/csharplang/blob/main/meetings/2025/LDM-2025-06-11.md#nameof
This may not be in .NET 10.

In the meantime, PR dotnet/roslyn#79021 adds that a dedicated error

[jcouv]

Closing as by-design for C# 14