`IsExtensionMethod` returns false for C# 14 extension method

[sbomer]

This is using:

<MicrosoftCodeAnalysisPackageVersion>5.0.0-2.25414.103</MicrosoftCodeAnalysisPackageVersion>

I assume it should return true instead, right?

    public static class Extensions
    {
        extension(Type type)
        {
            public void ExtensionMethodMismatch() => type.RequiresPublicMethods();
        }
    }

[RikkiGibson]

Related: #78567

I didn't see any discussion of this existing API in the linked issue. @jcouv was there an explicit design decision made about this?

[jcouv]

This behavior is expected. There are two symbols: one for the new extension method, which is a regular method in a container marked with IsExtension, and another for it's corresponding implementation method, which is a classic extension method (ie. has IsExtensionMethod).

[RikkiGibson]

Is there any "AssociatedSymbol" or similar public API which connects the "implementation method" with the new extension method?

[jcouv]

We have an internal API linking extension method/accessor/operator to the implementation method: TryGetCorrespondingExtensionImplementationMethod. If there's a confirmed need, we can discuss how to expose this information publicly.