CS1584, CS1658 produced on cref to method with function pointer parameter

[AArnott]

Version Used: VS 16.9 Preview 4 (30912.315.main)

C# apparently cannot take a cref to a method where the full signature is specified if the signature contains a function pointer type.
Note that C# will even suggest via completion the syntax that then produces two warnings.

Steps to Reproduce:

Sharplab

using System;
class PInvoke
{
    /// <inheritdoc cref = "X(delegate* unmanaged[Stdcall]{void*, void*, int})"/>
    internal static unsafe int Y() => throw new NotImplementedException();

    internal static unsafe int X(delegate* unmanaged[Stdcall]<void*, void*, int> IfCallback) => throw new NotImplementedException();
}

Expected Behavior:

No warnings

Actual Behavior:

Severity	Code	Description	Project	File	Line
Warning	CS1658	) expected. See also error CS1026.	GenerationSandbox.Tests (net472), GenerationSandbox.Tests (net5.0), GenerationSandbox.Tests (netcoreapp3.1)	D:\git\CsWin32\test\GenerationSandbox.Tests\Exp.cs	25
Warning	CS1584	XML comment has syntactically incorrect cref attribute 'X(delegate* unmanaged[Stdcall]{void*, void*, int})'	GenerationSandbox.Tests (net472), GenerationSandbox.Tests (net5.0), GenerationSandbox.Tests (netcoreapp3.1)	D:\git\CsWin32\test\GenerationSandbox.Tests\Exp.cs	25

[svick]

I think this is a duplicate of #48363.

[jaredpar]

Agree that looks like a dupe. That had fallen off my radar though. Got it properly triaged and closing this out as a dupe of it.