https://github.com/dotnet/coreclr/issues/17980

app.csproj

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFramework>netcoreapp2.1</TargetFramework>
    <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
  </PropertyGroup>
  <ItemGroup>
    <PackageReference Include="System.Runtime.CompilerServices.Unsafe" Version="4.5.0-rc1" />
  </ItemGroup>
</Project>

Program.cs

using System;
using System.Runtime.InteropServices;
using System.Runtime.CompilerServices;

struct MethodDesc
{
    const ushort enum_flag3_TokenRemainderMask = 0x3FFF;

    static readonly int ALIGNMENT_SHIFT = 3;
    static readonly int ALIGNMENT = (1<<ALIGNMENT_SHIFT);

    ushort m_wFlags3AndTokenRemainder;

    byte m_chunkIndex;

    byte m_bFlags2;

    ushort m_wSlotNumber;

    ushort m_wFlags;

    public unsafe int GetMemberDef()
    {
        MethodDescChunk *pChunk = GetMethodDescChunk();
        ushort tokrange = pChunk->GetTokRange();

        ushort tokremainder = (ushort)(m_wFlags3AndTokenRemainder & enum_flag3_TokenRemainderMask);

        return MergeToken(tokrange, tokremainder);
    }

    unsafe MethodDescChunk* GetMethodDescChunk()
    {
        return
            (MethodDescChunk*)((IntPtr)Unsafe.AsPointer(ref this) -
                            (sizeof(MethodDescChunk) + (GetMethodDescIndex() * MethodDesc.ALIGNMENT)));
    }

    int GetMethodDescIndex()
    {
        return m_chunkIndex;
    }

    const int METHOD_TOKEN_REMAINDER_BIT_COUNT = 14;

    int MergeToken(ushort tokrange, ushort tokremainder)
    {
        return (tokrange << METHOD_TOKEN_REMAINDER_BIT_COUNT) | tokremainder | mdtMethodDef;
    }

    const int mdtMethodDef = 0x06000000;
}

struct MethodDescChunk
{
    const ushort enum_flag_TokenRangeMask = 0x03FF;

    IntPtr m_methodTable;

    IntPtr m_next;

    byte m_size;
    byte m_count;
    ushort m_flagsAndTokenRange;

    public ushort GetTokRange()
    {
        return (ushort)(m_flagsAndTokenRange & enum_flag_TokenRangeMask);
    }
}

class Program
{
    static unsafe void Main()
    {
        var mi = typeof(Console).GetMethod("WriteLine", Type.EmptyTypes);

        var methodDesc = (MethodDesc*)mi.MethodHandle.Value;

        int token = methodDesc->GetMemberDef();
        Console.WriteLine("{0:X8}", token);

        Console.WriteLine(mi.Module.ResolveMethod(token));
    }
}