Invalid IL generated for intercepted callsite

[jkotas]

Version Used:

.NET SDK 8.0.100

Steps to Reproduce:

1. dotnet new console
2. Copy & paste attached Program.cs (adjust full path to match your system)
3. Add <InterceptorsPreviewNamespaces>$(InterceptorsPreviewNamespaces);MyInterceptors</InterceptorsPreviewNamespaces to the .csproj file
4. dotnet run

Expected Behavior:

Program runs to completion

Actual Behavior:

InvalidProgramException.

The problem is that Roslyn generates invalid IL

    .locals init (valuetype MyEnum V_0)
    IL_0000:  ldc.i4.1
    IL_0001:  stloc.0
    IL_0002:  ldloc.0 <- MyEnum is not assignable to Enum in IL!
    IL_0003:  call       string MyInterceptors.Interceptors::OtherToString(class [System.Runtime]System.Enum)

Program.cs

using System.Runtime.CompilerServices;

var value = MyEnum.Second;
Console.WriteLine(value.ToString());

public enum MyEnum
{
    First,
    Second,
}

namespace MyInterceptors
{
    public static class Interceptors
    {
        [InterceptsLocation(@"C:\repro\Program.cs", line: 4, column: 25)]
        public static string OtherToString(this System.Enum value)
            => "Wrong Value" + value;
    }
}

namespace System.Runtime.CompilerServices
{
    [AttributeUsage(AttributeTargets.Method, AllowMultiple = true)]
    sealed class InterceptsLocationAttribute : Attribute
    {
        public InterceptsLocationAttribute(string filePath, int line, int column)
        {
        }
    }
}

[jkotas]

Originally reported by @andrewlock in dotnet/runtime#57748 (comment):

[jaredpar]

@RikkiGibson PTAL