Describe the Bug

The 'RequiresUnreferencedCodeAttribute' should be internal. When targeting .NET 4.6.2 and using the Polyfill package this causes compile errors.

Steps to Reproduce

Create a project which targets .NET 4.6.2 and Reference Autofac and Polyfill.

using System;
using System.Diagnostics.CodeAnalysis;

[RequiresUnreferencedCode("Requires unreferenced code.")]		
public class Test
{
}

Expected Behavior

The code should compile.

Autofac: 8.3.0