ReflectionUtils.cs

using System.Reflection;

internal static class ReflectionUtils
{
    public static bool IsVisibleOutsideAssembly(Type type)
    {
        return (type.Attributes & TypeAttributes.VisibilityMask) switch
        {
            TypeAttributes.Public => true,
            TypeAttributes.NestedFamily or TypeAttributes.NestedFamORAssem => IsVisibleOutsideAssembly(type.DeclaringType!),
            _ => false,
        };
    }

    public static bool IsVisibleOutsideAssembly(MethodInfo method, bool assumeDeclaringTypeIsVisibleOutsideAssembly = false)
    {
        return (method.Attributes & MethodAttributes.MemberAccessMask) switch
        {
            MethodAttributes.Public or MethodAttributes.Family or MethodAttributes.FamORAssem =>
                assumeDeclaringTypeIsVisibleOutsideAssembly || IsVisibleOutsideAssembly(method.DeclaringType!),
            _ => false,
        };
    }

    public static bool IsInitOnly(MethodInfo method)
    {
        return method.ReturnParameter.GetRequiredCustomModifiers().Any(m => m.FullName == typeof(IsExternalInit).FullName!);
    }

    public static bool IsReadOnly(MethodInfo method)
    {
        return HasAttribute(method, typeof(IsReadOnlyAttribute).FullName!);
    }

    public static bool IsReadOnly(Type type)
    {
        return HasAttribute(type, typeof(IsReadOnlyAttribute).FullName!);
    }

    private static bool HasAttribute(MemberInfo member, string attributeFullName)
    {
        return member.GetCustomAttributesData().Any(d => d.AttributeType.FullName == attributeFullName);
    }
}