Why can I not bind a DynamicMethod to a struct instance?
struct A { }
... //then some where in code::
Func<Type> f = CodeGen.CreateDelegate<Func<Type>>(il=>
    il.ldarga_s(0)
    .constrained(typeof(A))
    .callvirt(typeof(object).GetMethod("GetType"))
    .ret(),
    name:"Constrained",
    target:new A()
);

public static class CodeGen
{
    public static TDelegate CreateDelegate<TDelegate>(Action<ILGenerator> genFunc, string name = "", object target = null, bool restrictedSkipVisibility = false)
        where TDelegate:class
    {
        ArgumentValidator.AssertGenericIsDelegateType(() => typeof(TDelegate));
        ArgumentValidator.AssertIsNotNull(() => genFunc);

        var invokeMethod = typeof(TDelegate).GetMethod("Invoke");
        var @params = invokeMethod.GetParameters();
        var paramTypes = new Type[@params.Length + 1];
        paramTypes[0] = target == null ? typeof(object) : target.GetType();
        @params.ConvertAll(p => p.ParameterType)
            .CopyTo(paramTypes, 1);
        var method = new DynamicMethod(name ?? string.Empty, invokeMethod.ReturnType, paramTypes, restrictedSkipVisibility);
        genFunc(method.GetILGenerator());

        return method.CreateDelegate<TDelegate>(target);
    }
}