Program.cs

void Main()
{
	var config = new MapperConfiguration(expression =>
	{
		expression.CreateMap<C, C>().ReverseMap(); // works
		expression.CreateMap<D, D>(); // stackoverflows
	});
	var mapper = config.CreateMapper();
}

private class C
{
	public string A { get; set; }
}

private class D
{
	public E? Bar { get; set; }
}

private class E : IEnumerable<E>
{
	public IEnumerator<E> GetEnumerator()
	{
		throw new NotImplementedException();
	}

	IEnumerator IEnumerable.GetEnumerator()
	{
		throw new NotImplementedException();
	}
}