AssertConfigurationIsValid fails after upgrade to 8.0

Code working using version 7.0.1 fails with exception after upgrade to 8.0. Mapping was using resolver with ResolveUsing which is now changed to MapFrom. AssertConfigurationIsValid seems to not see the mapping. (I dont think my usage is one that is called out by the upgrade guide as a breaking case, and looks to be as shown in documentation - http://docs.automapper.org/en/latest/Custom-value-resolvers.html). I tried with a converter instead of a resolver with same results.

Source/destination types

public class DoctorViewModel
{
    public string FirstName { get; set; }
    ...
}

public class DoctorDetailViewModel : DoctorViewModel
{
    public List<int> DoctorSpecialties { get; set; }
    ...
}

public class Doctor 
{
    public string FirstName { get; set; }
    public ICollection<DoctorSpecialty> DoctorSpecialties { get; set; }
    ...
}

public class DoctorSpecialty
{
    public int SpecialtyId { get; set; }
    ...
}

Mapping configuration

// Using Resolver shown, same failure using converter
CreateMap<DoctorDetailViewModel, Doctor>(MemberList.Source)
    .ForMember(dest => dest.DoctorSpecialties, opt => opt.MapFrom<SpecialtyFromIdResolver>());
	
private class SpecialtyFromIdResolver : IValueResolver<DoctorDetailViewModel, Doctor, ICollection<DoctorSpecialty>>
{
    ICollection<DoctorSpecialty> IValueResolver<DoctorDetailViewModel, Doctor, ICollection<DoctorSpecialty>>.Resolve(DoctorDetailViewModel source, Doctor destination, ICollection<DoctorSpecialty> destMember, ResolutionContext context)
    {
        List<DoctorSpecialty> specialties = new List<DoctorSpecialty>();
        source.DoctorSpecialties?.ForEach(s => specialties.Add(new DoctorSpecialty() { SpecialtyId = s }));
        return specialties;
    }
}

Version: 8.0.0

Expected behavior

Configuration and mapping should succeed as expected as it does using 7.0.1

Actual behavior

Get exception:

{AutoMapper.AutoMapperConfigurationException: The following property on Doctor cannot be mapped: 
	DoctorSpecialties 
Add a custom mapping expression, ignore, add a custom resolver, or modify the destination type Doctor.
Context:
	Mapping to property DoctorSpecialties from DoctorDetailViewModel to Doctor
Exception of type 'AutoMapper.AutoMapperConfigurationException' was thrown.
   at AutoMapper.ConfigurationValidator.DryRunTypeMap(ICollection`1 typeMapsChecked, TypePair types, TypeMap typeMap, PropertyMap propertyMap) in C:\projects\automapper\src\AutoMapper\ConfigurationValidator.cs:line 97}

Steps to reproduce

Mapper.AssertConfigurationIsValid();

[jonsagara]

Thanks!

[lbargaoanu]

@jonsagara You can workaround it by not using a class for your resolver.