Record ForCtorParam MapFrom validation

[killergege]

Source/destination types

    private class Source
    {
        public string         Name     { get; init; }
        public SourceExpenses Expenses { get; init; }
    }

    private class SourceExpenses
    {
        public int Value1 { get; init; }
        public int Value2 { get; init; }
    }

    private record Target(string Name, int Expenses);

Mapping configuration

            CreateMap<Source, Target>(MemberList.Destination)
               .ForCtorParam(nameof(Source.Name), opts => opts.MapFrom(x => x.Name))
               .ForCtorParam(nameof(Source.Expenses), opts => opts.MapFrom((source, _) => source.Expenses.Value1 + source.Expenses.Value2));

Version: 12.0.0

Expected behavior

Mapping works and config.AssertConfigurationIsValid(); does not throw

Actual behavior

Mapping works but config.AssertConfigurationIsValid(); throws.
When fields have the same name but different type, it seems that the validator doesn't detect that the field mapping is overriden and tries to map the source type with the target type.

There is no issue when the Target object is a class, and the mapping is done with ForMember instead of ForCtorParam.

Unhandled exception. AutoMapper.AutoMapperConfigurationException: The following member on Target cannot be mapped: 
    Expenses 
Add a custom mapping expression, ignore, add a custom resolver, or modify the destination type Target.
Context:
    Mapping to member Expenses from Source to Target

Steps to reproduce

Fiddle demo : https://dotnetfiddle.net/WoqHS4

[lbargaoanu]

The message is about the property Expenses, not about the constructor parameter. The record property is init, it matches, and it cannot be mapped. The easy way out is to rename the source property or the constructor parameter. A map from SourceExpenses to int would also work.
For the constructor parameter, the message is
AutoMapper.AutoMapperConfigurationException: The following member on UserQuery+Target cannot be mapped:
Void .ctor(System.String, Int32), parameter expenses

[lbargaoanu]

Record's weirdness aside, I guess if a property is mapped through the constructor, we can skip validating the property itself. You would get a runtime error if you bypass constructor mapping by passing an existing destination.
This new behaviour is in the MyGet build.

[jbogard]

I think that makes sense, but IIRC we've avoided that dual validation because we don't """know""" if a constructor parameter internally sets a property. But it's probably reasonable to make that assumption if the names match.

[lbargaoanu]

We kind of started assuming :) It seems fair. AutoMapper relies on conventions and names are important.