`CreateMissingTypeMaps` doesn't work for destination object if source and destination types are the same

Source/destination types

class A
{
    public string X { get; set; }
}

class B
{
    public string X { get; set; }
}

Mapping configuration

var config = new MapperConfiguration(cfg => cfg.CreateMissingTypeMaps = true)

Version: 5.1.1

Expected behavior

I pass an existing object to be filled. The type of source and destination objects are the same. I expect the destination object to be filled.

Actual behavior

The destination object is not filled. If I use a different destination type, it works fine. If I create a new object of the same type, it also works fine.

Steps to reproduce

var config = new MapperConfiguration(cfg => cfg.CreateMissingTypeMaps = true);
var mapper = config.CreateMapper();
var a1 = new A { X = "sample" };
var a2 = new A();
mapper.Map(a1, a2); // a2.X was not set, looks like a bug
var a3 = mapper.Map<A>(a1); // a3.X is set, ok

var b = new B();
mapper.Map(a1, b); // b.X is set, ok

[llRandom]

I still don’t understand, is it some design limitation that blocks from implementing it or is there a logical reason why this particular case should not be supported?

[lock[bot]]

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