Constructor selection in reverse mode

[petrnymsa]

Is your feature request related to a problem? Please describe.

When defining mapping with reverse flag, it is not clear how "constructor" parameter is used. Consider following classes

class Source {
   final int a;
   final int b;
   
   Source(this.a, this.b);
}

class Target {
   final int a;
   final int b;

   Target(this.a, this.b);

   Target.extra(int a) => Source(a, a *2);
}

// Mapping

MapType<Source, Target>(
  constructor: 'extra',
  reverse: true
)

This mapping will generate warning

Couldn't find constructor 'extra', fall-backing to using the most fitted one instead. (Target → Source)

Which is understandable but at first might seem confusing.

Describe the solution you'd like
We can introduce reverseConstructor param which will be used in reverse mode.

• No constructor and no reverseContructor = standard constructor selection strategy
• Only constructor = use in both way
• Only reverseContructor = Source -> Target uses selection strategy, Target - Source specific contructor
• constructor and reverseContructor = each way has defined preferred constructor