Let's consider a simple class declared within a script:

class foo{
  foo(){
    //...
  }
}

I can create its instances in both of these two ways:

foo foo1();
foo foo2;

Now let's consider a similar class, but give its constructor a parameter that can have a default value:

class foo{
  foo(int bar=0){
    //...
  }
}

This will still be valid:

foo foo1();

But the other line will return an error:

ERR : No default constructor for object of type 'foo'.

This error will also appear in various other cases such as trying to create a temporary copy of an object. I think that constructors which can be called with no parameters should be treated as default constructors.

I'm almost entirely convinced that if somebody creates a constructor that can be called without any arguments, their intention is making it a default constructor. I was trying to imagine a case in which this could generate problems but I'm unable to. I'm pretty sure a constructor whose all arguments have default values should overtake all functions of a default constructor including creating temporary objects, even if only because creating a proper default constructor would become impossible due to a "multiple matching signatures" error. I'm not as experienced programmer and I won't be surprised if I had overlooked some downside of this solution so if you could explain why exactly it sounds like a bad idea, I would be thankful.