* better way to define default constructors:
class Point {
num x;
num y;
num z;
// Syntactic sugar for setting z and x before the constructor body runs.
Point(this.z, this.x){...}
}
This is more explicit and flexible than D's way for default struct constructors,
which can only allow to set all fields in order, without skipping some, and
doesn't allow to do anything else in the ctor.

D doesn't allow non-trivial default struct constructors for some good reasons, which are a long discussion we've had many times. These reasons don't apply to javascript.

I don't recall this syntax 'Point(this.z, this.x){...}' ever being discussed; can you please provide a link?

* it avoids the following common bug:

struct Point{int x;int y;}

auto a=Point(1,2,3);

//later on we add a field: struct Point{int x; int a; int y; }

//woops!

* less boilerplate / more DRY / more explicit:

struct Point{

Foo x=32;

Bar y;

Baz z;

this(this.y, this.z){} //instead of this(Bar y, Baz z){this.y=y;this.z=z;}

}

This is arguably a preferable syntax.