Why is the compiler not complaining about an additional ',' in Array or Object Initializers?

Question

Using simple type like

class A {
  public int X, Y;
}

with object intializers, one can write

var a = new A { X=0, Y=0 };

But the following is also accepted by the compiler:

var a = new A { X=0, Y=0, }; // notice the additional ','

Same for int[] v = new int[] { 1, 2, };

This looks a bit strange ... Did they forgot to reject the additional ',' in the compiler or is there a deeper meaning behind this?

Answer 1

There isn't anything deep, it's a common thing accepted by compilers of many (but not all) languages. This makes doing lists easier:

var a = new A {
    X = 0,
    Y = 0,
};

When you want to add Z = 0, you don't need to edit the previous line to add a comma. This improves source code control deltas, because there is only one new line instead of one new line and one changed line.

Answer 2

This also simplifies an implementation of code generators. They don't have to check the last comma.