_size private property is not incremented in add w/ index in native CopyOnWriteList

[LouisCAD]

In the CopyOnWriteList class for Kotlin/Native, the _ size private property is incremented in the add(element: E): Boolean function on line 16:

kotlinx.coroutines/kotlinx-coroutines-core/native/src/internal/CopyOnWriteList.kt

Lines 13 to 19 in 7acaae6

	override fun add(element: E): Boolean {
	val newSize = if (_size == array.size) array.size * 2 else array.size
	val update = array.copyOf(newSize)
	update[_size++] = element
	array = update
	return true
	}

but it is not in the add(index: Int, element: E) function:

kotlinx.coroutines/kotlinx-coroutines-core/native/src/internal/CopyOnWriteList.kt

Lines 21 to 28 in 7acaae6

	override fun add(index: Int, element: E) {
	rangeCheck(index)
	val update = arrayOfNulls<Any?>(if (array.size == _size) array.size * 2 else array.size)
	arraycopy(array, 0, update, 0, index)
	update[index] = element
	arraycopy(array, index, update, index + 1, _size - index + 1)
	array = update
	}

I believe this is a bug.

[LouisCAD]

Note that this can't have caused bugs in consumers since the only usage of this class fortunately stays internal to the library (private property subscribers in ArrayBroadcastChannel) and doesn't use add(index: Int, element: E), but only add(element: E) which doesn't have the bug.

I think that still deserves fixing though since people might copy paste CopyOnWriteList into their projects thinking/hoing it's a bug-free array based MutableList implementation suitable for Kotlin/Native.

That's why I submitted PR #1308.