src/vs/editor/contrib/snippet/snippetParser.ts/Marker/appendChild
class Marker:	appendChild(child: Marker): this {
		if (child instanceof Text && this._children[this._children.length - 1] instanceof Text) {
			// this and previous child are text -> merge them
			(<Text>this._children[this._children.length - 1]).value += child.value;
		} else {
			// normal adoption of child
			child.parent = this;
			this._children.push(child);
		}
		return this;
	}