src/vs/workbench/common/editor/editorGroupModel.ts/isGroupEditorMoveEvent
export function isGroupEditorMoveEvent(e: IGroupModelChangeEvent): e is IGroupEditorMoveEvent {
	const candidate = e as IGroupEditorMoveEvent;

	return candidate.kind === GroupModelChangeKind.EDITOR_MOVE && candidate.editorIndex !== undefined && candidate.oldEditorIndex !== undefined;
}