The documentation is missing critical information about error handling. The .removeFirst() method throws a StateError when called on an empty queue. This should be documented, similar to how other methods like .removeAt() document their constraints. Consider adding a note after the syntax section explaining that calling this method on an empty queue will throw a StateError, and optionally provide an example or warning about checking if the queue is empty before calling this method.

The phrase "if it exists" in the introduction is misleading. The .removeFirst() method does not check if an element exists before removing it - it will throw a StateError if the queue is empty. Consider removing "if it exists" from this sentence or rephrasing to clarify the actual behavior, such as: "The .removeFirst() method in Dart removes and returns the first element from a queue."