Element.requireElementById

SomeElementType requireElementById(SomeElementType =  Element)(string id,  string file =  __FILE__,  size_t line =  __LINE__) if(
		 is(SomeElementType :  Element)
	)

Calls getElementById, but throws instead of returning null if the element is not found. You can also ask for a specific subclass of Element to dynamically cast to, which also throws if it cannot be done.