code: private Identifier parseLifetime(EnclosingScope scope, boolean terminated) {
  		Identifier id = parseOptionalLifetimeIdentifier(scope, terminated);
  		if (id != null) {
  			return id;
  		} else {
  			syntaxError("expecting lifetime identifier", tokens.get(index));
  		}
  		throw new RuntimeException("deadcode"); // dead-code
  	}
docs: Parse a currently declared lifetime.
  
  @return the matched lifetime name