/**
* for calling a function by name()
*/
public Expression createFunction(String name, List<Expression> args) {
Function f = lookup(name);
if (f == null) {
// TODO: typed exception
throw new AuraRuntimeException("No function found for key: " + name, l);
}
return new FunctionCallImpl(f, args == null ? ImmutableList.<Expression> of() : ImmutableList.copyOf(args), l);