in reply to
Re^3: How will you use state declared variables in Perl6?
in thread How will you use state declared variables in Perl6?
That's currently specced as "is cached" though I don't believe it's implemented yet. However, even after it's implemented, it's not going to be smart enough from the type signature to know whether an incoming parameter is sparse or dense, and for something like fibonacci an array is going to provide a faster memo cache than a hash is. Maybe the memoizing code can be smart enough to figure that out heuristically, but that's not a sure thing at this point.