Can you say more about the problems(s) being solved there? Given all the other feature work that has been done/requested around memoization, tempted to let this work happen in a contrib library first. But that is partially because I don't know from this ticket what pain is being addressed.

Unk may provide a starting point for a contrib lib. https://github.com/fogus/unk

I'm in support of a smarter memoize a la unk; this could be considered a stop-gap measure that helps in situations where the current memoize implementation simply cannot be used due to unbounded memory use.

I've also come across circumstances where I can't use memoize because it will make my function untestable, though admittedly these involve memoizing impure functions—perhaps the answer there is just "don't do that".

Let's do one of the following instead:

• make unk a contrib (after addressing Rich's questions)
• recommend Guava for advanced caching
• make a Guava-wrapping contrib