Non-macro biased Select?

[SimonSapin]

#1040 added a select_biased! macro. Some internal functions gained an is_biased: bool parameter to support it, but the non-macro public API around the Select type does not expose this functionality at all. Some of those internal functions are only ever called with false. Biased functionality could be useful to add to the Select type but I’m not sure what the API should look like exactly. ~Doubling the number of methods does not feel great.

For context: I’m building a priority queue on top of an array of crossbeam channels. My receiver should block until any of the inner receivers are ready, but then consume one item from the highest-priority channel rather than arbitrary one. (Starvation is mitigated by "ageing" some low-priority items into a one-level-higher priority channel.) As a work-around I call Select::ready() then an explicit loop with Receiver::try_recv(), but this looks like it does redundant work compared to an hypothetical Select::biased_select()