Idea: Borrowck Transparent Function Calls

josh: > But for private helper functions, automatically detecting which subsets they use would not necessarily be a maintenance hazard. I strongly believe that the ability to reason just from the function signatures and the better error messages is desirable even for private functions. Which means that this proposal is a maintenance hazard (indirectly), since it makes the code base harder to reason about. The possible impact on compile times doesn't care about private vs public.