Separate the lifetimes of each input of OrdMap::diff and OrdSet::diff #168
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This is a breaking change but only for code that uses turbofish syntax on the `diff` method, the `DiffIter` type, or the `DiffItem` type.
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This is a breaking change but only for code that uses turbofish syntax on the
diffmethod, theDiffItertype, or theDiffItemtype.Motivation:
We use
diffin an algorithm that merges two maps similar tounion_with_key, but tries to maximize sharing of internal nodes between similar maps. See "Stage 2" in #166. This works by collecting the results ofdiffinto twoVecs of(key, value)pairs that would need to be inserted in either input map in order to turn it into the desired merge/union. After that is done, we pick the smaller set of updates in order to decide which of the input maps to mutate.At the moment these
Veccontain cloned keys and cloned values. With this PR, they could instead be borrowed with eachVeconly borrowing from one of the two input maps. After we’ve decided whichVecto use, only its contents needs to be cloned for inserting into the mutated map.The full algorithm is at https://foss.heptapod.net/octobus/mercurial-devel/-/commit/53e9ccfaacd492852419cb9dca1abae1765a7474#1e7b6882ee05cf3bc9882ed81b2a0a8dac61ded6_179_182