julia

ed338d00 - lattice: Restore `tmerge_fast_path` for optimizer lattice (#50291)

lattice: Restore `tmerge_fast_path` for optimizer lattice (#50291) This function is slightly misnamed, because, while it does perform some fast pathing, the rest of the tmerge functions assume it has been run. When I removed the OptimizerLattice in #50257, we accidentally lost the call to `tmerge_fast_path` in the optimizer_lattice path, regressing tmerge quality in the optimizer (which admittedly we don't use a lot, but I did just add another use for in #50287). The proper fix is probably to split the tmerge into a helper that always calls the fast path and then delegates to the current implementation for everything else, but for now, just try moving the fast path to the start of the PartialsLattice, which should restore correctness and have reasonable performance, since there's only a handful of pointer checks between the entry to the inference tmerge and the partials lattice.