julia

e9762065 - allow external lattice to provide its own field-merge implementation (#47910)

allow external lattice to provide its own field-merge implementation (#47910) When merging `PartialStruct`, we are currently merging their fields a bit aggressively (#44404) in order to accelerate (or rather, guarantee) convergence. However, when `PartialStruct` wraps external lattice elements, this can be too aggressive since it does not use `tmerge(𝕃, fields...)` recursively and thus the external lattice elements are not merged as expected. This commit adds an additional lattice hook, `tmerge_field`, inside `tmerge(::PartialsLattice)` so that external lattice implementation can provide its own field-merge strategies.