scala.tools.nsc.transform.patmat.MatchApproximation.MatchApproximator.TreeMakersToProps
apply itself must render a faithful representation of the TreeMaker
apply itself must render a faithful representation of the TreeMaker
Concretely, True must only be used to represent a TreeMaker that is sure to match and that does not do any computation at all e.g., doCSE relies on apply itself being sound in this sense (since it drops TreeMakers that are approximated to True -- SI-6077)
handleUnknown may be customized by the caller to approximate further
TODO: don't ignore outer-checks