"Catherine: is there a use for `..." <- Catherine: to expand on this, it would seem that there is the following invariant in the code: "once constructed, a `MatchMatrix` always contains a row of all-`X` at the end" (or, at least, the weaker but equivalent "for every input there always is a case that matches") I hold this belief because the code that constructs the `MatchMatrix` upholds this invariant, and because absent this invariant, this line is unsound: https://github.com/prjunnamed/prjunnamed/blob/6bd37834e29bf3917119817036b576fe4521c6e6/generic/src/decision.rs#L208-L209 however, I'm not entirely sure on this, because some of the tests construct example MatchMatrices that violate this invariant