rat.Result.R because annoying, but we need itAs annoying as it is to pass the r []rune reference to Result{R:r} in every CheckFunc it saves us from bigger annoyances later, like having a result become decoupled from the parent results to which it belonged.
For example, say we create a filter function that walks the results tree to find only the single result that had a specific tag — a very likely use case. That returned result would lose the R []rune to which the B and E refer. At that point the user of the rat package would have to tape together the slice that was passed into the result in order to produce a valuable marshaling of that result tree. No result tree is worth anything without containing the data to which the pointer results associate.
So crisis averted, R MUST be assigned by ever CheckFunc (or it’s simply not qualified to be a CheckFunc). It would be too much to assert that any CheckFunc or Rule passed to Pack fulfilled this (although technically possible) but having a utility function to validate this might be nice for those writing tests.