catch-all-with-variable trick needs some clarification

[ac2epsilon]

I suggest adding a note about control structures-match-using default value

• Using variable bindings, you have to keep in mind, that any form of catch-all effectively breaks the matching chain. Some systems provide lookup for the most specific matches, but Scala's match does not. This error is easier to catch in the case of underscore placeholder but can be easily missed for var bindings. Especially if you suppress or ignore (not dive in) compiler warnings. This notch is a regular source of bad mistakes:

val i = 5
val day = i match
  case 0 => "Sunday"
  case 1 => "Monday"
  case 2 => "Tuesday"
  case 3 => "Wednesday"
  case what => "Guesswho"
  case 4 => "Thursday"
  case 5 => "Friday"
  case 6 => "Saturday"

println(day)

Guesswho

[som-snytt]

At least it warns that subsequent cases are unreachable, but it's nice to warn the user that it will warn. The warning is not necessarily friendly.