// returns: (CtxCase, closing line number)
// or null
static Pair<CtxCase, Int> ctxCase(L<S> lines, int i) {
  new Matches m;
  new CtxCase c;
  while (i <= l(lines) && emptyAfterTrim(get(lines, i))) ++i;
  if (!flexMatch("CASE (*) ACTION", get(lines, i), m, false)) null;
  c.condition = $1;
  
  // TODO: properties

  int closing = indexOfClosingCurlyBracket(lines, i+1);
  c.action = tok_unCurlyBracket(lines(subList(lines, i+1, closing+1)));
  ret pair(c, closing);
}