static <A> A assertEqualsVerbose(O x, A y) {
  assertEqualsVerbose((S) null, x, y);
  ret y;
}

// x = expected, y = actual
static <A> A assertEqualsVerbose(S msg, O x, A y) {
  if (!eq(x, y)) {
    ifdef assertEqualsVerbose_advancedDiff
    if (x instanceof S && y instanceof S && (containsNewLine((S) x) || containsNewLine((S) y)))
      nlPrintNL(unidiff((S) x, (S) y));
    endifdef

    fail((nempty(msg) ? msg + ": " : "") + "expected: "+ x + ", got: " + y);
  } else
    print("OK" + (empty(msg) ? "" : " " + msg) + ": " + /*sfu*/(x));
  ret y;
}

ifclass Scorer
static void assertEqualsVerbose(Scorer scorer, S msg default "", O x, O y) {
  if (scorer == null) ret with assertEqualsVerbose(x, y);
  if (!eq(x, y)) {
    print(appendColonIfNempty(msg) + y + " != " + x);
    scorer.add(false);
  } else {
    print("OK: " + appendColonIfNempty(msg) + x);
    scorer.add(true);
  }
}
endif

Began life as a copy of #1001055