static <A> A requiredPar(ThreadLocal<A> tl) {
  ret assertNotNull(optPar(tl));
}

sO requiredPar(O[] params, S name) {
  O o = optPar(params, name);
  if (o == null) fail("Need " + name);
  ret o;
}

sO mapMethodLike requiredPar(S name, O[] params) {
  ret requiredPar(params, name);
}

Began life as a copy of #1006679