!7

//!include #1010605 // WeakHashMap2

sclass Symbol {
  S text;
  
  *() {}
  *(S *text, bool dummy) {} // weird signature to prevent accidental calling
  
  public int hashCode() { ret hashCode(text); }
}

static new WeakHashMap<Symbol, Bool> symbolMap;

static Symbol symbol(S s) {
  synchronized(symbolMap) {
    Symbol test = Symbol(s, true);
    //WeakHashMap2.Entry<Symbol, Bool> e = symbolMap.getEntry(test);
    //Symbol sym = e == null ? null : e.get();
    O e = call(symbolMap, 'getEntry, test);
    Symbol sym = cast callOpt(e, 'get);
    if (sym == null)
      symbolMap.put(sym = test, Bool.TRUE);
    ret sym;
  }
}

p {
  Symbol a = symbol("a");
}