code: Expr ternary() {
  		Expr cond = or();
  		if (peek().sym == Sym.QUESTION) {
  			move();
  			Expr exprOne = expr();
  			match(Sym.COLON);
  			return new Ternary(cond, exprOne, expr(), location);
  		}
  		return cond;
  	}
docs: ternary : expr '?' expr ':' expr