code: func IsUnspendable(pkScript []byte) bool {
  	pops, err := parseScript(pkScript)
  	if err != nil {
  		return true
  	}
  
  	return len(pops) > 0 && pops[0].opcode.value == OP_RETURN
  }
docs: // IsUnspendable returns whether the passed public key script is unspendable, or
  // guaranteed to fail at execution.  This allows inputs to be pruned instantly
  // when entering the UTXO set.