Type "address[]" not supported for state variable

Question

I have a very strange problem. Many solidity contract examples use address struct types as state variables. But my smart contract:

pragma solidity ^0.4.0;

contract ProductItem {
address[] _owners;
address _currentOwner;
address _nextOwner;
string _productDigest;

function ProductItem(string productDigest) {
    _currentOwner = msg.sender;
    _productDigest = productDigest;
}

function setNextOwner(address nextOwner) returns(bool set) {
    if (_currentOwner != msg.sender) {
        return false;
    }
    _nextOwner = nextOwner;
    return true;
}

function confirmOwnership() returns(bool confirmed) {
    if (_nextOwner != msg.sender) {
        return false;
    }
    _owners.push(_nextOwner);
    _currentOwner = _nextOwner;
    _nextOwner = address(0);
    return true;
}

function getOwner() constant returns(address owner) {
    return _currentOwner;
}

function getOwners() constant returns(address[] owners) {
    return _owners;
}

function getProduct() returns (string product) {
    return _productDigest;
}
}

gives me error in web ide:

Untitled:4:5: Error: Type "address[]" not supported for state variable.
address[] _owners;
^---------------^"

If i ignore this error and try to deploy and call function, e.g. getProduct() it results with null.

Answer 1

I've used the Solidity realtime compiler and runtime connected to a local geth node with version Geth/v1.4.13-stable/linux/go1.5.1 and your code compiles and deploys perfectly.

I have made one change and that is to add constant keyword to the getProduct(...) method as you are not changing any state in this method.

Here is the modified code:

pragma solidity ^0.4.0;

contract ProductItem {
    address[] _owners;
    address _currentOwner;
    address _nextOwner;
    string _productDigest;

    function ProductItem(string productDigest) {
        _currentOwner = msg.sender;
        _productDigest = productDigest;
    }

    function setNextOwner(address nextOwner) returns(bool set) {
        if (_currentOwner != msg.sender) {
           return false;
        }
        _nextOwner = nextOwner;
        return true;
    }

    function confirmOwnership() returns(bool confirmed) {
        if (_nextOwner != msg.sender) {
            return false;
        }
        _owners.push(_nextOwner);
        _currentOwner = _nextOwner;
        _nextOwner = address(0);
        return true;
    }

    function getOwner() constant returns(address owner) {
        return _currentOwner;
    }

    function getOwners() constant returns(address[] owners) {
        return _owners;
    }

    function getProduct() constant returns (string product) {
       return _productDigest;
    }
}

Here is the screen showing the deployment of the modified code, and that the constant method getProduct() returns "ProductOne".