Proxy contracts NEED to have some kind of validation

[outdoteth]

At the moment if you try to deploy a proxy contract with an implementation that has invalid structure it will still succeed.
For example this contract will deploy fine:

contract Foo {
  uint public b;
  uint public c = 5;

  constructor(a uint) { 
    b = a; 
  }
}

But this contract is invalid when deployed from a proxy. Because any proxy relaying to this implementation won't have the c or b variables set. I think it should throw an error here if the user tries to deploy this or at least some kind of warning.

[outdoteth]

Also related, is in upgrading proxies - Storage collisions cause non-trivial errors. Obviously, it's harder to verify this because an upgrade could happen at a distant point in the future.

Old implementation:

contract Foo { 
  uint public b = 5;
};

New implementation:

// Incorrect
contract Bar { 
  uint public c; // Collision here! - value is actually set to 5 not 0
}

// Correct
contract Bar {
  uint public b; // value is 5 as expected
  uint public c; // value is 0
}

It would be useful to have a function that checks that the new contract doesn't conflict with the old contracts storage and is a valid proxy upgrade.

// Checks if "Foo" can be upgraded to "Bar"
const isValid = deployments.isValidProxyUpgrade("Foo", "Bar");

OpenZeppelin has a similar check but it is in-built into their deploy function so is of no use here in hardhat-deploy although their verification code can probably be mostly reused (?)

[wighawag]

Definitely wanted :), this was also mentioned here : #65

[wighawag]

closing as duplicate of #65