# Open Discussion: Upgradable Contracts

*These are collaborative notes from the open discussion round about "Upgradable Contracts" at the [Solidity Summit 2020](https://solidity-summit.ethereum.org/).*

contract c {
  uint a;
  uint b @1;
  uint c @3;
  
  struct X {
      uint a;
      uint b storageoffset 2;
  }
}

contract c {
  uint a;
  addedlater {
    uint b;
    uint c;
  }
  
  struct X {
      uint a;
      addedlater {
        uint b;
      }
  }
}

@id("some_name") 
contract c {
  @id("some_variable")
  uint a;
  uint b;
  uint c;
  
  @id("some_struct")
  struct X {
      uint a;
  }
}

https://github.com/ethereum/solidity/issues/597#issuecomment-392107980 suggested something like "modifiers":

uint a storage("some_variable");

https://github.com/ethereum/solidity/issues/597#issuecomment-406582568 suggested sections/namespaces:

contract MyContract {
  storage("some-collection") {
    uint foo;
    uint bar;
  }

  storage("other-collection") {
    mapping (uint => bool) qux;
    MyStruct baz;
  }
}

## Constructors

**TODO**: Create an issue on this

How to pass a constructor code to the proxy?
- Generate constructor as compiler output
- Note that it's not possible to grab the constructor bytecode from the deployBytecode since the ctor argument positions are hardcoded, so a different-length runtime code would yield differ
- Allow on-chain to define the constructor code
- Support on-chain factory that can create a proxy and run the constructor code from a different implementation