Allow contract's public state variable to implement interface function

[fulldecent]

Test case

pragma solidity ^0.4.19;

interface I {
    function bob() external returns (int);
}

contract C is I {
    int public bob;
}

Current outcome

This contract does not implement all functions and thus cannot be created.

Expected outcome

Compiles successfully

Discussion

Getter functions are defined in the documentation at http://solidity.readthedocs.io/en/develop/contracts.html#visibility-and-getters:

The compiler automatically creates getter functions for all public state variables.

In contract C, the implicit function function bob() external returns (int); is generated for the public variable int public bob;. Therefore the contract should be a valid implementation of the interface.

---

References:

• This issue is the opposite of Allow public constants in interfaces #3411

[chriseth]

I fear we need a centralized point where we discuss how function inheritance is supposed to work in the future.

[fulldecent]

Good point. In the Swift Evolution process, this would call for a manifesto. We could call it the Inheritance Manifesto. This would document what is going changing, the motivation and how to make the new behavior self-consistent.

If would like me to do this, maybe we could have a quick phone call. This will let me understand what type of end product would be accepted.

[axic]

Well as a first step we should collect all the relevant issue numbers in one place. There are probably close to 10 issues talking about different facets of inheritance.

[fulldecent]

RUNNING TALLY:

• Solidity Issue Inheritance: allow stricter mutability #3412 -- Implement Interface: Allow Stricter Mutability. Inheritance: allow stricter mutability #3412

• Solidity Issue Interfaces can't inherit #3419 -- Interfaces Can't Inherit. Interfaces can't inherit #3419

• to add more

[chriseth]

@fulldecent I created a project https://github.com/ethereum/solidity/projects/9 - not sure if you can add items there, but if you tell me, I will add them.

[chriseth]

Also created umbrella issue: #3698

[superduck35]

Interested to know the status of this as I seem to be getting some inconsistent behaviour between ~0.4.24 and 0.5.xx

[fulldecent]

@alsco77 This discussion is now rolled into #3729

This issue can be closed when the conclusion is reached, wherever that discussion happens.

[chriseth]

Implemented in #7839