Fix internal compiler error for unimplemented base contract function.

[anurag-git]

Description

This pull request fixes the internal compiler error for super function by ignoring the super functions which doesn't have implementation.

Checklist

• Code compiles correctly
• All tests are passing
• New tests have been created which fail without the change (if possible)
• README / documentation was extended, if necessary
• Changelog entry (if change is visible to the user)
• Used meaningful commit messages

Fixes #5130

[codecov]

Codecov Report

Merging #5558 into develop will decrease coverage by 59.17%.
The diff coverage is 100%.

@@             Coverage Diff              @@
##           develop    #5558       +/-   ##
============================================
- Coverage    88.13%   28.96%   -59.18%     
============================================
  Files          321      321               
  Lines        31721    31557      -164     
  Branches      3810     3811        +1     
============================================
- Hits         27957     9139    -18818     
- Misses        2479    21729    +19250     
+ Partials      1285      689      -596

Flag	Coverage Δ
#all	?
#syntax	28.96% <100%> (ø)	⬆️

[chriseth]

This bug might prompt to re-think the whole super-concept here. Consider the following contracts:

contract A {
    uint x;
    function f() public;
}
contract B is A {
    function f() public {
        super.f();
        x++;
    }
}
contract C is A {
    function f() public {
        x++;
    }
}
contract D is B, C {
}
contract E is C, B {
}

[anurag-git]

This seems to be classic diamond problem

[chriseth]

@anurag-git no, the diamond problem is solved. The problem is that super is a static type when it actually should not.

[anurag-git]

@chriseth, So we need to fix something as part of this PR, or take this issue separately

[chriseth]

Actually having thought about it, it does make sense to only allow the user of super if there is an implementation.

[chriseth]

I will rebase and add another test.