Implement analyzer and code-fixers for DynamicInterfaceCastableImplementation analyzers

[jkoritzinsky]

Implement analyzers and code fixes as per dotnet/runtime#41529

Fixes dotnet/runtime#41529

[codecov]

Codecov Report

Merging #5129 (47fb625) into release/6.0.1xx (ec2f382) will increase coverage by 0.00%.
The diff coverage is 95.98%.

@@                Coverage Diff                 @@
##           release/6.0.1xx    #5129     +/-   ##
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  Coverage            95.61%   95.62%             
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  Files                 1240     1244      +4     
  Lines               285455   286799   +1344     
  Branches             17134    17213     +79     
==================================================
+ Hits                272951   274248   +1297     
- Misses               10193    10232     +39     
- Partials              2311     2319      +8     

[Youssef1313]

else throw NotSupportedException or something that ensures the code path isn't reachable?

[jkoritzinsky]

I think silently falling through here is ok unless the pattern in the repo otherwise is to throw.

[Youssef1313]

Is IDynamicInterfaceCastable is a must to use DynamicInterfaceCastableImplementationAttribute? Any separate analyzer work for that?

[jkoritzinsky]

IDynamicInterfaceCastable is a must-use type related to the DynamicInterfaceCastableImplementationAttribute type. But since IDynamicInterfaceCastable will be implemented by a different type, so there's no analyzer work for that.

[jkoritzinsky]

@dotnet/roslyn-analysis just want to make sure that reviewing this is on the backlog as it's been green in CI and waiting for review for 27 days.

[ryzngard]

Some style problems. In general I think this repo uses var when possible. I marked a few but realized a lot of the same comment would get tedious.

There also may be some missing paths for testing.

[jkoritzinsky]

@sharwell is there an ETA on when this will be reviewed? Last review pass was two weeks ago and the only changes since then were resolving merge conflicts.

[sharwell]

... will conventionally not specify that it implements a 'DynamicInterfaceCastableImplementationAttribute'-attributed type, only the public interface type, virtual interface method lookup will fail even if the method has an implementation ...

I don't understand this wording. Can you suggest a rephrasing to iterate on it?

[jkoritzinsky]

Suggested change

<value>Since a type that implements 'IDynamicInterfaceCastable' will conventionally not specify that it implements a 'DynamicInterfaceCastableImplementationAttribute'-attributed type, only the public interface type, virtual interface method lookup will fail even if the method has an implementation. As a result, all members on 'DynamicInterfaceCastableImplementation'-attributed types should be 'sealed'.</value>

<value>Since a type that implements 'IDynamicInterfaceCastable' will not specify in source or in the `IDynamicInterfaceCastable` implementation that it implements a 'DynamicInterfaceCastableImplementationAttribute'-attributed type, virtual interface method lookup will fail even if the method has an implementation. As a result, all members on 'DynamicInterfaceCastableImplementation'-attributed types should be 'sealed'.</value>

[jkoritzinsky]

CI failure is #5381 and is unrelated to this PR (it's failing in the release/6.0.1xx branch without this change).