Add a resolved/compatible service parameter to decorator resolutions.

[tillig]

Resolves #1330.

When...

• An open generic is registered and exposes two services (IServiceA and IServiceB).
• An open generic decorator is registered against one of those services (IServiceB).
• The open generic is resolved against the other service (IServiceA).

...then, while the underlying component should be decorated, when the decorator is created it sees that "the wrong service" is being resolved so it, instead, attempts to execute a separate resolution operation. This can result in resolving the wrong type.

The solution proposed here adds both a TypedParameter (for "exact match" support, used by lambda-registered decorators and ensuring backwards-compatibility with existing code) and a ResolvedParameter. The new ResolvedParameter checks to see if the target decorator parameter is type compatible instead of type equal so the instance being decorated will end up getting used.

This does open up a potential edge case bug where a decorator could technically take both an IServiceA and an IServiceB and the new behavior will use the decorated instance as both parameters instead of using it for one parameter and resolving the other from the container.

If we could reverse-lookup the service being resolved back to the original component and then enumerate all of the exposed services from there, it would be a more 100% precise match, but it would also be a bit more expensive and, given the time I had, I couldn't figure out how to do that. :)

The failing test here is added directly from #1330.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 78.60%. Comparing base (488294e) to head (caa3e04).
Report is 4 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #1424      +/-   ##
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+ Coverage    78.58%   78.60%   +0.01%     
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  Files          200      200              
  Lines         5716     5720       +4     
  Branches      1168     1168              
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+ Hits          4492     4496       +4     
  Misses         712      712              
  Partials       512      512              

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[alistairjevans]

Looks good; this decorator stuff only gets more complicated! 😂