Fix Operation.swift Operation addDependency bug

[dannliu]

In this commit, I only fixed the addDependency bug. However, there is a critical bug https://bugs.swift.org/browse/SR-11333, exists from swift5.0 (I didn't check swift version < 5.0).

I created a test case for OperationQueue and Operation which testing the dependency.

[dannliu]

Everything works fine on the Darwin platform. As the Operation.swift changes so much between swift-5.0 and the current master branch. I guess the Foundation team may have a new design for Operation&OperationQueue and everything is in progress.

[millenomi]

@swift-ci please test and merge

[millenomi]

The new test is segfaulting.

[dannliu]

@millenomi The test case failed as I only fixed the addDependency. For the dependency logic in OperationQueue there is still a bug here which I haven't fixed. You can take a look at SR-11333.

[dannliu]

@swift-ci please test

[dannliu]

@millenomi I updated the test case to only handle the addDependency method. According to SR-11333, is that properly I could work and fix that? However, I am not sure if the foundation team there has already got a plan and overall design for Operation & OperationQueue. Looking forward to get how do you think this.

[millenomi]

The other test uncovered a separate bug that we need to look into.

The design you see is the design we have. (It's very close to the way Darwin's works.) We need to bugfix for sure, and patches are welcome; there's a lot of work and nonobvious behavior that's gone into the Darwin version, and the patches will need to clear a pretty high bar, but if you want to send a PR please do.

[millenomi]

@swift-ci please test and merge

[millenomi]

@swift-ci please test and merge

[millenomi]

@swift-ci please test and merge

[millenomi]

@swift-ci please test and merge