Do not allow Any to satisfy more specific same-type constraints.

[rudkx]

What's in this pull request?

Fix an issue where an associated type inferred to be Any is allowed to satisfy all same-type constraints on types.

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For associated types inferred to be Any, we were allowing the type to
satisfy more specific same-type constraints, e.g. Element ==
Character (where Element is the associated type). This is clearly wrong.

The fix here is very specific to empty protocol compositions, and
removes some code in matchTypes() that doesn't make a lot of
sense. Looking back at the history, this was added in a commit that made
a handful of other changes, and it's not clear this particular change
was important for the issues that commit claimed to fix (and in fact
removing this regresses no tests).

Fixes rdar://problem/27515965.

[rudkx]

@swift-ci Test.

[rudkx]

@DougGregor Doug - can you take a look? I'm not 100% confident that deleting this code is the best fix (e.g. there might be something else going on that means we shouldn't even reach here), but we don't have any tests that expect the current behavior, and the current code doesn't make a lot of sense in context.

[DougGregor]

This looks like the right fix. I don't know what that code was trying to accomplish, but after you change the SelfObjectOfProtocol constraint kind appears to be dead!

[rudkx]

Thanks!

[rudkx]

I cannot seem to merge this.

@tkremenek Ted, it seems like something is going on with PR testing where it appears to start the tests when you create the PR, but the tests never run, and then in some cases (like this one) it's blocking the merge. Perhaps because I did the full test run rather than smoke tests?

[gottesmm]

@rudkx That is what is happening. This is a known issue. @shahmishal is working on fixing the issue by having the test/merge and the normal test API to set the smoke test values to true. I just think that he needs to finish testing it.

[jckarter]

@rudkx Thanks!