Prior Art would take care of that if Apple had not gotten a patent on Optional Chaining (the Google patents page for US9952841B2, which was the only result I could find for the number given by @ebup, reads to me more like the whole concept of Swift, but I may be misunderstanding).
From a quick search (IANAL, also not from US, so salt to taste), I could also not find a consensus on whether the patent grant in the Apache license extended to derivative works and unrelated works. This StackExchange answer makes it sound like it does not, which as I read it could mean that Apple could still require a patent license if another project wanted to incorporate Optional Chaining.
Here is the patent grant section of the license:
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