[5.9][Executors] Do not consider Loc validity in determining to emit error/warning about enqueue(_:) #67959
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instead, error if all implementations are "default from stdlib" because end-user MUST implement at least one of them Don't trigger warnings about stdlib itself when user code might trigger them The standard library's enqueue() does not play by the same rules -- we provide "deprecated" implementations in order to remain source/binary compatible, and showing warnings about this when users make mistake will only be misleading.
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@swift-ci please test |
ktoso
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DougGregor
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Aug 16, 2023
ktoso
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Description: The introduction of new protocol requirements in
protocol Executorrequired careful and custom handling by the compiler in order to not break ABI/API. This logic made a wrong assumption that it can rely on valid/invalid source location information to determine if "this decl exists and is valid" -- while in reality, we cannot rely on loc at all for making this decision. This happened to work in tests and swiftpm projects because source location was always available.Symbols may not have valid loc attached just because they're in a different module and we don't have swiftsourceinfo for them. E.g. with Xcode the Archive action does not copy the swiftsourceinfo and thus we end up ALWAYS emitting the error that an implementation is missing -- even if it is there, but we simply trigger the "illegal loc!" case incorrectly.
Solution: Stop relying on the incorrect assumption that a "valid loc" can be used to determine if we have the method or not. This worked by accident, since in swift the unit test suite we entered this missing loc code path.
Instead, we must manually inspect the witnesses and determine that at least one of them is NOT the default implementation provided in the stdlib (because we implement ALL of the requirements in order to introduce the new protocol requirement without breaking API/ABI). The same goes about warnings, since we do not want to emit warnings about the standard library when end-users do something slightly wrong in their adoption -- it is their conformance mistake we must warn about.
Risk: Low
Risk details: The primary error fix is about removing the use of loc information entirely from decision making about emitting errors, i.e. we're removing a buggy source of information from the decision making -- the primary logic all remains the same.
Due to that removal, we also add some warning suppression that previously occurred naturally (correctly "by accident"), by concretely handling the special casing of the concrete extension in
_Concurrencymodule that performs actions we should not warn about in stdlib due to it implementing bin-compat concerns.Reward: Medium,
Reward details: Projects built in a way where
swiftsourceinfois not available (e.g. in Xcode by running "Archive") are now able to adopt libraries that adopted custom executors -- e.g. like Swift NIO. The reward is medium because custom executor adoption in this pattern isn't quite wide-spread yet.Review by: @DougGregor @owenv
Testing: Warnings and errors emitted by this are well tested; We also verified a known reproducer using Xcode and "Archive" action is resolved by a compiler with this fix.
Original PR: #67957
Scope: This is a compiler only change.
Radar: rdar://113913291