When diagnosing a concurrency-unsafe global or static variable, provide
Fix-Its with specific guidance and advice. This is intended to aid the
workflow for folks enabling strict concurrency checking or Swift 6.
There are up to three Fix-Its attached to a diagnostic about
concurrency-unsafe global/static variables:
* convert 'global' to a 'let' constant to make the shared state
immutable, which replaces `var` with `let`
* restrict 'global' to the main actor if it will only be accessed from the
main thread, which adds `@MainActor`
* unsafely mark %0 as concurrency-safe if all accesses are protected
by an external synchronization mechanism, which adds `nonisolated(unsafe)`
I fretted over two things before deciding on this path:
1. For the second note, the reality is that any global actor will
suffice, but `@MainActor` is orders of magnitude more common than any
other global actor, so "common case convenience" wins over "precise
but less useful.
2. For the third note, `nonisolated(unsafe)` should only be used
sparingly, and surfacing it via Fix-It could cause overuse. However,
developers need to know about it, and this is how we do that. It comes
last in the list of notes (after the better options) and says "unsafe"
in not one but two places.
When a retroactive conformance to a protocol that inherits from `Sendable`
introduces an implicit `Sendable` conformance, allow `@preconcurrency`
to suppress the diagnostic about the `Sendable` conformance being
introduced outside of the original source file.
Fixes rdar://125080066.
When determining whether a non-sendable type is a nominal type that is
affected by `@preconcurrency`, be sure to look at the specific type
even when it's part of larger type, e.g., the `NS` in `NS?`. This
makes `@preconcurrency` work properly through structural types like
arrays, optionals, and dictionaries.
While here, also check whether the nominal declaration itself has been
marked as `@preconcurrency`.
Fixes rdar://125081249.
The diagnostic for non-Sendable globa/static `let` properties was checking
for a Sendable conformance without considering `@preconcurrency`. Emit
this diagnostic via a `@preconcurrency`-sensitive path.
Fixes rdar://121889248.
I added a disable flag -disable-region-based-isolation-with-strict-concurrency
so that we do not need to update the current tests. It is only available when
asserts are enabled to ensure users cannot use it.
rdar://125918028
Remarks are intended to be enabled via eg. `-R...`, where as
`(add|remove)_predates_concurrency_import` is a diagnostic that's always
output without any `-R` flag. Move it to a warning instead.
Resolves rdar://114207080.
This means that:
1. In test cases where minimal is the default (swift 5 without
-warn-concurrency), I added RUN lines for targeted, complete, and complete +
sns.
2. In test cases where complete is the default (swift 6, -warn-concurrency,
specified complete with -strict-concurrency), I added a send non-sendable run
line.
In each of these cases, I added additional expected-* lines as appropriate so
the tests can compile in each mode successfully.
Introduce the `@preconcurrency` attribute name for `@_predatesConcurrency`,
which has been the favored name in the pitch thread so far. Retain the
old name for now to help smooth migration.
We'll already suggest the addition of `@_predatesConcurrency` on an import
to downgrade or silence `Sendable`-related diagnostics, so we'll be
adding these to people's code. Over time, this attribute can go stale,
if the imported module's adopt `Sendable`. When the attribute isn't
doing anything, because it didn't suppress any `Sendable`-related
diagnostics, suggest that it be removed.
