During the lifecycle of a feature, it may start as an experimental feature and
then graduate to become an upcoming feature. To preserve compatibility with
projects that adopted the feature when it was experimental,
`-enable-experimental-feature` ought to be able to enable upcoming features,
too.
Since projects may use `-enable-experimental-feature` for compatibility with an
older toolchain that does not have the feature as an upcoming feature, there is
no warning when the flag is used to enable an upcoming feature.
Note that if the semantics of a feature change when it graduates from
experimental to upcoming, then the feature must be renamed so that projects
using the experimental feature have an opportunity opt-in to the new semantics
of the upcoming feature.
Resolves rdar://134276783.
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.
Instance properties of non-sendable types cannot safely be
accessed within deinitializers. Make sure we respect `@preconcurrency`
when diagnosing these.
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.
module has enabled Swift 6.
Warnings when the client enables Swift 6 are not useful because that's not the
point when the library API has been audited.
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.
