Allow `fallthrough` to appear as the last statement
in the case of a `switch` expression. We already
allowed it in other positions, this was just an
oversight.
rdar://127670432
As of now, SE-366 is not correctly implemented with respect to concrete,
bitwise-copyable types like `Int`. Writing `consume someInt` doesn't
actually consume the variable binding as it should, meaning code that
should be flagged as having a use-after-consume is being silently
permitted:
```swift
let someInt = 10
let y = consume someInt
print(someInt) // no error!
```
This has been a problem since Swift 5.9. Eventually we plan to fix this
issue, which means code previously doing the above would become an
error. To help people get ready for the fix, start warning people that
these consumes are actually no-ops and suggest removing them until the
intended behavior is actually enforced in the future.
resolves rdar://127081103
We don't yet have keypaths working correctly to allow access to
noncopyable fields, so we should raise a friendly error in Sema rather
than an error-out elsewhere vaguely.
resolves rdar://109287447
Unfortunately we've encountered another source
breaking case here:
```
class C {
func method() {}
func foo() {
Task { [weak self] in
Task {
method()
}
}
}
}
```
In 5.10 we'd only do the unqualified lookup for
`self` when directly in a `weak self` closure,
but with the implicit self rework, we'd start
using the `weak self` here, leading to a
type-checker error.
At this point, adding more edge cases to the
existing logic is going to make things much more
complicated. Instead, reinstate the 5.10 implicit
self lookup behavior and diagnostic logic,
switching over to the new logic only under Swift 6
mode.
rdar://129475277
Although I don't plan to bring over new assertions wholesale
into the current qualification branch, it's entirely possible
that various minor changes in main will use the new assertions;
having this basic support in the release branch will simplify that.
(This is why I'm adding the includes as a separate pass from
rewriting the individual assertions)
I want to expose the syntactic checking to other parts of Sema, so that
we can determine whether an expression is a candidate for having a
`consume` added to it.
In 5.10 we warned on this:
```swift
func bar(@_implicitSelfCapture _ fn: @escaping () -> Void) {}
class C {
func foo() {
bar { [weak self] in
foo()
}
}
}
```
But with the implicit self rework, this accidentally
became an error. Fix it to ensure we continue to
warn until Swift 6 mode.
rdar://128941797
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.
We walk up the DeclContext hierarchy looking for closures, but they might
not have had their types set yet because they're currently being type
checked.
None of the diagnostics in MiscDiagnostics make a distinction between
sendable or actor-isolated function references which means that we can
skip conversions while reaching for a declaration used in an application.
We can use part of the new infrastructure if we simply handle abstract
conformances to Copyable, which is what we'd get upon lookup for a
nominal in the old world. This means that we can merge diagnostics for
the containment test together, and fix differences with deinit
diagnostics.
Sendable key path literals are represented as an existential
protocol composition with `Sendable` protocol which has to be
opened in certain scenarios i.e. to pass it to non-Sendable version.
