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Wrong Sendable closure diagnostics with implicitly unwrapped optional
Description
Hello,
The Swift compiler 5.10 that ships with Xcode 15.3 (15E204a) emits spurious warnings regarding sendable closures, in the specific case of implicitly unwrapped optionals.
Reproduction
In the following code, the compiler emit false positive warnings. They are all related to implicitly unwrapped optionals.
Converting non-sendable function value to '@Sendable () -> Void' may introduce data races
struct ClosureHolder {
var closure: @Sendable () -> Void = { }
var closureOpt: (@Sendable () -> Void)?
var closureIUO: (@Sendable () -> Void)!
}
func f() {
var holder: ClosureHolder = ClosureHolder()
holder.closure = { } // OK
holder.closureOpt = { } // OK
holder.closureIUO = { } // ⚠️ WARNING
var holderOpt: ClosureHolder?
holderOpt?.closure = { } // OK
holderOpt?.closureOpt = { } // OK
holderOpt?.closureIUO = { } // ⚠️ WARNING
var holderIUO: ClosureHolder!
holderIUO.closure = { } // ⚠️ WARNING
holderIUO.closureOpt = { } // ⚠️ WARNING
holderIUO.closureIUO = { } // ⚠️ WARNING
}
Expected behavior
The compiler emits no warning.
Environment
swift-driver version: 1.90.11.1 Apple Swift version 5.10 (swiftlang-5.10.0.13 clang-1500.3.9.4) Target: arm64-apple-macosx14.0
Additional information
No response
Reproducible with both swift-DEVELOPMENT-SNAPSHOT-2024-03-29-a and swift-6.0-DEVELOPMENT-SNAPSHOT-2024-03-26-a.