[AST/Sema] SE-0478: Implement using declaration under an experimental flag
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Initially this declaration is going to be used to determine per-file default actor isolation i.e. `using @MainActor` and `using nonisolated` but it could be extended to support other file-global settings in the future.
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swiftlang/swift-syntax#3087 |
hamishknight
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May 30, 2025
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swiftlang/swift-syntax#3087 |
xedin
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using declaration under an experimental flag
hamishknight
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May 31, 2025
…f `.swift` These are split-file C++ tests, this is a problem for swift-syntax because `.swift` tests get parsed for round-trip testing if swift-syntax is located near swift.
The default isolation is computed based on `using` declaration found in the file, if any.
These declarations are effectively `fileprivate` at the moment and should appear in swift interfaces.
…experimental feature
Infer default actor isolation from `using` declaration in the file scope and use it to override one that is set by `-default-isolation` flag.
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swiftlang/swift-syntax#3087 |
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swiftlang/swift-syntax#3087 |
ktoso
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Jun 2, 2025
| @@ -66,3 +71,12 @@ func misisngPatternTest(arr: [Int]) { | |||
| for {} // expected-error {{expected pattern, 'in', and expression in 'for' statement}} | |||
| // expected-note@-1 {{insert pattern, 'in', and expression}} {{7-7=<#pattern#> }} {{7-7=in }} {{7-7=<#expression#> }} | |||
| } | |||
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| using @MainActor // expected-note {{default isolation was previously declared here}} | |||
| using nonisolated // expected-error {{invalid redeclaration of file-level default actor isolation}} | |||
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Hah, exactly what I was worried about when I saw the proposal update :)
Good to see we diagnose this.
ktoso
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Jun 2, 2025
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This is an alternative spelling of
typealias DefaultIsolation = (MainActor | nonisolated)that was proposed as part of SE-0478.usingdeclaration accepts an attribute or a modifier and currently could be used to set a default actor isolation per file, but could be extended to support other use-cases in the future.Implementation uses
DefaultIsolationPerFileexperimental feature flag to hide the syntax.