Upcoming feature flag ExistentialAny ignores missing any keyword when constraining a protocol #72588
Description
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Reproduction
Compiling the following program with -enable-upcoming-feature ExistentialAny succeeds, even though it should fail since the constraint on f's parameter is written as P2 instead of any P2.
protocol P1<T> {
associatedtype T
}
protocol P2 {}
func f(_: some P1<P2>) {} // <---Expected behavior
The compiler should (when compiling with the ExistentialAny flag on) require that existential be explicitly spelled with any, as defined in SE-0335.
Environment
Apple Swift version 6.0-dev (LLVM 1ad249b55ef5cc0, Swift b10d97d)
Target: arm64-apple-macosx14.0
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A deviation from expected or documented behavior. Also: expected but undesirable behavior.The Swift compiler itselfFeature: values of types like `any Collection`, `Any` and `AnyObject`; type-erased valuesFeature → protocol: protocols with primary associated typesFeature → type declarations: Protocol declarationsArea → compiler: Semantic analysisFeature: typesBug: Unexpected behavior or incorrect output