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[cxx-interop] Document some caveats of safe interop #1094

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[cxx-interop] Document some caveats of safe interop #1094

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11 changes: 11 additions & 0 deletions documentation/cxx-interop/safe-interop/index.md
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Expand Up @@ -105,6 +105,10 @@ struct SWIFT_NONESCAPABLE StringRef { ... };
Now the Swift compiler imports `StringRef` as a safe type and no longer
emits a warning about using an unsafe type.

<div class="info" markdown="1">
Some containers and protocols do not yet support non-escapable types in Swift 6.2.
</div>

### Annotating C++ APIs

Building the code again will emit a new diagnostic for the `fileName` function about
Expand Down Expand Up @@ -387,6 +391,13 @@ compiler can bridge those span-like parameters to Swift's
and [`MutableSpan`](https://github.com/swiftlang/swift-evolution/blob/main/proposals/0467-MutableSpan.md)
types, and the user with a safe and convenient interface to those imported APIs.

<div class="info" markdown="1">
At the time of writing, the features described in this section
are behind an experimental feature flag on the Swift 6.2 release branch.
To enable these features, pass `-enable-experimental-feature SafeInteropWrappers`
to the Swift compiler.
</div>

### C++ `std::span` Support

APIs taking or returning C++'s `std::span` with sufficient lifetime
Expand Down