Egor Zhdan 84ae5fbe8c [cxx-interop] Fix runtime crash when casting from an existential to a foreign reference type ...

When a C++ foreign reference type is conformed to a Swift protocol via a Swift extension, trying to cast `any MyProtocol` to the foreign reference type crashes the runtime.

This was because `selectCasterForDest` wasn't handling C++ foreign reference types, and we were hitting `swift_unreachable`.

This change makes sure the runtime doesn't crash for such casts.

Notably, Swift doesn't have enough metadata to determine if the conditional cast actually succeeded. This is also a problem for CF types. Casting CF types in a similar fashion triggers a typechecker diagnostic. That diagnostic will be amended in a follow-up patch to also trigger for foreign reference types.

rdar://141227849

2024-12-16 20:23:17 +00:00

99 KiB

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