🍒[cxx-interop] Skip type metadata for C++ types that are only used in private C++ fields #78607
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…private C++ fields This fixes compiler errors for C++ types that use pimpl idiom: ``` invalid application of 'sizeof' to an incomplete type ``` rdar://141960396 (cherry picked from commit 738c8fb)
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@swift-ci please test |
Xazax-hun
approved these changes
Jan 13, 2025
DougGregor
approved these changes
Jan 14, 2025
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Explanation: When importing C++ types that use pointer-to-implementation idiom, when the implementation type is forward-declared, the compiler would previously emit an error:
This was happening because Swift was trying to emit the value witness table for
std::unique_ptr<IncompleteType>, which isn't possible, because the destructor cannot be instantiated for an incomplete pointee type.Scope: This changes IRGen logic that emits Swift metadata for private fields. It now ignores private fields imported from Clang, since there is no way to use those from Swift.
Risk: Low, this only affects type metadata of private fields. Swift started importing C++ private fields very recently. Non-C++ imported types don't get private fields in Swift.
Testing: Added new compiler tests.
Issue: rdar://141960396
Reviewer: @Xazax-hun @rjmccall
Original PR: #78467