🍒[cxx-interop] Use more correct type names in C++ template parameters #69328
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When importing a C++ class template instantiation, Swift translates the template parameter type names from C++ into their Swift equivalent. For instance, `basic_string<wchar_t, char_traits<wchar_t>, allocator<wchar_t>>` gets imported as `basic_string<Scalar, char_traits<Scalar>, allocator<Scalar>>`: `wchar_t` is imported as `CWideChar`, which is a typealias for `Scalar` on most platforms including Darwin. Notice that Swift goes through the `CWideChar` typealias on the specific platform. Another instantiation `basic_string<uint32_t, char_traits<uint32_t>, allocator<uint32_t>>` also gets imported as `basic_string<Scalar, char_traits<Scalar>, allocator<Scalar>>`: `uint32_t` is also imported as `Scalar`. This is problematic because we have two distinct C++ types that have the same name in Swift. This change makes sure Swift doesn't go through typealiases when emitting names of template parameters, so `wchar_t` would now get printed as `CWideChar`, `int` would get printed as `CInt`, etc. This also encourages clients to use the correct type (`CInt`, `CWideChar`, etc) instead of relying on platform-specific typealiases. rdar://115673622 (cherry picked from commit 041005a)
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@swift-ci please test |
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@swift-ci please test source compatibility |
hyp
approved these changes
Oct 24, 2023
DougGregor
approved these changes
Oct 26, 2023
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Explanation:
When importing a C++ class template instantiation, Swift translates the template parameter type names from C++ into their Swift equivalent.
For instance,
basic_string<wchar_t, char_traits<wchar_t>, allocator<wchar_t>>gets imported asbasic_string<Scalar, char_traits<Scalar>, allocator<Scalar>>:wchar_tis imported asCWideChar, which is a typealias forScalaron most platforms including Darwin. Notice that Swift goes through theCWideChartypealias on the specific platform. Another instantiationbasic_string<uint32_t, char_traits<uint32_t>, allocator<uint32_t>>also gets imported asbasic_string<Scalar, char_traits<Scalar>, allocator<Scalar>>:uint32_tis also imported asScalar. This is problematic because we have two distinct C++ types that have the same name in Swift.This change makes sure Swift doesn't go through typealiases when emitting names of template parameters, so
wchar_twould now get printed asCWideChar,intwould get printed asCInt, etc.Scope: All of the code changes are on a C++ interop only code path.
Risk: Low, only takes effect when C++ interop is enabled.
Testing: Covered by LIT tests.
Original PR: #68620
rdar://115673622
(cherry picked from commit 041005a)