🍒[cxx-interop] Ban ObjCBool from being substituted into C++ templates #74967
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This fixes a compiler crash when calling a templated C++ function with a parameter of type `ObjCBool` from Swift. The compiler now emits an error for this.
Previously the following would happen:
1. Swift starts to emit SILGen for a call expression `takeTAsConstRef(ObjCBool(true))`.
2. `takeTAsConstRef` is a templated C++ function, so Swift asks Clang to instantiate a `takeTAsConstRef` with a built-in Obj-C boolean type.
3. Swift gets an instantiated function template back that looks like this: `void takeTAsConstRef(_Bool t) { ... }`.
4. Swift's ClangImporter begins to import that instantiated function.
5. Since the parameter type is not spelled as `BOOL`, the parameter is not imported as `ObjCBool`. Instead, it's imported as regular Swift `Bool`.
6. Swift realizes that the types don't match (`ObjCBool` vs `Bool`), tries to apply any of the known implicit conversions, fails to do so, crashes.
rdar://130424969
(cherry picked from commit fe5b009)
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@swift-ci please test |
DougGregor
approved these changes
Jul 5, 2024
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Explanation: This fixes a compiler crash when calling a templated C++ function with a parameter of type
ObjCBoolfrom Swift. The compiler now emits an error for this.Scope: Changes the logic that transforms Swift types to C++ types for the purpose of C++ template instantiation.
Risk: Low, only affects C++ templates.
Testing: Added a compile test.
Issue: rdar://130424969
Reviewer: @beccadax
Original PR: #74790