[cxx-interop] Allow instantiated operator methods to serve as protocol conformance witnesses #62764
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…l conformance witnesses If a templated C++ class declares an operator as a member function, and is instantiated using a typedef or a using-decl on the C++ side, it previously could not be conformed to a Swift protocol that requires the operator function despite matching signatures. This was due to a Swift name lookup issue: operators, unlike regular member functions, are found by doing an unqualified lookup. Since C++ class template specializations and their members are not added to `SwiftLookupTable`, when doing qualified lookup members are searched by looking at all of the members of the specialization and choosing the ones with matching names. With unqualified lookup, we cannot rely on knowing the right specialization and need to search for all the operators in a given module. This change adds synthesized operator thunks to `SwiftLookupTable` to make them discoverable by unqualified lookup.
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zoecarver
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Jan 3, 2023
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If a templated C++ class declares an operator as a member function, and is instantiated using a typedef or a using-decl on the C++ side, it previously could not be conformed to a Swift protocol that requires the operator function despite matching signatures.
This was due to a Swift name lookup issue: operators, unlike regular member functions, are found by doing an unqualified lookup. Since C++ class template specializations and their members are not added to
SwiftLookupTable, when doing qualified lookup members are searched by looking at all of the members of the specialization and choosing the ones with matching names. With unqualified lookup, we cannot rely on knowing the right specialization and need to search for all the operators in a given module.This change adds synthesized operator thunks to
SwiftLookupTableto make them discoverable by unqualified lookup.