Explanation: C++ interop synthesizes certain forwarding functions in an
_ObjC module. This confuses MemberImportVisibility. This patch adds
logic to work this around by keeping a mapping between the synthesized
and the original function and looks up where the synthesized functions
belong to based on the original functions' parent module.
Scope: C++ forward interop when MemberImportVisibility is enabled.
Issues: rdar://154887575
Original PRs: #82840
Risk: Low, a narrow change makes getModuleContextForNameLookupForCxxDecl more
precise, and it is only used with MemberImportVisibility.
Testing: Added a compiler test.
Reviewers: @egorzhdan, @tshortli, @hnrklssn
Follow-up from #78132, which did not fix issues related to eagerly imported members like subscripts.
This patch restructures recursive ClangRecordMemberLookup requests to importBaseMemberDecl() in the recursive calls, rather than propagating base member decls up to the initial lookup request and doing the import. Doing so seems to fix lingering resolution issues (which I've added to the regression tests).
rdar://141069984
Nested calls to importBaseMemberDecl() subvert its cache and compromise its idempotence, causing the semantic checker to spuriously report ambiguous member lookups when multiple ClangRecordMemberLookup requests are made (e.g., because of an unrelated missing member lookup).
One such scenario is documented as a test case: test/Interop/Cxx/class/inheritance/inherited-lookup-typechecker.swift fails without this patch because of the expected error from the missing member. Meanwhile, test/Interop/Cxx/class/inheritance/inherited-lookup-executable.swift works because it does not attempt to access a missing member.
This patch fixes the issue by only calling importBaseMemberDecl() in the most derived class (where the ClangRecordMemberLookup originated, i.e., not in recursive requests).
As a consequence of my patch, synthesized member accessors in the derived class directly invoke the member from the base class where the member is inherited from, rather than incurring an indirection at each level of inheritance. As such, the synthesized symbol names are different (and shorter). I've taken this opportunity to update the relevant tests to // CHECK for more of the mangled symbol, rather than only the synthesized symbol prefix, for more precise testing and slightly better readability.
rdar://141069984
