Diagnose unannotated C++ APIs returning SWIFT_SHARED_REFERENCE at Swift call sites #83025

fahadnayyar · 2025-07-14T04:08:04Z

This patch improves the warning for C++ APIs returning SWIFT_SHARED_REFERENCE types but not annotated with either SWIFT_RETURNS_RETAINED or SWIFT_RETURNS_UNRETAINED in the following ways:

The warning for missing SWIFT_RETURNS_(UN)RETAINED annotations is now emitted on Swift use sites, rather than while importing the API (func/method decls).

This logic is now implemented as a Misl Diagnostic in function diagnoseCxxFunctionCalls in file lib/Sema/MiscDiagnostics.cpp.
The warning is now triggered only when the API is actually used, which reduces noise in large C++ headers.

rdar://150800115

lib/ClangImporter/ImportDecl.cpp

lib/Sema/MiscDiagnostics.cpp

test/Interop/Cxx/foreign-reference/inheritance-diagnostics.swift

lib/Sema/MiscDiagnostics.cpp

lib/ClangImporter/ImportDecl.cpp

lib/Sema/MiscDiagnostics.cpp

Xazax-hun

This looks really clean now, thanks!

lib/Sema/MiscDiagnostics.cpp

lib/ClangImporter/ImportDecl.cpp

include/swift/ClangImporter/ClangImporter.h

lib/ClangImporter/ImportDecl.cpp

include/swift/AST/DiagnosticsSema.def

lib/Sema/MiscDiagnostics.cpp

Xazax-hun

I have one nit inline, once that is addressed the PR looks good to me.

lib/Sema/MiscDiagnostics.cpp

…D_REFERENCE without ownership annotations Move the “unannotated SWIFT_SHARED_REFERENCE return” diagnostic from ClangImporter to Sema use sites (call expressions). This reduces the noise from large headers and only warns when the API is actually used. - New warning: warn_unannotated_cxx_func_returning_frt “cannot infer the ownership of the returned value, annotate %0 with either SWIFT_RETURNS_RETAINED or SWIFT_RETURNS_UNRETAINED” plus a note on the declaration site. - Gated by -enable-experimental-feature WarnUnannotatedReturnOfCxxFrt. - Implementation: * Add diagnoseCxxFunctionCalls() walker in MiscDiagnostics. * Add helpers: ReturnOwnershipInfo, hasImmortalAttrs, isReturningFRT(). * Remove the old import-time GROUPED_WARNING and update tests. rdar://150800115

fahadnayyar · 2025-08-22T23:16:14Z

@swift-ci please smoke test

fahadnayyar · 2025-08-24T00:40:53Z

@swift-ci please smoke test windows platform

fahadnayyar self-assigned this Jul 14, 2025

fahadnayyar added the c++ interop Feature: Interoperability with C++ label Jul 14, 2025

fahadnayyar force-pushed the fnayyar/unannotated-returns-unretained-warn-false-positives-fix branch from 23b360e to 96c60e7 Compare July 15, 2025 10:07

fahadnayyar marked this pull request as ready for review July 15, 2025 10:16

fahadnayyar requested review from zoecarver, egorzhdan, Xazax-hun, j-hui, susmonteiro, hnrklssn, beccadax and ian-twilightcoder as code owners July 15, 2025 10:16