Make @objcImpl work with @_cdecl

include/swift/AST/Attr.def

@@ -246,7 +246,7 @@ DECL_ATTR(_restatedObjCConformance, RestatedObjCConformance,
   OnProtocol | UserInaccessible | LongAttribute | RejectByParser | NotSerialized | ABIStableToAdd | ABIStableToRemove | APIStableToAdd | APIStableToRemove,
   70)
 DECL_ATTR(_objcImplementation, ObjCImplementation,
-  OnExtension | UserInaccessible | ABIBreakingToAdd | ABIBreakingToRemove | APIBreakingToAdd | APIBreakingToRemove,
+  OnExtension | OnAbstractFunction | UserInaccessible | ABIBreakingToAdd | ABIBreakingToRemove | APIBreakingToAdd | APIBreakingToRemove,
   72)
 DECL_ATTR(_optimize, Optimize,
   OnAbstractFunction | OnSubscript | OnVar | UserInaccessible | ABIStableToAdd | ABIStableToRemove | APIStableToAdd | APIStableToRemove,

include/swift/AST/Decl.h

@@ -941,6 +941,11 @@ class alignas(1 << DeclAlignInBits) Decl : public ASTAllocated<Decl> {
   /// attribute macro expansion.
   DeclAttributes getSemanticAttrs() const;
 
+  /// True if this declaration provides an implementation for an imported
+  /// Objective-C declaration. This implies various restrictions and special
+  /// behaviors for it and, if it's an extension, its members.
+  bool isObjCImplementation() const;
+
   using AuxiliaryDeclCallback = llvm::function_ref<void(Decl *)>;
 
   /// Iterate over the auxiliary declarations for this declaration,
@@ -1836,11 +1841,6 @@ class ExtensionDecl final : public GenericContext, public Decl,
   /// resiliently moved into the original protocol itself.
   bool isEquivalentToExtendedContext() const;
 
-  /// True if this extension provides an implementation for an imported
-  /// Objective-C \c \@interface. This implies various restrictions and special
-  /// behaviors for its members.
-  bool isObjCImplementation() const;
-
   /// Returns the name of the category specified by the \c \@_objcImplementation
   /// attribute, or \c None if the name is invalid. Do not call unless
   /// \c isObjCImplementation() returns \c true.
@@ -2778,6 +2778,10 @@ class ValueDecl : public Decl {
     return DeclNameRef(Name);
   }
 
+  /// Retrieve the C declaration name that names this function, or empty
+  /// string if it has none.
+  StringRef getCDeclName() const;
+
   /// Retrieve the name to use for this declaration when interoperating
   /// with the Objective-C runtime.
   ///

include/swift/AST/DiagnosticsClangImporter.def

@@ -134,8 +134,9 @@ WARNING(api_pattern_attr_ignored, none,
 
 ERROR(objc_implementation_two_impls, none,
       "duplicate implementation of Objective-C %select{|category %0 on }0"
-      "class %1",
-      (Identifier, ValueDecl *))
+      "%kind1",
+      (Identifier, Decl *))
+
 NOTE(previous_objc_implementation, none,
      "previously implemented by extension here", ())
 

include/swift/AST/DiagnosticsSema.def

@@ -1740,9 +1740,17 @@ ERROR(attr_objc_implementation_category_not_found,none,
       "could not find category %0 on Objective-C class %1; make sure your "
       "umbrella or bridging header imports the header that declares it",
       (Identifier, ValueDecl*))
+ERROR(attr_objc_implementation_func_not_found,none,
+      "could not find imported function '%0' matching %kind1; make sure your "
+      "umbrella or bridging header imports the header that declares it",
+      (StringRef, ValueDecl*))
 NOTE(attr_objc_implementation_fixit_remove_category_name,none,
      "remove arguments to implement the main '@interface' for this class",
      ())
+ERROR(attr_objc_implementation_no_category_for_func,none,
+      "%kind0 does not belong to an Objective-C category; remove the category "
+      "name from this attribute",
+      (ValueDecl*))
 ERROR(attr_objc_implementation_no_conformance,none,
       "'@_objcImplementation' extension cannot add conformance to %0; "
       "add this conformance %select{with an ordinary extension|"

include/swift/AST/LookupKinds.h

@@ -41,7 +41,8 @@ enum NLOptions : unsigned {
 
   /// Don't check access when doing lookup into a type.
   ///
-  /// This option is not valid when performing lookup into a module.
+  /// When performing lookup into a module, this option only applies to
+  /// declarations in the same module the lookup is coming from.
   NL_IgnoreAccessControl = 1 << 3,
 
   /// This lookup should only return type declarations.

include/swift/AST/TypeCheckRequests.h

@@ -4544,7 +4544,7 @@ class SemanticBriefCommentRequest
 /// This is done on all of a class's implementations at once to improve diagnostics.
 class TypeCheckObjCImplementationRequest
     : public SimpleRequest<TypeCheckObjCImplementationRequest,
-                           evaluator::SideEffect(ExtensionDecl *),
+                           evaluator::SideEffect(Decl *),
                            RequestFlags::Cached> {
 public:
   using SimpleRequest::SimpleRequest;
@@ -4554,7 +4554,7 @@ class TypeCheckObjCImplementationRequest
 
   // Evaluation.
   evaluator::SideEffect
-  evaluate(Evaluator &evaluator, ExtensionDecl *ED) const;
+  evaluate(Evaluator &evaluator, Decl *D) const;
 
 public:
   // Separate caching.

lib/AST/Decl.cpp

@@ -1847,7 +1847,7 @@ Type ExtensionDecl::getExtendedType() const {
   return ErrorType::get(ctx);
 }
 
-bool ExtensionDecl::isObjCImplementation() const {
+bool Decl::isObjCImplementation() const {
   return getAttrs().hasAttribute<ObjCImplementationAttr>(/*AllowInvalid=*/true);
 }
 
@@ -3869,6 +3869,22 @@ void ValueDecl::setInterfaceType(Type type) {
                                         std::move(type));
 }
 
+StringRef ValueDecl::getCDeclName() const {
+  // Treat imported C functions as implicitly @_cdecl.
+  if (auto clangDecl = dyn_cast_or_null<clang::FunctionDecl>(getClangDecl())) {
+    if (clangDecl->getLanguageLinkage() == clang::CLanguageLinkage
+          && clangDecl->getIdentifier())
+      return clangDecl->getName();
+  }
+
+  // Handle explicit cdecl attributes.
+  if (auto cdeclAttr = getAttrs().getAttribute<CDeclAttr>()) {
+    return cdeclAttr->Name;
+  }
+
+  return "";
+}
+
 llvm::Optional<ObjCSelector>
 ValueDecl::getObjCRuntimeName(bool skipIsObjCResolution) const {
   if (auto func = dyn_cast<AbstractFunctionDecl>(this))
@@ -4404,7 +4420,8 @@ static bool checkAccess(const DeclContext *useDC, const ValueDecl *VD,
   // a context where we would access its storage directly, forbid access. Name
   // lookups will instead find and use the matching interface decl.
   // FIXME: Passing `true` for `isAccessOnSelf` may cause false positives.
-  if (isObjCMemberImplementation(VD, getAccessLevel) &&
+  if ((VD->isObjCImplementation() ||
+         isObjCMemberImplementation(VD, getAccessLevel)) &&
       VD->getAccessSemanticsFromContext(useDC, /*isAccessOnSelf=*/true)
           != AccessSemantics::DirectToStorage)
     return false;

lib/AST/ModuleNameLookup.cpp

@@ -165,6 +165,11 @@ void ModuleNameLookup<LookupStrategy>::lookupInModule(
         if (resolutionKind == ResolutionKind::MacrosOnly && !isa<MacroDecl>(VD))
           return true;
         if (respectAccessControl &&
+            // NL_IgnoreAccessControl applies only to the current module.
+            !((options & NL_IgnoreAccessControl) &&
+                moduleScopeContext &&
+                moduleScopeContext->getParentModule() ==
+                    VD->getDeclContext()->getParentModule()) &&
             !VD->isAccessibleFrom(moduleScopeContext, false,
                                   includeUsableFromInline))
           return true;

lib/AST/SwiftNameTranslation.cpp

@@ -139,7 +139,7 @@ getObjCNameForSwiftDecl(const ValueDecl *VD, DeclName PreferredName){
 bool swift::objc_translation::
 isVisibleToObjC(const ValueDecl *VD, AccessLevel minRequiredAccess,
                 bool checkParent) {
-  if (!(VD->isObjC() || VD->getAttrs().hasAttribute<CDeclAttr>()))
+  if (!(VD->isObjC() || !VD->getCDeclName().empty()))
     return false;
   if (VD->getFormalAccess() >= minRequiredAccess) {
     return true;

lib/ClangImporter/ClangImporter.cpp

@@ -5827,21 +5827,6 @@ findImplsGivenInterface(ClassDecl *classDecl, Identifier categoryName) {
       impls.push_back(ext);
   }
 
-  if (impls.size() > 1) {
-    llvm::sort(impls, OrderDecls());
-
-    auto &diags = classDecl->getASTContext().Diags;
-    for (auto extraImpl : llvm::ArrayRef<Decl *>(impls).drop_front()) {
-      auto attr = extraImpl->getAttrs().getAttribute<ObjCImplementationAttr>();
-      attr->setCategoryNameInvalid();
-
-      diags.diagnose(attr->getLocation(), diag::objc_implementation_two_impls,
-                     categoryName, classDecl)
-        .fixItRemove(attr->getRangeWithAt());
-      diags.diagnose(impls.front(), diag::previous_objc_implementation);
-    }
-  }
-
   return impls;
 }
 
@@ -5872,10 +5857,26 @@ findInterfaceGivenImpl(ClassDecl *classDecl, ExtensionDecl *ext) {
 }
 
 static ObjCInterfaceAndImplementation
-constructResult(Decl *interface, llvm::TinyPtrVector<Decl *> impls) {
-  if (impls.empty())
+constructResult(Decl *interface, llvm::TinyPtrVector<Decl *> &impls,
+                Decl *diagnoseOn, Identifier categoryName) {
+  if (!interface || impls.empty())
     return ObjCInterfaceAndImplementation();
 
+  if (impls.size() > 1) {
+    llvm::sort(impls, OrderDecls());
+
+    auto &diags = interface->getASTContext().Diags;
+    for (auto extraImpl : llvm::ArrayRef<Decl *>(impls).drop_front()) {
+      auto attr = extraImpl->getAttrs().getAttribute<ObjCImplementationAttr>();
+      attr->setCategoryNameInvalid();
+
+      diags.diagnose(attr->getLocation(), diag::objc_implementation_two_impls,
+                     categoryName, diagnoseOn)
+        .fixItRemove(attr->getRangeWithAt());
+      diags.diagnose(impls.front(), diag::previous_objc_implementation);
+    }
+  }
+
   return ObjCInterfaceAndImplementation(interface, impls.front());
 }
 
@@ -5924,31 +5925,103 @@ findContextInterfaceAndImplementation(DeclContext *dc) {
   // look for extensions implementing it.
 
   auto implDecls = findImplsGivenInterface(classDecl, categoryName);
-  return constructResult(interfaceDecl, implDecls);
+  return constructResult(interfaceDecl, implDecls, classDecl, categoryName);
+}
+
+static void lookupRelatedFuncs(AbstractFunctionDecl *func,
+                               SmallVectorImpl<ValueDecl *> &results) {
+  DeclName swiftName;
+  if (auto accessor = dyn_cast<AccessorDecl>(func))
+    swiftName = accessor->getStorage()->getName();
+  else
+    swiftName = func->getName();
+
+  if (auto ty = func->getDeclContext()->getSelfNominalTypeDecl()) {
+    ty->lookupQualified({ ty }, DeclNameRef(swiftName), func->getLoc(),
+                        NL_QualifiedDefault | NL_IgnoreAccessControl, results);
+  }
+  else {
+    auto mod = func->getDeclContext()->getParentModule();
+    mod->lookupQualified(mod, DeclNameRef(swiftName), func->getLoc(),
+                         NL_RemoveOverridden | NL_IgnoreAccessControl, results);
+  }
+}
+
+static ObjCInterfaceAndImplementation
+findFunctionInterfaceAndImplementation(AbstractFunctionDecl *func) {
+  if (!func)
+    return {};
+
+  // If this isn't either a clang import or an implementation, there's no point
+  // doing any work here.
+  if (!func->hasClangNode() && !func->isObjCImplementation())
+    return {};
+
+  OptionalEnum<AccessorKind> accessorKind;
+  if (auto accessor = dyn_cast<AccessorDecl>(func))
+    accessorKind = accessor->getAccessorKind();
+
+  StringRef clangName = func->getCDeclName();
+  if (clangName.empty())
+    return {};
+
+  SmallVector<ValueDecl *, 4> results;
+  lookupRelatedFuncs(func, results);
+
+  // Classify the `results` as either the interface or an implementation.
+  // (Multiple implementations are invalid but utterable.)
+  Decl *interface = nullptr;
+  TinyPtrVector<Decl *> impls;
+
+  for (ValueDecl *result : results) {
+    AbstractFunctionDecl *resultFunc = nullptr;
+    if (accessorKind) {
+      if (auto resultStorage = dyn_cast<AbstractStorageDecl>(result))
+        resultFunc = resultStorage->getAccessor(*accessorKind);
+    }
+    else
+      resultFunc = dyn_cast<AbstractFunctionDecl>(result);
+
+    if (!resultFunc)
+      continue;
+
+    if (resultFunc->getCDeclName() != clangName)
+      continue;
+
+    if (resultFunc->hasClangNode()) {
+      if (interface) {
+        // This clang name is overloaded. That should only happen with C++
+        // functions/methods, which aren't currently supported.
+        return {};
+      }
+      interface = result;
+    } else if (resultFunc->isObjCImplementation()) {
+      impls.push_back(result);
+    }
+  }
+
+  // If we found enough decls to construct a result, `func` should be among them
+  // somewhere.
+  assert(interface == nullptr || impls.empty() ||
+         interface == func || llvm::is_contained(impls, func));
+
+  return constructResult(interface, impls, interface,
+                         /*categoryName=*/Identifier());
 }
 
 ObjCInterfaceAndImplementation ObjCInterfaceAndImplementationRequest::
 evaluate(Evaluator &evaluator, Decl *decl) const {
-  // These have direct links to their counterparts through the
+  // Types and extensions have direct links to their counterparts through the
   // `@_objcImplementation` attribute. Let's resolve that.
   // (Also directing nulls here, where they'll early-return.)
   if (auto ty = dyn_cast_or_null<NominalTypeDecl>(decl))
     return findContextInterfaceAndImplementation(ty);
   else if (auto ext = dyn_cast<ExtensionDecl>(decl))
     return findContextInterfaceAndImplementation(ext);
+  // Abstract functions have to be matched through their @_cdecl attributes.
+  else if (auto func = dyn_cast<AbstractFunctionDecl>(decl))
+    return findFunctionInterfaceAndImplementation(func);
 
-  // Anything else is resolved by first locating the context's interface and
-  // impl, then matching it to its counterpart. (Instead of calling
-  // `findContextInterfaceAndImplementation()` directly, we'll use the request
-  // recursively to take advantage of caching.)
-  auto contextDecl = decl->getDeclContext()->getAsDecl();
-  if (!contextDecl)
-    return {};
-
-  ObjCInterfaceAndImplementationRequest req(contextDecl);
-  /*auto contextPair =*/ evaluateOrDefault(evaluator, req, {});
-
-  // TODO: Implement member matching.
   return {};
 }
 

lib/IRGen/GenDecl.cpp

@@ -3544,7 +3544,10 @@ llvm::Function *IRGenModule::getAddrOfSILFunction(
       if (hasOrderNumber) {
         auto &fnList = Module.getFunctionList();
         fnList.remove(fn);
-        fnList.insert(llvm::Module::iterator(insertBefore), fn);
+        if (insertBefore)
+          fnList.insert(llvm::Module::iterator(insertBefore), fn);
+        else
+          fnList.push_back(fn);
 
         EmittedFunctionsByOrder.insert(orderNumber, fn);
       }

lib/PrintAsClang/DeclAndTypePrinter.cpp

@@ -1414,8 +1414,7 @@ class DeclAndTypePrinter::Implementation
 
     assert(FD->getAttrs().hasAttribute<CDeclAttr>() && "not a cdecl function");
     os << "SWIFT_EXTERN ";
-    printFunctionDeclAsCFunctionDecl(
-        FD, FD->getAttrs().getAttribute<CDeclAttr>()->Name, resultTy);
+    printFunctionDeclAsCFunctionDecl(FD, FD->getCDeclName(), resultTy);
     printFunctionClangAttributes(FD, funcTy);
     printAvailability(FD);
     os << ";\n";
@@ -1425,12 +1424,12 @@ class DeclAndTypePrinter::Implementation
     FunctionSwiftABIInformation(AbstractFunctionDecl *FD,
                                 LoweredFunctionSignature signature)
         : signature(signature) {
-      isCDecl = FD->getAttrs().hasAttribute<CDeclAttr>();
+      isCDecl = !FD->getCDeclName().empty();
       if (!isCDecl) {
         auto mangledName = SILDeclRef(FD).mangle();
         symbolName = FD->getASTContext().AllocateCopy(mangledName);
       } else {
-        symbolName = FD->getAttrs().getAttribute<CDeclAttr>()->Name;
+        symbolName = FD->getCDeclName();
       }
     }
 
@@ -2858,12 +2857,16 @@ static bool hasExposeAttr(const ValueDecl *VD, bool isExtension = false) {
   return false;
 }
 
-/// Skip \c \@objcImplementation \c extension member implementations and
-/// overrides. They are already declared in handwritten headers, and they may
-/// have attributes that aren't allowed in a category.
+/// Skip \c \@objcImplementation functions, \c extension member
+/// implementations, and overrides. They are already declared in handwritten
+/// headers, and they may have attributes that aren't allowed in a category.
 ///
 /// \return true if \p VD should \em not be included in the header.
 static bool excludeForObjCImplementation(const ValueDecl *VD) {
+  // If it's an ObjC implementation (and not an extension, which might have
+  // members that need printing), skip it; it's declared elsewhere.
+  if (VD->isObjCImplementation() && ! isa<ExtensionDecl>(VD))
+    return true;
   // Exclude member implementations; they are declared elsewhere.
   if (VD->isObjCMemberImplementation())
     return true;