[cxx-interop] Import using decls that refer to member operators of a base class

This is required for proper support for `std::vector::iterator` on Windows.

rdar://118657936 / resolves swiftlang#69990

Author: egorzhdan

lib/ClangImporter/ImportDecl.cpp

@@ -2294,53 +2294,6 @@ namespace {
         }
 
         if (auto MD = dyn_cast<FuncDecl>(member)) {
-          if (auto cxxMethod = dyn_cast<clang::CXXMethodDecl>(m)) {
-            ImportedName methodImportedName =
-                Impl.importFullName(cxxMethod, getActiveSwiftVersion());
-            auto cxxOperatorKind = cxxMethod->getOverloadedOperator();
-
-            if (cxxOperatorKind == clang::OverloadedOperatorKind::OO_PlusPlus) {
-              // Make sure the type is not a foreign reference type.
-              // We cannot handle `operator++` for those types, since the
-              // current implementation creates a new instance of the type.
-              if (cxxMethod->param_empty() && !isa<ClassDecl>(result)) {
-                // This is a pre-increment operator. We synthesize a
-                // non-mutating function called `successor() -> Self`.
-                FuncDecl *successorFunc = synthesizer.makeSuccessorFunc(MD);
-                result->addMember(successorFunc);
-
-                Impl.markUnavailable(MD, "use .successor()");
-              } else {
-                Impl.markUnavailable(MD, "unable to create .successor() func");
-              }
-              MD->overwriteAccess(AccessLevel::Private);
-            }
-            // Check if this method _is_ an overloaded operator but is not a
-            // call / subscript / dereference / increment. Those
-            // operators do not need static versions.
-            else if (cxxOperatorKind !=
-                         clang::OverloadedOperatorKind::OO_None &&
-                     cxxOperatorKind !=
-                         clang::OverloadedOperatorKind::OO_PlusPlus &&
-                     cxxOperatorKind !=
-                         clang::OverloadedOperatorKind::OO_Call &&
-                     !methodImportedName.isSubscriptAccessor() &&
-                     !methodImportedName.isDereferenceAccessor()) {
-
-              auto opFuncDecl = synthesizer.makeOperator(MD, cxxMethod);
-
-              Impl.addAlternateDecl(MD, opFuncDecl);
-
-              auto msg = "use " + std::string{clang::getOperatorSpelling(cxxOperatorKind)} + " instead";
-              Impl.markUnavailable(MD,msg);
-
-              // Make the actual member operator private.
-              MD->overwriteAccess(AccessLevel::Private);
-
-              // Make sure the synthesized decl can be found by lookupDirect.
-              result->addMemberToLookupTable(opFuncDecl);
-            }
-          }
           methods.push_back(MD);
           continue;
         }
@@ -3275,12 +3228,19 @@ namespace {
     }
 
     /// Handles special functions such as subscripts and dereference operators.
-    bool processSpecialImportedFunc(FuncDecl *func, ImportedName importedName) {
+    bool
+    processSpecialImportedFunc(FuncDecl *func, ImportedName importedName,
+                               clang::OverloadedOperatorKind cxxOperatorKind) {
+      if (cxxOperatorKind == clang::OverloadedOperatorKind::OO_None)
+        return true;
+
       auto dc = func->getDeclContext();
+      auto typeDecl = dc->getSelfNominalTypeDecl();
+      if (!typeDecl)
+        return true;
 
       if (importedName.isSubscriptAccessor()) {
         assert(func->getParameters()->size() == 1);
-        auto typeDecl = dc->getSelfNominalTypeDecl();
         auto parameter = func->getParameters()->get(0);
         auto parameterType = parameter->getTypeInContext();
         if (!typeDecl || !parameterType)
@@ -3310,10 +3270,10 @@ namespace {
         }
 
         Impl.markUnavailable(func, "use subscript");
+        return true;
       }
 
       if (importedName.isDereferenceAccessor()) {
-        auto typeDecl = dc->getSelfNominalTypeDecl();
         auto &getterAndSetter = Impl.cxxDereferenceOperators[typeDecl];
 
         switch (importedName.getAccessorKind()) {
@@ -3328,6 +3288,42 @@ namespace {
         }
 
         Impl.markUnavailable(func, "use .pointee property");
+        return true;
+      }
+
+      if (cxxOperatorKind == clang::OverloadedOperatorKind::OO_PlusPlus) {
+        // Make sure the type is not a foreign reference type.
+        // We cannot handle `operator++` for those types, since the
+        // current implementation creates a new instance of the type.
+        if (func->getParameters()->size() == 0 && !isa<ClassDecl>(typeDecl)) {
+          // This is a pre-increment operator. We synthesize a
+          // non-mutating function called `successor() -> Self`.
+          FuncDecl *successorFunc = synthesizer.makeSuccessorFunc(func);
+          typeDecl->addMember(successorFunc);
+
+          Impl.markUnavailable(func, "use .successor()");
+        } else {
+          Impl.markUnavailable(func, "unable to create .successor() func");
+        }
+        func->overwriteAccess(AccessLevel::Private);
+        return true;
+      }
+
+      // Check if this method _is_ an overloaded operator but is not a
+      // call / subscript / dereference / increment. Those
+      // operators do not need static versions.
+      if (cxxOperatorKind != clang::OverloadedOperatorKind::OO_Call) {
+        auto opFuncDecl = synthesizer.makeOperator(func, cxxOperatorKind);
+        Impl.addAlternateDecl(func, opFuncDecl);
+
+        Impl.markUnavailable(
+            func, (Twine("use ") + clang::getOperatorSpelling(cxxOperatorKind) +
+                   " instead")
+                      .str());
+
+        // Make sure the synthesized decl can be found by lookupDirect.
+        typeDecl->addMemberToLookupTable(opFuncDecl);
+        return true;
       }
 
       return true;
@@ -3656,7 +3652,8 @@ namespace {
         func->setAccess(AccessLevel::Public);
 
         if (!importFuncWithoutSignature) {
-          bool success = processSpecialImportedFunc(func, importedName);
+          bool success = processSpecialImportedFunc(
+              func, importedName, decl->getOverloadedOperator());
           if (!success)
             return nullptr;
         }
@@ -4012,6 +4009,12 @@ namespace {
       if (!importedDC)
         return nullptr;
 
+      // While importing the DeclContext, we might have imported the decl
+      // itself.
+      auto known = Impl.importDeclCached(decl, getVersion());
+      if (known.has_value())
+        return known.value();
+
       if (isa<clang::TypeDecl>(decl->getTargetDecl())) {
         Decl *SwiftDecl = Impl.importDecl(decl->getUnderlyingDecl(), getActiveSwiftVersion());
         if (!SwiftDecl)
@@ -4060,7 +4063,8 @@ namespace {
         if (!clonedMethod)
           return nullptr;
 
-        bool success = processSpecialImportedFunc(clonedMethod, importedName);
+        bool success = processSpecialImportedFunc(
+            clonedMethod, importedName, targetMethod->getOverloadedOperator());
         if (!success)
           return nullptr;
 

lib/ClangImporter/SwiftDeclSynthesizer.cpp

@@ -1910,9 +1910,7 @@ synthesizeOperatorMethodBody(AbstractFunctionDecl *afd, void *context) {
 
 FuncDecl *
 SwiftDeclSynthesizer::makeOperator(FuncDecl *operatorMethod,
-                                   clang::CXXMethodDecl *clangOperator) {
-  clang::OverloadedOperatorKind opKind = clangOperator->getOverloadedOperator();
-
+                                   clang::OverloadedOperatorKind opKind) {
   assert(opKind != clang::OverloadedOperatorKind::OO_None &&
          "expected a C++ operator");
 
@@ -1970,7 +1968,8 @@ SwiftDeclSynthesizer::makeOperator(FuncDecl *operatorMethod,
                                              operatorMethod);
 
   // If this is a unary prefix operator (e.g. `!`), add a `prefix` attribute.
-  if (clangOperator->param_empty()) {
+  size_t numParams = operatorMethod->getParameters()->size();
+  if (numParams == 0 || (operatorMethod->isStatic() && numParams == 1)) {
     topLevelStaticFuncDecl->getAttrs().add(new (ctx) PrefixAttr(SourceLoc()));
   }
 

lib/ClangImporter/SwiftDeclSynthesizer.h

@@ -285,7 +285,7 @@ class SwiftDeclSynthesizer {
   FuncDecl *makeSuccessorFunc(FuncDecl *incrementFunc);
 
   FuncDecl *makeOperator(FuncDecl *operatorMethod,
-                         clang::CXXMethodDecl *clangOperator);
+                         clang::OverloadedOperatorKind opKind);
 
   VarDecl *makeComputedPropertyFromCXXMethods(FuncDecl *getter,
                                               FuncDecl *setter);

test/Interop/Cxx/operators/Inputs/member-inline.h

@@ -440,4 +440,16 @@ struct DerivedFromAmbiguousOperatorStarPrivatelyWithUsingDecl
   using AmbiguousOperatorStar::operator*;
 };
 
+struct DerivedFromLoadableIntWrapperWithUsingDecl : private LoadableIntWrapper {
+  using LoadableIntWrapper::operator-;
+  using LoadableIntWrapper::operator+=;
+
+  int getValue() const {
+    return value;
+  }
+  void setValue(int v) {
+    this->value = v;
+  }
+};
+
 #endif

test/Interop/Cxx/operators/member-inline-module-interface.swift

@@ -265,3 +265,15 @@
 // CHECK-NEXT:   @available(*, unavailable, message: "use .pointee property")
 // CHECK-NEXT:   func __operatorStar() -> UnsafePointer<Int32>
 // CHECK-NEXT: }
+
+// CHECK: struct DerivedFromLoadableIntWrapperWithUsingDecl {
+// CHECK-NEXT:   init()
+// CHECK-NEXT:   static func - (lhs: inout DerivedFromLoadableIntWrapperWithUsingDecl, rhs: LoadableIntWrapper) -> LoadableIntWrapper
+// CHECK-NEXT:   @available(*, unavailable, message: "use - instead")
+// CHECK-NEXT:   mutating func __operatorMinus(_ rhs: LoadableIntWrapper) -> LoadableIntWrapper
+// CHECK-NEXT:   static func += (lhs: inout DerivedFromLoadableIntWrapperWithUsingDecl, rhs: LoadableIntWrapper)
+// CHECK-NEXT:   @available(*, unavailable, message: "use += instead")
+// CHECK-NEXT:   mutating func __operatorPlusEqual(_ rhs: LoadableIntWrapper)
+// CHECK-NEXT:   func getValue() -> Int32
+// CHECK-NEXT:   mutating func setValue(_ v: Int32)
+// CHECK-NEXT: }

test/Interop/Cxx/operators/member-inline-typechecker.swift

@@ -73,3 +73,6 @@ derivedConstIter.pointee // expected-error {{value of type 'DerivedFromConstIter
 
 let derivedConstIterWithUD = DerivedFromConstIteratorPrivatelyWithUsingDecl()
 let _ = derivedConstIterWithUD.pointee
+
+var derivedIntWrapper = DerivedFromLoadableIntWrapperWithUsingDecl()
+derivedIntWrapper += LoadableIntWrapper()

test/Interop/Cxx/operators/member-inline.swift

@@ -395,4 +395,13 @@ OperatorsTestSuite.test("DerivedFromAmbiguousOperatorStarPrivatelyWithUsingDecl.
   expectEqual(567, res)
 }
 
+OperatorsTestSuite.test("DerivedFromLoadableIntWrapperWithUsingDecl") {
+  var d = DerivedFromLoadableIntWrapperWithUsingDecl()
+  d.setValue(123)
+  var d1 = LoadableIntWrapper()
+  d1.value = 543
+  d += d1
+  expectEqual(666, d.getValue())
+}
+
 runAllTests()