[cxx-interop] Support importing subscript operators with multiple params

Gabor Horvath · Gabor Horvath · commit e4a120b63ca9 · 2025-08-05T15:27:53.000+01:00
Previously, the compiler would crash on them.

rdar://133541125
diff --git a/lib/ClangImporter/ImportDecl.cpp b/lib/ClangImporter/ImportDecl.cpp
@@ -2647,22 +2647,23 @@ namespace {
           result->addMember(p);
         }
 
-        for (auto &subscriptInfo : Impl.cxxSubscripts) {
-          auto declAndParameterType = subscriptInfo.first;
-          if (declAndParameterType.first != result)
-            continue;
-
-          auto getterAndSetter = subscriptInfo.second;
-          auto subscript = synthesizer.makeSubscript(getterAndSetter.first,
-                                                     getterAndSetter.second);
-          // Also add subscripts directly because they won't be found from the
-          // clang decl.
-          result->addMember(subscript);
-
-          // Add the subscript as an alternative for the getter so that it gets
-          // carried into derived classes.
-          auto *subscriptImpl = getterAndSetter.first ? getterAndSetter.first : getterAndSetter.second;
-          Impl.addAlternateDecl(subscriptImpl, subscript);
+        auto it = Impl.cxxSubscripts.find(result);
+        if (it != Impl.cxxSubscripts.end()) {
+          for (auto &subscriptInfo : it->second) {
+            auto getterAndSetter = subscriptInfo.second;
+            auto subscript = synthesizer.makeSubscript(getterAndSetter.first,
+                                                       getterAndSetter.second);
+            // Also add subscripts directly because they won't be found from the
+            // clang decl.
+            result->addMember(subscript);
+
+            // Add the subscript as an alternative for the getter so that it
+            // gets carried into derived classes.
+            auto *subscriptImpl = getterAndSetter.first
+                                      ? getterAndSetter.first
+                                      : getterAndSetter.second;
+            Impl.addAlternateDecl(subscriptImpl, subscript);
+          }
         }
 
         auto getterAndSetterIt = Impl.cxxDereferenceOperators.find(result);
@@ -3633,14 +3634,16 @@ namespace {
         return true;
 
       if (importedName.isSubscriptAccessor()) {
-        assert(func->getParameters()->size() == 1);
-        auto parameter = func->getParameters()->get(0);
-        auto parameterType = parameter->getTypeInContext();
-        if (!typeDecl || !parameterType)
-          return false;
-        if (parameter->isInOut())
-          // Subscripts with inout parameters are not allowed in Swift.
-          return false;
+        SmallVector<TypeBase *> params;
+        for (auto parameter : *(func->getParameters())) {
+          auto parameterType = parameter->getTypeInContext();
+          if (!typeDecl || !parameterType)
+            return false;
+          if (parameter->isInOut())
+            // Subscripts with inout parameters are not allowed in Swift.
+            return false;
+          params.push_back(parameterType.getPointer());
+        }
         // Subscript setter is marked as mutating in Swift even if the
         // C++ `operator []` is `const`.
         if (importedName.getAccessorKind() ==
@@ -3649,7 +3652,8 @@ namespace {
             !typeDecl->getDeclaredType()->isForeignReferenceType())
           func->setSelfAccessKind(SelfAccessKind::Mutating);
 
-        auto &getterAndSetter = Impl.cxxSubscripts[{typeDecl, parameterType}];
+        auto &getterAndSetterMap = Impl.cxxSubscripts[typeDecl];
+        auto &getterAndSetter = getterAndSetterMap[params];
 
         switch (importedName.getAccessorKind()) {
         case ImportedAccessorKind::SubscriptGetter:
diff --git a/lib/ClangImporter/ImporterImpl.h b/lib/ClangImporter/ImporterImpl.h
@@ -25,6 +25,7 @@
 #include "swift/AST/ASTContext.h"
 #include "swift/AST/Decl.h"
 #include "swift/AST/ForeignErrorConvention.h"
+#include "swift/AST/Identifier.h"
 #include "swift/AST/LazyResolver.h"
 #include "swift/AST/Module.h"
 #include "swift/AST/RequirementSignature.h"
@@ -683,8 +684,11 @@ class LLVM_LIBRARY_VISIBILITY ClangImporter::Implementation
   ///
   /// `.first` corresponds to a getter
   /// `.second` corresponds to a setter
-  llvm::MapVector<std::pair<NominalTypeDecl *, Type>,
-                  std::pair<FuncDecl *, FuncDecl *>> cxxSubscripts;
+  llvm::DenseMap<NominalTypeDecl *,
+                 llvm::MapVector<SmallVector<TypeBase *>,
+                                 std::pair<FuncDecl *, FuncDecl *>,
+                                 std::map<SmallVector<TypeBase *>, unsigned>>>
+      cxxSubscripts;
 
   llvm::MapVector<NominalTypeDecl *, std::pair<FuncDecl *, FuncDecl *>>
       cxxDereferenceOperators;
diff --git a/lib/ClangImporter/SwiftDeclSynthesizer.cpp b/lib/ClangImporter/SwiftDeclSynthesizer.cpp
@@ -10,8 +10,8 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include "CXXMethodBridging.h"
 #include "SwiftDeclSynthesizer.h"
+#include "CXXMethodBridging.h"
 #include "swift/AST/ASTMangler.h"
 #include "swift/AST/Attr.h"
 #include "swift/AST/AttrKind.h"
@@ -47,7 +47,7 @@ static Argument createSelfArg(AccessorDecl *accessorDecl) {
 
 static CallExpr *createAccessorImplCallExpr(FuncDecl *accessorImpl,
                                             Argument selfArg,
-                                            DeclRefExpr *keyRefExpr = nullptr) {
+                                            ArrayRef<Expr *> keyRefExprs) {
   ASTContext &ctx = accessorImpl->getASTContext();
 
   auto accessorImplExpr =
@@ -60,12 +60,8 @@ static CallExpr *createAccessorImplCallExpr(FuncDecl *accessorImpl,
   accessorImplDotCallExpr->setType(accessorImpl->getMethodInterfaceType());
   accessorImplDotCallExpr->setThrows(nullptr);
 
-  ArgumentList *argList;
-  if (keyRefExpr) {
-    argList = ArgumentList::forImplicitUnlabeled(ctx, {keyRefExpr});
-  } else {
-    argList = ArgumentList::forImplicitUnlabeled(ctx, {});
-  }
+  ArgumentList *argList = ArgumentList::forImplicitUnlabeled(ctx, keyRefExprs);
+
   auto *accessorImplCallExpr =
       CallExpr::createImplicit(ctx, accessorImplDotCallExpr, argList);
   accessorImplCallExpr->setType(accessorImpl->getResultInterfaceType());
@@ -1556,33 +1552,36 @@ synthesizeUnwrappingGetterOrAddressGetterBody(AbstractFunctionDecl *afd,
   ASTContext &ctx = getterDecl->getASTContext();
 
   auto selfArg = createSelfArg(getterDecl);
-  DeclRefExpr *keyRefExpr = getterDecl->getParameters()->size() == 0
-                                ? nullptr
-                                : createParamRefExpr(getterDecl, 0);
+  SmallVector<Expr *> arguments;
+  for (size_t idx = 0, end = getterDecl->getParameters()->size(); idx < end;
+       ++idx)
+    arguments.push_back(createParamRefExpr(getterDecl, idx));
 
   Type elementTy = getterDecl->getResultInterfaceType();
 
   auto *getterImplCallExpr =
-      createAccessorImplCallExpr(getterImpl, selfArg, keyRefExpr);
+      createAccessorImplCallExpr(getterImpl, selfArg, arguments);
 
   // This default handles C++'s operator[] that returns a value type.
   Expr *propertyExpr = getterImplCallExpr;
   PointerTypeKind ptrKind;
 
-  // The following check returns true if the subscript operator returns a C++
-  // reference type. This check actually checks to see if the type is a pointer
-  // type, but this does not apply to C pointers because they are Optional types
-  // when imported. TODO: Use a more obvious check here.
+  // The following check returns true if the subscript operator returns a
+  // C++ reference type. This check actually checks to see if the type is
+  // a pointer type, but this does not apply to C pointers because they
+  // are Optional types when imported. TODO: Use a more obvious check
+  // here.
   if (!isAddress &&
       getterImpl->getResultInterfaceType()->getAnyPointerElementType(ptrKind)) {
-    // `getterImpl` can return either UnsafePointer or UnsafeMutablePointer.
-    // Retrieve the corresponding `.pointee` declaration.
+    // `getterImpl` can return either UnsafePointer or
+    // UnsafeMutablePointer. Retrieve the corresponding `.pointee`
+    // declaration.
     VarDecl *pointeePropertyDecl = ctx.getPointerPointeePropertyDecl(ptrKind);
 
     // Handle operator[] that returns a reference type.
-    SubstitutionMap subMap = SubstitutionMap::get(
-        ctx.getUnsafePointerDecl()->getGenericSignature(), {elementTy},
-        LookUpConformanceInModule());
+    SubstitutionMap subMap =
+        SubstitutionMap::get(ctx.getUnsafePointerDecl()->getGenericSignature(),
+                             {elementTy}, LookUpConformanceInModule());
     auto pointeePropertyRefExpr = new (ctx) MemberRefExpr(
         getterImplCallExpr, SourceLoc(),
         ConcreteDeclRef(pointeePropertyDecl, subMap), DeclNameLoc(),
@@ -1627,16 +1626,15 @@ synthesizeUnwrappingSetterBody(AbstractFunctionDecl *afd, void *context) {
 
   auto selfArg = createSelfArg(setterDecl);
   DeclRefExpr *valueParamRefExpr = createParamRefExpr(setterDecl, 0);
-  // For a subscript this decl will have two parameters, for a pointee property
-  // it will only have one.
-  DeclRefExpr *keyParamRefExpr = setterDecl->getParameters()->size() == 1
-                                     ? nullptr
-                                     : createParamRefExpr(setterDecl, 1);
+  SmallVector<Expr *> arguments;
+  for (size_t idx = 1, end = setterDecl->getParameters()->size(); idx < end;
+       ++idx)
+    arguments.push_back(createParamRefExpr(setterDecl, idx));
 
   Type elementTy = valueParamRefExpr->getDecl()->getInterfaceType();
 
   auto *setterImplCallExpr =
-      createAccessorImplCallExpr(setterImpl, selfArg, keyParamRefExpr);
+      createAccessorImplCallExpr(setterImpl, selfArg, arguments);
 
   VarDecl *pointeePropertyDecl =
       ctx.getPointerPointeePropertyDecl(PTK_UnsafeMutablePointer);
@@ -1673,7 +1671,7 @@ synthesizeUnwrappingAddressSetterBody(AbstractFunctionDecl *afd,
 
   auto selfArg = createSelfArg(setterDecl);
   auto *setterImplCallExpr =
-      createAccessorImplCallExpr(setterImpl, selfArg, nullptr);
+      createAccessorImplCallExpr(setterImpl, selfArg, {});
 
   auto *returnStmt = ReturnStmt::createImplicit(ctx, setterImplCallExpr);
 
@@ -1701,15 +1699,16 @@ SubscriptDecl *SwiftDeclSynthesizer::makeSubscript(FuncDecl *getter,
 
   auto &ctx = ImporterImpl.SwiftContext;
 
-  assert(getterImpl->getParameters()->size() == 1 &&
-         "subscript can only have 1 parameter");
-  auto bodyParam = ParamDecl::clone(ctx, getterImpl->getParameters()->get(0));
-  // If the subscript parameter is unnamed, give it a name to make sure SILGen
-  // creates a variable for it.
-  if (bodyParam->getName().empty())
-    bodyParam->setName(ctx.getIdentifier("__index"));
-
-  auto bodyParams = ParameterList::create(ctx, bodyParam);
+  SmallVector<ParamDecl *> paramVec;
+  for (auto [i, param] : llvm::enumerate(*getterImpl->getParameters())) {
+    auto clonedParam = ParamDecl::clone(ctx, param);
+    // If the subscript parameter is unnamed, give it a name to make sure SILGen
+    // creates a variable for it.
+    if (clonedParam->getName().empty())
+      clonedParam->setName(ctx.getIdentifier("__index" + std::to_string(i)));
+    paramVec.push_back(clonedParam);
+  }
+  auto bodyParams = ParameterList::create(ctx, paramVec);
   DeclName name(ctx, DeclBaseName::createSubscript(), bodyParams);
   auto dc = getterImpl->getDeclContext();
 
@@ -1744,8 +1743,11 @@ SubscriptDecl *SwiftDeclSynthesizer::makeSubscript(FuncDecl *getter,
     paramVarDecl->setSpecifier(ParamSpecifier::Default);
     paramVarDecl->setInterfaceType(elementTy);
 
-    auto setterParamList =
-        ParameterList::create(ctx, {paramVarDecl, bodyParams->get(0)});
+    SmallVector<ParamDecl *> setterParams;
+    setterParams.push_back(paramVarDecl);
+    setterParams.append(bodyParams->begin(), bodyParams->end());
+
+    auto setterParamList = ParameterList::create(ctx, setterParams);
 
     setterDecl = AccessorDecl::create(
         ctx, setterImpl->getLoc(), setterImpl->getLoc(), AccessorKind::Set,
@@ -1918,7 +1920,7 @@ synthesizeSuccessorFuncBody(AbstractFunctionDecl *afd, void *context) {
 
   // Call `operator++`.
   auto incrementExpr = createAccessorImplCallExpr(
-      incrementImpl, Argument::implicitInOut(ctx, copyRefLValueExpr));
+      incrementImpl, Argument::implicitInOut(ctx, copyRefLValueExpr), {});
 
   auto copyRefRValueExpr = new (ctx) DeclRefExpr(copyDecl, DeclNameLoc(),
                                                  /*implicit*/ true);
@@ -2331,7 +2333,7 @@ synthesizeComputedGetterFromCXXMethod(AbstractFunctionDecl *afd,
 
   auto selfArg = createSelfArg(accessor);
 
-  auto *getterImplCallExpr = createAccessorImplCallExpr(method, selfArg);
+  auto *getterImplCallExpr = createAccessorImplCallExpr(method, selfArg, {});
   auto &ctx = method->getASTContext();
   auto *returnStmt = ReturnStmt::createImplicit(ctx, getterImplCallExpr);
   auto *body = BraceStmt::create(ctx, SourceLoc(), {returnStmt}, SourceLoc());
@@ -2349,7 +2351,7 @@ synthesizeComputedSetterFromCXXMethod(AbstractFunctionDecl *afd,
   DeclRefExpr *valueParamRefExpr = createParamRefExpr(setterDecl, 0);
 
   auto *getterImplCallExpr =
-      createAccessorImplCallExpr(setterImpl, selfArg, valueParamRefExpr);
+      createAccessorImplCallExpr(setterImpl, selfArg, {valueParamRefExpr});
 
   auto body = BraceStmt::create(setterImpl->getASTContext(), SourceLoc(),
                                 {getterImplCallExpr}, SourceLoc());
diff --git a/test/Interop/Cxx/operators/Inputs/member-inline.h b/test/Interop/Cxx/operators/Inputs/member-inline.h
@@ -157,6 +157,20 @@ struct ReadWriteIntArray {
   };
 };
 
+#if __cplusplus >= 202302L
+struct NullarySubscript {
+  int operator[]() const { return 42; }
+  int &operator[]() { return field; }
+  int field;
+};
+
+struct BinarySubscript {
+  int operator[](int x, int y) const { return x + y; }
+  int &operator[](int, int) { return field; }
+  int field;
+};
+#endif
+
 struct __attribute__((swift_attr("import_owned"))) ReadOnlyIntArray {
 private:
   int values[5] = { 1, 2, 3, 4, 5 };
diff --git a/test/Interop/Cxx/operators/member-inline-module-interface.swift b/test/Interop/Cxx/operators/member-inline-module-interface.swift
@@ -1,6 +1,6 @@
-// RUN: %target-swift-ide-test -print-module -module-to-print=MemberInline -I %S/Inputs -source-filename=x -cxx-interoperability-mode=swift-5.9 | %FileCheck %s
-// RUN: %target-swift-ide-test -print-module -module-to-print=MemberInline -I %S/Inputs -source-filename=x -cxx-interoperability-mode=swift-6 | %FileCheck %s
-// RUN: %target-swift-ide-test -print-module -module-to-print=MemberInline -I %S/Inputs -source-filename=x -cxx-interoperability-mode=upcoming-swift | %FileCheck %s
+// RUN: %target-swift-ide-test -print-module -module-to-print=MemberInline -I %S/Inputs -source-filename=x -cxx-interoperability-mode=swift-5.9 -Xcc -std=c++23 | %FileCheck %s
+// RUN: %target-swift-ide-test -print-module -module-to-print=MemberInline -I %S/Inputs -source-filename=x -cxx-interoperability-mode=swift-6 -Xcc -std=c++23 | %FileCheck %s
+// RUN: %target-swift-ide-test -print-module -module-to-print=MemberInline -I %S/Inputs -source-filename=x -cxx-interoperability-mode=upcoming-swift -Xcc -std=c++23 | %FileCheck %s
 
 // CHECK: struct LoadableIntWrapper {
 // CHECK:   func successor() -> LoadableIntWrapper
@@ -58,6 +58,21 @@
 // CHECK:   }
 // CHECK: }
 
+// CHECK: struct NullarySubscript {
+// CHECK:   subscript() -> Int32
+// CHECK:   @available(*, unavailable, message: "use subscript")
+// CHECK:   func __operatorSubscriptConst() -> Int32
+// CHECK:   @available(*, unavailable, message: "use subscript")
+// CHECK:   mutating func __operatorSubscript() -> UnsafeMutablePointer<Int32>
+// CHECK: }
+
+// CHECK: struct BinarySubscript {
+// CHECK:   subscript(x: Int32, y: Int32) -> Int32
+// CHECK:   @available(*, unavailable, message: "use subscript")
+// CHECK:   func __operatorSubscriptConst(_ x: Int32, _ y: Int32) -> Int32
+// CHECK:   @available(*, unavailable, message: "use subscript")
+// CHECK:   mutating func __operatorSubscript(_: Int32, _: Int32) -> UnsafeMutablePointer<Int32>
+// CHECK: }
 
 // CHECK: struct ReadOnlyIntArray {
 // CHECK:   subscript(x: Int32) -> Int32 { get }
@@ -212,10 +227,10 @@
 // CHECK: }
 
 // CHECK: struct SubscriptUnnamedParameter {
-// CHECK:   subscript(__index: Int32) -> Int32 { get }
+// CHECK:   subscript(__index0: Int32) -> Int32 { get }
 // CHECK: }
 // CHECK: struct SubscriptUnnamedParameterReadWrite {
-// CHECK:   subscript(__index: Int32) -> Int32
+// CHECK:   subscript(__index0: Int32) -> Int32
 // CHECK: }
 
 // CHECK: struct Iterator {
diff --git a/test/Interop/Cxx/operators/member-inline.swift b/test/Interop/Cxx/operators/member-inline.swift
@@ -1,6 +1,6 @@
 // RUN: %target-run-simple-swift(-I %S/Inputs -Xfrontend -cxx-interoperability-mode=swift-5.9)
 // RUN: %target-run-simple-swift(-I %S/Inputs -Xfrontend -cxx-interoperability-mode=swift-6)
-// RUN: %target-run-simple-swift(-I %S/Inputs -Xfrontend -cxx-interoperability-mode=upcoming-swift)
+// RUN: %target-run-simple-swift(-I %S/Inputs -Xfrontend -cxx-interoperability-mode=upcoming-swift -Xcc -std=c++23 -D CPP23)
 //
 // REQUIRES: executable_test
 
@@ -185,6 +185,20 @@ OperatorsTestSuite.test("ReadWriteIntArray.subscript (inline)") {
   expectEqual(234, resultAfter)
 }
 
+#if CPP23
+OperatorsTestSuite.test("Subscript operators with parameter number != 1") {
+  var ns = NullarySubscript()
+  expectEqual(42, ns[])
+  ns[] = 5
+  expectEqual(5, ns.field)
+
+  var bs = BinarySubscript()
+  expectEqual(10, bs[3, 7])
+  bs[1, 2] = 6
+  expectEqual(6, bs.field)
+}
+#endif
+
 OperatorsTestSuite.test("DerivedFromReadWriteIntArray.subscript (inline, base class)") {
   var arr = DerivedFromReadWriteIntArray()
 
