[cxx-interop] Allow virtual methods to be renamed with SWIFT_NAME

Author: susmonteiro

lib/ClangImporter/ImportDecl.cpp

@@ -4393,7 +4393,16 @@ namespace {
             // Create a thunk that will perform dynamic dispatch.
             // TODO: we don't have to import the actual `method` in this case,
             // we can just synthesize a thunk and import that instead.
-            auto result = synthesizer.makeVirtualMethod(decl);
+            ImportedName importedName;
+            std::optional<ImportedName> correctSwiftName;
+            std::tie(importedName, correctSwiftName) = importFullName(decl);
+            if (!importedName)
+              return nullptr;
+            auto result = synthesizer.makeVirtualMethod(decl, importedName);
+
+            if (correctSwiftName)
+              markAsVariant(result, *correctSwiftName);
+
             if (result) {
               return result;
             } else {

lib/ClangImporter/SwiftDeclSynthesizer.cpp

@@ -2013,7 +2013,8 @@ clang::CXXMethodDecl *SwiftDeclSynthesizer::synthesizeCXXForwardingMethod(
     ForwardingMethodKind forwardingMethodKind,
     ReferenceReturnTypeBehaviorForBaseMethodSynthesis
         referenceReturnTypeBehavior,
-    bool forceConstQualifier) {
+    bool forceConstQualifier,
+    std::optional<importer::ImportedName> importedName) {
 
   auto &clangCtx = ImporterImpl.getClangASTContext();
   auto &clangSema = ImporterImpl.getClangSema();
@@ -2029,7 +2030,9 @@ clang::CXXMethodDecl *SwiftDeclSynthesizer::synthesizeCXXForwardingMethod(
     os << (forwardingMethodKind == ForwardingMethodKind::Virtual
                ? "__synthesizedVirtualCall_"
                : "__synthesizedBaseCall_")
-       << name.getAsIdentifierInfo()->getName();
+       << (importedName 
+               ? importedName->getDeclName().getBaseName().userFacingName()
+               : name.getAsIdentifierInfo()->getName());
     name = clang::DeclarationName(
         &ImporterImpl.getClangPreprocessor().getIdentifierTable().get(
             os.str()));
@@ -2259,9 +2262,9 @@ SwiftDeclSynthesizer::makeOperator(FuncDecl *operatorMethod,
 }
 
 // MARK: C++ virtual methods
-
 FuncDecl *SwiftDeclSynthesizer::makeVirtualMethod(
-    const clang::CXXMethodDecl *clangMethodDecl) {
+    const clang::CXXMethodDecl *clangMethodDecl,
+    importer::ImportedName importedName) {
   auto clangDC = clangMethodDecl->getParent();
   auto &ctx = ImporterImpl.SwiftContext;
 
@@ -2271,7 +2274,7 @@ FuncDecl *SwiftDeclSynthesizer::makeVirtualMethod(
   auto newMethod = synthesizeCXXForwardingMethod(
       clangDC, clangDC, clangMethodDecl, ForwardingMethodKind::Virtual,
       ReferenceReturnTypeBehaviorForBaseMethodSynthesis::KeepReference,
-      /*forceConstQualifier*/ false);
+      /*forceConstQualifier*/ false, importedName);
 
   auto result = dyn_cast_or_null<FuncDecl>(
       ctx.getClangModuleLoader()->importDeclDirectly(newMethod));

lib/ClangImporter/SwiftDeclSynthesizer.h

@@ -318,11 +318,13 @@ class SwiftDeclSynthesizer {
       ReferenceReturnTypeBehaviorForBaseMethodSynthesis
           referenceReturnTypeBehavior =
               ReferenceReturnTypeBehaviorForBaseMethodSynthesis::KeepReference,
-      bool forceConstQualifier = false);
+      bool forceConstQualifier = false,
+      std::optional<importer::ImportedName> importedName = std::nullopt);
 
   /// Given an overload of a C++ virtual method on a reference type, create a
   /// method that dispatches the call dynamically.
-  FuncDecl *makeVirtualMethod(const clang::CXXMethodDecl *clangMethodDecl);
+  FuncDecl *makeVirtualMethod(const clang::CXXMethodDecl *clangMethodDecl,
+                              importer::ImportedName importedName);
 
   FuncDecl *makeInstanceToStaticOperatorCallMethod(
       const clang::CXXMethodDecl *clangMethodDecl);

test/Interop/Cxx/class/inheritance/Inputs/virtual-methods.h

@@ -6,6 +6,8 @@ inline void testFunctionCollected() {
 
 struct Base {
   virtual void foo() = 0;
+  virtual void virtualRename() const
+      __attribute__((swift_name("swiftVirtualRename()")));
 };
 
 struct Base2 { virtual int f() = 0; };
@@ -83,6 +85,8 @@ struct IMMORTAL_FRT DerivedFromImmortal : public Immortal {
 struct IMMORTAL_FRT Immortal2 {
 public:
   virtual void virtualMethod(HasDestructor) = 0;
+  virtual void virtualRename() const
+      __attribute__((swift_name("swiftVirtualRename()")));
 };
 
 inline const ImmortalBase *_Nonnull castToImmortalBase(

test/Interop/Cxx/class/inheritance/virtual-methods-typechecker.swift

@@ -37,3 +37,14 @@ func takesDerivedFromImmortal(_ i: DerivedFromImmortal) {
   let _ = i.getIntValue()
   i.setIntValue(1)
 }
+
+func callVirtualRenamedMethod(_ b: Base) {
+  b.virtualRename()  // expected-error {{value of type 'Base' has no member 'virtualRename'}}
+  b.swiftVirtualRename()
+}
+
+@available(SwiftStdlib 5.8, *)
+func callsRenamedVirtualMethodsInFRT(_ i: Immortal2) {
+  i.virtualRename()  // expected-error {{value of type 'Immortal2' has no member 'virtualRename'}}
+  i.swiftVirtualRename()
+}