[cxx-interop] Fix extra indirection when exporting CFData arguments/return values

The clang nodes associated with Swift's Core Foundation types can already be
represented by a pointer. The interop code does not need to add an extra
layer of indirection in those cases.

rdar://119840281

Author: Gabor Horvath

include/swift/ClangImporter/ClangImporter.h

@@ -678,6 +678,12 @@ getCxxReferencePointeeTypeOrNone(const clang::Type *type);
 /// Returns true if the given type is a C++ `const` reference type.
 bool isCxxConstReferenceType(const clang::Type *type);
 
+/// Determine whether this typedef is a CF type.
+bool isCFTypeDecl(const clang::TypedefNameDecl *Decl);
+
+/// Determine the imported CF type for the given typedef-name, or the empty
+/// string if this is not an imported CF type name.
+llvm::StringRef getCFTypeName(const clang::TypedefNameDecl *decl);
 } // namespace importer
 
 struct ClangInvocationFileMapping {

lib/ClangImporter/CFTypeInfo.h

@@ -107,13 +107,6 @@ class CFPointeeInfo {
     return Decl.get<const clang::TypedefNameDecl *>();
   }
 };
-
-/// Determine whether this typedef is a CF type.
-bool isCFTypeDecl(const clang::TypedefNameDecl *Decl);
-
-/// Determine the imported CF type for the given typedef-name, or the empty
-/// string if this is not an imported CF type name.
-llvm::StringRef getCFTypeName(const clang::TypedefNameDecl *decl);
 }
 }
 

lib/PrintAsClang/PrintClangFunction.cpp

@@ -31,6 +31,7 @@
 #include "swift/IRGen/IRABIDetailsProvider.h"
 #include "clang/AST/ASTContext.h"
 #include "clang/AST/Attr.h"
+#include "clang/AST/Decl.h"
 #include "clang/AST/DeclObjC.h"
 #include "llvm/ADT/STLExtras.h"
 
@@ -273,8 +274,13 @@ class CFunctionSignatureTypePrinter
                  bool isInOutParam) {
     auto *cd = CT->getDecl();
     if (cd->hasClangNode()) {
-      ClangSyntaxPrinter(os).printClangTypeReference(cd->getClangDecl());
-      os << " *"
+      const auto *clangDecl = cd->getClangDecl();
+      ClangSyntaxPrinter(os).printClangTypeReference(clangDecl);
+      bool alreadyPointer = false;
+      if (const auto *typedefDecl = dyn_cast<clang::TypedefNameDecl>(clangDecl))
+        if (importer::isCFTypeDecl(typedefDecl))
+          alreadyPointer = true;
+      os << (alreadyPointer ? " " : " *")
          << (!optionalKind || *optionalKind == OTK_None ? "_Nonnull"
                                                         : "_Nullable");
       if (isInOutParam) {

test/Interop/SwiftToCxx/stdlib/core-foundation-types-in-cxx.swift

@@ -0,0 +1,14 @@
+// RUN: %empty-directory(%t)
+
+// RUN: %target-swift-frontend -typecheck %s -typecheck -module-name UseCoreFoundation -enable-experimental-cxx-interop -clang-header-expose-decls=all-public -emit-clang-header-path %t/UseCoreFoundation.h
+// RUN: %FileCheck %s < %t/UseCoreFoundation.h
+
+// REQUIRES: objc_interop
+
+import CoreFoundation
+
+public func foobar(_ a: CFData) -> Bool {
+    true
+}
+
+// CHECK: SWIFT_EXTERN bool $s17UseCoreFoundation6foobarySbSo9CFDataRefaF(CFDataRef _Nonnull a) SWIFT_NOEXCEPT SWIFT_CALL; // foobar(_:)