[Interop][SwiftToCxx] Implement the new enum header design

WANGJIEKE · WANGJIEKE · commit 482e1ac80f1d · 2022-08-15T15:31:43.000-07:00
diff --git a/docs/CppInteroperability/UserGuide-CallingSwiftFromC++.md b/docs/CppInteroperability/UserGuide-CallingSwiftFromC++.md
@@ -595,7 +595,7 @@ enum value will abort the program.
 A resilient Swift enumeration value could represent a case that's unknown to the client.
 Swift forces the client to check if the value is `@uknown default` when switching over
 the enumeration to account for that. C++ follows a similar principle,
-by exposing an `unknown_default` case that can then be matched in a switch.
+by exposing an `unknownDefault` case that can then be matched in a switch.
 
 For example, given the following resilient enumeration:
 
@@ -620,14 +620,14 @@ void test(const DateFormatStyle &style) {
   case DateFormatStyle::full:
     ...
     break;
-  case DateFormatStyle::unknown_default: // just like Swift's @unknown default
+  case DateFormatStyle::unknownDefault: // just like Swift's @unknown default
     // Some case value added in a future version of enum.
     break;
   }
 }
 ```
 
-The `unknown_default` case value is not a constructible case and you will get a compiler error if you try to construct it in C++.
+The `unknownDefault` case value is not a constructible case and you will get a compiler error if you try to construct it in C++.
 
 ## Using Swift Class Types
 
diff --git a/lib/PrintAsClang/DeclAndTypePrinter.cpp b/lib/PrintAsClang/DeclAndTypePrinter.cpp
@@ -414,107 +414,68 @@ class DeclAndTypePrinter::Implementation
         return p1.second.tag < p2.second.tag;
       });
 
-      if (elementTagMapping.empty()) {
-        os << "\n";
-        return;
-      }
-
-      os << "  enum class cases {\n";
-      for (const auto &pair : elementTagMapping) {
-        os << "    ";
+      os << '\n';
+      os << "  enum class cases {";
+      llvm::interleave(elementTagMapping, os, [&](const auto &pair){
+        os << "\n    ";
         syntaxPrinter.printIdentifier(pair.first->getNameStr());
-        os << ",\n";
-      }
-      os << "  };\n"; // enum class cases' closing bracket
-
-      // Printing operator cases()
-      os << "  inline operator cases() const {\n";
-      if (ED->isResilient()) {
-        os << "    auto tag = _getEnumTag();\n";
-        for (const auto &pair : elementTagMapping) {
-          os << "    if (tag == " << cxx_synthesis::getCxxImplNamespaceName();
-          os << "::" << pair.second.globalVariableName << ") return cases::";
-          syntaxPrinter.printIdentifier(pair.first->getNameStr());
-          os << ";\n";
-        }
-        // TODO: change to Swift's fatalError when it's available in C++
-        os << "    abort();\n";
-      } else { // non-resilient enum
-        os << "    switch (_getEnumTag()) {\n";
-        for (const auto &pair : elementTagMapping) {
-          os << "      case " << pair.second.tag << ": return cases::";
-          syntaxPrinter.printIdentifier(pair.first->getNameStr());
-          os << ";\n";
-        }
-        // TODO: change to Swift's fatalError when it's available in C++
-        os << "      default: abort();\n";
-        os << "    }\n"; // switch's closing bracket
-      }
-      os << "  }\n";   // operator cases()'s closing bracket
-
+      }, ",");
+      // TODO: allow custom name for this special case
+      auto resilientUnknownDefaultCaseName = "unknownDefault";
       if (ED->isResilient()) {
-        os << "  inline bool inResilientUnknownCase() const {\n";
-        os << "    auto tag = _getEnumTag();\n";
-        os << "    return";
-        llvm::interleave(
-            elementTagMapping, os,
-            [&](const auto &pair) {
-              os << "\n      tag != " << cxx_synthesis::getCxxImplNamespaceName()
-                 << "::" << pair.second.globalVariableName;
-            },
-            " &&");
-        os << ";\n";
-        os << "  }\n";
+        os << ",\n    " << resilientUnknownDefaultCaseName;
       }
-
-      // Printing case-related functions
+      os << "\n  };\n\n"; // enum class cases' closing bracket
+      
+      // Printing struct, is, and get functions for each case
       DeclAndTypeClangFunctionPrinter clangFuncPrinter(
           os, owningPrinter.prologueOS, owningPrinter.typeMapping,
           owningPrinter.interopContext);
-
-      for (const auto &pair : elementTagMapping) {
+      
+      auto printIsFunction = [&](StringRef caseName, EnumDecl *ED) {
         os << "  inline bool is";
-        auto name = pair.first->getNameStr().str();
+        std::string name;
+        llvm::raw_string_ostream nameStream(name);
+        ClangSyntaxPrinter(nameStream).printIdentifier(caseName);
         name[0] = std::toupper(name[0]);
         os << name << "() const {\n";
-        os << "    return _getEnumTag() == ";
-        if (ED->isResilient()) {
-          os << cxx_synthesis::getCxxImplNamespaceName()
-             << "::" << pair.second.globalVariableName;
-        } else {
-          os << pair.second.tag;
-        }
-        os << ";\n  }\n";
-
-        if (!pair.first->hasAssociatedValues()) {
-          continue;
-        }
-
-        auto associatedValueList = pair.first->getParameterList();
+        os << "    return *this == ";
+        syntaxPrinter.printBaseName(ED);
+        os << "::";
+        syntaxPrinter.printIdentifier(caseName);
+        os << ";\n";
+        os << "  }\n";
+      };
+      
+      auto printGetFunction = [&](EnumElementDecl *elementDecl) {
+        auto associatedValueList = elementDecl->getParameterList();
         // TODO: add tuple type support
         if (associatedValueList->size() > 1) {
-          continue;
+          return;
         }
         auto firstType = associatedValueList->front()->getType();
         auto firstTypeDecl = firstType->getNominalOrBoundGenericNominal();
         OptionalTypeKind optKind;
         std::tie(firstType, optKind) =
             getObjectTypeAndOptionality(firstTypeDecl, firstType);
-
-        // FIXME: (tongjie) may have to forward declare return type
+        
+        auto name = elementDecl->getNameStr().str();
+        name[0] = std::toupper(name[0]);
+        
+        // FIXME: may have to forward declare return type
         os << "  inline ";
         clangFuncPrinter.printClangFunctionReturnType(
             firstType, optKind, firstTypeDecl->getModuleContext(),
             owningPrinter.outputLang);
         os << " get" << name << "() const {\n";
         os << "    if (!is" << name << "()) abort();\n";
         os << "    alignas(";
-        syntaxPrinter.printBaseName(ED);
+        syntaxPrinter.printBaseName(elementDecl->getParentEnum());
         os << ") unsigned char buffer[sizeof(";
-        syntaxPrinter.printBaseName(ED);
+        syntaxPrinter.printBaseName(elementDecl->getParentEnum());
         os << ")];\n";
         os << "    auto *thisCopy = new(buffer) ";
-        syntaxPrinter.printBaseName(ED);
+        syntaxPrinter.printBaseName(elementDecl->getParentEnum());
         os << "(*this);\n";
         os << "    char * _Nonnull payloadFromDestruction = "
               "thisCopy->_destructiveProjectEnumData();\n";
@@ -531,7 +492,7 @@ class DeclAndTypePrinter::Implementation
         } else {
           os << "    return ";
           syntaxPrinter.printModuleNamespaceQualifiersIfNeeded(
-              firstTypeDecl->getModuleContext(), ED->getModuleContext());
+              firstTypeDecl->getModuleContext(), elementDecl->getParentEnum()->getModuleContext());
           os << cxx_synthesis::getCxxImplNamespaceName();
           os << "::";
           ClangValueTypePrinter::printCxxImplClassName(os, firstTypeDecl);
@@ -542,8 +503,77 @@ class DeclAndTypePrinter::Implementation
           os << "::initializeWithTake(result, payloadFromDestruction);\n";
           os << "    });\n";
         }
-        os << "  }\n";
+        os << "  }\n";  // closing bracket of get function
+      };
+      
+      auto printStruct = [&](StringRef caseName, EnumElementDecl *elementDecl) {
+        os << "  static struct {  // impl struct for case " << caseName << '\n';
+        os << "    inline constexpr operator cases() const {\n";
+        os << "      return cases::";
+        syntaxPrinter.printIdentifier(caseName);
+        os << ";\n";
+        os << "    }\n";
+        if (elementDecl != nullptr) {
+          os << "    inline ";
+          syntaxPrinter.printBaseName(elementDecl->getParentEnum());
+          os << " operator()(";
+          // TODO: implement parameter for associated value
+          os << ") const {\n";
+          // TODO: print _make for now; need to implement actual code making an enum
+          os << "      return ";
+          syntaxPrinter.printBaseName(elementDecl->getParentEnum());
+          os << "::_make();\n";
+          os << "    }\n";
+        }
+        os << "  } ";
+        syntaxPrinter.printIdentifier(caseName);
+        os << ";\n";
+      };
+
+      for (const auto &pair : elementTagMapping) {
+        // Printing struct
+        printStruct(pair.first->getNameStr(), pair.first);
+        // Printing `is` function
+        printIsFunction(pair.first->getNameStr(), ED);
+        if (pair.first->hasAssociatedValues()) {
+          // Printing `get` function
+          printGetFunction(pair.first);
+        }
+        os << '\n';
+      }
+      
+      if (ED->isResilient()) {
+        // Printing struct for unknownDefault
+        printStruct(resilientUnknownDefaultCaseName, /* elementDecl */ nullptr);
+        // Printing isUnknownDefault
+        printIsFunction(resilientUnknownDefaultCaseName, ED);
+        os << '\n';
+      }
+      os << '\n';
+      
+      // Printing operator cases()
+      os << "  inline operator cases() const {\n";
+      if (ED->isResilient()) {
+        os << "    auto tag = _getEnumTag();\n";
+        for (const auto &pair : elementTagMapping) {
+          os << "    if (tag == " << cxx_synthesis::getCxxImplNamespaceName();
+          os << "::" << pair.second.globalVariableName << ") return cases::";
+          syntaxPrinter.printIdentifier(pair.first->getNameStr());
+          os << ";\n";
+        }
+        os << "    return cases::" << resilientUnknownDefaultCaseName << ";\n";
+      } else { // non-resilient enum
+        os << "    switch (_getEnumTag()) {\n";
+        for (const auto &pair : elementTagMapping) {
+          os << "      case " << pair.second.tag << ": return cases::";
+          syntaxPrinter.printIdentifier(pair.first->getNameStr());
+          os << ";\n";
+        }
+        // TODO: change to Swift's fatalError when it's available in C++
+        os << "      default: abort();\n";
+        os << "    }\n"; // switch's closing bracket
       }
+      os << "  }\n";   // operator cases()'s closing bracket
       os << "\n";
     });
     os << outOfLineDefinitions;
diff --git a/lib/PrintAsClang/PrintClangValueType.cpp b/lib/PrintAsClang/PrintClangValueType.cpp
@@ -254,7 +254,35 @@ void ClangValueTypePrinter::printValueTypeDecl(
   os << "  friend class " << cxx_synthesis::getCxxImplNamespaceName() << "::";
   printCxxImplClassName(os, typeDecl);
   os << ";\n";
-  os << "};\n\n";
+  os << "};\n";
+  // Print the definition of enum static struct data memebers
+  if (isa<EnumDecl>(typeDecl)) {
+    auto tagMapping = interopContext.getIrABIDetails().getEnumTagMapping(cast<EnumDecl>(typeDecl));
+    for (const auto& pair : tagMapping) {
+      os << "decltype(";
+      printer.printBaseName(typeDecl);
+      os << "::";
+      printer.printIdentifier(pair.first->getNameStr());
+      os << ") ";
+      printer.printBaseName(typeDecl);
+      os << "::";
+      printer.printIdentifier(pair.first->getNameStr());
+      os << ";\n";
+    }
+    if (isOpaqueLayout) {
+      os << "decltype(";
+      printer.printBaseName(typeDecl);
+      // TODO: allow custom name for this special case
+      os << "::";
+      printer.printIdentifier("unknownDefault");
+      os << ") ";
+      printer.printBaseName(typeDecl);
+      os << "::";
+      printer.printIdentifier("unknownDefault");
+      os << ";\n";
+    }
+  }
+  os << '\n';
 
   const auto *moduleContext = typeDecl->getModuleContext();
   // Print out the "hidden" _impl class.
diff --git a/test/Interop/SwiftToCxx/enums/resilient-enum-in-cxx-execution.cpp b/test/Interop/SwiftToCxx/enums/resilient-enum-in-cxx-execution.cpp
@@ -18,23 +18,38 @@
 #include <iostream>
 #include "enums.h"
 
+using namespace Enums;
+
+void useFooInSwitch(const Foo& f) {
+  switch (f) {
+    case Foo::a:
+      std::cout << "Foo::a\n";
+      break;;
+    case Foo::unknownDefault:
+      std::cout << "Foo::unknownDefault\n";
+      break;
+  }
+}
+
 int main() {
-  using namespace Enums;
   auto f1 = makeFoo(10);
   auto f2 = makeFoo(-10);
 
   printFoo(f1);
   printFoo(f2);
 
-  assert(!f2.inResilientUnknownCase());
-  if (f1.inResilientUnknownCase()) {
+  assert(!f2.isUnknownDefault());
+  if (f1.isUnknownDefault()) {
     std::cout << "f1.inResilientUnknownCase()\n";
     assert(!f1.isA());
   } else {
     assert(f1.isA());
     assert(f1.getA() == 10.0);
   }
 
+  useFooInSwitch(f1);
+  useFooInSwitch(f2);
+
   return 0;
 }
 
@@ -43,3 +58,7 @@ int main() {
 // CHECK-NEXT: a(-10.0)
 
 // NEW_CASE: f1.inResilientUnknownCase()
+
+// NEW_CASE: Foo::unknownDefault
+// OLD_CASE: Foo::a
+// CHECK-NEXT: Foo::a
diff --git a/test/Interop/SwiftToCxx/enums/resilient-enum-in-cxx.swift b/test/Interop/SwiftToCxx/enums/resilient-enum-in-cxx.swift
@@ -42,22 +42,22 @@ public func printFoo(_ x: Foo) {
 // CHECK-EMPTY:
 // CHECK-NEXT:    class Foo final {
 // CHECK-NEXT:    public:
+// CHECK:         enum class cases {
+// CHECK-NEXT:      a,
+// NEW_CASE-NEXT:   b,
+// CHECK-NEXT:      unknownDefault
+// CHECK-NEXT:    }
+// CHECK:         static struct {  // impl struct for case unknownDefault
+// CHECK-NEXT:      constexpr operator cases() const {
+// CHECK-NEXT:        return cases::unknownDefault;
+// CHECK-NEXT:      }
+// CHECK-NEXT:    } unknownDefault;
+// CHECK-NEXT:    inline bool isUnknownDefault() const {
+// CHECK-NEXT:      return *this == Foo::unknownDefault;
+// CHECK-NEXT:    }
 // CHECK:         inline operator cases() const {
 // CHECK-NEXT:      auto tag = _getEnumTag();
 // CHECK-NEXT:      if (tag == _impl::$s5Enums3FooO1ayACSdcACmFWC) return cases::a;
 // NEW_CASE-NEXT:   if (tag == _impl::$s5Enums3FooO1byACSicACmFWC) return cases::b;
-// CHECK-NEXT:      abort();
-// CHECK-NEXT:    }
-// CHECK-NEXT:    inline bool inResilientUnknownCase() const {
-// CHECK-NEXT:      auto tag = _getEnumTag();
-// CHECK-NEXT:      return
-// OLD_CASE-NEXT:     tag != _impl::$s5Enums3FooO1ayACSdcACmFWC;
-// NEW_CASE-NEXT:     tag != _impl::$s5Enums3FooO1ayACSdcACmFWC &&
-// NEW_CASE-NEXT:     tag != _impl::$s5Enums3FooO1byACSicACmFWC;
-// CHECK-NEXT:    }
-// CHECK-NEXT:    inline bool isA() const {
-// CHECK-NEXT:      return _getEnumTag() == _impl::$s5Enums3FooO1ayACSdcACmFWC;
+// CHECK-NEXT:      return cases::unknownDefault;
 // CHECK-NEXT:    }
-// NEW_CASE:      inline bool isB() const {
-// NEW_CASE-NEXT:   return _getEnumTag() == _impl::$s5Enums3FooO1byACSicACmFWC;
-// NEW_CASE-NEXT: }
diff --git a/test/Interop/SwiftToCxx/enums/swift-enum-case-functions.swift b/test/Interop/SwiftToCxx/enums/swift-enum-case-functions.swift
