[cxx-interop][rebranch] Handle clang elaborated types properly

Clang recently started wrapping more types in `clang::ElaboratedType` after this change: https://reviews.llvm.org/D112374

This broke some assumptions in ClangImporter, specifically in enum handling logic. This change adjusts those.

Fixes these tests in rebranch:
* `Interop/Cxx/enum/anonymous-with-swift-name-module-interface.swift`
* `Interop/Cxx/enum/anonymous-with-swift-name-objc-module-interface.swift`
* `Interop/Cxx/enum/anonymous-with-swift-name.swift`
* `Interop/Cxx/enum/c-enums-NS_OPTIONS-NS_REFINED_FOR_SWIFT.swift`
* `Interop/Cxx/enum/c-enums-NS_OPTIONS.swift`
* `Interop/Cxx/enum/c-enums-withOptions-omit.swift`

Author: egorzhdan

lib/ClangImporter/ImportDecl.cpp

@@ -5659,6 +5659,8 @@ SwiftDeclConverter::getImplicitProperty(ImportedName importedName,
       getAccessorPropertyType(getter, false, getterName.getSelfIndex());
   if (propertyType.isNull())
     return nullptr;
+  if (auto elaborated = dyn_cast<clang::ElaboratedType>(propertyType))
+    propertyType = elaborated->desugar();
 
   // If there is a setter, check that the property it implies
   // matches that of the getter.
@@ -7133,6 +7135,8 @@ canSkipOverTypedef(ClangImporter::Implementation &Impl,
     return nullptr;
 
   clang::QualType UnderlyingType = ClangTypedef->getUnderlyingType();
+  if (auto elaborated = dyn_cast<clang::ElaboratedType>(UnderlyingType))
+    UnderlyingType = elaborated->desugar();
 
   // A typedef to a typedef should get imported as a typealias.
   auto *TypedefT = UnderlyingType->getAs<clang::TypedefType>();
@@ -8456,6 +8460,8 @@ void ClangImporter::Implementation::loadAllMembersOfRecordDecl(
       clang::QualType baseType = base.getType();
       if (auto spectType = dyn_cast<clang::TemplateSpecializationType>(baseType))
         baseType = spectType->desugar();
+      if (auto elaborated = dyn_cast<clang::ElaboratedType>(baseType))
+        baseType = elaborated->desugar();
       if (!isa<clang::RecordType>(baseType))
         continue;
 

lib/ClangImporter/ImportEnumInfo.cpp

@@ -70,11 +70,12 @@ void EnumInfo::classifyEnum(const clang::EnumDecl *decl,
   // name for the Swift type.
   if (!decl->hasNameForLinkage()) {
     // If this enum comes from a typedef, we can find a name.
-    if (!isa<clang::TypedefType>(decl->getIntegerType().getTypePtr()) ||
+    const clang::Type *underlyingType = getUnderlyingType(decl);
+    if (!isa<clang::TypedefType>(underlyingType) ||
         // If the typedef is available in Swift, the user will get ambiguity.
         // It also means they may not have intended this API to be imported like this.
         !importer::isUnavailableInSwift(
-            cast<clang::TypedefType>(decl->getIntegerType().getTypePtr())->getDecl(),
+            cast<clang::TypedefType>(underlyingType)->getDecl(),
             nullptr, true)) {
       kind = EnumKind::Constants;
       return;
@@ -241,6 +242,13 @@ StringRef importer::getCommonPluralPrefix(StringRef singular,
   return commonPrefix;
 }
 
+const clang::Type *importer::getUnderlyingType(const clang::EnumDecl *decl) {
+  const clang::Type *underlyingType = decl->getIntegerType().getTypePtr();
+  if (auto elaborated = dyn_cast<clang::ElaboratedType>(underlyingType))
+    underlyingType = elaborated->desugar().getTypePtr();
+  return underlyingType;
+}
+
 /// Determine the prefix to be stripped from the names of the enum constants
 /// within the given enum.
 void EnumInfo::determineConstantNamePrefix(const clang::EnumDecl *decl) {
@@ -350,8 +358,8 @@ void EnumInfo::determineConstantNamePrefix(const clang::EnumDecl *decl) {
     StringRef enumNameStr;
     // If there's no name, this must be typedef. So use the typedef's name.
     if (!decl->hasNameForLinkage()) {
-      auto typedefDecl = cast<clang::TypedefType>(
-                             decl->getIntegerType().getTypePtr())->getDecl();
+      const clang::Type *underlyingType = getUnderlyingType(decl);
+      auto typedefDecl = cast<clang::TypedefType>(underlyingType)->getDecl();
       enumNameStr = typedefDecl->getName();
     } else {
       enumNameStr = decl->getName();

lib/ClangImporter/ImportEnumInfo.h

@@ -159,6 +159,10 @@ StringRef getCommonWordPrefix(StringRef a, StringRef b,
 ///
 /// \see getCommonWordPrefix
 StringRef getCommonPluralPrefix(StringRef singular, StringRef plural);
+
+/// Returns the underlying integer type of an enum. If clang treats the type as
+/// an elaborated type, an unwrapped type is returned.
+const clang::Type *getUnderlyingType(const clang::EnumDecl *decl);
 }
 }
 

lib/ClangImporter/ImportName.cpp

@@ -645,7 +645,7 @@ findSwiftNameAttr(const clang::Decl *decl, ImportNameVersion version) {
 
     if (auto enumDecl = dyn_cast<clang::EnumDecl>(decl)) {
       // Intentionally don't get the canonical type here.
-      if (auto typedefType = dyn_cast<clang::TypedefType>(enumDecl->getIntegerType().getTypePtr())) {
+      if (auto typedefType = dyn_cast<clang::TypedefType>(getUnderlyingType(enumDecl))) {
         // If the typedef is available in Swift, the user will get ambiguity.
         // It also means they may not have intended this API to be imported like this.
         if (importer::isUnavailableInSwift(typedefType->getDecl(), nullptr, true)) {
@@ -1796,7 +1796,7 @@ ImportedName NameImporter::importNameImpl(const clang::NamedDecl *D,
     // typedef (even if it's an anonymous enum).
     if (auto enumDecl = dyn_cast<clang::EnumDecl>(D)) {
       // Intentionally don't get the canonical type here.
-      if (auto typedefType = dyn_cast<clang::TypedefType>(enumDecl->getIntegerType().getTypePtr())) {
+      if (auto typedefType = dyn_cast<clang::TypedefType>(getUnderlyingType(enumDecl))) {
         // If the typedef is available in Swift, the user will get ambiguity.
         // It also means they may not have intended this API to be imported like this.
         if (importer::isUnavailableInSwift(typedefType->getDecl(), nullptr, true)) {

lib/ClangImporter/ImportType.cpp

@@ -2086,18 +2086,22 @@ ImportedType ClangImporter::Implementation::importFunctionReturnType(
     OptionalityOfReturn = OTK_ImplicitlyUnwrappedOptional;
   }
 
+  clang::QualType returnType = clangDecl->getReturnType();
+  if (auto elaborated =
+          dyn_cast<clang::ElaboratedType>(returnType.getTypePtr()))
+    returnType = elaborated->desugar();
+
   // Specialized templates need to match the args/result exactly (i.e.,
   // ptr -> ptr not ptr -> Optional<ptr>).
-  if (clangDecl->getReturnType()->isPointerType() &&
-      clangDecl->getPrimaryTemplate() &&
+  if (returnType->isPointerType() && clangDecl->getPrimaryTemplate() &&
       clangDecl
           ->getPrimaryTemplate()
           ->getAsFunction()
           ->getReturnType()
           ->isTemplateTypeParmType())
     OptionalityOfReturn = OTK_None;
 
-  if (auto typedefType = dyn_cast<clang::TypedefType>(clangDecl->getReturnType().getTypePtr())) {
+  if (auto typedefType = dyn_cast<clang::TypedefType>(returnType)) {
     if (isUnavailableInSwift(typedefType->getDecl())) {
       if (auto clangEnum = findAnonymousEnumForTypedef(SwiftContext, typedefType)) {
         // If this fails, it means that we need a stronger predicate for
@@ -2112,7 +2116,7 @@ ImportedType ClangImporter::Implementation::importFunctionReturnType(
   }
 
   // Import the result type.
-  return importType(clangDecl->getReturnType(),
+  return importType(returnType,
                     (isAuditedResult ? ImportTypeKind::AuditedResult
                                      : ImportTypeKind::Result),
                     ImportDiagnosticAdder(*this, clangDecl,
@@ -2244,6 +2248,8 @@ ClangImporter::Implementation::importParameterType(
     ArrayRef<GenericTypeParamDecl *> genericParams,
     llvm::function_ref<void(Diagnostic &&)> addImportDiagnosticFn) {
   auto paramTy = param->getType();
+  if (auto elaborated = dyn_cast<clang::ElaboratedType>(paramTy))
+    paramTy = elaborated->desugar();
 
   ImportTypeKind importKind = getImportTypeKindForParam(param);