[AST] Wrap converted clang::FunctionType values in clang::PointerType.

Author: varungandhi-apple

include/swift/AST/Types.h

@@ -2925,8 +2925,11 @@ class AnyFunctionType : public TypeBase {
       friend ExtInfo;
       friend class AnyFunctionType;
       friend class FunctionType;
-      // We preserve a full clang::Type *, not a clang::FunctionType *, so
-      // we can keep sugar in case we need to present an error to the user.
+      // We preserve a full clang::Type *, not a clang::FunctionType * as:
+      // 1. We need to keep sugar in case we need to present an error to the user.
+      // 2. The actual type being stored is [ignoring sugar] either a
+      //    clang::PointerType or a clang::BlockPointerType which points to a
+      //    clang::FunctionType.
       const clang::Type *ClangFunctionType;
 
       bool empty() const { return !ClangFunctionType; }

lib/AST/ClangTypeConverter.cpp

@@ -137,9 +137,9 @@ const clang::Type *ClangTypeConverter::getFunctionType(
 
   switch (repr) {
   case AnyFunctionType::Representation::CFunctionPointer:
-    return fn.getTypePtr();
+    return ClangASTContext.getPointerType(fn).getTypePtr();
   case AnyFunctionType::Representation::Block:
-    return ClangASTContext.getBlockPointerType(fn).getTypePtrOrNull();
+    return ClangASTContext.getBlockPointerType(fn).getTypePtr();
   case AnyFunctionType::Representation::Swift:
   case AnyFunctionType::Representation::Thin:
     llvm_unreachable("Expected a C-compatible representation.");

lib/AST/Type.cpp

@@ -3235,10 +3235,13 @@ Type ProtocolCompositionType::get(const ASTContext &C,
 void
 AnyFunctionType::ExtInfo::assertIsFunctionType(const clang::Type *type) {
 #ifndef NDEBUG
-  if (!type->isFunctionType()) {
-    llvm::errs() << "Expected a Clang function type but found\n";
-    type->dump(llvm::errs());
-    llvm_unreachable("");
+  if (!(type->isFunctionPointerType() || type->isBlockPointerType())) {
+    SmallString<256> buf;
+    llvm::raw_svector_ostream os(buf);
+    os << "Expected a Clang function type wrapped in a pointer type or "
+       << "a block pointer type but found:\n";
+    type->dump(os);
+    llvm_unreachable(os.str().data());
   }
 #endif
   return;
@@ -3250,7 +3253,7 @@ const clang::Type *AnyFunctionType::getClangFunctionType() const {
     return cast<FunctionType>(this)->getClangFunctionType();
   case TypeKind::GenericFunction:
     // Generic functions do not have C types.
-  return nullptr;
+    return nullptr;
   default:
     llvm_unreachable("Illegal type kind for AnyFunctionType.");
   }

lib/ClangImporter/ImportType.cpp

@@ -421,7 +421,7 @@ namespace {
             funcTy->getExtInfo()
               .withRepresentation(
                 AnyFunctionType::Representation::CFunctionPointer)
-              .withClangFunctionType(pointeeQualType.getTypePtr())),
+              .withClangFunctionType(type)),
           ImportHint::CFunctionPointer
         };
       }