[clang-doc] Fix typedef/using output.

Provides an initializer for the TypedefInfo.IsUsing member. Previously
this member was uninitialized and would produce random output.

Adds the Description (code comments) to the bitcode reader/writer.
Previously the typedef/using descriptions were lost during the bitcode
round-trip. Adds a test for this.

Differential Revision: https://reviews.llvm.org/D136638

clang-tools-extra/clang-doc/BitcodeReader.cpp

@@ -368,28 +368,27 @@ template <typename T> llvm::Expected<CommentInfo *> getCommentInfo(T I) {
 }
 
 template <> llvm::Expected<CommentInfo *> getCommentInfo(FunctionInfo *I) {
-  I->Description.emplace_back();
-  return &I->Description.back();
+  return &I->Description.emplace_back();
 }
 
 template <> llvm::Expected<CommentInfo *> getCommentInfo(NamespaceInfo *I) {
-  I->Description.emplace_back();
-  return &I->Description.back();
+  return &I->Description.emplace_back();
 }
 
 template <> llvm::Expected<CommentInfo *> getCommentInfo(RecordInfo *I) {
-  I->Description.emplace_back();
-  return &I->Description.back();
+  return &I->Description.emplace_back();
 }
 
 template <> llvm::Expected<CommentInfo *> getCommentInfo(MemberTypeInfo *I) {
-  I->Description.emplace_back();
-  return &I->Description.back();
+  return &I->Description.emplace_back();
 }
 
 template <> llvm::Expected<CommentInfo *> getCommentInfo(EnumInfo *I) {
-  I->Description.emplace_back();
-  return &I->Description.back();
+  return &I->Description.emplace_back();
+}
+
+template <> llvm::Expected<CommentInfo *> getCommentInfo(TypedefInfo *I) {
+  return &I->Description.emplace_back();
 }
 
 template <> llvm::Expected<CommentInfo *> getCommentInfo(CommentInfo *I) {

clang-tools-extra/clang-doc/BitcodeWriter.cpp

@@ -432,6 +432,8 @@ void ClangDocBitcodeWriter::emitBlock(const TypedefInfo &T) {
   emitRecord(T.Name, TYPEDEF_NAME);
   for (const auto &N : T.Namespace)
     emitBlock(N, FieldId::F_namespace);
+  for (const auto &CI : T.Description)
+    emitBlock(CI);
   if (T.DefLoc)
     emitRecord(*T.DefLoc, TYPEDEF_DEFLOCATION);
   emitRecord(T.IsUsing, TYPEDEF_IS_USING);

clang-tools-extra/clang-doc/Representation.h

@@ -365,7 +365,7 @@ struct TypedefInfo : public SymbolInfo {
   //   using MyVector = std::vector<int>
   // False means it's a C-style typedef:
   //   typedef std::vector<int> MyVector;
-  bool IsUsing;
+  bool IsUsing = false;
 };
 
 struct BaseRecordInfo : public RecordInfo {

clang-tools-extra/unittests/clang-doc/BitcodeTest.cpp

@@ -183,11 +183,33 @@ TEST(BitcodeTest, emitTypedefInfoBitcode) {
   I.Underlying = TypeInfo("unsigned");
   I.IsUsing = true;
 
+  CommentInfo Top;
+  Top.Kind = "FullComment";
+
+  Top.Children.emplace_back(std::make_unique<CommentInfo>());
+  CommentInfo *BlankLine = Top.Children.back().get();
+  BlankLine->Kind = "ParagraphComment";
+  BlankLine->Children.emplace_back(std::make_unique<CommentInfo>());
+  BlankLine->Children.back()->Kind = "TextComment";
+
+  I.Description.emplace_back(std::move(Top));
+
   std::string WriteResult = writeInfo(&I);
   EXPECT_TRUE(WriteResult.size() > 0);
   std::vector<std::unique_ptr<Info>> ReadResults = readInfo(WriteResult, 1);
 
   CheckTypedefInfo(&I, InfoAsTypedef(ReadResults[0].get()));
+
+  // Check one with no IsUsing set, no description, and no definition location.
+  TypedefInfo I2;
+  I2.Name = "SomethingElse";
+  I2.IsUsing = false;
+  I2.Underlying = TypeInfo("int");
+
+  WriteResult = writeInfo(&I2);
+  EXPECT_TRUE(WriteResult.size() > 0);
+  ReadResults = readInfo(WriteResult, 1);
+  CheckTypedefInfo(&I2, InfoAsTypedef(ReadResults[0].get()));
 }
 
 TEST(SerializeTest, emitInfoWithCommentBitcode) {