[Frontend] - Mark some ASTUnit methods as const

[hamzasood]

Summary

While using the libtooling API, I ran into problems when using a const ASTUnit. There were a few functions I needed to use that don't seem to modify anything, but they weren't marked as const so I couldn't use them.

This patch marks those methods (and a few others) as const.

[vsk]

LGTM.

[hamzasood]

Could someone commit this for me? I don't have access.

cfe/trunk/include/clang/Frontend/ASTUnit.h

public:
   
   const FileManager &getFileManager() const { return *FileMgr; }
         FileManager &getFileManager()       { return *FileMgr; }
 
   const FileSystemOptions &getFileSystemOpts() const { return FileSystemOpts; }
 
   IntrusiveRefCntPtr<ASTReader> getASTReader() const;
 
-  StringRef getOriginalSourceFileName() {
+  StringRef getOriginalSourceFileName() const {
     return OriginalSourceFile;
   }
 
   ASTMutationListener *getASTMutationListener();
   ASTDeserializationListener *getDeserializationListener();
 
   bool getOnlyLocalDecls() const { return OnlyLocalDecls; }
 
SourceLocation getLocation(const FileEntry *File,
                              unsigned Line, unsigned Col) const;
 
   /// \brief Get the source location for the given file:offset pair.
   SourceLocation getLocation(const FileEntry *File, unsigned Offset) const;
 
   /// \brief If \p Loc is a loaded location from the preamble, returns
   /// the corresponding local location of the main file, otherwise it returns
   /// \p Loc.
-  SourceLocation mapLocationFromPreamble(SourceLocation Loc);
+  SourceLocation mapLocationFromPreamble(SourceLocation Loc) const;
 
   /// \brief If \p Loc is a local location of the main file but inside the
   /// preamble chunk, returns the corresponding loaded location from the
   /// preamble, otherwise it returns \p Loc.
-  SourceLocation mapLocationToPreamble(SourceLocation Loc);
+  SourceLocation mapLocationToPreamble(SourceLocation Loc) const;
 
-  bool isInPreambleFileID(SourceLocation Loc);
-  bool isInMainFileID(SourceLocation Loc);
-  SourceLocation getStartOfMainFileID();
-  SourceLocation getEndOfPreambleFileID();
+  bool isInPreambleFileID(SourceLocation Loc) const;
+  bool isInMainFileID(SourceLocation Loc) const;
+  SourceLocation getStartOfMainFileID() const;
+  SourceLocation getEndOfPreambleFileID() const;
 
   /// \see mapLocationFromPreamble.
-  SourceRange mapRangeFromPreamble(SourceRange R) {
+  SourceRange mapRangeFromPreamble(SourceRange R) const {
     return SourceRange(mapLocationFromPreamble(R.getBegin()),
                        mapLocationFromPreamble(R.getEnd()));
   }
 
   /// \see mapLocationToPreamble.
-  SourceRange mapRangeToPreamble(SourceRange R) {
+  SourceRange mapRangeToPreamble(SourceRange R) const {
     return SourceRange(mapLocationToPreamble(R.getBegin()),
                        mapLocationToPreamble(R.getEnd()));
   }
   
   // Retrieve the diagnostics associated with this AST
   typedef StoredDiagnostic *stored_diag_iterator;
   typedef const StoredDiagnostic *stored_diag_const_iterator;
   stored_diag_const_iterator stored_diag_begin() const { 
public:
   /// \returns true if the iteration was complete or false if it was aborted.
   bool visitLocalTopLevelDecls(void *context, DeclVisitorFn Fn);
 
   /// \brief Get the PCH file if one was included.
   const FileEntry *getPCHFile();
 
   /// \brief Returns true if the ASTUnit was constructed from a serialized
   /// module file.
-  bool isModuleFile();
+  bool isModuleFile() const;
 
   std::unique_ptr<llvm::MemoryBuffer>
   getBufferForFile(StringRef Filename, std::string *ErrorStr = nullptr);
 
   /// \brief Determine what kind of translation unit this AST represents.
   TranslationUnitKind getTranslationUnitKind() const { return TUKind; }
 
   /// \brief Determine the input kind this AST unit represents.

cfe/trunk/lib/Frontend/ASTUnit.cpp

SourceLocation ASTUnit::getLocation(const FileEntry *File,
   const SourceManager &SM = getSourceManager();
   SourceLocation FileLoc = SM.translateFileLineCol(File, 1, 1);
   return SM.getMacroArgExpandedLocation(FileLoc.getLocWithOffset(Offset));
 }
 
 /// \brief If \arg Loc is a loaded location from the preamble, returns
 /// the corresponding local location of the main file, otherwise it returns
 /// \arg Loc.
-SourceLocation ASTUnit::mapLocationFromPreamble(SourceLocation Loc) {
+SourceLocation ASTUnit::mapLocationFromPreamble(SourceLocation Loc) const {
   FileID PreambleID;
   if (SourceMgr)
     PreambleID = SourceMgr->getPreambleFileID();
 
   if (Loc.isInvalid() || !Preamble || PreambleID.isInvalid())
     return Loc;
 
   unsigned Offs;
   if (SourceMgr->isInFileID(Loc, PreambleID, &Offs) && Offs < Preamble->getBounds().Size) {
     SourceLocation FileLoc
         = SourceMgr->getLocForStartOfFile(SourceMgr->getMainFileID());
     return FileLoc.getLocWithOffset(Offs);
   }
 
   return Loc;
 }
 
 /// \brief If \arg Loc is a local location of the main file but inside the
 /// preamble chunk, returns the corresponding loaded location from the
 /// preamble, otherwise it returns \arg Loc.
-SourceLocation ASTUnit::mapLocationToPreamble(SourceLocation Loc) {
+SourceLocation ASTUnit::mapLocationToPreamble(SourceLocation Loc) const {
   FileID PreambleID;
   if (SourceMgr)
     PreambleID = SourceMgr->getPreambleFileID();
 
   if (Loc.isInvalid() || !Preamble || PreambleID.isInvalid())
     return Loc;
 
   unsigned Offs;
   if (SourceMgr->isInFileID(Loc, SourceMgr->getMainFileID(), &Offs) &&
       Offs < Preamble->getBounds().Size) {
     SourceLocation FileLoc = SourceMgr->getLocForStartOfFile(PreambleID);
     return FileLoc.getLocWithOffset(Offs);
   }
 
   return Loc;
 }
 
-bool ASTUnit::isInPreambleFileID(SourceLocation Loc) {
+bool ASTUnit::isInPreambleFileID(SourceLocation Loc) const {
   FileID FID;
   if (SourceMgr)
     FID = SourceMgr->getPreambleFileID();
   
   if (Loc.isInvalid() || FID.isInvalid())
     return false;
   
   return SourceMgr->isInFileID(Loc, FID);
 }
 
-bool ASTUnit::isInMainFileID(SourceLocation Loc) {
+bool ASTUnit::isInMainFileID(SourceLocation Loc) const {
   FileID FID;
   if (SourceMgr)
     FID = SourceMgr->getMainFileID();
   
   if (Loc.isInvalid() || FID.isInvalid())
     return false;
   
   return SourceMgr->isInFileID(Loc, FID);
 }
 
-SourceLocation ASTUnit::getEndOfPreambleFileID() {
+SourceLocation ASTUnit::getEndOfPreambleFileID() const {
   FileID FID;
   if (SourceMgr)
     FID = SourceMgr->getPreambleFileID();
   
   if (FID.isInvalid())
     return SourceLocation();
 
   return SourceMgr->getLocForEndOfFile(FID);
 }
 
-SourceLocation ASTUnit::getStartOfMainFileID() {
+SourceLocation ASTUnit::getStartOfMainFileID() const {
   FileID FID;
   if (SourceMgr)
     FID = SourceMgr->getMainFileID();
   
   if (FID.isInvalid())
     return SourceLocation();
   
   return SourceMgr->getLocForStartOfFile(FID);
Reader->getModuleManager().visit([&Mod](serialization::ModuleFile &M) {
     return true;
   });
   if (Mod)
     return Mod->File;
 
   return nullptr;
 }
 
-bool ASTUnit::isModuleFile() {
+bool ASTUnit::isModuleFile() const {
   return isMainFileAST() && getLangOpts().isCompilingModule();
 }
 
 InputKind ASTUnit::getInputKind() const {
   auto &LangOpts = getLangOpts();
 
   InputKind::Language Lang;
   if (LangOpts.OpenCL)