Make ModuleDependencyCollector's method virtual (NFC)

[JDevlieghere]

Summary

For reproducers in LLDB we want to hook up into the existing clang infrastructure. To make that happen we need to be able to override the ModuleDependencyCollector's methods.

[bruno]

How much of the ModuleDependencyCollector will be reused as is by LLDB? I wonder about the tradeoff versus inheriting from DependencyCollector directly.

[JDevlieghere]

In D58072#1393640, @bruno wrote:

How much of the ModuleDependencyCollector will be reused as is by LLDB? I wonder about the tradeoff versus inheriting from DependencyCollector directly.

We reuse the attachTo methods, which in turn use the ModuleDependencyListener, ModuleDependencyPPCallbacks and ModuleDependencyMMCallbacks. Do you think it's worth re-implementing those?

[bruno]

Not really. Would making only the attachTo* methods virtual enough though?

[JDevlieghere]

In D58072#1393817, @bruno wrote:

Not really. Would making only the attachTo* methods virtual enough though?

You mean making them not virtual? They're the only ones I don't override.

[bruno]

I missed that the DependencyCollector already marks them virtual, you are just making it obvious here. I think you can omit the ones that are already virtual and only add to the ones that are on the intend of this patch.

[JDevlieghere]

Alright, I'll split this up in two patches

[bruno]

LGTM!

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

class ModuleDependencyCollector : public DependencyCollector {
   std::error_code copyToRoot(StringRef Src, StringRef Dst = {});
 
 public:
   ModuleDependencyCollector(std::string DestDir)
       : DestDir(std::move(DestDir)) {}
   ~ModuleDependencyCollector() override { writeFileMap(); }
 
   StringRef getDest() { return DestDir; }
-  bool insertSeen(StringRef Filename) { return Seen.insert(Filename).second; }
-  void addFile(StringRef Filename, StringRef FileDst = {});
+  virtual bool insertSeen(StringRef Filename) { return Seen.insert(Filename).second; }
+  virtual void addFile(StringRef Filename, StringRef FileDst = {});
 
-  void addFileMapping(StringRef VPath, StringRef RPath) {
+  virtual void addFileMapping(StringRef VPath, StringRef RPath) {
     VFSWriter.addFileMapping(VPath, RPath);
   }
 
   void attachToPreprocessor(Preprocessor &PP) override;
   void attachToASTReader(ASTReader &R) override;
 
-  void writeFileMap();
-  bool hasErrors() { return HasErrors; }
+  virtual void writeFileMap();
+  virtual bool hasErrors() { return HasErrors; }
 };
 
 /// AttachDependencyGraphGen - Create a dependency graph generator, and attach
 /// it to the given preprocessor.
 void AttachDependencyGraphGen(Preprocessor &PP, StringRef OutputFile,
                               StringRef SysRoot);
 
 /// AttachHeaderIncludeGen - Create a header include list generator, and attach