GC plugin: improve error reporting when tracing illegal fields.

tools/clang/blink_gc_plugin/RecordInfo.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // This file provides a wrapper for CXXRecordDecl that accumulates GC related
 // information about a class. Accumulated information is memoized and the info
 // objects are stored in a RecordCache.
 
 #ifndef TOOLS_BLINK_GC_PLUGIN_RECORD_INFO_H_
 #define TOOLS_BLINK_GC_PLUGIN_RECORD_INFO_H_
 
 #include <map>
 #include <vector>
 
 #include "Edge.h"
 
 #include "clang/AST/AST.h"
 #include "clang/AST/CXXInheritance.h"
+#include "clang/Frontend/CompilerInstance.h"
 
 class RecordCache;
 
 // A potentially tracable and/or lifetime affecting point in the object graph.
 class GraphPoint {
  public:
   GraphPoint() : traced_(false) {}
   virtual ~GraphPoint() {}
   void MarkTraced() { traced_ = true; }
   bool IsProperlyTraced() { return traced_ || !NeedsTracing().IsNeeded(); }
+  bool IsInproperlyTraced() { return traced_ && NeedsTracing().IsIllegal(); }
   virtual const TracingStatus NeedsTracing() = 0;
 
  private:
   bool traced_;
 };
 
 class BasePoint : public GraphPoint {
  public:
   BasePoint(const clang::CXXBaseSpecifier& spec,
             RecordInfo* info,
@@ skipping 112 matching lines @@
 
   bool is_gc_derived_;
 
   std::vector<std::string> gc_base_names_;
 
   friend class RecordCache;
 };
 
 class RecordCache {
  public:
+  RecordCache(clang::CompilerInstance& instance)
+    : instance_(instance)
+  {
+  }
+
   RecordInfo* Lookup(clang::CXXRecordDecl* record);
 
   RecordInfo* Lookup(const clang::CXXRecordDecl* record) {
     return Lookup(const_cast<clang::CXXRecordDecl*>(record));
   }
 
   RecordInfo* Lookup(clang::DeclContext* decl) {
     return Lookup(clang::dyn_cast<clang::CXXRecordDecl>(decl));
   }
 
@@ skipping 10 matching lines @@
       if (!it->second.fields_)
         continue;
       for (RecordInfo::Fields::iterator fit = it->second.fields_->begin();
         fit != it->second.fields_->end();
         ++fit) {
         fit->second.deleteEdge();
       }
     }
   }
 
+  clang::CompilerInstance& instance() const { return instance_; }
+
  private:
+  clang::CompilerInstance& instance_;
+
   typedef std::map<clang::CXXRecordDecl*, RecordInfo> Cache;
   Cache cache_;
 };
 
 #endif  // TOOLS_BLINK_GC_PLUGIN_RECORD_INFO_H_