[debug] Don't notify listener of exceptions internal to a desugaring.

src/objects.h

 // Copyright 2015 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_OBJECTS_H_
 #define V8_OBJECTS_H_
 
 #include <iosfwd>
 #include <memory>
 
@@ skipping 4448 matching lines @@
 //      [ range-start , range-end , handler-offset , handler-data ]
 // 2) Based on return addresses: Used for turbofanned code. Contains one entry
 //    per call-site that could throw an exception. Layout looks as follows:
 //      [ return-address-offset , handler-offset ]
 class HandlerTable : public FixedArray {
  public:
   // Conservative prediction whether a given handler will locally catch an
   // exception or cause a re-throw to outside the code boundary. Since this is
   // undecidable it is merely an approximation (e.g. useful for debugger).
   enum CatchPrediction {
-    UNCAUGHT,  // the handler will (likely) rethrow the exception.
-    CAUGHT,    // the exception will be caught by the handler.
-    PROMISE    // the exception will be caught and cause a promise rejection.
+    UNCAUGHT,    // The handler will (likely) rethrow the exception.
+    CAUGHT,      // The exception will be caught by the handler.
+    PROMISE,     // The exception will be caught and cause a promise rejection.
+    DESUGARING,  // The exception will be caught, but both the exception and the
+                 // catching are part of a desugaring and should therefore not
+                 // be visible to the user (we won't notify the debugger of such
+                 // exceptions).
   };
 
   // Getters for handler table based on ranges.
   inline int GetRangeStart(int index) const;
   inline int GetRangeEnd(int index) const;
   inline int GetRangeHandler(int index) const;
   inline int GetRangeData(int index) const;
 
   // Setters for handler table based on ranges.
   inline void SetRangeStart(int index, int value);
@@ skipping 6581 matching lines @@
     }
     return value;
   }
 };
 
 
 }  // NOLINT, false-positive due to second-order macros.
 }  // NOLINT, false-positive due to second-order macros.
 
 #endif  // V8_OBJECTS_H_