message: Adding UNREACHABLE() macro
diff: @@ -104,6 +104,11 @@ void Error(SourcePos p, const char *format, ...) PRINTF_FUNC;
  */
  void PerformanceWarning(SourcePos p, const char *format, ...) PRINTF_FUNC;
  +/** Reports that unreachable location is reached. This is a kind of fatal error
  + that causes the program to terminate.
  + */
  +#define UNREACHABLE() FatalError(__FILE__, __LINE__, "unreachable code")
  +
  /** Reports a fatal error that causes the program to terminate. This
  should only be used for cases where there is an internal error in the
  compiler.
  