scope + destructor with Exception parameter for RAII

[BCS]

Sean Kelly wrote:
> Leandro Lucarella wrote:
>> What do you think of adding an optional parameter (exception) to the 
>> destructor, defaulting to null, to indicate the destructor was called 
>> then unwinding because an exception was thrown? Then you can almost 
>> forget about scope(exit/success/failure) and you have a RAII as 
>> complete  as Python's 'with' statement.
> 
> I don't like it, personally.  It doesn't seem a good idea for a dtor to 
> alter its behavior based on whether an exception is in flight, and 
> exceptions should never be thrown from dtors anyway.  Doing so makes 
> writing correct code far too complicated.
> 
> One thing I have done for Ares, however, is to terminate the program if 
> one exception is thrown while another is in flight.  I think DMD/Phobos 
> does not do this currently, and instead either ignores the new 
> exception, or substitutes it for the in-flight exception (I can't 
> remember which).
> 
> 
> Sean


I think this works under DMD

try
{
	throw new Error("some stuff");
}
catch(Error e)
{
	throw new Error("more stuff\n"~e.toString);
}


It could be vary handy to have this ability to swap out one exception 
for another.