@nogc exceptions?

[Manu]

What's the story with @nogc exceptions?
There was DIP1008 or whatever, I didn't follow it because I never use
exceptions... but I kinda need it.

IIRC, the idea was the throw statement transfer ownership of the
exception to the runtime, and then use a `scope` catch block, such
that the runtime can be sure it owns the only reference at the end of
the catch block and it can free the exception rather than transfer it
to the GC?

How did it fail?