Delaying 7.10?

[Simon Marlow]

I'm worried about the code-size regression.  We should definitely 
measure how bad it is before making a decision on whether to enable 
Typeable by default.

+1 to delaying the release.

Cheers,
Simon

On 29/01/2015 17:58, Simon Peyton Jones wrote:
> Friends
>
> In a call with a bunch of type hackers, we were discussing
>
> https://ghc.haskell.org/trac/ghc/ticket/9858
>
> This is a pretty serious bug.  It allows a malicious person to construct
> his own unsafeCoerce, and so completely subverts Safe Haskell.
>
> Actually there are two bugs (see comment:19).  The first is easily
> fixed.  But the second is not.
>
> We explored various quick fixes, but the real solution is not far out of
> reach.  It amounts to this:
>
> ·Every data type is automatically in Typeable.  No need to say
> “deriving(Typeable)” or “AutoDeriveTypeable” (which would become deprecated)
>
> ·In implementation terms, the constraint solver treats Typeable
> specially, much as it already treats Coercible specially.
>
> It’s not a huge job.  It’d probably take a couple of days of
> implementation work, and some time for shaking out bugs and
> consequential changes.  The biggest thing might be simply working out
> implementation design choices.  (For example, there is a modest
> code-size cost to making everything Typeable, esp because that includes
> the data constructors of the type (which can be used in types, with
> DataKinds).  Does that matter?  Should we provide a way to suppress it?
> If so, we’d also need a way to express whether or not the Typable
> instance exists in the interface file.)
>
> But it is a substantial change that will touch a lot of lines of code.
> Moreover, someone has to do it, and Iavor (who heroically volunteered)
> happens to be travelling next week.
>
> So it’s really not the kind of thing we would usually do after RC2.
>
> But (a) it’s serious and, as it happens, (b) there is also the BBP
> Prelude debate going on.
>
> Hence the question: should we simply delay 7.10  by, say, a month?
> After all, the timetable is up to us.  Doing so might give a bit more
> breathing space to the BBP debate, which might allow time for reflection
> and/or implementation of modest features to help the transition.  (I
> know that several are under discussion.)  Plus, anyone waiting for 7.10
> can simply use RC2, which is pretty good.
>
> Would that be a relief to the BBP debate?  Or any other opinions.
>
> Simon
>
> PS: I know, I know: there is endless pressure to delay releases to get
> stuff in.  If we give in to that pressure, we never make a release.  But
> we should know when to break our own rules.  Perhaps this is such an
> occasion.
>
>
>
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