Backporting srcLoc to the GHC 7.10 branch

Austin Seipp austin at
Mon Mar 23 17:50:43 UTC 2015

Hi Michael,

I actually tried to adopt this patch into 7.10, because I thought it
was needed for another dependent patch we wanted. Unfortunately, the
backtrace-via-implicit-params patch seems to depend on some prior work
by Simon PJ in the typechecker (-fwarn-redundant-constraints, a rather
large patch), which we *did not* want in 7.10 (the *textual* diff
applied fine, but there were some API changes the backtrace patch
needed, so it failed to build). So, in the end, it was easier to
surgically remove this patch from the one that depended on it, and it
had a much lower 'surface area' of changes, than adopting both. Hope
that makes sense.

Also, as Simon said, we don't normally do big changes like this in
point releases, so I think this is unlikely to happen.

So the short story is "afraid not". But a backport should be possible,
if you're willing to get your hands a bit dirty (any conflict will
likely be fairly easy to fix, but it will involve some textual

On Mon, Mar 23, 2015 at 6:49 AM, Michael Snoyman <michael at> wrote:
> It looks like the srcLoc change[1] is something that some of our (FP
> Complete's) customers would be quite interested in getting access to sooner
> rather than later. Would there be any possibility of getting that patch
> merged into the 7.10 branch of GHC? I'm not sure if I'd try my luck at
> actually including it in 7.10.1, but would it be on the table for 7.10.2?
> We do of course have the option of backporting it ourselves and including it
> in a custom GHC we provide customers, but we generally try to stay as close
> to upstream as possible.
> [1]
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> ghc-devs mailing list
> ghc-devs at


Austin Seipp, Haskell Consultant
Well-Typed LLP,

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