GHC 7.10.2 panic

[thumphries]

GHC 7.10.2 has been unhelpfully exploding on some very large templates. I have not yet observed this happening with 8.0.2, and believe it to be a GHC bug fixed upstream.

I've partially addressed this by improving the simplifier, but this is not a sufficient fix. Users may need to work around this as it arises by breaking huge templates down into smaller ones. Not good!

I think the long-term fix is to just upgrade to 8.0. We might be able to put it off a bit longer by hoisting common subexpressions or breaking large terms into smaller ones automatically. We could also fix it structurally by generating bytecode or C instead of Haskell, but that would be more work than just upgrading.