David Thanks for moving my early-inline patch series to HEAD. You'll remember that I pushed this patch (below) to spj-early-inline2 Can you be sure to cherry-pick this one too? It's important and I don't see it in HEAD yet. I'm surprised that there isn't a validate failure (T9505 if memory serves - see attached). Simon commit 002192aa8df463ae945e8a94147cfc1d848f43a5 Author: Simon Peyton Jones <simonpj@microsoft.com> Date: Fri Feb 24 16:55:36 2017 +0000 Fix a nasty bug in CoreSubst.collectBindersPushingCo The bug wsa in the use of (mkNthCo 0) to get the argument part of a function coercion. Not so! Now (->) takes four arguments so that 0 should have been 2. Enough with magic numbers. I defined decomposeFunCo, and used it throughout. Much nicer now; and correct. The nete effect, incidentally, was that T9509 was failing to specialise. (And that was the initial reason for introducing collectBindersPushingCo in the first place.)