Axe initIfaceTc, tie the knot through HPT (or if_rec_types).
Summary: initIfaceTc was originally used to make sure when we typecheck an interface, it can find the TyThings for things it itself defined. However, in the case of retypecheckLoop, this wasn't necessary because we ALREADY tied the knot through the HPT. This commit removes initIfaceTc, instead relying on the HPT to tie the knot. genModDetails' caller needed to be modified to tie the knot, but there are not that many call-sites of typecheckIface so the change is quite reasonable. We also introduce a new 'initIfaceLoad', which does NOT set up 'if_rec_types'. It's used when we're typechecking old, up-to-date interfaces in, since we're never going to update the type environment. The full details are in Note [Knot-tying typecheckIface]. Displeasingly, we need a special case to handle DFuns in the case of tcHiBootIface, see Note [DFun knot-tying special case] for the gory details. I also added another test which tickles a bug in a buggy version of this patch (see "Why the seq?") Signed-off-by: Edward Z. Yang <firstname.lastname@example.org> Test Plan: validate Reviewers: simonpj, austin, bgamari Subscribers: thomie Differential Revision: https://phabricator.haskell.org/D2349