More refactoring of FamInst/FamInstEnv; finally fixes Trac #7524

Quite a bit of tidying up here; the fix to #7524 is actually
only a small part.

* Be fully clear that the cab_tvs in a CoAxBranch are not
  fresh.  See Note [CoAxBranch type variables] in CoAxiom.

* Use CoAxBranch to replace the ATDfeault type in Class.
  CoAxBranch is perfect here.  This change allowed me to
  delete quite a bit of boilerplate code, including the
  corresponding IfaceSynType.

* Tidy up the construction of CoAxBranches, and when FamIntBranch is
  freshened.  The latter onw happens only in FamInst.newFamInst.

* Tidy the tyvars of a CoAxBranch when we build them, done in
  FamInst.mkCoAxBranch.  See Note [Tidy axioms when we build them]
  in that module.  This is what fixes #7524.

Much niceer now.

1 files changed, 0 insertions, 7 deletions

diff --git a/compiler/iface/BinIface.hs b/compiler/iface/BinIface.hs
index ac244fab79..7f9b24e6e4 100644
--- a/compiler/iface/BinIface.hs
+++ b/compiler/iface/BinIface.hs
@@ -1426,13 +1426,6 @@ instance Binary IfaceAT where
         defs <- get bh
         return (IfaceAT dec defs)
 
-instance Binary IfaceATDefault where
-    put_ bh (IfaceATD tvs pat_tys ty) = do
-        put_ bh tvs
-        put_ bh pat_tys
-        put_ bh ty
-    get bh = liftM3 IfaceATD (get bh) (get bh) (get bh)
-
 instance Binary IfaceClassOp where
     put_ bh (IfaceClassOp n def ty) = do 
         put_ bh (occNameFS n)