Re-add FunTy (big patch)

With TypeInType Richard combined ForAllTy and FunTy, but that was often
awkward, and yielded little benefit becuase in practice the two were
always treated separately.  This patch re-introduces FunTy.  Specfically

* New type
    data TyVarBinder = TvBndr TyVar VisibilityFlag
  This /always/ has a TyVar it.  In many places that's just what
  what we want, so there are /lots/ of TyBinder -> TyVarBinder changes

* TyBinder still exists:
    data TyBinder = Named TyVarBinder | Anon Type

* data Type = ForAllTy TyVarBinder Type
            | FunTy Type Type
            |  ....

There are a LOT of knock-on changes, but they are all routine.

The Haddock submodule needs to be updated too

1 files changed, 29 insertions, 31 deletions

diff --git a/compiler/iface/BuildTyCl.hs b/compiler/iface/BuildTyCl.hs
index f62e5eeacb..c20a5ee9e2 100644
--- a/compiler/iface/BuildTyCl.hs
+++ b/compiler/iface/BuildTyCl.hs
@@ -29,7 +29,7 @@ import MkId
 import Class
 import TyCon
 import Type
-import TyCoRep( TyBinder(..) )
+import TyCoRep( TyBinder(..), TyVarBinder(..) )
 import Id
 import TcType
 
@@ -112,9 +112,8 @@ buildDataCon :: FamInstEnvs
             -> Maybe [HsImplBang]
                 -- See Note [Bangs on imported data constructors] in MkId
            -> [FieldLabel]             -- Field labels
-           -> [TyVar] -> [TyBinder]    -- Universals; see
-                                       -- Note [TyBinders in DataCons] in DataCon
-           -> [TyVar] -> [TyBinder]    -- existentials
+           -> [TyVar] -> [TyBinder]    -- Universals
+           -> [TyVarBinder]            -- existentials
            -> [EqSpec]                 -- Equality spec
            -> ThetaType                -- Does not include the "stupid theta"
                                        -- or the GADT equalities
@@ -125,9 +124,9 @@ buildDataCon :: FamInstEnvs
 --   a) makes the worker Id
 --   b) makes the wrapper Id if necessary, including
 --      allocating its unique (hence monadic)
---   c) Sorts out the TyBinders. See Note [TyBinders in DataCons] in DataCon
+--   c) Sorts out the TyVarBinders. See mkDataConUnivTyBinders
 buildDataCon fam_envs src_name declared_infix prom_info src_bangs impl_bangs field_lbls
-             univ_tvs univ_bndrs ex_tvs ex_bndrs eq_spec ctxt arg_tys res_ty rep_tycon
+             univ_tvs univ_bndrs ex_tvs eq_spec ctxt arg_tys res_ty rep_tycon
   = do  { wrap_name <- newImplicitBinder src_name mkDataConWrapperOcc
         ; work_name <- newImplicitBinder src_name mkDataConWorkerOcc
         -- This last one takes the name of the data constructor in the source
@@ -137,11 +136,11 @@ buildDataCon fam_envs src_name declared_infix prom_info src_bangs impl_bangs fie
         ; traceIf (text "buildDataCon 1" <+> ppr src_name)
         ; us <- newUniqueSupply
         ; dflags <- getDynFlags
-        ; let dc_bndrs    = mkDataConUnivTyBinders univ_bndrs univ_tvs
+        ; let dc_bndrs    = mkDataConUnivTyVarBinders univ_tvs univ_bndrs
               stupid_ctxt = mkDataConStupidTheta rep_tycon arg_tys univ_tvs
               data_con = mkDataCon src_name declared_infix prom_info
                                    src_bangs field_lbls
-                                   univ_tvs dc_bndrs ex_tvs ex_bndrs eq_spec ctxt
+                                   dc_bndrs ex_tvs eq_spec ctxt
                                    arg_tys res_ty NoRRI rep_tycon
                                    stupid_ctxt dc_wrk dc_rep
               dc_wrk = mkDataConWorkId work_name data_con
@@ -171,25 +170,25 @@ mkDataConStupidTheta tycon arg_tys univ_tvs
                       tyCoVarsOfType pred `intersectVarSet` arg_tyvars
 
 
-mkDataConUnivTyBinders :: [TyBinder] -> [TyVar]   -- From the TyCon
-                       -> [TyBinder]              -- For the DataCon
+mkDataConUnivTyVarBinders :: [TyVar] -> [TyBinder]   -- From the TyCon
+                          -> [TyVarBinder]           -- For the DataCon
 -- See Note [Building the TyBinders for a DataCon]
-mkDataConUnivTyBinders bndrs tvs
- = zipWith mk_binder bndrs tvs
+mkDataConUnivTyVarBinders tvs bndrs
+ = zipWith mk_binder tvs bndrs
  where
-   mk_binder bndr tv = mkNamedBinder vis tv
+   mk_binder tv bndr = mkTyVarBinder vis tv
       where
         vis = case bndr of
-                Anon _          -> Specified
-                Named _ Visible -> Specified
-                Named _ vis     -> vis
+                Anon _                   -> Specified
+                Named (TvBndr _ Visible) -> Specified
+                Named (TvBndr _ vis)     -> vis
 
 {- Note [Building the TyBinders for a DataCon]
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 A DataCon needs to keep track of the visibility of its universals and
 existentials, so that visible type application can work properly. This
-is done by storing the universal and existential TyBinders, along with
-the TyVars.  See Note [TyBinders in DataCons] in DataCon.
+is done by storing the universal and existential TyVarBinders.
+See Note [TyVarBinders in DataCons] in DataCon.
 
 During construction of a DataCon, we often start from the TyBinders of
 the parent TyCon.  For example
@@ -203,8 +202,8 @@ of the DataCon. Here is an example:
 
 The TyCon has
 
-  tyConTyVars    = [ k:*,                      a:k->*,      b:k]
-  tyConTyBinders = [ Named (k :: *) Invisible, Anon (k->*), Anon k ]
+  tyConTyVars    = [ k:*,                               a:k->*,      b:k]
+  tyConTyBinders = [ Named (TvBndr (k :: *) Invisible), Anon (k->*), Anon k ]
 
 The TyBinders for App line up with App's kind, given above.
 
@@ -213,9 +212,9 @@ But the DataCon MkApp has the type
 
 That is, its TyBinders should be
 
-  dataConUnivTyVars = [ Named (k:*)    Invisible
-                      , Named (a:k->*) Specified
-                      , Named (b:k)    Specified ]
+  dataConUnivTyVarBinders = [ TvBndr (k:*)    Invisible
+                            , TvBndr (a:k->*) Specified
+                            , TvBndr (b:k)    Specified ]
 
 So we want to take the TyCon's TyBinders and the TyCon's TyVars and
 merge them, pulling
@@ -237,15 +236,15 @@ DataCon (mkDataCon does no further work).
 ------------------------------------------------------
 buildPatSyn :: Name -> Bool
             -> (Id,Bool) -> Maybe (Id, Bool)
-            -> ([TyVar], [TyBinder], ThetaType) -- ^ Univ and req
-            -> ([TyVar], [TyBinder], ThetaType) -- ^ Ex and prov
+            -> ([TyVarBinder], ThetaType) -- ^ Univ and req
+            -> ([TyVarBinder], ThetaType) -- ^ Ex and prov
             -> [Type]               -- ^ Argument types
             -> Type                 -- ^ Result type
             -> [FieldLabel]         -- ^ Field labels for
                                     --   a record pattern synonym
             -> PatSyn
 buildPatSyn src_name declared_infix matcher@(matcher_id,_) builder
-            (univ_tvs, univ_bndrs, req_theta) (ex_tvs, ex_bndrs, prov_theta) arg_tys
+            (univ_tvs, req_theta) (ex_tvs, prov_theta) arg_tys
             pat_ty field_labels
   = -- The assertion checks that the matcher is
     -- compatible with the pattern synonym
@@ -263,17 +262,17 @@ buildPatSyn src_name declared_infix matcher@(matcher_id,_) builder
                     , ppr req_theta <+> twiddle <+> ppr req_theta1
                     , ppr arg_tys <+> twiddle <+> ppr arg_tys1]))
     mkPatSyn src_name declared_infix
-             (univ_tvs, univ_bndrs, req_theta) (ex_tvs, ex_bndrs, prov_theta)
+             (univ_tvs, req_theta) (ex_tvs, prov_theta)
              arg_tys pat_ty
              matcher builder field_labels
   where
     ((_:_:univ_tvs1), req_theta1, tau) = tcSplitSigmaTy $ idType matcher_id
-    ([pat_ty1, cont_sigma, _], _) = tcSplitFunTys tau
-    (ex_tvs1, prov_theta1, cont_tau) = tcSplitSigmaTy cont_sigma
+    ([pat_ty1, cont_sigma, _], _)      = tcSplitFunTys tau
+    (ex_tvs1, prov_theta1, cont_tau)   = tcSplitSigmaTy cont_sigma
     (arg_tys1, _) = tcSplitFunTys cont_tau
     twiddle = char '~'
     subst = zipTvSubst (univ_tvs1 ++ ex_tvs1)
-                       (mkTyVarTys (univ_tvs ++ ex_tvs))
+                       (mkTyVarTys (map binderVar (univ_tvs ++ ex_tvs)))
 
 ------------------------------------------------------
 type TcMethInfo = (Name, Type, Maybe (DefMethSpec Type))
@@ -342,7 +341,6 @@ buildClass tycon_name tvs roles sc_theta binders
                                    [{- No fields -}]
                                    tvs binders
                                    [{- no existentials -}]
-                                   [{- no existentials -}]
                                    [{- No GADT equalities -}]
                                    [{- No theta -}]
                                    arg_tys