Add kind equalities to GHC.

This implements the ideas originally put forward in
"System FC with Explicit Kind Equality" (ICFP'13).

There are several noteworthy changes with this patch:
 * We now have casts in types. These change the kind
   of a type. See new constructor `CastTy`.

 * All types and all constructors can be promoted.
   This includes GADT constructors. GADT pattern matches
   take place in type family equations. In Core,
   types can now be applied to coercions via the
   `CoercionTy` constructor.

 * Coercions can now be heterogeneous, relating types
   of different kinds. A coercion proving `t1 :: k1 ~ t2 :: k2`
   proves both that `t1` and `t2` are the same and also that
   `k1` and `k2` are the same.

 * The `Coercion` type has been significantly enhanced.
   The documentation in `docs/core-spec/core-spec.pdf` reflects
   the new reality.

 * The type of `*` is now `*`. No more `BOX`.

 * Users can write explicit kind variables in their code,
   anywhere they can write type variables. For backward compatibility,
   automatic inference of kind-variable binding is still permitted.

 * The new extension `TypeInType` turns on the new user-facing
   features.

 * Type families and synonyms are now promoted to kinds. This causes
   trouble with parsing `*`, leading to the somewhat awkward new
   `HsAppsTy` constructor for `HsType`. This is dispatched with in
   the renamer, where the kind `*` can be told apart from a
   type-level multiplication operator. Without `-XTypeInType` the
   old behavior persists. With `-XTypeInType`, you need to import
   `Data.Kind` to get `*`, also known as `Type`.

 * The kind-checking algorithms in TcHsType have been significantly
   rewritten to allow for enhanced kinds.

 * The new features are still quite experimental and may be in flux.

 * TODO: Several open tickets: #11195, #11196, #11197, #11198, #11203.

 * TODO: Update user manual.

Tickets addressed: #9017, #9173, #7961, #10524, #8566, #11142.
Updates Haddock submodule.

1 files changed, 5 insertions, 5 deletions

diff --git a/compiler/specialise/SpecConstr.hs b/compiler/specialise/SpecConstr.hs
index 1760b0e596..ff4613448e 100644
--- a/compiler/specialise/SpecConstr.hs
+++ b/compiler/specialise/SpecConstr.hs
@@ -31,13 +31,13 @@ import Literal          ( litIsLifted )
 import HscTypes         ( ModGuts(..) )
 import WwLib            ( mkWorkerArgs )
 import DataCon
-import Coercion         hiding( substTy, substCo )
+import Coercion         hiding( substCo )
 import Rules
 import Type             hiding ( substTy )
 import TyCon            ( isRecursiveTyCon, tyConName )
 import Id
 import PprCore          ( pprParendExpr )
-import MkCore           ( mkImpossibleExpr, sortQuantVars )
+import MkCore           ( mkImpossibleExpr )
 import Var
 import VarEnv
 import VarSet
@@ -1643,7 +1643,7 @@ spec_one env fn arg_bndrs body (call_pat@(qvars, pats), rule_number)
 --        return ()
 
                 -- And build the results
-        ; let spec_id    = mkLocalId spec_name (mkPiTypes spec_lam_args body_ty)
+        ; let spec_id    = mkLocalIdOrCoVar spec_name (mkPiTypes spec_lam_args body_ty)
                              -- See Note [Transfer strictness]
                              `setIdStrictness` spec_str
                              `setIdArity` count isId spec_lam_args
@@ -1850,7 +1850,7 @@ callToPats env bndr_occs (Call _ args con_env)
                 -- See Note [Shadowing] at the top
 
               (ktvs, ids)   = partition isTyVar qvars
-              qvars'        = sortQuantVars ktvs ++ map sanitise ids
+              qvars'        = toposortTyVars ktvs ++ map sanitise ids
                 -- Order into kind variables, type variables, term variables
                 -- The kind of a type variable may mention a kind variable
                 -- and the type of a term variable may mention a type variable
@@ -2001,7 +2001,7 @@ argToPat _env _in_scope _val_env arg _arg_occ
 wildCardPat :: Type -> UniqSM (Bool, CoreArg)
 wildCardPat ty
   = do { uniq <- getUniqueM
-       ; let id = mkSysLocal (fsLit "sc") uniq ty
+       ; let id = mkSysLocalOrCoVar (fsLit "sc") uniq ty
        ; return (False, varToCoreExpr id) }
 
 argsToPats :: ScEnv -> InScopeSet -> ValueEnv