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, 12 insertions, 4 deletions

diff --git a/compiler/hsSyn/HsDecls.hs b/compiler/hsSyn/HsDecls.hs
index 48348cc2e1..3f49f42a0e 100644
--- a/compiler/hsSyn/HsDecls.hs
+++ b/compiler/hsSyn/HsDecls.hs
@@ -46,7 +46,7 @@ module HsDecls (
   -- ** @RULE@ declarations
   LRuleDecls,RuleDecls(..),RuleDecl(..), LRuleDecl, RuleBndr(..),LRuleBndr,
   collectRuleBndrSigTys,
-  flattenRuleDecls,
+  flattenRuleDecls, pprFullRuleName,
   -- ** @VECTORISE@ declarations
   VectDecl(..), LVectDecl,
   lvectDeclName, lvectInstDecl,
@@ -638,7 +638,7 @@ countTyClDecls decls
 
 -- | Does this declaration have a complete, user-supplied kind signature?
 -- See Note [Complete user-supplied kind signatures]
-hsDeclHasCusk :: TyClDecl name -> Bool
+hsDeclHasCusk :: TyClDecl Name -> Bool
 hsDeclHasCusk (FamDecl { tcdFam = fam_decl }) = famDeclHasCusk fam_decl
 hsDeclHasCusk (SynDecl { tcdTyVars = tyvars, tcdRhs = rhs })
   = hsTvbAllKinded tyvars && rhs_annotated rhs
@@ -1060,14 +1060,19 @@ getConNames :: ConDecl name -> [Located name]
 getConNames ConDeclH98  {con_name  = name}  = [name]
 getConNames ConDeclGADT {con_names = names} = names
 
+-- don't call with RdrNames, because it can't deal with HsAppsTy
 getConDetails :: ConDecl name -> HsConDeclDetails name
 getConDetails ConDeclH98  {con_details  = details} = details
 getConDetails ConDeclGADT {con_type     = ty     } = details
   where
     (details,_,_,_) = gadtDeclDetails ty
 
+-- don't call with RdrNames, because it can't deal with HsAppsTy
 gadtDeclDetails :: LHsSigType name
-     -> (HsConDeclDetails name,LHsType name,LHsContext name,[LHsTyVarBndr name])
+                -> ( HsConDeclDetails name
+                   , LHsType name
+                   , LHsContext name
+                   , [LHsTyVarBndr name] )
 gadtDeclDetails HsIB {hsib_body = lbody_ty} = (details,res_ty,cxt,tvs)
   where
     (tvs, cxt, tau) = splitLHsSigmaTy lbody_ty
@@ -1635,12 +1640,15 @@ deriving instance (DataId name) => Data (RuleBndr name)
 collectRuleBndrSigTys :: [RuleBndr name] -> [LHsSigWcType name]
 collectRuleBndrSigTys bndrs = [ty | RuleBndrSig _ ty <- bndrs]
 
+pprFullRuleName :: Located (SourceText, RuleName) -> SDoc
+pprFullRuleName (L _ (_, n)) = doubleQuotes $ ftext n
+
 instance OutputableBndr name => Outputable (RuleDecls name) where
   ppr (HsRules _ rules) = ppr rules
 
 instance OutputableBndr name => Outputable (RuleDecl name) where
   ppr (HsRule name act ns lhs _fv_lhs rhs _fv_rhs)
-        = sep [text "{-# RULES" <+> doubleQuotes (ftext $ snd $ unLoc name)
+        = sep [text "{-# RULES" <+> pprFullRuleName name
                                 <+> ppr act,
                nest 4 (pp_forall <+> pprExpr (unLoc lhs)),
                nest 4 (equals <+> pprExpr (unLoc rhs) <+> text "#-}") ]