Explicit Specificity

Implementation for Ticket #16393.
Explicit specificity allows users to manually create inferred type variables,
by marking them with braces.
This way, the user determines which variables can be instantiated through
visible type application.

The additional syntax is included in the parser, allowing users to write
braces in type variable binders (type signatures, data constructors etc).
This information is passed along through the renamer and verified in the
type checker.
The AST for type variable binders, data constructors, pattern synonyms,
partial signatures and Template Haskell has been updated to include the
specificity of type variables.

Minor notes:
- Bumps haddock submodule
- Disables pattern match checking in GHC.Iface.Type with GHC 8.8

1 files changed, 8 insertions, 8 deletions

diff --git a/compiler/GHC/Iface/Syntax.hs b/compiler/GHC/Iface/Syntax.hs
index e69e546a89..cfa34ab7bb 100644
--- a/compiler/GHC/Iface/Syntax.hs
+++ b/compiler/GHC/Iface/Syntax.hs
@@ -65,7 +65,7 @@ import GHC.Types.SrcLoc
 import GHC.Utils.Fingerprint
 import GHC.Utils.Binary
 import GHC.Data.BooleanFormula ( BooleanFormula, pprBooleanFormula, isTrue )
-import GHC.Types.Var( VarBndr(..), binderVar )
+import GHC.Types.Var( VarBndr(..), binderVar, tyVarSpecToBinders )
 import GHC.Core.TyCon ( Role (..), Injectivity(..), tyConBndrVisArgFlag )
 import GHC.Utils.Misc( dropList, filterByList, notNull, unzipWith, debugIsOn )
 import GHC.Core.DataCon (SrcStrictness(..), SrcUnpackedness(..))
@@ -163,8 +163,8 @@ data IfaceDecl
                   ifPatBuilder    :: Maybe (IfExtName, Bool),
                   -- Everything below is redundant,
                   -- but needed to implement pprIfaceDecl
-                  ifPatUnivBndrs  :: [IfaceForAllBndr],
-                  ifPatExBndrs    :: [IfaceForAllBndr],
+                  ifPatUnivBndrs  :: [IfaceForAllSpecBndr],
+                  ifPatExBndrs    :: [IfaceForAllSpecBndr],
                   ifPatProvCtxt   :: IfaceContext,
                   ifPatReqCtxt    :: IfaceContext,
                   ifPatArgs       :: [IfaceType],
@@ -248,7 +248,7 @@ data IfaceConDecl
         -- So this guarantee holds for IfaceConDecl, but *not* for DataCon
 
         ifConExTCvs   :: [IfaceBndr],  -- Existential ty/covars
-        ifConUserTvBinders :: [IfaceForAllBndr],
+        ifConUserTvBinders :: [IfaceForAllSpecBndr],
           -- The tyvars, in the order the user wrote them
           -- INVARIANT: the set of tyvars in ifConUserTvBinders is exactly the
           --            set of tyvars (*not* covars) of ifConExTCvs, unioned
@@ -970,8 +970,8 @@ pprIfaceDecl _ (IfacePatSyn { ifName = name,
                              , pprIfaceContextArr prov_ctxt
                              , pprIfaceType $ foldr (IfaceFunTy VisArg) pat_ty arg_tys ])
       where
-        univ_msg = pprUserIfaceForAll univ_bndrs
-        ex_msg   = pprUserIfaceForAll ex_bndrs
+        univ_msg = pprUserIfaceForAll $ tyVarSpecToBinders univ_bndrs
+        ex_msg   = pprUserIfaceForAll $ tyVarSpecToBinders ex_bndrs
 
         insert_empty_ctxt = null req_ctxt
             && not (null prov_ctxt && isEmpty sdocCtx ex_msg)
@@ -1099,9 +1099,9 @@ pprIfaceConDecl ss gadt_style tycon tc_binders parent
     -- the visibilities of the existential tyvar binders, we can simply drop
     -- the universal tyvar binders from user_tvbs.
     ex_tvbs = dropList tc_binders user_tvbs
-    ppr_ex_quant = pprIfaceForAllPartMust ex_tvbs ctxt
+    ppr_ex_quant = pprIfaceForAllPartMust (ifaceForAllSpecToBndrs ex_tvbs) ctxt
     pp_gadt_res_ty = mk_user_con_res_ty eq_spec
-    ppr_gadt_ty = pprIfaceForAllPart user_tvbs ctxt pp_tau
+    ppr_gadt_ty = pprIfaceForAllPart (ifaceForAllSpecToBndrs user_tvbs) ctxt pp_tau
 
         -- A bit gruesome this, but we can't form the full con_tau, and ppr it,
         -- because we don't have a Name for the tycon, only an OccName