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, 19 insertions, 16 deletions

diff --git a/libraries/template-haskell/Language/Haskell/TH/Lib.hs b/libraries/template-haskell/Language/Haskell/TH/Lib.hs
index 0ec932d00b..4df23cd3c5 100644
--- a/libraries/template-haskell/Language/Haskell/TH/Lib.hs
+++ b/libraries/template-haskell/Language/Haskell/TH/Lib.hs
@@ -18,12 +18,13 @@ module Language.Haskell.TH.Lib (
 
     -- * Library functions
     -- ** Abbreviations
-        InfoQ, ExpQ, TExpQ, DecQ, DecsQ, ConQ, TypeQ, KindQ, TyVarBndrQ,
+        InfoQ, ExpQ, TExpQ, DecQ, DecsQ, ConQ, TypeQ, KindQ,
         TyLitQ, CxtQ, PredQ, DerivClauseQ, MatchQ, ClauseQ, BodyQ, GuardQ,
         StmtQ, RangeQ, SourceStrictnessQ, SourceUnpackednessQ, BangQ,
         BangTypeQ, VarBangTypeQ, StrictTypeQ, VarStrictTypeQ, FieldExpQ, PatQ,
         FieldPatQ, RuleBndrQ, TySynEqnQ, PatSynDirQ, PatSynArgsQ,
         FamilyResultSigQ, DerivStrategyQ,
+        TyVarBndrUnit, TyVarBndrSpec,
 
     -- ** Constructors lifted to 'Q'
     -- *** Literals
@@ -75,6 +76,8 @@ module Language.Haskell.TH.Lib (
 
     -- *** Type variable binders
     plainTV, kindedTV,
+    plainInvisTV, kindedInvisTV,
+    specifiedSpec, inferredSpec,
 
     -- *** Roles
     nominalR, representationalR, phantomR, inferR,
@@ -174,10 +177,10 @@ import Prelude
 -------------------------------------------------------------------------------
 -- *   Dec
 
-tySynD :: Quote m => Name -> [TyVarBndr] -> m Type -> m Dec
+tySynD :: Quote m => Name -> [TyVarBndr ()] -> m Type -> m Dec
 tySynD tc tvs rhs = do { rhs1 <- rhs; return (TySynD tc tvs rhs1) }
 
-dataD :: Quote m => m Cxt -> Name -> [TyVarBndr] -> Maybe Kind -> [m Con] -> [m DerivClause]
+dataD :: Quote m => m Cxt -> Name -> [TyVarBndr ()] -> Maybe Kind -> [m Con] -> [m DerivClause]
       -> m Dec
 dataD ctxt tc tvs ksig cons derivs =
   do
@@ -186,7 +189,7 @@ dataD ctxt tc tvs ksig cons derivs =
     derivs1 <- sequenceA derivs
     return (DataD ctxt1 tc tvs ksig cons1 derivs1)
 
-newtypeD :: Quote m => m Cxt -> Name -> [TyVarBndr] -> Maybe Kind -> m Con -> [m DerivClause]
+newtypeD :: Quote m => m Cxt -> Name -> [TyVarBndr ()] -> Maybe Kind -> m Con -> [m DerivClause]
          -> m Dec
 newtypeD ctxt tc tvs ksig con derivs =
   do
@@ -195,7 +198,7 @@ newtypeD ctxt tc tvs ksig con derivs =
     derivs1 <- sequenceA derivs
     return (NewtypeD ctxt1 tc tvs ksig con1 derivs1)
 
-classD :: Quote m => m Cxt -> Name -> [TyVarBndr] -> [FunDep] -> [m Dec] -> m Dec
+classD :: Quote m => m Cxt -> Name -> [TyVarBndr ()] -> [FunDep] -> [m Dec] -> m Dec
 classD ctxt cls tvs fds decs =
   do
     decs1 <- sequenceA decs
@@ -230,35 +233,35 @@ newtypeInstD ctxt tc tys ksig con derivs =
     derivs1 <- sequenceA derivs
     return (NewtypeInstD ctxt1 Nothing ty1 ksig con1 derivs1)
 
-dataFamilyD :: Quote m => Name -> [TyVarBndr] -> Maybe Kind -> m Dec
+dataFamilyD :: Quote m => Name -> [TyVarBndr ()] -> Maybe Kind -> m Dec
 dataFamilyD tc tvs kind
     = pure $ DataFamilyD tc tvs kind
 
-openTypeFamilyD :: Quote m => Name -> [TyVarBndr] -> FamilyResultSig
+openTypeFamilyD :: Quote m => Name -> [TyVarBndr ()] -> FamilyResultSig
                 -> Maybe InjectivityAnn -> m Dec
 openTypeFamilyD tc tvs res inj
     = pure $ OpenTypeFamilyD (TypeFamilyHead tc tvs res inj)
 
-closedTypeFamilyD :: Quote m => Name -> [TyVarBndr] -> FamilyResultSig
+closedTypeFamilyD :: Quote m => Name -> [TyVarBndr ()] -> FamilyResultSig
                   -> Maybe InjectivityAnn -> [m TySynEqn] -> m Dec
 closedTypeFamilyD tc tvs result injectivity eqns =
   do eqns1 <- sequenceA eqns
      return (ClosedTypeFamilyD (TypeFamilyHead tc tvs result injectivity) eqns1)
 
-tySynEqn :: Quote m => (Maybe [TyVarBndr]) -> m Type -> m Type -> m TySynEqn
+tySynEqn :: Quote m => (Maybe [TyVarBndr ()]) -> m Type -> m Type -> m TySynEqn
 tySynEqn tvs lhs rhs =
   do
     lhs1 <- lhs
     rhs1 <- rhs
     return (TySynEqn tvs lhs1 rhs1)
 
-forallC :: Quote m => [TyVarBndr] -> m Cxt -> m Con -> m Con
+forallC :: Quote m => [TyVarBndr Specificity] -> m Cxt -> m Con -> m Con
 forallC ns ctxt con = liftA2 (ForallC ns) ctxt con
 
 -------------------------------------------------------------------------------
 -- *   Type
 
-forallT :: Quote m => [TyVarBndr] -> m Cxt -> m Type -> m Type
+forallT :: Quote m => [TyVarBndr Specificity] -> m Cxt -> m Type -> m Type
 forallT tvars ctxt ty = do
     ctxt1 <- ctxt
     ty1   <- ty
@@ -273,11 +276,11 @@ sigT t k
 -------------------------------------------------------------------------------
 -- *   Kind
 
-plainTV :: Name -> TyVarBndr
-plainTV = PlainTV
+plainTV :: Name -> TyVarBndr ()
+plainTV n = PlainTV n ()
 
-kindedTV :: Name -> Kind -> TyVarBndr
-kindedTV = KindedTV
+kindedTV :: Name -> Kind -> TyVarBndr ()
+kindedTV n k = KindedTV n () k
 
 starK :: Kind
 starK = StarT
@@ -294,7 +297,7 @@ noSig = NoSig
 kindSig :: Kind -> FamilyResultSig
 kindSig = KindSig
 
-tyVarSig :: TyVarBndr -> FamilyResultSig
+tyVarSig :: TyVarBndr () -> FamilyResultSig
 tyVarSig = TyVarSig
 
 -------------------------------------------------------------------------------