{- Language/Haskell/TH/Desugar.hs

(c) Richard Eisenberg 2013
rae@cs.brynmawr.edu
-}

{-# LANGUAGE CPP, MultiParamTypeClasses, FunctionalDependencies,
             TypeSynonymInstances, FlexibleInstances, LambdaCase,
             ScopedTypeVariables, PatternSynonyms #-}

-----------------------------------------------------------------------------
-- |
-- Module      :  Language.Haskell.TH.Desugar
-- Copyright   :  (C) 2014 Richard Eisenberg
-- License     :  BSD-style (see LICENSE)
-- Maintainer  :  Ryan Scott
-- Stability   :  experimental
-- Portability :  non-portable
--
-- Desugars full Template Haskell syntax into a smaller core syntax for further
-- processing.
--
----------------------------------------------------------------------------

module Language.Haskell.TH.Desugar (
  -- * Desugared data types
  DExp(..), DLetDec(..), NamespaceSpecifier(..), DPat(..),
  DType(..), DForallTelescope(..), DKind, DCxt, DPred,
  DTyVarBndr(..), DTyVarBndrSpec, DTyVarBndrUnit, Specificity(..),
  DTyVarBndrVis,
#if __GLASGOW_HASKELL__ >= 907
  BndrVis(..),
#else
  BndrVis,
  pattern BndrReq,
  pattern BndrInvis,
#endif
  DMatch(..), DClause(..), DDec(..),
  DDerivClause(..), DDerivStrategy(..), DPatSynDir(..), DPatSynType,
  Overlap(..), PatSynArgs(..), DataFlavor(..),
  DTypeFamilyHead(..), DFamilyResultSig(..), InjectivityAnn(..),
  DCon(..), DConFields(..), DDeclaredInfix, DBangType, DVarBangType,
  Bang(..), SourceUnpackedness(..), SourceStrictness(..),
  DForeign(..),
  DPragma(..), DRuleBndr(..), DTySynEqn(..), DInfo(..), DInstanceDec,
  Role(..), AnnTarget(..),

  -- * The 'Desugar' class
  Desugar(..),

  -- * Main desugaring functions
  dsExp, dsDecs, dsType, dsInfo,
  dsPatOverExp, dsPatsOverExp, dsPatX,
  dsLetDecs, dsTvb, dsTvbSpec, dsTvbUnit, dsTvbVis, dsCxt,
  dsCon, dsForeign, dsPragma, dsRuleBndr,

  -- ** Secondary desugaring functions
  PatM, dsPred, dsPat, dsDec, dsDataDec, dsDataInstDec,
  DerivingClause, dsDerivClause, dsLetDec,
  dsMatches, dsBody, dsGuards, dsDoStmts, dsComp, dsClauses,
  dsBangType, dsVarBangType,
  dsTypeFamilyHead, dsFamilyResultSig,
#if __GLASGOW_HASKELL__ >= 801
  dsPatSynDir,
#endif
  dsTypeArg,

  -- * Converting desugared AST back to TH AST
  module Language.Haskell.TH.Desugar.Sweeten,

  -- * Expanding type synonyms
  expand, expandType,

  -- * Reification
  reifyWithWarning,

  -- ** Local reification
  -- $localReification
  withLocalDeclarations, dsReify, dsReifyType,
  reifyWithLocals_maybe, reifyWithLocals, reifyFixityWithLocals,
  reifyTypeWithLocals_maybe, reifyTypeWithLocals,
  lookupValueNameWithLocals, lookupTypeNameWithLocals,
  mkDataNameWithLocals, mkTypeNameWithLocals,
  reifyNameSpace,
  DsMonad(..), DsM,

  -- * Nested pattern flattening
  scExp, scLetDec,

  -- * Capture-avoiding substitution and utilities
  module Language.Haskell.TH.Desugar.Subst,

  -- * Free variable calculation
  module Language.Haskell.TH.Desugar.FV,

  -- * Utility functions
  applyDExp,
  dPatToDExp, removeWilds,
  getDataD, dataConNameToDataName, dataConNameToCon,
  nameOccursIn, allNamesIn, flattenDValD, getRecordSelectors,
  mkTypeName, mkDataName, newUniqueName,
  mkTupleDExp, mkTupleDPat, maybeDLetE, maybeDCaseE, mkDLamEFromDPats,
  tupleNameDegree_maybe,
  unboxedSumNameDegree_maybe, unboxedTupleNameDegree_maybe,
  isTypeKindName, typeKindName, bindIP,
  mkExtraDKindBinders, dTyVarBndrToDType, changeDTVFlags,
  toposortTyVarsOf, toposortKindVarsOfTvbs,

  -- ** 'FunArgs' and 'VisFunArg'
  FunArgs(..), ForallTelescope(..), VisFunArg(..),
  filterVisFunArgs, ravelType, unravelType,

  -- ** 'DFunArgs' and 'DVisFunArg'
  DFunArgs(..), DVisFunArg(..),
  filterDVisFunArgs, ravelDType, unravelDType,

  -- ** 'TypeArg'
  TypeArg(..), applyType, filterTANormals,
  tyVarBndrVisToTypeArg, tyVarBndrVisToTypeArgWithSig,
  unfoldType,

  -- ** 'DTypeArg'
  DTypeArg(..), applyDType, filterDTANormals,
  dTyVarBndrVisToDTypeArg, dTyVarBndrVisToDTypeArgWithSig,
  unfoldDType,

  -- ** Extracting bound names
  extractBoundNamesStmt, extractBoundNamesDec, extractBoundNamesPat
  ) where

import Language.Haskell.TH.Datatype.TyVarBndr
import Language.Haskell.TH.Desugar.AST
import Language.Haskell.TH.Desugar.Core
import Language.Haskell.TH.Desugar.Expand
import Language.Haskell.TH.Desugar.FV
import Language.Haskell.TH.Desugar.Match
import Language.Haskell.TH.Desugar.Reify
import Language.Haskell.TH.Desugar.Subst
import Language.Haskell.TH.Desugar.Sweeten
import Language.Haskell.TH.Desugar.Util
import Language.Haskell.TH.Syntax

import Control.Monad
import qualified Data.Foldable as F
import Data.Function
import qualified Data.Map as M
import qualified Data.Set as S
import Prelude hiding ( exp )

-- | This class relates a TH type with its th-desugar type and allows
-- conversions back and forth. The functional dependency goes only one
-- way because we define the following instances on old versions of GHC:
--
-- @
-- instance 'Desugar' 'TyVarBndrSpec' 'DTyVarBndrSpec'
-- instance 'Desugar' 'TyVarBndrUnit' 'DTyVarBndrUnit'
-- @
--
-- Prior to GHC 9.0, 'TyVarBndrSpec' and 'TyVarBndrUnit' are simply type
-- synonyms for 'TyVarBndr', so making the functional dependencies
-- bidirectional would cause these instances to be rejected.
class Desugar th ds | ds -> th where
  desugar :: DsMonad q => th -> q ds
  sweeten :: ds -> th

instance Desugar Exp DExp where
  desugar :: forall (q :: * -> *). DsMonad q => Exp -> q DExp
desugar = Exp -> q DExp
forall (q :: * -> *). DsMonad q => Exp -> q DExp
dsExp
  sweeten :: DExp -> Exp
sweeten = DExp -> Exp
expToTH

instance Desugar Type DType where
  desugar :: forall (q :: * -> *). DsMonad q => Type -> q DType
desugar = Type -> q DType
forall (q :: * -> *). DsMonad q => Type -> q DType
dsType
  sweeten :: DType -> Type
sweeten = DType -> Type
typeToTH

instance Desugar Cxt DCxt where
  desugar :: forall (q :: * -> *). DsMonad q => Cxt -> q DCxt
desugar = Cxt -> q DCxt
forall (q :: * -> *). DsMonad q => Cxt -> q DCxt
dsCxt
  sweeten :: DCxt -> Cxt
sweeten = DCxt -> Cxt
cxtToTH

#if __GLASGOW_HASKELL__ >= 900
-- | This instance is only @flag@-polymorphic on GHC 9.0 or later, since
-- previous versions of GHC do not equip 'TyVarBndr' with a @flag@ type
-- parameter. As a result, we define two separate instances for 'DTyVarBndr'
-- on older GHCs:
--
-- @
-- instance 'Desugar' 'TyVarBndrSpec' 'DTyVarBndrSpec'
-- instance 'Desugar' 'TyVarBndrUnit' 'DTyVarBndrUnit'
-- @
instance Desugar (TyVarBndr flag) (DTyVarBndr flag) where
  desugar :: forall (q :: * -> *).
DsMonad q =>
TyVarBndr flag -> q (DTyVarBndr flag)
desugar = TyVarBndr flag -> q (DTyVarBndr flag)
forall (q :: * -> *) flag.
DsMonad q =>
TyVarBndr_ flag -> q (DTyVarBndr flag)
dsTvb
  sweeten :: DTyVarBndr flag -> TyVarBndr flag
sweeten = DTyVarBndr flag -> TyVarBndr flag
forall flag. DTyVarBndr flag -> TyVarBndr flag
tvbToTH
#else
-- | This instance monomorphizes the @flag@ parameter of 'DTyVarBndr' since
-- pre-9.0 versions of GHC do not equip 'TyVarBndr' with a @flag@ type
-- parameter. There is also a corresponding instance for
-- 'TyVarBndrUnit'/'DTyVarBndrUnit'.
instance Desugar TyVarBndrSpec DTyVarBndrSpec where
  desugar = dsTvbSpec
  sweeten = tvbToTH

-- | This instance monomorphizes the @flag@ parameter of 'DTyVarBndr' since
-- pre-9.0 versions of GHC do not equip 'TyVarBndr' with a @flag@ type
-- parameter. There is also a corresponding instance for
-- 'TyVarBndrSpec'/'DTyVarBndrSpec'.
instance Desugar TyVarBndrUnit DTyVarBndrUnit where
  desugar = dsTvbUnit
  sweeten = tvbToTH
#endif

instance Desugar [Dec] [DDec] where
  desugar :: forall (q :: * -> *). DsMonad q => [Dec] -> q [DDec]
desugar = [Dec] -> q [DDec]
forall (q :: * -> *). DsMonad q => [Dec] -> q [DDec]
dsDecs
  sweeten :: [DDec] -> [Dec]
sweeten = [DDec] -> [Dec]
decsToTH

instance Desugar TypeArg DTypeArg where
  desugar :: forall (q :: * -> *). DsMonad q => TypeArg -> q DTypeArg
desugar = TypeArg -> q DTypeArg
forall (q :: * -> *). DsMonad q => TypeArg -> q DTypeArg
dsTypeArg
  sweeten :: DTypeArg -> TypeArg
sweeten = DTypeArg -> TypeArg
typeArgToTH

-- | If the declaration passed in is a 'DValD', creates new, equivalent
-- declarations such that the 'DPat' in all 'DValD's is just a plain
-- 'DVarPa'. Other declarations are passed through unchanged.
-- Note that the declarations that come out of this function are rather
-- less efficient than those that come in: they have many more pattern
-- matches.
flattenDValD :: Quasi q => DLetDec -> q [DLetDec]
flattenDValD :: forall (q :: * -> *). Quasi q => DLetDec -> q [DLetDec]
flattenDValD dec :: DLetDec
dec@(DValD (DVarP Name
_) DExp
_) = [DLetDec] -> q [DLetDec]
forall a. a -> q a
forall (m :: * -> *) a. Monad m => a -> m a
return [DLetDec
dec]
flattenDValD (DValD DPat
pat DExp
exp) = do
  x <- String -> q Name
forall (q :: * -> *). Quasi q => String -> q Name
newUniqueName String
"x" -- must use newUniqueName here because we might be top-level
  let top_val_d = DPat -> DExp -> DLetDec
DValD (Name -> DPat
DVarP Name
x) DExp
exp
      bound_names = OSet Name -> [Name]
forall a. OSet a -> [a]
forall (t :: * -> *) a. Foldable t => t a -> [a]
F.toList (OSet Name -> [Name]) -> OSet Name -> [Name]
forall a b. (a -> b) -> a -> b
$ DPat -> OSet Name
extractBoundNamesDPat DPat
pat
  other_val_ds <- mapM (mk_val_d x) bound_names
  return $ top_val_d : other_val_ds
  where
    mk_val_d :: Name -> Name -> m DLetDec
mk_val_d Name
x Name
name = do
      y <- String -> m Name
forall (q :: * -> *). Quasi q => String -> q Name
newUniqueName String
"y"
      let pat'  = Name -> Name -> DPat -> DPat
wildify Name
name Name
y DPat
pat
          match = DPat -> DExp -> DMatch
DMatch DPat
pat' (Name -> DExp
DVarE Name
y)
          cas   = DExp -> [DMatch] -> DExp
DCaseE (Name -> DExp
DVarE Name
x) [DMatch
match]
      return $ DValD (DVarP name) cas

    wildify :: Name -> Name -> DPat -> DPat
wildify Name
name Name
y DPat
p =
      case DPat
p of
        DLitP Lit
lit -> Lit -> DPat
DLitP Lit
lit
        DVarP Name
n
          | Name
n Name -> Name -> Bool
forall a. Eq a => a -> a -> Bool
== Name
name -> Name -> DPat
DVarP Name
y
          | Bool
otherwise -> DPat
DWildP
        DConP Name
con DCxt
ts [DPat]
ps -> Name -> DCxt -> [DPat] -> DPat
DConP Name
con DCxt
ts ((DPat -> DPat) -> [DPat] -> [DPat]
forall a b. (a -> b) -> [a] -> [b]
map (Name -> Name -> DPat -> DPat
wildify Name
name Name
y) [DPat]
ps)
        DTildeP DPat
pa -> DPat -> DPat
DTildeP (Name -> Name -> DPat -> DPat
wildify Name
name Name
y DPat
pa)
        DBangP DPat
pa -> DPat -> DPat
DBangP (Name -> Name -> DPat -> DPat
wildify Name
name Name
y DPat
pa)
        DSigP DPat
pa DType
ty -> DPat -> DType -> DPat
DSigP (Name -> Name -> DPat -> DPat
wildify Name
name Name
y DPat
pa) DType
ty
        DPat
DWildP -> DPat
DWildP
        DTypeP DType
ty -> DType -> DPat
DTypeP DType
ty
        DInvisP DType
ty -> DType -> DPat
DInvisP DType
ty

flattenDValD DLetDec
other_dec = [DLetDec] -> q [DLetDec]
forall a. a -> q a
forall (m :: * -> *) a. Monad m => a -> m a
return [DLetDec
other_dec]

-- | Produces 'DLetDec's representing the record selector functions from
-- the provided 'DCon's.
--
-- Note that if the same record selector appears in multiple constructors,
-- 'getRecordSelectors' will return only one binding for that selector.
-- For example, if you had:
--
-- @
-- data X = X1 {y :: Symbol} | X2 {y :: Symbol}
-- @
--
-- Then calling 'getRecordSelectors' on @[X1, X2]@ will return:
--
-- @
-- [ DSigD y (DAppT (DAppT DArrowT (DConT X)) (DConT Symbol))
-- , DFunD y [ DClause [DConP X1 [DVarP field]] (DVarE field)
--           , DClause [DConP X2 [DVarP field]] (DVarE field) ] ]
-- @
--
-- instead of returning one binding for @X1@ and another binding for @X2@.
--
-- 'getRecordSelectors' does not attempt to filter out \"naughty\" record
-- selectors—that is, records whose field types mention existentially
-- quantified type variables that do not appear in the constructor's return
-- type. Here is an example of a naughty record selector:
--
-- @
-- data Some :: (Type -> Type) -> Type where
--   MkSome :: { getSome :: f a } -> Some f
-- @
--
-- GHC itself will not allow the use of @getSome@ as a top-level function due
-- to its type @f a@ mentioning the existential variable @a@, but
-- 'getRecordSelectors' will return it nonetheless. Ultimately, this design
-- choice is a practical one, as detecting which type variables are existential
-- in Template Haskell is difficult in the general case.
getRecordSelectors :: DsMonad q => [DCon] -> q [DLetDec]
getRecordSelectors :: forall (q :: * -> *). DsMonad q => [DCon] -> q [DLetDec]
getRecordSelectors [DCon]
cons = [DLetDec] -> [DLetDec]
merge_let_decs ([DLetDec] -> [DLetDec]) -> q [DLetDec] -> q [DLetDec]
forall a b. (a -> b) -> q a -> q b
forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
`fmap` (DCon -> q [DLetDec]) -> [DCon] -> q [DLetDec]
forall (monad :: * -> *) monoid (t :: * -> *) a.
(Monad monad, Monoid monoid, Traversable t) =>
(a -> monad monoid) -> t a -> monad monoid
concatMapM DCon -> q [DLetDec]
forall {m :: * -> *}. Quasi m => DCon -> m [DLetDec]
get_record_sels [DCon]
cons
  where
    get_record_sels :: DCon -> m [DLetDec]
get_record_sels (DCon [DTyVarBndrSpec]
con_tvbs DCxt
_ Name
con_name DConFields
con_fields DType
con_ret_ty) =
      case DConFields
con_fields of
        DRecC [DVarBangType]
fields -> [DVarBangType] -> m [DLetDec]
forall {m :: * -> *} {b}.
Quasi m =>
[(Name, b, DType)] -> m [DLetDec]
go [DVarBangType]
fields
        DNormalC{}   -> [DLetDec] -> m [DLetDec]
forall a. a -> m a
forall (m :: * -> *) a. Monad m => a -> m a
return []
        where
          go :: [(Name, b, DType)] -> m [DLetDec]
go [(Name, b, DType)]
fields = do
            varName <- String -> m Name
forall (q :: * -> *). Quasi q => String -> q Name
qNewName String
"field"
            return $ concat
              [ [ DSigD name $ DForallT (DForallInvis con_tvbs)
                             $ DArrowT `DAppT` con_ret_ty `DAppT` field_ty
                , DFunD name [DClause [DConP con_name []
                                         (mk_field_pats n (length fields) varName)]
                                      (DVarE varName)] ]
              | ((name, _strict, field_ty), n) <- zip fields [0..]
              ]

    mk_field_pats :: Int -> Int -> Name -> [DPat]
    mk_field_pats :: Int -> Int -> Name -> [DPat]
mk_field_pats Int
0 Int
total Name
name = Name -> DPat
DVarP Name
name DPat -> [DPat] -> [DPat]
forall a. a -> [a] -> [a]
: (Int -> DPat -> [DPat]
forall a. Int -> a -> [a]
replicate (Int
totalInt -> Int -> Int
forall a. Num a => a -> a -> a
-Int
1) DPat
DWildP)
    mk_field_pats Int
n Int
total Name
name = DPat
DWildP DPat -> [DPat] -> [DPat]
forall a. a -> [a] -> [a]
: Int -> Int -> Name -> [DPat]
mk_field_pats (Int
nInt -> Int -> Int
forall a. Num a => a -> a -> a
-Int
1) (Int
totalInt -> Int -> Int
forall a. Num a => a -> a -> a
-Int
1) Name
name

    merge_let_decs :: [DLetDec] -> [DLetDec]
    merge_let_decs :: [DLetDec] -> [DLetDec]
merge_let_decs [DLetDec]
decs =
      let (Map Name [DClause]
name_clause_map, [DLetDec]
decs') = Map Name [DClause]
-> Set Name -> [DLetDec] -> (Map Name [DClause], [DLetDec])
gather_decs Map Name [DClause]
forall k a. Map k a
M.empty Set Name
forall a. Set a
S.empty [DLetDec]
decs
       in Map Name [DClause] -> [DLetDec] -> [DLetDec]
augment_clauses Map Name [DClause]
name_clause_map [DLetDec]
decs'
        -- First, for each record selector-related declarations, do the following:
        --
        -- 1. If it's a DFunD...
        --   a. If we haven't encountered it before, add a mapping from its Name
        --      to its associated DClauses, and continue.
        --   b. If we have encountered it before, augment the existing Name's
        --      mapping with the new clauses. Then remove the DFunD from the list
        --      and continue.
        -- 2. If it's a DSigD...
        --   a. If we haven't encountered it before, remember its Name and continue.
        --   b. If we have encountered it before, remove the DSigD from the list
        --      and continue.
        -- 3. Otherwise, continue.
        --
        -- After this, scan over the resulting list once more with the mapping
        -- that we accumulated. For every DFunD, replace its DClauses with the
        -- ones corresponding to its Name in the mapping.
        --
        -- Note that this algorithm combines all of the DClauses for each unique
        -- Name, while preserving the order in which the DFunDs were originally
        -- found. Moreover, it removes duplicate DSigD entries. Using Maps and
        -- Sets avoid quadratic blowup for data types with many record selectors.
      where
        gather_decs :: M.Map Name [DClause] -> S.Set Name -> [DLetDec]
                    -> (M.Map Name [DClause], [DLetDec])
        gather_decs :: Map Name [DClause]
-> Set Name -> [DLetDec] -> (Map Name [DClause], [DLetDec])
gather_decs Map Name [DClause]
name_clause_map Set Name
_ [] = (Map Name [DClause]
name_clause_map, [])
        gather_decs Map Name [DClause]
name_clause_map Set Name
type_sig_names (DLetDec
x:[DLetDec]
xs)
          -- 1.
          | DFunD Name
n [DClause]
clauses <- DLetDec
x
          = let name_clause_map' :: Map Name [DClause]
name_clause_map' = ([DClause] -> [DClause] -> [DClause])
-> Name -> [DClause] -> Map Name [DClause] -> Map Name [DClause]
forall k a. Ord k => (a -> a -> a) -> k -> a -> Map k a -> Map k a
M.insertWith (\[DClause]
new [DClause]
old -> [DClause]
old [DClause] -> [DClause] -> [DClause]
forall a. [a] -> [a] -> [a]
++ [DClause]
new)
                                                Name
n [DClause]
clauses Map Name [DClause]
name_clause_map
             in if Name
n Name -> Map Name [DClause] -> Bool
forall k a. Ord k => k -> Map k a -> Bool
`M.member` Map Name [DClause]
name_clause_map
                then Map Name [DClause]
-> Set Name -> [DLetDec] -> (Map Name [DClause], [DLetDec])
gather_decs Map Name [DClause]
name_clause_map' Set Name
type_sig_names [DLetDec]
xs
                else let (Map Name [DClause]
map', [DLetDec]
decs') = Map Name [DClause]
-> Set Name -> [DLetDec] -> (Map Name [DClause], [DLetDec])
gather_decs Map Name [DClause]
name_clause_map'
                                           Set Name
type_sig_names [DLetDec]
xs
                      in (Map Name [DClause]
map', DLetDec
xDLetDec -> [DLetDec] -> [DLetDec]
forall a. a -> [a] -> [a]
:[DLetDec]
decs')

          -- 2.
          | DSigD Name
n DType
_ <- DLetDec
x
          = if Name
n Name -> Set Name -> Bool
forall a. Ord a => a -> Set a -> Bool
`S.member` Set Name
type_sig_names
            then Map Name [DClause]
-> Set Name -> [DLetDec] -> (Map Name [DClause], [DLetDec])
gather_decs Map Name [DClause]
name_clause_map Set Name
type_sig_names [DLetDec]
xs
            else let (Map Name [DClause]
map', [DLetDec]
decs') = Map Name [DClause]
-> Set Name -> [DLetDec] -> (Map Name [DClause], [DLetDec])
gather_decs Map Name [DClause]
name_clause_map
                                       (Name
n Name -> Set Name -> Set Name
forall a. Ord a => a -> Set a -> Set a
`S.insert` Set Name
type_sig_names) [DLetDec]
xs
                  in (Map Name [DClause]
map', DLetDec
xDLetDec -> [DLetDec] -> [DLetDec]
forall a. a -> [a] -> [a]
:[DLetDec]
decs')

          -- 3.
          | Bool
otherwise =
              let (Map Name [DClause]
map', [DLetDec]
decs') = Map Name [DClause]
-> Set Name -> [DLetDec] -> (Map Name [DClause], [DLetDec])
gather_decs Map Name [DClause]
name_clause_map Set Name
type_sig_names [DLetDec]
xs
               in (Map Name [DClause]
map', DLetDec
xDLetDec -> [DLetDec] -> [DLetDec]
forall a. a -> [a] -> [a]
:[DLetDec]
decs')

        augment_clauses :: M.Map Name [DClause] -> [DLetDec] -> [DLetDec]
        augment_clauses :: Map Name [DClause] -> [DLetDec] -> [DLetDec]
augment_clauses Map Name [DClause]
_ [] = []
        augment_clauses Map Name [DClause]
name_clause_map (DLetDec
x:[DLetDec]
xs)
          | DFunD Name
n [DClause]
_ <- DLetDec
x, Just [DClause]
merged_clauses <- Name
n Name -> Map Name [DClause] -> Maybe [DClause]
forall k a. Ord k => k -> Map k a -> Maybe a
`M.lookup` Map Name [DClause]
name_clause_map
          = Name -> [DClause] -> DLetDec
DFunD Name
n [DClause]
merged_clausesDLetDec -> [DLetDec] -> [DLetDec]
forall a. a -> [a] -> [a]
:Map Name [DClause] -> [DLetDec] -> [DLetDec]
augment_clauses Map Name [DClause]
name_clause_map [DLetDec]
xs
          | Bool
otherwise = DLetDec
xDLetDec -> [DLetDec] -> [DLetDec]
forall a. a -> [a] -> [a]
:Map Name [DClause] -> [DLetDec] -> [DLetDec]
augment_clauses Map Name [DClause]
name_clause_map [DLetDec]
xs

-- | Create new kind variable binder names corresponding to the return kind of
-- a data type. This is useful when you have a data type like:
--
-- @
-- data Foo :: forall k. k -> Type -> Type where ...
-- @
--
-- But you want to be able to refer to the type @Foo a b@.
-- 'mkExtraDKindBinders' will take the kind @forall k. k -> Type -> Type@,
-- discover that is has two visible argument kinds, and return as a result
-- two new kind variable binders @[a :: k, b :: Type]@, where @a@ and @b@
-- are fresh type variable names.
--
-- This expands kind synonyms if necessary.
mkExtraDKindBinders :: forall q. DsMonad q => DKind -> q [DTyVarBndrVis]
mkExtraDKindBinders :: forall (q :: * -> *). DsMonad q => DType -> q [DTyVarBndrVis]
mkExtraDKindBinders DType
k = do
  k' <- DType -> q DType
forall (q :: * -> *). DsMonad q => DType -> q DType
expandType DType
k
  let (fun_args, _) = unravelDType k'
      vis_fun_args  = DFunArgs -> [DVisFunArg]
filterDVisFunArgs DFunArgs
fun_args
  mapM mk_tvb vis_fun_args
  where
    mk_tvb :: DVisFunArg -> q (DTyVarBndrVis)
    mk_tvb :: DVisFunArg -> q DTyVarBndrVis
mk_tvb (DVisFADep DTyVarBndrUnit
tvb) = DTyVarBndrVis -> q DTyVarBndrVis
forall a. a -> q a
forall (m :: * -> *) a. Monad m => a -> m a
return (BndrVis
BndrReq BndrVis -> DTyVarBndrUnit -> DTyVarBndrVis
forall a b. a -> DTyVarBndr b -> DTyVarBndr a
forall (f :: * -> *) a b. Functor f => a -> f b -> f a
<$ DTyVarBndrUnit
tvb)
    mk_tvb (DVisFAAnon DType
ki) = do
      name <- String -> q Name
forall (q :: * -> *). Quasi q => String -> q Name
qNewName String
"a"
      pure $ DKindedTV name BndrReq ki

{- $localReification

@template-haskell@ reification functions like 'reify' and 'qReify', as well as
@th-desugar@'s 'reifyWithWarning', only look through declarations that either
(1) have already been typechecked in the current module, or (2) are in scope
because of imports. We refer to this as /global/ reification. Sometimes,
however, you may wish to reify declarations that have been quoted but not
yet been typechecked, such as in the following example:

@
example :: IO ()
example = putStrLn
  $(do decs <- [d| data Foo = MkFoo |]
       info <- 'reify' (mkName \"Foo\")
       stringE $ pprint info)
@

Because @Foo@ only exists in a TH quote, it is not available globally. As a
result, the call to @'reify' (mkName \"Foo\")@ will fail.

To make this sort of example possible, @th-desugar@ extends global reification
with /local/ reification. A function that performs local reification (such
as 'dsReify', 'reifyWithLocals', or similar functions that have a 'DsMonad'
context) looks through both typechecked (or imported) declarations /and/ quoted
declarations that are currently in scope. One can add quoted declarations in
the current scope by using the 'withLocalDeclarations' function. Here is an
example of how to repair the example above using 'withLocalDeclarations':

@
example2 :: IO ()
example2 = putStrLn
  $(do decs <- [d| data Foo = MkFoo |]
       info <- 'withLocalDeclarations' decs $
                 'reifyWithLocals' (mkName \"Foo\")
       stringE $ pprint info)
@

Note that 'withLocalDeclarations' should only be used to add quoted
declarations with names that are not duplicates of existing global or local
declarations. Adding duplicate declarations through 'withLocalDeclarations'
is undefined behavior and should be avoided. This is unlikely to happen if
you are only using 'withLocalDeclarations' in conjunction with TH quotes,
however. For instance, this is /not/ an example of duplicate declarations:

@
data T = MkT1

$(do decs <- [d| data T = MkT2 |]
     info <- 'withLocalDeclarations' decs ...
     ...)
@

The quoted @data T = MkT2@ does not conflict with the top-level @data T = Mk1@
since declaring a data type within TH quotes gives it a fresh, unique name that
distinguishes it from any other data types already in scope.
-}