{-# LANGUAGE TemplateHaskell, CPP #-}
-- |
-- Module      : Test.LeanCheck.Derive
-- Copyright   : (c) 2015-2020 Rudy Matela
-- License     : 3-Clause BSD  (see the file LICENSE)
-- Maintainer  : Rudy Matela <rudy@matela.com.br>
--
-- This module is part of LeanCheck,
-- a simple enumerative property-based testing library.
--
-- Needs GHC and Template Haskell
-- (tested on GHC 7.4, 7.6, 7.8, 7.10, 8.0, 8.2, 8.4, 8.6 and 8.8).
--
-- If LeanCheck does not compile under later GHCs, this module is probably the
-- culprit.
--
-- If you rather do this through GHC Generics, please see:
-- "Test.LeanCheck.Generic" (experimental).
module Test.LeanCheck.Derive
  ( deriveListable
  , deriveListableIfNeeded
  , deriveListableCascading
  , deriveTiers
  , deriveList
  )
where

#ifdef __GLASGOW_HASKELL__

import Language.Haskell.TH
import Test.LeanCheck.Basic
import Control.Monad (unless, liftM, filterM)
import Data.List (delete)

#if __GLASGOW_HASKELL__ < 706
-- reportWarning was only introduced in GHC 7.6 / TH 2.8
reportWarning :: String -> Q ()
reportWarning  =  report False
#endif

-- | Derives a 'Listable' instance for a given type 'Name'.
--
-- Consider the following @Stack@ datatype:
--
-- > data Stack a  =  Stack a (Stack a) | Empty
--
-- Writing
--
-- > deriveListable ''Stack
--
-- will automatically derive the following 'Listable' instance:
--
-- > instance Listable a => Listable (Stack a) where
-- >   tiers  =  cons2 Stack \/ cons0 Empty
--
-- __Warning:__ if the values in your type need to follow a data invariant, the
--              derived instance won't respect it.  Use this only on "free"
--              datatypes.
--
-- Needs the @TemplateHaskell@ extension.
deriveListable :: Name -> DecsQ
deriveListable :: Name -> DecsQ
deriveListable  =  Bool -> Bool -> Name -> DecsQ
deriveListableX Bool
True Bool
False

-- | Same as 'deriveListable' but does not warn when the requested instance
--   already exists.  The function 'deriveListable' is preferable in most
--   situations.
deriveListableIfNeeded :: Name -> DecsQ
deriveListableIfNeeded :: Name -> DecsQ
deriveListableIfNeeded  =  Bool -> Bool -> Name -> DecsQ
deriveListableX Bool
False Bool
False

-- | Derives a 'Listable' instance for a given type 'Name'
--   cascading derivation of type arguments as well.
--
-- Consider the following series of datatypes:
--
-- > data Position  =  CEO | Manager | Programmer
-- >
-- > data Person  =  Person
-- >              {  name :: String
-- >              ,  age :: Int
-- >              ,  position :: Position
-- >              }
-- >
-- > data Company  =  Company
-- >               {  name :: String
-- >               ,  employees :: [Person]
-- >               }
--
-- Writing
--
-- > deriveListableCascading ''Company
--
-- will automatically derive the following three 'Listable' instances:
--
-- > instance Listable Position where
-- >   tiers  =  cons0 CEO \/ cons0 Manager \/ cons0 Programmer
-- >
-- > instance Listable Person where
-- >   tiers  =  cons3 Person
-- >
-- > instance Listable Company where
-- >   tiers  =  cons2 Company
deriveListableCascading :: Name -> DecsQ
deriveListableCascading :: Name -> DecsQ
deriveListableCascading  =  Bool -> Bool -> Name -> DecsQ
deriveListableX Bool
True Bool
True

deriveListableX :: Bool -> Bool -> Name -> DecsQ
deriveListableX :: Bool -> Bool -> Name -> DecsQ
deriveListableX Bool
warnExisting Bool
cascade Name
t  =  do
  Bool
is <- Name
t Name -> Name -> Q Bool
`isInstanceOf` ''Listable
  if Bool
is
    then do
      Bool -> Q () -> Q ()
forall (f :: * -> *). Applicative f => Bool -> f () -> f ()
unless (Bool -> Bool
not Bool
warnExisting)
        (String -> Q ()
reportWarning (String -> Q ()) -> String -> Q ()
forall a b. (a -> b) -> a -> b
$ String
"Instance Listable " String -> String -> String
forall a. [a] -> [a] -> [a]
++ Name -> String
forall a. Show a => a -> String
show Name
t
                      String -> String -> String
forall a. [a] -> [a] -> [a]
++ String
" already exists, skipping derivation")
      [Dec] -> DecsQ
forall (m :: * -> *) a. Monad m => a -> m a
return []
    else if Bool
cascade
           then Name -> DecsQ
reallyDeriveListableCascading Name
t
           else Name -> DecsQ
reallyDeriveListable Name
t

reallyDeriveListable :: Name -> DecsQ
reallyDeriveListable :: Name -> DecsQ
reallyDeriveListable Name
t  =  do
  (Type
nt,[Type]
vs) <- Name -> Q (Type, [Type])
normalizeType Name
t
#if __GLASGOW_HASKELL__ >= 710
  [Type]
cxt <- [Q Type] -> Q [Type]
forall (t :: * -> *) (m :: * -> *) a.
(Traversable t, Monad m) =>
t (m a) -> m (t a)
sequence [[t| Listable $(return v) |] | Type
v <- [Type]
vs]
#else
  cxt <- sequence [classP ''Listable [return v] | v <- vs]
#endif
#if __GLASGOW_HASKELL__ >= 708
  [Type]
cxt [Type] -> DecsQ -> DecsQ
|=>| [d| instance Listable $(return nt)
                 where tiers  =  $(deriveTiers t) |]
#else
  tiersE <- deriveTiers t
  return [ InstanceD
             cxt
             (AppT (ConT ''Listable) nt)
             [ValD (VarP 'tiers) (NormalB tiersE) []]
         ]
#endif

-- | Given a type 'Name', derives an expression to be placed as the result of
--   'tiers':
--
-- > consN C1 \/ consN C2 \/ ... \/ consN CN
--
-- This function can be used in the definition of 'Listable' instances:
--
-- > instance Listable MyType where
-- >   tiers  =  $(deriveTiers)
deriveTiers :: Name -> ExpQ
deriveTiers :: Name -> ExpQ
deriveTiers Name
t  =  [(Name, [Type])] -> ExpQ
forall a. [(Name, [a])] -> ExpQ
conse ([(Name, [Type])] -> ExpQ) -> Q [(Name, [Type])] -> ExpQ
forall (m :: * -> *) a b. Monad m => (a -> m b) -> m a -> m b
=<< Name -> Q [(Name, [Type])]
typeConstructors Name
t
  where
  cone :: Name -> t a -> ExpQ
cone Name
n t a
as  =  do
    (Just Name
consN) <- String -> Q (Maybe Name)
lookupValueName (String -> Q (Maybe Name)) -> String -> Q (Maybe Name)
forall a b. (a -> b) -> a -> b
$ String
"cons" String -> String -> String
forall a. [a] -> [a] -> [a]
++ Int -> String
forall a. Show a => a -> String
show (t a -> Int
forall (t :: * -> *) a. Foldable t => t a -> Int
length t a
as)
    [| $(varE consN) $(conE n) |]
  conse :: [(Name, [a])] -> ExpQ
conse  =  (ExpQ -> ExpQ -> ExpQ) -> [ExpQ] -> ExpQ
forall (t :: * -> *) a. Foldable t => (a -> a -> a) -> t a -> a
foldr1 (\ExpQ
e1 ExpQ
e2 -> [| $e1 \/ $e2 |]) ([ExpQ] -> ExpQ)
-> ([(Name, [a])] -> [ExpQ]) -> [(Name, [a])] -> ExpQ
forall b c a. (b -> c) -> (a -> b) -> a -> c
. ((Name, [a]) -> ExpQ) -> [(Name, [a])] -> [ExpQ]
forall a b. (a -> b) -> [a] -> [b]
map ((Name -> [a] -> ExpQ) -> (Name, [a]) -> ExpQ
forall a b c. (a -> b -> c) -> (a, b) -> c
uncurry Name -> [a] -> ExpQ
forall (t :: * -> *) a. Foldable t => Name -> t a -> ExpQ
cone)

-- | Given a type 'Name', derives an expression to be placed as the result of
--   'list':
--
-- > concat $ consN C1 \/ consN C2 \/ ... \/ consN CN
deriveList :: Name -> ExpQ
deriveList :: Name -> ExpQ
deriveList Name
t  =  [| concat $(deriveTiers t) |]

-- Not only really derive Listable instances,
-- but cascade through argument types.
reallyDeriveListableCascading :: Name -> DecsQ
reallyDeriveListableCascading :: Name -> DecsQ
reallyDeriveListableCascading Name
t =
      [Dec] -> DecsQ
forall (m :: * -> *) a. Monad m => a -> m a
return ([Dec] -> DecsQ) -> ([[Dec]] -> [Dec]) -> [[Dec]] -> DecsQ
forall b c a. (b -> c) -> (a -> b) -> a -> c
. [[Dec]] -> [Dec]
forall (t :: * -> *) a. Foldable t => t [a] -> [a]
concat
  ([[Dec]] -> DecsQ) -> Q [[Dec]] -> DecsQ
forall (m :: * -> *) a b. Monad m => (a -> m b) -> m a -> m b
=<< (Name -> DecsQ) -> [Name] -> Q [[Dec]]
forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
mapM Name -> DecsQ
reallyDeriveListable
  ([Name] -> Q [[Dec]]) -> Q [Name] -> Q [[Dec]]
forall (m :: * -> *) a b. Monad m => (a -> m b) -> m a -> m b
=<< (Name -> Q Bool) -> [Name] -> Q [Name]
forall (m :: * -> *) a.
Applicative m =>
(a -> m Bool) -> [a] -> m [a]
filterM ((Bool -> Bool) -> Q Bool -> Q Bool
forall (m :: * -> *) a1 r. Monad m => (a1 -> r) -> m a1 -> m r
liftM Bool -> Bool
not (Q Bool -> Q Bool) -> (Name -> Q Bool) -> Name -> Q Bool
forall b c a. (b -> c) -> (a -> b) -> a -> c
. Name -> Q Bool
isTypeSynonym)
  ([Name] -> Q [Name]) -> Q [Name] -> Q [Name]
forall (m :: * -> *) a b. Monad m => (a -> m b) -> m a -> m b
=<< [Name] -> Q [Name]
forall (m :: * -> *) a. Monad m => a -> m a
return ([Name] -> Q [Name]) -> ([Name] -> [Name]) -> [Name] -> Q [Name]
forall b c a. (b -> c) -> (a -> b) -> a -> c
. (Name
tName -> [Name] -> [Name]
forall a. a -> [a] -> [a]
:) ([Name] -> [Name]) -> ([Name] -> [Name]) -> [Name] -> [Name]
forall b c a. (b -> c) -> (a -> b) -> a -> c
. Name -> [Name] -> [Name]
forall a. Eq a => a -> [a] -> [a]
delete Name
t
  ([Name] -> Q [Name]) -> Q [Name] -> Q [Name]
forall (m :: * -> *) a b. Monad m => (a -> m b) -> m a -> m b
=<< Name
t Name -> (Name -> Q Bool) -> Q [Name]
`typeConCascadingArgsThat` (Name -> Name -> Q Bool
`isntInstanceOf` ''Listable)

-- * Template haskell utilities

typeConArgs :: Name -> Q [Name]
typeConArgs :: Name -> Q [Name]
typeConArgs Name
t  =  do
  Bool
is <- Name -> Q Bool
isTypeSynonym Name
t
  if Bool
is
  then (Type -> [Name]) -> Q Type -> Q [Name]
forall (m :: * -> *) a1 r. Monad m => (a1 -> r) -> m a1 -> m r
liftM Type -> [Name]
typeConTs (Q Type -> Q [Name]) -> Q Type -> Q [Name]
forall a b. (a -> b) -> a -> b
$ Name -> Q Type
typeSynonymType Name
t
  else ([(Name, [Type])] -> [Name]) -> Q [(Name, [Type])] -> Q [Name]
forall (m :: * -> *) a1 r. Monad m => (a1 -> r) -> m a1 -> m r
liftM ([[Name]] -> [Name]
forall a. Ord a => [[a]] -> [a]
nubMerges ([[Name]] -> [Name])
-> ([(Name, [Type])] -> [[Name]]) -> [(Name, [Type])] -> [Name]
forall b c a. (b -> c) -> (a -> b) -> a -> c
. (Type -> [Name]) -> [Type] -> [[Name]]
forall a b. (a -> b) -> [a] -> [b]
map Type -> [Name]
typeConTs ([Type] -> [[Name]])
-> ([(Name, [Type])] -> [Type]) -> [(Name, [Type])] -> [[Name]]
forall b c a. (b -> c) -> (a -> b) -> a -> c
. [[Type]] -> [Type]
forall (t :: * -> *) a. Foldable t => t [a] -> [a]
concat ([[Type]] -> [Type])
-> ([(Name, [Type])] -> [[Type]]) -> [(Name, [Type])] -> [Type]
forall b c a. (b -> c) -> (a -> b) -> a -> c
. ((Name, [Type]) -> [Type]) -> [(Name, [Type])] -> [[Type]]
forall a b. (a -> b) -> [a] -> [b]
map (Name, [Type]) -> [Type]
forall a b. (a, b) -> b
snd) (Q [(Name, [Type])] -> Q [Name]) -> Q [(Name, [Type])] -> Q [Name]
forall a b. (a -> b) -> a -> b
$ Name -> Q [(Name, [Type])]
typeConstructors Name
t
  where
  typeConTs :: Type -> [Name]
  typeConTs :: Type -> [Name]
typeConTs (AppT Type
t1 Type
t2)  =  Type -> [Name]
typeConTs Type
t1 [Name] -> [Name] -> [Name]
forall a. Ord a => [a] -> [a] -> [a]
`nubMerge` Type -> [Name]
typeConTs Type
t2
  typeConTs (SigT Type
t Type
_)  =  Type -> [Name]
typeConTs Type
t
  typeConTs (VarT Name
_)  =  []
  typeConTs (ConT Name
n)  =  [Name
n]
#if __GLASGOW_HASKELL__ >= 800
  -- typeConTs (PromotedT n)  =  [n] ?
  typeConTs (InfixT  Type
t1 Name
n Type
t2)  =  Type -> [Name]
typeConTs Type
t1 [Name] -> [Name] -> [Name]
forall a. Ord a => [a] -> [a] -> [a]
`nubMerge` Type -> [Name]
typeConTs Type
t2
  typeConTs (UInfixT Type
t1 Name
n Type
t2)  =  Type -> [Name]
typeConTs Type
t1 [Name] -> [Name] -> [Name]
forall a. Ord a => [a] -> [a] -> [a]
`nubMerge` Type -> [Name]
typeConTs Type
t2
  typeConTs (ParensT Type
t)  =  Type -> [Name]
typeConTs Type
t
#endif
  typeConTs Type
_  =  []

typeConArgsThat :: Name -> (Name -> Q Bool) -> Q [Name]
typeConArgsThat :: Name -> (Name -> Q Bool) -> Q [Name]
typeConArgsThat Name
t Name -> Q Bool
p  =  do
  [Name]
targs <- Name -> Q [Name]
typeConArgs Name
t
  [(Name, Bool)]
tbs   <- (Name -> Q (Name, Bool)) -> [Name] -> Q [(Name, Bool)]
forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
mapM (\Name
t' -> do Bool
is <- Name -> Q Bool
p Name
t'; (Name, Bool) -> Q (Name, Bool)
forall (m :: * -> *) a. Monad m => a -> m a
return (Name
t',Bool
is)) [Name]
targs
  [Name] -> Q [Name]
forall (m :: * -> *) a. Monad m => a -> m a
return [Name
t' | (Name
t',Bool
p) <- [(Name, Bool)]
tbs, Bool
p]

typeConCascadingArgsThat :: Name -> (Name -> Q Bool) -> Q [Name]
Name
t typeConCascadingArgsThat :: Name -> (Name -> Q Bool) -> Q [Name]
`typeConCascadingArgsThat` Name -> Q Bool
p  =  do
  [Name]
ts <- Name
t Name -> (Name -> Q Bool) -> Q [Name]
`typeConArgsThat` Name -> Q Bool
p
  let p' :: Name -> Q Bool
p' Name
t'  =  do Bool
is <- Name -> Q Bool
p Name
t'; Bool -> Q Bool
forall (m :: * -> *) a. Monad m => a -> m a
return (Bool -> Q Bool) -> Bool -> Q Bool
forall a b. (a -> b) -> a -> b
$ Name
t' Name -> [Name] -> Bool
forall (t :: * -> *) a. (Foldable t, Eq a) => a -> t a -> Bool
`notElem` (Name
tName -> [Name] -> [Name]
forall a. a -> [a] -> [a]
:[Name]
ts) Bool -> Bool -> Bool
&& Bool
is
  [[Name]]
tss <- (Name -> Q [Name]) -> [Name] -> Q [[Name]]
forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
mapM (Name -> (Name -> Q Bool) -> Q [Name]
`typeConCascadingArgsThat` Name -> Q Bool
p') [Name]
ts
  [Name] -> Q [Name]
forall (m :: * -> *) a. Monad m => a -> m a
return ([Name] -> Q [Name]) -> [Name] -> Q [Name]
forall a b. (a -> b) -> a -> b
$ [[Name]] -> [Name]
forall a. Ord a => [[a]] -> [a]
nubMerges ([Name]
ts[Name] -> [[Name]] -> [[Name]]
forall a. a -> [a] -> [a]
:[[Name]]
tss)

-- Normalizes a type by applying it to necessary type variables, making it
-- accept "zero" parameters.  The normalized type is tupled with a list of
-- necessary type variables.
--
-- Suppose:
--
-- > data DT a b c ...  =  ...
--
-- Then, in pseudo-TH:
--
-- > normalizeType [t|DT|] == Q (DT a b c ..., [a, b, c, ...])
normalizeType :: Name -> Q (Type, [Type])
normalizeType :: Name -> Q (Type, [Type])
normalizeType Name
t  =  do
  Int
ar <- Name -> Q Int
typeArity Name
t
  [Type]
vs <- Int -> Q [Type]
newVarTs Int
ar
  (Type, [Type]) -> Q (Type, [Type])
forall (m :: * -> *) a. Monad m => a -> m a
return ((Type -> Type -> Type) -> Type -> [Type] -> Type
forall (t :: * -> *) b a.
Foldable t =>
(b -> a -> b) -> b -> t a -> b
foldl Type -> Type -> Type
AppT (Name -> Type
ConT Name
t) [Type]
vs, [Type]
vs)
  where
    newNames :: [String] -> Q [Name]
    newNames :: [String] -> Q [Name]
newNames  =  (String -> Q Name) -> [String] -> Q [Name]
forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
mapM String -> Q Name
newName
    newVarTs :: Int -> Q [Type]
    newVarTs :: Int -> Q [Type]
newVarTs Int
n  =  ([Name] -> [Type]) -> Q [Name] -> Q [Type]
forall (m :: * -> *) a1 r. Monad m => (a1 -> r) -> m a1 -> m r
liftM ((Name -> Type) -> [Name] -> [Type]
forall a b. (a -> b) -> [a] -> [b]
map Name -> Type
VarT)
                (Q [Name] -> Q [Type]) -> Q [Name] -> Q [Type]
forall a b. (a -> b) -> a -> b
$  [String] -> Q [Name]
newNames (Int -> [String] -> [String]
forall a. Int -> [a] -> [a]
take Int
n ([String] -> [String])
-> (String -> [String]) -> String -> [String]
forall b c a. (b -> c) -> (a -> b) -> a -> c
. (Char -> String) -> String -> [String]
forall a b. (a -> b) -> [a] -> [b]
map (Char -> String -> String
forall a. a -> [a] -> [a]
:[]) (String -> [String]) -> String -> [String]
forall a b. (a -> b) -> a -> b
$ String -> String
forall a. [a] -> [a]
cycle [Char
'a'..Char
'z'])

-- Normalizes a type by applying it to units (`()`) while possible.
--
-- > normalizeTypeUnits ''Int    === [t| Int |]
-- > normalizeTypeUnits ''Maybe  === [t| Maybe () |]
-- > normalizeTypeUnits ''Either === [t| Either () () |]
normalizeTypeUnits :: Name -> Q Type
normalizeTypeUnits :: Name -> Q Type
normalizeTypeUnits Name
t  =  do
  Int
ar <- Name -> Q Int
typeArity Name
t
  Type -> Q Type
forall (m :: * -> *) a. Monad m => a -> m a
return ((Type -> Type -> Type) -> Type -> [Type] -> Type
forall (t :: * -> *) b a.
Foldable t =>
(b -> a -> b) -> b -> t a -> b
foldl Type -> Type -> Type
AppT (Name -> Type
ConT Name
t) (Int -> Type -> [Type]
forall a. Int -> a -> [a]
replicate Int
ar (Int -> Type
TupleT Int
0)))

-- Given a type name and a class name,
-- returns whether the type is an instance of that class.
isInstanceOf :: Name -> Name -> Q Bool
isInstanceOf :: Name -> Name -> Q Bool
isInstanceOf Name
tn Name
cl  =  do
  Type
ty <- Name -> Q Type
normalizeTypeUnits Name
tn
  Name -> [Type] -> Q Bool
isInstance Name
cl [Type
ty]

isntInstanceOf :: Name -> Name -> Q Bool
isntInstanceOf :: Name -> Name -> Q Bool
isntInstanceOf Name
tn Name
cl  =  (Bool -> Bool) -> Q Bool -> Q Bool
forall (m :: * -> *) a1 r. Monad m => (a1 -> r) -> m a1 -> m r
liftM Bool -> Bool
not (Name -> Name -> Q Bool
isInstanceOf Name
tn Name
cl)

-- | Given a type name, return the number of arguments taken by that type.
-- Examples in partially broken TH:
--
-- > arity ''Int        === Q 0
-- > arity ''Int->Int   === Q 0
-- > arity ''Maybe      === Q 1
-- > arity ''Either     === Q 2
-- > arity ''Int->      === Q 1
--
-- This works for Data's and Newtype's and it is useful when generating
-- typeclass instances.
typeArity :: Name -> Q Int
typeArity :: Name -> Q Int
typeArity Name
t  =  do
  Info
ti <- Name -> Q Info
reify Name
t
  Int -> Q Int
forall (m :: * -> *) a. Monad m => a -> m a
return (Int -> Q Int) -> ([TyVarBndr] -> Int) -> [TyVarBndr] -> Q Int
forall b c a. (b -> c) -> (a -> b) -> a -> c
. [TyVarBndr] -> Int
forall (t :: * -> *) a. Foldable t => t a -> Int
length ([TyVarBndr] -> Q Int) -> [TyVarBndr] -> Q Int
forall a b. (a -> b) -> a -> b
$ case Info
ti of
#if __GLASGOW_HASKELL__ < 800
    TyConI (DataD    _ _ ks _ _) -> ks
    TyConI (NewtypeD _ _ ks _ _) -> ks
#else
    TyConI (DataD    [Type]
_ Name
_ [TyVarBndr]
ks Maybe Type
_ [Con]
_ [DerivClause]
_) -> [TyVarBndr]
ks
    TyConI (NewtypeD [Type]
_ Name
_ [TyVarBndr]
ks Maybe Type
_ Con
_ [DerivClause]
_) -> [TyVarBndr]
ks
#endif
    TyConI (TySynD Name
_ [TyVarBndr]
ks Type
_) -> [TyVarBndr]
ks
    Info
_ -> String -> [TyVarBndr]
forall a. HasCallStack => String -> a
error (String -> [TyVarBndr]) -> String -> [TyVarBndr]
forall a b. (a -> b) -> a -> b
$ String
"error (typeArity): symbol " String -> String -> String
forall a. [a] -> [a] -> [a]
++ Name -> String
forall a. Show a => a -> String
show Name
t
              String -> String -> String
forall a. [a] -> [a] -> [a]
++ String
" is not a newtype, data or type synonym"

-- Given a type name, returns a list of its type constructor names paired with
-- the type arguments they take.
--
-- > typeConstructors ''()  =  Q [('(),[])]
--
-- > typeConstructors ''(,)  =  Q [('(,),[VarT a, VarT b])]
--
-- > typeConstructors ''[]  =  Q [('[],[]),('(:),[VarT a,AppT ListT (VarT a)])]
--
-- > data Pair a  =  P a a
-- > typeConstructors ''Pair  =  Q [('P,[VarT a, VarT a])]
--
-- > data Point  =  Pt Int Int
-- > typeConstructors ''Point  =  Q [('Pt,[ConT Int, ConT Int])]
typeConstructors :: Name -> Q [(Name,[Type])]
typeConstructors :: Name -> Q [(Name, [Type])]
typeConstructors Name
t  =  do
  Info
ti <- Name -> Q Info
reify Name
t
  [(Name, [Type])] -> Q [(Name, [Type])]
forall (m :: * -> *) a. Monad m => a -> m a
return ([(Name, [Type])] -> Q [(Name, [Type])])
-> ([Con] -> [(Name, [Type])]) -> [Con] -> Q [(Name, [Type])]
forall b c a. (b -> c) -> (a -> b) -> a -> c
. (Con -> (Name, [Type])) -> [Con] -> [(Name, [Type])]
forall a b. (a -> b) -> [a] -> [b]
map Con -> (Name, [Type])
simplify ([Con] -> Q [(Name, [Type])]) -> [Con] -> Q [(Name, [Type])]
forall a b. (a -> b) -> a -> b
$ case Info
ti of
#if __GLASGOW_HASKELL__ < 800
    TyConI (DataD    _ _ _ cs _) -> cs
    TyConI (NewtypeD _ _ _ c  _) -> [c]
#else
    TyConI (DataD    [Type]
_ Name
_ [TyVarBndr]
_ Maybe Type
_ [Con]
cs [DerivClause]
_) -> [Con]
cs
    TyConI (NewtypeD [Type]
_ Name
_ [TyVarBndr]
_ Maybe Type
_ Con
c  [DerivClause]
_) -> [Con
c]
#endif
    Info
_ -> String -> [Con]
forall a. HasCallStack => String -> a
error (String -> [Con]) -> String -> [Con]
forall a b. (a -> b) -> a -> b
$ String
"error (typeConstructors): symbol " String -> String -> String
forall a. [a] -> [a] -> [a]
++ Name -> String
forall a. Show a => a -> String
show Name
t
              String -> String -> String
forall a. [a] -> [a] -> [a]
++ String
" is neither newtype nor data"
  where
  simplify :: Con -> (Name, [Type])
simplify (NormalC Name
n [BangType]
ts)   =  (Name
n,(BangType -> Type) -> [BangType] -> [Type]
forall a b. (a -> b) -> [a] -> [b]
map BangType -> Type
forall a b. (a, b) -> b
snd [BangType]
ts)
  simplify (RecC    Name
n [VarBangType]
ts)   =  (Name
n,(VarBangType -> Type) -> [VarBangType] -> [Type]
forall a b. (a -> b) -> [a] -> [b]
map VarBangType -> Type
forall a b c. (a, b, c) -> c
trd [VarBangType]
ts)
  simplify (InfixC  BangType
t1 Name
n BangType
t2)  =  (Name
n,[BangType -> Type
forall a b. (a, b) -> b
snd BangType
t1,BangType -> Type
forall a b. (a, b) -> b
snd BangType
t2])
  simplify Con
_  =  String -> (Name, [Type])
forall a. HasCallStack => String -> a
error String
"typeConstructors: unexpected unhandled case"
  trd :: (a, b, c) -> c
trd (a
x,b
y,c
z)  =  c
z

isTypeSynonym :: Name -> Q Bool
isTypeSynonym :: Name -> Q Bool
isTypeSynonym Name
t  =  do
  Info
ti <- Name -> Q Info
reify Name
t
  Bool -> Q Bool
forall (m :: * -> *) a. Monad m => a -> m a
return (Bool -> Q Bool) -> Bool -> Q Bool
forall a b. (a -> b) -> a -> b
$ case Info
ti of
    TyConI (TySynD Name
_ [TyVarBndr]
_ Type
_) -> Bool
True
    Info
_                     -> Bool
False

typeSynonymType :: Name -> Q Type
typeSynonymType :: Name -> Q Type
typeSynonymType Name
t  =  do
  Info
ti <- Name -> Q Info
reify Name
t
  Type -> Q Type
forall (m :: * -> *) a. Monad m => a -> m a
return (Type -> Q Type) -> Type -> Q Type
forall a b. (a -> b) -> a -> b
$ case Info
ti of
    TyConI (TySynD Name
_ [TyVarBndr]
_ Type
t') -> Type
t'
    Info
_ -> String -> Type
forall a. HasCallStack => String -> a
error (String -> Type) -> String -> Type
forall a b. (a -> b) -> a -> b
$ String
"error (typeSynonymType): symbol " String -> String -> String
forall a. [a] -> [a] -> [a]
++ Name -> String
forall a. Show a => a -> String
show Name
t
              String -> String -> String
forall a. [a] -> [a] -> [a]
++ String
" is not a type synonym"

-- Append to instance contexts in a declaration.
--
-- > sequence [[|Eq b|],[|Eq c|]] |=>| [t|instance Eq a => Cl (Ty a) where f=g|]
-- > == [t| instance (Eq a, Eq b, Eq c) => Cl (Ty a) where f  =  g |]
(|=>|) :: Cxt -> DecsQ -> DecsQ
[Type]
c |=>| :: [Type] -> DecsQ -> DecsQ
|=>| DecsQ
qds  =  do [Dec]
ds <- DecsQ
qds
                  [Dec] -> DecsQ
forall (m :: * -> *) a. Monad m => a -> m a
return ([Dec] -> DecsQ) -> [Dec] -> DecsQ
forall a b. (a -> b) -> a -> b
$ (Dec -> Dec) -> [Dec] -> [Dec]
forall a b. (a -> b) -> [a] -> [b]
map (Dec -> [Type] -> Dec
`ac` [Type]
c) [Dec]
ds
#if __GLASGOW_HASKELL__ < 800
  where ac (InstanceD c ts ds) c'  =  InstanceD (c++c') ts ds
        ac d                   _   =  d
#else
  where ac :: Dec -> [Type] -> Dec
ac (InstanceD Maybe Overlap
o [Type]
c Type
ts [Dec]
ds) [Type]
c'  =  Maybe Overlap -> [Type] -> Type -> [Dec] -> Dec
InstanceD Maybe Overlap
o ([Type]
c[Type] -> [Type] -> [Type]
forall a. [a] -> [a] -> [a]
++[Type]
c') Type
ts [Dec]
ds
        ac Dec
d                     [Type]
_   =  Dec
d
#endif

-- > nubMerge xs ys == nub (merge xs ys)
-- > nubMerge xs ys == nub (sort (xs ++ ys))
nubMerge :: Ord a => [a] -> [a] -> [a]
nubMerge :: [a] -> [a] -> [a]
nubMerge [] [a]
ys  =  [a]
ys
nubMerge [a]
xs []  =  [a]
xs
nubMerge (a
x:[a]
xs) (a
y:[a]
ys) | a
x a -> a -> Bool
forall a. Ord a => a -> a -> Bool
< a
y      =  a
x a -> [a] -> [a]
forall a. a -> [a] -> [a]
:    [a]
xs  [a] -> [a] -> [a]
forall a. Ord a => [a] -> [a] -> [a]
`nubMerge` (a
ya -> [a] -> [a]
forall a. a -> [a] -> [a]
:[a]
ys)
                       | a
x a -> a -> Bool
forall a. Ord a => a -> a -> Bool
> a
y      =  a
y a -> [a] -> [a]
forall a. a -> [a] -> [a]
: (a
xa -> [a] -> [a]
forall a. a -> [a] -> [a]
:[a]
xs) [a] -> [a] -> [a]
forall a. Ord a => [a] -> [a] -> [a]
`nubMerge`    [a]
ys
                       | Bool
otherwise  =  a
x a -> [a] -> [a]
forall a. a -> [a] -> [a]
:    [a]
xs  [a] -> [a] -> [a]
forall a. Ord a => [a] -> [a] -> [a]
`nubMerge`    [a]
ys

nubMerges :: Ord a => [[a]] -> [a]
nubMerges :: [[a]] -> [a]
nubMerges  =  ([a] -> [a] -> [a]) -> [a] -> [[a]] -> [a]
forall (t :: * -> *) a b.
Foldable t =>
(a -> b -> b) -> b -> t a -> b
foldr [a] -> [a] -> [a]
forall a. Ord a => [a] -> [a] -> [a]
nubMerge []

#else
-- When using Hugs or other compiler without Template Haskell

errorNotGHC :: a
errorNotGHC  =  error "Only defined when using GHC"

deriveListable :: a
deriveListable  =  errorNotGHC

deriveListableIfNeeded :: a
deriveListableIfNeeded  =  errorNotGHC

deriveListableCascading :: a
deriveListableCascading  =  errorNotGHC

deriveTiers :: a
deriveTiers  =  errorNotGHC

deriveList :: a
deriveList  =  errorNotGHC

-- closing #ifdef __GLASGOW_HASKELL__
#endif