lens-5.2.3: src/Control/Lens/Internal/TH.hs
{-# LANGUAGE CPP #-}
{-# LANGUAGE TemplateHaskellQuotes #-}
#ifdef TRUSTWORTHY
# if MIN_VERSION_template_haskell(2,12,0)
{-# LANGUAGE Safe #-}
# else
{-# LANGUAGE Trustworthy #-}
# endif
#endif
#include "lens-common.h"
-----------------------------------------------------------------------------
-- |
-- Module : Control.Lens.Internal.TH
-- Copyright : (C) 2013-2016 Edward Kmett and Eric Mertens
-- License : BSD-style (see the file LICENSE)
-- Maintainer : Edward Kmett <ekmett@gmail.com>
-- Stability : experimental
-- Portability : non-portable
--
----------------------------------------------------------------------------
module Control.Lens.Internal.TH
( module Control.Lens.Internal.TH
#if MIN_VERSION_template_haskell(2,21,0) || MIN_VERSION_th_abstraction(0,6,0)
, D.TyVarBndrVis
, D.bndrReq
#endif
) where
import Control.Lens.Iso
import Control.Lens.Prism
import Control.Lens.Review
import Control.Lens.Type
import Control.Lens.Wrapped
import Data.Functor.Contravariant
import qualified Data.Set as Set
import Data.Set (Set)
import Language.Haskell.TH
import qualified Language.Haskell.TH.Datatype as D
import qualified Language.Haskell.TH.Datatype.TyVarBndr as D
-- | Apply arguments to a type constructor
appsT :: TypeQ -> [TypeQ] -> TypeQ
appsT = foldl appT
-- | Apply arguments to a function
appsE1 :: ExpQ -> [ExpQ] -> ExpQ
appsE1 = foldl appE
-- | Construct a tuple type given a list of types.
toTupleT :: [TypeQ] -> TypeQ
toTupleT [x] = x
toTupleT xs = appsT (tupleT (length xs)) xs
-- | Construct a tuple value given a list of expressions.
toTupleE :: [ExpQ] -> ExpQ
toTupleE [x] = x
toTupleE xs = tupE xs
-- | Construct a tuple pattern given a list of patterns.
toTupleP :: [PatQ] -> PatQ
toTupleP [x] = x
toTupleP xs = tupP xs
-- | Apply arguments to a type constructor.
conAppsT :: Name -> [Type] -> Type
conAppsT conName = foldl AppT (ConT conName)
-- | Generate many new names from a given base name.
newNames :: String {- ^ base name -} -> Int {- ^ count -} -> Q [Name]
newNames base n = sequence [ newName (base++show i) | i <- [1..n] ]
-- | Decompose an applied type into its individual components. For example, this:
--
-- @
-- Either Int Char
-- @
--
-- would be unfolded to this:
--
-- @
-- ('ConT' ''Either, ['ConT' ''Int, 'ConT' ''Char])
-- @
--
-- This function ignores explicit parentheses and visible kind applications.
unfoldType :: Type -> (Type, [Type])
unfoldType = go []
where
go :: [Type] -> Type -> (Type, [Type])
go acc (ForallT _ _ ty) = go acc ty
go acc (AppT ty1 ty2) = go (ty2:acc) ty1
go acc (SigT ty _) = go acc ty
go acc (ParensT ty) = go acc ty
#if MIN_VERSION_template_haskell(2,15,0)
go acc (AppKindT ty _) = go acc ty
#endif
go acc ty = (ty, acc)
-- Construct a 'Type' using the datatype's type constructor and type
-- parameters. Unlike 'D.datatypeType', kind signatures are preserved to
-- some extent. (See the comments for 'dropSigsIfNonDataFam' below for more
-- details on this.)
datatypeTypeKinded :: D.DatatypeInfo -> Type
datatypeTypeKinded di
= foldl AppT (ConT (D.datatypeName di))
$ dropSigsIfNonDataFam di
$ D.datatypeInstTypes di
-- | In an effort to prevent users from having to enable KindSignatures every
-- time that they use lens' TH functionality, we strip off reified kind
-- annotations from when:
--
-- 1. The kind of a type does not contain any kind variables. If it *does*
-- contain kind variables, we want to preserve them so that we can generate
-- type signatures that preserve the dependency order of kind and type
-- variables. (The data types in test/T917.hs contain examples where this
-- is important.) This will require enabling `PolyKinds`, but since
-- `PolyKinds` implies `KindSignatures`, we can at least accomplish two
-- things at once.
-- 2. The data type is not an instance of a data family. We make an exception
-- for data family instances, since the presence or absence of a kind
-- annotation can be the difference between typechecking or not.
-- (See T917DataFam in tests/T917.hs for an example.) Moreover, the
-- `TypeFamilies` extension implies `KindSignatures`.
dropSigsIfNonDataFam :: D.DatatypeInfo -> [Type] -> [Type]
dropSigsIfNonDataFam di
| isDataFamily (D.datatypeVariant di) = id
| otherwise = map dropSig
where
dropSig :: Type -> Type
dropSig (SigT t k) | null (D.freeVariables k) = t
dropSig t = t
-- | Template Haskell wants type variables declared in a forall, so
-- we find all free type variables in a given type and declare them.
quantifyType :: Cxt -> Type -> Type
quantifyType = quantifyType' Set.empty
-- | This function works like 'quantifyType' except that it takes
-- a list of variables to exclude from quantification.
quantifyType' :: Set Name -> Cxt -> Type -> Type
quantifyType' exclude c t = ForallT vs c t
where
vs = filter (\tvb -> D.tvName tvb `Set.notMember` exclude)
$ D.changeTVFlags D.SpecifiedSpec
$ D.freeVariablesWellScoped (t:c) -- stable order
-- | Convert a 'TyVarBndr' into its corresponding 'Type'.
tvbToType :: D.TyVarBndr_ flag -> Type
tvbToType = D.elimTV VarT (SigT . VarT)
-- | Peel off a kind signature from a Type (if it has one).
unSigT :: Type -> Type
unSigT (SigT t _) = t
unSigT t = t
isDataFamily :: D.DatatypeVariant -> Bool
isDataFamily D.Datatype = False
isDataFamily D.Newtype = False
isDataFamily D.DataInstance = True
isDataFamily D.NewtypeInstance = True
#if MIN_VERSION_th_abstraction(0,5,0)
isDataFamily D.TypeData = False
#endif
#if !(MIN_VERSION_template_haskell(2,21,0)) && !(MIN_VERSION_th_abstraction(0,6,0))
type TyVarBndrVis = D.TyVarBndr_ ()
bndrReq :: ()
bndrReq = ()
#endif
------------------------------------------------------------------------
-- TH-quoted names
------------------------------------------------------------------------
-- Note that this module only TemplateHaskellQuotes, not TemplateHaskell,
-- which makes lens able to be used in stage1 cross-compilers.
traversalTypeName :: Name
traversalTypeName = ''Traversal
traversal'TypeName :: Name
traversal'TypeName = ''Traversal'
lensTypeName :: Name
lensTypeName = ''Lens
lens'TypeName :: Name
lens'TypeName = ''Lens'
isoTypeName :: Name
isoTypeName = ''Iso
iso'TypeName :: Name
iso'TypeName = ''Iso'
getterTypeName :: Name
getterTypeName = ''Getter
foldTypeName :: Name
foldTypeName = ''Fold
prismTypeName :: Name
prismTypeName = ''Prism
prism'TypeName :: Name
prism'TypeName = ''Prism'
reviewTypeName :: Name
reviewTypeName = ''Review
wrappedTypeName :: Name
wrappedTypeName = ''Wrapped
unwrappedTypeName :: Name
unwrappedTypeName = ''Unwrapped
rewrappedTypeName :: Name
rewrappedTypeName = ''Rewrapped
_wrapped'ValName :: Name
_wrapped'ValName = '_Wrapped'
isoValName :: Name
isoValName = 'iso
prismValName :: Name
prismValName = 'prism
untoValName :: Name
untoValName = 'unto
phantomValName :: Name
phantomValName = 'phantom2
phantom2 :: (Functor f, Contravariant f) => f a -> f b
phantom2 = phantom
{-# INLINE phantom2 #-}
composeValName :: Name
composeValName = '(.)
idValName :: Name
idValName = 'id
fmapValName :: Name
fmapValName = 'fmap
pureValName :: Name
pureValName = 'pure
apValName :: Name
apValName = '(<*>)
rightDataName :: Name
rightDataName = 'Right
leftDataName :: Name
leftDataName = 'Left
------------------------------------------------------------------------
-- Support for generating inline pragmas
------------------------------------------------------------------------
inlinePragma :: Name -> [DecQ]
inlinePragma methodName = [pragInlD methodName Inline FunLike AllPhases]