summaryrefslogtreecommitdiff
path: root/libraries/base
diff options
context:
space:
mode:
authorBen Gamari <bgamari.foss@gmail.com>2015-10-30 20:22:42 +0100
committerBen Gamari <ben@smart-cactus.org>2015-10-30 20:22:44 +0100
commit91c6b1f54aea658b0056caec45655475897f1972 (patch)
treeaeb80a04e102e51dfd41343d4f697baf34c95739 /libraries/base
parent59e728bc0b47116e3c9a8b21b14dc3198531b9a9 (diff)
downloadhaskell-91c6b1f54aea658b0056caec45655475897f1972.tar.gz
Generate Typeable info at definition sites
This is the second attempt at merging D757. This patch implements the idea floated in Trac #9858, namely that we should generate type-representation information at the data type declaration site, rather than when solving a Typeable constraint. However, this turned out quite a bit harder than I expected. I still think it's the right thing to do, and it's done now, but it was quite a struggle. See particularly * Note [Grand plan for Typeable] in TcTypeable (which is a new module) * Note [The overall promotion story] in DataCon (clarifies existing stuff) The most painful bit was that to generate Typeable instances (ie TyConRepName bindings) for every TyCon is tricky for types in ghc-prim etc: * We need to have enough data types around to *define* a TyCon * Many of these types are wired-in Also, to minimise the code generated for each data type, I wanted to generate pure data, not CAFs with unpackCString# stuff floating about. Performance ~~~~~~~~~~~ Three perf/compiler tests start to allocate quite a bit more. This isn't surprising, because they all allocate zillions of data types, with practically no other code, esp. T1969 * T1969: GHC allocates 19% more * T4801: GHC allocates 13% more * T5321FD: GHC allocates 13% more * T9675: GHC allocates 11% more * T783: GHC allocates 11% more * T5642: GHC allocates 10% more I'm treating this as acceptable. The payoff comes in Typeable-heavy code. Remaining to do ~~~~~~~~~~~~~~~ * I think that "TyCon" and "Module" are over-generic names to use for the runtime type representations used in GHC.Typeable. Better might be "TrTyCon" and "TrModule". But I have not yet done this * Add more info the the "TyCon" e.g. source location where it was defined * Use the new "Module" type to help with Trac Trac #10068 * It would be possible to generate TyConRepName (ie Typeable instances) selectively rather than all the time. We'd need to persist the information in interface files. Lacking a motivating reason I have not done this, but it would not be difficult. Refactoring ~~~~~~~~~~~ As is so often the case, I ended up refactoring more than I intended. In particular * In TyCon, a type *family* (whether type or data) is repesented by a FamilyTyCon * a algebraic data type (including data/newtype instances) is represented by AlgTyCon This wasn't true before; a data family was represented as an AlgTyCon. There are some corresponding changes in IfaceSyn. * Also get rid of the (unhelpfully named) tyConParent. * In TyCon define 'Promoted', isomorphic to Maybe, used when things are optionally promoted; and use it elsewhere in GHC. * Cleanup handling of knownKeyNames * Each TyCon, including promoted TyCons, contains its TyConRepName, if it has one. This is, in effect, the name of its Typeable instance. Updates haddock submodule Test Plan: Let Harbormaster validate Reviewers: austin, hvr, goldfire Subscribers: goldfire, thomie Differential Revision: https://phabricator.haskell.org/D1404 GHC Trac Issues: #9858
Diffstat (limited to 'libraries/base')
-rw-r--r--libraries/base/Data/Typeable.hs5
-rw-r--r--libraries/base/Data/Typeable/Internal.hs330
-rw-r--r--libraries/base/GHC/Show.hs10
-rw-r--r--libraries/base/GHC/Stack/Types.hs13
4 files changed, 245 insertions, 113 deletions
diff --git a/libraries/base/Data/Typeable.hs b/libraries/base/Data/Typeable.hs
index c30a43dd65..1afc6a9563 100644
--- a/libraries/base/Data/Typeable.hs
+++ b/libraries/base/Data/Typeable.hs
@@ -58,7 +58,7 @@ module Data.Typeable
-- * A canonical proxy type
Proxy (..),
-
+
-- * Type representations
TypeRep, -- abstract, instance of: Eq, Show, Typeable
typeRepFingerprint,
@@ -66,6 +66,7 @@ module Data.Typeable
showsTypeRep,
TyCon, -- abstract, instance of: Eq, Show, Typeable
+ -- For now don't export Module, to avoid name clashes
tyConFingerprint,
tyConString,
tyConPackage,
@@ -87,7 +88,7 @@ module Data.Typeable
typeRepArgs, -- :: TypeRep -> [TypeRep]
) where
-import Data.Typeable.Internal hiding (mkTyCon)
+import Data.Typeable.Internal
import Data.Type.Equality
import Unsafe.Coerce
diff --git a/libraries/base/Data/Typeable/Internal.hs b/libraries/base/Data/Typeable/Internal.hs
index e35d794a62..4379155c57 100644
--- a/libraries/base/Data/Typeable/Internal.hs
+++ b/libraries/base/Data/Typeable/Internal.hs
@@ -25,15 +25,34 @@
module Data.Typeable.Internal (
Proxy (..),
- TypeRep(..),
- KindRep,
Fingerprint(..),
+
+ -- * Typeable class
typeOf, typeOf1, typeOf2, typeOf3, typeOf4, typeOf5, typeOf6, typeOf7,
Typeable1, Typeable2, Typeable3, Typeable4, Typeable5, Typeable6, Typeable7,
- TyCon(..),
+
+ -- * Module
+ Module, -- Abstract
+ moduleName, modulePackage,
+
+ -- * TyCon
+ TyCon, -- Abstract
+ tyConPackage, tyConModule, tyConName, tyConString, tyConFingerprint,
+ mkTyCon3, mkTyCon3#,
+ rnfTyCon,
+
+ tcBool, tc'True, tc'False,
+ tcOrdering, tc'LT, tc'EQ, tc'GT,
+ tcChar, tcInt, tcWord, tcFloat, tcDouble, tcFun,
+ tcIO, tcSPEC, tcTyCon, tcModule,
+ tcCoercible, tcList, tcEq,
+ tcLiftedKind, tcUnliftedKind, tcOpenKind, tcBOX, tcConstraint, tcAnyK,
+
+ funTc, -- ToDo
+
+ -- * TypeRep
+ TypeRep(..), KindRep,
typeRep,
- mkTyCon,
- mkTyCon3,
mkTyConApp,
mkPolyTyConApp,
mkAppTy,
@@ -47,19 +66,15 @@ module Data.Typeable.Internal (
typeRepFingerprint,
rnfTypeRep,
showsTypeRep,
- tyConString,
- rnfTyCon,
- listTc, funTc,
typeRepKinds,
- typeNatTypeRep,
- typeSymbolTypeRep
+ typeSymbolTypeRep, typeNatTypeRep
) where
import GHC.Base
import GHC.Word
import GHC.Show
-import GHC.TypeLits
import Data.Proxy
+import GHC.TypeLits( KnownNat, KnownSymbol, natVal', symbolVal' )
import GHC.Fingerprint.Type
import {-# SOURCE #-} GHC.Fingerprint
@@ -68,9 +83,106 @@ import {-# SOURCE #-} GHC.Fingerprint
-- of Data.Typeable as much as possible so we can optimise the derived
-- instances.
--- | A concrete representation of a (monomorphic) type. 'TypeRep'
--- supports reasonably efficient equality.
+#include "MachDeps.h"
+
+{- *********************************************************************
+* *
+ The TyCon type
+* *
+********************************************************************* -}
+
+modulePackage :: Module -> String
+modulePackage (Module p _) = trNameString p
+
+moduleName :: Module -> String
+moduleName (Module _ m) = trNameString m
+
+tyConPackage :: TyCon -> String
+tyConPackage (TyCon _ _ m _) = modulePackage m
+
+tyConModule :: TyCon -> String
+tyConModule (TyCon _ _ m _) = moduleName m
+
+tyConName :: TyCon -> String
+tyConName (TyCon _ _ _ n) = trNameString n
+
+trNameString :: TrName -> String
+trNameString (TrNameS s) = unpackCString# s
+trNameString (TrNameD s) = s
+
+-- | Observe string encoding of a type representation
+{-# DEPRECATED tyConString "renamed to 'tyConName'; 'tyConModule' and 'tyConPackage' are also available." #-}
+-- deprecated in 7.4
+tyConString :: TyCon -> String
+tyConString = tyConName
+
+tyConFingerprint :: TyCon -> Fingerprint
+tyConFingerprint (TyCon hi lo _ _)
+ = Fingerprint (W64# hi) (W64# lo)
+
+mkTyCon3# :: Addr# -- ^ package name
+ -> Addr# -- ^ module name
+ -> Addr# -- ^ the name of the type constructor
+ -> TyCon -- ^ A unique 'TyCon' object
+mkTyCon3# pkg modl name
+ | Fingerprint (W64# hi) (W64# lo) <- fingerprint
+ = TyCon hi lo (Module (TrNameS pkg) (TrNameS modl)) (TrNameS name)
+ where
+ fingerprint :: Fingerprint
+ fingerprint = fingerprintString (unpackCString# pkg
+ ++ (' ': unpackCString# modl)
+ ++ (' ' : unpackCString# name))
+
+mkTyCon3 :: String -- ^ package name
+ -> String -- ^ module name
+ -> String -- ^ the name of the type constructor
+ -> TyCon -- ^ A unique 'TyCon' object
+-- Used when the strings are dynamically allocated,
+-- eg from binary deserialisation
+mkTyCon3 pkg modl name
+ | Fingerprint (W64# hi) (W64# lo) <- fingerprint
+ = TyCon hi lo (Module (TrNameD pkg) (TrNameD modl)) (TrNameD name)
+ where
+ fingerprint :: Fingerprint
+ fingerprint = fingerprintString (pkg ++ (' ':modl) ++ (' ':name))
+
+isTupleTyCon :: TyCon -> Bool
+isTupleTyCon tc
+ | ('(':',':_) <- tyConName tc = True
+ | otherwise = False
+
+-- | Helper to fully evaluate 'TyCon' for use as @NFData(rnf)@ implementation
+--
+-- @since 4.8.0.0
+rnfModule :: Module -> ()
+rnfModule (Module p m) = rnfTrName p `seq` rnfTrName m
+
+rnfTrName :: TrName -> ()
+rnfTrName (TrNameS _) = ()
+rnfTrName (TrNameD n) = rnfString n
+
+rnfTyCon :: TyCon -> ()
+rnfTyCon (TyCon _ _ m n) = rnfModule m `seq` rnfTrName n
+
+rnfString :: [Char] -> ()
+rnfString [] = ()
+rnfString (c:cs) = c `seq` rnfString cs
+
+
+{- *********************************************************************
+* *
+ The TypeRep type
+* *
+********************************************************************* -}
+
+-- | A concrete representation of a (monomorphic) type.
+-- 'TypeRep' supports reasonably efficient equality.
data TypeRep = TypeRep {-# UNPACK #-} !Fingerprint TyCon [KindRep] [TypeRep]
+ -- NB: For now I've made this lazy so that it's easy to
+ -- optimise code that constructs and deconstructs TypeReps
+ -- perf/should_run/T9203 is a good example
+ -- Also note that mkAppTy does discards the fingerprint,
+ -- so it's a waste to compute it
type KindRep = TypeRep
@@ -81,56 +193,42 @@ instance Eq TypeRep where
instance Ord TypeRep where
TypeRep x _ _ _ <= TypeRep y _ _ _ = x <= y
+-- | Observe the 'Fingerprint' of a type representation
+--
+-- @since 4.8.0.0
+typeRepFingerprint :: TypeRep -> Fingerprint
+typeRepFingerprint (TypeRep fpr _ _ _) = fpr
--- | An abstract representation of a type constructor. 'TyCon' objects can
--- be built using 'mkTyCon'.
-data TyCon = TyCon {
- tyConFingerprint :: {-# UNPACK #-} !Fingerprint, -- ^ @since 4.8.0.0
- tyConPackage :: String, -- ^ @since 4.5.0.0
- tyConModule :: String, -- ^ @since 4.5.0.0
- tyConName :: String -- ^ @since 4.5.0.0
- }
-
-instance Eq TyCon where
- (TyCon t1 _ _ _) == (TyCon t2 _ _ _) = t1 == t2
-
-instance Ord TyCon where
- (TyCon k1 _ _ _) <= (TyCon k2 _ _ _) = k1 <= k2
-
------------------ Construction --------------------
-
-#include "MachDeps.h"
-
--- mkTyCon is an internal function to make it easier for GHC to
--- generate derived instances. GHC precomputes the MD5 hash for the
--- TyCon and passes it as two separate 64-bit values to mkTyCon. The
--- TyCon for a derived Typeable instance will end up being statically
--- allocated.
-
-#if WORD_SIZE_IN_BITS < 64
-mkTyCon :: Word64# -> Word64# -> String -> String -> String -> TyCon
-#else
-mkTyCon :: Word# -> Word# -> String -> String -> String -> TyCon
-#endif
-mkTyCon high# low# pkg modl name
- = TyCon (Fingerprint (W64# high#) (W64# low#)) pkg modl name
-
--- | Applies a polymorhic type constructor to a sequence of kinds and types
+-- | Applies a kind-polymorphic type constructor to a sequence of kinds and
+-- types
mkPolyTyConApp :: TyCon -> [KindRep] -> [TypeRep] -> TypeRep
-mkPolyTyConApp tc@(TyCon tc_k _ _ _) [] [] = TypeRep tc_k tc [] []
-mkPolyTyConApp tc@(TyCon tc_k _ _ _) kinds types =
- TypeRep (fingerprintFingerprints (tc_k : arg_ks)) tc kinds types
+{-# INLINE mkPolyTyConApp #-}
+mkPolyTyConApp tc kinds types
+ = TypeRep (fingerprintFingerprints sub_fps) tc kinds types
where
- arg_ks = [ k | TypeRep k _ _ _ <- kinds ++ types ]
+ !kt_fps = typeRepFingerprints kinds types
+ sub_fps = tyConFingerprint tc : kt_fps
--- | Applies a monomorphic type constructor to a sequence of types
+typeRepFingerprints :: [KindRep] -> [TypeRep] -> [Fingerprint]
+-- Builds no thunks
+typeRepFingerprints kinds types
+ = go1 [] kinds
+ where
+ go1 acc [] = go2 acc types
+ go1 acc (k:ks) = let !fp = typeRepFingerprint k
+ in go1 (fp:acc) ks
+ go2 acc [] = acc
+ go2 acc (t:ts) = let !fp = typeRepFingerprint t
+ in go2 (fp:acc) ts
+
+-- | Applies a kind-monomorphic type constructor to a sequence of types
mkTyConApp :: TyCon -> [TypeRep] -> TypeRep
mkTyConApp tc = mkPolyTyConApp tc []
-- | A special case of 'mkTyConApp', which applies the function
-- type constructor to a pair of types.
mkFunTy :: TypeRep -> TypeRep -> TypeRep
-mkFunTy f a = mkTyConApp funTc [f,a]
+mkFunTy f a = mkTyConApp tcFun [f,a]
-- | Splits a type constructor application.
-- Note that if the type construcotr is polymorphic, this will
@@ -150,11 +248,12 @@ splitPolyTyConApp (TypeRep _ tc ks trs) = (tc,ks,trs)
funResultTy :: TypeRep -> TypeRep -> Maybe TypeRep
funResultTy trFun trArg
= case splitTyConApp trFun of
- (tc, [t1,t2]) | tc == funTc && t1 == trArg -> Just t2
+ (tc, [t1,t2]) | tc == tcFun && t1 == trArg -> Just t2
_ -> Nothing
-- | Adds a TypeRep argument to a TypeRep.
mkAppTy :: TypeRep -> TypeRep -> TypeRep
+{-# INLINE mkAppTy #-}
mkAppTy (TypeRep _ tc ks trs) arg_tr = mkPolyTyConApp tc ks (trs ++ [arg_tr])
-- Notice that we call mkTyConApp to construct the fingerprint from tc and
-- the arg fingerprints. Simply combining the current fingerprint with
@@ -162,20 +261,6 @@ mkAppTy (TypeRep _ tc ks trs) arg_tr = mkPolyTyConApp tc ks (trs ++ [arg_tr])
-- ensure that a TypeRep of the same shape has the same fingerprint!
-- See Trac #5962
--- | Builds a 'TyCon' object representing a type constructor. An
--- implementation of "Data.Typeable" should ensure that the following holds:
---
--- > A==A' ^ B==B' ^ C==C' ==> mkTyCon A B C == mkTyCon A' B' C'
---
-
---
-mkTyCon3 :: String -- ^ package name
- -> String -- ^ module name
- -> String -- ^ the name of the type constructor
- -> TyCon -- ^ A unique 'TyCon' object
-mkTyCon3 pkg modl name =
- TyCon (fingerprintString (pkg ++ (' ':modl) ++ (' ':name))) pkg modl name
-
----------------- Observation ---------------------
-- | Observe the type constructor of a type representation
@@ -190,16 +275,12 @@ typeRepArgs (TypeRep _ _ _ tys) = tys
typeRepKinds :: TypeRep -> [KindRep]
typeRepKinds (TypeRep _ _ ks _) = ks
--- | Observe string encoding of a type representation
-{-# DEPRECATED tyConString "renamed to 'tyConName'; 'tyConModule' and 'tyConPackage' are also available." #-} -- deprecated in 7.4
-tyConString :: TyCon -> String
-tyConString = tyConName
--- | Observe the 'Fingerprint' of a type representation
---
--- @since 4.8.0.0
-typeRepFingerprint :: TypeRep -> Fingerprint
-typeRepFingerprint (TypeRep fpr _ _ _) = fpr
+{- *********************************************************************
+* *
+ The Typeable class
+* *
+********************************************************************* -}
-------------------------------------------------------------
--
@@ -273,8 +354,8 @@ instance Show TypeRep where
showsPrec p (TypeRep _ tycon kinds tys) =
case tys of
[] -> showsPrec p tycon
- [x] | tycon == listTc -> showChar '[' . shows x . showChar ']'
- [a,r] | tycon == funTc -> showParen (p > 8) $
+ [x] | tycon == tcList -> showChar '[' . shows x . showChar ']'
+ [a,r] | tycon == tcFun -> showParen (p > 8) $
showsPrec 9 a .
showString " -> " .
showsPrec 8 r
@@ -288,13 +369,6 @@ instance Show TypeRep where
showsTypeRep :: TypeRep -> ShowS
showsTypeRep = shows
-instance Show TyCon where
- showsPrec _ t = showString (tyConName t)
-
-isTupleTyCon :: TyCon -> Bool
-isTupleTyCon (TyCon _ _ _ ('(':',':_)) = True
-isTupleTyCon _ = False
-
-- | Helper to fully evaluate 'TypeRep' for use as @NFData(rnf)@ implementation
--
-- @since 4.8.0.0
@@ -304,15 +378,6 @@ rnfTypeRep (TypeRep _ tyc krs tyrs) = rnfTyCon tyc `seq` go krs `seq` go tyrs
go [] = ()
go (x:xs) = rnfTypeRep x `seq` go xs
--- | Helper to fully evaluate 'TyCon' for use as @NFData(rnf)@ implementation
---
--- @since 4.8.0.0
-rnfTyCon :: TyCon -> ()
-rnfTyCon (TyCon _ tcp tcm tcn) = go tcp `seq` go tcm `seq` go tcn
- where
- go [] = ()
- go (x:xs) = x `seq` go xs
-
-- Some (Show.TypeRep) helpers:
showArgs :: Show a => ShowS -> [a] -> ShowS
@@ -325,13 +390,68 @@ showTuple args = showChar '('
. showArgs (showChar ',') args
. showChar ')'
-listTc :: TyCon
-listTc = typeRepTyCon (typeOf [()])
+{- *********************************************************
+* *
+* TyCon definitions for GHC.Types *
+* *
+********************************************************* -}
+
+mkGhcTypesTyCon :: Addr# -> TyCon
+{-# INLINE mkGhcTypesTyCon #-}
+mkGhcTypesTyCon name = mkTyCon3# "ghc-prim"# "GHC.Types"# name
+
+tcBool, tc'True, tc'False,
+ tcOrdering, tc'GT, tc'EQ, tc'LT,
+ tcChar, tcInt, tcWord, tcFloat, tcDouble, tcFun,
+ tcIO, tcSPEC, tcTyCon, tcModule,
+ tcCoercible, tcEq, tcList :: TyCon
+
+tcBool = mkGhcTypesTyCon "Bool"# -- Bool is promotable
+tc'True = mkGhcTypesTyCon "'True"#
+tc'False = mkGhcTypesTyCon "'False"#
+tcOrdering = mkGhcTypesTyCon "Ordering"# -- Ordering is promotable
+tc'GT = mkGhcTypesTyCon "'GT"#
+tc'EQ = mkGhcTypesTyCon "'EQ"#
+tc'LT = mkGhcTypesTyCon "'LT"#
+
+-- None of the rest are promotable (see TysWiredIn)
+tcChar = mkGhcTypesTyCon "Char"#
+tcInt = mkGhcTypesTyCon "Int"#
+tcWord = mkGhcTypesTyCon "Word"#
+tcFloat = mkGhcTypesTyCon "Float"#
+tcDouble = mkGhcTypesTyCon "Double"#
+tcSPEC = mkGhcTypesTyCon "SPEC"#
+tcIO = mkGhcTypesTyCon "IO"#
+tcTyCon = mkGhcTypesTyCon "TyCon"#
+tcModule = mkGhcTypesTyCon "Module"#
+tcCoercible = mkGhcTypesTyCon "Coercible"#
+
+tcFun = mkGhcTypesTyCon "->"#
+tcList = mkGhcTypesTyCon "[]"# -- Type rep for the list type constructor
+tcEq = mkGhcTypesTyCon "~"# -- Type rep for the (~) type constructor
+
+tcLiftedKind, tcUnliftedKind, tcOpenKind, tcBOX, tcConstraint, tcAnyK :: TyCon
+tcLiftedKind = mkGhcTypesTyCon "*"#
+tcUnliftedKind = mkGhcTypesTyCon "#"#
+tcOpenKind = mkGhcTypesTyCon "#"#
+tcBOX = mkGhcTypesTyCon "BOX"#
+tcAnyK = mkGhcTypesTyCon "AnyK"#
+tcConstraint = mkGhcTypesTyCon "Constraint"#
funTc :: TyCon
-funTc = typeRepTyCon (typeRep (Proxy :: Proxy (->)))
+funTc = tcFun -- Legacy
+
+{- *********************************************************
+* *
+* TyCon/TypeRep definitions for type literals *
+* (Symbol and Nat) *
+* *
+********************************************************* -}
+mkTypeLitTyCon :: String -> TyCon
+mkTypeLitTyCon name = mkTyCon3 "base" "GHC.TypeLits" name
+
-- | Used to make `'Typeable' instance for things of kind Nat
typeNatTypeRep :: KnownNat a => Proxy# a -> TypeRep
typeNatTypeRep p = typeLitTypeRep (show (natVal' p))
@@ -342,17 +462,5 @@ typeSymbolTypeRep p = typeLitTypeRep (show (symbolVal' p))
-- | An internal function, to make representations for type literals.
typeLitTypeRep :: String -> TypeRep
-typeLitTypeRep nm = rep
- where
- rep = mkTyConApp tc []
- tc = TyCon
- { tyConFingerprint = fingerprintString (mk pack modu nm)
- , tyConPackage = pack
- , tyConModule = modu
- , tyConName = nm
- }
- pack = "base"
- modu = "GHC.TypeLits"
- mk a b c = a ++ " " ++ b ++ " " ++ c
-
+typeLitTypeRep nm = mkTyConApp (mkTypeLitTyCon nm) []
diff --git a/libraries/base/GHC/Show.hs b/libraries/base/GHC/Show.hs
index 4aeecb15f3..879d666bb0 100644
--- a/libraries/base/GHC/Show.hs
+++ b/libraries/base/GHC/Show.hs
@@ -194,6 +194,16 @@ showWord w# cs
deriving instance Show a => Show (Maybe a)
+instance Show TyCon where
+ showsPrec p (TyCon _ _ _ tc_name) = showsPrec p tc_name
+
+instance Show TrName where
+ showsPrec _ (TrNameS s) = showString (unpackCString# s)
+ showsPrec _ (TrNameD s) = showString s
+
+instance Show Module where
+ showsPrec _ (Module p m) = shows p . (':' :) . shows m
+
--------------------------------------------------------------
-- Show instances for the first few tuple
--------------------------------------------------------------
diff --git a/libraries/base/GHC/Stack/Types.hs b/libraries/base/GHC/Stack/Types.hs
index 5c37f64713..d3ea1d2147 100644
--- a/libraries/base/GHC/Stack/Types.hs
+++ b/libraries/base/GHC/Stack/Types.hs
@@ -21,6 +21,19 @@ module GHC.Stack.Types (
SrcLoc(..), CallStack(..),
) where
+{-
+Ideally these would live in GHC.Stack but sadly they can't due to this
+import cycle,
+
+ Module imports form a cycle:
+ module ‘Data.Maybe’ (libraries/base/Data/Maybe.hs)
+ imports ‘GHC.Base’ (libraries/base/GHC/Base.hs)
+ which imports ‘GHC.Err’ (libraries/base/GHC/Err.hs)
+ which imports ‘GHC.Stack’ (libraries/base/dist-install/build/GHC/Stack.hs)
+ which imports ‘GHC.Foreign’ (libraries/base/GHC/Foreign.hs)
+ which imports ‘Data.Maybe’ (libraries/base/Data/Maybe.hs)
+-}
+
import GHC.Types
-- Make implicit dependency known to build system