{-# LANGUAGE CPP #-} {-# LANGUAGE ConstraintKinds #-} {-# LANGUAGE DeriveDataTypeable #-} {-# LANGUAGE FlexibleContexts #-} {-# LANGUAGE FlexibleInstances #-} {-# LANGUAGE ScopedTypeVariables #-} {-# LANGUAGE StandaloneDeriving #-} {-# LANGUAGE TypeFamilies #-} {-# LANGUAGE UndecidableInstances #-} -- Wrinkle in Note [Trees That Grow] -- in module Language.Haskell.Syntax.Extension {- (c) The University of Glasgow 2006 (c) The GRASP/AQUA Project, Glasgow University, 1992-1998 GHC.Hs.Type: Abstract syntax: user-defined types -} -- See Note [Language.Haskell.Syntax.* Hierarchy] for why not GHC.Hs.* module Language.Haskell.Syntax.Type ( Mult, HsScaled(..), hsMult, hsScaledThing, HsArrow(..), hsLinear, hsUnrestricted, HsType(..), HsCoreTy, LHsType, HsKind, LHsKind, HsForAllTelescope(..), HsTyVarBndr(..), LHsTyVarBndr, LHsQTyVars(..), HsOuterTyVarBndrs(..), HsOuterFamEqnTyVarBndrs, HsOuterSigTyVarBndrs, HsWildCardBndrs(..), HsPatSigType(..), HsPSRn(..), HsSigType(..), LHsSigType, LHsSigWcType, LHsWcType, HsTupleSort(..), HsContext, LHsContext, HsTyLit(..), HsIPName(..), hsIPNameFS, HsArg(..), numVisibleArgs, LHsTypeArg, LBangType, BangType, HsSrcBang(..), HsImplBang(..), SrcStrictness(..), SrcUnpackedness(..), ConDeclField(..), LConDeclField, HsConDetails(..), noTypeArgs, FieldOcc(..), LFieldOcc, AmbiguousFieldOcc(..), mapHsOuterImplicit, hsQTvExplicit, isHsKindedTyVar, hsPatSigType, ) where #include "HsVersions.h" import GHC.Prelude import {-# SOURCE #-} Language.Haskell.Syntax.Expr ( HsSplice ) import Language.Haskell.Syntax.Extension import GHC.Types.SourceText import GHC.Types.Name( Name ) import GHC.Types.Name.Reader ( RdrName ) import GHC.Core.DataCon( HsSrcBang(..), HsImplBang(..), SrcStrictness(..), SrcUnpackedness(..) ) import GHC.Core.Type import GHC.Hs.Doc import GHC.Types.Basic import GHC.Types.SrcLoc import GHC.Utils.Outputable import GHC.Data.FastString import GHC.Utils.Misc ( count ) import GHC.Parser.Annotation import Data.Data hiding ( Fixity, Prefix, Infix ) import Data.Void {- ************************************************************************ * * \subsection{Bang annotations} * * ************************************************************************ -} -- | Located Bang Type type LBangType pass = XRec pass (BangType pass) -- | Bang Type -- -- In the parser, strictness and packedness annotations bind more tightly -- than docstrings. This means that when consuming a 'BangType' (and looking -- for 'HsBangTy') we must be ready to peer behind a potential layer of -- 'HsDocTy'. See #15206 for motivation and 'getBangType' for an example. type BangType pass = HsType pass -- Bangs are in the HsType data type {- ************************************************************************ * * \subsection{Data types} * * ************************************************************************ This is the syntax for types as seen in type signatures. Note [HsBSig binder lists] ~~~~~~~~~~~~~~~~~~~~~~~~~~ Consider a binder (or pattern) decorated with a type or kind, \ (x :: a -> a). blah forall (a :: k -> *) (b :: k). blah Then we use a LHsBndrSig on the binder, so that the renamer can decorate it with the variables bound by the pattern ('a' in the first example, 'k' in the second), assuming that neither of them is in scope already See also Note [Kind and type-variable binders] in GHC.Rename.HsType Note [HsType binders] ~~~~~~~~~~~~~~~~~~~~~ The system for recording type and kind-variable binders in HsTypes is a bit complicated. Here's how it works. * In a HsType, HsForAllTy represents an /explicit, user-written/ 'forall' that is nested within another HsType e.g. forall a b. {...} or forall a b -> {...} Note that top-level 'forall's are represented with a different AST form. See the description of HsOuterTyVarBndrs below. HsQualTy represents an /explicit, user-written/ context e.g. (Eq a, Show a) => ... The context can be empty if that's what the user wrote These constructors represent what the user wrote, no more and no less. * The ForAllTelescope field of HsForAllTy represents whether a forall is invisible (e.g., forall a b. {...}, with a dot) or visible (e.g., forall a b -> {...}, with an arrow). * HsTyVarBndr describes a quantified type variable written by the user. For example f :: forall a (b :: *). blah here 'a' and '(b::*)' are each a HsTyVarBndr. A HsForAllTy has a list of LHsTyVarBndrs. * HsOuterTyVarBndrs is used to represent the outermost quantified type variables in a type that obeys the forall-or-nothing rule. An HsOuterTyVarBndrs can be one of the following: HsOuterImplicit (implicit quantification, added by renamer) f :: a -> a -- Desugars to f :: forall {a}. a -> a HsOuterExplicit (explicit user quantifiation): f :: forall a. a -> a See Note [forall-or-nothing rule]. * An HsSigType is an LHsType with an accompanying HsOuterTyVarBndrs that represents the presence (or absence) of its outermost 'forall'. See Note [Representing type signatures]. * HsWildCardBndrs is a wrapper that binds the wildcard variables of the wrapped thing. It is filled in by the renamer f :: _a -> _ The enclosing HsWildCardBndrs binds the wildcards _a and _. * HsSigPatType describes types that appear in pattern signatures and the signatures of term-level binders in RULES. Like HsWildCardBndrs/HsOuterTyVarBndrs, they track the names of wildcard variables and implicitly bound type variables. Unlike HsOuterTyVarBndrs, however, HsSigPatTypes do not obey the forall-or-nothing rule. See Note [Pattern signature binders and scoping]. * The explicit presence of these wrappers specifies, in the HsSyn, exactly where implicit quantification is allowed, and where wildcards are allowed. * LHsQTyVars is used in data/class declarations, where the user gives explicit *type* variable bindings, but we need to implicitly bind *kind* variables. For example class C (a :: k -> *) where ... The 'k' is implicitly bound in the hsq_tvs field of LHsQTyVars Note [The wildcard story for types] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Types can have wildcards in them, to support partial type signatures, like f :: Int -> (_ , _a) -> _a A wildcard in a type can be * An anonymous wildcard, written '_' In HsType this is represented by HsWildCardTy. The renamer leaves it untouched, and it is later given a fresh meta tyvar in the typechecker. * A named wildcard, written '_a', '_foo', etc In HsType this is represented by (HsTyVar "_a") i.e. a perfectly ordinary type variable that happens to start with an underscore Note carefully: * When NamedWildCards is off, type variables that start with an underscore really /are/ ordinary type variables. And indeed, even when NamedWildCards is on you can bind _a explicitly as an ordinary type variable: data T _a _b = MkT _b _a Or even: f :: forall _a. _a -> _b Here _a is an ordinary forall'd binder, but (With NamedWildCards) _b is a named wildcard. (See the comments in #10982) * Named wildcards are bound by the HsWildCardBndrs (for types that obey the forall-or-nothing rule) and HsPatSigType (for type signatures in patterns and term-level binders in RULES), which wrap types that are allowed to have wildcards. Unnamed wildcards, however are left unchanged until typechecking, where we give them fresh wild tyvars and determine whether or not to emit hole constraints on each wildcard (we don't if it's a visible type/kind argument or a type family pattern). See related notes Note [Wildcards in visible kind application] and Note [Wildcards in visible type application] in GHC.Tc.Gen.HsType. * After type checking is done, we report what types the wildcards got unified with. Note [Ordering of implicit variables] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Since the advent of -XTypeApplications, GHC makes promises about the ordering of implicit variable quantification. Specifically, we offer that implicitly quantified variables (such as those in const :: a -> b -> a, without a `forall`) will occur in left-to-right order of first occurrence. Here are a few examples: const :: a -> b -> a -- forall a b. ... f :: Eq a => b -> a -> a -- forall a b. ... contexts are included type a <-< b = b -> a g :: a <-< b -- forall a b. ... type synonyms matter class Functor f where fmap :: (a -> b) -> f a -> f b -- forall f a b. ... -- The f is quantified by the class, so only a and b are considered in fmap This simple story is complicated by the possibility of dependency: all variables must come after any variables mentioned in their kinds. typeRep :: Typeable a => TypeRep (a :: k) -- forall k a. ... The k comes first because a depends on k, even though the k appears later than the a in the code. Thus, GHC does a *stable topological sort* on the variables. By "stable", we mean that any two variables who do not depend on each other preserve their existing left-to-right ordering. Implicitly bound variables are collected by the extract- family of functions (extractHsTysRdrTyVars, extractHsTyVarBndrsKVs, etc.) in GHC.Rename.HsType. These functions thus promise to keep left-to-right ordering. Look for pointers to this note to see the places where the action happens. Note that we also maintain this ordering in kind signatures. Even though there's no visible kind application (yet), having implicit variables be quantified in left-to-right order in kind signatures is nice since: * It's consistent with the treatment for type signatures. * It can affect how types are displayed with -fprint-explicit-kinds (see #15568 for an example), which is a situation where knowing the order in which implicit variables are quantified can be useful. * In the event that visible kind application is implemented, the order in which we would expect implicit variables to be ordered in kinds will have already been established. -} -- | Located Haskell Context type LHsContext pass = XRec pass (HsContext pass) -- ^ 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnUnit' -- For details on above see note [exact print annotations] in GHC.Parser.Annotation -- | Haskell Context type HsContext pass = [LHsType pass] -- | Located Haskell Type type LHsType pass = XRec pass (HsType pass) -- ^ May have 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnComma' when -- in a list -- For details on above see note [exact print annotations] in GHC.Parser.Annotation -- | Haskell Kind type HsKind pass = HsType pass -- | Located Haskell Kind type LHsKind pass = XRec pass (HsKind pass) -- ^ 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnDcolon' -- For details on above see note [exact print annotations] in GHC.Parser.Annotation -------------------------------------------------- -- LHsQTyVars -- The explicitly-quantified binders in a data/type declaration -- | The type variable binders in an 'HsForAllTy'. -- See also @Note [Variable Specificity and Forall Visibility]@ in -- "GHC.Tc.Gen.HsType". data HsForAllTelescope pass = HsForAllVis -- ^ A visible @forall@ (e.g., @forall a -> {...}@). -- These do not have any notion of specificity, so we use -- '()' as a placeholder value. { forall pass. HsForAllTelescope pass -> XHsForAllVis pass hsf_xvis :: XHsForAllVis pass , forall pass. HsForAllTelescope pass -> [LHsTyVarBndr () pass] hsf_vis_bndrs :: [LHsTyVarBndr () pass] } | HsForAllInvis -- ^ An invisible @forall@ (e.g., @forall a {b} c. {...}@), -- where each binder has a 'Specificity'. { forall pass. HsForAllTelescope pass -> XHsForAllInvis pass hsf_xinvis :: XHsForAllInvis pass , forall pass. HsForAllTelescope pass -> [LHsTyVarBndr Specificity pass] hsf_invis_bndrs :: [LHsTyVarBndr Specificity pass] } | XHsForAllTelescope !(XXHsForAllTelescope pass) -- | Located Haskell Type Variable Binder type LHsTyVarBndr flag pass = XRec pass (HsTyVarBndr flag pass) -- See Note [HsType binders] -- | Located Haskell Quantified Type Variables data LHsQTyVars pass -- See Note [HsType binders] = HsQTvs { forall pass. LHsQTyVars pass -> XHsQTvs pass hsq_ext :: XHsQTvs pass , forall pass. LHsQTyVars pass -> [LHsTyVarBndr () pass] hsq_explicit :: [LHsTyVarBndr () pass] -- Explicit variables, written by the user } | XLHsQTyVars !(XXLHsQTyVars pass) hsQTvExplicit :: LHsQTyVars pass -> [LHsTyVarBndr () pass] hsQTvExplicit :: forall pass. LHsQTyVars pass -> [LHsTyVarBndr () pass] hsQTvExplicit = forall pass. LHsQTyVars pass -> [LHsTyVarBndr () pass] hsq_explicit ------------------------------------------------ -- HsOuterTyVarBndrs -- Used to quantify the outermost type variable binders of a type that obeys -- the forall-or-nothing rule. These are used to represent the outermost -- quantification in: -- * Type signatures (LHsSigType/LHsSigWcType) -- * Patterns in a type/data family instance (HsTyPats) -- -- We support two forms: -- HsOuterImplicit (implicit quantification, added by renamer) -- f :: a -> a -- Desugars to f :: forall {a}. a -> a -- type instance F (a,b) = a->b -- HsOuterExplicit (explicit user quantifiation): -- f :: forall a. a -> a -- type instance forall a b. F (a,b) = a->b -- -- In constrast, when the user writes /visible/ quanitification -- T :: forall k -> k -> Type -- we use use HsOuterImplicit, wrapped around a HsForAllTy -- for the visible quantification -- -- See Note [forall-or-nothing rule] -- | The outermost type variables in a type that obeys the @forall@-or-nothing -- rule. See @Note [forall-or-nothing rule]@. data HsOuterTyVarBndrs flag pass = HsOuterImplicit -- ^ Implicit forall, e.g., -- @f :: a -> b -> b@ { forall flag pass. HsOuterTyVarBndrs flag pass -> XHsOuterImplicit pass hso_ximplicit :: XHsOuterImplicit pass } | HsOuterExplicit -- ^ Explicit forall, e.g., -- @f :: forall a b. a -> b -> b@ { forall flag pass. HsOuterTyVarBndrs flag pass -> XHsOuterExplicit pass flag hso_xexplicit :: XHsOuterExplicit pass flag , forall flag pass. HsOuterTyVarBndrs flag pass -> [LHsTyVarBndr flag (NoGhcTc pass)] hso_bndrs :: [LHsTyVarBndr flag (NoGhcTc pass)] } | XHsOuterTyVarBndrs !(XXHsOuterTyVarBndrs pass) -- | Used for signatures, e.g., -- -- @ -- f :: forall a {b}. blah -- @ -- -- We use 'Specificity' for the 'HsOuterTyVarBndrs' @flag@ to allow -- distinguishing between specified and inferred type variables. type HsOuterSigTyVarBndrs = HsOuterTyVarBndrs Specificity -- | Used for type-family instance equations, e.g., -- -- @ -- type instance forall a. F [a] = Tree a -- @ -- -- The notion of specificity is irrelevant in type family equations, so we use -- @()@ for the 'HsOuterTyVarBndrs' @flag@. type HsOuterFamEqnTyVarBndrs = HsOuterTyVarBndrs () -- | Haskell Wildcard Binders data HsWildCardBndrs pass thing -- See Note [HsType binders] -- See Note [The wildcard story for types] = HsWC { forall pass thing. HsWildCardBndrs pass thing -> XHsWC pass thing hswc_ext :: XHsWC pass thing -- after the renamer -- Wild cards, only named -- See Note [Wildcards in visible kind application] , forall pass thing. HsWildCardBndrs pass thing -> thing hswc_body :: thing -- Main payload (type or list of types) -- If there is an extra-constraints wildcard, -- it's still there in the hsc_body. } | XHsWildCardBndrs !(XXHsWildCardBndrs pass thing) -- | Types that can appear in pattern signatures, as well as the signatures for -- term-level binders in RULES. -- See @Note [Pattern signature binders and scoping]@. -- -- This is very similar to 'HsSigWcType', but with -- slightly different semantics: see @Note [HsType binders]@. -- See also @Note [The wildcard story for types]@. data HsPatSigType pass = HsPS { forall pass. HsPatSigType pass -> XHsPS pass hsps_ext :: XHsPS pass -- ^ After renamer: 'HsPSRn' , forall pass. HsPatSigType pass -> LHsType pass hsps_body :: LHsType pass -- ^ Main payload (the type itself) } | XHsPatSigType !(XXHsPatSigType pass) -- | The extension field for 'HsPatSigType', which is only used in the -- renamer onwards. See @Note [Pattern signature binders and scoping]@. data HsPSRn = HsPSRn { HsPSRn -> [Name] hsps_nwcs :: [Name] -- ^ Wildcard names , HsPSRn -> [Name] hsps_imp_tvs :: [Name] -- ^ Implicitly bound variable names } deriving Typeable HsPSRn HsPSRn -> DataType HsPSRn -> Constr (forall b. Data b => b -> b) -> HsPSRn -> HsPSRn forall a. Typeable a -> (forall (c :: * -> *). (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> a -> c a) -> (forall (c :: * -> *). (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c a) -> (a -> Constr) -> (a -> DataType) -> (forall (t :: * -> *) (c :: * -> *). Typeable t => (forall d. Data d => c (t d)) -> Maybe (c a)) -> (forall (t :: * -> * -> *) (c :: * -> *). Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c a)) -> ((forall b. Data b => b -> b) -> a -> a) -> (forall r r'. (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> a -> r) -> (forall r r'. (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> a -> r) -> (forall u. (forall d. Data d => d -> u) -> a -> [u]) -> (forall u. Int -> (forall d. Data d => d -> u) -> a -> u) -> (forall (m :: * -> *). Monad m => (forall d. Data d => d -> m d) -> a -> m a) -> (forall (m :: * -> *). MonadPlus m => (forall d. Data d => d -> m d) -> a -> m a) -> (forall (m :: * -> *). MonadPlus m => (forall d. Data d => d -> m d) -> a -> m a) -> Data a forall u. Int -> (forall d. Data d => d -> u) -> HsPSRn -> u forall u. (forall d. Data d => d -> u) -> HsPSRn -> [u] forall r r'. (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> HsPSRn -> r forall r r'. (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> HsPSRn -> r forall (m :: * -> *). Monad m => (forall d. Data d => d -> m d) -> HsPSRn -> m HsPSRn forall (m :: * -> *). MonadPlus m => (forall d. Data d => d -> m d) -> HsPSRn -> m HsPSRn forall (c :: * -> *). (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c HsPSRn forall (c :: * -> *). (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> HsPSRn -> c HsPSRn forall (t :: * -> *) (c :: * -> *). Typeable t => (forall d. Data d => c (t d)) -> Maybe (c HsPSRn) forall (t :: * -> * -> *) (c :: * -> *). Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c HsPSRn) gmapMo :: forall (m :: * -> *). MonadPlus m => (forall d. Data d => d -> m d) -> HsPSRn -> m HsPSRn $cgmapMo :: forall (m :: * -> *). MonadPlus m => (forall d. Data d => d -> m d) -> HsPSRn -> m HsPSRn gmapMp :: forall (m :: * -> *). MonadPlus m => (forall d. Data d => d -> m d) -> HsPSRn -> m HsPSRn $cgmapMp :: forall (m :: * -> *). MonadPlus m => (forall d. Data d => d -> m d) -> HsPSRn -> m HsPSRn gmapM :: forall (m :: * -> *). Monad m => (forall d. Data d => d -> m d) -> HsPSRn -> m HsPSRn $cgmapM :: forall (m :: * -> *). Monad m => (forall d. Data d => d -> m d) -> HsPSRn -> m HsPSRn gmapQi :: forall u. Int -> (forall d. Data d => d -> u) -> HsPSRn -> u $cgmapQi :: forall u. Int -> (forall d. Data d => d -> u) -> HsPSRn -> u gmapQ :: forall u. (forall d. Data d => d -> u) -> HsPSRn -> [u] $cgmapQ :: forall u. (forall d. Data d => d -> u) -> HsPSRn -> [u] gmapQr :: forall r r'. (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> HsPSRn -> r $cgmapQr :: forall r r'. (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> HsPSRn -> r gmapQl :: forall r r'. (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> HsPSRn -> r $cgmapQl :: forall r r'. (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> HsPSRn -> r gmapT :: (forall b. Data b => b -> b) -> HsPSRn -> HsPSRn $cgmapT :: (forall b. Data b => b -> b) -> HsPSRn -> HsPSRn dataCast2 :: forall (t :: * -> * -> *) (c :: * -> *). Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c HsPSRn) $cdataCast2 :: forall (t :: * -> * -> *) (c :: * -> *). Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c HsPSRn) dataCast1 :: forall (t :: * -> *) (c :: * -> *). Typeable t => (forall d. Data d => c (t d)) -> Maybe (c HsPSRn) $cdataCast1 :: forall (t :: * -> *) (c :: * -> *). Typeable t => (forall d. Data d => c (t d)) -> Maybe (c HsPSRn) dataTypeOf :: HsPSRn -> DataType $cdataTypeOf :: HsPSRn -> DataType toConstr :: HsPSRn -> Constr $ctoConstr :: HsPSRn -> Constr gunfold :: forall (c :: * -> *). (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c HsPSRn $cgunfold :: forall (c :: * -> *). (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c HsPSRn gfoldl :: forall (c :: * -> *). (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> HsPSRn -> c HsPSRn $cgfoldl :: forall (c :: * -> *). (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> HsPSRn -> c HsPSRn Data -- | Located Haskell Signature Type type LHsSigType pass = XRec pass (HsSigType pass) -- Implicit only -- | Located Haskell Wildcard Type type LHsWcType pass = HsWildCardBndrs pass (LHsType pass) -- Wildcard only -- | Located Haskell Signature Wildcard Type type LHsSigWcType pass = HsWildCardBndrs pass (LHsSigType pass) -- Both -- | A type signature that obeys the @forall@-or-nothing rule. In other -- words, an 'LHsType' that uses an 'HsOuterSigTyVarBndrs' to represent its -- outermost type variable quantification. -- See @Note [Representing type signatures]@. data HsSigType pass = HsSig { forall pass. HsSigType pass -> XHsSig pass sig_ext :: XHsSig pass , forall pass. HsSigType pass -> HsOuterSigTyVarBndrs pass sig_bndrs :: HsOuterSigTyVarBndrs pass , forall pass. HsSigType pass -> LHsType pass sig_body :: LHsType pass } | XHsSigType !(XXHsSigType pass) hsPatSigType :: HsPatSigType pass -> LHsType pass hsPatSigType :: forall pass. HsPatSigType pass -> LHsType pass hsPatSigType = forall pass. HsPatSigType pass -> LHsType pass hsps_body {- Note [forall-or-nothing rule] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Free variables in signatures are usually bound in an implicit 'forall' at the beginning of user-written signatures. However, if the signature has an explicit, invisible forall at the beginning, this is disabled. This is referred to as the forall-or-nothing rule. The idea is nested foralls express something which is only expressible explicitly, while a top level forall could (usually) be replaced with an implicit binding. Top-level foralls alone ("forall.") are therefore an indication that the user is trying to be fastidious, so we don't implicitly bind any variables. Note that this rule only applies to outermost /in/visible 'forall's, and not outermost visible 'forall's. See #18660 for more on this point. Here are some concrete examples to demonstrate the forall-or-nothing rule in action: type F1 :: a -> b -> b -- Legal; a,b are implicitly quantified. -- Equivalently: forall a b. a -> b -> b type F2 :: forall a b. a -> b -> b -- Legal; explicitly quantified type F3 :: forall a. a -> b -> b -- Illegal; the forall-or-nothing rule says that -- if you quantify a, you must also quantify b type F4 :: forall a -> b -> b -- Legal; the top quantifier (forall a) is a /visible/ -- quantifer, so the "nothing" part of the forall-or-nothing -- rule applies, and b is therefore implicitly quantified. -- Equivalently: forall b. forall a -> b -> b type F5 :: forall b. forall a -> b -> c -- Illegal; the forall-or-nothing rule says that -- if you quantify b, you must also quantify c type F6 :: forall a -> forall b. b -> c -- Legal: just like F4. For a complete list of all places where the forall-or-nothing rule applies, see "The `forall`-or-nothing rule" section of the GHC User's Guide. Any type that obeys the forall-or-nothing rule is represented in the AST with an HsOuterTyVarBndrs: * If the type has an outermost, invisible 'forall', it uses HsOuterExplicit, which contains a list of the explicitly quantified type variable binders in `hso_bndrs`. After typechecking, HsOuterExplicit also stores a list of the explicitly quantified `InvisTVBinder`s in `hso_xexplicit :: XHsOuterExplicit GhcTc`. * Otherwise, it uses HsOuterImplicit. HsOuterImplicit is used for different things depending on the phase: * After parsing, it does not store anything in particular. * After renaming, it stores the implicitly bound type variable `Name`s in `hso_ximplicit :: XHsOuterImplicit GhcRn`. * After typechecking, it stores the implicitly bound `TyVar`s in `hso_ximplicit :: XHsOuterImplicit GhcTc`. NB: this implicit quantification is purely lexical: we bind any type or kind variables that are not in scope. The type checker may subsequently quantify over further kind variables. See Note [Binding scoped type variables] in GHC.Tc.Gen.Sig. HsOuterTyVarBndrs GhcTc is used in the typechecker as an intermediate data type for storing the outermost TyVars/InvisTVBinders in a type. See GHC.Tc.Gen.HsType.bindOuterTKBndrsX for an example of this. Note [Representing type signatures] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ HsSigType is used to represent an explicit user type signature. These are used in a variety of places. Some examples include: * Type signatures (e.g., f :: a -> a) * Standalone kind signatures (e.g., type G :: a -> a) * GADT constructor types (e.g., data T where MkT :: a -> T) A HsSigType is the combination of an HsOuterSigTyVarBndrs and an LHsType: * The HsOuterSigTyVarBndrs binds the /explicitly/ quantified type variables when the type signature has an outermost, user-written 'forall' (i.e, the HsOuterExplicit constructor is used). If there is no outermost 'forall', then it binds the /implicitly/ quantified type variables instead (i.e., the HsOuterImplicit constructor is used). * The LHsType represents the rest of the type. E.g. For a signature like f :: forall k (a::k). blah we get HsSig { sig_bndrs = HsOuterExplicit { hso_bndrs = [k, (a :: k)] } , sig_body = blah } Note [Pattern signature binders and scoping] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Consider the pattern signatures like those on `t` and `g` in: f = let h = \(t :: (b, b) -> \(g :: forall a. a -> b) -> ...(t :: (Int,Int))... in woggle * The `b` in t's pattern signature is implicitly bound and scopes over the signature and the body of the lambda. It stands for a type (any type); indeed we subsequently discover that b=Int. (See Note [TyVarTv] in GHC.Tc.Utils.TcMType for more on this point.) * The `b` in g's pattern signature is an /occurrence/ of the `b` bound by t's pattern signature. * The `a` in `forall a` scopes only over the type `a -> b`, not over the body of the lambda. * There is no forall-or-nothing rule for pattern signatures, which is why the type `forall a. a -> b` is permitted in `g`'s pattern signature, even though `b` is not explicitly bound. See Note [forall-or-nothing rule]. Similar scoping rules apply to term variable binders in RULES, like in the following example: {-# RULES "h" forall (t :: (b, b)) (g :: forall a. a -> b). h t g = ... #-} Just like in pattern signatures, the `b` in t's signature is implicitly bound and scopes over the remainder of the RULE. As a result, the `b` in g's signature is an occurrence. Moreover, the `a` in `forall a` scopes only over the type `a -> b`, and the forall-or-nothing rule does not apply. While quite similar, RULE term binder signatures behave slightly differently from pattern signatures in two ways: 1. Unlike in pattern signatures, where type variables can stand for any type, type variables in RULE term binder signatures are skolems. See Note [Typechecking pattern signature binders] in GHC.Tc.Gen.HsType for more on this point. In this sense, type variables in pattern signatures are quite similar to named wildcards, as both can refer to arbitrary types. The main difference lies in error reporting: if a named wildcard `_a` in a pattern signature stands for Int, then by default GHC will emit a warning stating as much. Changing `_a` to `a`, on the other hand, will cause it not to be reported. 2. In the `h` RULE above, only term variables are explicitly bound, so any free type variables in the term variables' signatures are implicitly bound. This is just like how the free type variables in pattern signatures are implicitly bound. If a RULE explicitly binds both term and type variables, however, then free type variables in term signatures are /not/ implicitly bound. For example, this RULE would be ill scoped: {-# RULES "h2" forall b. forall (t :: (b, c)) (g :: forall a. a -> b). h2 t g = ... #-} This is because `b` and `c` occur free in the signature for `t`, but only `b` was explicitly bound, leaving `c` out of scope. If the RULE had started with `forall b c.`, then it would have been accepted. The types in pattern signatures and RULE term binder signatures are represented in the AST by HsSigPatType. From the renamer onward, the hsps_ext field (of type HsPSRn) tracks the names of named wildcards and implicitly bound type variables so that they can be brought into scope during renaming and typechecking. Note [Lexically scoped type variables] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ The ScopedTypeVariables extension does two things: * It allows the use of type signatures in patterns (e.g., `f (x :: a -> a) = ...`). See Note [Pattern signature binders and scoping] for more on this point. * It brings lexically scoped type variables into scope for certain type signatures with outermost invisible 'forall's. This Note concerns the latter bullet point. Per the "Lexically scoped type variables" section of the GHC User's Guide, the following forms of type signatures can have lexically scoped type variables: * In declarations with type signatures, e.g., f :: forall a. a -> a f x = e @a Here, the 'forall a' brings 'a' into scope over the body of 'f'. Note that ScopedTypeVariables does /not/ interact with standalone kind signatures, only type signatures. * In explicit type annotations in expressions, e.g., id @a :: forall a. a -> a * In instance declarations, e.g., instance forall a. C [a] where m = e @a Note that unlike the examples above, the use of an outermost 'forall' isn't required to bring 'a' into scope. That is, the following would also work: instance forall a. C [a] where m = e @a Note that all of the types above obey the forall-or-nothing rule. As a result, the places in the AST that can have lexically scoped type variables are a subset of the places that use HsOuterTyVarBndrs (See Note [forall-or-nothing rule].) Some other observations about lexically scoped type variables: * Only type variables bound by an /invisible/ forall can be lexically scoped. See Note [hsScopedTvs and visible foralls]. * The lexically scoped type variables may be a strict subset of the type variables brought into scope by a type signature. See Note [Binding scoped type variables] in GHC.Tc.Gen.Sig. -} mapHsOuterImplicit :: (XHsOuterImplicit pass -> XHsOuterImplicit pass) -> HsOuterTyVarBndrs flag pass -> HsOuterTyVarBndrs flag pass mapHsOuterImplicit :: forall pass flag. (XHsOuterImplicit pass -> XHsOuterImplicit pass) -> HsOuterTyVarBndrs flag pass -> HsOuterTyVarBndrs flag pass mapHsOuterImplicit XHsOuterImplicit pass -> XHsOuterImplicit pass f (HsOuterImplicit{hso_ximplicit :: forall flag pass. HsOuterTyVarBndrs flag pass -> XHsOuterImplicit pass hso_ximplicit = XHsOuterImplicit pass imp}) = HsOuterImplicit{hso_ximplicit :: XHsOuterImplicit pass hso_ximplicit = XHsOuterImplicit pass -> XHsOuterImplicit pass f XHsOuterImplicit pass imp} mapHsOuterImplicit XHsOuterImplicit pass -> XHsOuterImplicit pass _ hso :: HsOuterTyVarBndrs flag pass hso@(HsOuterExplicit{}) = HsOuterTyVarBndrs flag pass hso mapHsOuterImplicit XHsOuterImplicit pass -> XHsOuterImplicit pass _ hso :: HsOuterTyVarBndrs flag pass hso@(XHsOuterTyVarBndrs{}) = HsOuterTyVarBndrs flag pass hso -------------------------------------------------- -- | These names are used early on to store the names of implicit -- parameters. They completely disappear after type-checking. newtype HsIPName = HsIPName FastString deriving( HsIPName -> HsIPName -> Bool forall a. (a -> a -> Bool) -> (a -> a -> Bool) -> Eq a /= :: HsIPName -> HsIPName -> Bool $c/= :: HsIPName -> HsIPName -> Bool == :: HsIPName -> HsIPName -> Bool $c== :: HsIPName -> HsIPName -> Bool Eq, Typeable HsIPName HsIPName -> DataType HsIPName -> Constr (forall b. Data b => b -> b) -> HsIPName -> HsIPName forall a. Typeable a -> (forall (c :: * -> *). (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> a -> c a) -> (forall (c :: * -> *). (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c a) -> (a -> Constr) -> (a -> DataType) -> (forall (t :: * -> *) (c :: * -> *). Typeable t => (forall d. Data d => c (t d)) -> Maybe (c a)) -> (forall (t :: * -> * -> *) (c :: * -> *). Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c a)) -> ((forall b. Data b => b -> b) -> a -> a) -> (forall r r'. (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> a -> r) -> (forall r r'. (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> a -> r) -> (forall u. (forall d. Data d => d -> u) -> a -> [u]) -> (forall u. Int -> (forall d. Data d => d -> u) -> a -> u) -> (forall (m :: * -> *). Monad m => (forall d. Data d => d -> m d) -> a -> m a) -> (forall (m :: * -> *). MonadPlus m => (forall d. Data d => d -> m d) -> a -> m a) -> (forall (m :: * -> *). MonadPlus m => (forall d. Data d => d -> m d) -> a -> m a) -> Data a forall u. Int -> (forall d. Data d => d -> u) -> HsIPName -> u forall u. (forall d. Data d => d -> u) -> HsIPName -> [u] forall r r'. (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> HsIPName -> r forall r r'. (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> HsIPName -> r forall (m :: * -> *). Monad m => (forall d. Data d => d -> m d) -> HsIPName -> m HsIPName forall (m :: * -> *). MonadPlus m => (forall d. Data d => d -> m d) -> HsIPName -> m HsIPName forall (c :: * -> *). (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c HsIPName forall (c :: * -> *). (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> HsIPName -> c HsIPName forall (t :: * -> *) (c :: * -> *). Typeable t => (forall d. Data d => c (t d)) -> Maybe (c HsIPName) forall (t :: * -> * -> *) (c :: * -> *). Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c HsIPName) gmapMo :: forall (m :: * -> *). MonadPlus m => (forall d. Data d => d -> m d) -> HsIPName -> m HsIPName $cgmapMo :: forall (m :: * -> *). MonadPlus m => (forall d. Data d => d -> m d) -> HsIPName -> m HsIPName gmapMp :: forall (m :: * -> *). MonadPlus m => (forall d. Data d => d -> m d) -> HsIPName -> m HsIPName $cgmapMp :: forall (m :: * -> *). MonadPlus m => (forall d. Data d => d -> m d) -> HsIPName -> m HsIPName gmapM :: forall (m :: * -> *). Monad m => (forall d. Data d => d -> m d) -> HsIPName -> m HsIPName $cgmapM :: forall (m :: * -> *). Monad m => (forall d. Data d => d -> m d) -> HsIPName -> m HsIPName gmapQi :: forall u. Int -> (forall d. Data d => d -> u) -> HsIPName -> u $cgmapQi :: forall u. Int -> (forall d. Data d => d -> u) -> HsIPName -> u gmapQ :: forall u. (forall d. Data d => d -> u) -> HsIPName -> [u] $cgmapQ :: forall u. (forall d. Data d => d -> u) -> HsIPName -> [u] gmapQr :: forall r r'. (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> HsIPName -> r $cgmapQr :: forall r r'. (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> HsIPName -> r gmapQl :: forall r r'. (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> HsIPName -> r $cgmapQl :: forall r r'. (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> HsIPName -> r gmapT :: (forall b. Data b => b -> b) -> HsIPName -> HsIPName $cgmapT :: (forall b. Data b => b -> b) -> HsIPName -> HsIPName dataCast2 :: forall (t :: * -> * -> *) (c :: * -> *). Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c HsIPName) $cdataCast2 :: forall (t :: * -> * -> *) (c :: * -> *). Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c HsIPName) dataCast1 :: forall (t :: * -> *) (c :: * -> *). Typeable t => (forall d. Data d => c (t d)) -> Maybe (c HsIPName) $cdataCast1 :: forall (t :: * -> *) (c :: * -> *). Typeable t => (forall d. Data d => c (t d)) -> Maybe (c HsIPName) dataTypeOf :: HsIPName -> DataType $cdataTypeOf :: HsIPName -> DataType toConstr :: HsIPName -> Constr $ctoConstr :: HsIPName -> Constr gunfold :: forall (c :: * -> *). (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c HsIPName $cgunfold :: forall (c :: * -> *). (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c HsIPName gfoldl :: forall (c :: * -> *). (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> HsIPName -> c HsIPName $cgfoldl :: forall (c :: * -> *). (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> HsIPName -> c HsIPName Data ) hsIPNameFS :: HsIPName -> FastString hsIPNameFS :: HsIPName -> FastString hsIPNameFS (HsIPName FastString n) = FastString n instance Outputable HsIPName where ppr :: HsIPName -> SDoc ppr (HsIPName FastString n) = Char -> SDoc char Char '?' SDoc -> SDoc -> SDoc <> FastString -> SDoc ftext FastString n -- Ordinary implicit parameters instance OutputableBndr HsIPName where pprBndr :: BindingSite -> HsIPName -> SDoc pprBndr BindingSite _ HsIPName n = forall a. Outputable a => a -> SDoc ppr HsIPName n -- Simple for now pprInfixOcc :: HsIPName -> SDoc pprInfixOcc HsIPName n = forall a. Outputable a => a -> SDoc ppr HsIPName n pprPrefixOcc :: HsIPName -> SDoc pprPrefixOcc HsIPName n = forall a. Outputable a => a -> SDoc ppr HsIPName n -------------------------------------------------- -- | Haskell Type Variable Binder -- The flag annotates the binder. It is 'Specificity' in places where -- explicit specificity is allowed (e.g. x :: forall {a} b. ...) or -- '()' in other places. data HsTyVarBndr flag pass = UserTyVar -- no explicit kinding (XUserTyVar pass) flag (LIdP pass) -- See Note [Located RdrNames] in GHC.Hs.Expr | KindedTyVar (XKindedTyVar pass) flag (LIdP pass) (LHsKind pass) -- The user-supplied kind signature -- ^ -- - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnOpen', -- 'GHC.Parser.Annotation.AnnDcolon', 'GHC.Parser.Annotation.AnnClose' -- For details on above see note [exact print annotations] in GHC.Parser.Annotation | XTyVarBndr !(XXTyVarBndr pass) -- | Does this 'HsTyVarBndr' come with an explicit kind annotation? isHsKindedTyVar :: HsTyVarBndr flag pass -> Bool isHsKindedTyVar :: forall flag pass. HsTyVarBndr flag pass -> Bool isHsKindedTyVar (UserTyVar {}) = Bool False isHsKindedTyVar (KindedTyVar {}) = Bool True isHsKindedTyVar (XTyVarBndr {}) = Bool False -- | Haskell Type data HsType pass = HsForAllTy -- See Note [HsType binders] { forall pass. HsType pass -> XForAllTy pass hst_xforall :: XForAllTy pass , forall pass. HsType pass -> HsForAllTelescope pass hst_tele :: HsForAllTelescope pass -- Explicit, user-supplied 'forall a {b} c' , forall pass. HsType pass -> LHsType pass hst_body :: LHsType pass -- body type } -- ^ - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnForall', -- 'GHC.Parser.Annotation.AnnDot','GHC.Parser.Annotation.AnnDarrow' -- For details on above see note [exact print annotations] in "GHC.Parser.Annotation" | HsQualTy -- See Note [HsType binders] { forall pass. HsType pass -> XQualTy pass hst_xqual :: XQualTy pass , forall pass. HsType pass -> Maybe (LHsContext pass) hst_ctxt :: Maybe (LHsContext pass) -- Context C => blah , hst_body :: LHsType pass } | HsTyVar (XTyVar pass) PromotionFlag -- Whether explicitly promoted, -- for the pretty printer (LIdP pass) -- Type variable, type constructor, or data constructor -- see Note [Promotions (HsTyVar)] -- See Note [Located RdrNames] in GHC.Hs.Expr -- ^ - 'GHC.Parser.Annotation.AnnKeywordId' : None -- For details on above see note [exact print annotations] in GHC.Parser.Annotation | HsAppTy (XAppTy pass) (LHsType pass) (LHsType pass) -- ^ - 'GHC.Parser.Annotation.AnnKeywordId' : None -- For details on above see note [exact print annotations] in GHC.Parser.Annotation | HsAppKindTy (XAppKindTy pass) -- type level type app (LHsType pass) (LHsKind pass) | HsFunTy (XFunTy pass) (HsArrow pass) (LHsType pass) -- function type (LHsType pass) -- ^ - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnRarrow', -- For details on above see note [exact print annotations] in GHC.Parser.Annotation | HsListTy (XListTy pass) (LHsType pass) -- Element type -- ^ - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnOpen' @'['@, -- 'GHC.Parser.Annotation.AnnClose' @']'@ -- For details on above see note [exact print annotations] in GHC.Parser.Annotation | HsTupleTy (XTupleTy pass) HsTupleSort [LHsType pass] -- Element types (length gives arity) -- ^ - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnOpen' @'(' or '(#'@, -- 'GHC.Parser.Annotation.AnnClose' @')' or '#)'@ -- For details on above see note [exact print annotations] in GHC.Parser.Annotation | HsSumTy (XSumTy pass) [LHsType pass] -- Element types (length gives arity) -- ^ - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnOpen' @'(#'@, -- 'GHC.Parser.Annotation.AnnClose' '#)'@ -- For details on above see note [exact print annotations] in GHC.Parser.Annotation | HsOpTy (XOpTy pass) (LHsType pass) (LIdP pass) (LHsType pass) -- ^ - 'GHC.Parser.Annotation.AnnKeywordId' : None -- For details on above see note [exact print annotations] in GHC.Parser.Annotation | HsParTy (XParTy pass) (LHsType pass) -- See Note [Parens in HsSyn] in GHC.Hs.Expr -- Parenthesis preserved for the precedence re-arrangement in -- GHC.Rename.HsType -- It's important that a * (b + c) doesn't get rearranged to (a*b) + c! -- ^ - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnOpen' @'('@, -- 'GHC.Parser.Annotation.AnnClose' @')'@ -- For details on above see note [exact print annotations] in GHC.Parser.Annotation | HsIParamTy (XIParamTy pass) (XRec pass HsIPName) -- (?x :: ty) (LHsType pass) -- Implicit parameters as they occur in -- contexts -- ^ -- > (?x :: ty) -- -- - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnDcolon' -- For details on above see note [exact print annotations] in GHC.Parser.Annotation | HsStarTy (XStarTy pass) Bool -- Is this the Unicode variant? -- Note [HsStarTy] -- ^ - 'GHC.Parser.Annotation.AnnKeywordId' : None | HsKindSig (XKindSig pass) (LHsType pass) -- (ty :: kind) (LHsKind pass) -- A type with a kind signature -- ^ -- > (ty :: kind) -- -- - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnOpen' @'('@, -- 'GHC.Parser.Annotation.AnnDcolon','GHC.Parser.Annotation.AnnClose' @')'@ -- For details on above see note [exact print annotations] in GHC.Parser.Annotation | HsSpliceTy (XSpliceTy pass) (HsSplice pass) -- Includes quasi-quotes -- ^ - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnOpen' @'$('@, -- 'GHC.Parser.Annotation.AnnClose' @')'@ -- For details on above see note [exact print annotations] in GHC.Parser.Annotation | HsDocTy (XDocTy pass) (LHsType pass) LHsDocString -- A documented type -- ^ - 'GHC.Parser.Annotation.AnnKeywordId' : None -- For details on above see note [exact print annotations] in GHC.Parser.Annotation | HsBangTy (XBangTy pass) HsSrcBang (LHsType pass) -- Bang-style type annotations -- ^ - 'GHC.Parser.Annotation.AnnKeywordId' : -- 'GHC.Parser.Annotation.AnnOpen' @'{-\# UNPACK' or '{-\# NOUNPACK'@, -- 'GHC.Parser.Annotation.AnnClose' @'#-}'@ -- 'GHC.Parser.Annotation.AnnBang' @\'!\'@ -- For details on above see note [exact print annotations] in GHC.Parser.Annotation | HsRecTy (XRecTy pass) [LConDeclField pass] -- Only in data type declarations -- ^ - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnOpen' @'{'@, -- 'GHC.Parser.Annotation.AnnClose' @'}'@ -- For details on above see note [exact print annotations] in GHC.Parser.Annotation | HsExplicitListTy -- A promoted explicit list (XExplicitListTy pass) PromotionFlag -- whether explicitly promoted, for pretty printer [LHsType pass] -- ^ - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnOpen' @"'["@, -- 'GHC.Parser.Annotation.AnnClose' @']'@ -- For details on above see note [exact print annotations] in GHC.Parser.Annotation | HsExplicitTupleTy -- A promoted explicit tuple (XExplicitTupleTy pass) [LHsType pass] -- ^ - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnOpen' @"'("@, -- 'GHC.Parser.Annotation.AnnClose' @')'@ -- For details on above see note [exact print annotations] in GHC.Parser.Annotation | HsTyLit (XTyLit pass) HsTyLit -- A promoted numeric literal. -- ^ - 'GHC.Parser.Annotation.AnnKeywordId' : None -- For details on above see note [exact print annotations] in GHC.Parser.Annotation | HsWildCardTy (XWildCardTy pass) -- A type wildcard -- See Note [The wildcard story for types] -- ^ - 'GHC.Parser.Annotation.AnnKeywordId' : None -- For details on above see note [exact print annotations] in GHC.Parser.Annotation -- For adding new constructors via Trees that Grow | XHsType !(XXType pass) -- An escape hatch for tunnelling a Core 'Type' through 'HsType'. -- For more details on how this works, see: -- -- * @Note [Renaming HsCoreTys]@ in "GHC.Rename.HsType" -- -- * @Note [Typechecking HsCoreTys]@ in "GHC.Tc.Gen.HsType" type HsCoreTy = Type -- Note [Literal source text] in GHC.Types.Basic for SourceText fields in -- the following -- | Haskell Type Literal data HsTyLit = HsNumTy SourceText Integer | HsStrTy SourceText FastString | HsCharTy SourceText Char deriving Typeable HsTyLit HsTyLit -> DataType HsTyLit -> Constr (forall b. Data b => b -> b) -> HsTyLit -> HsTyLit forall a. Typeable a -> (forall (c :: * -> *). (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> a -> c a) -> (forall (c :: * -> *). (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c a) -> (a -> Constr) -> (a -> DataType) -> (forall (t :: * -> *) (c :: * -> *). Typeable t => (forall d. Data d => c (t d)) -> Maybe (c a)) -> (forall (t :: * -> * -> *) (c :: * -> *). Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c a)) -> ((forall b. Data b => b -> b) -> a -> a) -> (forall r r'. (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> a -> r) -> (forall r r'. (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> a -> r) -> (forall u. (forall d. Data d => d -> u) -> a -> [u]) -> (forall u. Int -> (forall d. Data d => d -> u) -> a -> u) -> (forall (m :: * -> *). Monad m => (forall d. Data d => d -> m d) -> a -> m a) -> (forall (m :: * -> *). MonadPlus m => (forall d. Data d => d -> m d) -> a -> m a) -> (forall (m :: * -> *). MonadPlus m => (forall d. Data d => d -> m d) -> a -> m a) -> Data a forall u. Int -> (forall d. Data d => d -> u) -> HsTyLit -> u forall u. (forall d. Data d => d -> u) -> HsTyLit -> [u] forall r r'. (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> HsTyLit -> r forall r r'. (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> HsTyLit -> r forall (m :: * -> *). Monad m => (forall d. Data d => d -> m d) -> HsTyLit -> m HsTyLit forall (m :: * -> *). MonadPlus m => (forall d. Data d => d -> m d) -> HsTyLit -> m HsTyLit forall (c :: * -> *). (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c HsTyLit forall (c :: * -> *). (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> HsTyLit -> c HsTyLit forall (t :: * -> *) (c :: * -> *). Typeable t => (forall d. Data d => c (t d)) -> Maybe (c HsTyLit) forall (t :: * -> * -> *) (c :: * -> *). Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c HsTyLit) gmapMo :: forall (m :: * -> *). MonadPlus m => (forall d. Data d => d -> m d) -> HsTyLit -> m HsTyLit $cgmapMo :: forall (m :: * -> *). MonadPlus m => (forall d. Data d => d -> m d) -> HsTyLit -> m HsTyLit gmapMp :: forall (m :: * -> *). MonadPlus m => (forall d. Data d => d -> m d) -> HsTyLit -> m HsTyLit $cgmapMp :: forall (m :: * -> *). MonadPlus m => (forall d. Data d => d -> m d) -> HsTyLit -> m HsTyLit gmapM :: forall (m :: * -> *). Monad m => (forall d. Data d => d -> m d) -> HsTyLit -> m HsTyLit $cgmapM :: forall (m :: * -> *). Monad m => (forall d. Data d => d -> m d) -> HsTyLit -> m HsTyLit gmapQi :: forall u. Int -> (forall d. Data d => d -> u) -> HsTyLit -> u $cgmapQi :: forall u. Int -> (forall d. Data d => d -> u) -> HsTyLit -> u gmapQ :: forall u. (forall d. Data d => d -> u) -> HsTyLit -> [u] $cgmapQ :: forall u. (forall d. Data d => d -> u) -> HsTyLit -> [u] gmapQr :: forall r r'. (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> HsTyLit -> r $cgmapQr :: forall r r'. (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> HsTyLit -> r gmapQl :: forall r r'. (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> HsTyLit -> r $cgmapQl :: forall r r'. (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> HsTyLit -> r gmapT :: (forall b. Data b => b -> b) -> HsTyLit -> HsTyLit $cgmapT :: (forall b. Data b => b -> b) -> HsTyLit -> HsTyLit dataCast2 :: forall (t :: * -> * -> *) (c :: * -> *). Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c HsTyLit) $cdataCast2 :: forall (t :: * -> * -> *) (c :: * -> *). Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c HsTyLit) dataCast1 :: forall (t :: * -> *) (c :: * -> *). Typeable t => (forall d. Data d => c (t d)) -> Maybe (c HsTyLit) $cdataCast1 :: forall (t :: * -> *) (c :: * -> *). Typeable t => (forall d. Data d => c (t d)) -> Maybe (c HsTyLit) dataTypeOf :: HsTyLit -> DataType $cdataTypeOf :: HsTyLit -> DataType toConstr :: HsTyLit -> Constr $ctoConstr :: HsTyLit -> Constr gunfold :: forall (c :: * -> *). (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c HsTyLit $cgunfold :: forall (c :: * -> *). (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c HsTyLit gfoldl :: forall (c :: * -> *). (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> HsTyLit -> c HsTyLit $cgfoldl :: forall (c :: * -> *). (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> HsTyLit -> c HsTyLit Data -- | Denotes the type of arrows in the surface language data HsArrow pass = HsUnrestrictedArrow IsUnicodeSyntax -- ^ a -> b or a → b | HsLinearArrow IsUnicodeSyntax (Maybe AddEpAnn) -- ^ a %1 -> b or a %1 → b, or a ⊸ b | HsExplicitMult IsUnicodeSyntax (Maybe AddEpAnn) (LHsType pass) -- ^ a %m -> b or a %m → b (very much including `a %Many -> b`! -- This is how the programmer wrote it). It is stored as an -- `HsType` so as to preserve the syntax as written in the -- program. -- | This is used in the syntax. In constructor declaration. It must keep the -- arrow representation. data HsScaled pass a = HsScaled (HsArrow pass) a hsMult :: HsScaled pass a -> HsArrow pass hsMult :: forall pass a. HsScaled pass a -> HsArrow pass hsMult (HsScaled HsArrow pass m a _) = HsArrow pass m hsScaledThing :: HsScaled pass a -> a hsScaledThing :: forall pass a. HsScaled pass a -> a hsScaledThing (HsScaled HsArrow pass _ a t) = a t -- | When creating syntax we use the shorthands. It's better for printing, also, -- the shorthands work trivially at each pass. hsUnrestricted, hsLinear :: a -> HsScaled pass a hsUnrestricted :: forall a pass. a -> HsScaled pass a hsUnrestricted = forall pass a. HsArrow pass -> a -> HsScaled pass a HsScaled (forall pass. IsUnicodeSyntax -> HsArrow pass HsUnrestrictedArrow IsUnicodeSyntax NormalSyntax) hsLinear :: forall a pass. a -> HsScaled pass a hsLinear = forall pass a. HsArrow pass -> a -> HsScaled pass a HsScaled (forall pass. IsUnicodeSyntax -> Maybe AddEpAnn -> HsArrow pass HsLinearArrow IsUnicodeSyntax NormalSyntax forall a. Maybe a Nothing) instance Outputable a => Outputable (HsScaled pass a) where ppr :: HsScaled pass a -> SDoc ppr (HsScaled HsArrow pass _cnt a t) = -- ppr cnt <> ppr t forall a. Outputable a => a -> SDoc ppr a t {- Note [Unit tuples] ~~~~~~~~~~~~~~~~~~ Consider the type type instance F Int = () We want to parse that "()" as HsTupleTy HsBoxedOrConstraintTuple [], NOT as HsTyVar unitTyCon Why? Because F might have kind (* -> Constraint), so we when parsing we don't know if that tuple is going to be a constraint tuple or an ordinary unit tuple. The HsTupleSort flag is specifically designed to deal with that, but it has to work for unit tuples too. Note [Promotions (HsTyVar)] ~~~~~~~~~~~~~~~~~~~~~~~~~~~ HsTyVar: A name in a type or kind. Here are the allowed namespaces for the name. In a type: Var: not allowed Data: promoted data constructor Tv: type variable TcCls before renamer: type constructor, class constructor, or promoted data constructor TcCls after renamer: type constructor or class constructor In a kind: Var, Data: not allowed Tv: kind variable TcCls: kind constructor or promoted type constructor The 'Promoted' field in an HsTyVar captures whether the type was promoted in the source code by prefixing an apostrophe. Note [HsStarTy] ~~~~~~~~~~~~~~~ When the StarIsType extension is enabled, we want to treat '*' and its Unicode variant identically to 'Data.Kind.Type'. Unfortunately, doing so in the parser would mean that when we pretty-print it back, we don't know whether the user wrote '*' or 'Type', and lose the parse/ppr roundtrip property. As a workaround, we parse '*' as HsStarTy (if it stands for 'Data.Kind.Type') and then desugar it to 'Data.Kind.Type' in the typechecker (see tc_hs_type). When '*' is a regular type operator (StarIsType is disabled), HsStarTy is not involved. Note [Promoted lists and tuples] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Notice the difference between HsListTy HsExplicitListTy HsTupleTy HsExplicitListTupleTy E.g. f :: [Int] HsListTy g3 :: T '[] All these use g2 :: T '[True] HsExplicitListTy g1 :: T '[True,False] g1a :: T [True,False] (can omit ' where unambiguous) kind of T :: [Bool] -> * This kind uses HsListTy! E.g. h :: (Int,Bool) HsTupleTy; f is a pair k :: S '(True,False) HsExplicitTypleTy; S is indexed by a type-level pair of booleans kind of S :: (Bool,Bool) -> * This kind uses HsExplicitTupleTy Note [Distinguishing tuple kinds] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Apart from promotion, tuples can have one of three different kinds: x :: (Int, Bool) -- Regular boxed tuples f :: Int# -> (# Int#, Int# #) -- Unboxed tuples g :: (Eq a, Ord a) => a -- Constraint tuples For convenience, internally we use a single constructor for all of these, namely HsTupleTy, but keep track of the tuple kind (in the first argument to HsTupleTy, a HsTupleSort). We can tell if a tuple is unboxed while parsing, because of the #. However, with -XConstraintKinds we can only distinguish between constraint and boxed tuples during type checking, in general. Hence the two constructors of HsTupleSort: HsUnboxedTuple -> Produced by the parser HsBoxedOrConstraintTuple -> Could be a boxed or a constraint tuple. Produced by the parser only, disappears after type checking After typechecking, we use TupleSort (which clearly distinguishes between constraint tuples and boxed tuples) rather than HsTupleSort. -} -- | Haskell Tuple Sort data HsTupleSort = HsUnboxedTuple | HsBoxedOrConstraintTuple deriving Typeable HsTupleSort HsTupleSort -> DataType HsTupleSort -> Constr (forall b. Data b => b -> b) -> HsTupleSort -> HsTupleSort forall a. Typeable a -> (forall (c :: * -> *). (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> a -> c a) -> (forall (c :: * -> *). (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c a) -> (a -> Constr) -> (a -> DataType) -> (forall (t :: * -> *) (c :: * -> *). Typeable t => (forall d. Data d => c (t d)) -> Maybe (c a)) -> (forall (t :: * -> * -> *) (c :: * -> *). Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c a)) -> ((forall b. Data b => b -> b) -> a -> a) -> (forall r r'. (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> a -> r) -> (forall r r'. (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> a -> r) -> (forall u. (forall d. Data d => d -> u) -> a -> [u]) -> (forall u. Int -> (forall d. Data d => d -> u) -> a -> u) -> (forall (m :: * -> *). Monad m => (forall d. Data d => d -> m d) -> a -> m a) -> (forall (m :: * -> *). MonadPlus m => (forall d. Data d => d -> m d) -> a -> m a) -> (forall (m :: * -> *). MonadPlus m => (forall d. Data d => d -> m d) -> a -> m a) -> Data a forall u. Int -> (forall d. Data d => d -> u) -> HsTupleSort -> u forall u. (forall d. Data d => d -> u) -> HsTupleSort -> [u] forall r r'. (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> HsTupleSort -> r forall r r'. (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> HsTupleSort -> r forall (m :: * -> *). Monad m => (forall d. Data d => d -> m d) -> HsTupleSort -> m HsTupleSort forall (m :: * -> *). MonadPlus m => (forall d. Data d => d -> m d) -> HsTupleSort -> m HsTupleSort forall (c :: * -> *). (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c HsTupleSort forall (c :: * -> *). (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> HsTupleSort -> c HsTupleSort forall (t :: * -> *) (c :: * -> *). Typeable t => (forall d. Data d => c (t d)) -> Maybe (c HsTupleSort) forall (t :: * -> * -> *) (c :: * -> *). Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c HsTupleSort) gmapMo :: forall (m :: * -> *). MonadPlus m => (forall d. Data d => d -> m d) -> HsTupleSort -> m HsTupleSort $cgmapMo :: forall (m :: * -> *). MonadPlus m => (forall d. Data d => d -> m d) -> HsTupleSort -> m HsTupleSort gmapMp :: forall (m :: * -> *). MonadPlus m => (forall d. Data d => d -> m d) -> HsTupleSort -> m HsTupleSort $cgmapMp :: forall (m :: * -> *). MonadPlus m => (forall d. Data d => d -> m d) -> HsTupleSort -> m HsTupleSort gmapM :: forall (m :: * -> *). Monad m => (forall d. Data d => d -> m d) -> HsTupleSort -> m HsTupleSort $cgmapM :: forall (m :: * -> *). Monad m => (forall d. Data d => d -> m d) -> HsTupleSort -> m HsTupleSort gmapQi :: forall u. Int -> (forall d. Data d => d -> u) -> HsTupleSort -> u $cgmapQi :: forall u. Int -> (forall d. Data d => d -> u) -> HsTupleSort -> u gmapQ :: forall u. (forall d. Data d => d -> u) -> HsTupleSort -> [u] $cgmapQ :: forall u. (forall d. Data d => d -> u) -> HsTupleSort -> [u] gmapQr :: forall r r'. (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> HsTupleSort -> r $cgmapQr :: forall r r'. (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> HsTupleSort -> r gmapQl :: forall r r'. (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> HsTupleSort -> r $cgmapQl :: forall r r'. (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> HsTupleSort -> r gmapT :: (forall b. Data b => b -> b) -> HsTupleSort -> HsTupleSort $cgmapT :: (forall b. Data b => b -> b) -> HsTupleSort -> HsTupleSort dataCast2 :: forall (t :: * -> * -> *) (c :: * -> *). Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c HsTupleSort) $cdataCast2 :: forall (t :: * -> * -> *) (c :: * -> *). Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c HsTupleSort) dataCast1 :: forall (t :: * -> *) (c :: * -> *). Typeable t => (forall d. Data d => c (t d)) -> Maybe (c HsTupleSort) $cdataCast1 :: forall (t :: * -> *) (c :: * -> *). Typeable t => (forall d. Data d => c (t d)) -> Maybe (c HsTupleSort) dataTypeOf :: HsTupleSort -> DataType $cdataTypeOf :: HsTupleSort -> DataType toConstr :: HsTupleSort -> Constr $ctoConstr :: HsTupleSort -> Constr gunfold :: forall (c :: * -> *). (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c HsTupleSort $cgunfold :: forall (c :: * -> *). (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c HsTupleSort gfoldl :: forall (c :: * -> *). (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> HsTupleSort -> c HsTupleSort $cgfoldl :: forall (c :: * -> *). (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> HsTupleSort -> c HsTupleSort Data -- | Located Constructor Declaration Field type LConDeclField pass = XRec pass (ConDeclField pass) -- ^ May have 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnComma' when -- in a list -- For details on above see note [exact print annotations] in GHC.Parser.Annotation -- | Constructor Declaration Field data ConDeclField pass -- Record fields have Haddock docs on them = ConDeclField { forall pass. ConDeclField pass -> XConDeclField pass cd_fld_ext :: XConDeclField pass, forall pass. ConDeclField pass -> [LFieldOcc pass] cd_fld_names :: [LFieldOcc pass], -- ^ See Note [ConDeclField passs] forall pass. ConDeclField pass -> LBangType pass cd_fld_type :: LBangType pass, forall pass. ConDeclField pass -> Maybe LHsDocString cd_fld_doc :: Maybe LHsDocString } -- ^ - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnDcolon' -- For details on above see note [exact print annotations] in GHC.Parser.Annotation | XConDeclField !(XXConDeclField pass) -- | Describes the arguments to a data constructor. This is a common -- representation for several constructor-related concepts, including: -- -- * The arguments in a Haskell98-style constructor declaration -- (see 'HsConDeclH98Details' in "GHC.Hs.Decls"). -- -- * The arguments in constructor patterns in @case@/function definitions -- (see 'HsConPatDetails' in "GHC.Hs.Pat"). -- -- * The left-hand side arguments in a pattern synonym binding -- (see 'HsPatSynDetails' in "GHC.Hs.Binds"). -- -- One notable exception is the arguments in a GADT constructor, which uses -- a separate data type entirely (see 'HsConDeclGADTDetails' in -- "GHC.Hs.Decls"). This is because GADT constructors cannot be declared with -- infix syntax, unlike the concepts above (#18844). data HsConDetails tyarg arg rec = PrefixCon [tyarg] [arg] -- C @t1 @t2 p1 p2 p3 | RecCon rec -- C { x = p1, y = p2 } | InfixCon arg arg -- p1 `C` p2 deriving HsConDetails tyarg arg rec -> DataType HsConDetails tyarg arg rec -> Constr forall a. Typeable a -> (forall (c :: * -> *). (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> a -> c a) -> (forall (c :: * -> *). (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c a) -> (a -> Constr) -> (a -> DataType) -> (forall (t :: * -> *) (c :: * -> *). Typeable t => (forall d. Data d => c (t d)) -> Maybe (c a)) -> (forall (t :: * -> * -> *) (c :: * -> *). Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c a)) -> ((forall b. Data b => b -> b) -> a -> a) -> (forall r r'. (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> a -> r) -> (forall r r'. (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> a -> r) -> (forall u. (forall d. Data d => d -> u) -> a -> [u]) -> (forall u. Int -> (forall d. Data d => d -> u) -> a -> u) -> (forall (m :: * -> *). Monad m => (forall d. Data d => d -> m d) -> a -> m a) -> (forall (m :: * -> *). MonadPlus m => (forall d. Data d => d -> m d) -> a -> m a) -> (forall (m :: * -> *). MonadPlus m => (forall d. Data d => d -> m d) -> a -> m a) -> Data a forall {tyarg} {arg} {rec}. (Data tyarg, Data arg, Data rec) => Typeable (HsConDetails tyarg arg rec) forall tyarg arg rec. (Data tyarg, Data arg, Data rec) => HsConDetails tyarg arg rec -> DataType forall tyarg arg rec. (Data tyarg, Data arg, Data rec) => HsConDetails tyarg arg rec -> Constr forall tyarg arg rec. (Data tyarg, Data arg, Data rec) => (forall b. Data b => b -> b) -> HsConDetails tyarg arg rec -> HsConDetails tyarg arg rec forall tyarg arg rec u. (Data tyarg, Data arg, Data rec) => Int -> (forall d. Data d => d -> u) -> HsConDetails tyarg arg rec -> u forall tyarg arg rec u. (Data tyarg, Data arg, Data rec) => (forall d. Data d => d -> u) -> HsConDetails tyarg arg rec -> [u] forall tyarg arg rec r r'. (Data tyarg, Data arg, Data rec) => (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> HsConDetails tyarg arg rec -> r forall tyarg arg rec r r'. (Data tyarg, Data arg, Data rec) => (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> HsConDetails tyarg arg rec -> r forall tyarg arg rec (m :: * -> *). (Data tyarg, Data arg, Data rec, Monad m) => (forall d. Data d => d -> m d) -> HsConDetails tyarg arg rec -> m (HsConDetails tyarg arg rec) forall tyarg arg rec (m :: * -> *). (Data tyarg, Data arg, Data rec, MonadPlus m) => (forall d. Data d => d -> m d) -> HsConDetails tyarg arg rec -> m (HsConDetails tyarg arg rec) forall tyarg arg rec (c :: * -> *). (Data tyarg, Data arg, Data rec) => (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c (HsConDetails tyarg arg rec) forall tyarg arg rec (c :: * -> *). (Data tyarg, Data arg, Data rec) => (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> HsConDetails tyarg arg rec -> c (HsConDetails tyarg arg rec) forall tyarg arg rec (t :: * -> *) (c :: * -> *). (Data tyarg, Data arg, Data rec, Typeable t) => (forall d. Data d => c (t d)) -> Maybe (c (HsConDetails tyarg arg rec)) forall tyarg arg rec (t :: * -> * -> *) (c :: * -> *). (Data tyarg, Data arg, Data rec, Typeable t) => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c (HsConDetails tyarg arg rec)) forall (c :: * -> *). (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c (HsConDetails tyarg arg rec) forall (c :: * -> *). (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> HsConDetails tyarg arg rec -> c (HsConDetails tyarg arg rec) gmapMo :: forall (m :: * -> *). MonadPlus m => (forall d. Data d => d -> m d) -> HsConDetails tyarg arg rec -> m (HsConDetails tyarg arg rec) $cgmapMo :: forall tyarg arg rec (m :: * -> *). (Data tyarg, Data arg, Data rec, MonadPlus m) => (forall d. Data d => d -> m d) -> HsConDetails tyarg arg rec -> m (HsConDetails tyarg arg rec) gmapMp :: forall (m :: * -> *). MonadPlus m => (forall d. Data d => d -> m d) -> HsConDetails tyarg arg rec -> m (HsConDetails tyarg arg rec) $cgmapMp :: forall tyarg arg rec (m :: * -> *). (Data tyarg, Data arg, Data rec, MonadPlus m) => (forall d. Data d => d -> m d) -> HsConDetails tyarg arg rec -> m (HsConDetails tyarg arg rec) gmapM :: forall (m :: * -> *). Monad m => (forall d. Data d => d -> m d) -> HsConDetails tyarg arg rec -> m (HsConDetails tyarg arg rec) $cgmapM :: forall tyarg arg rec (m :: * -> *). (Data tyarg, Data arg, Data rec, Monad m) => (forall d. Data d => d -> m d) -> HsConDetails tyarg arg rec -> m (HsConDetails tyarg arg rec) gmapQi :: forall u. Int -> (forall d. Data d => d -> u) -> HsConDetails tyarg arg rec -> u $cgmapQi :: forall tyarg arg rec u. (Data tyarg, Data arg, Data rec) => Int -> (forall d. Data d => d -> u) -> HsConDetails tyarg arg rec -> u gmapQ :: forall u. (forall d. Data d => d -> u) -> HsConDetails tyarg arg rec -> [u] $cgmapQ :: forall tyarg arg rec u. (Data tyarg, Data arg, Data rec) => (forall d. Data d => d -> u) -> HsConDetails tyarg arg rec -> [u] gmapQr :: forall r r'. (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> HsConDetails tyarg arg rec -> r $cgmapQr :: forall tyarg arg rec r r'. (Data tyarg, Data arg, Data rec) => (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> HsConDetails tyarg arg rec -> r gmapQl :: forall r r'. (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> HsConDetails tyarg arg rec -> r $cgmapQl :: forall tyarg arg rec r r'. (Data tyarg, Data arg, Data rec) => (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> HsConDetails tyarg arg rec -> r gmapT :: (forall b. Data b => b -> b) -> HsConDetails tyarg arg rec -> HsConDetails tyarg arg rec $cgmapT :: forall tyarg arg rec. (Data tyarg, Data arg, Data rec) => (forall b. Data b => b -> b) -> HsConDetails tyarg arg rec -> HsConDetails tyarg arg rec dataCast2 :: forall (t :: * -> * -> *) (c :: * -> *). Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c (HsConDetails tyarg arg rec)) $cdataCast2 :: forall tyarg arg rec (t :: * -> * -> *) (c :: * -> *). (Data tyarg, Data arg, Data rec, Typeable t) => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c (HsConDetails tyarg arg rec)) dataCast1 :: forall (t :: * -> *) (c :: * -> *). Typeable t => (forall d. Data d => c (t d)) -> Maybe (c (HsConDetails tyarg arg rec)) $cdataCast1 :: forall tyarg arg rec (t :: * -> *) (c :: * -> *). (Data tyarg, Data arg, Data rec, Typeable t) => (forall d. Data d => c (t d)) -> Maybe (c (HsConDetails tyarg arg rec)) dataTypeOf :: HsConDetails tyarg arg rec -> DataType $cdataTypeOf :: forall tyarg arg rec. (Data tyarg, Data arg, Data rec) => HsConDetails tyarg arg rec -> DataType toConstr :: HsConDetails tyarg arg rec -> Constr $ctoConstr :: forall tyarg arg rec. (Data tyarg, Data arg, Data rec) => HsConDetails tyarg arg rec -> Constr gunfold :: forall (c :: * -> *). (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c (HsConDetails tyarg arg rec) $cgunfold :: forall tyarg arg rec (c :: * -> *). (Data tyarg, Data arg, Data rec) => (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c (HsConDetails tyarg arg rec) gfoldl :: forall (c :: * -> *). (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> HsConDetails tyarg arg rec -> c (HsConDetails tyarg arg rec) $cgfoldl :: forall tyarg arg rec (c :: * -> *). (Data tyarg, Data arg, Data rec) => (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> HsConDetails tyarg arg rec -> c (HsConDetails tyarg arg rec) Data -- | An empty list that can be used to indicate that there are no -- type arguments allowed in cases where HsConDetails is applied to Void. noTypeArgs :: [Void] noTypeArgs :: [Void] noTypeArgs = [] instance (Outputable tyarg, Outputable arg, Outputable rec) => Outputable (HsConDetails tyarg arg rec) where ppr :: HsConDetails tyarg arg rec -> SDoc ppr (PrefixCon [tyarg] tyargs [arg] args) = String -> SDoc text String "PrefixCon:" SDoc -> SDoc -> SDoc <+> [SDoc] -> SDoc hsep (forall a b. (a -> b) -> [a] -> [b] map (\tyarg t -> String -> SDoc text String "@" SDoc -> SDoc -> SDoc <> forall a. Outputable a => a -> SDoc ppr tyarg t) [tyarg] tyargs) SDoc -> SDoc -> SDoc <+> forall a. Outputable a => a -> SDoc ppr [arg] args ppr (RecCon rec rec) = String -> SDoc text String "RecCon:" SDoc -> SDoc -> SDoc <+> forall a. Outputable a => a -> SDoc ppr rec rec ppr (InfixCon arg l arg r) = String -> SDoc text String "InfixCon:" SDoc -> SDoc -> SDoc <+> forall a. Outputable a => a -> SDoc ppr [arg l, arg r] {- Note [ConDeclField passs] ~~~~~~~~~~~~~~~~~~~~~~~~~ A ConDeclField contains a list of field occurrences: these always include the field label as the user wrote it. After the renamer, it will additionally contain the identity of the selector function in the second component. Due to DuplicateRecordFields, the OccName of the selector function may have been mangled, which is why we keep the original field label separately. For example, when DuplicateRecordFields is enabled data T = MkT { x :: Int } gives ConDeclField { cd_fld_names = [L _ (FieldOcc "x" $sel:x:MkT)], ... }. -} ----------------------- -- A valid type must have a for-all at the top of the type, or of the fn arg -- types --------------------- {- Note [Scoping of named wildcards] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Consider f :: _a -> _a f x = let g :: _a -> _a g = ... in ... Currently, for better or worse, the "_a" variables are all the same. So although there is no explicit forall, the "_a" scopes over the definition. I don't know if this is a good idea, but there it is. -} {- Note [hsScopedTvs and visible foralls] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -XScopedTypeVariables can be defined in terms of a desugaring to -XTypeAbstractions (GHC Proposal #50): fn :: forall a b c. tau(a,b,c) fn :: forall a b c. tau(a,b,c) fn = defn(a,b,c) ==> fn @x @y @z = defn(x,y,z) That is, for every type variable of the leading 'forall' in the type signature, we add an invisible binder at term level. This model does not extend to visible forall, as discussed here: * https://gitlab.haskell.org/ghc/ghc/issues/16734#note_203412 * https://github.com/ghc-proposals/ghc-proposals/pull/238 The conclusion of these discussions can be summarized as follows: > Assuming support for visible 'forall' in terms, consider this example: > > vfn :: forall x y -> tau(x,y) > vfn = \a b -> ... > > The user has written their own binders 'a' and 'b' to stand for 'x' and > 'y', and we definitely should not desugar this into: > > vfn :: forall x y -> tau(x,y) > vfn x y = \a b -> ... -- bad! This design choice is reflected in the design of HsOuterSigTyVarBndrs, which are used in every place that ScopedTypeVariables takes effect: data HsOuterTyVarBndrs flag pass = HsOuterImplicit { ... } | HsOuterExplicit { ..., hso_bndrs :: [LHsTyVarBndr flag pass] } | ... type HsOuterSigTyVarBndrs = HsOuterTyVarBndrs Specificity The HsOuterExplicit constructor is only used in type signatures with outermost, /invisible/ 'forall's. Any other type—including those with outermost, /visible/ 'forall's—will use HsOuterImplicit. Therefore, when we determine which type variables to bring into scope over the body of a function (in hsScopedTvs), we /only/ bring the type variables bound by the hso_bndrs in an HsOuterExplicit into scope. If we have an HsOuterImplicit instead, then we do not bring any type variables into scope over the body of a function at all. At the moment, GHC does not support visible 'forall' in terms. Nevertheless, it is still possible to write erroneous programs that use visible 'forall's in terms, such as this example: x :: forall a -> a -> a x = x Previous versions of GHC would bring `a` into scope over the body of `x` in the hopes that the typechecker would error out later (see `GHC.Tc.Validity.vdqAllowed`). However, this can wreak havoc in the renamer before GHC gets to that point (see #17687 for an example of this). Bottom line: nip problems in the bud by refraining from bringing any type variables in an HsOuterImplicit into scope over the body of a function, even if they correspond to a visible 'forall'. -} {- ************************************************************************ * * Decomposing HsTypes * * ************************************************************************ -} -- Arguments in an expression/type after splitting data HsArg tm ty = HsValArg tm -- Argument is an ordinary expression (f arg) | HsTypeArg SrcSpan ty -- Argument is a visible type application (f @ty) -- SrcSpan is location of the `@` | HsArgPar SrcSpan -- See Note [HsArgPar] numVisibleArgs :: [HsArg tm ty] -> Arity numVisibleArgs :: forall tm ty. [HsArg tm ty] -> Int numVisibleArgs = forall a. (a -> Bool) -> [a] -> Int count forall {tm} {ty}. HsArg tm ty -> Bool is_vis where is_vis :: HsArg tm ty -> Bool is_vis (HsValArg tm _) = Bool True is_vis HsArg tm ty _ = Bool False -- type level equivalent type LHsTypeArg p = HsArg (LHsType p) (LHsKind p) instance (Outputable tm, Outputable ty) => Outputable (HsArg tm ty) where ppr :: HsArg tm ty -> SDoc ppr (HsValArg tm tm) = forall a. Outputable a => a -> SDoc ppr tm tm ppr (HsTypeArg SrcSpan _ ty ty) = Char -> SDoc char Char '@' SDoc -> SDoc -> SDoc <> forall a. Outputable a => a -> SDoc ppr ty ty ppr (HsArgPar SrcSpan sp) = String -> SDoc text String "HsArgPar" SDoc -> SDoc -> SDoc <+> forall a. Outputable a => a -> SDoc ppr SrcSpan sp {- Note [HsArgPar] A HsArgPar indicates that everything to the left of this in the argument list is enclosed in parentheses together with the function itself. It is necessary so that we can recreate the parenthesis structure in the original source after typechecking the arguments. The SrcSpan is the span of the original HsPar ((f arg1) arg2 arg3) results in an input argument list of [HsValArg arg1, HsArgPar span1, HsValArg arg2, HsValArg arg3, HsArgPar span2] -} -------------------------------- {- ************************************************************************ * * FieldOcc * * ************************************************************************ -} -- | Located Field Occurrence type LFieldOcc pass = XRec pass (FieldOcc pass) -- | Field Occurrence -- -- Represents an *occurrence* of an unambiguous field. This may or may not be a -- binding occurrence (e.g. this type is used in 'ConDeclField' and -- 'RecordPatSynField' which bind their fields, but also in 'HsRecField' for -- record construction and patterns, which do not). -- -- We store both the 'RdrName' the user originally wrote, and after the renamer, -- the selector function. data FieldOcc pass = FieldOcc { forall pass. FieldOcc pass -> XCFieldOcc pass extFieldOcc :: XCFieldOcc pass , forall pass. FieldOcc pass -> LocatedN RdrName rdrNameFieldOcc :: LocatedN RdrName -- ^ See Note [Located RdrNames] in "GHC.Hs.Expr" } | XFieldOcc !(XXFieldOcc pass) deriving instance (Eq (XCFieldOcc pass), Eq (XXFieldOcc pass)) => Eq (FieldOcc pass) instance Outputable (FieldOcc pass) where ppr :: FieldOcc pass -> SDoc ppr = forall a. Outputable a => a -> SDoc ppr forall b c a. (b -> c) -> (a -> b) -> a -> c . forall pass. FieldOcc pass -> LocatedN RdrName rdrNameFieldOcc instance OutputableBndr (FieldOcc pass) where pprInfixOcc :: FieldOcc pass -> SDoc pprInfixOcc = forall a. OutputableBndr a => a -> SDoc pprInfixOcc forall b c a. (b -> c) -> (a -> b) -> a -> c . forall l e. GenLocated l e -> e unLoc forall b c a. (b -> c) -> (a -> b) -> a -> c . forall pass. FieldOcc pass -> LocatedN RdrName rdrNameFieldOcc pprPrefixOcc :: FieldOcc pass -> SDoc pprPrefixOcc = forall a. OutputableBndr a => a -> SDoc pprPrefixOcc forall b c a. (b -> c) -> (a -> b) -> a -> c . forall l e. GenLocated l e -> e unLoc forall b c a. (b -> c) -> (a -> b) -> a -> c . forall pass. FieldOcc pass -> LocatedN RdrName rdrNameFieldOcc instance OutputableBndr (GenLocated SrcSpan (FieldOcc pass)) where pprInfixOcc :: GenLocated SrcSpan (FieldOcc pass) -> SDoc pprInfixOcc = forall a. OutputableBndr a => a -> SDoc pprInfixOcc forall b c a. (b -> c) -> (a -> b) -> a -> c . forall l e. GenLocated l e -> e unLoc pprPrefixOcc :: GenLocated SrcSpan (FieldOcc pass) -> SDoc pprPrefixOcc = forall a. OutputableBndr a => a -> SDoc pprPrefixOcc forall b c a. (b -> c) -> (a -> b) -> a -> c . forall l e. GenLocated l e -> e unLoc -- | Ambiguous Field Occurrence -- -- Represents an *occurrence* of a field that is potentially -- ambiguous after the renamer, with the ambiguity resolved by the -- typechecker. We always store the 'RdrName' that the user -- originally wrote, and store the selector function after the renamer -- (for unambiguous occurrences) or the typechecker (for ambiguous -- occurrences). -- -- See Note [HsRecField and HsRecUpdField] in "GHC.Hs.Pat" and -- Note [Disambiguating record fields] in "GHC.Tc.Gen.Head". -- See Note [Located RdrNames] in "GHC.Hs.Expr" data AmbiguousFieldOcc pass = Unambiguous (XUnambiguous pass) (LocatedN RdrName) | Ambiguous (XAmbiguous pass) (LocatedN RdrName) | XAmbiguousFieldOcc !(XXAmbiguousFieldOcc pass) {- ************************************************************************ * * \subsection{Pretty printing} * * ************************************************************************ -} instance Outputable HsTyLit where ppr :: HsTyLit -> SDoc ppr = HsTyLit -> SDoc ppr_tylit -------------------------- ppr_tylit :: HsTyLit -> SDoc ppr_tylit :: HsTyLit -> SDoc ppr_tylit (HsNumTy SourceText source Integer i) = SourceText -> SDoc -> SDoc pprWithSourceText SourceText source (Integer -> SDoc integer Integer i) ppr_tylit (HsStrTy SourceText source FastString s) = SourceText -> SDoc -> SDoc pprWithSourceText SourceText source (String -> SDoc text (forall a. Show a => a -> String show FastString s)) ppr_tylit (HsCharTy SourceText source Char c) = SourceText -> SDoc -> SDoc pprWithSourceText SourceText source (String -> SDoc text (forall a. Show a => a -> String show Char c))