hieFile/HieTypes.hs

    {-# LANGUAGE DeriveTraversable #-}
    {-# LANGUAGE DeriveDataTypeable #-}
    {-# LANGUAGE TypeSynonymInstances #-}
    {-# LANGUAGE FlexibleInstances #-}
    {-# LANGUAGE ScopedTypeVariables #-}
    module HieTypes where

    import GhcPrelude

    import Binary
    import FastString                 ( FastString )
    import IfaceType
    import Module                     ( ModuleName, Module )
    import Name                       ( Name )
    import Outputable hiding ( (<>) )
    import SrcLoc                     ( RealSrcSpan )
    import Avail

    import qualified Data.Array as A
    import qualified Data.Map as M
    import qualified Data.Set as S
    import Data.ByteString            ( ByteString )
    import Data.Data                  ( Typeable, Data )
    import Data.Semigroup             ( Semigroup(..) )
    import Data.Word                  ( Word8 )
    import Control.Applicative        ( (<|>) )

    type Span = RealSrcSpan

    -- | Current version of @.hie@ files
    curHieVersion :: Word8
    curHieVersion = 0

    {- |
    GHC builds up a wealth of information about Haskell source as it compiles it.
    @.hie@ files are a way of persisting some of this information to disk so that
    external tools that need to work with haskell source don't need to parse,
    typecheck, and rename all over again. These files contain:

      * a simplified AST

           * nodes are annotated with source positions and types
           * identifiers are annotated with scope information

      * the raw bytes of the initial Haskell source

    Besides saving compilation cycles, @.hie@ files also offer a more stable
    interface than the GHC API.
    -}
    data HieFile = HieFile
        { hie_version :: Word8
        -- ^ version of the HIE format

        , hie_ghc_version :: ByteString
        -- ^ Version of GHC that produced this file

        , hie_hs_file :: FilePath
        -- ^ Initial Haskell source file path

        , hie_module :: Module
        -- ^ The module this HIE file is for

        , hie_types :: A.Array TypeIndex HieTypeFlat
        -- ^ Types referenced in the 'hie_asts'.
        --
        -- See Note [Efficient serialization of redundant type info]

        , hie_asts :: HieASTs TypeIndex
        -- ^ Type-annotated abstract syntax trees

        , hie_exports :: [AvailInfo]
        -- ^ The names that this module exports

        , hie_hs_src :: ByteString
        -- ^ Raw bytes of the initial Haskell source
        }

    instance Binary HieFile where
      put_ bh hf = do
        put_ bh $ hie_version hf
        put_ bh $ hie_ghc_version hf
        put_ bh $ hie_hs_file hf
        put_ bh $ hie_module hf
        put_ bh $ hie_types hf
        put_ bh $ hie_asts hf
        put_ bh $ hie_exports hf
        put_ bh $ hie_hs_src hf

      get bh = HieFile
        <$> get bh
        <*> get bh
        <*> get bh
        <*> get bh
        <*> get bh
        <*> get bh
        <*> get bh
        <*> get bh

    {-
    Note [Efficient serialization of redundant type info]
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

    The type information in .hie files is highly repetitive and redundant. For
    example, consider the expression

        const True 'a'

    There is a lot of shared structure between the types of subterms:

      * const True 'a' ::                 Bool
      * const True     ::         Char -> Bool
      * const          :: Bool -> Char -> Bool

    Since all 3 of these types need to be stored in the .hie file, it is worth
    making an effort to deduplicate this shared structure. The trick is to define
    a new data type that is a flattened version of 'Type':

        data HieType a = HAppTy a a  -- data Type = AppTy Type Type
                       | HFunTy a a  --           | FunTy Type Type
                       | ...

        type TypeIndex = Int

    Types in the final AST are stored in an 'A.Array TypeIndex (HieType TypeIndex)',
    where the 'TypeIndex's in the 'HieType' are references to other elements of the
    array. Types recovered from GHC are deduplicated and stored in this compressed
    form with sharing of subtrees.
    -}

    type TypeIndex = Int

    -- | A flattened version of 'Type'.
    --
    -- See Note [Efficient serialization of redundant type info]
    data HieType a
      = HTyVarTy Name
      | HAppTy a (HieArgs a)
      | HTyConApp IfaceTyCon (HieArgs a)
      | HForAllTy ((Name, a),ArgFlag) a
      | HFunTy  a a
      | HQualTy a a           -- ^ type with constraint: @t1 => t2@ (see 'IfaceDFunTy')
      | HLitTy IfaceTyLit
      | HCastTy a
      | HCoercionTy
        deriving (Functor, Foldable, Traversable, Eq)

    type HieTypeFlat = HieType TypeIndex

    -- | Roughly isomorphic to the original core 'Type'.
    newtype HieTypeFix = Roll (HieType (HieTypeFix))

    instance Binary (HieType TypeIndex) where
      put_ bh (HTyVarTy n) = do
        putByte bh 0
        put_ bh n
      put_ bh (HAppTy a b) = do
        putByte bh 1
        put_ bh a
        put_ bh b
      put_ bh (HTyConApp n xs) = do
        putByte bh 2
        put_ bh n
        put_ bh xs
      put_ bh (HForAllTy bndr a) = do
        putByte bh 3
        put_ bh bndr
        put_ bh a
      put_ bh (HFunTy a b) = do
        putByte bh 4
        put_ bh a
        put_ bh b
      put_ bh (HQualTy a b) = do
        putByte bh 5
        put_ bh a
        put_ bh b
      put_ bh (HLitTy l) = do
        putByte bh 6
        put_ bh l
      put_ bh (HCastTy a) = do
        putByte bh 7
        put_ bh a
      put_ bh (HCoercionTy) = putByte bh 8

      get bh = do
        (t :: Word8) <- get bh
        case t of
          0 -> HTyVarTy <$> get bh
          1 -> HAppTy <$> get bh <*> get bh
          2 -> HTyConApp <$> get bh <*> get bh
          3 -> HForAllTy <$> get bh <*> get bh
          4 -> HFunTy <$> get bh <*> get bh
          5 -> HQualTy <$> get bh <*> get bh
          6 -> HLitTy <$> get bh
          7 -> HCastTy <$> get bh
          8 -> return HCoercionTy
          _ -> panic "Binary (HieArgs Int): invalid tag"

    -- | A list of type arguments along with their respective visibilities (ie. is
    -- this an argument that would return 'True' for 'isVisibleArgFlag'?).
    newtype HieArgs a = HieArgs [(Bool,a)]
      deriving (Functor, Foldable, Traversable, Eq)

    instance Binary (HieArgs TypeIndex) where
      put_ bh (HieArgs xs) = put_ bh xs
      get bh = HieArgs <$> get bh

    -- | Mapping from filepaths (represented using 'FastString') to the
    -- corresponding AST
    newtype HieASTs a = HieASTs { getAsts :: (M.Map FastString (HieAST a)) }
      deriving (Functor, Foldable, Traversable)

    instance Binary (HieASTs TypeIndex) where
      put_ bh asts = put_ bh $ M.toAscList $ getAsts asts
      get bh = HieASTs <$> fmap M.fromDistinctAscList (get bh)

    data HieAST a =
      Node
        { nodeInfo :: NodeInfo a
        , nodeSpan :: Span
        , nodeChildren :: [HieAST a]
        } deriving (Functor, Foldable, Traversable)

    instance Binary (HieAST TypeIndex) where
      put_ bh ast = do
        put_ bh $ nodeInfo ast
        put_ bh $ nodeSpan ast
        put_ bh $ nodeChildren ast

      get bh = Node
        <$> get bh
        <*> get bh
        <*> get bh

    -- | The information stored in one AST node.
    --
    -- The type parameter exists to provide flexibility in representation of types
    -- (see Note [Efficient serialization of redundant type info]).
    data NodeInfo a = NodeInfo
        { nodeAnnotations :: S.Set (FastString,FastString)
        -- ^ (name of the AST node constructor, name of the AST node Type)

        , nodeType :: [a]
        -- ^ The Haskell types of this node, if any.

        , nodeIdentifiers :: NodeIdentifiers a
        -- ^ All the identifiers and their details
        } deriving (Functor, Foldable, Traversable)

    instance Binary (NodeInfo TypeIndex) where
      put_ bh ni = do
        put_ bh $ S.toAscList $ nodeAnnotations ni
        put_ bh $ nodeType ni
        put_ bh $ M.toList $ nodeIdentifiers ni
      get bh = NodeInfo
        <$> fmap (S.fromDistinctAscList) (get bh)
        <*> get bh
        <*> fmap (M.fromList) (get bh)

    type Identifier = Either ModuleName Name

    type NodeIdentifiers a = M.Map Identifier (IdentifierDetails a)

    -- | Information associated with every identifier
    --
    -- We need to include types with identifiers because sometimes multiple
    -- identifiers occur in the same span(Overloaded Record Fields and so on)
    data IdentifierDetails a = IdentifierDetails
      { identType :: Maybe a
      , identInfo :: S.Set ContextInfo
      } deriving (Eq, Functor, Foldable, Traversable)

    instance Outputable a => Outputable (IdentifierDetails a) where
      ppr x = text "IdentifierDetails" <+> ppr (identType x) <+> ppr (identInfo x)

    instance Semigroup (IdentifierDetails a) where
      d1 <> d2 = IdentifierDetails (identType d1 <|> identType d2)
                                   (S.union (identInfo d1) (identInfo d2))

    instance Monoid (IdentifierDetails a) where
      mempty = IdentifierDetails Nothing S.empty

    instance Binary (IdentifierDetails TypeIndex) where
      put_ bh dets = do
        put_ bh $ identType dets
        put_ bh $ S.toAscList $ identInfo dets
      get bh =  IdentifierDetails
        <$> get bh
        <*> fmap (S.fromDistinctAscList) (get bh)

    -- | Different contexts under which identifiers exist
    data ContextInfo
      = Use                -- ^ regular variable
      | MatchBind
      | IEThing IEType     -- ^ import/export
      | TyDecl

      -- | Value binding
      | ValBind
          BindType     -- ^ whether or not the binding is in an instance
          Scope        -- ^ scope over which the value is bound
          (Maybe Span) -- ^ span of entire binding

      -- | Pattern binding
      --
      -- This case is tricky because the bound identifier can be used in two
      -- distinct scopes. Consider the following example (with @-XViewPatterns@)
      --
      -- @
      -- do (b, a, (a -> True)) <- bar
      --    foo a
      -- @
      --
      -- The identifier @a@ has two scopes: in the view pattern @(a -> True)@ and
      -- in the rest of the @do@-block in @foo a@.
      | PatternBind
          Scope        -- ^ scope /in the pattern/ (the variable bound can be used
                       -- further in the pattern)
          Scope        -- ^ rest of the scope outside the pattern
          (Maybe Span) -- ^ span of entire binding

      | ClassTyDecl (Maybe Span)

      -- | Declaration
      | Decl
          DeclType     -- ^ type of declaration
          (Maybe Span) -- ^ span of entire binding

      -- | Type variable
      | TyVarBind Scope TyVarScope

      -- | Record field
      | RecField RecFieldContext (Maybe Span)
        deriving (Eq, Ord, Show)

    instance Outputable ContextInfo where
      ppr = text . show

    instance Binary ContextInfo where
      put_ bh Use = putByte bh 0
      put_ bh (IEThing t) = do
        putByte bh 1
        put_ bh t
      put_ bh TyDecl = putByte bh 2
      put_ bh (ValBind bt sc msp) = do
        putByte bh 3
        put_ bh bt
        put_ bh sc
        put_ bh msp
      put_ bh (PatternBind a b c) = do
        putByte bh 4
        put_ bh a
        put_ bh b
        put_ bh c
      put_ bh (ClassTyDecl sp) = do
        putByte bh 5
        put_ bh sp
      put_ bh (Decl a b) = do
        putByte bh 6
        put_ bh a
        put_ bh b
      put_ bh (TyVarBind a b) = do
        putByte bh 7
        put_ bh a
        put_ bh b
      put_ bh (RecField a b) = do
        putByte bh 8
        put_ bh a
        put_ bh b
      put_ bh MatchBind = putByte bh 9

      get bh = do
        (t :: Word8) <- get bh
        case t of
          0 -> return Use
          1 -> IEThing <$> get bh
          2 -> return TyDecl
          3 -> ValBind <$> get bh <*> get bh <*> get bh
          4 -> PatternBind <$> get bh <*> get bh <*> get bh
          5 -> ClassTyDecl <$> get bh
          6 -> Decl <$> get bh <*> get bh
          7 -> TyVarBind <$> get bh <*> get bh
          8 -> RecField <$> get bh <*> get bh
          9 -> return MatchBind
          _ -> panic "Binary ContextInfo: invalid tag"

    -- | Types of imports and exports
    data IEType
      = Import
      | ImportAs
      | ImportHiding
      | Export
        deriving (Eq, Enum, Ord, Show)

    instance Binary IEType where
      put_ bh b = putByte bh (fromIntegral (fromEnum b))
      get bh = do x <- getByte bh; pure $! (toEnum (fromIntegral x))

    data RecFieldContext
      = RecFieldDecl
      | RecFieldAssign
      | RecFieldMatch
      | RecFieldOcc
        deriving (Eq, Enum, Ord, Show)

    instance Binary RecFieldContext where
      put_ bh b = putByte bh (fromIntegral (fromEnum b))
      get bh = do x <- getByte bh; pure $! (toEnum (fromIntegral x))

    data BindType
      = RegularBind
      | InstanceBind
        deriving (Eq, Ord, Show, Enum)

    instance Binary BindType where
      put_ bh b = putByte bh (fromIntegral (fromEnum b))
      get bh = do x <- getByte bh; pure $! (toEnum (fromIntegral x))

    data DeclType
      = FamDec     -- ^ type or data family
      | SynDec     -- ^ type synonym
      | DataDec    -- ^ data declaration
      | ConDec     -- ^ constructor declaration
      | PatSynDec  -- ^ pattern synonym
      | ClassDec   -- ^ class declaration
      | InstDec    -- ^ instance declaration
        deriving (Eq, Ord, Show, Enum)

    instance Binary DeclType where
      put_ bh b = putByte bh (fromIntegral (fromEnum b))
      get bh = do x <- getByte bh; pure $! (toEnum (fromIntegral x))

    data Scope
      = NoScope
      | LocalScope Span
      | ModuleScope
        deriving (Eq, Ord, Show, Typeable, Data)

    instance Outputable Scope where
      ppr NoScope = text "NoScope"
      ppr (LocalScope sp) = text "LocalScope" <+> ppr sp
      ppr ModuleScope = text "ModuleScope"

    instance Binary Scope where
      put_ bh NoScope = putByte bh 0
      put_ bh (LocalScope span) = do
        putByte bh 1
        put_ bh span
      put_ bh ModuleScope = putByte bh 2

      get bh = do
        (t :: Word8) <- get bh
        case t of
          0 -> return NoScope
          1 -> LocalScope <$> get bh
          2 -> return ModuleScope
          _ -> panic "Binary Scope: invalid tag"

    -- | Scope of a type variable.
    --
    -- This warrants a data type apart from 'Scope' because of complexities
    -- introduced by features like @-XScopedTypeVariables@ and @-XInstanceSigs@. For
    -- example, consider:
    --
    -- @
    -- foo, bar, baz :: forall a. a -> a
    -- @
    --
    -- Here @a@ is in scope in all the definitions of @foo@, @bar@, and @baz@, so we
    -- need a list of scopes to keep track of this. Furthermore, this list cannot be
    -- computed until we resolve the binding sites of @foo@, @bar@, and @baz@.
    --
    -- Consequently, @a@ starts with an @'UnresolvedScope' [foo, bar, baz] Nothing@
    -- which later gets resolved into a 'ResolvedScopes'.
    data TyVarScope
      = ResolvedScopes [Scope]

      -- | Unresolved scopes should never show up in the final @.hie@ file
      | UnresolvedScope
            [Name]        -- ^ names of the definitions over which the scope spans
            (Maybe Span)  -- ^ the location of the instance/class declaration for
                          -- the case where the type variable is declared in a
                          -- method type signature
        deriving (Eq, Ord)

    instance Show TyVarScope where
      show (ResolvedScopes sc) = show sc
      show _ = error "UnresolvedScope"

    instance Binary TyVarScope where
      put_ bh (ResolvedScopes xs) = do
        putByte bh 0
        put_ bh xs
      put_ bh (UnresolvedScope ns span) = do
        putByte bh 1
        put_ bh ns
        put_ bh span

      get bh = do
        (t :: Word8) <- get bh
        case t of
          0 -> ResolvedScopes <$> get bh
          1 -> UnresolvedScope <$> get bh <*> get bh
          _ -> panic "Binary TyVarScope: invalid tag"