Imports.hs 23.6 KB
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{- |
    Module      :  $Header$
    Description :  Importing interface declarations
    Copyright   :  (c) 2000-2003, Wolfgang Lux
                       2011, Björn Peemöller (bjp@informatik.uni-kiel.de)
    License     :  OtherLicense

    Maintainer  :  bjp@informatik.uni-kiel.de
    Stability   :  experimental
    Portability :  portable

    This module provides the function 'importModules' to bring the imported
    entities into the module's scope, and the function 'qualifyEnv' to
    qualify the environment prior to computing the export interface.
-}
module Imports (importModules, qualifyEnv) where

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import Control.Monad (liftM, unless)
import qualified Control.Monad.State as S (State, gets, modify, runState)
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import qualified Data.Map as Map
import Data.Maybe
import qualified Data.Set as Set

import Curry.Base.Ident
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import Curry.Base.Position
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import Curry.Syntax

import Base.CurryTypes (toQualType, toQualTypes)
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import Base.Messages (Message, errorMessages, posMsg, internalError)
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import Base.TopEnv
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import Base.Types
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import Base.TypeSubst (expandAliasType)
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import Env.Interface
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import Env.ModuleAlias (importAliases)
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import Env.OpPrec
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import Env.TypeConstructor
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import Env.Value

import CompilerEnv
import CompilerOpts

-- |The function 'importModules' brings the declarations of all
-- imported interfaces into scope for the current module.
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importModules :: Options -> Module -> InterfaceEnv -> CompilerEnv
importModules opts (Module mid _ imps _) iEnv
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  = expandTCValueEnv opts
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  $ importUnifyData
  $ foldl importModule initEnv imps
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  where
    initEnv = (initCompilerEnv mid)
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      { aliasEnv     = importAliases     imps -- import module aliases
      , interfaceEnv = iEnv                   -- imported interfaces
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      }
    importModule env (ImportDecl _ m q asM is) = case Map.lookup m iEnv of
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      Just intf -> importInterface (fromMaybe m asM) q is intf env
      Nothing   -> internalError $ "Imports.importModules: no interface for "
                                   ++ show m
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-- ---------------------------------------------------------------------------
-- Importing an interface into the module
-- ---------------------------------------------------------------------------

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-- Three kinds of environments are computed from the interface:
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--
-- 1. The operator precedences
-- 2. The type constructors
-- 3. The types of the data constructors and functions (values)
--
-- Note that the original names of all entities defined in the imported module
-- are qualified appropriately. The same is true for type expressions.

type IdentMap    = Map.Map Ident

type ExpPEnv     = IdentMap PrecInfo
type ExpTCEnv    = IdentMap TypeInfo
type ExpValueEnv = IdentMap ValueInfo

-- When an interface is imported, the compiler first transforms the
-- interface into these environments. If an import specification is
-- present, the environments are restricted to only those entities which
-- are included in the specification or not hidden by it, respectively.
-- The resulting environments are then imported into the current module
-- using either a qualified import (if the module is imported qualified)
-- or both a qualified and an unqualified import (non-qualified import).

importInterface :: ModuleIdent -> Bool -> Maybe ImportSpec -> Interface
                -> CompilerEnv -> CompilerEnv
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importInterface m q is i env
  | not (null errs) = errorMessages errs
  | otherwise       = env
    { opPrecEnv = importEntities m q vs id              mPEnv  $ opPrecEnv env
    , tyConsEnv = importEntities m q ts (importData vs) mTCEnv $ tyConsEnv env
    , valueEnv  = importEntities m q vs id              mTyEnv $ valueEnv  env
    }
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  where
  mPEnv  = intfEnv bindPrec i -- all operator precedences
  mTCEnv = intfEnv bindTC   i -- all type constructors
  mTyEnv = intfEnv bindTy   i -- all values
  -- all imported type constructors / values
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  (expandedSpec, errs) = runExpand (expandSpecs is) m mTCEnv mTyEnv
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  ts = isVisible is (Set.fromList $ foldr addType  [] expandedSpec)
  vs = isVisible is (Set.fromList $ foldr addValue [] expandedSpec)
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addType :: Import -> [Ident] -> [Ident]
addType (Import            _) tcs = tcs
addType (ImportTypeWith tc _) tcs = tc : tcs
addType (ImportTypeAll     _) _   = internalError "Imports.addType"

addValue :: Import -> [Ident] -> [Ident]
addValue (Import            f) fs = f : fs
addValue (ImportTypeWith _ cs) fs = cs ++ fs
addValue (ImportTypeAll     _) _  = internalError "Imports.addValue"

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isVisible :: Maybe ImportSpec -> Set.Set Ident -> Ident -> Bool
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isVisible Nothing                _  = const True
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isVisible (Just (Importing _ _)) xs = (`Set.member`    xs)
isVisible (Just (Hiding    _ _)) xs = (`Set.notMember` xs)

importEntities :: Entity a => ModuleIdent -> Bool -> (Ident -> Bool)
               -> (a -> a) -> IdentMap a -> TopEnv a -> TopEnv a
importEntities m q isVisible' f mEnv env =
  foldr (uncurry (if q then qualImportTopEnv m else importUnqual m)) env
        [(x,f y) | (x,y) <- Map.toList mEnv, isVisible' x]
  where importUnqual m' x y = importTopEnv m' x y . qualImportTopEnv m' x y

importData :: (Ident -> Bool) -> TypeInfo -> TypeInfo
importData isVisible' (DataType tc n cs) =
  DataType tc n (map (>>= importConstr isVisible') cs)
importData isVisible' (RenamingType tc n nc) =
  maybe (DataType tc n []) (RenamingType tc n) (importConstr isVisible' nc)
importData _ (AliasType tc n ty) = AliasType tc n ty

importConstr :: (Ident -> Bool) -> DataConstr -> Maybe DataConstr
importConstr isVisible' dc@(DataConstr c _ _)
  | isVisible' c = Just dc
  | otherwise    = Nothing

-- ---------------------------------------------------------------------------
-- Building the initial environment
-- ---------------------------------------------------------------------------

-- In a first step, the four export environments are initialized from
-- the interface's declarations. This step also qualifies the names of
-- all entities defined in (but not imported into) the interface with its
-- module name.

intfEnv :: (ModuleIdent -> IDecl -> IdentMap a -> IdentMap a)
        -> Interface -> IdentMap a
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intfEnv bind (Interface m _ ds) = foldr (bind m) Map.empty ds
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-- operator precedences
bindPrec :: ModuleIdent -> IDecl -> ExpPEnv -> ExpPEnv
bindPrec m (IInfixDecl _ fix p op) =
  Map.insert (unqualify op) (PrecInfo (qualQualify m op) (OpPrec fix p))
bindPrec _ _ = id

bindTCHidden :: ModuleIdent -> IDecl -> ExpTCEnv -> ExpTCEnv
bindTCHidden m (HidingDataDecl _ tc tvs) =
  bindType DataType m (qualify tc) tvs []
bindTCHidden m d = bindTC m d

-- type constructors
bindTC :: ModuleIdent -> IDecl -> ExpTCEnv -> ExpTCEnv
bindTC m (IDataDecl _ tc tvs cs) mTCEnv
  | unqualify tc `Map.member` mTCEnv = mTCEnv
  | otherwise = bindType DataType m tc tvs (map (fmap mkData) cs) mTCEnv
  where
   mkData (ConstrDecl _ evs c tys) =
     DataConstr c (length evs) (toQualTypes m tvs tys)
   mkData (ConOpDecl _ evs ty1 c ty2) =
     DataConstr c (length evs) (toQualTypes m tvs [ty1,ty2])

bindTC m (INewtypeDecl _ tc tvs (NewConstrDecl _ evs c ty)) mTCEnv =
  bindType RenamingType m tc tvs
 (DataConstr c (length evs) [toQualType m tvs ty]) mTCEnv

bindTC m (ITypeDecl _ tc tvs ty) mTCEnv
  | isRecordExtId tc' =
    bindType AliasType m (qualify (fromRecordExtId tc')) tvs
   (toQualType m tvs ty) mTCEnv
  | otherwise =
    bindType AliasType m tc tvs (toQualType m tvs ty) mTCEnv
  where tc' = unqualify tc

bindTC _ _ mTCEnv = mTCEnv

bindType :: (QualIdent -> Int -> a -> TypeInfo) -> ModuleIdent -> QualIdent
         -> [Ident] -> a -> ExpTCEnv -> ExpTCEnv
bindType f m tc tvs = Map.insert (unqualify tc)
                    . f (qualQualify m tc) (length tvs)

-- functions and data constructors
bindTy :: ModuleIdent -> IDecl -> ExpValueEnv -> ExpValueEnv
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bindTy m (IDataDecl _ tc tvs cs) env =
  foldr (bindConstr m tc' tvs $ constrType tc' tvs) env $ catMaybes cs
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  where tc' = qualQualify m tc
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bindTy m (INewtypeDecl _ tc tvs nc) env =
  bindNewConstr m tc' tvs (constrType tc' tvs) nc env
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  where tc' = qualQualify m tc
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bindTy m (ITypeDecl _ rtc tvs (RecordType fs _)) env =
  foldr (bindRecordLabels m rtc') env' fs
  where urtc = fromRecordExtId $ unqualify rtc
        rtc' = qualifyWith m urtc
        env' = bindConstr m rtc' tvs (constrType rtc' tvs)
               (ConstrDecl NoPos [] urtc (map snd fs)) env
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bindTy m (IFunctionDecl _ f a ty) env = Map.insert (unqualify f)
  (Value (qualQualify m f) a (polyType (toQualType m [] ty))) env
bindTy _ _ env = env
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bindConstr :: ModuleIdent -> QualIdent -> [Ident] -> TypeExpr -> ConstrDecl
           -> ExpValueEnv -> ExpValueEnv
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bindConstr m tc tvs ty0 (ConstrDecl     _ evs c tys) = Map.insert c $
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  DataConstructor (qualifyLike tc c) (length tys) $
  constrType' m tvs evs (foldr ArrowType ty0 tys)
bindConstr m tc tvs ty0 (ConOpDecl _ evs ty1 op ty2) = Map.insert op $
  DataConstructor (qualifyLike tc op) 2 $
  constrType' m tvs evs (ArrowType ty1 (ArrowType ty2 ty0))
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bindNewConstr :: ModuleIdent -> QualIdent -> [Ident] -> TypeExpr
              -> NewConstrDecl -> ExpValueEnv -> ExpValueEnv
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bindNewConstr m tc tvs ty0 (NewConstrDecl _ evs c ty1) = Map.insert c $
  NewtypeConstructor (qualifyLike tc c) $
  constrType' m tvs evs (ArrowType ty1 ty0)

constrType' :: ModuleIdent -> [Ident] -> [Ident] -> TypeExpr -> ExistTypeScheme
constrType' m tvs evs ty = ForAllExist (length tvs) (length evs)
                                       (toQualType m tvs ty)

qualifyLike :: QualIdent -> Ident -> QualIdent
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qualifyLike x = maybe qualify qualifyWith (qidModule x)
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bindRecordLabels :: ModuleIdent -> QualIdent -> ([Ident], TypeExpr)
                 -> ExpValueEnv -> ExpValueEnv
bindRecordLabels m r (ls, ty) env = foldr bindLbl env ls
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  where
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  bindLbl l = Map.insert l (lblInfo l)
  lblInfo l = Label (qualify l) r (polyType $ toQualType m [] ty)

constrType :: QualIdent -> [Ident] -> TypeExpr
constrType tc tvs = ConstructorType tc $ map VariableType tvs
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-- ---------------------------------------------------------------------------
-- Expansion of the import specification
-- ---------------------------------------------------------------------------

-- After the environments have been initialized, the optional import
-- specifications can be checked. There are two kinds of import
-- specifications, a ``normal'' one, which names the entities that shall
-- be imported, and a hiding specification, which lists those entities
-- that shall not be imported.
--
-- There is a subtle difference between both kinds of
-- specifications: While it is not allowed to list a data constructor
-- outside of its type in a ``normal'' specification, it is allowed to
-- hide a data constructor explicitly. E.g., if module \texttt{A} exports
-- the data type \texttt{T} with constructor \texttt{C}, the data
-- constructor can be imported with one of the two specifications
--
-- import A (T(C))
-- import A (T(..))
--
-- but can be hidden in three different ways:
--
-- import A hiding (C)
-- import A hiding (T (C))
-- import A hiding (T (..))
--
-- The functions \texttt{expandImport} and \texttt{expandHiding} check
-- that all entities in an import specification are actually exported
-- from the module. In addition, all imports of type constructors are
-- changed into a \texttt{T()} specification and explicit imports for the
-- data constructors are added.

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data ExpandState = ExpandState
  { expModIdent :: ModuleIdent
  , expTCEnv    :: ExpTCEnv
  , expValueEnv :: ExpValueEnv
  , errors      :: [Message]
  }

type ExpandM a = S.State ExpandState a

getModuleIdent :: ExpandM ModuleIdent
getModuleIdent = S.gets expModIdent

getTyConsEnv :: ExpandM ExpTCEnv
getTyConsEnv = S.gets expTCEnv

getValueEnv :: ExpandM ExpValueEnv
getValueEnv = S.gets expValueEnv

report :: Message -> ExpandM ()
report msg = S.modify $ \ s -> s { errors = msg : errors s }

runExpand :: ExpandM a -> ModuleIdent -> ExpTCEnv -> ExpValueEnv -> (a, [Message])
runExpand expand m tcEnv tyEnv =
  let (r, s) = S.runState expand (ExpandState m tcEnv tyEnv [])
  in (r, reverse $ errors s)

expandSpecs :: Maybe ImportSpec -> ExpandM [Import]
expandSpecs Nothing                 = return []
expandSpecs (Just (Importing _ is)) = concat `liftM` mapM expandImport is
expandSpecs (Just (Hiding    _ is)) = concat `liftM` mapM expandHiding is

expandImport :: Import -> ExpandM [Import]
expandImport (Import             x) =               expandThing    x
expandImport (ImportTypeWith tc cs) = (:[]) `liftM` expandTypeWith tc cs
expandImport (ImportTypeAll     tc) = (:[]) `liftM` expandTypeAll  tc

expandHiding :: Import -> ExpandM [Import]
expandHiding (Import             x) = expandHide x
expandHiding (ImportTypeWith tc cs) = (:[]) `liftM` expandTypeWith tc cs
expandHiding (ImportTypeAll     tc) = (:[]) `liftM` expandTypeAll  tc
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-- try to expand as type constructor
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expandThing :: Ident -> ExpandM [Import]
expandThing tc = do
  tcEnv <- getTyConsEnv
  case Map.lookup tc tcEnv of
    Just _  -> expandThing' tc $ Just [ImportTypeWith tc []]
    Nothing -> expandThing' tc Nothing
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-- try to expand as function / data constructor
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expandThing' :: Ident -> Maybe [Import] -> ExpandM [Import]
expandThing' f tcImport = do
  m     <- getModuleIdent
  tyEnv <- getValueEnv
  expand m f (Map.lookup f tyEnv) tcImport
  where
  expand :: ModuleIdent -> Ident
         -> Maybe ValueInfo -> Maybe [Import] -> ExpandM [Import]
  expand m e Nothing  Nothing   = report (errUndefinedEntity m e) >> return []
  expand _ _ Nothing  (Just tc) = return tc
  expand m e (Just v) maybeTc
    | isConstr v = case maybeTc of
        Nothing -> report (errImportDataConstr m e) >> return []
        Just tc -> return tc
    | otherwise  = return [Import e]

  isConstr (DataConstructor  _ _ _) = True
  isConstr (NewtypeConstructor _ _) = True
  isConstr (Value            _ _ _) = False
  isConstr (Label            _ _ _) = False
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-- try to hide as type constructor
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expandHide :: Ident -> ExpandM [Import]
expandHide tc = do
  tcEnv <- getTyConsEnv
  case Map.lookup tc tcEnv of
    Just _  -> expandHide' tc $ Just [ImportTypeWith tc []]
    Nothing -> expandHide' tc Nothing
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-- try to hide as function / data constructor
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expandHide' :: Ident -> Maybe [Import] -> ExpandM [Import]
expandHide' f tcImport = do
  m     <- getModuleIdent
  tyEnv <- getValueEnv
  case Map.lookup f tyEnv of
    Just _  -> return $ Import f : fromMaybe [] tcImport
    Nothing -> case tcImport of
      Nothing -> report (errUndefinedEntity m f) >> return []
      Just tc -> return tc

expandTypeWith ::  Ident -> [Ident] -> ExpandM Import
expandTypeWith tc cs = do
  m     <- getModuleIdent
  tcEnv <- getTyConsEnv
  ImportTypeWith tc `liftM` case Map.lookup tc tcEnv of
    Just (DataType     _ _                cs') ->
      mapM (checkConstr [c | Just (DataConstr c _ _) <- cs']) cs
    Just (RenamingType _ _ (DataConstr c _ _)) ->
      mapM (checkConstr [c]) cs
    Just (AliasType    _ _ (TypeRecord  fs _)) ->
      mapM (checkLabel [l | (l, _) <- fs] . renameLabel) cs
    Just (AliasType _ _ _) -> report (errNonDataType       tc) >> return []
    Nothing                -> report (errUndefinedEntity m tc) >> return []
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  where
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  checkConstr cs' c = do
    unless (c `elem` cs') $ report $ errUndefinedDataConstr tc c
    return c
  checkLabel ls' l  = do
    unless (l `elem` ls') $ report $ errUndefinedLabel tc l
    return l

expandTypeAll :: Ident -> ExpandM Import
expandTypeAll tc = do
  m     <- getModuleIdent
  tcEnv <- getTyConsEnv
  ImportTypeWith tc `liftM` case Map.lookup tc tcEnv of
    Just (DataType     _ _                 cs) ->
      return [c | Just (DataConstr c _ _) <- cs]
    Just (RenamingType _ _ (DataConstr c _ _)) -> return [c]
    Just (AliasType    _ _ (TypeRecord  fs _)) -> return [l | (l, _) <- fs]
    Just (AliasType _ _ _) -> report (errNonDataType       tc) >> return []
    Nothing                -> report (errUndefinedEntity m tc) >> return []
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errUndefinedEntity :: ModuleIdent -> Ident -> Message
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errUndefinedEntity m x = posMsg x $
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  "Module " ++ moduleName m ++ " does not export " ++ idName x
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errUndefinedDataConstr :: Ident -> Ident -> Message
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errUndefinedDataConstr tc c = posMsg c $
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  idName c ++ " is not a data constructor of type " ++ idName tc
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errUndefinedLabel :: Ident -> Ident -> Message
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errUndefinedLabel tc c = posMsg c $
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  idName c ++ " is not a label of record type " ++ idName tc
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errNonDataType :: Ident -> Message
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errNonDataType tc = posMsg tc $ idName tc ++ " is not a data type"
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errImportDataConstr :: ModuleIdent -> Ident -> Message
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errImportDataConstr _ c = posMsg c $
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  "Explicit import for data constructor " ++ idName c
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-- ---------------------------------------------------------------------------

-- After all modules have been imported, the compiler has to ensure that
-- all references to a data type use the same list of constructors.

importUnifyData :: CompilerEnv -> CompilerEnv
importUnifyData cEnv = cEnv { tyConsEnv = importUnifyData' $ tyConsEnv cEnv }

importUnifyData' :: TCEnv -> TCEnv
importUnifyData' tcEnv = fmap (setInfo allTyCons) tcEnv
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  where
  setInfo tcs t   = fromJust $ Map.lookup (origName t) tcs
  allTyCons       = foldr (mergeData . snd) Map.empty $ allImports tcEnv
  mergeData t tcs =
    Map.insert tc (maybe t (fromJust . merge t) $ Map.lookup tc tcs) tcs
    where tc = origName t
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-- ---------------------------------------------------------------------------

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-- |
qualifyEnv :: Options -> CompilerEnv -> CompilerEnv
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qualifyEnv opts env = expandValueEnv opts
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                    $ qualifyLocal env
                    $ foldl (flip importInterfaceIntf) initEnv
                    $ Map.elems
                    $ interfaceEnv env
  where initEnv = initCompilerEnv $ moduleIdent env

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qualifyLocal :: CompilerEnv -> CompilerEnv -> CompilerEnv
qualifyLocal currentEnv initEnv = currentEnv
  { opPrecEnv = foldr bindQual   pEnv  $ localBindings $ opPrecEnv currentEnv
  , tyConsEnv = foldr bindQual   tcEnv $ localBindings $ tyConsEnv currentEnv
  , valueEnv  = foldr bindGlobal tyEnv $ localBindings $ valueEnv  currentEnv
  }
  where
    pEnv  = opPrecEnv initEnv
    tcEnv = tyConsEnv initEnv
    tyEnv = valueEnv  initEnv
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    bindQual   (_, y) = qualBindTopEnv "Imports.qualifyEnv" (origName y) y
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    bindGlobal (x, y)
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      | idUnique x == 0 = bindQual (x, y)
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      | otherwise       = bindTopEnv "Imports.qualifyEnv" x y
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-- Importing an interface into another interface is somewhat simpler
-- because all entities are imported into the environment. In addition,
-- only a qualified import is necessary. Note that the hidden data types
-- are imported as well because they may be used in type expressions in
-- an interface.

importInterfaceIntf :: Interface -> CompilerEnv -> CompilerEnv
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importInterfaceIntf i@(Interface m _ _) env = env
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  { opPrecEnv = importEntities m True (const True) id mPEnv  $ opPrecEnv env
  , tyConsEnv = importEntities m True (const True) id mTCEnv $ tyConsEnv env
  , valueEnv  = importEntities m True (const True) id mTyEnv $ valueEnv  env
  }
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  where
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  mPEnv  = intfEnv bindPrec     i -- all operator precedences
  mTCEnv = intfEnv bindTCHidden i -- all type constructors
  mTyEnv = intfEnv bindTy       i -- all values
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-- ---------------------------------------------------------------------------
-- Record stuff
-- ---------------------------------------------------------------------------

expandTCValueEnv :: Options -> CompilerEnv -> CompilerEnv
expandTCValueEnv opts env
  | enabled   = env' { tyConsEnv = tcEnv' }
  | otherwise = env
  where
  enabled = Records `elem` optExtensions opts
  tcEnv'  = fmap (expandRecordTC tcEnv) tcEnv
  tcEnv   = tyConsEnv env'
  env'    = expandValueEnv opts env

expandRecordTC :: TCEnv -> TypeInfo -> TypeInfo
expandRecordTC tcEnv (DataType qid n args) =
  DataType qid n $ map (fmap expandData) args
  where
  expandData (DataConstr c m tys) =
    DataConstr c m $ map (expandRecords tcEnv) tys
expandRecordTC tcEnv (RenamingType qid n (DataConstr c m [ty])) =
  RenamingType qid n (DataConstr c m [expandRecords tcEnv ty])
expandRecordTC _     (RenamingType _   _ (DataConstr    _ _ _)) =
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  internalError "Imports.expandRecordTC"
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expandRecordTC tcEnv (AliasType qid n ty) =
  AliasType qid n (expandRecords tcEnv ty)

expandValueEnv :: Options -> CompilerEnv -> CompilerEnv
expandValueEnv opts env
  | enabled   = env { valueEnv = tyEnv' }
  | otherwise = env
  where
  tcEnv    = tyConsEnv env
  tyEnv    = valueEnv env
  enabled  = Records `elem` optExtensions opts
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  tyEnv'   = fmap (expandRecordTypes tcEnv) $ addImportedLabels m tyEnv
  m        = moduleIdent env

-- TODO: This is necessary as currently labels are unqualified.
-- Without this additional import the labels would no longer be known.
addImportedLabels :: ModuleIdent -> ValueEnv -> ValueEnv
addImportedLabels m tyEnv = foldr addLabelType tyEnv (allImports tyEnv)
  where
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  addLabelType (_, Label l r ty) = importTopEnv (fromMaybe m (qidModule r))
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                                   (unqualify l) (Label l r ty)
  addLabelType _ = id
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expandRecordTypes :: TCEnv -> ValueInfo -> ValueInfo
expandRecordTypes tcEnv (DataConstructor  qid a (ForAllExist n m ty)) =
  DataConstructor qid a (ForAllExist n m (expandRecords tcEnv ty))
expandRecordTypes tcEnv (NewtypeConstructor qid (ForAllExist n m ty)) =
  NewtypeConstructor qid (ForAllExist n m (expandRecords tcEnv ty))
expandRecordTypes tcEnv (Value qid a (ForAll n ty)) =
  Value qid a (ForAll n (expandRecords tcEnv ty))
expandRecordTypes tcEnv (Label qid r (ForAll n ty)) =
  Label qid r (ForAll n (expandRecords tcEnv ty))

expandRecords :: TCEnv -> Type -> Type
expandRecords tcEnv (TypeConstructor qid tys) = case qualLookupTC qid tcEnv of
  [AliasType _ _ rty@(TypeRecord _ _)]
    -> expandRecords tcEnv $ expandAliasType (map (expandRecords tcEnv) tys) rty
  _ -> TypeConstructor qid $ map (expandRecords tcEnv) tys
expandRecords tcEnv (TypeConstrained tys v) =
  TypeConstrained (map (expandRecords tcEnv) tys) v
expandRecords tcEnv (TypeArrow ty1 ty2) =
  TypeArrow (expandRecords tcEnv ty1) (expandRecords tcEnv ty2)
expandRecords tcEnv (TypeRecord fs rv) =
  TypeRecord (map (\ (l, ty) -> (l, expandRecords tcEnv ty)) fs) rv
expandRecords _ ty = ty

-- Unlike usual identifiers like in functions, types etc., identifiers
-- of labels are always represented unqualified within the whole context
-- of compilation. Since the common type environment (type \texttt{ValueEnv})
-- has some problems with handling imported unqualified identifiers, it is
-- necessary to add the type information for labels seperately. For this reason
-- the function \texttt{importLabels} generates an environment containing
-- all imported labels and the function \texttt{addImportedLabels} adds this
-- content to a value environment.

-- importLabels :: InterfaceEnv -> [ImportDecl] -> LabelEnv
-- importLabels mEnv ds = foldl importLabelTypes initLabelEnv ds
--   where
--   importLabelTypes :: LabelEnv -> ImportDecl -> LabelEnv
--   importLabelTypes lEnv (ImportDecl _ m _ asM is) = case Map.lookup m mEnv of
--     Just (Interface _ _ ds') ->
--       foldl (importLabelType (fromMaybe m asM) is) lEnv ds'
--     Nothing  ->
--       internalError "Records.importLabels"
--
--   importLabelType m is lEnv (ITypeDecl _ r _ (RecordType fs _)) =
--     foldl (insertLabelType r' (getImportSpec r' is)) lEnv fs
--     where r' = qualifyWith m $ fromRecordExtId $ unqualify r
--   importLabelType _ _  lEnv _ = lEnv
--
--   insertLabelType r (Just (ImportTypeAll     _)) lEnv ([l], ty) =
--     bindLabelType l r (toType [] ty) lEnv
--   insertLabelType r (Just (ImportTypeWith _ ls)) lEnv ([l], ty)
--     | l `elem` ls = bindLabelType l r (toType [] ty) lEnv
--     | otherwise   = lEnv
--   insertLabelType _ _ lEnv _ = lEnv
--
--   getImportSpec r (Just (Importing _ is')) = find (isImported (unqualify r)) is'
--   getImportSpec r Nothing                  = Just $ ImportTypeAll $ unqualify r
--   getImportSpec _ _                        = Nothing
--
--   isImported r (Import         r'  ) = r == r'
--   isImported r (ImportTypeWith r' _) = r == r'
--   isImported r (ImportTypeAll  r'  ) = r == r'