basicTypes/Name.hs

    {-
    (c) The University of Glasgow 2006
    (c) The GRASP/AQUA Project, Glasgow University, 1992-1998

    \section[Name]{@Name@: to transmit name info from renamer to typechecker}
    -}

    {-# LANGUAGE RecordWildCards #-}

    -- |
    -- #name_types#
    -- GHC uses several kinds of name internally:
    --
    -- * 'OccName.OccName': see "OccName#name_types"
    --
    -- * 'RdrName.RdrName': see "RdrName#name_types"
    --
    -- *  'Name.Name' is the type of names that have had their scoping and binding resolved. They
    --   have an 'OccName.OccName' but also a 'Unique.Unique' that disambiguates Names that have
    --   the same 'OccName.OccName' and indeed is used for all 'Name.Name' comparison. Names
    --   also contain information about where they originated from, see "Name#name_sorts"
    --
    -- * 'Id.Id': see "Id#name_types"
    --
    -- * 'Var.Var': see "Var#name_types"
    --
    -- #name_sorts#
    -- Names are one of:
    --
    --  * External, if they name things declared in other modules. Some external
    --    Names are wired in, i.e. they name primitives defined in the compiler itself
    --
    --  * Internal, if they name things in the module being compiled. Some internal
    --    Names are system names, if they are names manufactured by the compiler

    module Name (
            -- * The main types
            Name,                                   -- Abstract
            BuiltInSyntax(..),

            -- ** Creating 'Name's
            mkSystemName, mkSystemNameAt,
            mkInternalName, mkClonedInternalName, mkDerivedInternalName,
            mkSystemVarName, mkSysTvName,
            mkFCallName,
            mkExternalName, mkWiredInName,

            -- ** Manipulating and deconstructing 'Name's
            nameUnique, setNameUnique,
            nameOccName, nameModule, nameModule_maybe,
            setNameLoc,
            tidyNameOcc,
            localiseName,
            mkLocalisedOccName,

            nameSrcLoc, nameSrcSpan, pprNameDefnLoc, pprDefinedAt,

            -- ** Predicates on 'Name's
            isSystemName, isInternalName, isExternalName,
            isTyVarName, isTyConName, isDataConName,
            isValName, isVarName,
            isWiredInName, isBuiltInSyntax,
            isHoleName,
            wiredInNameTyThing_maybe,
            nameIsLocalOrFrom, nameIsHomePackage,
            nameIsHomePackageImport, nameIsFromExternalPackage,
            stableNameCmp,

            -- * Class 'NamedThing' and overloaded friends
            NamedThing(..),
            getSrcLoc, getSrcSpan, getOccString, getOccFS,

            pprInfixName, pprPrefixName, pprModulePrefix,
            nameStableString,

            -- Re-export the OccName stuff
            module OccName
        ) where

    import {-# SOURCE #-} TyCoRep( TyThing )
    import {-# SOURCE #-} PrelNames( starKindTyConKey, unicodeStarKindTyConKey )

    import OccName
    import Module
    import SrcLoc
    import Unique
    import Util
    import Maybes
    import Binary
    import DynFlags
    import FastString
    import Outputable

    import Control.DeepSeq
    import Data.Data

    {-
    ************************************************************************
    *                                                                      *
    \subsection[Name-datatype]{The @Name@ datatype, and name construction}
    *                                                                      *
    ************************************************************************
    -}

    -- | A unique, unambiguous name for something, containing information about where
    -- that thing originated.
    data Name = Name {
                    n_sort :: NameSort,     -- What sort of name it is
                    n_occ  :: !OccName,     -- Its occurrence name
                    n_uniq :: {-# UNPACK #-} !Int,
                    n_loc  :: !SrcSpan      -- Definition site
                }

    -- NOTE: we make the n_loc field strict to eliminate some potential
    -- (and real!) space leaks, due to the fact that we don't look at
    -- the SrcLoc in a Name all that often.

    data NameSort
      = External Module

      | WiredIn Module TyThing BuiltInSyntax
            -- A variant of External, for wired-in things

      | Internal            -- A user-defined Id or TyVar
                            -- defined in the module being compiled

      | System              -- A system-defined Id or TyVar.  Typically the
                            -- OccName is very uninformative (like 's')

    instance Outputable NameSort where
      ppr (External _)    = text "external"
      ppr (WiredIn _ _ _) = text "wired-in"
      ppr  Internal       = text "internal"
      ppr  System         = text "system"

    instance NFData Name where
      rnf Name{..} = rnf n_sort

    instance NFData NameSort where
      rnf (External m) = rnf m
      rnf (WiredIn m t b) = rnf m `seq` t `seq` b `seq` ()
        -- XXX this is a *lie*, we're not going to rnf the TyThing, but
        -- since the TyThings for WiredIn Names are all static they can't
        -- be hiding space leaks or errors.
      rnf Internal = ()
      rnf System = ()

    -- | BuiltInSyntax is for things like @(:)@, @[]@ and tuples,
    -- which have special syntactic forms.  They aren't in scope
    -- as such.
    data BuiltInSyntax = BuiltInSyntax | UserSyntax

    {-
    Notes about the NameSorts:

    1.  Initially, top-level Ids (including locally-defined ones) get External names,
        and all other local Ids get Internal names

    2.  In any invocation of GHC, an External Name for "M.x" has one and only one
        unique.  This unique association is ensured via the Name Cache;
        see Note [The Name Cache] in IfaceEnv.

    3.  Things with a External name are given C static labels, so they finally
        appear in the .o file's symbol table.  They appear in the symbol table
        in the form M.n.  If originally-local things have this property they
        must be made @External@ first.

    4.  In the tidy-core phase, a External that is not visible to an importer
        is changed to Internal, and a Internal that is visible is changed to External

    5.  A System Name differs in the following ways:
            a) has unique attached when printing dumps
            b) unifier eliminates sys tyvars in favour of user provs where possible

        Before anything gets printed in interface files or output code, it's
        fed through a 'tidy' processor, which zaps the OccNames to have
        unique names; and converts all sys-locals to user locals
        If any desugarer sys-locals have survived that far, they get changed to
        "ds1", "ds2", etc.

    Built-in syntax => It's a syntactic form, not "in scope" (e.g. [])

    Wired-in thing  => The thing (Id, TyCon) is fully known to the compiler,
                       not read from an interface file.
                       E.g. Bool, True, Int, Float, and many others

    All built-in syntax is for wired-in things.
    -}

    instance HasOccName Name where
      occName = nameOccName

    nameUnique              :: Name -> Unique
    nameOccName             :: Name -> OccName
    nameModule              :: Name -> Module
    nameSrcLoc              :: Name -> SrcLoc
    nameSrcSpan             :: Name -> SrcSpan

    nameUnique  name = mkUniqueGrimily (n_uniq name)
    nameOccName name = n_occ  name
    nameSrcLoc  name = srcSpanStart (n_loc name)
    nameSrcSpan name = n_loc  name

    {-
    ************************************************************************
    *                                                                      *
    \subsection{Predicates on names}
    *                                                                      *
    ************************************************************************
    -}

    isInternalName    :: Name -> Bool
    isExternalName    :: Name -> Bool
    isSystemName      :: Name -> Bool
    isWiredInName     :: Name -> Bool

    isWiredInName (Name {n_sort = WiredIn _ _ _}) = True
    isWiredInName _                               = False

    wiredInNameTyThing_maybe :: Name -> Maybe TyThing
    wiredInNameTyThing_maybe (Name {n_sort = WiredIn _ thing _}) = Just thing
    wiredInNameTyThing_maybe _                                   = Nothing

    isBuiltInSyntax :: Name -> Bool
    isBuiltInSyntax (Name {n_sort = WiredIn _ _ BuiltInSyntax}) = True
    isBuiltInSyntax _                                           = False

    isExternalName (Name {n_sort = External _})    = True
    isExternalName (Name {n_sort = WiredIn _ _ _}) = True
    isExternalName _                               = False

    isInternalName name = not (isExternalName name)

    isHoleName :: Name -> Bool
    isHoleName = isHoleModule . nameModule

    nameModule name =
      nameModule_maybe name `orElse`
      pprPanic "nameModule" (ppr (n_sort name) <+> ppr name)

    nameModule_maybe :: Name -> Maybe Module
    nameModule_maybe (Name { n_sort = External mod})    = Just mod
    nameModule_maybe (Name { n_sort = WiredIn mod _ _}) = Just mod
    nameModule_maybe _                                  = Nothing

    nameIsLocalOrFrom :: Module -> Name -> Bool
    -- ^ Returns True if the name is
    --   (a) Internal
    --   (b) External but from the specified module
    --   (c) External but from the 'interactive' package
    --
    -- The key idea is that
    --    False means: the entity is defined in some other module
    --                 you can find the details (type, fixity, instances)
    --                     in some interface file
    --                 those details will be stored in the EPT or HPT
    --
    --    True means:  the entity is defined in this module or earlier in
    --                     the GHCi session
    --                 you can find details (type, fixity, instances) in the
    --                     TcGblEnv or TcLclEnv
    --
    -- The isInteractiveModule part is because successive interactions of a GCHi session
    -- each give rise to a fresh module (Ghci1, Ghci2, etc), but they all come
    -- from the magic 'interactive' package; and all the details are kept in the
    -- TcLclEnv, TcGblEnv, NOT in the HPT or EPT.
    -- See Note [The interactive package] in HscTypes

    nameIsLocalOrFrom from name
      | Just mod <- nameModule_maybe name = from == mod || isInteractiveModule mod
      | otherwise                         = True

    nameIsHomePackage :: Module -> Name -> Bool
    -- True if the Name is defined in module of this package
    nameIsHomePackage this_mod
      = \nm -> case n_sort nm of
                  External nm_mod    -> moduleUnitId nm_mod == this_pkg
                  WiredIn nm_mod _ _ -> moduleUnitId nm_mod == this_pkg
                  Internal -> True
                  System   -> False
      where
        this_pkg = moduleUnitId this_mod

    nameIsHomePackageImport :: Module -> Name -> Bool
    -- True if the Name is defined in module of this package
    -- /other than/ the this_mod
    nameIsHomePackageImport this_mod
      = \nm -> case nameModule_maybe nm of
                  Nothing -> False
                  Just nm_mod -> nm_mod /= this_mod
                              && moduleUnitId nm_mod == this_pkg
      where
        this_pkg = moduleUnitId this_mod

    -- | Returns True if the Name comes from some other package: neither this
    -- pacakge nor the interactive package.
    nameIsFromExternalPackage :: UnitId -> Name -> Bool
    nameIsFromExternalPackage this_pkg name
      | Just mod <- nameModule_maybe name
      , moduleUnitId mod /= this_pkg    -- Not this package
      , not (isInteractiveModule mod)       -- Not the 'interactive' package
      = True
      | otherwise
      = False

    isTyVarName :: Name -> Bool
    isTyVarName name = isTvOcc (nameOccName name)

    isTyConName :: Name -> Bool
    isTyConName name = isTcOcc (nameOccName name)

    isDataConName :: Name -> Bool
    isDataConName name = isDataOcc (nameOccName name)

    isValName :: Name -> Bool
    isValName name = isValOcc (nameOccName name)

    isVarName :: Name -> Bool
    isVarName = isVarOcc . nameOccName

    isSystemName (Name {n_sort = System}) = True
    isSystemName _                        = False

    {-
    ************************************************************************
    *                                                                      *
    \subsection{Making names}
    *                                                                      *
    ************************************************************************
    -}

    -- | Create a name which is (for now at least) local to the current module and hence
    -- does not need a 'Module' to disambiguate it from other 'Name's
    mkInternalName :: Unique -> OccName -> SrcSpan -> Name
    mkInternalName uniq occ loc = Name { n_uniq = getKey uniq
                                       , n_sort = Internal
                                       , n_occ = occ
                                       , n_loc = loc }
            -- NB: You might worry that after lots of huffing and
            -- puffing we might end up with two local names with distinct
            -- uniques, but the same OccName.  Indeed we can, but that's ok
            --      * the insides of the compiler don't care: they use the Unique
            --      * when printing for -ddump-xxx you can switch on -dppr-debug to get the
            --        uniques if you get confused
            --      * for interface files we tidyCore first, which makes
            --        the OccNames distinct when they need to be

    mkClonedInternalName :: Unique -> Name -> Name
    mkClonedInternalName uniq (Name { n_occ = occ, n_loc = loc })
      = Name { n_uniq = getKey uniq, n_sort = Internal
             , n_occ = occ, n_loc = loc }

    mkDerivedInternalName :: (OccName -> OccName) -> Unique -> Name -> Name
    mkDerivedInternalName derive_occ uniq (Name { n_occ = occ, n_loc = loc })
      = Name { n_uniq = getKey uniq, n_sort = Internal
             , n_occ = derive_occ occ, n_loc = loc }

    -- | Create a name which definitely originates in the given module
    mkExternalName :: Unique -> Module -> OccName -> SrcSpan -> Name
    -- WATCH OUT! External Names should be in the Name Cache
    -- (see Note [The Name Cache] in IfaceEnv), so don't just call mkExternalName
    -- with some fresh unique without populating the Name Cache
    mkExternalName uniq mod occ loc
      = Name { n_uniq = getKey uniq, n_sort = External mod,
               n_occ = occ, n_loc = loc }

    -- | Create a name which is actually defined by the compiler itself
    mkWiredInName :: Module -> OccName -> Unique -> TyThing -> BuiltInSyntax -> Name
    mkWiredInName mod occ uniq thing built_in
      = Name { n_uniq = getKey uniq,
               n_sort = WiredIn mod thing built_in,
               n_occ = occ, n_loc = wiredInSrcSpan }

    -- | Create a name brought into being by the compiler
    mkSystemName :: Unique -> OccName -> Name
    mkSystemName uniq occ = mkSystemNameAt uniq occ noSrcSpan

    mkSystemNameAt :: Unique -> OccName -> SrcSpan -> Name
    mkSystemNameAt uniq occ loc = Name { n_uniq = getKey uniq, n_sort = System
                                       , n_occ = occ, n_loc = loc }

    mkSystemVarName :: Unique -> FastString -> Name
    mkSystemVarName uniq fs = mkSystemName uniq (mkVarOccFS fs)

    mkSysTvName :: Unique -> FastString -> Name
    mkSysTvName uniq fs = mkSystemName uniq (mkOccNameFS tvName fs)

    -- | Make a name for a foreign call
    mkFCallName :: Unique -> String -> Name
    mkFCallName uniq str = mkInternalName uniq (mkVarOcc str) noSrcSpan
       -- The encoded string completely describes the ccall

    -- When we renumber/rename things, we need to be
    -- able to change a Name's Unique to match the cached
    -- one in the thing it's the name of.  If you know what I mean.
    setNameUnique :: Name -> Unique -> Name
    setNameUnique name uniq = name {n_uniq = getKey uniq}

    -- This is used for hsigs: we want to use the name of the originally exported
    -- entity, but edit the location to refer to the reexport site
    setNameLoc :: Name -> SrcSpan -> Name
    setNameLoc name loc = name {n_loc = loc}

    tidyNameOcc :: Name -> OccName -> Name
    -- We set the OccName of a Name when tidying
    -- In doing so, we change System --> Internal, so that when we print
    -- it we don't get the unique by default.  It's tidy now!
    tidyNameOcc name@(Name { n_sort = System }) occ = name { n_occ = occ, n_sort = Internal}
    tidyNameOcc name                            occ = name { n_occ = occ }

    -- | Make the 'Name' into an internal name, regardless of what it was to begin with
    localiseName :: Name -> Name
    localiseName n = n { n_sort = Internal }

    -- |Create a localised variant of a name.
    --
    -- If the name is external, encode the original's module name to disambiguate.
    -- SPJ says: this looks like a rather odd-looking function; but it seems to
    --           be used only during vectorisation, so I'm not going to worry
    mkLocalisedOccName :: Module -> (Maybe String -> OccName -> OccName) -> Name -> OccName
    mkLocalisedOccName this_mod mk_occ name = mk_occ origin (nameOccName name)
      where
        origin
          | nameIsLocalOrFrom this_mod name = Nothing
          | otherwise                       = Just (moduleNameColons . moduleName . nameModule $ name)

    {-
    ************************************************************************
    *                                                                      *
    \subsection{Hashing and comparison}
    *                                                                      *
    ************************************************************************
    -}

    cmpName :: Name -> Name -> Ordering
    cmpName n1 n2 = n_uniq n1 `compare` n_uniq n2

    -- | Compare Names lexicographically
    -- This only works for Names that originate in the source code or have been
    -- tidied.
    stableNameCmp :: Name -> Name -> Ordering
    stableNameCmp (Name { n_sort = s1, n_occ = occ1 })
                  (Name { n_sort = s2, n_occ = occ2 })
      = (s1 `sort_cmp` s2) `thenCmp` (occ1 `compare` occ2)
        -- The ordinary compare on OccNames is lexicographic
      where
        -- Later constructors are bigger
        sort_cmp (External m1) (External m2)       = m1 `stableModuleCmp` m2
        sort_cmp (External {}) _                   = LT
        sort_cmp (WiredIn {}) (External {})        = GT
        sort_cmp (WiredIn m1 _ _) (WiredIn m2 _ _) = m1 `stableModuleCmp` m2
        sort_cmp (WiredIn {})     _                = LT
        sort_cmp Internal         (External {})    = GT
        sort_cmp Internal         (WiredIn {})     = GT
        sort_cmp Internal         Internal         = EQ
        sort_cmp Internal         System           = LT
        sort_cmp System           System           = EQ
        sort_cmp System           _                = GT

    {-
    ************************************************************************
    *                                                                      *
    \subsection[Name-instances]{Instance declarations}
    *                                                                      *
    ************************************************************************
    -}

    instance Eq Name where
        a == b = case (a `compare` b) of { EQ -> True;  _ -> False }
        a /= b = case (a `compare` b) of { EQ -> False; _ -> True }

    instance Ord Name where
        a <= b = case (a `compare` b) of { LT -> True;  EQ -> True;  GT -> False }
        a <  b = case (a `compare` b) of { LT -> True;  EQ -> False; GT -> False }
        a >= b = case (a `compare` b) of { LT -> False; EQ -> True;  GT -> True  }
        a >  b = case (a `compare` b) of { LT -> False; EQ -> False; GT -> True  }
        compare a b = cmpName a b

    instance Uniquable Name where
        getUnique = nameUnique

    instance NamedThing Name where
        getName n = n

    instance Data Name where
      -- don't traverse?
      toConstr _   = abstractConstr "Name"
      gunfold _ _  = error "gunfold"
      dataTypeOf _ = mkNoRepType "Name"

    {-
    ************************************************************************
    *                                                                      *
    \subsection{Binary}
    *                                                                      *
    ************************************************************************
    -}

    -- | Assumes that the 'Name' is a non-binding one. See
    -- 'IfaceSyn.putIfaceTopBndr' and 'IfaceSyn.getIfaceTopBndr' for serializing
    -- binding 'Name's. See 'UserData' for the rationale for this distinction.
    instance Binary Name where
       put_ bh name =
          case getUserData bh of
            UserData{ ud_put_nonbinding_name = put_name } -> put_name bh name

       get bh =
          case getUserData bh of
            UserData { ud_get_name = get_name } -> get_name bh

    {-
    ************************************************************************
    *                                                                      *
    \subsection{Pretty printing}
    *                                                                      *
    ************************************************************************
    -}

    instance Outputable Name where
        ppr name = pprName name

    instance OutputableBndr Name where
        pprBndr _ name = pprName name
        pprInfixOcc  = pprInfixName
        pprPrefixOcc = pprPrefixName

    pprName :: Name -> SDoc
    pprName (Name {n_sort = sort, n_uniq = u, n_occ = occ})
      = getPprStyle $ \ sty ->
        case sort of
          WiredIn mod _ builtin   -> pprExternal sty uniq mod occ True  builtin
          External mod            -> pprExternal sty uniq mod occ False UserSyntax
          System                  -> pprSystem sty uniq occ
          Internal                -> pprInternal sty uniq occ
      where uniq = mkUniqueGrimily u

    pprExternal :: PprStyle -> Unique -> Module -> OccName -> Bool -> BuiltInSyntax -> SDoc
    pprExternal sty uniq mod occ is_wired is_builtin
      | codeStyle sty = ppr mod <> char '_' <> ppr_z_occ_name occ
            -- In code style, always qualify
            -- ToDo: maybe we could print all wired-in things unqualified
            --       in code style, to reduce symbol table bloat?
      | debugStyle sty = pp_mod <> ppr_occ_name occ
                         <> braces (hsep [if is_wired then text "(w)" else empty,
                                          pprNameSpaceBrief (occNameSpace occ),
                                          pprUnique uniq])
      | BuiltInSyntax <- is_builtin = ppr_occ_name occ  -- Never qualify builtin syntax
      | otherwise                   =
            if isHoleModule mod
                then case qualName sty mod occ of
                        NameUnqual -> ppr_occ_name occ
                        _ -> braces (ppr (moduleName mod) <> dot <> ppr_occ_name occ)
                else pprModulePrefix sty mod occ <> ppr_occ_name occ
      where
        pp_mod = sdocWithDynFlags $ \dflags ->
                 if gopt Opt_SuppressModulePrefixes dflags
                 then empty
                 else ppr mod <> dot

    pprInternal :: PprStyle -> Unique -> OccName -> SDoc
    pprInternal sty uniq occ
      | codeStyle sty  = pprUniqueAlways uniq
      | debugStyle sty = ppr_occ_name occ <> braces (hsep [pprNameSpaceBrief (occNameSpace occ),
                                                           pprUnique uniq])
      | dumpStyle sty  = ppr_occ_name occ <> ppr_underscore_unique uniq
                            -- For debug dumps, we're not necessarily dumping
                            -- tidied code, so we need to print the uniques.
      | otherwise      = ppr_occ_name occ   -- User style

    -- Like Internal, except that we only omit the unique in Iface style
    pprSystem :: PprStyle -> Unique -> OccName -> SDoc
    pprSystem sty uniq occ
      | codeStyle sty  = pprUniqueAlways uniq
      | debugStyle sty = ppr_occ_name occ <> ppr_underscore_unique uniq
                         <> braces (pprNameSpaceBrief (occNameSpace occ))
      | otherwise      = ppr_occ_name occ <> ppr_underscore_unique uniq
                                    -- If the tidy phase hasn't run, the OccName
                                    -- is unlikely to be informative (like 's'),
                                    -- so print the unique

    pprModulePrefix :: PprStyle -> Module -> OccName -> SDoc
    -- Print the "M." part of a name, based on whether it's in scope or not
    -- See Note [Printing original names] in HscTypes
    pprModulePrefix sty mod occ = sdocWithDynFlags $ \dflags ->
      if gopt Opt_SuppressModulePrefixes dflags
      then empty
      else
        case qualName sty mod occ of              -- See Outputable.QualifyName:
          NameQual modname -> ppr modname <> dot       -- Name is in scope
          NameNotInScope1  -> ppr mod <> dot           -- Not in scope
          NameNotInScope2  -> ppr (moduleUnitId mod) <> colon     -- Module not in
                              <> ppr (moduleName mod) <> dot          -- scope either
          NameUnqual       -> empty                   -- In scope unqualified

    pprUnique :: Unique -> SDoc
    -- Print a unique unless we are suppressing them
    pprUnique uniq
      = sdocWithDynFlags $ \dflags ->
        ppUnless (gopt Opt_SuppressUniques dflags) $
        pprUniqueAlways uniq

    ppr_underscore_unique :: Unique -> SDoc
    -- Print an underscore separating the name from its unique
    -- But suppress it if we aren't printing the uniques anyway
    ppr_underscore_unique uniq
      = sdocWithDynFlags $ \dflags ->
        ppUnless (gopt Opt_SuppressUniques dflags) $
        char '_' <> pprUniqueAlways uniq

    ppr_occ_name :: OccName -> SDoc
    ppr_occ_name occ = ftext (occNameFS occ)
            -- Don't use pprOccName; instead, just print the string of the OccName;
            -- we print the namespace in the debug stuff above

    -- In code style, we Z-encode the strings.  The results of Z-encoding each FastString are
    -- cached behind the scenes in the FastString implementation.
    ppr_z_occ_name :: OccName -> SDoc
    ppr_z_occ_name occ = ztext (zEncodeFS (occNameFS occ))

    -- Prints (if mod information is available) "Defined at <loc>" or
    --  "Defined in <mod>" information for a Name.
    pprDefinedAt :: Name -> SDoc
    pprDefinedAt name = text "Defined" <+> pprNameDefnLoc name

    pprNameDefnLoc :: Name -> SDoc
    -- Prints "at <loc>" or
    --     or "in <mod>" depending on what info is available
    pprNameDefnLoc name
      = case nameSrcLoc name of
             -- nameSrcLoc rather than nameSrcSpan
             -- It seems less cluttered to show a location
             -- rather than a span for the definition point
           RealSrcLoc s -> text "at" <+> ppr s
           UnhelpfulLoc s
             | isInternalName name || isSystemName name
             -> text "at" <+> ftext s
             | otherwise
             -> text "in" <+> quotes (ppr (nameModule name))

    -- | Get a string representation of a 'Name' that's unique and stable
    -- across recompilations. Used for deterministic generation of binds for
    -- derived instances.
    -- eg. "$aeson_70dylHtv1FFGeai1IoxcQr$Data.Aeson.Types.Internal$String"
    nameStableString :: Name -> String
    nameStableString Name{..} =
      nameSortStableString n_sort ++ "$" ++ occNameString n_occ

    nameSortStableString :: NameSort -> String
    nameSortStableString System = "$_sys"
    nameSortStableString Internal = "$_in"
    nameSortStableString (External mod) = moduleStableString mod
    nameSortStableString (WiredIn mod _ _) = moduleStableString mod

    {-
    ************************************************************************
    *                                                                      *
    \subsection{Overloaded functions related to Names}
    *                                                                      *
    ************************************************************************
    -}

    -- | A class allowing convenient access to the 'Name' of various datatypes
    class NamedThing a where
        getOccName :: a -> OccName
        getName    :: a -> Name

        getOccName n = nameOccName (getName n)      -- Default method

    instance NamedThing e => NamedThing (GenLocated l e) where
        getName = getName . unLoc

    getSrcLoc           :: NamedThing a => a -> SrcLoc
    getSrcSpan          :: NamedThing a => a -> SrcSpan
    getOccString        :: NamedThing a => a -> String
    getOccFS            :: NamedThing a => a -> FastString

    getSrcLoc           = nameSrcLoc           . getName
    getSrcSpan          = nameSrcSpan          . getName
    getOccString        = occNameString        . getOccName
    getOccFS            = occNameFS            . getOccName

    pprInfixName :: (Outputable a, NamedThing a) => a -> SDoc
    -- See Outputable.pprPrefixVar, pprInfixVar;
    -- add parens or back-quotes as appropriate
    pprInfixName  n = pprInfixVar (isSymOcc (getOccName n)) (ppr n)

    pprPrefixName :: NamedThing a => a -> SDoc
    pprPrefixName thing
     | name `hasKey` starKindTyConKey || name `hasKey` unicodeStarKindTyConKey
     = ppr name   -- See Note [Special treatment for kind *]
     | otherwise
     = pprPrefixVar (isSymOcc (nameOccName name)) (ppr name)
     where
       name = getName thing

    {-
    Note [Special treatment for kind *]
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    Do not put parens around the kind '*'.  Even though it looks like
    an operator, it is really a special case.

    This pprPrefixName stuff is really only used when printing HsSyn,
    which has to be polymorphic in the name type, and hence has to go via
    the overloaded function pprPrefixOcc.  It's easier where we know the
    type being pretty printed; eg the pretty-printing code in TyCoRep.

    See Trac #7645, which led to this.
    -}