    {-
    (c) The University of Glasgow 2006-2012
    (c) The GRASP Project, Glasgow University, 1992-1998
    -}

    -- | This module defines classes and functions for pretty-printing. It also
    -- exports a number of helpful debugging and other utilities such as 'trace' and 'panic'.
    --
    -- The interface to this module is very similar to the standard Hughes-PJ pretty printing
    -- module, except that it exports a number of additional functions that are rarely used,
    -- and works over the 'SDoc' type.
    module Outputable (
            -- * Type classes
            Outputable(..), OutputableBndr(..),

            -- * Pretty printing combinators
            SDoc, runSDoc, initSDocContext,
            docToSDoc,
            interppSP, interpp'SP, pprQuotedList, pprWithCommas, quotedListWithOr,
            empty, nest,
            char,
            text, ftext, ptext, ztext,
            int, intWithCommas, integer, float, double, rational,
            parens, cparen, brackets, braces, quotes, quote,
            doubleQuotes, angleBrackets, paBrackets,
            semi, comma, colon, dcolon, space, equals, dot,
            arrow, larrow, darrow, arrowt, larrowt, arrowtt, larrowtt,
            lparen, rparen, lbrack, rbrack, lbrace, rbrace, underscore,
            blankLine, forAllLit,
            (<>), (<+>), hcat, hsep,
            ($$), ($+$), vcat,
            sep, cat,
            fsep, fcat,
            hang, punctuate, ppWhen, ppUnless,
            speakNth, speakNTimes, speakN, speakNOf, plural, isOrAre,

            coloured, PprColour, colType, colCoerc, colDataCon,
            colBinder, bold, keyword,

            -- * Converting 'SDoc' into strings and outputing it
            printForC, printForAsm, printForUser, printForUserPartWay,
            pprCode, mkCodeStyle,
            showSDoc, showSDocUnsafe, showSDocOneLine,
            showSDocForUser, showSDocDebug, showSDocDump, showSDocDumpOneLine,
            showSDocUnqual, showPpr,
            renderWithStyle,

            pprInfixVar, pprPrefixVar,
            pprHsChar, pprHsString, pprHsBytes,
            pprFastFilePath,

            -- * Controlling the style in which output is printed
            BindingSite(..),

            PprStyle, CodeStyle(..), PrintUnqualified(..),
            QueryQualifyName, QueryQualifyModule, QueryQualifyPackage,
            reallyAlwaysQualify, reallyAlwaysQualifyNames,
            alwaysQualify, alwaysQualifyNames, alwaysQualifyModules,
            neverQualify, neverQualifyNames, neverQualifyModules,
            QualifyName(..), queryQual,
            sdocWithDynFlags, sdocWithPlatform,
            getPprStyle, withPprStyle, withPprStyleDoc,
            pprDeeper, pprDeeperList, pprSetDepth,
            codeStyle, userStyle, debugStyle, dumpStyle, asmStyle,
            ifPprDebug, qualName, qualModule, qualPackage,
            mkErrStyle, defaultErrStyle, defaultDumpStyle, mkDumpStyle, defaultUserStyle,
            mkUserStyle, cmdlineParserStyle, Depth(..),

            -- * Error handling and debugging utilities
            pprPanic, pprSorry, assertPprPanic, pprPanicFastInt, pprPgmError,
            pprTrace, warnPprTrace,
            trace, pgmError, panic, sorry, panicFastInt, assertPanic,
            pprDebugAndThen,
        ) where

    import {-# SOURCE #-}   DynFlags( DynFlags,
                                      targetPlatform, pprUserLength, pprCols,
                                      useUnicode, useUnicodeSyntax,
                                      unsafeGlobalDynFlags )
    import {-# SOURCE #-}   Module( PackageKey, Module, ModuleName, moduleName )
    import {-# SOURCE #-}   OccName( OccName )
    import {-# SOURCE #-}   StaticFlags( opt_PprStyle_Debug, opt_NoDebugOutput )

    import FastString
    import FastTypes
    import qualified Pretty
    import Util
    import Platform
    import Pretty           ( Doc, Mode(..) )
    import Panic

    import Data.ByteString (ByteString)
    import qualified Data.ByteString as BS
    import Data.Char
    import qualified Data.Map as M
    import Data.Int
    import qualified Data.IntMap as IM
    import Data.Set (Set)
    import qualified Data.Set as Set
    import Data.Word
    import System.IO        ( Handle )
    import System.FilePath
    import Text.Printf

    import GHC.Fingerprint
    import GHC.Show         ( showMultiLineString )

    {-
    ************************************************************************
    *                                                                      *
    \subsection{The @PprStyle@ data type}
    *                                                                      *
    ************************************************************************
    -}

    data PprStyle
      = PprUser PrintUnqualified Depth
                    -- Pretty-print in a way that will make sense to the
                    -- ordinary user; must be very close to Haskell
                    -- syntax, etc.
                    -- Assumes printing tidied code: non-system names are
                    -- printed without uniques.

      | PprDump PrintUnqualified
                    -- For -ddump-foo; less verbose than PprDebug, but more than PprUser
                    -- Does not assume tidied code: non-external names
                    -- are printed with uniques.

      | PprDebug    -- Full debugging output

      | PprCode CodeStyle
                    -- Print code; either C or assembler

    data CodeStyle = CStyle         -- The format of labels differs for C and assembler
                   | AsmStyle

    data Depth = AllTheWay
               | PartWay Int        -- 0 => stop

    -- -----------------------------------------------------------------------------
    -- Printing original names

    -- | When printing code that contains original names, we need to map the
    -- original names back to something the user understands.  This is the
    -- purpose of the triple of functions that gets passed around
    -- when rendering 'SDoc'.
    data PrintUnqualified = QueryQualify {
        queryQualifyName    :: QueryQualifyName,
        queryQualifyModule  :: QueryQualifyModule,
        queryQualifyPackage :: QueryQualifyPackage
    }

    -- | given an /original/ name, this function tells you which module
    -- name it should be qualified with when printing for the user, if
    -- any.  For example, given @Control.Exception.catch@, which is in scope
    -- as @Exception.catch@, this fuction will return @Just "Exception"@.
    -- Note that the return value is a ModuleName, not a Module, because
    -- in source code, names are qualified by ModuleNames.
    type QueryQualifyName = Module -> OccName -> QualifyName

    -- | For a given module, we need to know whether to print it with
    -- a package name to disambiguate it.
    type QueryQualifyModule = Module -> Bool

    -- | For a given package, we need to know whether to print it with
    -- the package key to disambiguate it.
    type QueryQualifyPackage = PackageKey -> Bool

    -- See Note [Printing original names] in HscTypes
    data QualifyName                        -- given P:M.T
            = NameUnqual                    -- refer to it as "T"
            | NameQual ModuleName           -- refer to it as "X.T" for the supplied X
            | NameNotInScope1
                    -- it is not in scope at all, but M.T is not bound in the current
                    -- scope, so we can refer to it as "M.T"
            | NameNotInScope2
                    -- it is not in scope at all, and M.T is already bound in the
                    -- current scope, so we must refer to it as "P:M.T"

    reallyAlwaysQualifyNames :: QueryQualifyName
    reallyAlwaysQualifyNames _ _ = NameNotInScope2

    -- | NB: This won't ever show package IDs
    alwaysQualifyNames :: QueryQualifyName
    alwaysQualifyNames m _ = NameQual (moduleName m)

    neverQualifyNames :: QueryQualifyName
    neverQualifyNames _ _ = NameUnqual

    alwaysQualifyModules :: QueryQualifyModule
    alwaysQualifyModules _ = True

    neverQualifyModules :: QueryQualifyModule
    neverQualifyModules _ = False

    alwaysQualifyPackages :: QueryQualifyPackage
    alwaysQualifyPackages _ = True

    neverQualifyPackages :: QueryQualifyPackage
    neverQualifyPackages _ = False

    reallyAlwaysQualify, alwaysQualify, neverQualify :: PrintUnqualified
    reallyAlwaysQualify
                  = QueryQualify reallyAlwaysQualifyNames
                                 alwaysQualifyModules
                                 alwaysQualifyPackages
    alwaysQualify = QueryQualify alwaysQualifyNames
                                 alwaysQualifyModules
                                 alwaysQualifyPackages
    neverQualify  = QueryQualify neverQualifyNames
                                 neverQualifyModules
                                 neverQualifyPackages

    defaultUserStyle, defaultDumpStyle :: PprStyle

    defaultUserStyle = mkUserStyle neverQualify AllTheWay
     -- Print without qualifiers to reduce verbosity, unless -dppr-debug

    defaultDumpStyle |  opt_PprStyle_Debug = PprDebug
                     |  otherwise          = PprDump neverQualify

    mkDumpStyle :: PrintUnqualified -> PprStyle
    mkDumpStyle print_unqual | opt_PprStyle_Debug = PprDebug
                             | otherwise          = PprDump print_unqual

    defaultErrStyle :: DynFlags -> PprStyle
    -- Default style for error messages, when we don't know PrintUnqualified
    -- It's a bit of a hack because it doesn't take into account what's in scope
    -- Only used for desugarer warnings, and typechecker errors in interface sigs
    -- NB that -dppr-debug will still get into PprDebug style
    defaultErrStyle dflags = mkErrStyle dflags neverQualify

    -- | Style for printing error messages
    mkErrStyle :: DynFlags -> PrintUnqualified -> PprStyle
    mkErrStyle dflags qual = mkUserStyle qual (PartWay (pprUserLength dflags))

    cmdlineParserStyle :: PprStyle
    cmdlineParserStyle = mkUserStyle alwaysQualify AllTheWay

    mkUserStyle :: PrintUnqualified -> Depth -> PprStyle
    mkUserStyle unqual depth
       | opt_PprStyle_Debug = PprDebug
       | otherwise          = PprUser unqual depth

    {-
    Orthogonal to the above printing styles are (possibly) some
    command-line flags that affect printing (often carried with the
    style).  The most likely ones are variations on how much type info is
    shown.

    The following test decides whether or not we are actually generating
    code (either C or assembly), or generating interface files.

    ************************************************************************
    *                                                                      *
    \subsection{The @SDoc@ data type}
    *                                                                      *
    ************************************************************************
    -}

    newtype SDoc = SDoc { runSDoc :: SDocContext -> Doc }

    data SDocContext = SDC
      { sdocStyle      :: !PprStyle
      , sdocLastColour :: !PprColour
        -- ^ The most recently used colour.  This allows nesting colours.
      , sdocDynFlags   :: !DynFlags
      }

    initSDocContext :: DynFlags -> PprStyle -> SDocContext
    initSDocContext dflags sty = SDC
      { sdocStyle = sty
      , sdocLastColour = colReset
      , sdocDynFlags = dflags
      }

    withPprStyle :: PprStyle -> SDoc -> SDoc
    withPprStyle sty d = SDoc $ \ctxt -> runSDoc d ctxt{sdocStyle=sty}

    withPprStyleDoc :: DynFlags -> PprStyle -> SDoc -> Doc
    withPprStyleDoc dflags sty d = runSDoc d (initSDocContext dflags sty)

    pprDeeper :: SDoc -> SDoc
    pprDeeper d = SDoc $ \ctx -> case ctx of
      SDC{sdocStyle=PprUser _ (PartWay 0)} -> Pretty.text "..."
      SDC{sdocStyle=PprUser q (PartWay n)} ->
        runSDoc d ctx{sdocStyle = PprUser q (PartWay (n-1))}
      _ -> runSDoc d ctx

    pprDeeperList :: ([SDoc] -> SDoc) -> [SDoc] -> SDoc
    -- Truncate a list that list that is longer than the current depth
    pprDeeperList f ds
      | null ds   = f []
      | otherwise = SDoc work
     where
      work ctx@SDC{sdocStyle=PprUser q (PartWay n)}
       | n==0      = Pretty.text "..."
       | otherwise =
          runSDoc (f (go 0 ds)) ctx{sdocStyle = PprUser q (PartWay (n-1))}
       where
         go _ [] = []
         go i (d:ds) | i >= n    = [text "...."]
                     | otherwise = d : go (i+1) ds
      work other_ctx = runSDoc (f ds) other_ctx

    pprSetDepth :: Depth -> SDoc -> SDoc
    pprSetDepth depth doc = SDoc $ \ctx ->
        case ctx of
            SDC{sdocStyle=PprUser q _} ->
                runSDoc doc ctx{sdocStyle = PprUser q depth}
            _ ->
                runSDoc doc ctx

    getPprStyle :: (PprStyle -> SDoc) -> SDoc
    getPprStyle df = SDoc $ \ctx -> runSDoc (df (sdocStyle ctx)) ctx

    sdocWithDynFlags :: (DynFlags -> SDoc) -> SDoc
    sdocWithDynFlags f = SDoc $ \ctx -> runSDoc (f (sdocDynFlags ctx)) ctx

    sdocWithPlatform :: (Platform -> SDoc) -> SDoc
    sdocWithPlatform f = sdocWithDynFlags (f . targetPlatform)

    qualName :: PprStyle -> QueryQualifyName
    qualName (PprUser q _)  mod occ = queryQualifyName q mod occ
    qualName (PprDump q)    mod occ = queryQualifyName q mod occ
    qualName _other         mod _   = NameQual (moduleName mod)

    qualModule :: PprStyle -> QueryQualifyModule
    qualModule (PprUser q _)  m = queryQualifyModule q m
    qualModule (PprDump q)    m = queryQualifyModule q m
    qualModule _other        _m = True

    qualPackage :: PprStyle -> QueryQualifyPackage
    qualPackage (PprUser q _)  m = queryQualifyPackage q m
    qualPackage (PprDump q)    m = queryQualifyPackage q m
    qualPackage _other        _m = True

    queryQual :: PprStyle -> PrintUnqualified
    queryQual s = QueryQualify (qualName s)
                               (qualModule s)
                               (qualPackage s)

    codeStyle :: PprStyle -> Bool
    codeStyle (PprCode _)     = True
    codeStyle _               = False

    asmStyle :: PprStyle -> Bool
    asmStyle (PprCode AsmStyle)  = True
    asmStyle _other              = False

    dumpStyle :: PprStyle -> Bool
    dumpStyle (PprDump {}) = True
    dumpStyle _other       = False

    debugStyle :: PprStyle -> Bool
    debugStyle PprDebug = True
    debugStyle _other   = False

    userStyle ::  PprStyle -> Bool
    userStyle (PprUser _ _) = True
    userStyle _other        = False

    ifPprDebug :: SDoc -> SDoc        -- Empty for non-debug style
    ifPprDebug d = SDoc $ \ctx ->
        case ctx of
            SDC{sdocStyle=PprDebug} -> runSDoc d ctx
            _                       -> Pretty.empty

    printForUser :: DynFlags -> Handle -> PrintUnqualified -> SDoc -> IO ()
    printForUser dflags handle unqual doc
      = Pretty.printDoc PageMode (pprCols dflags) handle
          (runSDoc doc (initSDocContext dflags (mkUserStyle unqual AllTheWay)))

    printForUserPartWay :: DynFlags -> Handle -> Int -> PrintUnqualified -> SDoc
                        -> IO ()
    printForUserPartWay dflags handle d unqual doc
      = Pretty.printDoc PageMode (pprCols dflags) handle
          (runSDoc doc (initSDocContext dflags (mkUserStyle unqual (PartWay d))))

    -- printForC, printForAsm do what they sound like
    printForC :: DynFlags -> Handle -> SDoc -> IO ()
    printForC dflags handle doc =
      Pretty.printDoc LeftMode (pprCols dflags) handle
        (runSDoc doc (initSDocContext dflags (PprCode CStyle)))

    printForAsm :: DynFlags -> Handle -> SDoc -> IO ()
    printForAsm dflags handle doc =
      Pretty.printDoc LeftMode (pprCols dflags) handle
        (runSDoc doc (initSDocContext dflags (PprCode AsmStyle)))

    pprCode :: CodeStyle -> SDoc -> SDoc
    pprCode cs d = withPprStyle (PprCode cs) d

    mkCodeStyle :: CodeStyle -> PprStyle
    mkCodeStyle = PprCode

    -- Can't make SDoc an instance of Show because SDoc is just a function type
    -- However, Doc *is* an instance of Show
    -- showSDoc just blasts it out as a string
    showSDoc :: DynFlags -> SDoc -> String
    showSDoc dflags sdoc = renderWithStyle dflags sdoc defaultUserStyle

    -- showSDocUnsafe is unsafe, because `unsafeGlobalDynFlags` might not be
    -- initialised yet.
    showSDocUnsafe :: SDoc -> String
    showSDocUnsafe sdoc = showSDoc unsafeGlobalDynFlags sdoc

    showPpr :: Outputable a => DynFlags -> a -> String
    showPpr dflags thing = showSDoc dflags (ppr thing)

    showSDocUnqual :: DynFlags -> SDoc -> String
    -- Only used by Haddock
    showSDocUnqual dflags sdoc = showSDoc dflags sdoc

    showSDocForUser :: DynFlags -> PrintUnqualified -> SDoc -> String
    -- Allows caller to specify the PrintUnqualified to use
    showSDocForUser dflags unqual doc
     = renderWithStyle dflags doc (mkUserStyle unqual AllTheWay)

    showSDocDump :: DynFlags -> SDoc -> String
    showSDocDump dflags d = renderWithStyle dflags d defaultDumpStyle

    showSDocDebug :: DynFlags -> SDoc -> String
    showSDocDebug dflags d = renderWithStyle dflags d PprDebug

    renderWithStyle :: DynFlags -> SDoc -> PprStyle -> String
    renderWithStyle dflags sdoc sty
      = Pretty.showDoc PageMode (pprCols dflags) $
        runSDoc sdoc (initSDocContext dflags sty)

    -- This shows an SDoc, but on one line only. It's cheaper than a full
    -- showSDoc, designed for when we're getting results like "Foo.bar"
    -- and "foo{uniq strictness}" so we don't want fancy layout anyway.
    showSDocOneLine :: DynFlags -> SDoc -> String
    showSDocOneLine dflags d
     = Pretty.showDoc OneLineMode (pprCols dflags) $
       runSDoc d (initSDocContext dflags defaultUserStyle)

    showSDocDumpOneLine :: DynFlags -> SDoc -> String
    showSDocDumpOneLine dflags d
     = Pretty.showDoc OneLineMode irrelevantNCols $
       runSDoc d (initSDocContext dflags defaultDumpStyle)

    irrelevantNCols :: Int
    -- Used for OneLineMode and LeftMode when number of cols isn't used
    irrelevantNCols = 1

    docToSDoc :: Doc -> SDoc
    docToSDoc d = SDoc (\_ -> d)

    empty    :: SDoc
    char     :: Char       -> SDoc
    text     :: String     -> SDoc
    ftext    :: FastString -> SDoc
    ptext    :: LitString  -> SDoc
    ztext    :: FastZString -> SDoc
    int      :: Int        -> SDoc
    integer  :: Integer    -> SDoc
    float    :: Float      -> SDoc
    double   :: Double     -> SDoc
    rational :: Rational   -> SDoc

    empty       = docToSDoc $ Pretty.empty
    char c      = docToSDoc $ Pretty.char c

    text s      = docToSDoc $ Pretty.text s
    {-# INLINE text #-}   -- Inline so that the RULE Pretty.text will fire

    ftext s     = docToSDoc $ Pretty.ftext s
    ptext s     = docToSDoc $ Pretty.ptext s
    ztext s     = docToSDoc $ Pretty.ztext s
    int n       = docToSDoc $ Pretty.int n
    integer n   = docToSDoc $ Pretty.integer n
    float n     = docToSDoc $ Pretty.float n
    double n    = docToSDoc $ Pretty.double n
    rational n  = docToSDoc $ Pretty.rational n

    parens, braces, brackets, quotes, quote,
            paBrackets, doubleQuotes, angleBrackets :: SDoc -> SDoc

    parens d        = SDoc $ Pretty.parens . runSDoc d
    braces d        = SDoc $ Pretty.braces . runSDoc d
    brackets d      = SDoc $ Pretty.brackets . runSDoc d
    quote d         = SDoc $ Pretty.quote . runSDoc d
    doubleQuotes d  = SDoc $ Pretty.doubleQuotes . runSDoc d
    angleBrackets d = char '<' <> d <> char '>'
    paBrackets d    = ptext (sLit "[:") <> d <> ptext (sLit ":]")

    cparen :: Bool -> SDoc -> SDoc

    cparen b d     = SDoc $ Pretty.cparen b . runSDoc d

    -- 'quotes' encloses something in single quotes...
    -- but it omits them if the thing begins or ends in a single quote
    -- so that we don't get `foo''.  Instead we just have foo'.
    quotes d =
          sdocWithDynFlags $ \dflags ->
          if useUnicode dflags
          then char '‘' <> d <> char '’'
          else SDoc $ \sty ->
               let pp_d = runSDoc d sty
                   str  = show pp_d
               in case (str, snocView str) of
                 (_, Just (_, '\'')) -> pp_d
                 ('\'' : _, _)       -> pp_d
                 _other              -> Pretty.quotes pp_d

    semi, comma, colon, equals, space, dcolon, underscore, dot :: SDoc
    arrow, larrow, darrow, arrowt, larrowt, arrowtt, larrowtt :: SDoc
    lparen, rparen, lbrack, rbrack, lbrace, rbrace, blankLine :: SDoc

    blankLine  = docToSDoc $ Pretty.ptext (sLit "")
    dcolon     = unicodeSyntax (char '∷') (docToSDoc $ Pretty.ptext (sLit "::"))
    arrow      = unicodeSyntax (char '→') (docToSDoc $ Pretty.ptext (sLit "->"))
    larrow     = unicodeSyntax (char '←') (docToSDoc $ Pretty.ptext (sLit "<-"))
    darrow     = unicodeSyntax (char '⇒') (docToSDoc $ Pretty.ptext (sLit "=>"))
    arrowt     = unicodeSyntax (char '↣') (docToSDoc $ Pretty.ptext (sLit ">-"))
    larrowt    = unicodeSyntax (char '↢') (docToSDoc $ Pretty.ptext (sLit "-<"))
    arrowtt    = unicodeSyntax (char '⤜') (docToSDoc $ Pretty.ptext (sLit ">>-"))
    larrowtt   = unicodeSyntax (char '⤛') (docToSDoc $ Pretty.ptext (sLit "-<<"))
    semi       = docToSDoc $ Pretty.semi
    comma      = docToSDoc $ Pretty.comma
    colon      = docToSDoc $ Pretty.colon
    equals     = docToSDoc $ Pretty.equals
    space      = docToSDoc $ Pretty.space
    underscore = char '_'
    dot        = char '.'
    lparen     = docToSDoc $ Pretty.lparen
    rparen     = docToSDoc $ Pretty.rparen
    lbrack     = docToSDoc $ Pretty.lbrack
    rbrack     = docToSDoc $ Pretty.rbrack
    lbrace     = docToSDoc $ Pretty.lbrace
    rbrace     = docToSDoc $ Pretty.rbrace

    forAllLit :: SDoc
    forAllLit = unicodeSyntax (char '∀') (ptext (sLit "forall"))

    unicodeSyntax :: SDoc -> SDoc -> SDoc
    unicodeSyntax unicode plain = sdocWithDynFlags $ \dflags ->
        if useUnicode dflags && useUnicodeSyntax dflags
        then unicode
        else plain

    nest :: Int -> SDoc -> SDoc
    -- ^ Indent 'SDoc' some specified amount
    (<>) :: SDoc -> SDoc -> SDoc
    -- ^ Join two 'SDoc' together horizontally without a gap
    (<+>) :: SDoc -> SDoc -> SDoc
    -- ^ Join two 'SDoc' together horizontally with a gap between them
    ($$) :: SDoc -> SDoc -> SDoc
    -- ^ Join two 'SDoc' together vertically; if there is
    -- no vertical overlap it "dovetails" the two onto one line
    ($+$) :: SDoc -> SDoc -> SDoc
    -- ^ Join two 'SDoc' together vertically

    nest n d    = SDoc $ Pretty.nest n . runSDoc d
    (<>) d1 d2  = SDoc $ \sty -> (Pretty.<>)  (runSDoc d1 sty) (runSDoc d2 sty)
    (<+>) d1 d2 = SDoc $ \sty -> (Pretty.<+>) (runSDoc d1 sty) (runSDoc d2 sty)
    ($$) d1 d2  = SDoc $ \sty -> (Pretty.$$)  (runSDoc d1 sty) (runSDoc d2 sty)
    ($+$) d1 d2 = SDoc $ \sty -> (Pretty.$+$) (runSDoc d1 sty) (runSDoc d2 sty)

    hcat :: [SDoc] -> SDoc
    -- ^ Concatenate 'SDoc' horizontally
    hsep :: [SDoc] -> SDoc
    -- ^ Concatenate 'SDoc' horizontally with a space between each one
    vcat :: [SDoc] -> SDoc
    -- ^ Concatenate 'SDoc' vertically with dovetailing
    sep :: [SDoc] -> SDoc
    -- ^ Separate: is either like 'hsep' or like 'vcat', depending on what fits
    cat :: [SDoc] -> SDoc
    -- ^ Catenate: is either like 'hcat' or like 'vcat', depending on what fits
    fsep :: [SDoc] -> SDoc
    -- ^ A paragraph-fill combinator. It's much like sep, only it
    -- keeps fitting things on one line until it can't fit any more.
    fcat :: [SDoc] -> SDoc
    -- ^ This behaves like 'fsep', but it uses '<>' for horizontal conposition rather than '<+>'

    hcat ds = SDoc $ \sty -> Pretty.hcat [runSDoc d sty | d <- ds]
    hsep ds = SDoc $ \sty -> Pretty.hsep [runSDoc d sty | d <- ds]
    vcat ds = SDoc $ \sty -> Pretty.vcat [runSDoc d sty | d <- ds]
    sep ds  = SDoc $ \sty -> Pretty.sep  [runSDoc d sty | d <- ds]
    cat ds  = SDoc $ \sty -> Pretty.cat  [runSDoc d sty | d <- ds]
    fsep ds = SDoc $ \sty -> Pretty.fsep [runSDoc d sty | d <- ds]
    fcat ds = SDoc $ \sty -> Pretty.fcat [runSDoc d sty | d <- ds]

    hang :: SDoc  -- ^ The header
          -> Int  -- ^ Amount to indent the hung body
          -> SDoc -- ^ The hung body, indented and placed below the header
          -> SDoc
    hang d1 n d2   = SDoc $ \sty -> Pretty.hang (runSDoc d1 sty) n (runSDoc d2 sty)

    punctuate :: SDoc   -- ^ The punctuation
              -> [SDoc] -- ^ The list that will have punctuation added between every adjacent pair of elements
              -> [SDoc] -- ^ Punctuated list
    punctuate _ []     = []
    punctuate p (d:ds) = go d ds
                       where
                         go d [] = [d]
                         go d (e:es) = (d <> p) : go e es

    ppWhen, ppUnless :: Bool -> SDoc -> SDoc
    ppWhen True  doc = doc
    ppWhen False _   = empty

    ppUnless True  _   = empty
    ppUnless False doc = doc

    -- | A colour\/style for use with 'coloured'.
    newtype PprColour = PprColour String

    -- Colours

    colType :: PprColour
    colType = PprColour "\27[34m"

    colBold :: PprColour
    colBold = PprColour "\27[;1m"

    colCoerc :: PprColour
    colCoerc = PprColour "\27[34m"

    colDataCon :: PprColour
    colDataCon = PprColour "\27[31m"

    colBinder :: PprColour
    colBinder = PprColour "\27[32m"

    colReset :: PprColour
    colReset = PprColour "\27[0m"

    -- | Apply the given colour\/style for the argument.
    --
    -- Only takes effect if colours are enabled.
    coloured :: PprColour -> SDoc -> SDoc
    -- TODO: coloured _ sdoc ctxt | coloursDisabled = sdoc ctxt
    coloured col@(PprColour c) sdoc =
      SDoc $ \ctx@SDC{ sdocLastColour = PprColour lc } ->
        let ctx' = ctx{ sdocLastColour = col } in
        Pretty.zeroWidthText c Pretty.<> runSDoc sdoc ctx' Pretty.<> Pretty.zeroWidthText lc

    bold :: SDoc -> SDoc
    bold = coloured colBold

    keyword :: SDoc -> SDoc
    keyword = bold

    {-
    ************************************************************************
    *                                                                      *
    \subsection[Outputable-class]{The @Outputable@ class}
    *                                                                      *
    ************************************************************************
    -}

    -- | Class designating that some type has an 'SDoc' representation
    class Outputable a where
            ppr :: a -> SDoc
            pprPrec :: Rational -> a -> SDoc
                    -- 0 binds least tightly
                    -- We use Rational because there is always a
                    -- Rational between any other two Rationals

            ppr = pprPrec 0
            pprPrec _ = ppr

    instance Outputable Char where
        ppr c = text [c]

    instance Outputable Bool where
        ppr True  = ptext (sLit "True")
        ppr False = ptext (sLit "False")

    instance Outputable Int32 where
       ppr n = integer $ fromIntegral n

    instance Outputable Int64 where
       ppr n = integer $ fromIntegral n

    instance Outputable Int where
        ppr n = int n

    instance Outputable Word16 where
        ppr n = integer $ fromIntegral n

    instance Outputable Word32 where
        ppr n = integer $ fromIntegral n

    instance Outputable Word where
        ppr n = integer $ fromIntegral n

    instance Outputable () where
        ppr _ = text "()"

    instance (Outputable a) => Outputable [a] where
        ppr xs = brackets (fsep (punctuate comma (map ppr xs)))

    instance (Outputable a) => Outputable (Set a) where
        ppr s = braces (fsep (punctuate comma (map ppr (Set.toList s))))

    instance (Outputable a, Outputable b) => Outputable (a, b) where
        ppr (x,y) = parens (sep [ppr x <> comma, ppr y])

    instance Outputable a => Outputable (Maybe a) where
        ppr Nothing = ptext (sLit "Nothing")
        ppr (Just x) = ptext (sLit "Just") <+> ppr x

    instance (Outputable a, Outputable b) => Outputable (Either a b) where
        ppr (Left x)  = ptext (sLit "Left")  <+> ppr x
        ppr (Right y) = ptext (sLit "Right") <+> ppr y

    -- ToDo: may not be used
    instance (Outputable a, Outputable b, Outputable c) => Outputable (a, b, c) where
        ppr (x,y,z) =
          parens (sep [ppr x <> comma,
                       ppr y <> comma,
                       ppr z ])

    instance (Outputable a, Outputable b, Outputable c, Outputable d) =>
             Outputable (a, b, c, d) where
        ppr (a,b,c,d) =
          parens (sep [ppr a <> comma,
                       ppr b <> comma,
                       ppr c <> comma,
                       ppr d])

    instance (Outputable a, Outputable b, Outputable c, Outputable d, Outputable e) =>
             Outputable (a, b, c, d, e) where
        ppr (a,b,c,d,e) =
          parens (sep [ppr a <> comma,
                       ppr b <> comma,
                       ppr c <> comma,
                       ppr d <> comma,
                       ppr e])

    instance (Outputable a, Outputable b, Outputable c, Outputable d, Outputable e, Outputable f) =>
             Outputable (a, b, c, d, e, f) where
        ppr (a,b,c,d,e,f) =
          parens (sep [ppr a <> comma,
                       ppr b <> comma,
                       ppr c <> comma,
                       ppr d <> comma,
                       ppr e <> comma,
                       ppr f])

    instance (Outputable a, Outputable b, Outputable c, Outputable d, Outputable e, Outputable f, Outputable g) =>
             Outputable (a, b, c, d, e, f, g) where
        ppr (a,b,c,d,e,f,g) =
          parens (sep [ppr a <> comma,
                       ppr b <> comma,
                       ppr c <> comma,
                       ppr d <> comma,
                       ppr e <> comma,
                       ppr f <> comma,
                       ppr g])

    instance Outputable FastString where
        ppr fs = ftext fs           -- Prints an unadorned string,
                                    -- no double quotes or anything

    instance (Outputable key, Outputable elt) => Outputable (M.Map key elt) where
        ppr m = ppr (M.toList m)
    instance (Outputable elt) => Outputable (IM.IntMap elt) where
        ppr m = ppr (IM.toList m)

    instance Outputable Fingerprint where
        ppr (Fingerprint w1 w2) = text (printf "%016x%016x" w1 w2)

    {-
    ************************************************************************
    *                                                                      *
    \subsection{The @OutputableBndr@ class}
    *                                                                      *
    ************************************************************************
    -}

    -- | 'BindingSite' is used to tell the thing that prints binder what
    -- language construct is binding the identifier.  This can be used
    -- to decide how much info to print.
    data BindingSite = LambdaBind | CaseBind | LetBind

    -- | When we print a binder, we often want to print its type too.
    -- The @OutputableBndr@ class encapsulates this idea.
    class Outputable a => OutputableBndr a where
       pprBndr :: BindingSite -> a -> SDoc
       pprBndr _b x = ppr x

       pprPrefixOcc, pprInfixOcc :: a -> SDoc
          -- Print an occurrence of the name, suitable either in the
          -- prefix position of an application, thus   (f a b) or  ((+) x)
          -- or infix position,                 thus   (a `f` b) or  (x + y)

    {-
    ************************************************************************
    *                                                                      *
    \subsection{Random printing helpers}
    *                                                                      *
    ************************************************************************
    -}

    -- We have 31-bit Chars and will simply use Show instances of Char and String.

    -- | Special combinator for showing character literals.
    pprHsChar :: Char -> SDoc
    pprHsChar c | c > '\x10ffff' = char '\\' <> text (show (fromIntegral (ord c) :: Word32))
                | otherwise      = text (show c)

    -- | Special combinator for showing string literals.
    pprHsString :: FastString -> SDoc
    pprHsString fs = vcat (map text (showMultiLineString (unpackFS fs)))

    -- | Special combinator for showing string literals.
    pprHsBytes :: ByteString -> SDoc
    pprHsBytes bs = let escaped = concatMap escape $ BS.unpack bs
                    in vcat (map text (showMultiLineString escaped)) <> char '#'
        where escape :: Word8 -> String
              escape w = let c = chr (fromIntegral w)
                         in if isAscii c
                            then [c]
                            else '\\' : show w

    ---------------------
    -- Put a name in parens if it's an operator
    pprPrefixVar :: Bool -> SDoc -> SDoc
    pprPrefixVar is_operator pp_v
      | is_operator = parens pp_v
      | otherwise   = pp_v

    -- Put a name in backquotes if it's not an operator
    pprInfixVar :: Bool -> SDoc -> SDoc
    pprInfixVar is_operator pp_v
      | is_operator = pp_v
      | otherwise   = char '`' <> pp_v <> char '`'

    ---------------------
    pprFastFilePath :: FastString -> SDoc
    pprFastFilePath path = text $ normalise $ unpackFS path

    {-
    ************************************************************************
    *                                                                      *
    \subsection{Other helper functions}
    *                                                                      *
    ************************************************************************
    -}

    pprWithCommas :: (a -> SDoc) -- ^ The pretty printing function to use
                  -> [a]         -- ^ The things to be pretty printed
                  -> SDoc        -- ^ 'SDoc' where the things have been pretty printed,
                                 -- comma-separated and finally packed into a paragraph.
    pprWithCommas pp xs = fsep (punctuate comma (map pp xs))

    -- | Returns the separated concatenation of the pretty printed things.
    interppSP  :: Outputable a => [a] -> SDoc
    interppSP  xs = sep (map ppr xs)

    -- | Returns the comma-separated concatenation of the pretty printed things.
    interpp'SP :: Outputable a => [a] -> SDoc
    interpp'SP xs = sep (punctuate comma (map ppr xs))

    -- | Returns the comma-separated concatenation of the quoted pretty printed things.
    --
    -- > [x,y,z]  ==>  `x', `y', `z'
    pprQuotedList :: Outputable a => [a] -> SDoc
    pprQuotedList = quotedList . map ppr

    quotedList :: [SDoc] -> SDoc
    quotedList xs = hsep (punctuate comma (map quotes xs))

    quotedListWithOr :: [SDoc] -> SDoc
    -- [x,y,z]  ==>  `x', `y' or `z'
    quotedListWithOr xs@(_:_:_) = quotedList (init xs) <+> ptext (sLit "or") <+> quotes (last xs)
    quotedListWithOr xs = quotedList xs

    {-
    ************************************************************************
    *                                                                      *
    \subsection{Printing numbers verbally}
    *                                                                      *
    ************************************************************************
    -}

    intWithCommas :: Integral a => a -> SDoc
    -- Prints a big integer with commas, eg 345,821
    intWithCommas n
      | n < 0     = char '-' <> intWithCommas (-n)
      | q == 0    = int (fromIntegral r)
      | otherwise = intWithCommas q <> comma <> zeroes <> int (fromIntegral r)
      where
        (q,r) = n `quotRem` 1000
        zeroes | r >= 100  = empty
               | r >= 10   = char '0'
               | otherwise = ptext (sLit "00")

    -- | Converts an integer to a verbal index:
    --
    -- > speakNth 1 = text "first"
    -- > speakNth 5 = text "fifth"
    -- > speakNth 21 = text "21st"
    speakNth :: Int -> SDoc
    speakNth 1 = ptext (sLit "first")
    speakNth 2 = ptext (sLit "second")
    speakNth 3 = ptext (sLit "third")
    speakNth 4 = ptext (sLit "fourth")
    speakNth 5 = ptext (sLit "fifth")
    speakNth 6 = ptext (sLit "sixth")
    speakNth n = hcat [ int n, text suffix ]
      where
        suffix | n <= 20       = "th"       -- 11,12,13 are non-std
               | last_dig == 1 = "st"
               | last_dig == 2 = "nd"
               | last_dig == 3 = "rd"
               | otherwise     = "th"

        last_dig = n `rem` 10

    -- | Converts an integer to a verbal multiplicity:
    --
    -- > speakN 0 = text "none"
    -- > speakN 5 = text "five"
    -- > speakN 10 = text "10"
    speakN :: Int -> SDoc
    speakN 0 = ptext (sLit "none")  -- E.g.  "he has none"
    speakN 1 = ptext (sLit "one")   -- E.g.  "he has one"
    speakN 2 = ptext (sLit "two")
    speakN 3 = ptext (sLit "three")
    speakN 4 = ptext (sLit "four")
    speakN 5 = ptext (sLit "five")
    speakN 6 = ptext (sLit "six")
    speakN n = int n

    -- | Converts an integer and object description to a statement about the
    -- multiplicity of those objects:
    --
    -- > speakNOf 0 (text "melon") = text "no melons"
    -- > speakNOf 1 (text "melon") = text "one melon"
    -- > speakNOf 3 (text "melon") = text "three melons"
    speakNOf :: Int -> SDoc -> SDoc
    speakNOf 0 d = ptext (sLit "no") <+> d <> char 's'
    speakNOf 1 d = ptext (sLit "one") <+> d                 -- E.g. "one argument"
    speakNOf n d = speakN n <+> d <> char 's'               -- E.g. "three arguments"

    -- | Converts a strictly positive integer into a number of times:
    --
    -- > speakNTimes 1 = text "once"
    -- > speakNTimes 2 = text "twice"
    -- > speakNTimes 4 = text "4 times"
    speakNTimes :: Int {- >=1 -} -> SDoc
    speakNTimes t | t == 1     = ptext (sLit "once")
                  | t == 2     = ptext (sLit "twice")
                  | otherwise  = speakN t <+> ptext (sLit "times")

    -- | Determines the pluralisation suffix appropriate for the length of a list:
    --
    -- > plural [] = char 's'
    -- > plural ["Hello"] = empty
    -- > plural ["Hello", "World"] = char 's'
    plural :: [a] -> SDoc
    plural [_] = empty  -- a bit frightening, but there you are
    plural _   = char 's'

    -- | Determines the form of to be appropriate for the length of a list:
    --
    -- > isOrAre [] = ptext (sLit "are")
    -- > isOrAre ["Hello"] = ptext (sLit "is")
    -- > isOrAre ["Hello", "World"] = ptext (sLit "are")
    isOrAre :: [a] -> SDoc
    isOrAre [_] = ptext (sLit "is")
    isOrAre _   = ptext (sLit "are")

    {-
    ************************************************************************
    *                                                                      *
    \subsection{Error handling}
    *                                                                      *
    ************************************************************************
    -}

    pprPanic :: String -> SDoc -> a
    -- ^ Throw an exception saying "bug in GHC"
    pprPanic    = panicDoc

    pprSorry :: String -> SDoc -> a
    -- ^ Throw an exception saying "this isn't finished yet"
    pprSorry    = sorryDoc

    pprPgmError :: String -> SDoc -> a
    -- ^ Throw an exception saying "bug in pgm being compiled" (used for unusual program errors)
    pprPgmError = pgmErrorDoc

    pprTrace :: String -> SDoc -> a -> a
    -- ^ If debug output is on, show some 'SDoc' on the screen
    pprTrace str doc x
       | opt_NoDebugOutput = x
       | otherwise         = pprDebugAndThen unsafeGlobalDynFlags trace (text str) doc x

    pprPanicFastInt :: String -> SDoc -> FastInt
    -- ^ Specialization of pprPanic that can be safely used with 'FastInt'
    pprPanicFastInt heading pretty_msg = panicDocFastInt heading pretty_msg

    warnPprTrace :: Bool -> String -> Int -> SDoc -> a -> a
    -- ^ Just warn about an assertion failure, recording the given file and line number.
    -- Should typically be accessed with the WARN macros
    warnPprTrace _     _     _     _    x | not debugIsOn     = x
    warnPprTrace _     _file _line _msg x | opt_NoDebugOutput = x
    warnPprTrace False _file _line _msg x = x
    warnPprTrace True   file  line  msg x
      = pprDebugAndThen unsafeGlobalDynFlags trace heading msg x
      where
        heading = hsep [text "WARNING: file", text file <> comma, text "line", int line]

    assertPprPanic :: String -> Int -> SDoc -> a
    -- ^ Panic with an assertation failure, recording the given file and line number.
    -- Should typically be accessed with the ASSERT family of macros
    assertPprPanic file line msg
      = pprPanic "ASSERT failed!" doc
      where
        doc = sep [ hsep [ text "file", text file
                         , text "line", int line ]
                  , msg ]

    pprDebugAndThen :: DynFlags -> (String -> a) -> SDoc -> SDoc -> a
    pprDebugAndThen dflags cont heading pretty_msg
     = cont (showSDocDump dflags doc)
     where
         doc = sep [heading, nest 2 pretty_msg]