coreSyn/PprCore.hs

    {-
    (c) The University of Glasgow 2006
    (c) The AQUA Project, Glasgow University, 1996-1998

    Printing of Core syntax
    -}

    {-# LANGUAGE MultiWayIf #-}
    {-# OPTIONS_GHC -fno-warn-orphans #-}
    module PprCore (
            pprCoreExpr, pprParendExpr,
            pprCoreBinding, pprCoreBindings, pprCoreAlt,
            pprCoreBindingWithSize, pprCoreBindingsWithSize,
            pprRules, pprOptCo
        ) where

    import GhcPrelude

    import CoreSyn
    import CoreStats (exprStats)
    import Literal( pprLiteral )
    import Name( pprInfixName, pprPrefixName )
    import Var
    import Id
    import IdInfo
    import Demand
    import DataCon
    import TyCon
    import TyCoPpr
    import Coercion
    import DynFlags
    import BasicTypes
    import Maybes
    import Util
    import Outputable
    import FastString
    import SrcLoc      ( pprUserRealSpan )

    {-
    ************************************************************************
    *                                                                      *
    \subsection{Public interfaces for Core printing (excluding instances)}
    *                                                                      *
    ************************************************************************

    @pprParendCoreExpr@ puts parens around non-atomic Core expressions.
    -}

    pprCoreBindings :: OutputableBndr b => [Bind b] -> SDoc
    pprCoreBinding  :: OutputableBndr b => Bind b  -> SDoc
    pprCoreExpr     :: OutputableBndr b => Expr b  -> SDoc
    pprParendExpr   :: OutputableBndr b => Expr b  -> SDoc

    pprCoreBindings = pprTopBinds noAnn
    pprCoreBinding  = pprTopBind noAnn

    pprCoreBindingsWithSize :: [CoreBind] -> SDoc
    pprCoreBindingWithSize  :: CoreBind  -> SDoc

    pprCoreBindingsWithSize = pprTopBinds sizeAnn
    pprCoreBindingWithSize = pprTopBind sizeAnn

    instance OutputableBndr b => Outputable (Bind b) where
        ppr bind = ppr_bind noAnn bind

    instance OutputableBndr b => Outputable (Expr b) where
        ppr expr = pprCoreExpr expr

    {-
    ************************************************************************
    *                                                                      *
    \subsection{The guts}
    *                                                                      *
    ************************************************************************
    -}

    -- | A function to produce an annotation for a given right-hand-side
    type Annotation b = Expr b -> SDoc

    -- | Annotate with the size of the right-hand-side
    sizeAnn :: CoreExpr -> SDoc
    sizeAnn e = text "-- RHS size:" <+> ppr (exprStats e)

    -- | No annotation
    noAnn :: Expr b -> SDoc
    noAnn _ = empty

    pprTopBinds :: OutputableBndr a
                => Annotation a -- ^ generate an annotation to place before the
                                -- binding
                -> [Bind a]     -- ^ bindings to show
                -> SDoc         -- ^ the pretty result
    pprTopBinds ann binds = vcat (map (pprTopBind ann) binds)

    pprTopBind :: OutputableBndr a => Annotation a -> Bind a -> SDoc
    pprTopBind ann (NonRec binder expr)
     = ppr_binding ann (binder,expr) $$ blankLine

    pprTopBind _ (Rec [])
      = text "Rec { }"
    pprTopBind ann (Rec (b:bs))
      = vcat [text "Rec {",
              ppr_binding ann b,
              vcat [blankLine $$ ppr_binding ann b | b <- bs],
              text "end Rec }",
              blankLine]

    ppr_bind :: OutputableBndr b => Annotation b -> Bind b -> SDoc

    ppr_bind ann (NonRec val_bdr expr) = ppr_binding ann (val_bdr, expr)
    ppr_bind ann (Rec binds)           = vcat (map pp binds)
                                        where
                                          pp bind = ppr_binding ann bind <> semi

    ppr_binding :: OutputableBndr b => Annotation b -> (b, Expr b) -> SDoc
    ppr_binding ann (val_bdr, expr)
      = sdocWithDynFlags $ \dflags ->
          vcat [ ann expr
               , if gopt Opt_SuppressTypeSignatures dflags
                   then empty
                   else pprBndr LetBind val_bdr
               , pp_bind
               ]
      where
        pp_bind = case bndrIsJoin_maybe val_bdr of
                    Nothing -> pp_normal_bind
                    Just ar -> pp_join_bind ar

        pp_normal_bind = hang (ppr val_bdr) 2 (equals <+> pprCoreExpr expr)

          -- For a join point of join arity n, we want to print j = \x1 ... xn -> e
          -- as "j x1 ... xn = e" to differentiate when a join point returns a
          -- lambda (the first rendering looks like a nullary join point returning
          -- an n-argument function).
        pp_join_bind join_arity
          | bndrs `lengthAtLeast` join_arity
          = hang (ppr val_bdr <+> sep (map (pprBndr LambdaBind) lhs_bndrs))
               2 (equals <+> pprCoreExpr rhs)
          | otherwise -- Yikes!  A join-binding with too few lambda
                      -- Lint will complain, but we don't want to crash
                      -- the pretty-printer else we can't see what's wrong
                      -- So refer to printing  j = e
          = pp_normal_bind
          where
            (bndrs, body) = collectBinders expr
            lhs_bndrs = take join_arity bndrs
            rhs       = mkLams (drop join_arity bndrs) body

    pprParendExpr expr = ppr_expr parens expr
    pprCoreExpr   expr = ppr_expr noParens expr

    noParens :: SDoc -> SDoc
    noParens pp = pp

    pprOptCo :: Coercion -> SDoc
    -- Print a coercion optionally; i.e. honouring -dsuppress-coercions
    pprOptCo co = sdocWithDynFlags $ \dflags ->
                  if gopt Opt_SuppressCoercions dflags
                  then angleBrackets (text "Co:" <> int (coercionSize co))
                  else parens (sep [ppr co, dcolon <+> ppr (coercionType co)])

    ppr_expr :: OutputableBndr b => (SDoc -> SDoc) -> Expr b -> SDoc
            -- The function adds parens in context that need
            -- an atomic value (e.g. function args)

    ppr_expr add_par (Var name)
     | isJoinId name               = add_par ((text "jump") <+> ppr name)
     | otherwise                   = ppr name
    ppr_expr add_par (Type ty)     = add_par (text "TYPE:" <+> ppr ty)       -- Weird
    ppr_expr add_par (Coercion co) = add_par (text "CO:" <+> ppr co)
    ppr_expr add_par (Lit lit)     = pprLiteral add_par lit

    ppr_expr add_par (Cast expr co)
      = add_par $ sep [pprParendExpr expr, text "`cast`" <+> pprOptCo co]

    ppr_expr add_par expr@(Lam _ _)
      = let
            (bndrs, body) = collectBinders expr
        in
        add_par $
        hang (text "\\" <+> sep (map (pprBndr LambdaBind) bndrs) <+> arrow)
             2 (pprCoreExpr body)

    ppr_expr add_par expr@(App {})
      = sdocWithDynFlags $ \dflags ->
        case collectArgs expr of { (fun, args) ->
        let
            pp_args     = sep (map pprArg args)
            val_args    = dropWhile isTypeArg args   -- Drop the type arguments for tuples
            pp_tup_args = pprWithCommas pprCoreExpr val_args
            args'
              | gopt Opt_SuppressTypeApplications dflags = val_args
              | otherwise = args
            parens
              | null args' = id
              | otherwise  = add_par
        in
        case fun of
            Var f -> case isDataConWorkId_maybe f of
                            -- Notice that we print the *worker*
                            -- for tuples in paren'd format.
                       Just dc | saturated
                               , Just sort <- tyConTuple_maybe tc
                               -> tupleParens sort pp_tup_args
                               where
                                 tc        = dataConTyCon dc
                                 saturated = val_args `lengthIs` idArity f

                       _ -> parens (hang fun_doc 2 pp_args)
                       where
                         fun_doc | isJoinId f = text "jump" <+> ppr f
                                 | otherwise  = ppr f

            _ -> parens (hang (pprParendExpr fun) 2 pp_args)
        }

    ppr_expr add_par (Case expr var ty [(con,args,rhs)])
      = sdocWithDynFlags $ \dflags ->
        if gopt Opt_PprCaseAsLet dflags
        then add_par $  -- See Note [Print case as let]
             sep [ sep [ text "let! {"
                         <+> ppr_case_pat con args
                         <+> text "~"
                         <+> ppr_bndr var
                       , text "<-" <+> ppr_expr id expr
                         <+> text "} in" ]
                 , pprCoreExpr rhs
                 ]
        else add_par $
             sep [sep [sep [ text "case" <+> pprCoreExpr expr
                           , whenPprDebug (text "return" <+> ppr ty)
                           , text "of" <+> ppr_bndr var
                           ]
                      , char '{' <+> ppr_case_pat con args <+> arrow
                      ]
                  , pprCoreExpr rhs
                  , char '}'
                  ]
      where
        ppr_bndr = pprBndr CaseBind

    ppr_expr add_par (Case expr var ty alts)
      = add_par $
        sep [sep [text "case"
                    <+> pprCoreExpr expr
                    <+> whenPprDebug (text "return" <+> ppr ty),
                  text "of" <+> ppr_bndr var <+> char '{'],
             nest 2 (vcat (punctuate semi (map pprCoreAlt alts))),
             char '}'
        ]
      where
        ppr_bndr = pprBndr CaseBind

    -- special cases: let ... in let ...
    -- ("disgusting" SLPJ)

    {-
    ppr_expr add_par (Let bind@(NonRec val_bdr rhs@(Let _ _)) body)
      = add_par $
        vcat [
          hsep [text "let {", (pprBndr LetBind val_bdr $$ ppr val_bndr), equals],
          nest 2 (pprCoreExpr rhs),
          text "} in",
          pprCoreExpr body ]

    ppr_expr add_par (Let bind@(NonRec val_bdr rhs) expr@(Let _ _))
      = add_par
        (hang (text "let {")
              2 (hsep [ppr_binding (val_bdr,rhs),
                       text "} in"])
         $$
         pprCoreExpr expr)
    -}

    -- General case (recursive case, too)
    ppr_expr add_par (Let bind expr)
      = add_par $
        sep [hang (keyword bind <+> char '{') 2 (ppr_bind noAnn bind <+> text "} in"),
             pprCoreExpr expr]
      where
        keyword (NonRec b _)
         | isJust (bndrIsJoin_maybe b) = text "join"
         | otherwise                   = text "let"
        keyword (Rec pairs)
         | ((b,_):_) <- pairs
         , isJust (bndrIsJoin_maybe b) = text "joinrec"
         | otherwise                   = text "letrec"

    ppr_expr add_par (Tick tickish expr)
      = sdocWithDynFlags $ \dflags ->
      if gopt Opt_SuppressTicks dflags
      then ppr_expr add_par expr
      else add_par (sep [ppr tickish, pprCoreExpr expr])

    pprCoreAlt :: OutputableBndr a => (AltCon, [a] , Expr a) -> SDoc
    pprCoreAlt (con, args, rhs)
      = hang (ppr_case_pat con args <+> arrow) 2 (pprCoreExpr rhs)

    ppr_case_pat :: OutputableBndr a => AltCon -> [a] -> SDoc
    ppr_case_pat (DataAlt dc) args
      | Just sort <- tyConTuple_maybe tc
      = tupleParens sort (pprWithCommas ppr_bndr args)
      where
        ppr_bndr = pprBndr CasePatBind
        tc = dataConTyCon dc

    ppr_case_pat con args
      = ppr con <+> (fsep (map ppr_bndr args))
      where
        ppr_bndr = pprBndr CasePatBind

    -- | Pretty print the argument in a function application.
    pprArg :: OutputableBndr a => Expr a -> SDoc
    pprArg (Type ty)
     = sdocWithDynFlags $ \dflags ->
       if gopt Opt_SuppressTypeApplications dflags
       then empty
       else text "@" <+> pprParendType ty
    pprArg (Coercion co) = text "@~" <+> pprOptCo co
    pprArg expr          = pprParendExpr expr

    {-
    Note [Print case as let]
    ~~~~~~~~~~~~~~~~~~~~~~~~
    Single-branch case expressions are very common:
       case x of y { I# x' ->
       case p of q { I# p' -> ... } }
    These are, in effect, just strict let's, with pattern matching.
    With -dppr-case-as-let we print them as such:
       let! { I# x' ~ y <- x } in
       let! { I# p' ~ q <- p } in ...

    Other printing bits-and-bobs used with the general @pprCoreBinding@
    and @pprCoreExpr@ functions.

    Note [Binding-site specific printing]
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

    pprCoreBinder and pprTypedLamBinder receive a BindingSite argument to adjust
    the information printed.

    Let-bound binders are printed with their full type and idInfo.

    Case-bound variables (both the case binder and pattern variables) are printed
    without a type and without their unfolding.

    Furthermore, a dead case-binder is completely ignored, while otherwise, dead
    binders are printed as "_".
    -}

    -- These instances are sadly orphans

    instance OutputableBndr Var where
      pprBndr = pprCoreBinder
      pprInfixOcc  = pprInfixName  . varName
      pprPrefixOcc = pprPrefixName . varName
      bndrIsJoin_maybe = isJoinId_maybe

    instance Outputable b => OutputableBndr (TaggedBndr b) where
      pprBndr _    b = ppr b   -- Simple
      pprInfixOcc  b = ppr b
      pprPrefixOcc b = ppr b
      bndrIsJoin_maybe (TB b _) = isJoinId_maybe b

    pprCoreBinder :: BindingSite -> Var -> SDoc
    pprCoreBinder LetBind binder
      | isTyVar binder = pprKindedTyVarBndr binder
      | otherwise      = pprTypedLetBinder binder $$
                         ppIdInfo binder (idInfo binder)

    -- Lambda bound type variables are preceded by "@"
    pprCoreBinder bind_site bndr
      = getPprStyle $ \ sty ->
        pprTypedLamBinder bind_site (debugStyle sty) bndr

    pprUntypedBinder :: Var -> SDoc
    pprUntypedBinder binder
      | isTyVar binder = text "@" <+> ppr binder    -- NB: don't print kind
      | otherwise      = pprIdBndr binder

    pprTypedLamBinder :: BindingSite -> Bool -> Var -> SDoc
    -- For lambda and case binders, show the unfolding info (usually none)
    pprTypedLamBinder bind_site debug_on var
      = sdocWithDynFlags $ \dflags ->
        case () of
        _
          | not debug_on            -- Show case-bound wild binders only if debug is on
          , CaseBind <- bind_site
          , isDeadBinder var        -> empty

          | not debug_on            -- Even dead binders can be one-shot
          , isDeadBinder var        -> char '_' <+> ppWhen (isId var)
                                                    (pprIdBndrInfo (idInfo var))

          | not debug_on            -- No parens, no kind info
          , CaseBind <- bind_site   -> pprUntypedBinder var

          | not debug_on
          , CasePatBind <- bind_site    -> pprUntypedBinder var

          | suppress_sigs dflags    -> pprUntypedBinder var

          | isTyVar var  -> parens (pprKindedTyVarBndr var)

          | otherwise    -> parens (hang (pprIdBndr var)
                                       2 (vcat [ dcolon <+> pprType (idType var)
                                               , pp_unf]))
      where
        suppress_sigs = gopt Opt_SuppressTypeSignatures

        unf_info = unfoldingInfo (idInfo var)
        pp_unf | hasSomeUnfolding unf_info = text "Unf=" <> ppr unf_info
               | otherwise                 = empty

    pprTypedLetBinder :: Var -> SDoc
    -- Print binder with a type or kind signature (not paren'd)
    pprTypedLetBinder binder
      = sdocWithDynFlags $ \dflags ->
        case () of
        _
          | isTyVar binder                         -> pprKindedTyVarBndr binder
          | gopt Opt_SuppressTypeSignatures dflags -> pprIdBndr binder
          | otherwise                              -> hang (pprIdBndr binder) 2 (dcolon <+> pprType (idType binder))

    pprKindedTyVarBndr :: TyVar -> SDoc
    -- Print a type variable binder with its kind (but not if *)
    pprKindedTyVarBndr tyvar
      = text "@" <+> pprTyVar tyvar

    -- pprIdBndr does *not* print the type
    -- When printing any Id binder in debug mode, we print its inline pragma and one-shot-ness
    pprIdBndr :: Id -> SDoc
    pprIdBndr id = ppr id <+> pprIdBndrInfo (idInfo id)

    pprIdBndrInfo :: IdInfo -> SDoc
    pprIdBndrInfo info
      = sdocWithDynFlags $ \dflags ->
        ppUnless (gopt Opt_SuppressIdInfo dflags) $
        info `seq` doc -- The seq is useful for poking on black holes
      where
        prag_info = inlinePragInfo info
        occ_info  = occInfo info
        dmd_info  = demandInfo info
        lbv_info  = oneShotInfo info

        has_prag  = not (isDefaultInlinePragma prag_info)
        has_occ   = not (isManyOccs occ_info)
        has_dmd   = not $ isTopDmd dmd_info
        has_lbv   = not (hasNoOneShotInfo lbv_info)

        doc = showAttributes
              [ (has_prag, text "InlPrag=" <> pprInlineDebug prag_info)
              , (has_occ,  text "Occ=" <> ppr occ_info)
              , (has_dmd,  text "Dmd=" <> ppr dmd_info)
              , (has_lbv , text "OS=" <> ppr lbv_info)
              ]

    {-
    -----------------------------------------------------
    --      IdDetails and IdInfo
    -----------------------------------------------------
    -}

    ppIdInfo :: Id -> IdInfo -> SDoc
    ppIdInfo id info
      = sdocWithDynFlags $ \dflags ->
        ppUnless (gopt Opt_SuppressIdInfo dflags) $
        showAttributes
        [ (True, pp_scope <> ppr (idDetails id))
        , (has_arity,        text "Arity=" <> int arity)
        , (has_called_arity, text "CallArity=" <> int called_arity)
        , (has_caf_info,     text "Caf=" <> ppr caf_info)
        , (has_str_info,     text "Str=" <> pprStrictness str_info)
        , (has_unf,          text "Unf=" <> ppr unf_info)
        , (not (null rules), text "RULES:" <+> vcat (map pprRule rules))
        ]   -- Inline pragma, occ, demand, one-shot info
            -- printed out with all binders (when debug is on);
            -- see PprCore.pprIdBndr
      where
        pp_scope | isGlobalId id   = text "GblId"
                 | isExportedId id = text "LclIdX"
                 | otherwise       = text "LclId"

        arity = arityInfo info
        has_arity = arity /= 0

        called_arity = callArityInfo info
        has_called_arity = called_arity /= 0

        caf_info = cafInfo info
        has_caf_info = not (mayHaveCafRefs caf_info)

        str_info = strictnessInfo info
        has_str_info = not (isTopSig str_info)

        unf_info = unfoldingInfo info
        has_unf = hasSomeUnfolding unf_info

        rules = ruleInfoRules (ruleInfo info)

    showAttributes :: [(Bool,SDoc)] -> SDoc
    showAttributes stuff
      | null docs = empty
      | otherwise = brackets (sep (punctuate comma docs))
      where
        docs = [d | (True,d) <- stuff]

    {-
    -----------------------------------------------------
    --      Unfolding and UnfoldingGuidance
    -----------------------------------------------------
    -}

    instance Outputable UnfoldingGuidance where
        ppr UnfNever  = text "NEVER"
        ppr (UnfWhen { ug_arity = arity, ug_unsat_ok = unsat_ok, ug_boring_ok = boring_ok })
          = text "ALWAYS_IF" <>
            parens (text "arity="     <> int arity    <> comma <>
                    text "unsat_ok="  <> ppr unsat_ok <> comma <>
                    text "boring_ok=" <> ppr boring_ok)
        ppr (UnfIfGoodArgs { ug_args = cs, ug_size = size, ug_res = discount })
          = hsep [ text "IF_ARGS",
                   brackets (hsep (map int cs)),
                   int size,
                   int discount ]

    instance Outputable UnfoldingSource where
      ppr InlineCompulsory  = text "Compulsory"
      ppr InlineStable      = text "InlineStable"
      ppr InlineRhs         = text "<vanilla>"

    instance Outputable Unfolding where
      ppr NoUnfolding                = text "No unfolding"
      ppr BootUnfolding              = text "No unfolding (from boot)"
      ppr (OtherCon cs)              = text "OtherCon" <+> ppr cs
      ppr (DFunUnfolding { df_bndrs = bndrs, df_con = con, df_args = args })
           = hang (text "DFun:" <+> ptext (sLit "\\")
                    <+> sep (map (pprBndr LambdaBind) bndrs) <+> arrow)
                2 (ppr con <+> sep (map ppr args))
      ppr (CoreUnfolding { uf_src = src
                         , uf_tmpl=rhs, uf_is_top=top, uf_is_value=hnf
                         , uf_is_conlike=conlike, uf_is_work_free=wf
                         , uf_expandable=exp, uf_guidance=g })
            = text "Unf" <> braces (pp_info $$ pp_rhs)
        where
          pp_info = fsep $ punctuate comma
                    [ text "Src="        <> ppr src
                    , text "TopLvl="     <> ppr top
                    , text "Value="      <> ppr hnf
                    , text "ConLike="    <> ppr conlike
                    , text "WorkFree="   <> ppr wf
                    , text "Expandable=" <> ppr exp
                    , text "Guidance="   <> ppr g ]
          pp_tmpl = sdocWithDynFlags $ \dflags ->
                    ppUnless (gopt Opt_SuppressUnfoldings dflags) $
                    text "Tmpl=" <+> ppr rhs
          pp_rhs | isStableSource src = pp_tmpl
                 | otherwise          = empty
                -- Don't print the RHS or we get a quadratic
                -- blowup in the size of the printout!

    {-
    -----------------------------------------------------
    --      Rules
    -----------------------------------------------------
    -}

    instance Outputable CoreRule where
       ppr = pprRule

    pprRules :: [CoreRule] -> SDoc
    pprRules rules = vcat (map pprRule rules)

    pprRule :: CoreRule -> SDoc
    pprRule (BuiltinRule { ru_fn = fn, ru_name = name})
      = text "Built in rule for" <+> ppr fn <> colon <+> doubleQuotes (ftext name)

    pprRule (Rule { ru_name = name, ru_act = act, ru_fn = fn,
                    ru_bndrs = tpl_vars, ru_args = tpl_args,
                    ru_rhs = rhs })
      = hang (doubleQuotes (ftext name) <+> ppr act)
           4 (sep [text "forall" <+>
                      sep (map (pprCoreBinder LambdaBind) tpl_vars) <> dot,
                   nest 2 (ppr fn <+> sep (map pprArg tpl_args)),
                   nest 2 (text "=" <+> pprCoreExpr rhs)
                ])

    {-
    -----------------------------------------------------
    --      Tickish
    -----------------------------------------------------
    -}

    instance Outputable id => Outputable (Tickish id) where
      ppr (HpcTick modl ix) =
          hcat [text "hpc<",
                ppr modl, comma,
                ppr ix,
                text ">"]
      ppr (Breakpoint ix vars) =
          hcat [text "break<",
                ppr ix,
                text ">",
                parens (hcat (punctuate comma (map ppr vars)))]
      ppr (ProfNote { profNoteCC = cc,
                      profNoteCount = tick,
                      profNoteScope = scope }) =
          case (tick,scope) of
             (True,True)  -> hcat [text "scctick<", ppr cc, char '>']
             (True,False) -> hcat [text "tick<",    ppr cc, char '>']
             _            -> hcat [text "scc<",     ppr cc, char '>']
      ppr (SourceNote span _) =
          hcat [ text "src<", pprUserRealSpan True span, char '>']