-----------------------------------------------------------------------------
--
-- Pretty-printing TyThings
--
-- (c) The GHC Team 2005
--
-----------------------------------------------------------------------------

{-# LANGUAGE CPP #-}
module PprTyThing (
        pprTyThing,
        pprTyThingInContext,
        pprTyThingLoc,
        pprTyThingInContextLoc,
        pprTyThingHdr,
        pprTypeForUser,
        pprFamInst
  ) where

#include "HsVersions.h"

import GhcPrelude

import Type    ( Type, ArgFlag(..), TyThing(..), mkTyVarBinders, tidyOpenType )
import IfaceSyn ( ShowSub(..), ShowHowMuch(..), AltPpr(..)
  , showToHeader, pprIfaceDecl )
import CoAxiom ( coAxiomTyCon )
import HscTypes( tyThingParent_maybe )
import MkIface ( tyThingToIfaceDecl )
import FamInstEnv( FamInst(..), FamFlavor(..) )
import TyCoPpr ( pprUserForAll, pprTypeApp, pprSigmaType )
import Name
import VarEnv( emptyTidyEnv )
import Outputable

-- -----------------------------------------------------------------------------
-- Pretty-printing entities that we get from the GHC API

{- Note [Pretty printing via IfaceSyn]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Our general plan for prett-printing
  - Types
  - TyCons
  - Classes
  - Pattern synonyms
  ...etc...

is to convert them to IfaceSyn, and pretty-print that. For example
  - pprType converts a Type to an IfaceType, and pretty prints that.
  - pprTyThing converts the TyThing to an IfaceDecl,
    and pretty prints that.

So IfaceSyn play a dual role:
  - it's the internal version of an interface files
  - it's used for pretty-printing

Why do this?

* A significant reason is that we need to be able
  to pretty-print IfaceSyn (to display Foo.hi), and it was a
  pain to duplicate masses of pretty-printing goop, esp for
  Type and IfaceType.

* When pretty-printing (a type, say), we want to tidy (with
  tidyType) to avoids having (forall a a. blah) where the two
  a's have different uniques.

  Alas, for type constructors, TyCon, tidying does not work well,
  because a TyCon includes DataCons which include Types, which mention
  TyCons. And tidying can't tidy a mutually recursive data structure
  graph, only trees.

* Interface files contains fast-strings, not uniques, so the very same
  tidying must take place when we convert to IfaceDecl. E.g.
  MkIface.tyThingToIfaceDecl which converts a TyThing (i.e. TyCon,
  Class etc) to an IfaceDecl.

  Bottom line: IfaceDecls are already 'tidy', so it's straightforward
  to print them.

* An alternative I once explored was to ensure that TyCons get type
  variables with distinct print-names. That's ok for type variables
  but less easy for kind variables. Processing data type declarations
  is already so complicated that I don't think it's sensible to add
  the extra requirement that it generates only "pretty" types and
  kinds.

Consequences:

- IfaceSyn (and IfaceType) must contain enough information to
  print nicely.  Hence, for example, the IfaceAppArgs type, which
  allows us to suppress invisible kind arguments in types
  (see Note [Suppressing invisible arguments] in IfaceType)

- In a few places we have info that is used only for pretty-printing,
  and is totally ignored when turning IfaceSyn back into TyCons
  etc (in TcIface). For example, IfaceClosedSynFamilyTyCon
  stores a [IfaceAxBranch] that is used only for pretty-printing.

- See Note [Free tyvars in IfaceType] in IfaceType

See #7730, #8776 for details   -}

--------------------
-- | Pretty-prints a 'FamInst' (type/data family instance) with its defining location.
pprFamInst :: FamInst -> SDoc
--  * For data instances we go via pprTyThing of the representational TyCon,
--    because there is already much cleverness associated with printing
--    data type declarations that I don't want to duplicate
--  * For type instances we print directly here; there is no TyCon
--    to give to pprTyThing
--
-- FamInstEnv.pprFamInst does a more quick-and-dirty job for internal purposes

pprFamInst :: FamInst -> SDoc
pprFamInst (FamInst { fi_flavor :: FamInst -> FamFlavor
fi_flavor = DataFamilyInst TyCon
rep_tc })
  = TyThing -> SDoc
pprTyThingInContextLoc (TyCon -> TyThing
ATyCon TyCon
rep_tc)

pprFamInst (FamInst { fi_flavor :: FamInst -> FamFlavor
fi_flavor = FamFlavor
SynFamilyInst, fi_axiom :: FamInst -> CoAxiom Unbranched
fi_axiom = CoAxiom Unbranched
axiom
                    , fi_tvs :: FamInst -> [TyVar]
fi_tvs = [TyVar]
tvs, fi_tys :: FamInst -> [Type]
fi_tys = [Type]
lhs_tys, fi_rhs :: FamInst -> Type
fi_rhs = Type
rhs })
  = SDoc -> SDoc -> SDoc
showWithLoc (Name -> SDoc
pprDefinedAt (CoAxiom Unbranched -> Name
forall a. NamedThing a => a -> Name
getName CoAxiom Unbranched
axiom)) (SDoc -> SDoc) -> SDoc -> SDoc
forall a b. (a -> b) -> a -> b
$
    SDoc -> Int -> SDoc -> SDoc
hang (String -> SDoc
text String
"type instance"
            SDoc -> SDoc -> SDoc
<+> [TyCoVarBinder] -> SDoc
pprUserForAll (ArgFlag -> [TyVar] -> [TyCoVarBinder]
mkTyVarBinders ArgFlag
Specified [TyVar]
tvs)
                -- See Note [Printing foralls in type family instances]
                -- in IfaceType
            SDoc -> SDoc -> SDoc
<+> TyCon -> [Type] -> SDoc
pprTypeApp (CoAxiom Unbranched -> TyCon
forall (br :: BranchFlag). CoAxiom br -> TyCon
coAxiomTyCon CoAxiom Unbranched
axiom) [Type]
lhs_tys)
       Int
2 (SDoc
equals SDoc -> SDoc -> SDoc
<+> Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr Type
rhs)

----------------------------
-- | Pretty-prints a 'TyThing' with its defining location.
pprTyThingLoc :: TyThing -> SDoc
pprTyThingLoc :: TyThing -> SDoc
pprTyThingLoc TyThing
tyThing
  = SDoc -> SDoc -> SDoc
showWithLoc (Name -> SDoc
pprDefinedAt (TyThing -> Name
forall a. NamedThing a => a -> Name
getName TyThing
tyThing))
                (ShowSub -> TyThing -> SDoc
pprTyThing ShowSub
showToHeader TyThing
tyThing)

-- | Pretty-prints the 'TyThing' header. For functions and data constructors
-- the function is equivalent to 'pprTyThing' but for type constructors
-- and classes it prints only the header part of the declaration.
pprTyThingHdr :: TyThing -> SDoc
pprTyThingHdr :: TyThing -> SDoc
pprTyThingHdr = ShowSub -> TyThing -> SDoc
pprTyThing ShowSub
showToHeader

-- | Pretty-prints a 'TyThing' in context: that is, if the entity
-- is a data constructor, record selector, or class method, then
-- the entity's parent declaration is pretty-printed with irrelevant
-- parts omitted.
pprTyThingInContext :: ShowSub -> TyThing -> SDoc
pprTyThingInContext :: ShowSub -> TyThing -> SDoc
pprTyThingInContext ShowSub
show_sub TyThing
thing
  = [OccName] -> TyThing -> SDoc
go [] TyThing
thing
  where
    go :: [OccName] -> TyThing -> SDoc
go [OccName]
ss TyThing
thing
      = case TyThing -> Maybe TyThing
tyThingParent_maybe TyThing
thing of
          Just TyThing
parent ->
            [OccName] -> TyThing -> SDoc
go (TyThing -> OccName
forall a. NamedThing a => a -> OccName
getOccName TyThing
thing OccName -> [OccName] -> [OccName]
forall a. a -> [a] -> [a]
: [OccName]
ss) TyThing
parent
          Maybe TyThing
Nothing ->
            ShowSub -> TyThing -> SDoc
pprTyThing
              (ShowSub
show_sub { ss_how_much :: ShowHowMuch
ss_how_much = [OccName] -> AltPpr -> ShowHowMuch
ShowSome [OccName]
ss (Maybe (OccName -> SDoc) -> AltPpr
AltPpr Maybe (OccName -> SDoc)
forall a. Maybe a
Nothing) })
              TyThing
thing

-- | Like 'pprTyThingInContext', but adds the defining location.
pprTyThingInContextLoc :: TyThing -> SDoc
pprTyThingInContextLoc :: TyThing -> SDoc
pprTyThingInContextLoc TyThing
tyThing
  = SDoc -> SDoc -> SDoc
showWithLoc (Name -> SDoc
pprDefinedAt (TyThing -> Name
forall a. NamedThing a => a -> Name
getName TyThing
tyThing))
                (ShowSub -> TyThing -> SDoc
pprTyThingInContext ShowSub
showToHeader TyThing
tyThing)

-- | Pretty-prints a 'TyThing'.
pprTyThing :: ShowSub -> TyThing -> SDoc
-- We pretty-print 'TyThing' via 'IfaceDecl'
-- See Note [Pretty-printing TyThings]
pprTyThing :: ShowSub -> TyThing -> SDoc
pprTyThing ShowSub
ss TyThing
ty_thing
  = ShowSub -> IfaceDecl -> SDoc
pprIfaceDecl ShowSub
ss' (TyThing -> IfaceDecl
tyThingToIfaceDecl TyThing
ty_thing)
  where
    ss' :: ShowSub
ss' = case ShowSub -> ShowHowMuch
ss_how_much ShowSub
ss of
      ShowHeader (AltPpr Maybe (OccName -> SDoc)
Nothing)  -> ShowSub
ss { ss_how_much :: ShowHowMuch
ss_how_much = AltPpr -> ShowHowMuch
ShowHeader AltPpr
ppr' }
      ShowSome [OccName]
xs (AltPpr Maybe (OccName -> SDoc)
Nothing) -> ShowSub
ss { ss_how_much :: ShowHowMuch
ss_how_much = [OccName] -> AltPpr -> ShowHowMuch
ShowSome [OccName]
xs AltPpr
ppr' }
      ShowHowMuch
_                   -> ShowSub
ss

    ppr' :: AltPpr
ppr' = Maybe (OccName -> SDoc) -> AltPpr
AltPpr (Maybe (OccName -> SDoc) -> AltPpr)
-> Maybe (OccName -> SDoc) -> AltPpr
forall a b. (a -> b) -> a -> b
$ Name -> Maybe (OccName -> SDoc)
ppr_bndr (Name -> Maybe (OccName -> SDoc))
-> Name -> Maybe (OccName -> SDoc)
forall a b. (a -> b) -> a -> b
$ TyThing -> Name
forall a. NamedThing a => a -> Name
getName TyThing
ty_thing

    ppr_bndr :: Name -> Maybe (OccName -> SDoc)
    ppr_bndr :: Name -> Maybe (OccName -> SDoc)
ppr_bndr Name
name
      | Name -> Bool
isBuiltInSyntax Name
name
         = Maybe (OccName -> SDoc)
forall a. Maybe a
Nothing
      | Bool
otherwise
         = case Name -> Maybe Module
nameModule_maybe Name
name of
             Just Module
mod -> (OccName -> SDoc) -> Maybe (OccName -> SDoc)
forall a. a -> Maybe a
Just ((OccName -> SDoc) -> Maybe (OccName -> SDoc))
-> (OccName -> SDoc) -> Maybe (OccName -> SDoc)
forall a b. (a -> b) -> a -> b
$ \OccName
occ -> (PprStyle -> SDoc) -> SDoc
getPprStyle ((PprStyle -> SDoc) -> SDoc) -> (PprStyle -> SDoc) -> SDoc
forall a b. (a -> b) -> a -> b
$ \PprStyle
sty ->
               PprStyle -> Module -> OccName -> SDoc
pprModulePrefix PprStyle
sty Module
mod OccName
occ SDoc -> SDoc -> SDoc
<> OccName -> SDoc
forall a. Outputable a => a -> SDoc
ppr OccName
occ
             Maybe Module
Nothing  -> WARN( True, ppr name ) Nothing
             -- Nothing is unexpected here; TyThings have External names

pprTypeForUser :: Type -> SDoc
-- The type is tidied
pprTypeForUser :: Type -> SDoc
pprTypeForUser Type
ty
  = Type -> SDoc
pprSigmaType Type
tidy_ty
  where
    (TidyEnv
_, Type
tidy_ty)     = TidyEnv -> Type -> (TidyEnv, Type)
tidyOpenType TidyEnv
emptyTidyEnv Type
ty
     -- Often the types/kinds we print in ghci are fully generalised
     -- and have no free variables, but it turns out that we sometimes
     -- print un-generalised kinds (eg when doing :k T), so it's
     -- better to use tidyOpenType here

showWithLoc :: SDoc -> SDoc -> SDoc
showWithLoc :: SDoc -> SDoc -> SDoc
showWithLoc SDoc
loc SDoc
doc
    = SDoc -> Int -> SDoc -> SDoc
hang SDoc
doc Int
2 (Char -> SDoc
char Char
'\t' SDoc -> SDoc -> SDoc
<> SDoc
comment SDoc -> SDoc -> SDoc
<+> SDoc
loc)
                -- The tab tries to make them line up a bit
  where
    comment :: SDoc
comment = String -> SDoc
text String
"--"