HsDecls.lhs 24.4 KB
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%
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% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
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%
\section[HsDecls]{Abstract syntax: global declarations}

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Definitions for: @TyDecl@ and @oCnDecl@, @ClassDecl@,
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@InstDecl@, @DefaultDecl@ and @ForeignDecl@.
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\begin{code}
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module HsDecls (
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	HsDecl(..), LHsDecl, TyClDecl(..), LTyClDecl, 
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	InstDecl(..), LInstDecl, NewOrData(..),
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	RuleDecl(..), LRuleDecl, RuleBndr(..),
	DefaultDecl(..), LDefaultDecl, HsGroup(..), SpliceDecl(..),
	ForeignDecl(..), LForeignDecl, ForeignImport(..), ForeignExport(..),
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	CImportSpec(..), FoType(..),
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	ConDecl(..), LConDecl,
	LBangType, BangType(..), HsBang(..), 
	getBangType, getBangStrictness, unbangedType, 
	DeprecDecl(..),  LDeprecDecl,
	tcdName, tyClDeclNames, tyClDeclTyVars,
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	isClassDecl, isSynDecl, isDataDecl, 
	countTyClDecls,
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	conDetailsTys,
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	collectRuleBndrSigTys, 
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    ) where
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#include "HsVersions.h"
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-- friends:
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import {-# SOURCE #-}	HsExpr( HsExpr, pprExpr )
	-- Because Expr imports Decls via HsBracket

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import HsBinds		( HsBindGroup, HsBind, LHsBinds, 
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			  Sig(..), LSig, LFixitySig, pprLHsBinds )
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import HsPat		( HsConDetails(..), hsConArgs )
import HsImpExp		( pprHsVar )
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import HsTypes
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import HscTypes		( DeprecTxt )
import CoreSyn		( RuleName )
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import BasicTypes	( Activation(..) )
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import ForeignCall	( CCallTarget(..), DNCallSpec, CCallConv, Safety,
			  CExportSpec(..)) 
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-- others:
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import FunDeps		( pprFundeps )
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import Class		( FunDep )
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import CStrings		( CLabelString )
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import Outputable	
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import Util		( count )
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import SrcLoc		( Located(..), unLoc )
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import FastString
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\end{code}

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%************************************************************************
%*									*
\subsection[HsDecl]{Declarations}
%*									*
%************************************************************************

\begin{code}
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type LHsDecl id = Located (HsDecl id)

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data HsDecl id
  = TyClD	(TyClDecl id)
  | InstD	(InstDecl  id)
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  | ValD	(HsBind id)
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  | SigD	(Sig id)
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  | DefD	(DefaultDecl id)
  | ForD        (ForeignDecl id)
  | DeprecD	(DeprecDecl id)
  | RuleD	(RuleDecl id)
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  | SpliceD	(SpliceDecl id)
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-- NB: all top-level fixity decls are contained EITHER
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-- EITHER SigDs
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-- OR     in the ClassDecls in TyClDs
--
-- The former covers
-- 	a) data constructors
-- 	b) class methods (but they can be also done in the
-- 		signatures of class decls)
--	c) imported functions (that have an IfacSig)
--	d) top level decls
--
-- The latter is for class methods only
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-- A [HsDecl] is categorised into a HsGroup before being 
-- fed to the renamer.
data HsGroup id
  = HsGroup {
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	hs_valds  :: [HsBindGroup id],
		-- Before the renamer, this is a single big HsBindGroup,
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		-- with all the bindings, and all the signatures.
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		-- The renamer does dependency analysis, splitting it up
		-- into several HsBindGroups.
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	hs_tyclds :: [LTyClDecl id],
	hs_instds :: [LInstDecl id],
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	hs_fixds  :: [LFixitySig id],
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		-- Snaffled out of both top-level fixity signatures,
		-- and those in class declarations

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	hs_defds  :: [LDefaultDecl id],
	hs_fords  :: [LForeignDecl id],
	hs_depds  :: [LDeprecDecl id],
	hs_ruleds :: [LRuleDecl id]
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  }
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\end{code}

\begin{code}
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instance OutputableBndr name => Outputable (HsDecl name) where
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    ppr (TyClD dcl)  = ppr dcl
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    ppr (ValD binds) = ppr binds
    ppr (DefD def)   = ppr def
    ppr (InstD inst) = ppr inst
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    ppr (ForD fd)    = ppr fd
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    ppr (SigD sd)    = ppr sd
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    ppr (RuleD rd)   = ppr rd
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    ppr (DeprecD dd) = ppr dd
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    ppr (SpliceD dd) = ppr dd
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instance OutputableBndr name => Outputable (HsGroup name) where
    ppr (HsGroup { hs_valds  = val_decls,
		   hs_tyclds = tycl_decls,
		   hs_instds = inst_decls,
		   hs_fixds  = fix_decls,
		   hs_depds  = deprec_decls,
		   hs_fords  = foreign_decls,
		   hs_defds  = default_decls,
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		   hs_ruleds = rule_decls })
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	= vcat [ppr_ds fix_decls, ppr_ds default_decls, 
		ppr_ds deprec_decls, ppr_ds rule_decls,
		ppr val_decls,
		ppr_ds tycl_decls, ppr_ds inst_decls,
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		ppr_ds foreign_decls]
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	where
	  ppr_ds [] = empty
	  ppr_ds ds = text "" $$ vcat (map ppr ds)
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data SpliceDecl id = SpliceDecl (Located (HsExpr id))	-- Top level splice
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instance OutputableBndr name => Outputable (SpliceDecl name) where
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   ppr (SpliceDecl e) = ptext SLIT("$") <> parens (pprExpr (unLoc e))
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\end{code}

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%************************************************************************
%*									*
\subsection[TyDecl]{@data@, @newtype@ or @type@ (synonym) type declaration}
%*									*
%************************************************************************

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		--------------------------------
			THE NAMING STORY
		--------------------------------
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Here is the story about the implicit names that go with type, class,
and instance decls.  It's a bit tricky, so pay attention!
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"Implicit" (or "system") binders
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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  Each data type decl defines 
	a worker name for each constructor
	to-T and from-T convertors
  Each class decl defines
	a tycon for the class
	a data constructor for that tycon
	the worker for that constructor
	a selector for each superclass

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All have occurrence names that are derived uniquely from their parent
declaration.
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None of these get separate definitions in an interface file; they are
fully defined by the data or class decl.  But they may *occur* in
interface files, of course.  Any such occurrence must haul in the
relevant type or class decl.

Plan of attack:
 - Ensure they "point to" the parent data/class decl 
   when loading that decl from an interface file
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   (See RnHiFiles.getSysBinders)

 - When typechecking the decl, we build the implicit TyCons and Ids.
   When doing so we look them up in the name cache (RnEnv.lookupSysName),
   to ensure correct module and provenance is set
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These are the two places that we have to conjure up the magic derived
names.  (The actual magic is in OccName.mkWorkerOcc, etc.)
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Default methods
~~~~~~~~~~~~~~~
 - Occurrence name is derived uniquely from the method name
   E.g. $dmmax

 - If there is a default method name at all, it's recorded in
   the ClassOpSig (in HsBinds), in the DefMeth field.
   (DefMeth is defined in Class.lhs)

Source-code class decls and interface-code class decls are treated subtly
differently, which has given me a great deal of confusion over the years.
Here's the deal.  (We distinguish the two cases because source-code decls
have (Just binds) in the tcdMeths field, whereas interface decls have Nothing.

In *source-code* class declarations:
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 - When parsing, every ClassOpSig gets a DefMeth with a suitable RdrName
   This is done by RdrHsSyn.mkClassOpSigDM

 - The renamer renames it to a Name

 - During typechecking, we generate a binding for each $dm for 
   which there's a programmer-supplied default method:
	class Foo a where
	  op1 :: <type>
	  op2 :: <type>
	  op1 = ...
   We generate a binding for $dmop1 but not for $dmop2.
   The Class for Foo has a NoDefMeth for op2 and a DefMeth for op1.
   The Name for $dmop2 is simply discarded.

In *interface-file* class declarations:
  - When parsing, we see if there's an explicit programmer-supplied default method
    because there's an '=' sign to indicate it:
	class Foo a where
	  op1 = :: <type>	-- NB the '='
  	  op2   :: <type>
    We use this info to generate a DefMeth with a suitable RdrName for op1,
    and a NoDefMeth for op2
  - The interface file has a separate definition for $dmop1, with unfolding etc.
  - The renamer renames it to a Name.
  - The renamer treats $dmop1 as a free variable of the declaration, so that
    the binding for $dmop1 will be sucked in.  (See RnHsSyn.tyClDeclFVs)  
    This doesn't happen for source code class decls, because they *bind* the default method.

Dictionary functions
~~~~~~~~~~~~~~~~~~~~
Each instance declaration gives rise to one dictionary function binding.

The type checker makes up new source-code instance declarations
(e.g. from 'deriving' or generic default methods --- see
TcInstDcls.tcInstDecls1).  So we can't generate the names for
dictionary functions in advance (we don't know how many we need).

On the other hand for interface-file instance declarations, the decl
specifies the name of the dictionary function, and it has a binding elsewhere
in the interface file:
	instance {Eq Int} = dEqInt
	dEqInt :: {Eq Int} <pragma info>

So again we treat source code and interface file code slightly differently.

Source code:
  - Source code instance decls have a Nothing in the (Maybe name) field
    (see data InstDecl below)

  - The typechecker makes up a Local name for the dict fun for any source-code
    instance decl, whether it comes from a source-code instance decl, or whether
    the instance decl is derived from some other construct (e.g. 'deriving').

  - The occurrence name it chooses is derived from the instance decl (just for 
    documentation really) --- e.g. dNumInt.  Two dict funs may share a common
    occurrence name, but will have different uniques.  E.g.
	instance Foo [Int]  where ...
	instance Foo [Bool] where ...
    These might both be dFooList

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  - The CoreTidy phase externalises the name, and ensures the occurrence name is
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    unique (this isn't special to dict funs).  So we'd get dFooList and dFooList1.

  - We can take this relaxed approach (changing the occurrence name later) 
    because dict fun Ids are not captured in a TyCon or Class (unlike default
    methods, say).  Instead, they are kept separately in the InstEnv.  This
    makes it easy to adjust them after compiling a module.  (Once we've finished
    compiling that module, they don't change any more.)


Interface file code:
  - The instance decl gives the dict fun name, so the InstDecl has a (Just name)
    in the (Maybe name) field.
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  - RnHsSyn.instDeclFVs treats the dict fun name as free in the decl, so that we
    suck in the dfun binding
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\begin{code}
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-- TyClDecls are precisely the kind of declarations that can 
-- appear in interface files; or (internally) in GHC's interface
-- for a module.  That's why (despite the misnomer) IfaceSig and ForeignType
-- are both in TyClDecl

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type LTyClDecl name = Located (TyClDecl name)

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data TyClDecl name
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  = ForeignType { 
		tcdLName    :: Located name,
		tcdExtName  :: Maybe FastString,
		tcdFoType   :: FoType
  }
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  | TyData {	tcdND     :: NewOrData,
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		tcdCtxt   :: LHsContext name,	 	-- Context
		tcdLName  :: Located name,	 	-- Type constructor
		tcdTyVars :: [LHsTyVarBndr name], 	-- Type variables
		tcdCons	  :: [LConDecl name],	 	-- Data constructors
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		tcdDerivs :: Maybe [LHsType name]
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			-- Derivings; Nothing => not specified
			-- 	      Just [] => derive exactly what is asked
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			-- These "types" must be of form
			--	forall ab. C ty1 ty2
			-- Typically the foralls and ty args are empty, but they
			-- are non-empty for the newtype-deriving case
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    }

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  | TySynonym {	tcdLName  :: Located name,	        -- type constructor
		tcdTyVars :: [LHsTyVarBndr name],	-- type variables
		tcdSynRhs :: LHsType name	        -- synonym expansion
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    }

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  | ClassDecl {	tcdCtxt    :: LHsContext name, 	 	-- Context...
		tcdLName   :: Located name,	    	-- Name of the class
		tcdTyVars  :: [LHsTyVarBndr name],	-- Class type variables
		tcdFDs     :: [Located (FunDep name)],	-- Functional deps
		tcdSigs    :: [LSig name],		-- Methods' signatures
		tcdMeths   :: LHsBinds name		-- Default methods
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    }
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data NewOrData
  = NewType  	-- "newtype Blah ..."
  | DataType 	-- "data Blah ..."
  deriving( Eq )	-- Needed because Demand derives Eq
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\end{code}

Simple classifiers

\begin{code}
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isDataDecl, isSynDecl, isClassDecl :: TyClDecl name -> Bool
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isSynDecl (TySynonym {}) = True
isSynDecl other		 = False
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isDataDecl (TyData {}) = True
isDataDecl other       = False
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isClassDecl (ClassDecl {}) = True
isClassDecl other	   = False
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\end{code}

Dealing with names
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\begin{code}
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tcdName :: TyClDecl name -> name
tcdName decl = unLoc (tcdLName decl)
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tyClDeclNames :: Eq name => TyClDecl name -> [Located name]
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-- Returns all the *binding* names of the decl, along with their SrcLocs
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-- The first one is guaranteed to be the name of the decl
-- For record fields, the first one counts as the SrcLoc
-- We use the equality to filter out duplicate field names

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tyClDeclNames (TySynonym   {tcdLName = name})  = [name]
tyClDeclNames (ForeignType {tcdLName = name})  = [name]
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tyClDeclNames (ClassDecl {tcdLName = cls_name, tcdSigs = sigs})
  = cls_name : [n | L _ (Sig n _) <- sigs]
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tyClDeclNames (TyData {tcdLName = tc_name, tcdCons = cons})
  = tc_name : conDeclsNames (map unLoc cons)
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tyClDeclTyVars (TySynonym {tcdTyVars = tvs}) = tvs
tyClDeclTyVars (TyData    {tcdTyVars = tvs}) = tvs
tyClDeclTyVars (ClassDecl {tcdTyVars = tvs}) = tvs
tyClDeclTyVars (ForeignType {})		     = []
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\end{code}

\begin{code}
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countTyClDecls :: [TyClDecl name] -> (Int, Int, Int, Int)
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	-- class, data, newtype, synonym decls
countTyClDecls decls 
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 = (count isClassDecl     decls,
    count isSynDecl       decls,
    count isDataTy        decls,
    count isNewTy         decls) 
 where
   isDataTy TyData{tcdND=DataType} = True
   isDataTy _                      = False
   
   isNewTy TyData{tcdND=NewType} = True
   isNewTy _                     = False
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\end{code}

\begin{code}
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instance OutputableBndr name
	      => Outputable (TyClDecl name) where
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    ppr (ForeignType {tcdLName = ltycon})
	= hsep [ptext SLIT("foreign import type dotnet"), ppr ltycon]
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    ppr (TySynonym {tcdLName = ltycon, tcdTyVars = tyvars, tcdSynRhs = mono_ty})
      = hang (ptext SLIT("type") <+> pp_decl_head [] ltycon tyvars <+> equals)
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	     4 (ppr mono_ty)
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    ppr (TyData {tcdND = new_or_data, tcdCtxt = context, tcdLName = ltycon,
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		 tcdTyVars = tyvars, tcdCons = condecls, 
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		 tcdDerivs = derivings})
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      = pp_tydecl (ppr new_or_data <+> pp_decl_head (unLoc context) ltycon tyvars)
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		  (pp_condecls condecls)
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		  derivings

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    ppr (ClassDecl {tcdCtxt = context, tcdLName = lclas, tcdTyVars = tyvars, tcdFDs = fds,
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		    tcdSigs = sigs, tcdMeths = methods})
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      | null sigs	-- No "where" part
      = top_matter

      | otherwise	-- Laid out
      = sep [hsep [top_matter, ptext SLIT("where {")],
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	     nest 4 (sep [sep (map ppr_sig sigs), ppr methods, char '}'])]
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      where
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        top_matter  = ptext SLIT("class") <+> pp_decl_head (unLoc context) lclas tyvars <+> pprFundeps (map unLoc fds)
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	ppr_sig sig = ppr sig <> semi
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pp_decl_head :: OutputableBndr name
   => HsContext name
   -> Located name
   -> [LHsTyVarBndr name]
   -> SDoc
pp_decl_head context thing tyvars
  = hsep [pprHsContext context, ppr thing, interppSP tyvars]
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pp_condecls cs = equals <+> sep (punctuate (ptext SLIT(" |")) (map ppr cs))
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pp_tydecl pp_head pp_decl_rhs derivings
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  = hang pp_head 4 (sep [
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	pp_decl_rhs,
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	case derivings of
	  Nothing 	   -> empty
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	  Just ds	   -> hsep [ptext SLIT("deriving"), parens (interpp'SP ds)]
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    ])
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instance Outputable NewOrData where
  ppr NewType  = ptext SLIT("newtype")
  ppr DataType = ptext SLIT("data")
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\end{code}


%************************************************************************
%*									*
\subsection[ConDecl]{A data-constructor declaration}
%*									*
%************************************************************************

\begin{code}
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type LConDecl name = Located (ConDecl name)

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data ConDecl name
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  = ConDecl 	(Located name)		-- Constructor name; this is used for the
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					-- DataCon itself, and for the user-callable wrapper Id

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		[LHsTyVarBndr name]	-- Existentially quantified type variables
		(LHsContext name)	-- ...and context
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					-- If both are empty then there are no existentials

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		(HsConDetails name (LBangType name))
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\end{code}

\begin{code}
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conDeclsNames :: Eq name => [ConDecl name] -> [Located name]
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  -- See tyClDeclNames for what this does
  -- The function is boringly complicated because of the records
  -- And since we only have equality, we have to be a little careful
conDeclsNames cons
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  = snd (foldl do_one ([], []) cons)
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  where
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    do_one (flds_seen, acc) (ConDecl lname _ _ (RecCon flds))
	= (map unLoc new_flds ++ flds_seen, lname : [f | f <- new_flds] ++ acc)
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	where
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	  new_flds = [ f | (f,_) <- flds, not (unLoc f `elem` flds_seen) ]
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    do_one (flds_seen, acc) (ConDecl lname _ _ _)
	= (flds_seen, lname:acc)
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conDetailsTys details = map getBangType (hsConArgs details)
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\end{code}
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\begin{code}
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type LBangType name = Located (BangType name)

data BangType name = BangType HsBang (LHsType name)
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data HsBang = HsNoBang
	    | HsStrict	-- ! 
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	    | HsUnbox	-- {-# UNPACK #-} ! (GHC extension, meaning "unbox")
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getBangType       (BangType _ ty) = ty
getBangStrictness (BangType s _)  = s

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unbangedType :: LHsType id -> LBangType id
unbangedType ty@(L loc _) = L loc (BangType HsNoBang ty)
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\end{code}

\begin{code}
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instance (OutputableBndr name) => Outputable (ConDecl name) where
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    ppr (ConDecl con tvs cxt con_details)
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      = sep [pprHsForAll Explicit tvs cxt, ppr_con_details con con_details]
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ppr_con_details con (InfixCon ty1 ty2)
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  = hsep [ppr ty1, ppr con, ppr ty2]
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-- ConDecls generated by MkIface.ifaceTyThing always have a PrefixCon, even
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-- if the constructor is an infix one.  This is because in an interface file
-- we don't distinguish between the two.  Hence when printing these for the
-- user, we need to parenthesise infix constructor names.
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ppr_con_details con (PrefixCon tys)
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  = hsep (pprHsVar con : map ppr tys)
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ppr_con_details con (RecCon fields)
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  = ppr con <+> braces (sep (punctuate comma (map ppr_field fields)))
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  where
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    ppr_field (n, ty) = ppr n <+> dcolon <+> ppr ty
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instance OutputableBndr name => Outputable (BangType name) where
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    ppr (BangType is_strict ty) 
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	= bang <> pprParendHsType (unLoc ty)
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	where
	  bang = case is_strict of
			HsNoBang -> empty
			HsStrict -> char '!'
			HsUnbox  -> ptext SLIT("!!")
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\end{code}


%************************************************************************
%*									*
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\subsection[InstDecl]{An instance declaration
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%*									*
%************************************************************************

\begin{code}
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type LInstDecl name = Located (InstDecl name)

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data InstDecl name
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  = InstDecl	(LHsType name)	-- Context => Class Instance-type
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				-- Using a polytype means that the renamer conveniently
				-- figures out the quantified type variables for us.
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		(LHsBinds name)
		[LSig name]		-- User-supplied pragmatic info
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instance (OutputableBndr name) => Outputable (InstDecl name) where
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    ppr (InstDecl inst_ty binds uprags)
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      = vcat [hsep [ptext SLIT("instance"), ppr inst_ty, ptext SLIT("where")],
	      nest 4 (ppr uprags),
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	      nest 4 (pprLHsBinds binds) ]
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\end{code}

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%************************************************************************
%*									*
\subsection[DefaultDecl]{A @default@ declaration}
%*									*
%************************************************************************

There can only be one default declaration per module, but it is hard
for the parser to check that; we pass them all through in the abstract
syntax, and that restriction must be checked in the front end.

\begin{code}
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type LDefaultDecl name = Located (DefaultDecl name)

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data DefaultDecl name
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  = DefaultDecl	[LHsType name]
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instance (OutputableBndr name)
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	      => Outputable (DefaultDecl name) where

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    ppr (DefaultDecl tys)
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      = ptext SLIT("default") <+> parens (interpp'SP tys)
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\end{code}
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%************************************************************************
%*									*
\subsection{Foreign function interface declaration}
%*									*
%************************************************************************

\begin{code}
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-- foreign declarations are distinguished as to whether they define or use a
-- Haskell name
--
-- * the Boolean value indicates whether the pre-standard deprecated syntax
--   has been used
--
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type LForeignDecl name = Located (ForeignDecl name)

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data ForeignDecl name
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  = ForeignImport (Located name) (LHsType name) ForeignImport Bool  -- defines name
  | ForeignExport (Located name) (LHsType name) ForeignExport Bool  -- uses name
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-- specification of an imported external entity in dependence on the calling
-- convention 
--
data ForeignImport = -- import of a C entity
		     --
                     -- * the two strings specifying a header file or library
                     --   may be empty, which indicates the absence of a
                     --   header or object specification (both are not used
                     --   in the case of `CWrapper' and when `CFunction'
                     --   has a dynamic target)
		     --
		     -- * the calling convention is irrelevant for code
		     --   generation in the case of `CLabel', but is needed
		     --   for pretty printing 
		     --
		     -- * `Safety' is irrelevant for `CLabel' and `CWrapper'
		     --
		     CImport  CCallConv	      -- ccall or stdcall
			      Safety	      -- safe or unsafe
			      FastString      -- name of C header
			      FastString      -- name of library object
			      CImportSpec     -- details of the C entity

                     -- import of a .NET function
		     --
		   | DNImport DNCallSpec

-- details of an external C entity
--
data CImportSpec = CLabel    CLabelString     -- import address of a C label
		 | CFunction CCallTarget      -- static or dynamic function
		 | CWrapper		      -- wrapper to expose closures
					      -- (former f.e.d.)
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-- specification of an externally exported entity in dependence on the calling
-- convention
--
data ForeignExport = CExport  CExportSpec    -- contains the calling convention
		   | DNExport		     -- presently unused
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-- abstract type imported from .NET
--
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data FoType = DNType 		-- In due course we'll add subtype stuff
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	    deriving (Eq)	-- Used for equality instance for TyClDecl


-- pretty printing of foreign declarations
--
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instance OutputableBndr name => Outputable (ForeignDecl name) where
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  ppr (ForeignImport n ty fimport _) =
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    ptext SLIT("foreign import") <+> ppr fimport <+> 
    ppr n <+> dcolon <+> ppr ty
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  ppr (ForeignExport n ty fexport _) =
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    ptext SLIT("foreign export") <+> ppr fexport <+> 
    ppr n <+> dcolon <+> ppr ty

instance Outputable ForeignImport where
  ppr (DNImport			        spec) = 
    ptext SLIT("dotnet") <+> ppr spec
  ppr (CImport  cconv safety header lib spec) =
    ppr cconv <+> ppr safety <+> 
    char '"' <> pprCEntity header lib spec <> char '"'
    where
      pprCEntity header lib (CLabel lbl) = 
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        ptext SLIT("static") <+> ftext header <+> char '&' <>
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	pprLib lib <> ppr lbl
      pprCEntity header lib (CFunction (StaticTarget lbl)) = 
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        ptext SLIT("static") <+> ftext header <+> char '&' <>
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	pprLib lib <> ppr lbl
      pprCEntity header lib (CFunction (DynamicTarget)) = 
        ptext SLIT("dynamic")
      pprCEntity _      _   (CWrapper) = ptext SLIT("wrapper")
      --
      pprLib lib | nullFastString lib = empty
		 | otherwise	      = char '[' <> ppr lib <> char ']'

instance Outputable ForeignExport where
  ppr (CExport  (CExportStatic lbl cconv)) = 
    ppr cconv <+> char '"' <> ppr lbl <> char '"'
  ppr (DNExport                          ) = 
    ptext SLIT("dotnet") <+> ptext SLIT("\"<unused>\"")
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instance Outputable FoType where
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  ppr DNType = ptext SLIT("type dotnet")
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\end{code}

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%************************************************************************
%*									*
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\subsection{Transformation rules}
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%*									*
%************************************************************************

\begin{code}
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type LRuleDecl name = Located (RuleDecl name)

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data RuleDecl name
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  = HsRule			-- Source rule
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	RuleName		-- Rule name
	Activation
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	[RuleBndr name]		-- Forall'd vars; after typechecking this includes tyvars
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	(Located (HsExpr name))	-- LHS
	(Located (HsExpr name))	-- RHS
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data RuleBndr name
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  = RuleBndr (Located name)
  | RuleBndrSig (Located name) (LHsType name)
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collectRuleBndrSigTys :: [RuleBndr name] -> [LHsType name]
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collectRuleBndrSigTys bndrs = [ty | RuleBndrSig _ ty <- bndrs]

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instance OutputableBndr name => Outputable (RuleDecl name) where
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  ppr (HsRule name act ns lhs rhs)
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	= sep [text "{-# RULES" <+> doubleQuotes (ftext name) <+> ppr act,
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	       nest 4 (pp_forall <+> pprExpr (unLoc lhs)), 
	       nest 4 (equals <+> pprExpr (unLoc rhs) <+> text "#-}") ]
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	where
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	  pp_forall | null ns   = empty
		    | otherwise	= text "forall" <+> fsep (map ppr ns) <> dot
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instance OutputableBndr name => Outputable (RuleBndr name) where
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   ppr (RuleBndr name) = ppr name
   ppr (RuleBndrSig name ty) = ppr name <> dcolon <> ppr ty
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\end{code}


%************************************************************************
%*									*
\subsection[DeprecDecl]{Deprecations}
%*									*
%************************************************************************

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We use exported entities for things to deprecate.
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\begin{code}
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type LDeprecDecl name = Located (DeprecDecl name)

data DeprecDecl name = Deprecation name DeprecTxt
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instance OutputableBndr name => Outputable (DeprecDecl name) where
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    ppr (Deprecation thing txt)
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      = hsep [text "{-# DEPRECATED", ppr thing, doubleQuotes (ppr txt), text "#-}"]
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\end{code}