HsDecls.lhs 30.6 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(..), TyClDecl(..), InstDecl(..), RuleDecl(..), RuleBndr(..),
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	DefaultDecl(..), HsGroup(..),
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	ForeignDecl(..), ForeignImport(..), ForeignExport(..),
	CImportSpec(..), FoType(..),
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	ConDecl(..), CoreDecl(..),
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	BangType(..), getBangType, getBangStrictness, unbangedType,
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	DeprecDecl(..), DeprecTxt,
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	tyClDeclName, tyClDeclNames, tyClDeclTyVars,
	isClassDecl, isSynDecl, isDataDecl, isIfaceSigDecl, 
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	isTypeOrClassDecl, countTyClDecls,
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	isSourceInstDecl, ifaceRuleDeclName,
	conDetailsTys,
	collectRuleBndrSigTys, isSrcRule
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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

import HsBinds		( HsBinds, MonoBinds, Sig(..) )
import HsPat		( HsConDetails(..), hsConArgs )
import HsImpExp		( pprHsVar )
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import HsTypes
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import PprCore		( pprCoreRule )
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import HsCore		( UfExpr, UfBinder, HsIdInfo, pprHsIdInfo,
			  eq_ufBinders, eq_ufExpr, pprUfExpr 
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			)
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import CoreSyn		( CoreRule(..), RuleName )
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import BasicTypes	( NewOrData(..), StrictnessMark(..), Activation(..), FixitySig(..) )
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import ForeignCall	( CCallTarget(..), DNCallSpec, CCallConv, Safety,
			  CExportSpec(..)) 
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-- others:
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import Name		( NamedThing )
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import FunDeps		( pprFundeps )
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import TyCon		( DataConDetails(..), visibleDataCons )
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import Class		( FunDep, DefMeth(..) )
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import CStrings		( CLabelString )
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import Outputable	
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import Util		( eqListBy, count )
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import SrcLoc		( SrcLoc )
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import FastString
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import Maybe		( isNothing, fromJust )	
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\end{code}

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

\begin{code}
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data HsDecl id
  = TyClD	(TyClDecl id)
  | InstD	(InstDecl  id)
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  | ValD	(MonoBinds id)
  | SigD	(Sig id)
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  | DefD	(DefaultDecl id)
  | ForD        (ForeignDecl id)
  | DeprecD	(DeprecDecl id)
  | RuleD	(RuleDecl id)
  | CoreD	(CoreDecl id)
  | SpliceD	(HsExpr id)	-- Top level splice
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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 {
	hs_valds  :: HsBinds id,	
		-- Before the renamer, this is a single big MonoBinds, 
		-- with all the bindings, and all the signatures.
		-- The renamer does dependency analysis, using ThenBinds
		-- to give the structure

	hs_tyclds :: [TyClDecl id],
	hs_instds :: [InstDecl id],

	hs_fixds  :: [FixitySig id],
		-- Snaffled out of both top-level fixity signatures,
		-- and those in class declarations

	hs_defds  :: [DefaultDecl id],
	hs_fords  :: [ForeignDecl id],
	hs_depds  :: [DeprecDecl id],
	hs_ruleds :: [RuleDecl id],
	hs_coreds :: [CoreDecl id]
  }
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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 (CoreD dd)   = ppr dd
    ppr (SpliceD e)  = ptext SLIT("splice") <> parens (pprExpr e)
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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,
		   hs_ruleds = rule_decls,
		   hs_coreds = core_decls })
	= 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,
		ppr_ds foreign_decls, ppr_ds core_decls]
	where
	  ppr_ds [] = empty
	  ppr_ds ds = text "" $$ vcat (map ppr ds)
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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!

"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

All have occurrence names that are derived uniquely from their parent declaration.

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:
 - 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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data TyClDecl name
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  = IfaceSig {	tcdName :: name,		-- It may seem odd to classify an interface-file signature
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		tcdType :: HsType name,		-- as a 'TyClDecl', but it's very convenient.  
		tcdIdInfo :: [HsIdInfo name],
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		tcdLoc :: SrcLoc
    }

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  | ForeignType { tcdName    :: name,		-- See remarks about IfaceSig above
		  tcdExtName :: Maybe FastString,
		  tcdFoType  :: FoType,
		  tcdLoc     :: SrcLoc }
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  | TyData {	tcdND     :: NewOrData,
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		tcdCtxt   :: HsContext name,	 -- Context
		tcdName   :: name,		 -- Type constructor
		tcdTyVars :: [HsTyVarBndr name], -- Type variables
		tcdCons	  :: DataConDetails (ConDecl name),	 -- Data constructors
		tcdDerivs :: Maybe (HsContext name),	-- Derivings; Nothing => not specified
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							-- Just [] => derive exactly what is asked
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		tcdGeneric :: Maybe Bool,	-- Nothing <=> source decl
						-- Just x  <=> interface-file decl;
						-- 	x=True <=> generic converter functions available
						-- We need this for imported data decls, since the
						-- imported modules may have been compiled with
						-- different flags to the current compilation unit
		tcdLoc	   :: SrcLoc
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    }

  | TySynonym {	tcdName :: name,		        -- type constructor
		tcdTyVars :: [HsTyVarBndr name],	-- type variables
		tcdSynRhs :: HsType name,	        -- synonym expansion
		tcdLoc    :: SrcLoc
    }

  | ClassDecl {	tcdCtxt    :: HsContext name, 	 	-- Context...
		tcdName    :: name,		    	-- Name of the class
		tcdTyVars  :: [HsTyVarBndr name],	-- The class type variables
		tcdFDs     :: [FunDep name],		-- Functional dependencies
		tcdSigs    :: [Sig name],		-- Methods' signatures
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		tcdMeths   :: Maybe (MonoBinds name),	-- Default methods
							-- 	Nothing for imported class decls
							-- 	Just bs for source   class decls
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		tcdLoc      :: SrcLoc
    }
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\end{code}

Simple classifiers

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

Dealing with names
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\begin{code}
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--------------------------------
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tyClDeclName :: TyClDecl name -> name
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tyClDeclName tycl_decl = tcdName tycl_decl
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--------------------------------
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tyClDeclNames :: Eq name => TyClDecl name -> [(name, SrcLoc)]
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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   {tcdName = name, tcdLoc = loc})  = [(name,loc)]
tyClDeclNames (IfaceSig    {tcdName = name, tcdLoc = loc})  = [(name,loc)]
tyClDeclNames (ForeignType {tcdName = name, tcdLoc = loc})  = [(name,loc)]
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tyClDeclNames (ClassDecl {tcdName = cls_name, tcdSigs = sigs, tcdLoc = loc})
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  = (cls_name,loc) : [(n,loc) | ClassOpSig n _ _ loc <- sigs]
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tyClDeclNames (TyData {tcdName = tc_name, tcdCons = cons, tcdLoc = loc})
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  = (tc_name,loc) : conDeclsNames cons
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tyClDeclTyVars (TySynonym {tcdTyVars = tvs}) = tvs
tyClDeclTyVars (TyData    {tcdTyVars = tvs}) = tvs
tyClDeclTyVars (ClassDecl {tcdTyVars = tvs}) = tvs
tyClDeclTyVars (ForeignType {})		     = []
tyClDeclTyVars (IfaceSig {})		     = []
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\end{code}

\begin{code}
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instance (NamedThing name, Ord name) => Eq (TyClDecl name) where
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	-- Used only when building interface files
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  (==) d1@(IfaceSig {}) d2@(IfaceSig {})
      = tcdName d1 == tcdName d2 && 
	tcdType d1 == tcdType d2 && 
	tcdIdInfo d1 == tcdIdInfo d2

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  (==) d1@(ForeignType {}) d2@(ForeignType {})
      = tcdName d1 == tcdName d2 && 
	tcdFoType d1 == tcdFoType d2

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  (==) d1@(TyData {}) d2@(TyData {})
      = tcdName d1 == tcdName d2 && 
	tcdND d1   == tcdND   d2 && 
	eqWithHsTyVars (tcdTyVars d1) (tcdTyVars d2) (\ env -> 
   	  eq_hsContext env (tcdCtxt d1) (tcdCtxt d2)  &&
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	  eq_hsCD      env (tcdCons d1) (tcdCons d2)
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	)

  (==) d1@(TySynonym {}) d2@(TySynonym {})
      = tcdName d1 == tcdName d2 && 
	eqWithHsTyVars (tcdTyVars d1) (tcdTyVars d2) (\ env -> 
          eq_hsType env (tcdSynRhs d1) (tcdSynRhs d2)
        )

  (==) d1@(ClassDecl {}) d2@(ClassDecl {})
    = tcdName d1 == tcdName d2 && 
      eqWithHsTyVars (tcdTyVars d1) (tcdTyVars d2) (\ env -> 
   	  eq_hsContext env (tcdCtxt d1) (tcdCtxt d2)  &&
	  eqListBy (eq_hsFD env) (tcdFDs d1) (tcdFDs d2) &&
	  eqListBy (eq_cls_sig env) (tcdSigs d1) (tcdSigs d2)
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       )

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  (==) _ _ = False	-- default case

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eq_hsCD env (DataCons c1) (DataCons c2) = eqListBy (eq_ConDecl env) c1 c2
eq_hsCD env Unknown	  Unknown	= True
eq_hsCD env (HasCons n1)  (HasCons n2)  = n1 == n2
eq_hsCD env d1		  d2		= False

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eq_hsFD env (ns1,ms1) (ns2,ms2)
  = eqListBy (eq_hsVar env) ns1 ns2 && eqListBy (eq_hsVar env) ms1 ms2

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eq_cls_sig env (ClassOpSig n1 dm1 ty1 _) (ClassOpSig n2 dm2 ty2 _)
  = n1==n2 && dm1 `eq_dm` dm2 && eq_hsType env ty1 ty2
  where
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	-- Ignore the name of the default method for (DefMeth id)
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	-- This is used for comparing declarations before putting
	-- them into interface files, and the name of the default 
	-- method isn't relevant
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    NoDefMeth  `eq_dm` NoDefMeth  = True
    GenDefMeth `eq_dm` GenDefMeth = True
    DefMeth _  `eq_dm` DefMeth _  = True
    dm1	       `eq_dm` dm2	  = False
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\end{code}

\begin{code}
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countTyClDecls :: [TyClDecl name] -> (Int, 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,
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    count isIfaceSigDecl  decls,
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    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 (IfaceSig {tcdName = var, tcdType = ty, tcdIdInfo = info})
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	= getPprStyle $ \ sty ->
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	   hsep [ pprHsVar var, dcolon, ppr ty, pprHsIdInfo info ]
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    ppr (ForeignType {tcdName = tycon})
	= hsep [ptext SLIT("foreign import type dotnet"), ppr tycon]

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    ppr (TySynonym {tcdName = tycon, tcdTyVars = tyvars, tcdSynRhs = mono_ty})
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      = hang (ptext SLIT("type") <+> pp_decl_head [] tycon tyvars <+> equals)
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	     4 (ppr mono_ty)
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    ppr (TyData {tcdND = new_or_data, tcdCtxt = context, tcdName = tycon,
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		 tcdTyVars = tyvars, tcdCons = condecls, 
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		 tcdDerivs = derivings})
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      = pp_tydecl (ptext keyword <+> pp_decl_head context tycon tyvars)
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		  (pp_condecls condecls)
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		  derivings
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      where
	keyword = case new_or_data of
			NewType  -> SLIT("newtype")
			DataType -> SLIT("data")
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    ppr (ClassDecl {tcdCtxt = context, tcdName = clas, tcdTyVars = tyvars, tcdFDs = fds,
		    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), pp_methods, char '}'])]
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      where
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        top_matter  = ptext SLIT("class") <+> pp_decl_head context clas tyvars <+> pprFundeps fds
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	ppr_sig sig = ppr sig <> semi
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	pp_methods = if isNothing methods
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			then empty
			else ppr (fromJust methods)
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pp_decl_head :: OutputableBndr name => HsContext name -> name -> [HsTyVarBndr name] -> SDoc
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pp_decl_head context thing tyvars = hsep [pprHsContext context, ppr thing, interppSP tyvars]
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pp_condecls Unknown	  = ptext SLIT("{- abstract -}")
pp_condecls (HasCons n)   = ptext SLIT("{- abstract with") <+> int n <+> ptext SLIT("constructors -}")
pp_condecls (DataCons 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"), ppr_hs_context ds]
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    ])
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\end{code}


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

\begin{code}
data ConDecl name
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  = ConDecl 	name			-- Constructor name; this is used for the
					-- DataCon itself, and for the user-callable wrapper Id

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

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		(HsConDetails name (BangType name))
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		SrcLoc
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\end{code}

\begin{code}
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conDeclsNames :: Eq name => DataConDetails (ConDecl name) -> [(name,SrcLoc)]
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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 ([], []) (visibleDataCons cons))
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  where
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    do_one (flds_seen, acc) (ConDecl name _ _ (RecCon flds) loc)
	= (new_flds ++ flds_seen, (name,loc) : [(f,loc) | f <- new_flds] ++ acc)
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	where
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	  new_flds = [ f | (f,_) <- flds, not (f `elem` flds_seen) ]
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    do_one (flds_seen, acc) (ConDecl name _ _ _ loc)
	= (flds_seen, (name,loc):acc)
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\end{code}

\begin{code}
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conDetailsTys details = map getBangType (hsConArgs details)
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eq_ConDecl env (ConDecl n1 tvs1 cxt1 cds1 _)
	       (ConDecl n2 tvs2 cxt2 cds2 _)
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  = n1 == n2 &&
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    (eq_hsTyVars env tvs1 tvs2	$ \ env ->
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     eq_hsContext env cxt1 cxt2	&&
     eq_ConDetails env cds1 cds2)

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eq_ConDetails env (PrefixCon bts1) (PrefixCon bts2)
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  = eqListBy (eq_btype env) bts1 bts2
eq_ConDetails env (InfixCon bta1 btb1) (InfixCon bta2 btb2)
  = eq_btype env bta1 bta2 && eq_btype env btb1 btb2
eq_ConDetails env (RecCon fs1) (RecCon fs2)
  = eqListBy (eq_fld env) fs1 fs2
eq_ConDetails env _ _ = False

eq_fld env (ns1,bt1) (ns2, bt2) = ns1==ns2 && eq_btype env bt1 bt2
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\end{code}
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\begin{code}
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data BangType name = BangType StrictnessMark (HsType name)

getBangType       (BangType _ ty) = ty
getBangStrictness (BangType s _)  = s

unbangedType ty = BangType NotMarkedStrict ty

eq_btype env (BangType s1 t1) (BangType s2 t2) = s1==s2 && eq_hsType env t1 t2
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\end{code}

\begin{code}
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instance (OutputableBndr name) => Outputable (ConDecl name) where
    ppr (ConDecl con tvs cxt con_details loc)
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      = sep [pprHsForAll tvs cxt, ppr_con_details con con_details]
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ppr_con_details con (InfixCon ty1 ty2)
  = hsep [ppr_bang ty1, ppr con, ppr_bang 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)
  = hsep (pprHsVar con : map ppr_bang 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_bang ty
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instance OutputableBndr name => Outputable (BangType name) where
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    ppr = ppr_bang

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ppr_bang (BangType s ty) = ppr s <> pprParendHsType ty
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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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data InstDecl name
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  = InstDecl	(HsType 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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		(MonoBinds name)
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		[Sig name]		-- User-supplied pragmatic info
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		(Maybe name)		-- Name for the dictionary function
					-- Nothing for source-file instance decls
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		SrcLoc
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isSourceInstDecl :: InstDecl name -> Bool
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isSourceInstDecl (InstDecl _ _ _ maybe_dfun _) = isNothing maybe_dfun
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\end{code}

\begin{code}
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instance (OutputableBndr name) => Outputable (InstDecl name) where
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    ppr (InstDecl inst_ty binds uprags maybe_dfun_name src_loc)
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      = vcat [hsep [ptext SLIT("instance"), ppr inst_ty, ptext SLIT("where")],
	      nest 4 (ppr uprags),
	      nest 4 (ppr binds) ]
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      where
	pp_dfun = case maybe_dfun_name of
		    Just df -> ppr df
		    Nothing -> empty
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\end{code}

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\begin{code}
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instance Ord name => Eq (InstDecl name) where
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	-- Used for interface comparison only, so don't compare bindings
  (==) (InstDecl inst_ty1 _ _ dfun1 _) (InstDecl inst_ty2 _ _ dfun2 _)
       = inst_ty1 == inst_ty2 && dfun1 == dfun2
\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}
data DefaultDecl name
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  = DefaultDecl	[HsType name]
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		SrcLoc

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instance (OutputableBndr name)
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	      => Outputable (DefaultDecl name) where

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    ppr (DefaultDecl tys src_loc)
      = 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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data ForeignDecl name
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  = ForeignImport name (HsType name) ForeignImport Bool SrcLoc  -- defines name
  | ForeignExport name (HsType name) ForeignExport Bool SrcLoc  -- uses name
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-- yield the Haskell name defined or used in a foreign declaration
--
foreignDeclName                           :: ForeignDecl name -> name
foreignDeclName (ForeignImport n _ _ _ _)  = n
foreignDeclName (ForeignExport n _ _ _ _)  = n
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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 _ _) =
    ptext SLIT("foreign import") <+> ppr fimport <+> 
    ppr n <+> dcolon <+> ppr ty
  ppr (ForeignExport n ty fexport _ _) =
    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 header lib (CFunction (CasmTarget _)) = 
        panic "HsDecls.pprCEntity: malformed C function target"
      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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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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	(HsExpr name)	-- LHS
	(HsExpr name)	-- RHS
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	SrcLoc		

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  | IfaceRule	 		-- One that's come in from an interface file; pre-typecheck
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	RuleName
	Activation
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	[UfBinder name]		-- Tyvars and term vars
	name			-- Head of lhs
	[UfExpr name]		-- Args of LHS
	(UfExpr name)		-- Pre typecheck
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	SrcLoc		

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  | IfaceRuleOut		-- Post typecheck
	name			-- Head of LHS
	CoreRule

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isSrcRule (HsRule _ _ _ _ _ _) = True
isSrcRule other		       = False

ifaceRuleDeclName :: RuleDecl name -> name
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ifaceRuleDeclName (IfaceRule _ _ _ n _ _ _) = n
ifaceRuleDeclName (IfaceRuleOut n r)	    = n
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ifaceRuleDeclName (HsRule fs _ _ _ _ _)     = pprPanic "ifaceRuleDeclName" (ppr fs)
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data RuleBndr name
  = RuleBndr name
  | RuleBndrSig name (HsType name)
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collectRuleBndrSigTys :: [RuleBndr name] -> [HsType name]
collectRuleBndrSigTys bndrs = [ty | RuleBndrSig _ ty <- bndrs]

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instance (NamedThing name, Ord name) => Eq (RuleDecl name) where
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  -- Works for IfaceRules only; used when comparing interface file versions
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  (IfaceRule n1 a1 bs1 f1 es1 rhs1 _) == (IfaceRule n2 a2 bs2 f2 es2 rhs2 _)
     = n1==n2 && f1 == f2 && a1==a2 &&
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       eq_ufBinders emptyEqHsEnv bs1 bs2 (\env -> 
       eqListBy (eq_ufExpr env) (rhs1:es1) (rhs2:es2))

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instance OutputableBndr name => Outputable (RuleDecl name) where
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  ppr (HsRule name act ns lhs rhs loc)
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	= sep [text "{-# RULES" <+> doubleQuotes (ftext name) <+> ppr act,
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	       pp_forall, pprExpr lhs, equals <+> pprExpr rhs,
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               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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  ppr (IfaceRule name act tpl_vars fn tpl_args rhs loc) 
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    = hsep [ doubleQuotes (ftext name), ppr act,
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	   ptext SLIT("__forall") <+> braces (interppSP tpl_vars),
	   ppr fn <+> sep (map (pprUfExpr parens) tpl_args),
	   ptext SLIT("=") <+> ppr rhs
      ] <+> semi

  ppr (IfaceRuleOut fn rule) = pprCoreRule (ppr fn) rule
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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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data DeprecDecl name = Deprecation name DeprecTxt SrcLoc
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type DeprecTxt = FastString	-- reason/explanation for deprecation
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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}
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%************************************************************************
%*									*
		External-core declarations
%*									*
%************************************************************************

\begin{code}
data CoreDecl name	-- a Core value binding (from 'external Core' input)
  = CoreDecl 	name
		(HsType name)
		(UfExpr name)
		SrcLoc
        
instance OutputableBndr name => Outputable (CoreDecl name) where
    ppr (CoreDecl var ty rhs loc)
	= getPprStyle $ \ sty ->
	  hsep [ pprHsVar var, dcolon, ppr ty, ppr rhs ]
\end{code}