Detab DataCon

Signed-off-by: Edward Z. Yang <ezyang@cs.stanford.edu>

1 files changed, 347 insertions, 353 deletions

diff --git a/compiler/basicTypes/DataCon.lhs b/compiler/basicTypes/DataCon.lhs
index 771aa303a1..fa9e2e9a97 100644
--- a/compiler/basicTypes/DataCon.lhs
+++ b/compiler/basicTypes/DataCon.lhs
@@ -6,45 +6,39 @@
 
 \begin{code}
 {-# LANGUAGE CPP, DeriveDataTypeable #-}
-{-# OPTIONS_GHC -fno-warn-tabs #-}
--- The above warning supression flag is a temporary kludge.
--- While working on this module you are encouraged to remove it and
--- detab the module (please do the detabbing in a separate patch). See
---     http://ghc.haskell.org/trac/ghc/wiki/Commentary/CodingStyle#TabsvsSpaces
--- for details
 
 module DataCon (
         -- * Main data types
-	DataCon, DataConRep(..), HsBang(..), StrictnessMark(..),
-	ConTag,
-	
-	-- ** Type construction
-	mkDataCon, fIRST_TAG,
-        buildAlgTyCon, 
-	
-	-- ** Type deconstruction
-	dataConRepType, dataConSig, dataConFullSig,
-	dataConName, dataConIdentity, dataConTag, dataConTyCon, 
+        DataCon, DataConRep(..), HsBang(..), StrictnessMark(..),
+        ConTag,
+
+        -- ** Type construction
+        mkDataCon, fIRST_TAG,
+        buildAlgTyCon,
+
+        -- ** Type deconstruction
+        dataConRepType, dataConSig, dataConFullSig,
+        dataConName, dataConIdentity, dataConTag, dataConTyCon,
         dataConOrigTyCon, dataConUserType,
-	dataConUnivTyVars, dataConExTyVars, dataConAllTyVars, 
-	dataConEqSpec, eqSpecPreds, dataConTheta,
-	dataConStupidTheta,  
-	dataConInstArgTys, dataConOrigArgTys, dataConOrigResTy,
-	dataConInstOrigArgTys, dataConRepArgTys, 
-	dataConFieldLabels, dataConFieldType,
-	dataConStrictMarks, 
-	dataConSourceArity, dataConRepArity, dataConRepRepArity,
-	dataConIsInfix,
-	dataConWorkId, dataConWrapId, dataConWrapId_maybe, dataConImplicitIds,
-	dataConRepStrictness, dataConRepBangs, dataConBoxer,
-
-	splitDataProductType_maybe,
+        dataConUnivTyVars, dataConExTyVars, dataConAllTyVars,
+        dataConEqSpec, eqSpecPreds, dataConTheta,
+        dataConStupidTheta,
+        dataConInstArgTys, dataConOrigArgTys, dataConOrigResTy,
+        dataConInstOrigArgTys, dataConRepArgTys,
+        dataConFieldLabels, dataConFieldType,
+        dataConStrictMarks,
+        dataConSourceArity, dataConRepArity, dataConRepRepArity,
+        dataConIsInfix,
+        dataConWorkId, dataConWrapId, dataConWrapId_maybe, dataConImplicitIds,
+        dataConRepStrictness, dataConRepBangs, dataConBoxer,
+
+        splitDataProductType_maybe,
 
         tyConsOfTyCon,
 
-	-- ** Predicates on DataCons
-	isNullarySrcDataCon, isNullaryRepDataCon, isTupleDataCon, isUnboxedTupleCon,
-	isVanillaDataCon, classDataCon, dataConCannotMatch,
+        -- ** Predicates on DataCons
+        isNullarySrcDataCon, isNullaryRepDataCon, isTupleDataCon, isUnboxedTupleCon,
+        isVanillaDataCon, classDataCon, dataConCannotMatch,
         isBanged, isMarkedStrict, eqHsBang,
 
         -- ** Promotion related functions
@@ -87,30 +81,30 @@ Data constructor representation
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 Consider the following Haskell data type declaration
 
-	data T = T !Int ![Int]
+        data T = T !Int ![Int]
 
 Using the strictness annotations, GHC will represent this as
 
-	data T = T Int# [Int]
+        data T = T Int# [Int]
 
 That is, the Int has been unboxed.  Furthermore, the Haskell source construction
 
-	T e1 e2
+        T e1 e2
 
 is translated to
 
-	case e1 of { I# x -> 
-	case e2 of { r ->
-	T x r }}
+        case e1 of { I# x ->
+        case e2 of { r ->
+        T x r }}
 
 That is, the first argument is unboxed, and the second is evaluated.  Finally,
 pattern matching is translated too:
 
-	case e of { T a b -> ... }
+        case e of { T a b -> ... }
 
 becomes
 
-	case e of { T a' b -> let a = I# a' in ... }
+        case e of { T a' b -> let a = I# a' in ... }
 
 To keep ourselves sane, we name the different versions of the data constructor
 differently, as follows.
@@ -120,13 +114,13 @@ Note [Data Constructor Naming]
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 Each data constructor C has two, and possibly up to four, Names associated with it:
 
-		   OccName   Name space	  Name of   Notes
+                   OccName   Name space   Name of   Notes
  ---------------------------------------------------------------------------
- The "data con itself" 	 C     DataName	  DataCon   In dom( GlobalRdrEnv )
- The "worker data con"	 C     VarName	  Id        The worker
- The "wrapper data con"	 $WC   VarName	  Id        The wrapper
+ The "data con itself"   C     DataName   DataCon   In dom( GlobalRdrEnv )
+ The "worker data con"   C     VarName    Id        The worker
+ The "wrapper data con"  $WC   VarName    Id        The wrapper
  The "newtype coercion"  :CoT  TcClsName  TyCon
- 
+
 EVERY data constructor (incl for newtypes) has the former two (the
 data con itself, and its worker.  But only some data constructors have a
 wrapper (see Note [The need for a wrapper]).
@@ -146,272 +140,272 @@ The "worker Id", is the actual data constructor.
 * For a *data* type, the worker *is* the data constructor;
   it has no unfolding
 
-* For a *newtype*, the worker has a compulsory unfolding which 
+* For a *newtype*, the worker has a compulsory unfolding which
   does a cast, e.g.
-	newtype T = MkT Int
-	The worker for MkT has unfolding
-		\\(x:Int). x `cast` sym CoT
+        newtype T = MkT Int
+        The worker for MkT has unfolding
+                \\(x:Int). x `cast` sym CoT
   Here CoT is the type constructor, witnessing the FC axiom
-	axiom CoT : T = Int
+        axiom CoT : T = Int
 
 The "wrapper Id", \$WC, goes as follows
 
-* Its type is exactly what it looks like in the source program. 
+* Its type is exactly what it looks like in the source program.
 
-* It is an ordinary function, and it gets a top-level binding 
+* It is an ordinary function, and it gets a top-level binding
   like any other function.
 
 * The wrapper Id isn't generated for a data type if there is
   nothing for the wrapper to do.  That is, if its defn would be
-	\$wC = C
+        \$wC = C
 
 Note [The need for a wrapper]
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 Why might the wrapper have anything to do?  Two reasons:
 
 * Unboxing strict fields (with -funbox-strict-fields)
-	data T = MkT !(Int,Int)
-	\$wMkT :: (Int,Int) -> T
-	\$wMkT (x,y) = MkT x y
-  Notice that the worker has two fields where the wapper has 
+        data T = MkT !(Int,Int)
+        \$wMkT :: (Int,Int) -> T
+        \$wMkT (x,y) = MkT x y
+  Notice that the worker has two fields where the wapper has
   just one.  That is, the worker has type
-		MkT :: Int -> Int -> T
+                MkT :: Int -> Int -> T
 
 * Equality constraints for GADTs
-	data T a where { MkT :: a -> T [a] }
+        data T a where { MkT :: a -> T [a] }
 
   The worker gets a type with explicit equality
   constraints, thus:
-	MkT :: forall a b. (a=[b]) => b -> T a
+        MkT :: forall a b. (a=[b]) => b -> T a
 
   The wrapper has the programmer-specified type:
-	\$wMkT :: a -> T [a]
-	\$wMkT a x = MkT [a] a [a] x
+        \$wMkT :: a -> T [a]
+        \$wMkT a x = MkT [a] a [a] x
   The third argument is a coerion
-	[a] :: [a]~[a]
+        [a] :: [a]~[a]
 
 INVARIANT: the dictionary constructor for a class
-	   never has a wrapper.
+           never has a wrapper.
 
 
 A note about the stupid context
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 Data types can have a context:
-	
-	data (Eq a, Ord b) => T a b = T1 a b | T2 a
+
+        data (Eq a, Ord b) => T a b = T1 a b | T2 a
 
 and that makes the constructors have a context too
 (notice that T2's context is "thinned"):
 
-	T1 :: (Eq a, Ord b) => a -> b -> T a b
-	T2 :: (Eq a) => a -> T a b
+        T1 :: (Eq a, Ord b) => a -> b -> T a b
+        T2 :: (Eq a) => a -> T a b
 
 Furthermore, this context pops up when pattern matching
 (though GHC hasn't implemented this, but it is in H98, and
 I've fixed GHC so that it now does):
 
-	f (T2 x) = x
+        f (T2 x) = x
 gets inferred type
-	f :: Eq a => T a b -> a
+        f :: Eq a => T a b -> a
 
 I say the context is "stupid" because the dictionaries passed
 are immediately discarded -- they do nothing and have no benefit.
 It's a flaw in the language.
 
-	Up to now [March 2002] I have put this stupid context into the
-	type of the "wrapper" constructors functions, T1 and T2, but
-	that turned out to be jolly inconvenient for generics, and
-	record update, and other functions that build values of type T
-	(because they don't have suitable dictionaries available).
+        Up to now [March 2002] I have put this stupid context into the
+        type of the "wrapper" constructors functions, T1 and T2, but
+        that turned out to be jolly inconvenient for generics, and
+        record update, and other functions that build values of type T
+        (because they don't have suitable dictionaries available).
 
-	So now I've taken the stupid context out.  I simply deal with
-	it separately in the type checker on occurrences of a
-	constructor, either in an expression or in a pattern.
+        So now I've taken the stupid context out.  I simply deal with
+        it separately in the type checker on occurrences of a
+        constructor, either in an expression or in a pattern.
 
-	[May 2003: actually I think this decision could evasily be
-	reversed now, and probably should be.  Generics could be
-	disabled for types with a stupid context; record updates now
-	(H98) needs the context too; etc.  It's an unforced change, so
-	I'm leaving it for now --- but it does seem odd that the
-	wrapper doesn't include the stupid context.]
+        [May 2003: actually I think this decision could evasily be
+        reversed now, and probably should be.  Generics could be
+        disabled for types with a stupid context; record updates now
+        (H98) needs the context too; etc.  It's an unforced change, so
+        I'm leaving it for now --- but it does seem odd that the
+        wrapper doesn't include the stupid context.]
 
 [July 04] With the advent of generalised data types, it's less obvious
 what the "stupid context" is.  Consider
-	C :: forall a. Ord a => a -> a -> T (Foo a)
+        C :: forall a. Ord a => a -> a -> T (Foo a)
 Does the C constructor in Core contain the Ord dictionary?  Yes, it must:
 
-	f :: T b -> Ordering
-	f = /\b. \x:T b. 
-	    case x of
-		C a (d:Ord a) (p:a) (q:a) -> compare d p q
+        f :: T b -> Ordering
+        f = /\b. \x:T b.
+            case x of
+                C a (d:Ord a) (p:a) (q:a) -> compare d p q
 
 Note that (Foo a) might not be an instance of Ord.
 
 %************************************************************************
-%*									*
+%*                                                                      *
 \subsection{Data constructors}
-%*									*
+%*                                                                      *
 %************************************************************************
 
 \begin{code}
 -- | A data constructor
 data DataCon
   = MkData {
-	dcName    :: Name,	-- This is the name of the *source data con*
-				-- (see "Note [Data Constructor Naming]" above)
-	dcUnique :: Unique, 	-- Cached from Name
-	dcTag    :: ConTag,     -- ^ Tag, used for ordering 'DataCon's
-
-	-- Running example:
-	--
-	-- 	*** As declared by the user
-	--  data T a where
-	--    MkT :: forall x y. (x~y,Ord x) => x -> y -> T (x,y)
-
-	-- 	*** As represented internally
-	--  data T a where
-	--    MkT :: forall a. forall x y. (a~(x,y),x~y,Ord x) => x -> y -> T a
-	-- 
-	-- The next six fields express the type of the constructor, in pieces
-	-- e.g.
-	--
-	--	dcUnivTyVars  = [a]
-	--	dcExTyVars    = [x,y]
-	--	dcEqSpec      = [a~(x,y)]
-	--	dcOtherTheta  = [x~y, Ord x]	
-	--	dcOrigArgTys  = [x,y]
-	--	dcRepTyCon       = T
-
-	dcVanilla :: Bool,	-- True <=> This is a vanilla Haskell 98 data constructor
-				--	    Its type is of form
-				--	        forall a1..an . t1 -> ... tm -> T a1..an
-				-- 	    No existentials, no coercions, nothing.
-				-- That is: dcExTyVars = dcEqSpec = dcOtherTheta = []
-		-- NB 1: newtypes always have a vanilla data con
-		-- NB 2: a vanilla constructor can still be declared in GADT-style 
-		--	 syntax, provided its type looks like the above.
-		--       The declaration format is held in the TyCon (algTcGadtSyntax)
-
-	dcUnivTyVars :: [TyVar],	-- Universally-quantified type vars [a,b,c]
-					-- INVARIANT: length matches arity of the dcRepTyCon
-					---           result type of (rep) data con is exactly (T a b c)
-
-	dcExTyVars   :: [TyVar],	-- Existentially-quantified type vars 
-		-- In general, the dcUnivTyVars are NOT NECESSARILY THE SAME AS THE TYVARS
-		-- FOR THE PARENT TyCon. With GADTs the data con might not even have 
-		-- the same number of type variables.
-		-- [This is a change (Oct05): previously, vanilla datacons guaranteed to
-		--  have the same type variables as their parent TyCon, but that seems ugly.]
-
-	-- INVARIANT: the UnivTyVars and ExTyVars all have distinct OccNames
-	-- Reason: less confusing, and easier to generate IfaceSyn
-
-	dcEqSpec :: [(TyVar,Type)],	-- Equalities derived from the result type, 
-					-- _as written by the programmer_
-		-- This field allows us to move conveniently between the two ways
-		-- of representing a GADT constructor's type:
-		--	MkT :: forall a b. (a ~ [b]) => b -> T a
-		--	MkT :: forall b. b -> T [b]
-		-- Each equality is of the form (a ~ ty), where 'a' is one of 
-		-- the universally quantified type variables
-					
-		-- The next two fields give the type context of the data constructor
-		-- 	(aside from the GADT constraints, 
-		--	 which are given by the dcExpSpec)
-		-- In GADT form, this is *exactly* what the programmer writes, even if
-		-- the context constrains only universally quantified variables
-		--	MkT :: forall a b. (a ~ b, Ord b) => a -> T a b
-	dcOtherTheta :: ThetaType,  -- The other constraints in the data con's type
-		                    -- other than those in the dcEqSpec
-
-	dcStupidTheta :: ThetaType,	-- The context of the data type declaration 
-					--	data Eq a => T a = ...
-					-- or, rather, a "thinned" version thereof
-		-- "Thinned", because the Report says
-		-- to eliminate any constraints that don't mention
-		-- tyvars free in the arg types for this constructor
-		--
-		-- INVARIANT: the free tyvars of dcStupidTheta are a subset of dcUnivTyVars
-		-- Reason: dcStupidTeta is gotten by thinning the stupid theta from the tycon
-		-- 
-		-- "Stupid", because the dictionaries aren't used for anything.  
-		-- Indeed, [as of March 02] they are no longer in the type of 
-		-- the wrapper Id, because that makes it harder to use the wrap-id 
-		-- to rebuild values after record selection or in generics.
-
-	dcOrigArgTys :: [Type],		-- Original argument types
-					-- (before unboxing and flattening of strict fields)
-	dcOrigResTy :: Type,		-- Original result type, as seen by the user
-		-- NB: for a data instance, the original user result type may 
-		-- differ from the DataCon's representation TyCon.  Example
-		--	data instance T [a] where MkT :: a -> T [a]
-		-- The OrigResTy is T [a], but the dcRepTyCon might be :T123
-
-	-- Now the strictness annotations and field labels of the constructor
+        dcName    :: Name,      -- This is the name of the *source data con*
+                                -- (see "Note [Data Constructor Naming]" above)
+        dcUnique :: Unique,     -- Cached from Name
+        dcTag    :: ConTag,     -- ^ Tag, used for ordering 'DataCon's
+
+        -- Running example:
+        --
+        --      *** As declared by the user
+        --  data T a where
+        --    MkT :: forall x y. (x~y,Ord x) => x -> y -> T (x,y)
+
+        --      *** As represented internally
+        --  data T a where
+        --    MkT :: forall a. forall x y. (a~(x,y),x~y,Ord x) => x -> y -> T a
+        --
+        -- The next six fields express the type of the constructor, in pieces
+        -- e.g.
+        --
+        --      dcUnivTyVars  = [a]
+        --      dcExTyVars    = [x,y]
+        --      dcEqSpec      = [a~(x,y)]
+        --      dcOtherTheta  = [x~y, Ord x]
+        --      dcOrigArgTys  = [x,y]
+        --      dcRepTyCon       = T
+
+        dcVanilla :: Bool,      -- True <=> This is a vanilla Haskell 98 data constructor
+                                --          Its type is of form
+                                --              forall a1..an . t1 -> ... tm -> T a1..an
+                                --          No existentials, no coercions, nothing.
+                                -- That is: dcExTyVars = dcEqSpec = dcOtherTheta = []
+                -- NB 1: newtypes always have a vanilla data con
+                -- NB 2: a vanilla constructor can still be declared in GADT-style
+                --       syntax, provided its type looks like the above.
+                --       The declaration format is held in the TyCon (algTcGadtSyntax)
+
+        dcUnivTyVars :: [TyVar],        -- Universally-quantified type vars [a,b,c]
+                                        -- INVARIANT: length matches arity of the dcRepTyCon
+                                        ---           result type of (rep) data con is exactly (T a b c)
+
+        dcExTyVars   :: [TyVar],        -- Existentially-quantified type vars
+                -- In general, the dcUnivTyVars are NOT NECESSARILY THE SAME AS THE TYVARS
+                -- FOR THE PARENT TyCon. With GADTs the data con might not even have
+                -- the same number of type variables.
+                -- [This is a change (Oct05): previously, vanilla datacons guaranteed to
+                --  have the same type variables as their parent TyCon, but that seems ugly.]
+
+        -- INVARIANT: the UnivTyVars and ExTyVars all have distinct OccNames
+        -- Reason: less confusing, and easier to generate IfaceSyn
+
+        dcEqSpec :: [(TyVar,Type)],     -- Equalities derived from the result type,
+                                        -- _as written by the programmer_
+                -- This field allows us to move conveniently between the two ways
+                -- of representing a GADT constructor's type:
+                --      MkT :: forall a b. (a ~ [b]) => b -> T a
+                --      MkT :: forall b. b -> T [b]
+                -- Each equality is of the form (a ~ ty), where 'a' is one of
+                -- the universally quantified type variables
+
+                -- The next two fields give the type context of the data constructor
+                --      (aside from the GADT constraints,
+                --       which are given by the dcExpSpec)
+                -- In GADT form, this is *exactly* what the programmer writes, even if
+                -- the context constrains only universally quantified variables
+                --      MkT :: forall a b. (a ~ b, Ord b) => a -> T a b
+        dcOtherTheta :: ThetaType,  -- The other constraints in the data con's type
+                                    -- other than those in the dcEqSpec
+
+        dcStupidTheta :: ThetaType,     -- The context of the data type declaration
+                                        --      data Eq a => T a = ...
+                                        -- or, rather, a "thinned" version thereof
+                -- "Thinned", because the Report says
+                -- to eliminate any constraints that don't mention
+                -- tyvars free in the arg types for this constructor
+                --
+                -- INVARIANT: the free tyvars of dcStupidTheta are a subset of dcUnivTyVars
+                -- Reason: dcStupidTeta is gotten by thinning the stupid theta from the tycon
+                --
+                -- "Stupid", because the dictionaries aren't used for anything.
+                -- Indeed, [as of March 02] they are no longer in the type of
+                -- the wrapper Id, because that makes it harder to use the wrap-id
+                -- to rebuild values after record selection or in generics.
+
+        dcOrigArgTys :: [Type],         -- Original argument types
+                                        -- (before unboxing and flattening of strict fields)
+        dcOrigResTy :: Type,            -- Original result type, as seen by the user
+                -- NB: for a data instance, the original user result type may
+                -- differ from the DataCon's representation TyCon.  Example
+                --      data instance T [a] where MkT :: a -> T [a]
+                -- The OrigResTy is T [a], but the dcRepTyCon might be :T123
+
+        -- Now the strictness annotations and field labels of the constructor
         -- See Note [Bangs on data constructor arguments]
-	dcArgBangs :: [HsBang],
-		-- Strictness annotations as decided by the compiler.  
-		-- Matches 1-1 with dcOrigArgTys
-		-- Hence length = dataConSourceArity dataCon
-
-	dcFields  :: [FieldLabel],
-		-- Field labels for this constructor, in the
-		-- same order as the dcOrigArgTys; 
-		-- length = 0 (if not a record) or dataConSourceArity.
-
-	-- The curried worker function that corresponds to the constructor:
-	-- It doesn't have an unfolding; the code generator saturates these Ids
-	-- and allocates a real constructor when it finds one.
-	dcWorkId :: Id,
-
-	-- Constructor representation
+        dcArgBangs :: [HsBang],
+                -- Strictness annotations as decided by the compiler.
+                -- Matches 1-1 with dcOrigArgTys
+                -- Hence length = dataConSourceArity dataCon
+
+        dcFields  :: [FieldLabel],
+                -- Field labels for this constructor, in the
+                -- same order as the dcOrigArgTys;
+                -- length = 0 (if not a record) or dataConSourceArity.
+
+        -- The curried worker function that corresponds to the constructor:
+        -- It doesn't have an unfolding; the code generator saturates these Ids
+        -- and allocates a real constructor when it finds one.
+        dcWorkId :: Id,
+
+        -- Constructor representation
         dcRep      :: DataConRep,
 
         -- Cached
         dcRepArity    :: Arity,  -- == length dataConRepArgTys
         dcSourceArity :: Arity,  -- == length dcOrigArgTys
 
-	-- Result type of constructor is T t1..tn
-	dcRepTyCon  :: TyCon,		-- Result tycon, T
+        -- Result type of constructor is T t1..tn
+        dcRepTyCon  :: TyCon,           -- Result tycon, T
 
-	dcRepType   :: Type,	-- Type of the constructor
-				-- 	forall a x y. (a~(x,y), x~y, Ord x) =>
+        dcRepType   :: Type,    -- Type of the constructor
+                                --      forall a x y. (a~(x,y), x~y, Ord x) =>
                                 --        x -> y -> T a
-				-- (this is *not* of the constructor wrapper Id:
-				--  see Note [Data con representation] below)
-	-- Notice that the existential type parameters come *second*.  
-	-- Reason: in a case expression we may find:
-	--	case (e :: T t) of
+                                -- (this is *not* of the constructor wrapper Id:
+                                --  see Note [Data con representation] below)
+        -- Notice that the existential type parameters come *second*.
+        -- Reason: in a case expression we may find:
+        --      case (e :: T t) of
         --        MkT x y co1 co2 (d:Ord x) (v:r) (w:F s) -> ...
-	-- It's convenient to apply the rep-type of MkT to 't', to get
-	--	forall x y. (t~(x,y), x~y, Ord x) => x -> y -> T t
-	-- and use that to check the pattern.  Mind you, this is really only
-	-- used in CoreLint.
+        -- It's convenient to apply the rep-type of MkT to 't', to get
+        --      forall x y. (t~(x,y), x~y, Ord x) => x -> y -> T t
+        -- and use that to check the pattern.  Mind you, this is really only
+        -- used in CoreLint.
 
 
-	dcInfix :: Bool,	-- True <=> declared infix
-				-- Used for Template Haskell and 'deriving' only
-				-- The actual fixity is stored elsewhere
+        dcInfix :: Bool,        -- True <=> declared infix
+                                -- Used for Template Haskell and 'deriving' only
+                                -- The actual fixity is stored elsewhere
 
         dcPromoted :: Maybe TyCon    -- The promoted TyCon if this DataCon is promotable
                                      -- See Note [Promoted data constructors] in TyCon
   }
   deriving Data.Typeable.Typeable
 
-data DataConRep 
+data DataConRep
   = NoDataConRep              -- No wrapper
 
-  | DCR { dcr_wrap_id :: Id   -- Takes src args, unboxes/flattens, 
+  | DCR { dcr_wrap_id :: Id   -- Takes src args, unboxes/flattens,
                               -- and constructs the representation
 
         , dcr_boxer   :: DataConBoxer
 
-        , dcr_arg_tys :: [Type]  -- Final, representation argument types, 
+        , dcr_arg_tys :: [Type]  -- Final, representation argument types,
                                  -- after unboxing and flattening,
                                  -- and *including* all evidence args
 
         , dcr_stricts :: [StrictnessMark]  -- 1-1 with dcr_arg_tys
-		-- See also Note [Data-con worker strictness] in MkId.lhs
+                -- See also Note [Data-con worker strictness] in MkId.lhs
 
         , dcr_bangs :: [HsBang]  -- The actual decisions made (including failures)
                                  -- 1-1 with orig_arg_tys
@@ -420,7 +414,7 @@ data DataConRep
     }
 -- Algebraic data types always have a worker, and
 -- may or may not have a wrapper, depending on whether
--- the wrapper does anything.  
+-- the wrapper does anything.
 --
 -- Data types have a worker with no unfolding
 -- Newtypes just have a worker, which has a compulsory unfolding (just a cast)
@@ -436,7 +430,7 @@ data DataConRep
 -- but it also ensures that the wrapper is replaced
 -- by the worker (because it *is* the worker)
 -- even when there are no args. E.g. in
--- 		f (:) x
+--              f (:) x
 -- the (:) *is* the worker.
 -- This is really important in rule matching,
 -- (We could match on the wrappers,
@@ -446,14 +440,14 @@ data DataConRep
 -------------------------
 -- HsBang describes what the *programmer* wrote
 -- This info is retained in the DataCon.dcStrictMarks field
-data HsBang 
+data HsBang
   = HsUserBang   -- The user's source-code request
        (Maybe Bool)       -- Just True    {-# UNPACK #-}
                           -- Just False   {-# NOUNPACK #-}
                           -- Nothing      no pragma
        Bool               -- True <=> '!' specified
 
-  | HsNoBang	          -- Lazy field
+  | HsNoBang              -- Lazy field
                           -- HsUserBang Nothing False means the same as HsNoBang
 
   | HsUnpack              -- Definite commitment: this field is strict and unboxed
@@ -463,9 +457,9 @@ data HsBang
   deriving (Data.Data, Data.Typeable)
 
 -------------------------
--- StrictnessMark is internal only, used to indicate strictness 
+-- StrictnessMark is internal only, used to indicate strictness
 -- of the DataCon *worker* fields
-data StrictnessMark = MarkedStrict | NotMarkedStrict	
+data StrictnessMark = MarkedStrict | NotMarkedStrict
 \end{code}
 
 Note [Data con representation]
@@ -473,17 +467,17 @@ Note [Data con representation]
 The dcRepType field contains the type of the representation of a contructor
 This may differ from the type of the contructor *Id* (built
 by MkId.mkDataConId) for two reasons:
-	a) the constructor Id may be overloaded, but the dictionary isn't stored
-	   e.g.    data Eq a => T a = MkT a a
+        a) the constructor Id may be overloaded, but the dictionary isn't stored
+           e.g.    data Eq a => T a = MkT a a
 
-	b) the constructor may store an unboxed version of a strict field.
+        b) the constructor may store an unboxed version of a strict field.
 
 Here's an example illustrating both:
-	data Ord a => T a = MkT Int! a
+        data Ord a => T a = MkT Int! a
 Here
-	T :: Ord a => Int -> a -> T a
+        T :: Ord a => Int -> a -> T a
 but the rep type is
-	Trep :: Int# -> a -> T a
+        Trep :: Int# -> a -> T a
 Actually, the unboxed part isn't implemented yet!
 
 Note [Bangs on data constructor arguments]
@@ -509,9 +503,9 @@ dcr_bangs field; we don't know what the user originally said.
 
 
 %************************************************************************
-%*									*
+%*                                                                      *
 \subsection{Instances}
-%*									*
+%*                                                                      *
 %************************************************************************
 
 \begin{code}
@@ -521,9 +515,9 @@ instance Eq DataCon where
 
 instance Ord DataCon where
     a <= b = getUnique a <= getUnique b
-    a <	 b = getUnique a <  getUnique b
+    a <  b = getUnique a <  getUnique b
     a >= b = getUnique a >= getUnique b
-    a >	 b = getUnique a > getUnique b
+    a >  b = getUnique a > getUnique b
     compare a b = getUnique a `compare` getUnique b
 
 instance Uniquable DataCon where
@@ -582,42 +576,42 @@ isMarkedStrict _               = True   -- All others are strict
 
 
 %************************************************************************
-%*									*
+%*                                                                      *
 \subsection{Construction}
-%*									*
+%*                                                                      *
 %************************************************************************
 
 \begin{code}
 -- | Build a new data constructor
-mkDataCon :: Name 
-	  -> Bool	        -- ^ Is the constructor declared infix?
-	  -> [HsBang]           -- ^ Strictness annotations written in the source file
-	  -> [FieldLabel]       -- ^ Field labels for the constructor, if it is a record, 
-				--   otherwise empty
-	  -> [TyVar]            -- ^ Universally quantified type variables
-	  -> [TyVar]            -- ^ Existentially quantified type variables
-	  -> [(TyVar,Type)]     -- ^ GADT equalities
-	  -> ThetaType          -- ^ Theta-type occuring before the arguments proper
-	  -> [Type]             -- ^ Original argument types
-	  -> Type		-- ^ Original result type
-	  -> TyCon              -- ^ Representation type constructor
-	  -> ThetaType          -- ^ The "stupid theta", context of the data declaration 
-				--   e.g. @data Eq a => T a ...@
+mkDataCon :: Name
+          -> Bool               -- ^ Is the constructor declared infix?
+          -> [HsBang]           -- ^ Strictness annotations written in the source file
+          -> [FieldLabel]       -- ^ Field labels for the constructor, if it is a record,
+                                --   otherwise empty
+          -> [TyVar]            -- ^ Universally quantified type variables
+          -> [TyVar]            -- ^ Existentially quantified type variables
+          -> [(TyVar,Type)]     -- ^ GADT equalities
+          -> ThetaType          -- ^ Theta-type occuring before the arguments proper
+          -> [Type]             -- ^ Original argument types
+          -> Type               -- ^ Original result type
+          -> TyCon              -- ^ Representation type constructor
+          -> ThetaType          -- ^ The "stupid theta", context of the data declaration
+                                --   e.g. @data Eq a => T a ...@
           -> Id                 -- ^ Worker Id
-	  -> DataConRep         -- ^ Representation
-	  -> DataCon
+          -> DataConRep         -- ^ Representation
+          -> DataCon
   -- Can get the tag from the TyCon
 
 mkDataCon name declared_infix
-	  arg_stricts	-- Must match orig_arg_tys 1-1
-	  fields
-	  univ_tvs ex_tvs 
-	  eq_spec theta
-	  orig_arg_tys orig_res_ty rep_tycon
-	  stupid_theta work_id rep
--- Warning: mkDataCon is not a good place to check invariants. 
+          arg_stricts   -- Must match orig_arg_tys 1-1
+          fields
+          univ_tvs ex_tvs
+          eq_spec theta
+          orig_arg_tys orig_res_ty rep_tycon
+          stupid_theta work_id rep
+-- Warning: mkDataCon is not a good place to check invariants.
 -- If the programmer writes the wrong result type in the decl, thus:
---	data T a where { MkT :: S }
+--      data T a where { MkT :: S }
 -- then it's possible that the univ_tvs may hit an assertion failure
 -- if you pull on univ_tvs.  This case is checked by checkValidDataCon,
 -- so the error is detected properly... it's just that asaertions here
@@ -626,39 +620,39 @@ mkDataCon name declared_infix
   = con
   where
     is_vanilla = null ex_tvs && null eq_spec && null theta
-    con = MkData {dcName = name, dcUnique = nameUnique name, 
-		  dcVanilla = is_vanilla, dcInfix = declared_infix,
-	  	  dcUnivTyVars = univ_tvs, dcExTyVars = ex_tvs, 
-		  dcEqSpec = eq_spec, 
-		  dcOtherTheta = theta,
-		  dcStupidTheta = stupid_theta, 
-		  dcOrigArgTys = orig_arg_tys, dcOrigResTy = orig_res_ty,
-		  dcRepTyCon = rep_tycon, 
-		  dcArgBangs = arg_stricts, 
-		  dcFields = fields, dcTag = tag, dcRepType = rep_ty,
-		  dcWorkId = work_id,
-                  dcRep = rep, 
+    con = MkData {dcName = name, dcUnique = nameUnique name,
+                  dcVanilla = is_vanilla, dcInfix = declared_infix,
+                  dcUnivTyVars = univ_tvs, dcExTyVars = ex_tvs,
+                  dcEqSpec = eq_spec,
+                  dcOtherTheta = theta,
+                  dcStupidTheta = stupid_theta,
+                  dcOrigArgTys = orig_arg_tys, dcOrigResTy = orig_res_ty,
+                  dcRepTyCon = rep_tycon,
+                  dcArgBangs = arg_stricts,
+                  dcFields = fields, dcTag = tag, dcRepType = rep_ty,
+                  dcWorkId = work_id,
+                  dcRep = rep,
                   dcSourceArity = length orig_arg_tys,
                   dcRepArity = length rep_arg_tys,
                   dcPromoted = mb_promoted }
 
-	-- The 'arg_stricts' passed to mkDataCon are simply those for the
-	-- source-language arguments.  We add extra ones for the
-	-- dictionary arguments right here.
+        -- The 'arg_stricts' passed to mkDataCon are simply those for the
+        -- source-language arguments.  We add extra ones for the
+        -- dictionary arguments right here.
 
     tag = assoc "mkDataCon" (tyConDataCons rep_tycon `zip` [fIRST_TAG..]) con
     rep_arg_tys = dataConRepArgTys con
-    rep_ty = mkForAllTys univ_tvs $ mkForAllTys ex_tvs $ 
-	     mkFunTys rep_arg_tys $
-	     mkTyConApp rep_tycon (mkTyVarTys univ_tvs)
+    rep_ty = mkForAllTys univ_tvs $ mkForAllTys ex_tvs $
+             mkFunTys rep_arg_tys $
+             mkTyConApp rep_tycon (mkTyVarTys univ_tvs)
 
     mb_promoted   -- See Note [Promoted data constructors] in TyCon
       | isJust (promotableTyCon_maybe rep_tycon)
           -- The TyCon is promotable only if all its datacons
           -- are, so the promoteType for prom_kind should succeed
       = Just (mkPromotedDataCon con name (getUnique name) prom_kind roles)
-      | otherwise 
-      = Nothing          
+      | otherwise
+      = Nothing
     prom_kind = promoteType (dataConUserType con)
     roles = map (const Nominal)          (univ_tvs ++ ex_tvs) ++
             map (const Representational) orig_arg_tys
@@ -693,7 +687,7 @@ dataConTyCon = dcRepTyCon
 -- constructor.  In case of a data family instance, that will be the family
 -- type constructor.
 dataConOrigTyCon :: DataCon -> TyCon
-dataConOrigTyCon dc 
+dataConOrigTyCon dc
   | Just (tc, _) <- tyConFamInst_maybe (dcRepTyCon dc) = tc
   | otherwise                                          = dcRepTyCon dc
 
@@ -726,7 +720,7 @@ dataConEqSpec = dcEqSpec
 
 -- | The *full* constraints on the constructor type
 dataConTheta :: DataCon -> ThetaType
-dataConTheta (MkData { dcEqSpec = eq_spec, dcOtherTheta = theta }) 
+dataConTheta (MkData { dcEqSpec = eq_spec, dcOtherTheta = theta })
   = eqSpecPreds eq_spec ++ theta
 
 -- | Get the Id of the 'DataCon' worker: a function that is the "actual"
@@ -738,7 +732,7 @@ dataConWorkId dc = dcWorkId dc
 
 -- | Get the Id of the 'DataCon' wrapper: a function that wraps the "actual"
 -- constructor so it has the type visible in the source program: c.f. 'dataConWorkId'.
--- Returns Nothing if there is no wrapper, which occurs for an algebraic data constructor 
+-- Returns Nothing if there is no wrapper, which occurs for an algebraic data constructor
 -- and also for a newtype (whose constructor is inlined compulsorily)
 dataConWrapId_maybe :: DataCon -> Maybe Id
 dataConWrapId_maybe dc = case dcRep dc of
@@ -781,7 +775,7 @@ dataConStrictMarks = dcArgBangs
 dataConSourceArity :: DataCon -> Arity
 dataConSourceArity (MkData { dcSourceArity = arity }) = arity
 
--- | Gives the number of actual fields in the /representation/ of the 
+-- | Gives the number of actual fields in the /representation/ of the
 -- data constructor. This may be more than appear in the source code;
 -- the extra ones are the existentially quantified dictionaries
 dataConRepArity :: DataCon -> Arity
@@ -815,7 +809,7 @@ dataConRepBangs dc = case dcRep dc of
 
 dataConBoxer :: DataCon -> Maybe DataConBoxer
 dataConBoxer (MkData { dcRep = DCR { dcr_boxer = boxer } }) = Just boxer
-dataConBoxer _ = Nothing 
+dataConBoxer _ = Nothing
 
 -- | The \"signature\" of the 'DataCon' returns, in order:
 --
@@ -828,9 +822,9 @@ dataConBoxer _ = Nothing
 --
 -- 4) The /original/ result type of the 'DataCon'
 dataConSig :: DataCon -> ([TyVar], ThetaType, [Type], Type)
-dataConSig (MkData {dcUnivTyVars = univ_tvs, dcExTyVars = ex_tvs, 
-		    dcEqSpec = eq_spec, dcOtherTheta  = theta, 
-		    dcOrigArgTys = arg_tys, dcOrigResTy = res_ty})
+dataConSig (MkData {dcUnivTyVars = univ_tvs, dcExTyVars = ex_tvs,
+                    dcEqSpec = eq_spec, dcOtherTheta  = theta,
+                    dcOrigArgTys = arg_tys, dcOrigResTy = res_ty})
   = (univ_tvs ++ ex_tvs, eqSpecPreds eq_spec ++ theta, arg_tys, res_ty)
 
 -- | The \"full signature\" of the 'DataCon' returns, in order:
@@ -843,15 +837,15 @@ dataConSig (MkData {dcUnivTyVars = univ_tvs, dcExTyVars = ex_tvs,
 --
 -- 4) The result of 'dataConDictTheta'
 --
--- 5) The original argument types to the 'DataCon' (i.e. before 
+-- 5) The original argument types to the 'DataCon' (i.e. before
 --    any change of the representation of the type)
 --
 -- 6) The original result type of the 'DataCon'
-dataConFullSig :: DataCon 
-	       -> ([TyVar], [TyVar], [(TyVar,Type)], ThetaType, [Type], Type)
-dataConFullSig (MkData {dcUnivTyVars = univ_tvs, dcExTyVars = ex_tvs, 
-			dcEqSpec = eq_spec, dcOtherTheta = theta,
-			dcOrigArgTys = arg_tys, dcOrigResTy = res_ty})
+dataConFullSig :: DataCon
+               -> ([TyVar], [TyVar], [(TyVar,Type)], ThetaType, [Type], Type)
+dataConFullSig (MkData {dcUnivTyVars = univ_tvs, dcExTyVars = ex_tvs,
+                        dcEqSpec = eq_spec, dcOtherTheta = theta,
+                        dcOrigArgTys = arg_tys, dcOrigResTy = res_ty})
   = (univ_tvs, ex_tvs, eq_spec, theta, arg_tys, res_ty)
 
 dataConOrigResTy :: DataCon -> Type
@@ -875,10 +869,10 @@ dataConUserType :: DataCon -> Type
 --
 -- NB: If the constructor is part of a data instance, the result type
 -- mentions the family tycon, not the internal one.
-dataConUserType  (MkData { dcUnivTyVars = univ_tvs, 
-			   dcExTyVars = ex_tvs, dcEqSpec = eq_spec,
-			   dcOtherTheta = theta, dcOrigArgTys = arg_tys,
-			   dcOrigResTy = res_ty })
+dataConUserType  (MkData { dcUnivTyVars = univ_tvs,
+                           dcExTyVars = ex_tvs, dcEqSpec = eq_spec,
+                           dcOtherTheta = theta, dcOrigArgTys = arg_tys,
+                           dcOrigResTy = res_ty })
   = mkForAllTys ((univ_tvs `minusList` map fst eq_spec) ++ ex_tvs) $
     mkFunTys theta $
     mkFunTys arg_tys $
@@ -888,13 +882,13 @@ dataConUserType  (MkData { dcUnivTyVars = univ_tvs,
 -- NB: these INCLUDE any dictionary args
 --     but EXCLUDE the data-declaration context, which is discarded
 -- It's all post-flattening etc; this is a representation type
-dataConInstArgTys :: DataCon	-- ^ A datacon with no existentials or equality constraints
-				-- However, it can have a dcTheta (notably it can be a 
-				-- class dictionary, with superclasses)
-	      	  -> [Type] 	-- ^ Instantiated at these types
-	      	  -> [Type]
+dataConInstArgTys :: DataCon    -- ^ A datacon with no existentials or equality constraints
+                                -- However, it can have a dcTheta (notably it can be a
+                                -- class dictionary, with superclasses)
+                  -> [Type]     -- ^ Instantiated at these types
+                  -> [Type]
 dataConInstArgTys dc@(MkData {dcUnivTyVars = univ_tvs, dcEqSpec = eq_spec,
-			      dcExTyVars = ex_tvs}) inst_tys
+                              dcExTyVars = ex_tvs}) inst_tys
  = ASSERT2( length univ_tvs == length inst_tys
           , ptext (sLit "dataConInstArgTys") <+> ppr dc $$ ppr univ_tvs $$ ppr inst_tys)
    ASSERT2( null ex_tvs && null eq_spec, ppr dc )
@@ -902,16 +896,16 @@ dataConInstArgTys dc@(MkData {dcUnivTyVars = univ_tvs, dcEqSpec = eq_spec,
 
 -- | Returns just the instantiated /value/ argument types of a 'DataCon',
 -- (excluding dictionary args)
-dataConInstOrigArgTys 
-	:: DataCon	-- Works for any DataCon
-	-> [Type]	-- Includes existential tyvar args, but NOT
-			-- equality constraints or dicts
-	-> [Type]
+dataConInstOrigArgTys
+        :: DataCon      -- Works for any DataCon
+        -> [Type]       -- Includes existential tyvar args, but NOT
+                        -- equality constraints or dicts
+        -> [Type]
 -- For vanilla datacons, it's all quite straightforward
 -- But for the call in MatchCon, we really do want just the value args
 dataConInstOrigArgTys dc@(MkData {dcOrigArgTys = arg_tys,
-			          dcUnivTyVars = univ_tvs, 
-			          dcExTyVars = ex_tvs}) inst_tys
+                                  dcUnivTyVars = univ_tvs,
+                                  dcExTyVars = ex_tvs}) inst_tys
   = ASSERT2( length tyvars == length inst_tys
           , ptext (sLit "dataConInstOrigArgTys") <+> ppr dc $$ ppr tyvars $$ ppr inst_tys )
     map (substTyWith tyvars inst_tys) arg_tys
@@ -925,13 +919,13 @@ dataConInstOrigArgTys dc@(MkData {dcOrigArgTys = arg_tys,
 dataConOrigArgTys :: DataCon -> [Type]
 dataConOrigArgTys dc = dcOrigArgTys dc
 
--- | Returns the arg types of the worker, including *all* evidence, after any 
+-- | Returns the arg types of the worker, including *all* evidence, after any
 -- flattening has been done and without substituting for any type variables
 dataConRepArgTys :: DataCon -> [Type]
-dataConRepArgTys (MkData { dcRep = rep 
+dataConRepArgTys (MkData { dcRep = rep
                          , dcEqSpec = eq_spec
                          , dcOtherTheta = theta
-		         , dcOrigArgTys = orig_arg_tys })
+                         , dcOrigArgTys = orig_arg_tys })
   = case rep of
       NoDataConRep -> ASSERT( null eq_spec ) theta ++ orig_arg_tys
       DCR { dcr_arg_tys = arg_tys } -> arg_tys
@@ -952,7 +946,7 @@ dataConIdentity dc = bytesFS (packageKeyFS (modulePackageKey mod)) ++
 \begin{code}
 isTupleDataCon :: DataCon -> Bool
 isTupleDataCon (MkData {dcRepTyCon = tc}) = isTupleTyCon tc
-	
+
 isUnboxedTupleCon :: DataCon -> Bool
 isUnboxedTupleCon (MkData {dcRepTyCon = tc}) = isUnboxedTupleTyCon tc
 
@@ -964,27 +958,27 @@ isVanillaDataCon dc = dcVanilla dc
 \begin{code}
 classDataCon :: Class -> DataCon
 classDataCon clas = case tyConDataCons (classTyCon clas) of
-		      (dict_constr:no_more) -> ASSERT( null no_more ) dict_constr 
-		      [] -> panic "classDataCon"
+                      (dict_constr:no_more) -> ASSERT( null no_more ) dict_constr
+                      [] -> panic "classDataCon"
 \end{code}
 
 \begin{code}
 dataConCannotMatch :: [Type] -> DataCon -> Bool
--- Returns True iff the data con *definitely cannot* match a 
---		    scrutinee of type (T tys)
---		    where T is the dcRepTyCon for the data con
+-- Returns True iff the data con *definitely cannot* match a
+--                  scrutinee of type (T tys)
+--                  where T is the dcRepTyCon for the data con
 -- NB: look at *all* equality constraints, not only those
 --     in dataConEqSpec; see Trac #5168
 dataConCannotMatch tys con
-  | null theta        = False	-- Common
-  | all isTyVarTy tys = False	-- Also common
+  | null theta        = False   -- Common
+  | all isTyVarTy tys = False   -- Also common
   | otherwise
   = typesCantMatch [(Type.substTy subst ty1, Type.substTy subst ty2)
                    | (ty1, ty2) <- concatMap predEqs theta ]
   where
     dc_tvs  = dataConUnivTyVars con
     theta   = dataConTheta con
-    subst   = ASSERT2( length dc_tvs == length tys, ppr con $$ ppr dc_tvs $$ ppr tys ) 
+    subst   = ASSERT2( length dc_tvs == length tys, ppr con $$ ppr dc_tvs $$ ppr tys )
               zipTopTvSubst dc_tvs tys
 
     -- TODO: could gather equalities from superclasses too
@@ -995,36 +989,36 @@ dataConCannotMatch tys con
 \end{code}
 
 %************************************************************************
-%*									*
+%*                                                                      *
               Building an algebraic data type
-%*									*
+%*                                                                      *
 %************************************************************************
 
 buildAlgTyCon is here because it is called from TysWiredIn, which in turn
 depends on DataCon, but not on BuildTyCl.
 
 \begin{code}
-buildAlgTyCon :: Name 
+buildAlgTyCon :: Name
               -> [TyVar]               -- ^ Kind variables and type variables
               -> [Role]
-	      -> Maybe CType
-	      -> ThetaType	       -- ^ Stupid theta
-	      -> AlgTyConRhs
-	      -> RecFlag
-	      -> Bool		       -- ^ True <=> this TyCon is promotable
-	      -> Bool		       -- ^ True <=> was declared in GADT syntax
+              -> Maybe CType
+              -> ThetaType             -- ^ Stupid theta
+              -> AlgTyConRhs
+              -> RecFlag
+              -> Bool                  -- ^ True <=> this TyCon is promotable
+              -> Bool                  -- ^ True <=> was declared in GADT syntax
               -> TyConParent
-	      -> TyCon
+              -> TyCon
 
-buildAlgTyCon tc_name ktvs roles cType stupid_theta rhs 
+buildAlgTyCon tc_name ktvs roles cType stupid_theta rhs
               is_rec is_promotable gadt_syn parent
   = tc
-  where 
+  where
     kind = mkPiKinds ktvs liftedTypeKind
 
     -- tc and mb_promoted_tc are mutually recursive
-    tc = mkAlgTyCon tc_name kind ktvs roles cType stupid_theta 
-                    rhs parent is_rec gadt_syn 
+    tc = mkAlgTyCon tc_name kind ktvs roles cType stupid_theta
+                    rhs parent is_rec gadt_syn
                     mb_promoted_tc
 
     mb_promoted_tc
@@ -1066,11 +1060,11 @@ The transformation from type to kind is done by promoteType
   * Ensure all foralls are at the top (no higher rank stuff)
 
   * Ensure that all type constructors mentioned (Maybe and T
-    in the example) are promotable; that is, they have kind 
+    in the example) are promotable; that is, they have kind
           * -> ... -> * -> *
 
 \begin{code}
--- | Promotes a type to a kind. 
+-- | Promotes a type to a kind.
 -- Assumes the argument satisfies 'isPromotableType'
 promoteType :: Type -> Kind
 promoteType ty
@@ -1083,23 +1077,23 @@ promoteType ty
     go (TyConApp tc tys) | Just prom_tc <- promotableTyCon_maybe tc
                          = mkTyConApp prom_tc (map go tys)
     go (FunTy arg res)   = mkArrowKind (go arg) (go res)
-    go (TyVarTy tv)      | Just kv <- lookupVarEnv env tv 
+    go (TyVarTy tv)      | Just kv <- lookupVarEnv env tv
                          = TyVarTy kv
     go _ = panic "promoteType"  -- Argument did not satisfy isPromotableType
 
 promoteKind :: Kind -> SuperKind
 -- Promote the kind of a type constructor
--- from (* -> * -> *) to (BOX -> BOX -> BOX) 
-promoteKind (TyConApp tc []) 
+-- from (* -> * -> *) to (BOX -> BOX -> BOX)
+promoteKind (TyConApp tc [])
   | tc `hasKey` liftedTypeKindTyConKey = superKind
 promoteKind (FunTy arg res) = FunTy (promoteKind arg) (promoteKind res)
 promoteKind k = pprPanic "promoteKind" (ppr k)
 \end{code}
 
 %************************************************************************
-%*									*
+%*                                                                      *
 \subsection{Splitting products}
-%*									*
+%*                                                                      *
 %************************************************************************
 
 \begin{code}
@@ -1116,15 +1110,15 @@ promoteKind k = pprPanic "promoteKind" (ppr k)
 --
 -- Whether the type is a @data@ type or a @newtype@
 splitDataProductType_maybe
-	:: Type 			-- ^ A product type, perhaps
-	-> Maybe (TyCon, 		-- The type constructor
-		  [Type],		-- Type args of the tycon
-		  DataCon,		-- The data constructor
-		  [Type])		-- Its /representation/ arg types
-
-	-- Rejecing existentials is conservative.  Maybe some things
-	-- could be made to work with them, but I'm not going to sweat
-	-- it through till someone finds it's important.
+        :: Type                         -- ^ A product type, perhaps
+        -> Maybe (TyCon,                -- The type constructor
+                  [Type],               -- Type args of the tycon
+                  DataCon,              -- The data constructor
+                  [Type])               -- Its /representation/ arg types
+
+        -- Rejecting existentials is conservative.  Maybe some things
+        -- could be made to work with them, but I'm not going to sweat
+        -- it through till someone finds it's important.
 
 splitDataProductType_maybe ty
   | Just (tycon, ty_args) <- splitTyConApp_maybe ty