[ci skip] typecheck: detabify/dewhitespace TcPat

Signed-off-by: Austin Seipp <austin@well-typed.com>

1 files changed, 334 insertions, 340 deletions

diff --git a/compiler/typecheck/TcPat.lhs b/compiler/typecheck/TcPat.lhs
index c052575c12..c4c3f88ac5 100644
--- a/compiler/typecheck/TcPat.lhs
+++ b/compiler/typecheck/TcPat.lhs
@@ -7,22 +7,16 @@ TcPat: Typechecking patterns
 
 \begin{code}
 {-# LANGUAGE CPP, RankNTypes #-}
-{-# 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 TcPat ( tcLetPat, TcSigFun, TcPragFun
              , TcSigInfo(..), findScopedTyVars
              , LetBndrSpec(..), addInlinePrags, warnPrags
              , tcPat, tcPats, newNoSigLetBndr
-	     , addDataConStupidTheta, badFieldCon, polyPatSig ) where
+             , addDataConStupidTheta, badFieldCon, polyPatSig ) where
 
 #include "HsVersions.h"
 
-import {-# SOURCE #-}	TcExpr( tcSyntaxOp, tcInferRho)
+import {-# SOURCE #-}   TcExpr( tcSyntaxOp, tcInferRho)
 
 import HsSyn
 import TcHsSyn
@@ -57,32 +51,32 @@ import Control.Monad
 
 
 %************************************************************************
-%*									*
-		External interface
-%*									*
+%*                                                                      *
+                External interface
+%*                                                                      *
 %************************************************************************
 
 \begin{code}
 tcLetPat :: TcSigFun -> LetBndrSpec
-      	 -> LPat Name -> TcSigmaType 
-     	 -> TcM a
-      	 -> TcM (LPat TcId, a)
+         -> LPat Name -> TcSigmaType
+         -> TcM a
+         -> TcM (LPat TcId, a)
 tcLetPat sig_fn no_gen pat pat_ty thing_inside
-  = tc_lpat pat pat_ty penv thing_inside 
+  = tc_lpat pat pat_ty penv thing_inside
   where
     penv = PE { pe_lazy = True
               , pe_ctxt = LetPat sig_fn no_gen }
 
 -----------------
 tcPats :: HsMatchContext Name
-       -> [LPat Name]		 -- Patterns,
-       -> [TcSigmaType]	         --   and their types
+       -> [LPat Name]            -- Patterns,
+       -> [TcSigmaType]          --   and their types
        -> TcM a                  --   and the checker for the body
        -> TcM ([LPat TcId], a)
 
 -- This is the externally-callable wrapper function
 -- Typecheck the patterns, extend the environment to bind the variables,
--- do the thing inside, use any existentially-bound dictionaries to 
+-- do the thing inside, use any existentially-bound dictionaries to
 -- discharge parts of the returning LIE, and deal with pattern type
 -- signatures
 
@@ -97,7 +91,7 @@ tcPats ctxt pats pat_tys thing_inside
     penv = PE { pe_lazy = False, pe_ctxt = LamPat ctxt }
 
 tcPat :: HsMatchContext Name
-      -> LPat Name -> TcSigmaType 
+      -> LPat Name -> TcSigmaType
       -> TcM a                 -- Checker for body, given
                                -- its result type
       -> TcM (LPat TcId, a)
@@ -105,31 +99,31 @@ tcPat ctxt pat pat_ty thing_inside
   = tc_lpat pat pat_ty penv thing_inside
   where
     penv = PE { pe_lazy = False, pe_ctxt = LamPat ctxt }
-   
+
 
 -----------------
 data PatEnv
-  = PE { pe_lazy :: Bool	-- True <=> lazy context, so no existentials allowed
-       , pe_ctxt :: PatCtxt   	-- Context in which the whole pattern appears
+  = PE { pe_lazy :: Bool        -- True <=> lazy context, so no existentials allowed
+       , pe_ctxt :: PatCtxt     -- Context in which the whole pattern appears
        }
 
 data PatCtxt
   = LamPat   -- Used for lambdas, case etc
-       (HsMatchContext Name) 
+       (HsMatchContext Name)
 
   | LetPat   -- Used only for let(rec) pattern bindings
-    	     -- See Note [Typing patterns in pattern bindings]
+             -- See Note [Typing patterns in pattern bindings]
        TcSigFun        -- Tells type sig if any
        LetBndrSpec     -- True <=> no generalisation of this let
 
-data LetBndrSpec 
-  = LetLclBndr		  -- The binder is just a local one;
-    			  -- an AbsBinds will provide the global version
+data LetBndrSpec
+  = LetLclBndr            -- The binder is just a local one;
+                          -- an AbsBinds will provide the global version
 
-  | LetGblBndr TcPragFun  -- Genrealisation plan is NoGen, so there isn't going 
+  | LetGblBndr TcPragFun  -- Genrealisation plan is NoGen, so there isn't going
                           -- to be an AbsBinds; So we must bind the global version
-                          -- of the binder right away.  
-    	       		  -- Oh, and dhhere is the inline-pragma information
+                          -- of the binder right away.
+                          -- Oh, and dhhere is the inline-pragma information
 
 makeLazy :: PatEnv -> PatEnv
 makeLazy penv = penv { pe_lazy = True }
@@ -146,7 +140,7 @@ data TcSigInfo
   = TcSigInfo {
         sig_id     :: TcId,         --  *Polymorphic* binder for this value...
 
-        sig_tvs    :: [(Maybe Name, TcTyVar)],    
+        sig_tvs    :: [(Maybe Name, TcTyVar)],
                            -- Instantiated type and kind variables
                            -- Just n <=> this skolem is lexically in scope with name n
                            -- See Note [Binding scoped type variables]
@@ -154,7 +148,7 @@ data TcSigInfo
         sig_theta  :: TcThetaType,  -- Instantiated theta
 
         sig_tau    :: TcSigmaType,  -- Instantiated tau
-		      		    -- See Note [sig_tau may be polymorphic]
+                                    -- See Note [sig_tau may be polymorphic]
 
         sig_loc    :: SrcSpan       -- The location of the signature
     }
@@ -231,14 +225,14 @@ but we need to be careful about "extra" tyvars. Consider
     (\C x -> d) : pat_ty -> res_ty
 When looking for existential escape we must check that the existential
 bound by C don't unify with the free variables of pat_ty, OR res_ty
-(or of course the environment).   Hence we need to keep track of the 
+(or of course the environment).   Hence we need to keep track of the
 res_ty free vars.
 
 
 %************************************************************************
-%*									*
-		Binders
-%*									*
+%*                                                                      *
+                Binders
+%*                                                                      *
 %************************************************************************
 
 \begin{code}
@@ -251,11 +245,11 @@ tcPatBndr (PE { pe_ctxt = LetPat lookup_sig no_gen}) bndr_name pat_ty
   | LetGblBndr prags <- no_gen
   , Just sig <- lookup_sig bndr_name
   = do { bndr_id <- addInlinePrags (sig_id sig) (prags bndr_name)
-       ; traceTc "tcPatBndr(gbl,sig)" (ppr bndr_id $$ ppr (idType bndr_id)) 
+       ; traceTc "tcPatBndr(gbl,sig)" (ppr bndr_id $$ ppr (idType bndr_id))
        ; co <- unifyPatType (idType bndr_id) pat_ty
        ; return (co, bndr_id) }
-      
-  | otherwise 
+
+  | otherwise
   = do { bndr_id <- newNoSigLetBndr no_gen bndr_name pat_ty
        ; traceTc "tcPatBndr(no-sig)" (ppr bndr_id $$ ppr (idType bndr_id))
        ; return (mkTcNomReflCo pat_ty, bndr_id) }
@@ -266,29 +260,29 @@ tcPatBndr (PE { pe_ctxt = _lam_or_proc }) bndr_name pat_ty
 
 ------------
 newNoSigLetBndr :: LetBndrSpec -> Name -> TcType -> TcM TcId
--- In the polymorphic case (no_gen = LetLclBndr), generate a "monomorphic version" 
+-- In the polymorphic case (no_gen = LetLclBndr), generate a "monomorphic version"
 --    of the Id; the original name will be bound to the polymorphic version
 --    by the AbsBinds
--- In the monomorphic case (no_gen = LetBglBndr) there is no AbsBinds, and we 
+-- In the monomorphic case (no_gen = LetBglBndr) there is no AbsBinds, and we
 --    use the original name directly
-newNoSigLetBndr LetLclBndr name ty 
+newNoSigLetBndr LetLclBndr name ty
   =do  { mono_name <- newLocalName name
        ; mkLocalBinder mono_name ty }
-newNoSigLetBndr (LetGblBndr prags) name ty 
+newNoSigLetBndr (LetGblBndr prags) name ty
   = do { id <- mkLocalBinder name ty
        ; addInlinePrags id (prags name) }
 
 ----------
 addInlinePrags :: TcId -> [LSig Name] -> TcM TcId
 addInlinePrags poly_id prags
-  = do { traceTc "addInlinePrags" (ppr poly_id $$ ppr prags) 
+  = do { traceTc "addInlinePrags" (ppr poly_id $$ ppr prags)
        ; tc_inl inl_sigs }
   where
     inl_sigs = filter isInlineLSig prags
     tc_inl [] = return poly_id
     tc_inl (L loc (InlineSig _ prag) : other_inls)
        = do { unless (null other_inls) (setSrcSpan loc warn_dup_inline)
-            ; traceTc "addInlinePrag" (ppr poly_id $$ ppr prag) 
+            ; traceTc "addInlinePrag" (ppr poly_id $$ ppr prag)
             ; return (poly_id `setInlinePragma` prag) }
     tc_inl _ = panic "tc_inl"
 
@@ -338,135 +332,135 @@ Two cases, dealt with by the LetPat case of tcPatBndr
 
 
 %************************************************************************
-%*									*
-		The main worker functions
-%*									*
+%*                                                                      *
+                The main worker functions
+%*                                                                      *
 %************************************************************************
 
 Note [Nesting]
 ~~~~~~~~~~~~~~
 tcPat takes a "thing inside" over which the pattern scopes.  This is partly
-so that tcPat can extend the environment for the thing_inside, but also 
+so that tcPat can extend the environment for the thing_inside, but also
 so that constraints arising in the thing_inside can be discharged by the
 pattern.
 
 This does not work so well for the ErrCtxt carried by the monad: we don't
-want the error-context for the pattern to scope over the RHS. 
+want the error-context for the pattern to scope over the RHS.
 Hence the getErrCtxt/setErrCtxt stuff in tcMultiple
 
 \begin{code}
 --------------------
 type Checker inp out =  forall r.
-			  inp
-		       -> PatEnv
-		       -> TcM r
-		       -> TcM (out, r)
+                          inp
+                       -> PatEnv
+                       -> TcM r
+                       -> TcM (out, r)
 
 tcMultiple :: Checker inp out -> Checker [inp] [out]
 tcMultiple tc_pat args penv thing_inside
-  = do	{ err_ctxt <- getErrCtxt
-	; let loop _ []
-		= do { res <- thing_inside
-		     ; return ([], res) }
-
-	      loop penv (arg:args)
-		= do { (p', (ps', res)) 
-				<- tc_pat arg penv $ 
-				   setErrCtxt err_ctxt $
-				   loop penv args
-		-- setErrCtxt: restore context before doing the next pattern
-		-- See note [Nesting] above
-				
-		     ; return (p':ps', res) }
-
-	; loop penv args }
+  = do  { err_ctxt <- getErrCtxt
+        ; let loop _ []
+                = do { res <- thing_inside
+                     ; return ([], res) }
+
+              loop penv (arg:args)
+                = do { (p', (ps', res))
+                                <- tc_pat arg penv $
+                                   setErrCtxt err_ctxt $
+                                   loop penv args
+                -- setErrCtxt: restore context before doing the next pattern
+                -- See note [Nesting] above
+
+                     ; return (p':ps', res) }
+
+        ; loop penv args }
 
 --------------------
-tc_lpat :: LPat Name 
-	-> TcSigmaType
-	-> PatEnv
-	-> TcM a
-	-> TcM (LPat TcId, a)
+tc_lpat :: LPat Name
+        -> TcSigmaType
+        -> PatEnv
+        -> TcM a
+        -> TcM (LPat TcId, a)
 tc_lpat (L span pat) pat_ty penv thing_inside
   = setSrcSpan span $
-    do	{ (pat', res) <- maybeWrapPatCtxt pat (tc_pat penv pat pat_ty)
+    do  { (pat', res) <- maybeWrapPatCtxt pat (tc_pat penv pat pat_ty)
                                           thing_inside
-	; return (L span pat', res) }
+        ; return (L span pat', res) }
 
 tc_lpats :: PatEnv
-	 -> [LPat Name] -> [TcSigmaType]
-       	 -> TcM a	
-       	 -> TcM ([LPat TcId], a)
-tc_lpats penv pats tys thing_inside 
+         -> [LPat Name] -> [TcSigmaType]
+         -> TcM a
+         -> TcM ([LPat TcId], a)
+tc_lpats penv pats tys thing_inside
   = ASSERT2( equalLength pats tys, ppr pats $$ ppr tys )
-    tcMultiple (\(p,t) -> tc_lpat p t) 
+    tcMultiple (\(p,t) -> tc_lpat p t)
                 (zipEqual "tc_lpats" pats tys)
-                penv thing_inside 
+                penv thing_inside
 
 --------------------
-tc_pat	:: PatEnv
-        -> Pat Name 
-        -> TcSigmaType	-- Fully refined result type
-        -> TcM a		-- Thing inside
-        -> TcM (Pat TcId, 	-- Translated pattern
-                a)		-- Result of thing inside
+tc_pat  :: PatEnv
+        -> Pat Name
+        -> TcSigmaType  -- Fully refined result type
+        -> TcM a                -- Thing inside
+        -> TcM (Pat TcId,       -- Translated pattern
+                a)              -- Result of thing inside
 
 tc_pat penv (VarPat name) pat_ty thing_inside
-  = do	{ (co, id) <- tcPatBndr penv name pat_ty
+  = do  { (co, id) <- tcPatBndr penv name pat_ty
         ; res <- tcExtendIdEnv1 name id thing_inside
         ; return (mkHsWrapPatCo co (VarPat id) pat_ty, res) }
 
 tc_pat penv (ParPat pat) pat_ty thing_inside
-  = do	{ (pat', res) <- tc_lpat pat pat_ty penv thing_inside
-	; return (ParPat pat', res) }
+  = do  { (pat', res) <- tc_lpat pat pat_ty penv thing_inside
+        ; return (ParPat pat', res) }
 
 tc_pat penv (BangPat pat) pat_ty thing_inside
-  = do	{ (pat', res) <- tc_lpat pat pat_ty penv thing_inside
-	; return (BangPat pat', res) }
+  = do  { (pat', res) <- tc_lpat pat pat_ty penv thing_inside
+        ; return (BangPat pat', res) }
 
 tc_pat penv lpat@(LazyPat pat) pat_ty thing_inside
-  = do	{ (pat', (res, pat_ct)) 
-		<- tc_lpat pat pat_ty (makeLazy penv) $ 
-		   captureConstraints thing_inside
-		-- Ignore refined penv', revert to penv
+  = do  { (pat', (res, pat_ct))
+                <- tc_lpat pat pat_ty (makeLazy penv) $
+                   captureConstraints thing_inside
+                -- Ignore refined penv', revert to penv
 
-	; emitConstraints pat_ct
-	-- captureConstraints/extendConstraints: 
+        ; emitConstraints pat_ct
+        -- captureConstraints/extendConstraints:
         --   see Note [Hopping the LIE in lazy patterns]
 
-	-- Check there are no unlifted types under the lazy pattern
-	; when (any (isUnLiftedType . idType) $ collectPatBinders pat') $
+        -- Check there are no unlifted types under the lazy pattern
+        ; when (any (isUnLiftedType . idType) $ collectPatBinders pat') $
                lazyUnliftedPatErr lpat
 
-	-- Check that the expected pattern type is itself lifted
-	; pat_ty' <- newFlexiTyVarTy liftedTypeKind
-	; _ <- unifyType pat_ty pat_ty'
+        -- Check that the expected pattern type is itself lifted
+        ; pat_ty' <- newFlexiTyVarTy liftedTypeKind
+        ; _ <- unifyType pat_ty pat_ty'
 
-	; return (LazyPat pat', res) }
+        ; return (LazyPat pat', res) }
 
 tc_pat _ p@(QuasiQuotePat _) _ _
   = pprPanic "Should never see QuasiQuotePat in type checker" (ppr p)
 
 tc_pat _ (WildPat _) pat_ty thing_inside
-  = do	{ res <- thing_inside 
-	; return (WildPat pat_ty, res) }
+  = do  { res <- thing_inside
+        ; return (WildPat pat_ty, res) }
 
 tc_pat penv (AsPat (L nm_loc name) pat) pat_ty thing_inside
-  = do	{ (co, bndr_id) <- setSrcSpan nm_loc (tcPatBndr penv name pat_ty)
+  = do  { (co, bndr_id) <- setSrcSpan nm_loc (tcPatBndr penv name pat_ty)
         ; (pat', res) <- tcExtendIdEnv1 name bndr_id $
-			 tc_lpat pat (idType bndr_id) penv thing_inside
-	    -- NB: if we do inference on:
-	    --		\ (y@(x::forall a. a->a)) = e
-	    -- we'll fail.  The as-pattern infers a monotype for 'y', which then
-	    -- fails to unify with the polymorphic type for 'x'.  This could 
-	    -- perhaps be fixed, but only with a bit more work.
-	    --
-	    -- If you fix it, don't forget the bindInstsOfPatIds!
-	; return (mkHsWrapPatCo co (AsPat (L nm_loc bndr_id) pat') pat_ty, res) }
-
-tc_pat penv (ViewPat expr pat _) overall_pat_ty thing_inside 
-  = do	{
-         -- Morally, expr must have type `forall a1...aN. OPT' -> B` 
+                         tc_lpat pat (idType bndr_id) penv thing_inside
+            -- NB: if we do inference on:
+            --          \ (y@(x::forall a. a->a)) = e
+            -- we'll fail.  The as-pattern infers a monotype for 'y', which then
+            -- fails to unify with the polymorphic type for 'x'.  This could
+            -- perhaps be fixed, but only with a bit more work.
+            --
+            -- If you fix it, don't forget the bindInstsOfPatIds!
+        ; return (mkHsWrapPatCo co (AsPat (L nm_loc bndr_id) pat') pat_ty, res) }
+
+tc_pat penv (ViewPat expr pat _) overall_pat_ty thing_inside
+  = do  {
+         -- Morally, expr must have type `forall a1...aN. OPT' -> B`
          -- where overall_pat_ty is an instance of OPT'.
          -- Here, we infer a rho type for it,
          -- which replaces the leading foralls and constraints
@@ -474,74 +468,74 @@ tc_pat penv (ViewPat expr pat _) overall_pat_ty thing_inside
         ; (expr',expr'_inferred) <- tcInferRho expr
 
          -- next, we check that expr is coercible to `overall_pat_ty -> pat_ty`
-         -- NOTE: this forces pat_ty to be a monotype (because we use a unification 
+         -- NOTE: this forces pat_ty to be a monotype (because we use a unification
          -- variable to find it).  this means that in an example like
          -- (view -> f)    where view :: _ -> forall b. b
          -- we will only be able to use view at one instantation in the
          -- rest of the view
-	; (expr_co, pat_ty) <- tcInfer $ \ pat_ty -> 
-		unifyType expr'_inferred (mkFunTy overall_pat_ty pat_ty)
-        
+        ; (expr_co, pat_ty) <- tcInfer $ \ pat_ty ->
+                unifyType expr'_inferred (mkFunTy overall_pat_ty pat_ty)
+
          -- pattern must have pat_ty
         ; (pat', res) <- tc_lpat pat pat_ty penv thing_inside
 
-	; return (ViewPat (mkLHsWrapCo expr_co expr') pat' overall_pat_ty, res) }
+        ; return (ViewPat (mkLHsWrapCo expr_co expr') pat' overall_pat_ty, res) }
 
 -- Type signatures in patterns
 -- See Note [Pattern coercions] below
 tc_pat penv (SigPatIn pat sig_ty) pat_ty thing_inside
-  = do	{ (inner_ty, tv_binds, wrap) <- tcPatSig (patSigCtxt penv) sig_ty pat_ty
-	; (pat', res) <- tcExtendTyVarEnv2 tv_binds $
-			 tc_lpat pat inner_ty penv thing_inside
+  = do  { (inner_ty, tv_binds, wrap) <- tcPatSig (patSigCtxt penv) sig_ty pat_ty
+        ; (pat', res) <- tcExtendTyVarEnv2 tv_binds $
+                         tc_lpat pat inner_ty penv thing_inside
 
         ; return (mkHsWrapPat wrap (SigPatOut pat' inner_ty) pat_ty, res) }
 
 ------------------------
 -- Lists, tuples, arrays
 tc_pat penv (ListPat pats _ Nothing) pat_ty thing_inside
-  = do	{ (coi, elt_ty) <- matchExpectedPatTy matchExpectedListTy pat_ty      
+  = do  { (coi, elt_ty) <- matchExpectedPatTy matchExpectedListTy pat_ty
         ; (pats', res) <- tcMultiple (\p -> tc_lpat p elt_ty)
-				     pats penv thing_inside
- 	; return (mkHsWrapPat coi (ListPat pats' elt_ty Nothing) pat_ty, res) 
+                                     pats penv thing_inside
+        ; return (mkHsWrapPat coi (ListPat pats' elt_ty Nothing) pat_ty, res)
         }
 
 tc_pat penv (ListPat pats _ (Just (_,e))) pat_ty thing_inside
-  = do	{ list_pat_ty <- newFlexiTyVarTy liftedTypeKind
+  = do  { list_pat_ty <- newFlexiTyVarTy liftedTypeKind
         ; e' <- tcSyntaxOp ListOrigin e (mkFunTy pat_ty list_pat_ty)
         ; (coi, elt_ty) <- matchExpectedPatTy matchExpectedListTy list_pat_ty
         ; (pats', res) <- tcMultiple (\p -> tc_lpat p elt_ty)
-				     pats penv thing_inside
- 	; return (mkHsWrapPat coi (ListPat pats' elt_ty (Just (pat_ty,e'))) list_pat_ty, res) 
+                                     pats penv thing_inside
+        ; return (mkHsWrapPat coi (ListPat pats' elt_ty (Just (pat_ty,e'))) list_pat_ty, res)
         }
 
 tc_pat penv (PArrPat pats _) pat_ty thing_inside
-  = do	{ (coi, elt_ty) <- matchExpectedPatTy matchExpectedPArrTy pat_ty
-	; (pats', res) <- tcMultiple (\p -> tc_lpat p elt_ty)
-				     pats penv thing_inside 
-	; return (mkHsWrapPat coi (PArrPat pats' elt_ty) pat_ty, res)
+  = do  { (coi, elt_ty) <- matchExpectedPatTy matchExpectedPArrTy pat_ty
+        ; (pats', res) <- tcMultiple (\p -> tc_lpat p elt_ty)
+                                     pats penv thing_inside
+        ; return (mkHsWrapPat coi (PArrPat pats' elt_ty) pat_ty, res)
         }
 
 tc_pat penv (TuplePat pats boxity _) pat_ty thing_inside
-  = do	{ let tc = tupleTyCon (boxityNormalTupleSort boxity) (length pats)
+  = do  { let tc = tupleTyCon (boxityNormalTupleSort boxity) (length pats)
         ; (coi, arg_tys) <- matchExpectedPatTy (matchExpectedTyConApp tc) pat_ty
-	; (pats', res) <- tc_lpats penv pats arg_tys thing_inside
+        ; (pats', res) <- tc_lpats penv pats arg_tys thing_inside
 
-	; dflags <- getDynFlags
+        ; dflags <- getDynFlags
 
-	-- Under flag control turn a pattern (x,y,z) into ~(x,y,z)
-	-- so that we can experiment with lazy tuple-matching.
-	-- This is a pretty odd place to make the switch, but
-	-- it was easy to do.
-	; let 
+        -- Under flag control turn a pattern (x,y,z) into ~(x,y,z)
+        -- so that we can experiment with lazy tuple-matching.
+        -- This is a pretty odd place to make the switch, but
+        -- it was easy to do.
+        ; let
               unmangled_result = TuplePat pats' boxity arg_tys
                                  -- pat_ty /= pat_ty iff coi /= IdCo
-	      possibly_mangled_result
-	        | gopt Opt_IrrefutableTuples dflags &&
+              possibly_mangled_result
+                | gopt Opt_IrrefutableTuples dflags &&
                   isBoxed boxity            = LazyPat (noLoc unmangled_result)
-	        | otherwise		    = unmangled_result
+                | otherwise                 = unmangled_result
 
- 	; ASSERT( length arg_tys == length pats )      -- Syntactically enforced
-	  return (mkHsWrapPat coi possibly_mangled_result pat_ty, res)
+        ; ASSERT( length arg_tys == length pats )      -- Syntactically enforced
+          return (mkHsWrapPat coi possibly_mangled_result pat_ty, res)
         }
 
 ------------------------
@@ -552,48 +546,48 @@ tc_pat penv (ConPatIn con arg_pats) pat_ty thing_inside
 ------------------------
 -- Literal patterns
 tc_pat _ (LitPat simple_lit) pat_ty thing_inside
-  = do	{ let lit_ty = hsLitType simple_lit
-	; co <- unifyPatType lit_ty pat_ty
-		-- coi is of kind: pat_ty ~ lit_ty
-	; res <- thing_inside 
-	; return ( mkHsWrapPatCo co (LitPat simple_lit) pat_ty 
+  = do  { let lit_ty = hsLitType simple_lit
+        ; co <- unifyPatType lit_ty pat_ty
+                -- coi is of kind: pat_ty ~ lit_ty
+        ; res <- thing_inside
+        ; return ( mkHsWrapPatCo co (LitPat simple_lit) pat_ty
                  , res) }
 
 ------------------------
 -- Overloaded patterns: n, and n+k
 tc_pat _ (NPat over_lit mb_neg eq) pat_ty thing_inside
-  = do	{ let orig = LiteralOrigin over_lit
-	; lit'    <- newOverloadedLit orig over_lit pat_ty
-	; eq'     <- tcSyntaxOp orig eq (mkFunTys [pat_ty, pat_ty] boolTy)
-	; mb_neg' <- case mb_neg of
-			Nothing  -> return Nothing	-- Positive literal
-			Just neg -> 	-- Negative literal
-					-- The 'negate' is re-mappable syntax
- 			    do { neg' <- tcSyntaxOp orig neg (mkFunTy pat_ty pat_ty)
-			       ; return (Just neg') }
-	; res <- thing_inside 
-	; return (NPat lit' mb_neg' eq', res) }
+  = do  { let orig = LiteralOrigin over_lit
+        ; lit'    <- newOverloadedLit orig over_lit pat_ty
+        ; eq'     <- tcSyntaxOp orig eq (mkFunTys [pat_ty, pat_ty] boolTy)
+        ; mb_neg' <- case mb_neg of
+                        Nothing  -> return Nothing      -- Positive literal
+                        Just neg ->     -- Negative literal
+                                        -- The 'negate' is re-mappable syntax
+                            do { neg' <- tcSyntaxOp orig neg (mkFunTy pat_ty pat_ty)
+                               ; return (Just neg') }
+        ; res <- thing_inside
+        ; return (NPat lit' mb_neg' eq', res) }
 
 tc_pat penv (NPlusKPat (L nm_loc name) lit ge minus) pat_ty thing_inside
-  = do	{ (co, bndr_id) <- setSrcSpan nm_loc (tcPatBndr penv name pat_ty)
+  = do  { (co, bndr_id) <- setSrcSpan nm_loc (tcPatBndr penv name pat_ty)
         ; let pat_ty' = idType bndr_id
-	      orig    = LiteralOrigin lit
-	; lit' <- newOverloadedLit orig lit pat_ty'
+              orig    = LiteralOrigin lit
+        ; lit' <- newOverloadedLit orig lit pat_ty'
 
-	-- The '>=' and '-' parts are re-mappable syntax
-	; ge'    <- tcSyntaxOp orig ge    (mkFunTys [pat_ty', pat_ty'] boolTy)
-	; minus' <- tcSyntaxOp orig minus (mkFunTys [pat_ty', pat_ty'] pat_ty')
+        -- The '>=' and '-' parts are re-mappable syntax
+        ; ge'    <- tcSyntaxOp orig ge    (mkFunTys [pat_ty', pat_ty'] boolTy)
+        ; minus' <- tcSyntaxOp orig minus (mkFunTys [pat_ty', pat_ty'] pat_ty')
         ; let pat' = NPlusKPat (L nm_loc bndr_id) lit' ge' minus'
 
-	-- The Report says that n+k patterns must be in Integral
-	-- We may not want this when using re-mappable syntax, though (ToDo?)
-	; icls <- tcLookupClass integralClassName
-	; instStupidTheta orig [mkClassPred icls [pat_ty']]	
-    
-	; res <- tcExtendIdEnv1 name bndr_id thing_inside
-	; return (mkHsWrapPatCo co pat' pat_ty, res) }
+        -- The Report says that n+k patterns must be in Integral
+        -- We may not want this when using re-mappable syntax, though (ToDo?)
+        ; icls <- tcLookupClass integralClassName
+        ; instStupidTheta orig [mkClassPred icls [pat_ty']]
 
-tc_pat _ _other_pat _ _ = panic "tc_pat" 	-- ConPatOut, SigPatOut
+        ; res <- tcExtendIdEnv1 name bndr_id thing_inside
+        ; return (mkHsWrapPatCo co pat' pat_ty, res) }
+
+tc_pat _ _other_pat _ _ = panic "tc_pat"        -- ConPatOut, SigPatOut
 
 ----------------
 unifyPatType :: TcType -> TcType -> TcM TcCoercion
@@ -610,18 +604,18 @@ Note [Hopping the LIE in lazy patterns]
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 In a lazy pattern, we must *not* discharge constraints from the RHS
 from dictionaries bound in the pattern.  E.g.
-	f ~(C x) = 3
+        f ~(C x) = 3
 We can't discharge the Num constraint from dictionaries bound by
-the pattern C!  
+the pattern C!
 
-So we have to make the constraints from thing_inside "hop around" 
+So we have to make the constraints from thing_inside "hop around"
 the pattern.  Hence the captureConstraints and emitConstraints.
 
 The same thing ensures that equality constraints in a lazy match
 are not made available in the RHS of the match. For example
-	data T a where { T1 :: Int -> T Int; ... }
-	f :: T a -> Int -> a
-	f ~(T1 i) y = y
+        data T a where { T1 :: Int -> T Int; ... }
+        f :: T a -> Int -> a
+        f ~(T1 i) y = y
 It's obviously not sound to refine a to Int in the right
 hand side, because the arugment might not match T1 at all!
 
@@ -630,10 +624,10 @@ because they won't be in scope when we do the desugaring
 
 
 %************************************************************************
-%*									*
-	Most of the work for constructors is here
-	(the rest is in the ConPatIn case of tc_pat)
-%*									*
+%*                                                                      *
+        Most of the work for constructors is here
+        (the rest is in the ConPatIn case of tc_pat)
+%*                                                                      *
 %************************************************************************
 
 [Pattern matching indexed data types]
@@ -663,7 +657,7 @@ unify the family type list {(Int, c), w} with the instance types {(a, b), v}
 unification yields the substitution [a -> Int, b -> c, v -> w], which gives us
 the split arguments for the representation tycon :R123Map as {Int, c, w}
 
-In other words, boxySplitTyConAppWithFamily implicitly takes the coercion 
+In other words, boxySplitTyConAppWithFamily implicitly takes the coercion
 
   Co123Map a b v :: {Map (a, b) v ~ :R123Map a b v}
 
@@ -690,14 +684,14 @@ equality constraints that are used in conjunction with implication constraints
 to express the local scope of GADT refinements.
 
 \begin{code}
---	Running example:
+--      Running example:
 -- MkT :: forall a b c. (a~[b]) => b -> c -> T a
--- 	 with scrutinee of type (T ty)
+--       with scrutinee of type (T ty)
 
-tcConPat :: PatEnv -> Located Name 
-	 -> TcRhoType  	       	-- Type of the pattern
-	 -> HsConPatDetails Name -> TcM a
-	 -> TcM (Pat TcId, a)
+tcConPat :: PatEnv -> Located Name
+         -> TcRhoType           -- Type of the pattern
+         -> HsConPatDetails Name -> TcM a
+         -> TcM (Pat TcId, a)
 tcConPat penv con_lname@(L _ con_name) pat_ty arg_pats thing_inside
   = do  { con_like <- tcLookupConLike con_name
         ; case con_like of
@@ -708,94 +702,94 @@ tcConPat penv con_lname@(L _ con_name) pat_ty arg_pats thing_inside
         }
 
 tcDataConPat :: PatEnv -> Located Name -> DataCon
-	     -> TcRhoType  	       	-- Type of the pattern
-	     -> HsConPatDetails Name -> TcM a
-	     -> TcM (Pat TcId, a)
+             -> TcRhoType               -- Type of the pattern
+             -> HsConPatDetails Name -> TcM a
+             -> TcM (Pat TcId, a)
 tcDataConPat penv (L con_span con_name) data_con pat_ty arg_pats thing_inside
-  = do	{ let tycon = dataConTyCon data_con
-         	  -- For data families this is the representation tycon
-	      (univ_tvs, ex_tvs, eq_spec, theta, arg_tys, _)
+  = do  { let tycon = dataConTyCon data_con
+                  -- For data families this is the representation tycon
+              (univ_tvs, ex_tvs, eq_spec, theta, arg_tys, _)
                 = dataConFullSig data_con
               header = L con_span (RealDataCon data_con)
 
-	  -- Instantiate the constructor type variables [a->ty]
-	  -- This may involve doing a family-instance coercion, 
-	  -- and building a wrapper 
-	; (wrap, ctxt_res_tys) <- matchExpectedPatTy (matchExpectedConTy tycon) pat_ty
+          -- Instantiate the constructor type variables [a->ty]
+          -- This may involve doing a family-instance coercion,
+          -- and building a wrapper
+        ; (wrap, ctxt_res_tys) <- matchExpectedPatTy (matchExpectedConTy tycon) pat_ty
 
-	  -- Add the stupid theta
-	; setSrcSpan con_span $ addDataConStupidTheta data_con ctxt_res_tys
+          -- Add the stupid theta
+        ; setSrcSpan con_span $ addDataConStupidTheta data_con ctxt_res_tys
 
-	; checkExistentials ex_tvs penv 
+        ; checkExistentials ex_tvs penv
         ; (tenv, ex_tvs') <- tcInstSuperSkolTyVarsX
                                (zipTopTvSubst univ_tvs ctxt_res_tys) ex_tvs
                      -- Get location from monad, not from ex_tvs
 
         ; let -- pat_ty' = mkTyConApp tycon ctxt_res_tys
-	      -- pat_ty' is type of the actual constructor application
+              -- pat_ty' is type of the actual constructor application
               -- pat_ty' /= pat_ty iff coi /= IdCo
 
-	      arg_tys' = substTys tenv arg_tys
+              arg_tys' = substTys tenv arg_tys
 
         ; traceTc "tcConPat" (vcat [ ppr con_name, ppr univ_tvs, ppr ex_tvs, ppr eq_spec
                                    , ppr ex_tvs', ppr ctxt_res_tys, ppr arg_tys' ])
-	; if null ex_tvs && null eq_spec && null theta
-	  then do { -- The common case; no class bindings etc 
+        ; if null ex_tvs && null eq_spec && null theta
+          then do { -- The common case; no class bindings etc
                     -- (see Note [Arrows and patterns])
-		    (arg_pats', res) <- tcConArgs (RealDataCon data_con) arg_tys'
-						  arg_pats penv thing_inside
-		  ; let res_pat = ConPatOut { pat_con = header,
-			            	      pat_tvs = [], pat_dicts = [], 
+                    (arg_pats', res) <- tcConArgs (RealDataCon data_con) arg_tys'
+                                                  arg_pats penv thing_inside
+                  ; let res_pat = ConPatOut { pat_con = header,
+                                              pat_tvs = [], pat_dicts = [],
                                               pat_binds = emptyTcEvBinds,
-					      pat_args = arg_pats', 
+                                              pat_args = arg_pats',
                                               pat_arg_tys = ctxt_res_tys,
                                               pat_wrap = idHsWrapper }
 
-		  ; return (mkHsWrapPat wrap res_pat pat_ty, res) }
+                  ; return (mkHsWrapPat wrap res_pat pat_ty, res) }
 
-	  else do   -- The general case, with existential, 
+          else do   -- The general case, with existential,
                     -- and local equality constraints
-	{ let theta'   = substTheta tenv (eqSpecPreds eq_spec ++ theta)
+        { let theta'   = substTheta tenv (eqSpecPreds eq_spec ++ theta)
                            -- order is *important* as we generate the list of
                            -- dictionary binders from theta'
-	      no_equalities = not (any isEqPred theta')
+              no_equalities = not (any isEqPred theta')
               skol_info = case pe_ctxt penv of
                             LamPat mc -> PatSkol (RealDataCon data_con) mc
                             LetPat {} -> UnkSkol -- Doesn't matter
- 
+
         ; gadts_on    <- xoptM Opt_GADTs
         ; families_on <- xoptM Opt_TypeFamilies
-	; checkTc (no_equalities || gadts_on || families_on)
-		  (ptext (sLit "A pattern match on a GADT requires GADTs or TypeFamilies"))
-		  -- Trac #2905 decided that a *pattern-match* of a GADT
-		  -- should require the GADT language flag.  
-                  -- Re TypeFamilies see also #7156 
+        ; checkTc (no_equalities || gadts_on || families_on)
+                  (ptext (sLit "A pattern match on a GADT requires GADTs or TypeFamilies"))
+                  -- Trac #2905 decided that a *pattern-match* of a GADT
+                  -- should require the GADT language flag.
+                  -- Re TypeFamilies see also #7156
 
         ; given <- newEvVars theta'
         ; (ev_binds, (arg_pats', res))
-	     <- checkConstraints skol_info ex_tvs' given $
+             <- checkConstraints skol_info ex_tvs' given $
                 tcConArgs (RealDataCon data_con) arg_tys' arg_pats penv thing_inside
 
         ; let res_pat = ConPatOut { pat_con   = header,
-			            pat_tvs   = ex_tvs',
-			            pat_dicts = given,
-			            pat_binds = ev_binds,
-			            pat_args  = arg_pats', 
+                                    pat_tvs   = ex_tvs',
+                                    pat_dicts = given,
+                                    pat_binds = ev_binds,
+                                    pat_args  = arg_pats',
                                     pat_arg_tys = ctxt_res_tys,
                                     pat_wrap  = idHsWrapper }
-	; return (mkHsWrapPat wrap res_pat pat_ty, res)
-	} }
+        ; return (mkHsWrapPat wrap res_pat pat_ty, res)
+        } }
 
 tcPatSynPat :: PatEnv -> Located Name -> PatSyn
-	    -> TcRhoType  	       	-- Type of the pattern
-	    -> HsConPatDetails Name -> TcM a
-	    -> TcM (Pat TcId, a)
+            -> TcRhoType                -- Type of the pattern
+            -> HsConPatDetails Name -> TcM a
+            -> TcM (Pat TcId, a)
 tcPatSynPat penv (L con_span _) pat_syn pat_ty arg_pats thing_inside
-  = do	{ let (univ_tvs, ex_tvs, prov_theta, req_theta, arg_tys, ty) = patSynSig pat_syn
+  = do  { let (univ_tvs, ex_tvs, prov_theta, req_theta, arg_tys, ty) = patSynSig pat_syn
 
         ; (univ_tvs', inst_tys, subst) <- tcInstTyVars univ_tvs
 
-	; checkExistentials ex_tvs penv
+        ; checkExistentials ex_tvs penv
         ; (tenv, ex_tvs') <- tcInstSuperSkolTyVarsX subst ex_tvs
         ; let ty' = substTy tenv ty
               arg_tys' = substTys tenv arg_tys
@@ -816,7 +810,7 @@ tcPatSynPat penv (L con_span _) pat_syn pat_ty arg_pats thing_inside
         -- Using a pattern synonym requires the PatternSynonyms
         -- language flag to keep consistent with #2905
         ; patsyns_on <- xoptM Opt_PatternSynonyms
-	; checkTc patsyns_on
+        ; checkTc patsyns_on
                   (ptext (sLit "A pattern match on a pattern synonym requires PatternSynonyms"))
 
         ; let skol_info = case pe_ctxt penv of
@@ -833,25 +827,25 @@ tcPatSynPat penv (L con_span _) pat_syn pat_ty arg_pats thing_inside
 
         ; traceTc "checkConstraints }" (ppr ev_binds)
         ; let res_pat = ConPatOut { pat_con   = L con_span $ PatSynCon pat_syn,
-			            pat_tvs   = ex_tvs',
-			            pat_dicts = prov_dicts',
-			            pat_binds = ev_binds,
-			            pat_args  = arg_pats',
+                                    pat_tvs   = ex_tvs',
+                                    pat_dicts = prov_dicts',
+                                    pat_binds = ev_binds,
+                                    pat_args  = arg_pats',
                                     pat_arg_tys = mkTyVarTys univ_tvs',
                                     pat_wrap  = req_wrap }
-	; return (mkHsWrapPat wrap res_pat pat_ty, res) }
+        ; return (mkHsWrapPat wrap res_pat pat_ty, res) }
 
 ----------------------------
 matchExpectedPatTy :: (TcRhoType -> TcM (TcCoercion, a))
-                    -> TcRhoType -> TcM (HsWrapper, a) 
+                    -> TcRhoType -> TcM (HsWrapper, a)
 -- See Note [Matching polytyped patterns]
 -- Returns a wrapper : pat_ty ~ inner_ty
 matchExpectedPatTy inner_match pat_ty
   | null tvs && null theta
   = do { (co, res) <- inner_match pat_ty
        ; return (coToHsWrapper (mkTcSymCo co), res) }
-       	 -- The Sym is because the inner_match returns a coercion
-	 -- that is the other way round to matchExpectedPatTy
+         -- The Sym is because the inner_match returns a coercion
+         -- that is the other way round to matchExpectedPatTy
 
   | otherwise
   = do { (_, tys, subst) <- tcInstTyVars tvs
@@ -862,35 +856,35 @@ matchExpectedPatTy inner_match pat_ty
     (tvs, theta, tau) = tcSplitSigmaTy pat_ty
 
 ----------------------------
-matchExpectedConTy :: TyCon  	 -- The TyCon that this data 
-		    		 -- constructor actually returns
-		   -> TcRhoType  -- The type of the pattern
-		   -> TcM (TcCoercion, [TcSigmaType])
+matchExpectedConTy :: TyCon      -- The TyCon that this data
+                                 -- constructor actually returns
+                   -> TcRhoType  -- The type of the pattern
+                   -> TcM (TcCoercion, [TcSigmaType])
 -- See Note [Matching constructor patterns]
 -- Returns a coercion : T ty1 ... tyn ~ pat_ty
 -- This is the same way round as matchExpectedListTy etc
 -- but the other way round to matchExpectedPatTy
 matchExpectedConTy data_tc pat_ty
   | Just (fam_tc, fam_args, co_tc) <- tyConFamInstSig_maybe data_tc
-    	 -- Comments refer to Note [Matching constructor patterns]
-     	 -- co_tc :: forall a. T [a] ~ T7 a
+         -- Comments refer to Note [Matching constructor patterns]
+         -- co_tc :: forall a. T [a] ~ T7 a
   = do { (_, tys, subst) <- tcInstTyVars (tyConTyVars data_tc)
-       	     -- tys = [ty1,ty2]
+             -- tys = [ty1,ty2]
 
-       ; traceTc "matchExpectedConTy" (vcat [ppr data_tc, 
+       ; traceTc "matchExpectedConTy" (vcat [ppr data_tc,
                                              ppr (tyConTyVars data_tc),
                                              ppr fam_tc, ppr fam_args])
        ; co1 <- unifyType (mkTyConApp fam_tc (substTys subst fam_args)) pat_ty
-       	     -- co1 : T (ty1,ty2) ~ pat_ty
+             -- co1 : T (ty1,ty2) ~ pat_ty
 
        ; let co2 = mkTcUnbranchedAxInstCo Nominal co_tc tys
-       	     -- co2 : T (ty1,ty2) ~ T7 ty1 ty2
+             -- co2 : T (ty1,ty2) ~ T7 ty1 ty2
 
        ; return (mkTcSymCo co2 `mkTcTransCo` co1, tys) }
 
   | otherwise
   = matchExpectedTyConApp data_tc pat_ty
-       	     -- coi : T tys ~ pat_ty
+             -- coi : T tys ~ pat_ty
 \end{code}
 
 Note [Matching constructor patterns]
@@ -910,7 +904,7 @@ Suppose (coi, tys) = matchExpectedConType data_tc pat_ty
        Then we'll have internally generated
               data T7 p q = A p | B q
               axiom coT7 p q :: T (p,q) ~ T7 p q
- 
+
        So if pat_ty = T (ty1,ty2), we return (coi, [ty1,ty2]) such that
            coi = coi2 . coi1 : T7 t ~ pat_ty
            coi1 : T (ty1,ty2) ~ pat_ty
@@ -922,63 +916,63 @@ Suppose (coi, tys) = matchExpectedConType data_tc pat_ty
 
 \begin{code}
 tcConArgs :: ConLike -> [TcSigmaType]
-	  -> Checker (HsConPatDetails Name) (HsConPatDetails Id)
+          -> Checker (HsConPatDetails Name) (HsConPatDetails Id)
 
 tcConArgs con_like arg_tys (PrefixCon arg_pats) penv thing_inside
-  = do	{ checkTc (con_arity == no_of_args)	-- Check correct arity
-		  (arityErr "Constructor" con_like con_arity no_of_args)
-	; let pats_w_tys = zipEqual "tcConArgs" arg_pats arg_tys
-	; (arg_pats', res) <- tcMultiple tcConArg pats_w_tys
-					      penv thing_inside 
-	; return (PrefixCon arg_pats', res) }
+  = do  { checkTc (con_arity == no_of_args)     -- Check correct arity
+                  (arityErr "Constructor" con_like con_arity no_of_args)
+        ; let pats_w_tys = zipEqual "tcConArgs" arg_pats arg_tys
+        ; (arg_pats', res) <- tcMultiple tcConArg pats_w_tys
+                                              penv thing_inside
+        ; return (PrefixCon arg_pats', res) }
   where
     con_arity  = conLikeArity con_like
     no_of_args = length arg_pats
 
 tcConArgs con_like arg_tys (InfixCon p1 p2) penv thing_inside
-  = do	{ checkTc (con_arity == 2)	-- Check correct arity
+  = do  { checkTc (con_arity == 2)      -- Check correct arity
                   (arityErr "Constructor" con_like con_arity 2)
-	; let [arg_ty1,arg_ty2] = arg_tys	-- This can't fail after the arity check
-	; ([p1',p2'], res) <- tcMultiple tcConArg [(p1,arg_ty1),(p2,arg_ty2)]
-					      penv thing_inside
-	; return (InfixCon p1' p2', res) }
+        ; let [arg_ty1,arg_ty2] = arg_tys       -- This can't fail after the arity check
+        ; ([p1',p2'], res) <- tcMultiple tcConArg [(p1,arg_ty1),(p2,arg_ty2)]
+                                              penv thing_inside
+        ; return (InfixCon p1' p2', res) }
   where
     con_arity  = conLikeArity con_like
 
 tcConArgs con_like arg_tys (RecCon (HsRecFields rpats dd)) penv thing_inside
-  = do	{ (rpats', res) <- tcMultiple tc_field rpats penv thing_inside
-	; return (RecCon (HsRecFields rpats' dd), res) }
+  = do  { (rpats', res) <- tcMultiple tc_field rpats penv thing_inside
+        ; return (RecCon (HsRecFields rpats' dd), res) }
   where
     tc_field :: Checker (HsRecField FieldLabel (LPat Name)) (HsRecField TcId (LPat TcId))
     tc_field (HsRecField field_lbl pat pun) penv thing_inside
       = do { (sel_id, pat_ty) <- wrapLocFstM find_field_ty field_lbl
-	   ; (pat', res) <- tcConArg (pat, pat_ty) penv thing_inside
-	   ; return (HsRecField sel_id pat' pun, res) }
+           ; (pat', res) <- tcConArg (pat, pat_ty) penv thing_inside
+           ; return (HsRecField sel_id pat' pun, res) }
 
     find_field_ty :: FieldLabel -> TcM (Id, TcType)
     find_field_ty field_lbl
-	= case [ty | (f,ty) <- field_tys, f == field_lbl] of
+        = case [ty | (f,ty) <- field_tys, f == field_lbl] of
 
-		-- No matching field; chances are this field label comes from some
-		-- other record type (or maybe none).  If this happens, just fail,
+                -- No matching field; chances are this field label comes from some
+                -- other record type (or maybe none).  If this happens, just fail,
                 -- otherwise we get crashes later (Trac #8570), and similar:
-		--	f (R { foo = (a,b) }) = a+b
-		-- If foo isn't one of R's fields, we don't want to crash when
-		-- typechecking the "a+b".
-	   [] -> failWith (badFieldCon con_like field_lbl)
+                --      f (R { foo = (a,b) }) = a+b
+                -- If foo isn't one of R's fields, we don't want to crash when
+                -- typechecking the "a+b".
+           [] -> failWith (badFieldCon con_like field_lbl)
 
-		-- The normal case, when the field comes from the right constructor
-	   (pat_ty : extras) ->
-		ASSERT( null extras )
-		do { sel_id <- tcLookupField field_lbl
-		   ; return (sel_id, pat_ty) }
+                -- The normal case, when the field comes from the right constructor
+           (pat_ty : extras) ->
+                ASSERT( null extras )
+                do { sel_id <- tcLookupField field_lbl
+                   ; return (sel_id, pat_ty) }
 
     field_tys :: [(FieldLabel, TcType)]
     field_tys = case con_like of
         RealDataCon data_con -> zip (dataConFieldLabels data_con) arg_tys
-	  -- Don't use zipEqual! If the constructor isn't really a record, then
-	  -- dataConFieldLabels will be empty (and each field in the pattern
-	  -- will generate an error below).
+          -- Don't use zipEqual! If the constructor isn't really a record, then
+          -- dataConFieldLabels will be empty (and each field in the pattern
+          -- will generate an error below).
         PatSynCon{} -> []
 
 conLikeArity :: ConLike -> Arity
@@ -992,25 +986,25 @@ tcConArg (arg_pat, arg_ty) penv thing_inside
 
 \begin{code}
 addDataConStupidTheta :: DataCon -> [TcType] -> TcM ()
--- Instantiate the "stupid theta" of the data con, and throw 
+-- Instantiate the "stupid theta" of the data con, and throw
 -- the constraints into the constraint set
 addDataConStupidTheta data_con inst_tys
   | null stupid_theta = return ()
-  | otherwise	      = instStupidTheta origin inst_theta
+  | otherwise         = instStupidTheta origin inst_theta
   where
     origin = OccurrenceOf (dataConName data_con)
-	-- The origin should always report "occurrence of C"
-	-- even when C occurs in a pattern
+        -- The origin should always report "occurrence of C"
+        -- even when C occurs in a pattern
     stupid_theta = dataConStupidTheta data_con
     tenv = mkTopTvSubst (dataConUnivTyVars data_con `zip` inst_tys)
-    	 -- NB: inst_tys can be longer than the univ tyvars
-	 --     because the constructor might have existentials
+         -- NB: inst_tys can be longer than the univ tyvars
+         --     because the constructor might have existentials
     inst_theta = substTheta tenv stupid_theta
 \end{code}
 
 Note [Arrows and patterns]
 ~~~~~~~~~~~~~~~~~~~~~~~~~~
-(Oct 07) Arrow noation has the odd property that it involves 
+(Oct 07) Arrow noation has the odd property that it involves
 "holes in the scope". For example:
   expr :: Arrow a => a () Int
   expr = proc (y,z) -> do
@@ -1033,31 +1027,31 @@ plan for ordinary vanilla patterns to bypass the constraint
 simplification step.
 
 %************************************************************************
-%*									*
-		Note [Pattern coercions]
-%*									*
+%*                                                                      *
+                Note [Pattern coercions]
+%*                                                                      *
 %************************************************************************
 
 In principle, these program would be reasonable:
-	
-	f :: (forall a. a->a) -> Int
-	f (x :: Int->Int) = x 3
 
-	g :: (forall a. [a]) -> Bool
-	g [] = True
+        f :: (forall a. a->a) -> Int
+        f (x :: Int->Int) = x 3
+
+        g :: (forall a. [a]) -> Bool
+        g [] = True
 
 In both cases, the function type signature restricts what arguments can be passed
 in a call (to polymorphic ones).  The pattern type signature then instantiates this
 type.  For example, in the first case,  (forall a. a->a) <= Int -> Int, and we
 generate the translated term
-	f = \x' :: (forall a. a->a).  let x = x' Int in x 3
+        f = \x' :: (forall a. a->a).  let x = x' Int in x 3
 
 From a type-system point of view, this is perfectly fine, but it's *very* seldom useful.
 And it requires a significant amount of code to implement, because we need to decorate
-the translated pattern with coercion functions (generated from the subsumption check 
-by tcSub).  
+the translated pattern with coercion functions (generated from the subsumption check
+by tcSub).
 
-So for now I'm just insisting on type *equality* in patterns.  No subsumption. 
+So for now I'm just insisting on type *equality* in patterns.  No subsumption.
 
 Old notes about desugaring, at a time when pattern coercions were handled:
 
@@ -1065,20 +1059,20 @@ A SigPat is a type coercion and must be handled one at at time.  We can't
 combine them unless the type of the pattern inside is identical, and we don't
 bother to check for that.  For example:
 
-	data T = T1 Int | T2 Bool
-	f :: (forall a. a -> a) -> T -> t
-	f (g::Int->Int)   (T1 i) = T1 (g i)
-	f (g::Bool->Bool) (T2 b) = T2 (g b)
+        data T = T1 Int | T2 Bool
+        f :: (forall a. a -> a) -> T -> t
+        f (g::Int->Int)   (T1 i) = T1 (g i)
+        f (g::Bool->Bool) (T2 b) = T2 (g b)
 
 We desugar this as follows:
 
-	f = \ g::(forall a. a->a) t::T ->
-	    let gi = g Int
-	    in case t of { T1 i -> T1 (gi i)
-			   other ->
-	    let	gb = g Bool
-	    in case t of { T2 b -> T2 (gb b)
-			   other -> fail }}
+        f = \ g::(forall a. a->a) t::T ->
+            let gi = g Int
+            in case t of { T1 i -> T1 (gi i)
+                           other ->
+            let gb = g Bool
+            in case t of { T2 b -> T2 (gb b)
+                           other -> fail }}
 
 Note that we do not treat the first column of patterns as a
 column of variables, because the coerced variables (gi, gb)
@@ -1087,35 +1081,35 @@ But I don't think this is a common case, and if it was we could
 doubtless improve it.
 
 Meanwhile, the strategy is:
-	* treat each SigPat coercion (always non-identity coercions)
-		as a separate block
-	* deal with the stuff inside, and then wrap a binding round
-		the result to bind the new variable (gi, gb, etc)
+        * treat each SigPat coercion (always non-identity coercions)
+                as a separate block
+        * deal with the stuff inside, and then wrap a binding round
+                the result to bind the new variable (gi, gb, etc)
 
 
 %************************************************************************
-%*									*
+%*                                                                      *
 \subsection{Errors and contexts}
-%*									*
+%*                                                                      *
 %************************************************************************
 
 \begin{code}
 maybeWrapPatCtxt :: Pat Name -> (TcM a -> TcM b) -> TcM a -> TcM b
 -- Not all patterns are worth pushing a context
-maybeWrapPatCtxt pat tcm thing_inside 
+maybeWrapPatCtxt pat tcm thing_inside
   | not (worth_wrapping pat) = tcm thing_inside
   | otherwise                = addErrCtxt msg $ tcm $ popErrCtxt thing_inside
-    			       -- Remember to pop before doing thing_inside
+                               -- Remember to pop before doing thing_inside
   where
    worth_wrapping (VarPat {}) = False
    worth_wrapping (ParPat {}) = False
    worth_wrapping (AsPat {})  = False
-   worth_wrapping _  	      = True
+   worth_wrapping _           = True
    msg = hang (ptext (sLit "In the pattern:")) 2 (ppr pat)
 
 -----------------------------------------------
 checkExistentials :: [TyVar] -> PatEnv -> TcM ()
-	  -- See Note [Arrows and patterns]
+          -- See Note [Arrows and patterns]
 checkExistentials [] _                                 = return ()
 checkExistentials _ (PE { pe_ctxt = LetPat {}})        = failWithTc existentialLetPat
 checkExistentials _ (PE { pe_ctxt = LamPat ProcExpr }) = failWithTc existentialProcPat
@@ -1128,19 +1122,19 @@ existentialLazyPat
        2 (ptext (sLit "inside a lazy (~) pattern"))
 
 existentialProcPat :: SDoc
-existentialProcPat 
+existentialProcPat
   = ptext (sLit "Proc patterns cannot use existential or GADT data constructors")
 
 existentialLetPat :: SDoc
 existentialLetPat
   = vcat [text "My brain just exploded",
-	  text "I can't handle pattern bindings for existential or GADT data constructors.",
-	  text "Instead, use a case-expression, or do-notation, to unpack the constructor."]
+          text "I can't handle pattern bindings for existential or GADT data constructors.",
+          text "Instead, use a case-expression, or do-notation, to unpack the constructor."]
 
 badFieldCon :: ConLike -> Name -> SDoc
 badFieldCon con field
   = hsep [ptext (sLit "Constructor") <+> quotes (ppr con),
-	  ptext (sLit "does not have field"), quotes (ppr field)]
+          ptext (sLit "does not have field"), quotes (ppr field)]
 
 polyPatSig :: TcType -> SDoc
 polyPatSig sig_ty