X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2Ftypecheck%2FTcPat.lhs;h=82ac5e3596a53c1558c6800ed3f58f2b7b09a5fd;hb=3517c53d8a66149dcc3f971cf0577719e99d6d70;hp=b8bbed710cb58087a57170df2e6ac0ad5f1777f2;hpb=259d5ea8479dbbf0220335c740efebec1bc19a7f;p=ghc-hetmet.git

diff --git a/compiler/typecheck/TcPat.lhs b/compiler/typecheck/TcPat.lhs
index b8bbed7..82ac5e3 100644
--- a/compiler/typecheck/TcPat.lhs
+++ b/compiler/typecheck/TcPat.lhs
@@ -37,6 +37,7 @@ import TyCon
 import DataCon
 import PrelNames
 import BasicTypes hiding (SuccessFlag(..))
+import DynFlags	( DynFlag( Opt_GADTs ) )
 import SrcLoc
 import ErrUtils
 import Util
@@ -427,7 +428,7 @@ tc_pat pstate (orig@(ViewPat expr pat _)) overall_pat_ty thing_inside
 tc_pat pstate (SigPatIn pat sig_ty) pat_ty thing_inside
   = do	{ (inner_ty, tv_binds, coi) <- tcPatSig (patSigCtxt pstate) sig_ty 
                                                                     pat_ty
-        ; unless (isIdentityCoercion coi) $ 
+        ; unless (isIdentityCoI coi) $ 
             failWithTc (badSigPat pat_ty)
 	; (pat', tvs, res) <- tcExtendTyVarEnv2 tv_binds $
 			      tc_lpat pat inner_ty pstate thing_inside
@@ -670,6 +671,12 @@ tcConPat pstate con_span data_con tycon pat_ty arg_pats thing_inside
 	      pstate' | no_equalities = pstate
 		      | otherwise     = pstate { pat_eqs = True }
 
+        ; gadts_on <- doptM Opt_GADTs
+	; checkTc (no_equalities || gadts_on)
+	  	  (ptext (sLit "A pattern match on a GADT requires -XGADTs"))
+		  -- Trac #2905 decided that a *pattern-match* of a GADT
+		  -- should require the GADT language flag
+
 	; unless no_equalities $ checkTc (isRigidTy pat_ty) $
                                  nonRigidMatch (pat_ctxt pstate) data_con
 
@@ -702,7 +709,7 @@ tcConPat pstate con_span data_con tycon pat_ty arg_pats thing_inside
 	     ; (_, freshTvs, subst) <- tcInstTyVars (tyConTyVars tycon)
              ; let instTys' = substTys subst instTys
 	     ; cois <- boxyUnifyList instTys' scrutinee_arg_tys
-             ; let coi = if isIdentityCoercion coi1
+             ; let coi = if isIdentityCoI coi1
                          then  -- pat_ty was splittable
                                -- => boxyUnifyList had real work to do
                            mkTyConAppCoI fam_tycon instTys' cois
@@ -978,7 +985,7 @@ patCtxt pat 	    = Just (hang (ptext (sLit "In the pattern:"))
 existentialExplode :: LPat Name -> SDoc
 existentialExplode pat
   = hang (vcat [text "My brain just exploded.",
-	        text "I can't handle pattern bindings for existentially-quantified constructors.",
+	        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 "In the binding group for"])
 	4 (ppr pat)
@@ -1030,7 +1037,7 @@ existentialProcPat con
 lazyPatErr :: Pat name -> [TcTyVar] -> TcM ()
 lazyPatErr _ tvs
   = failWithTc $
-    hang (ptext (sLit "A lazy (~) pattern cannot bind existential type variables"))
+    hang (ptext (sLit "A lazy (~) pattern cannot match existential or GADT data constructors"))
        2 (vcat (map pprSkolTvBinding tvs))
 
 nonRigidMatch :: PatCtxt -> DataCon -> SDoc