X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2Ftypecheck%2FTcSplice.lhs;h=f68239ee26e8e267af6f222d3ad3d74df4b98b54;hb=191292aaa7f56f32fc546478f43aa89ac67c95a3;hp=2e813146f1ffb3499df374a47690a00dc20f7668;hpb=2a334098a6ec81a532bbe93183c2cf6c818c0c6c;p=ghc-hetmet.git

diff --git a/compiler/typecheck/TcSplice.lhs b/compiler/typecheck/TcSplice.lhs
index 2e81314..f68239e 100644
--- a/compiler/typecheck/TcSplice.lhs
+++ b/compiler/typecheck/TcSplice.lhs
@@ -348,10 +348,22 @@ tcBracket brack res_ty
           -- instance), but we aren't otherwise interested in the
           -- results. Nor do we care about ambiguous dictionaries etc.
           -- We will type check this bracket again at its usage site.
-       ; _ <- newImplication BracketSkol [] [] $
-              setStage brack_stage $
-              do { meta_ty <- tc_bracket cur_stage brack
-                 ; unifyType meta_ty res_ty }
+	  --
+	  -- We build a single implication constraint with a BracketSkol;
+	  -- that in turn tells simplifyCheck to report only definite
+	  -- errors
+       ; (_,lie) <- captureConstraints $
+              	    newImplication BracketSkol [] [] $
+              	    setStage brack_stage $
+              	    do { meta_ty <- tc_bracket cur_stage brack
+              	       ; unifyType meta_ty res_ty }
+
+          -- It's best to simplify the constraint now, even though in 
+	  -- principle some later unification might be useful for it,
+	  -- because we don't want these essentially-junk TH implication
+	  -- contraints floating around nested inside other constraints
+	  -- See for example Trac #4949
+       ; _ <- simplifyTop lie
 
         -- Return the original expression, not the type-decorated one
        ; pendings <- readMutVar pending_splices
@@ -374,7 +386,7 @@ tc_bracket outer_stage (VarBr name) 	-- Note [Quoting names]
 	}
 
 tc_bracket _ (ExpBr expr) 
-  = do	{ any_ty <- newFlexiTyVarTy liftedTypeKind
+  = do	{ any_ty <- newFlexiTyVarTy openTypeKind
 	; _ <- tcMonoExprNC expr any_ty  -- NC for no context; tcBracket does that
 	; tcMetaTy expQTyConName }
 	-- Result type is ExpQ (= Q Exp)
@@ -395,7 +407,7 @@ tc_bracket _ (DecBrG decls)
 	; tcMetaTy decsQTyConName } -- Result type is Q [Dec]
 
 tc_bracket _ (PatBr pat)
-  = do	{ any_ty <- newFlexiTyVarTy liftedTypeKind
+  = do	{ any_ty <- newFlexiTyVarTy openTypeKind
 	; _ <- tcPat ThPatQuote pat any_ty $ 
                return ()
 	; tcMetaTy patQTyConName }