Complain sensibly if you try to use scoped type variables in Template Haskell

[ghc-hetmet.git] / compiler / deSugar / DsMeta.hs

diff --git a/compiler/deSugar/DsMeta.hs b/compiler/deSugar/DsMeta.hs
index 7fbce31..9859167 100644 (file)
--- a/compiler/deSugar/DsMeta.hs
+++ b/compiler/deSugar/DsMeta.hs
@@ -17,7 +17,7 @@
 -- The above warning supression flag is a temporary kludge.
 -- While working on this module you are encouraged to remove it and fix
 -- any warnings in the module. See
---     http://hackage.haskell.org/trac/ghc/wiki/CodingStyle#Warnings
+--     http://hackage.haskell.org/trac/ghc/wiki/Commentary/CodingStyle#Warnings
 -- for details
 
 module DsMeta( dsBracket, 
@@ -424,7 +424,7 @@ repTy (HsForAllTy _ tvs ctxt ty)  =
 
 repTy (HsTyVar n)
   | isTvOcc (nameOccName n)       = do 
-                                     tv1 <- lookupBinder n
+                                     tv1 <- lookupTvOcc n
                                      repTvar tv1
   | otherwise                    = do 
                                      tc1 <- lookupOcc n
@@ -790,7 +790,7 @@ repLambda (L _ (Match ps _ (GRHSs [L _ (GRHS [] e)] EmptyLocalBinds)))
                do { xs <- repLPs ps; body <- repLE e; repLam xs body })
       ; wrapGenSyns ss lam }
 
-repLambda (L _ m) = notHandled "Guarded labmdas" (pprMatch LambdaExpr m)
+repLambda (L _ m) = notHandled "Guarded labmdas" (pprMatch (LambdaExpr :: HsMatchContext Name) m)
 
   
 -----------------------------------------------------------------------------
@@ -831,8 +831,8 @@ repP (ConPatIn dc details)
                                 p2' <- repLP p2;
                                 repPinfix p1' con_str p2' }
    }
-repP (NPat l Nothing _ _)  = do { a <- repOverloadedLiteral l; repPlit a }
-repP p@(NPat l (Just _) _ _) = notHandled "Negative overloaded patterns" (ppr p)
+repP (NPat l Nothing _)  = do { a <- repOverloadedLiteral l; repPlit a }
+repP p@(NPat l (Just _) _) = notHandled "Negative overloaded patterns" (ppr p)
 repP p@(SigPatIn {})  = notHandled "Type signatures in patterns" (ppr p)
        -- The problem is to do with scoped type variables.
        -- To implement them, we have to implement the scoping rules
@@ -917,6 +917,18 @@ lookupOcc n
                Just (Splice _) -> pprPanic "repE:lookupOcc" (ppr n) 
     }
 
+lookupTvOcc :: Name -> DsM (Core TH.Name)
+-- Type variables can't be staged and are not lexically scoped in TH
+lookupTvOcc n  
+  = do {  mb_val <- dsLookupMetaEnv n ;
+          case mb_val of
+               Just (Bound x)  -> return (coreVar x)
+               other           -> failWithDs msg
+    }
+  where
+    msg = vcat  [ ptext SLIT("Illegal lexically-scoped type variable") <+> quotes (ppr n)
+               , ptext SLIT("Lexically scoped type variables are not supported by Template Haskell") ]
+
 globalVar :: Name -> DsM (Core TH.Name)
 -- Not bound by the meta-env
 -- Could be top-level; or could be local
@@ -1277,9 +1289,9 @@ mk_string s   = do string_ty <- lookupType stringTyConName
                    return $ HsString s
 
 repOverloadedLiteral :: HsOverLit Name -> DsM (Core TH.Lit)
-repOverloadedLiteral (HsIntegral i _)   = do { lit <- mk_integer  i; repLiteral lit }
-repOverloadedLiteral (HsFractional f _) = do { lit <- mk_rational f; repLiteral lit }
-repOverloadedLiteral (HsIsString s _)   = do { lit <- mk_string   s; repLiteral lit }
+repOverloadedLiteral (HsIntegral i _ _)   = do { lit <- mk_integer  i; repLiteral lit }
+repOverloadedLiteral (HsFractional f _ _) = do { lit <- mk_rational f; repLiteral lit }
+repOverloadedLiteral (HsIsString s _ _)   = do { lit <- mk_string   s; repLiteral lit }
        -- The type Rational will be in the environment, becuase 
        -- the smart constructor 'TH.Syntax.rationalL' uses it in its type,
        -- and rationalL is sucked in when any TH stuff is used