Fix scoped type variables for expression type signatures

[ghc-hetmet.git] / compiler / typecheck / TcMType.lhs

diff --git a/compiler/typecheck/TcMType.lhs b/compiler/typecheck/TcMType.lhs
index 4542a34..f01d69d 100644 (file)
--- a/compiler/typecheck/TcMType.lhs
+++ b/compiler/typecheck/TcMType.lhs
@@ -107,6 +107,7 @@ import Outputable
 
 import Control.Monad   ( when )
 import Data.List       ( (\\) )
+
 \end{code}
 
 
@@ -367,7 +368,8 @@ data LookupTyVarResult      -- The result of a lookupTcTyVar call
 
 lookupTcTyVar :: TcTyVar -> TcM LookupTyVarResult
 lookupTcTyVar tyvar 
-  = case details of
+  = ASSERT( isTcTyVar tyvar )
+    case details of
       SkolemTv _   -> return (DoneTv details)
       MetaTv _ ref -> do { meta_details <- readMutVar ref
                         ; case meta_details of