Fix Trac #4003: fix the knot-tying in checkHiBootIface

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

diff --git a/compiler/typecheck/TcRnDriver.lhs b/compiler/typecheck/TcRnDriver.lhs
index 262bd73..649807e 100644 (file)
--- a/compiler/typecheck/TcRnDriver.lhs
+++ b/compiler/typecheck/TcRnDriver.lhs
@@ -566,15 +566,19 @@ checkHiBootIface
 
                -- Check instance declarations
        ; mb_dfun_prs <- mapM check_inst boot_insts
-       ; let tcg_env' = tcg_env { tcg_binds    = binds `unionBags` dfun_binds,
-                                  tcg_type_env = extendTypeEnvWithIds local_type_env boot_dfuns }
-             dfun_prs   = catMaybes mb_dfun_prs
-             boot_dfuns = map fst dfun_prs
-             dfun_binds = listToBag [ mkVarBind boot_dfun (nlHsVar dfun)
-                                    | (boot_dfun, dfun) <- dfun_prs ]
+        ; let dfun_prs   = catMaybes mb_dfun_prs
+              boot_dfuns = map fst dfun_prs
+              dfun_binds = listToBag [ mkVarBind boot_dfun (nlHsVar dfun)
+                                     | (boot_dfun, dfun) <- dfun_prs ]
+              type_env'  = extendTypeEnvWithIds local_type_env boot_dfuns
+              tcg_env'   = tcg_env { tcg_binds = binds `unionBags` dfun_binds }
 
         ; failIfErrsM
-       ; return tcg_env' }
+       ; setGlobalTypeEnv tcg_env' type_env' }
+            -- Update the global type env *including* the knot-tied one
+             -- so that if the source module reads in an interface unfolding
+             -- mentioning one of the dfuns from the boot module, then it
+             -- can "see" that boot dfun.   See Trac #4003
   where
     check_export boot_avail    -- boot_avail is exported by the boot iface
       | name `elem` dfun_names = return ()