Fail more informatively when a global isn't in the type environment

diff --git a/compiler/typecheck/TcEnv.lhs b/compiler/typecheck/TcEnv.lhs
index 6799653..fcf41e5 100644 (file)
--- a/compiler/typecheck/TcEnv.lhs
+++ b/compiler/typecheck/TcEnv.lhs
@@ -66,8 +66,7 @@ import InstEnv                ( Instance, DFunId, instanceDFunId, instanceHead )
 import DataCon         ( DataCon )
 import TyCon           ( TyCon )
 import Class           ( Class )
-import Name            ( Name, NamedThing(..), getSrcLoc, nameModule,
-                         nameOccName )
+import Name            ( Name, NamedThing(..), getSrcLoc, nameModule_maybe, nameOccName )
 import PrelNames       ( thFAKE )
 import NameEnv
 import OccName         ( mkDFunOcc, occNameString, mkInstTyTcOcc )
@@ -114,13 +113,15 @@ tcLookupGlobal name
            Nothing    -> do
 
                -- Should it have been in the local envt?
-       { let mod = nameModule name
-       ; if mod == tcg_mod env || mod == thFAKE then
-               notFound name   -- It should be local, so panic
-                               -- The thFAKE possibility is because it
-                               -- might be in a declaration bracket
-         else
-               tcImportDecl name       -- Go find it in an interface
+       { case nameModule_maybe name of
+               Nothing -> notFound name        -- Internal names can happen in GHCi
+
+               Just mod | mod == tcg_mod env   -- Names from this module 
+                        -> notFound name       -- should be in tcg_type_env
+                        | mod == thFAKE        -- Names bound in TH declaration brackets
+                        -> notFound name       -- should be in tcg_env
+                        | otherwise
+                        -> tcImportDecl name   -- Go find it in an interface
        }}}}}
 
 tcLookupField :: Name -> TcM Id                -- Returns the selector Id