Eliminate over-zealous warning in CoreToStg

[ghc-hetmet.git] / compiler / stgSyn / CoreToStg.lhs

diff --git a/compiler/stgSyn/CoreToStg.lhs b/compiler/stgSyn/CoreToStg.lhs
index ddbc632..91c9a20 100644 (file)
--- a/compiler/stgSyn/CoreToStg.lhs
+++ b/compiler/stgSyn/CoreToStg.lhs
@@ -36,7 +36,7 @@ import Name           ( getOccName, isExternalName, nameOccName )
 import OccName         ( occNameString, occNameFS )
 import BasicTypes       ( Arity )
 import StaticFlags     ( opt_RuntimeTypes )
-import PackageConfig   ( PackageId )
+import Module
 import Outputable
 
 infixr 9 `thenLne`
@@ -563,9 +563,15 @@ coreToStgArgs (arg : args) -- Non-type argument
     let
        arg_ty = exprType arg
        stg_arg_ty = stgArgType stg_arg
+       bad_args = (isUnLiftedType arg_ty && not (isUnLiftedType stg_arg_ty)) 
+               || (typePrimRep arg_ty /= typePrimRep stg_arg_ty)
+       -- In GHCi we coerce an argument of type BCO# (unlifted) to HValue (lifted), 
+       -- and pass it to a function expecting an HValue (arg_ty).  This is ok because
+       -- we can treat an unlifted value as lifted.  But the other way round 
+       -- we complain.
+       -- We also want to check if a pointer is cast to a non-ptr etc
     in
-    WARN( isUnLiftedType arg_ty /= isUnLiftedType stg_arg_ty, 
-         ptext SLIT("Dangerous-looking argument. Probable cause: bad unsafeCoerce#") $$ ppr arg)
+    WARN( bad_args, ptext SLIT("Dangerous-looking argument. Probable cause: bad unsafeCoerce#") $$ ppr arg )
     returnLne (stg_arg : stg_args, fvs)