Add the primitive type Any, and use it for Dynamics

GHC's code generator can only enter a closure if it's guaranteed
not to be a function.  In the Dynamic module, we were using the 
type (forall a.a) as the type to which the dynamic type was unsafely
cast:
	type Obj = forall a.a

Gut alas this polytype was sometimes instantiated to (), something 
like this (it only bit when profiling was enabled)
	let y::() = dyn ()
	in (y `cast` ..) p q
As a result, an ASSERT in ClosureInfo fired (hooray).

I've tided this up by making a new, primitive, lifted type Any, and
arranging that Dynamic uses Any, thus:
	type Obj = ANy

While I was at it, I also arranged that when the type checker instantiates 
un-constrained type variables, it now instantiates them to Any, not ()
	e.g.  length Any []

[There remains a Horrible Hack when we want Any-like things at arbitrary 
kinds.  This essentially never happens, but see comments with 
TysPrim.mkAnyPrimTyCon.]

Anyway, this fixes Trac #905

1 files changed, 5 insertions, 5 deletions

diff --git a/compiler/codeGen/ClosureInfo.lhs b/compiler/codeGen/ClosureInfo.lhs
index 8f62bc7e0e..e6319898db 100644
--- a/compiler/codeGen/ClosureInfo.lhs
+++ b/compiler/codeGen/ClosureInfo.lhs
@@ -257,12 +257,12 @@ mkLFThunk thunk_ty top fvs upd_flag
 	    (might_be_a_function thunk_ty)
 
 might_be_a_function :: Type -> Bool
+-- Return False only if we are *sure* it's a data type
+-- Look through newtypes etc as much as poss
 might_be_a_function ty
-  | Just (tc,_) <- splitTyConApp_maybe (repType ty), 
-    not (isFunTyCon tc)  && not (isAbstractTyCon tc) = False
-	-- don't forget to check for abstract types, which might
-	-- be functions too.
-  | otherwise = True
+  = case splitTyConApp_maybe (repType ty) of
+	Just (tc, _) -> not (isDataTyCon tc)
+	Nothing	     -> True
 \end{code}
 
 @mkConLFInfo@ is similar, for constructors.