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Simon Peyton Jones authored
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
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