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51bbdda)
Understanding GHC.Prim.Any is all about understanding the need for
explicit type applications in CoreSyn; the previous example had one
explicit type application but was missing the other, which this patch
adds. It also expands the explanation, based on SPJ's post here:
http://article.gmane.org/gmane.comp.lang.haskell.cvs.ghc/46551
but never enters a function value.
It's also used to instantiate un-constrained type variables after type
but never enters a function value.
It's also used to instantiate un-constrained type variables after type
+ checking. For example, {\tt length} has type
+ {\tt length :: forall a. [a] -> Int}
+
+ and the list datacon for the empty list has type
+
+ {\tt [] :: forall a. [a]}
+
+ In order to compose these two terms as {\tt length []} a type
+ application is required, but there is no constraint on the
+ choice. In this situation GHC uses {\tt Any}:
+
+ {\tt length Any ([] Any)}
Annoyingly, we sometimes need {\tt Any}s of other kinds, such as {\tt (* -> *)} etc.
This is a bit like tuples. We define a couple of useful ones here,
Annoyingly, we sometimes need {\tt Any}s of other kinds, such as {\tt (* -> *)} etc.
This is a bit like tuples. We define a couple of useful ones here,