+%* *
+ Implicit bindings
+%* *
+%************************************************************************
+
+Note [Injecting implicit bindings]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+We inject the implict bindings right at the end, in CoreTidy.
+Some of these bindings, notably record selectors, are not
+constructed in an optimised form. E.g. record selector for
+ data T = MkT { x :: {-# UNPACK #-} !Int }
+Then the unfolding looks like
+ x = \t. case t of MkT x1 -> let x = I# x1 in x
+This generates bad code unless it's first simplified a bit. That is
+why CoreUnfold.mkImplicitUnfolding uses simleExprOpt to do a bit of
+optimisation first. (Only matters when the selector is used curried;
+eg map x ys.) See Trac #2070.
+
+At one time I tried injecting the implicit bindings *early*, at the
+beginning of SimplCore. But that gave rise to real difficulty,
+becuase GlobalIds are supposed to have *fixed* IdInfo, but the
+simplifier and other core-to-core passes mess with IdInfo all the
+time. The straw that broke the camels back was when a class selector
+got the wrong arity -- ie the simplifier gave it arity 2, whereas
+importing modules were expecting it to have arity 1 (Trac #2844).
+It's much safer just to inject them right at the end, after tidying.
+
+
+\begin{code}
+getImplicitBinds :: TypeEnv -> [CoreBind]
+getImplicitBinds type_env
+ = map get_defn (concatMap implicit_con_ids (typeEnvTyCons type_env)
+ ++ concatMap other_implicit_ids (typeEnvElts type_env))
+ -- Put the constructor wrappers first, because
+ -- other implicit bindings (notably the fromT functions arising
+ -- from generics) use the constructor wrappers. At least that's
+ -- what External Core likes
+ where
+ implicit_con_ids tc = mapCatMaybes dataConWrapId_maybe (tyConDataCons tc)
+
+ other_implicit_ids (ATyCon tc) = filter (not . isNaughtyRecordSelector) (tyConSelIds tc)
+ -- The "naughty" ones are not real functions at all
+ -- They are there just so we can get decent error messages
+ -- See Note [Naughty record selectors] in MkId.lhs
+ other_implicit_ids (AClass cl) = classSelIds cl
+ other_implicit_ids _other = []
+
+ get_defn :: Id -> CoreBind
+ get_defn id = NonRec id (unfoldingTemplate (idUnfolding id))
+\end{code}
+
+
+%************************************************************************