magnify ::
    forall outertag innertag t outer inner m a.
    ( forall x. Coercible (t m x) (m x)
    , forall m'.
      (HasReader outertag outer m') =>
      HasReader innertag inner (t m')
    , HasReader outertag outer m
    ) =>
    (forall m'. (HasReader innertag inner m') => m' a) ->
    m a