Unbox_free_vars_of_closuresWhen approximations of free variables of closures indicate that they are closures or blocks, rewrite projections from such blocks to new variables (which become free in the closures), with the defining expressions of the projections lifted out of the corresponding sets of closures.
val run : env:Inline_and_simplify_aux.Env.t -> set_of_closures:Flambda.set_of_closures -> (Flambda.expr * Inlining_cost.Benefit.t) option