Extract_projectionsIdentify projections from variables used in function bodies (free variables or specialised args, for example, according to which_variables below). Projections from variables that are also used boxed are not returned.
val from_function_decl : env:Inline_and_simplify_aux.Env.t -> which_variables:Flambda.specialised_to Variable.Map.t -> function_decl:Flambda.function_declaration -> Projection.Set.twhich_variables maps (existing) inner variables to (existing) outer variables in the manner of free_vars and specialised_args in Flambda.set_of_closures.
The returned projections are projecting_from (cf. projection.mli) the "existing inner vars".