(* [decomp_lams_eta env c t] finds the number [n] of products in the type [t],
and decompose the term [c] in [n] lambdas, with eta-expansion if needed. *)
(* [decomp_lams_eta env c t] finds the number [n] of products in the type [t],
and decompose the term [c] in [n] lambdas, with eta-expansion if needed. *)