let pop where c0 =
Wp_parameters.debug ~level:3 "POPK %d: %S@." (pred (List.length !context)) where ;
match !context with
| [] -> Wp_parameters.fatal "No context for constrained term"
| c::stack ->
if not (c0 == c)
then Wp_parameters.fatal "Context mismatch for constrained term" ;
context := stack ;
c.bindings