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Diffstat (limited to '')
| -rw-r--r-- | src/InterpreterBorrows.ml | 37 |
1 files changed, 31 insertions, 6 deletions
diff --git a/src/InterpreterBorrows.ml b/src/InterpreterBorrows.ml index 9331d9f3..034d566a 100644 --- a/src/InterpreterBorrows.ml +++ b/src/InterpreterBorrows.ml @@ -432,14 +432,39 @@ let give_back_value (config : C.config) (bid : V.BorrowId.id) let give_back_symbolic_value (_config : C.config) (proj_regions : T.RegionId.Set.t) (proj_ty : T.rty) (sv : V.symbolic_value) (nsv : V.symbolic_value) (ctx : C.eval_ctx) : C.eval_ctx = - let subst (abs : V.abs) abs_proj_ty = - (* TODO: check that we can consume this symbolic value - this is not - * a precondition, purely a sanity check *) - raise Errors.Unimplemented; + let subst (_abs : V.abs) _abs_proj_ty = + (* Compute the projection over the given back value *) let child_proj = + (* If it is the same symbolic value, it means it was left unchanged: + * we don't have to project it *) if sv.sv_id = nsv.sv_id then None - else - Some (mk_aproj_borrows_from_symbolic_value abs.regions nsv abs_proj_ty) + else ( + (* Not the same symbolic value: it was updated (because given to a + * function or returned) *) + (* For now, we can only have the following case *) + assert (nsv.sv_kind = V.SynthGivenBack); + match nsv.sv_kind with + | V.SynthGivenBack -> + (* The given back value comes from the return value of the function + * we are currently synthesizing (as it is given back, it means + * we ended one of the regions appearing in the signature: we are + * currently synthesizing one of the backward functions *) + (* As we don't allow borrow overwrites on returned value, we can + * (and MUST) forget the borrows *) + None + | V.FunCallGivenBack -> + (* The value was fed as input to a function, and was given back *) + (* For now, we don't allow borrow overwrites on returned values, + * meaning the given back value can't have borrows below mutable + * borrows. *) + let has_borrow_below_mut = + ty_has_borrow_below_mut ctx.type_context.type_infos nsv.sv_ty + in + assert (not has_borrow_below_mut); + (* We don't allow overwrites: we must thus not project over the + * given back value *) + None + | _ -> failwith "Unreachable") in V.AEndedProjLoans child_proj in |