summaryrefslogtreecommitdiff
path: root/src/Invariants.ml
blob: 05373d1b2f711fca7a3c150e7e4bfb1e2b2d068e (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
(* The following module defines functions to check that some invariants
 * are always maintained by evaluation contexts *)

module T = Types
module V = Values
module E = Expressions
module C = Contexts
module Subst = Substitute
module A = CfimAst
module L = Logging
open InterpreterUtils
open InterpreterBorrowsCore

let debug_invariants : bool ref = ref false

type borrow_info = {
  loan_kind : T.ref_kind;
  loan_in_abs : bool;
  (* true if the loan was found in an abstraction *)
  loan_ids : V.BorrowId.set_t;
  borrow_ids : V.BorrowId.set_t;
}
[@@deriving show]

type outer_borrow_info = {
  outer_borrow : bool;
  (* true if the value is borrowed *)
  outer_shared : bool; (* true if the value is borrowed as shared *)
}

let set_outer_mut (info : outer_borrow_info) : outer_borrow_info =
  { info with outer_borrow = true }

let set_outer_shared (_info : outer_borrow_info) : outer_borrow_info =
  { outer_borrow = true; outer_shared = true }

let borrows_infos_to_string (infos : borrow_info V.BorrowId.Map.t) : string =
  let bindings = V.BorrowId.Map.bindings infos in
  let bindings = List.map (fun (_, info) -> show_borrow_info info) bindings in
  String.concat "\n" bindings

type borrow_kind = Mut | Shared | Inactivated

(** Check that:
    - loans and borrows are correctly related
    - a two-phase borrow can't point to a value inside an abstraction
 *)
let check_loans_borrows_relation_invariant (ctx : C.eval_ctx) : unit =
  (* Link all the borrow ids to a representant - necessary because of shared
   * borrows/loans *)
  let ids_reprs : V.BorrowId.id V.BorrowId.Map.t ref =
    ref V.BorrowId.Map.empty
  in
  (* Link all the id representants to a borrow information *)
  let borrows_infos : borrow_info V.BorrowId.Map.t ref =
    ref V.BorrowId.Map.empty
  in

  (* First, register all the loans *)
  (* Some utilities to register the loans *)
  let register_shared_loan (loan_in_abs : bool) (bids : V.BorrowId.set_t) : unit
      =
    let reprs = !ids_reprs in
    let infos = !borrows_infos in
    (* Use the first borrow id as representant *)
    let repr_bid = V.BorrowId.Set.min_elt bids in
    assert (not (V.BorrowId.Map.mem repr_bid infos));
    (* Insert the mappings to the representant *)
    let reprs =
      V.BorrowId.Set.fold
        (fun bid reprs ->
          assert (not (V.BorrowId.Map.mem bid reprs));
          V.BorrowId.Map.add bid repr_bid reprs)
        bids reprs
    in
    (* Insert the loan info *)
    let info =
      {
        loan_kind = T.Shared;
        loan_in_abs;
        loan_ids = bids;
        borrow_ids = V.BorrowId.Set.empty;
      }
    in
    let infos = V.BorrowId.Map.add repr_bid info infos in
    (* Update *)
    ids_reprs := reprs;
    borrows_infos := infos
  in

  let register_mut_loan (loan_in_abs : bool) (bid : V.BorrowId.id) : unit =
    let reprs = !ids_reprs in
    let infos = !borrows_infos in
    (* Sanity checks *)
    assert (not (V.BorrowId.Map.mem bid reprs));
    assert (not (V.BorrowId.Map.mem bid infos));
    (* Add the mapping for the representant *)
    let reprs = V.BorrowId.Map.add bid bid reprs in
    (* Add the mapping for the loan info *)
    let info =
      {
        loan_kind = T.Mut;
        loan_in_abs;
        loan_ids = V.BorrowId.Set.singleton bid;
        borrow_ids = V.BorrowId.Set.empty;
      }
    in
    let infos = V.BorrowId.Map.add bid info infos in
    (* Update *)
    ids_reprs := reprs;
    borrows_infos := infos
  in

  let loans_visitor =
    object
      inherit [_] C.iter_eval_ctx as super

      method! visit_Var _ binder v =
        let inside_abs = false in
        super#visit_Var inside_abs binder v

      method! visit_Abs _ abs =
        let inside_abs = true in
        super#visit_Abs inside_abs abs

      method! visit_loan_content inside_abs lc =
        (* Register the loan *)
        let _ =
          match lc with
          | V.SharedLoan (bids, _) -> register_shared_loan inside_abs bids
          | V.MutLoan bid -> register_mut_loan inside_abs bid
        in
        (* Continue exploring *)
        super#visit_loan_content inside_abs lc

      method! visit_aloan_content inside_abs lc =
        let _ =
          match lc with
          | V.AMutLoan (bid, _) -> register_mut_loan inside_abs bid
          | V.ASharedLoan (bids, _, _) -> register_shared_loan inside_abs bids
          | V.AEndedMutLoan { given_back = _; child = _ }
          | V.AEndedSharedLoan (_, _)
          | V.AIgnoredMutLoan (_, _) (* We might want to do something here *)
          | V.AEndedIgnoredMutLoan { given_back = _; child = _ }
          | V.AIgnoredSharedLoan _ ->
              (* Do nothing *)
              ()
        in
        (* Continue exploring *)
        super#visit_aloan_content inside_abs lc
    end
  in

  (* Visit *)
  let inside_abs = false in
  loans_visitor#visit_eval_ctx inside_abs ctx;

  (* Then, register all the borrows *)
  (* Some utilities to register the borrows *)
  let find_info (bid : V.BorrowId.id) : borrow_info =
    (* Find the representant *)
    let repr_bid = V.BorrowId.Map.find bid !ids_reprs in
    (* Lookup the info *)
    V.BorrowId.Map.find repr_bid !borrows_infos
  in
  let update_info (bid : V.BorrowId.id) (info : borrow_info) : unit =
    (* Find the representant *)
    let repr_bid = V.BorrowId.Map.find bid !ids_reprs in
    (* Update the info *)
    let infos =
      V.BorrowId.Map.update repr_bid
        (fun x ->
          match x with Some _ -> Some info | None -> failwith "Unreachable")
        !borrows_infos
    in
    borrows_infos := infos
  in

  let register_borrow (kind : borrow_kind) (bid : V.BorrowId.id) : unit =
    (* Lookup the info *)
    let info = find_info bid in
    (* Check that the borrow kind is consistent *)
    (match (info.loan_kind, kind) with
    | T.Shared, (Shared | Inactivated) | T.Mut, Mut -> ()
    | _ -> failwith "Invariant not satisfied");
    (* An inactivated borrow can't point to a value inside an abstraction *)
    assert (kind <> Inactivated || not info.loan_in_abs);
    (* Insert the borrow id *)
    let borrow_ids = info.borrow_ids in
    assert (not (V.BorrowId.Set.mem bid borrow_ids));
    let info = { info with borrow_ids = V.BorrowId.Set.add bid borrow_ids } in
    (* Update the info in the map *)
    update_info bid info
  in

  let borrows_visitor =
    object
      inherit [_] C.iter_eval_ctx as super

      method! visit_abstract_shared_borrows _ asb =
        let visit asb =
          match asb with
          | V.AsbBorrow bid -> register_borrow Shared bid
          | V.AsbProjReborrows _ -> ()
        in
        List.iter visit asb

      method! visit_borrow_content env bc =
        (* Register the loan *)
        let _ =
          match bc with
          | V.SharedBorrow bid -> register_borrow Shared bid
          | V.MutBorrow (bid, _) -> register_borrow Mut bid
          | V.InactivatedMutBorrow bid -> register_borrow Inactivated bid
        in
        (* Continue exploring *)
        super#visit_borrow_content env bc

      method! visit_aborrow_content env bc =
        let _ =
          match bc with
          | V.AMutBorrow (bid, _) -> register_borrow Mut bid
          | V.ASharedBorrow bid -> register_borrow Shared bid
          | V.AIgnoredMutBorrow _ | V.AProjSharedBorrow _ ->
              (* Do nothing *)
              ()
        in
        (* Continue exploring *)
        super#visit_aborrow_content env bc
    end
  in

  (* Visit *)
  borrows_visitor#visit_eval_ctx () ctx;

  (* Debugging *)
  if !debug_invariants then (
    L.log#ldebug
      (lazy
        ("\nAbout to check context invariant:\n" ^ eval_ctx_to_string ctx ^ "\n"));
    L.log#ldebug
      (lazy
        ("\nBorrows information:\n"
        ^ borrows_infos_to_string !borrows_infos
        ^ "\n")));

  (* Finally, check that everything is consistant *)
  V.BorrowId.Map.iter
    (fun _ info ->
      (* Note that we can't directly compare the sets - I guess they are
       * different depending on the order in which we add the elements... *)
      assert (
        V.BorrowId.Set.elements info.loan_ids
        = V.BorrowId.Set.elements info.borrow_ids);
      match info.loan_kind with
      | T.Mut -> assert (V.BorrowId.Set.cardinal info.loan_ids = 1)
      | T.Shared -> ())
    !borrows_infos

(** Check that:
    - borrows/loans can't contain ⊥ or inactivated mut borrows
    - shared loans can't contain mutable loans
 *)
let check_borrowed_values_invariant (ctx : C.eval_ctx) : unit =
  let visitor =
    object
      inherit [_] C.iter_eval_ctx as super

      method! visit_Bottom info =
        (* No ⊥ inside borrowed values *)
        assert (not info.outer_borrow)

      method! visit_ABottom _info =
        (* ⊥ inside an abstraction is not the same as in a regular value *)
        ()

      method! visit_loan_content info lc =
        (* Update the info *)
        let info =
          match lc with
          | V.SharedLoan (_, _) -> set_outer_shared info
          | V.MutLoan _ ->
              (* No mutable loan inside a shared loan *)
              assert (not info.outer_shared);
              set_outer_mut info
        in
        (* Continue exploring *)
        super#visit_loan_content info lc

      method! visit_borrow_content info bc =
        (* Update the info *)
        let info =
          match bc with
          | V.SharedBorrow _ -> set_outer_shared info
          | V.InactivatedMutBorrow _ ->
              assert (not info.outer_borrow);
              set_outer_shared info
          | V.MutBorrow (_, _) -> set_outer_mut info
        in
        (* Continue exploring *)
        super#visit_borrow_content info bc

      method! visit_aloan_content info lc =
        (* Update the info *)
        let info =
          match lc with
          | V.AMutLoan (_, _) -> set_outer_mut info
          | V.ASharedLoan (_, _, _) -> set_outer_shared info
          | V.AEndedMutLoan { given_back = _; child = _ } -> set_outer_mut info
          | V.AEndedSharedLoan (_, _) -> set_outer_shared info
          | V.AIgnoredMutLoan (_, _) -> set_outer_mut info
          | V.AEndedIgnoredMutLoan { given_back = _; child = _ } ->
              set_outer_mut info
          | V.AIgnoredSharedLoan _ -> set_outer_shared info
        in
        (* Continue exploring *)
        super#visit_aloan_content info lc

      method! visit_aborrow_content info bc =
        (* Update the info *)
        let info =
          match bc with
          | V.AMutBorrow (_, _) -> set_outer_mut info
          | V.ASharedBorrow _ -> set_outer_shared info
          | V.AIgnoredMutBorrow _ -> set_outer_mut info
          | V.AProjSharedBorrow _ -> set_outer_shared info
        in
        (* Continue exploring *)
        super#visit_aborrow_content info bc
    end
  in

  (* Explore *)
  let info = { outer_borrow = false; outer_shared = false } in
  visitor#visit_eval_ctx info ctx

let check_constant_value_type (cv : V.constant_value) (ty : T.ety) : unit =
  match (cv, ty) with
  | V.Scalar sv, T.Integer int_ty -> assert (sv.int_ty = int_ty)
  | V.Bool _, T.Bool | V.Char _, T.Char | V.String _, T.Str -> ()
  | _ -> failwith "Erroneous typing"

let check_typing_invariant (ctx : C.eval_ctx) : unit =
  let visitor =
    object
      inherit [_] C.iter_eval_ctx as super

      method! visit_typed_value info tv =
        (* Check the current pair (value, type) *)
        (match (tv.V.value, tv.V.ty) with
        | V.Concrete cv, ty -> check_constant_value_type cv ty
        (* ADT case *)
        | V.Adt av, T.Adt (T.AdtId def_id, regions, tys) ->
            (* Retrieve the definition to check the variant id, the number of
             * parameters, etc. *)
            let def = C.ctx_lookup_type_def ctx def_id in
            (* Check the number of parameters *)
            assert (List.length regions = List.length def.region_params);
            assert (List.length tys = List.length def.type_params);
            (* Check that the variant id is consistent *)
            (match (av.V.variant_id, def.T.kind) with
            | Some variant_id, T.Enum variants ->
                assert (T.VariantId.to_int variant_id < List.length variants)
            | None, T.Struct _ -> ()
            | _ -> failwith "Erroneous typing");
            (* Check that the field types are correct *)
            let field_types =
              Subst.type_def_get_instantiated_field_etypes def av.V.variant_id
                tys
            in
            let fields_with_types =
              List.combine av.V.field_values field_types
            in
            List.iter
              (fun ((v, ty) : V.typed_value * T.ety) -> assert (v.V.ty = ty))
              fields_with_types
        (* Tuple case *)
        | V.Adt av, T.Adt (T.Tuple, regions, tys) ->
            assert (regions = []);
            assert (av.V.variant_id = None);
            (* Check that the fields have the proper values - and check that there
             * are as many fields as field types at the same time *)
            let fields_with_types = List.combine av.V.field_values tys in
            List.iter
              (fun ((v, ty) : V.typed_value * T.ety) -> assert (v.V.ty = ty))
              fields_with_types
        (* Assumed type case *)
        | V.Adt av, T.Adt (T.Assumed aty_id, regions, tys) -> (
            assert (av.V.variant_id = None);
            match (aty_id, av.V.field_values, regions, tys) with
            (* Box *)
            | T.Box, [ boxed_value ], [], [ boxed_ty ] ->
                assert (boxed_value.V.ty = boxed_ty)
            | _ -> failwith "Erroneous type")
        | V.Bottom, _ -> (* Nothing to check *) ()
        | V.Borrow bc, T.Ref (_, ref_ty, rkind) -> (
            match (bc, rkind) with
            | V.SharedBorrow bid, T.Shared | V.InactivatedMutBorrow bid, T.Mut
              -> (
                (* Lookup the borrowed value to check it has the proper type *)
                let _, glc = lookup_loan ek_all bid ctx in
                match glc with
                | Concrete (V.SharedLoan (_, sv))
                | Abstract (V.ASharedLoan (_, sv, _)) ->
                    assert (sv.V.ty = ref_ty)
                | _ -> failwith "Inconsistent context")
            | V.MutBorrow (_, bv), T.Mut ->
                assert (
                  (* Check that the borrowed value has the proper type *)
                  bv.V.ty = ref_ty)
            | _ -> failwith "Erroneous typing")
        | V.Loan lc, ty -> (
            match lc with
            | V.SharedLoan (_, sv) -> assert (sv.V.ty = ty)
            | V.MutLoan bid -> (
                (* Lookup the borrowed value to check it has the proper type *)
                let glc = lookup_borrow ek_all bid ctx in
                match glc with
                | Concrete (V.MutBorrow (_, bv)) -> assert (bv.V.ty = ty)
                | Abstract (V.AMutBorrow (_, sv)) ->
                    assert (Subst.erase_regions sv.V.ty = ty)
                | _ -> failwith "Inconsistent context"))
        | V.Symbolic spc, ty ->
            let ty' = Subst.erase_regions spc.V.svalue.V.sv_ty in
            assert (ty' = ty)
        | _ -> failwith "Erroneous typing");
        (* Continue exploring to inspect the subterms *)
        super#visit_typed_value info tv

      method! visit_typed_avalue info atv =
        (* Check the current pair (value, type) *)
        (match (atv.V.value, atv.V.ty) with
        | V.AConcrete cv, ty ->
            check_constant_value_type cv (Subst.erase_regions ty)
        (* ADT case *)
        | V.AAdt av, T.Adt (T.AdtId def_id, regions, tys) ->
            (* Retrieve the definition to check the variant id, the number of
             * parameters, etc. *)
            let def = C.ctx_lookup_type_def ctx def_id in
            (* Check the number of parameters *)
            assert (List.length regions = List.length def.region_params);
            assert (List.length tys = List.length def.type_params);
            (* Check that the variant id is consistent *)
            (match (av.V.variant_id, def.T.kind) with
            | Some variant_id, T.Enum variants ->
                assert (T.VariantId.to_int variant_id < List.length variants)
            | None, T.Struct _ -> ()
            | _ -> failwith "Erroneous typing");
            (* Check that the field types are correct *)
            let field_types =
              Subst.type_def_get_instantiated_field_rtypes def av.V.variant_id
                regions tys
            in
            let fields_with_types =
              List.combine av.V.field_values field_types
            in
            List.iter
              (fun ((v, ty) : V.typed_avalue * T.rty) -> assert (v.V.ty = ty))
              fields_with_types
        (* Tuple case *)
        | V.AAdt av, T.Adt (T.Tuple, regions, tys) ->
            assert (regions = []);
            assert (av.V.variant_id = None);
            (* Check that the fields have the proper values - and check that there
             * are as many fields as field types at the same time *)
            let fields_with_types = List.combine av.V.field_values tys in
            List.iter
              (fun ((v, ty) : V.typed_avalue * T.rty) -> assert (v.V.ty = ty))
              fields_with_types
        (* Assumed type case *)
        | V.AAdt av, T.Adt (T.Assumed aty_id, regions, tys) -> (
            assert (av.V.variant_id = None);
            match (aty_id, av.V.field_values, regions, tys) with
            (* Box *)
            | T.Box, [ boxed_value ], [], [ boxed_ty ] ->
                assert (boxed_value.V.ty = boxed_ty)
            | _ -> failwith "Erroneous type")
        | V.ABottom, _ -> (* Nothing to check *) ()
        | V.ABorrow bc, T.Ref (_, ref_ty, rkind) -> (
            match (bc, rkind) with
            | V.AMutBorrow (_, av), T.Mut ->
                (* Check that the child value has the proper type *)
                assert (av.V.ty = ref_ty)
            | V.ASharedBorrow bid, T.Shared -> (
                (* Lookup the borrowed value to check it has the proper type *)
                let _, glc = lookup_loan ek_all bid ctx in
                match glc with
                | Concrete (V.SharedLoan (_, sv))
                | Abstract (V.ASharedLoan (_, sv, _)) ->
                    assert (sv.V.ty = Subst.erase_regions ref_ty)
                | _ -> failwith "Inconsistent context")
            | V.AIgnoredMutBorrow av, T.Mut -> assert (av.V.ty = ref_ty)
            | V.AProjSharedBorrow _, T.Shared -> ()
            | _ -> failwith "Inconsistent context")
        | V.ALoan lc, aty -> (
            match lc with
            | V.AMutLoan (bid, child_av) | V.AIgnoredMutLoan (bid, child_av)
              -> (
                assert (child_av.V.ty = aty);
                (* Lookup the borrowed value to check it has the proper type *)
                let glc = lookup_borrow ek_all bid ctx in
                match glc with
                | Concrete (V.MutBorrow (_, bv)) ->
                    assert (bv.V.ty = Subst.erase_regions aty)
                | Abstract (V.AMutBorrow (_, sv)) ->
                    assert (
                      Subst.erase_regions sv.V.ty = Subst.erase_regions aty)
                | _ -> failwith "Inconsistent context")
            | V.ASharedLoan (_, sv, child_av) | V.AEndedSharedLoan (sv, child_av)
              ->
                let ty = Subst.erase_regions aty in
                assert (sv.V.ty = ty);
                assert (child_av.V.ty = aty)
            | V.AEndedMutLoan { given_back; child }
            | V.AEndedIgnoredMutLoan { given_back; child } ->
                assert (given_back.V.ty = aty);
                assert (child.V.ty = aty)
            | V.AIgnoredSharedLoan child_av -> assert (child_av.V.ty = aty))
        | V.ASymbolic aproj, ty ->
            let ty1 = Subst.erase_regions ty in
            let ty2 =
              match aproj with
              | V.AProjLoans sv | V.AProjBorrows (sv, _) ->
                  Subst.erase_regions sv.V.sv_ty
            in
            assert (ty1 = ty2)
        | _ -> failwith "Erroneous typing");
        (* Continue exploring to inspect the subterms *)
        super#visit_typed_avalue info atv
      (** TODO: there is a lot of duplication with [visit_typed_value]... *)
    end
  in
  visitor#visit_eval_ctx () ctx

let check_invariants (ctx : C.eval_ctx) : unit =
  check_loans_borrows_relation_invariant ctx;
  check_borrowed_values_invariant ctx;
  check_typing_invariant ctx