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
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

// Type resolution: the phase that finds all the types in the AST with
// unresolved type variables and replaces "ty_var" types with their
// substitutions.

use check::FnCtxt;
use rustc::hir;
use rustc::hir::def_id::{DefId, DefIndex};
use rustc::hir::intravisit::{self, NestedVisitorMap, Visitor};
use rustc::infer::InferCtxt;
use rustc::ty::adjustment::{Adjust, Adjustment};
use rustc::ty::fold::{BottomUpFolder, TypeFoldable, TypeFolder};
use rustc::ty::subst::UnpackedKind;
use rustc::ty::{self, Ty, TyCtxt};
use rustc::util::nodemap::DefIdSet;
use rustc_data_structures::sync::Lrc;
use std::mem;
use syntax::ast;
use syntax_pos::Span;

///////////////////////////////////////////////////////////////////////////
// Entry point

impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
    pub fn resolve_type_vars_in_body(&self, body: &'gcx hir::Body) -> &'gcx ty::TypeckTables<'gcx> {
        let item_id = self.tcx.hir.body_owner(body.id());
        let item_def_id = self.tcx.hir.local_def_id(item_id);

        // This attribute causes us to dump some writeback information
        // in the form of errors, which is used for unit tests.
        let rustc_dump_user_substs = self.tcx.has_attr(item_def_id, "rustc_dump_user_substs");

        let mut wbcx = WritebackCx::new(self, body, rustc_dump_user_substs);
        for arg in &body.arguments {
            wbcx.visit_node_id(arg.pat.span, arg.hir_id);
        }
        wbcx.visit_body(body);
        wbcx.visit_upvar_borrow_map();
        wbcx.visit_closures();
        wbcx.visit_liberated_fn_sigs();
        wbcx.visit_fru_field_types();
        wbcx.visit_opaque_types(body.value.span);
        wbcx.visit_cast_types();
        wbcx.visit_free_region_map();
        wbcx.visit_user_provided_tys();

        let used_trait_imports = mem::replace(
            &mut self.tables.borrow_mut().used_trait_imports,
            Lrc::new(DefIdSet()),
        );
        debug!(
            "used_trait_imports({:?}) = {:?}",
            item_def_id, used_trait_imports
        );
        wbcx.tables.used_trait_imports = used_trait_imports;

        wbcx.tables.tainted_by_errors = self.is_tainted_by_errors();

        debug!(
            "writeback: tables for {:?} are {:#?}",
            item_def_id, wbcx.tables
        );

        self.tcx.alloc_tables(wbcx.tables)
    }
}

///////////////////////////////////////////////////////////////////////////
// The Writerback context. This visitor walks the AST, checking the
// fn-specific tables to find references to types or regions. It
// resolves those regions to remove inference variables and writes the
// final result back into the master tables in the tcx. Here and
// there, it applies a few ad-hoc checks that were not convenient to
// do elsewhere.

struct WritebackCx<'cx, 'gcx: 'cx + 'tcx, 'tcx: 'cx> {
    fcx: &'cx FnCtxt<'cx, 'gcx, 'tcx>,

    tables: ty::TypeckTables<'gcx>,

    body: &'gcx hir::Body,

    rustc_dump_user_substs: bool,
}

impl<'cx, 'gcx, 'tcx> WritebackCx<'cx, 'gcx, 'tcx> {
    fn new(
        fcx: &'cx FnCtxt<'cx, 'gcx, 'tcx>,
        body: &'gcx hir::Body,
        rustc_dump_user_substs: bool,
    ) -> WritebackCx<'cx, 'gcx, 'tcx> {
        let owner = fcx.tcx.hir.definitions().node_to_hir_id(body.id().node_id);

        WritebackCx {
            fcx,
            tables: ty::TypeckTables::empty(Some(DefId::local(owner.owner))),
            body,
            rustc_dump_user_substs,
        }
    }

    fn tcx(&self) -> TyCtxt<'cx, 'gcx, 'tcx> {
        self.fcx.tcx
    }

    fn write_ty_to_tables(&mut self, hir_id: hir::HirId, ty: Ty<'gcx>) {
        debug!("write_ty_to_tables({:?}, {:?})", hir_id, ty);
        assert!(!ty.needs_infer() && !ty.has_skol());
        self.tables.node_types_mut().insert(hir_id, ty);
    }

    // Hacky hack: During type-checking, we treat *all* operators
    // as potentially overloaded. But then, during writeback, if
    // we observe that something like `a+b` is (known to be)
    // operating on scalars, we clear the overload.
    fn fix_scalar_builtin_expr(&mut self, e: &hir::Expr) {
        match e.node {
            hir::ExprKind::Unary(hir::UnNeg, ref inner)
            | hir::ExprKind::Unary(hir::UnNot, ref inner) => {
                let inner_ty = self.fcx.node_ty(inner.hir_id);
                let inner_ty = self.fcx.resolve_type_vars_if_possible(&inner_ty);

                if inner_ty.is_scalar() {
                    let mut tables = self.fcx.tables.borrow_mut();
                    tables.type_dependent_defs_mut().remove(e.hir_id);
                    tables.node_substs_mut().remove(e.hir_id);
                }
            }
            hir::ExprKind::Binary(ref op, ref lhs, ref rhs)
            | hir::ExprKind::AssignOp(ref op, ref lhs, ref rhs) => {
                let lhs_ty = self.fcx.node_ty(lhs.hir_id);
                let lhs_ty = self.fcx.resolve_type_vars_if_possible(&lhs_ty);

                let rhs_ty = self.fcx.node_ty(rhs.hir_id);
                let rhs_ty = self.fcx.resolve_type_vars_if_possible(&rhs_ty);

                if lhs_ty.is_scalar() && rhs_ty.is_scalar() {
                    let mut tables = self.fcx.tables.borrow_mut();
                    tables.type_dependent_defs_mut().remove(e.hir_id);
                    tables.node_substs_mut().remove(e.hir_id);

                    match e.node {
                        hir::ExprKind::Binary(..) => {
                            if !op.node.is_by_value() {
                                let mut adjustments = tables.adjustments_mut();
                                adjustments.get_mut(lhs.hir_id).map(|a| a.pop());
                                adjustments.get_mut(rhs.hir_id).map(|a| a.pop());
                            }
                        }
                        hir::ExprKind::AssignOp(..) => {
                            tables
                                .adjustments_mut()
                                .get_mut(lhs.hir_id)
                                .map(|a| a.pop());
                        }
                        _ => {}
                    }
                }
            }
            _ => {}
        }
    }

    // Similar to operators, indexing is always assumed to be overloaded
    // Here, correct cases where an indexing expression can be simplified
    // to use builtin indexing because the index type is known to be
    // usize-ish
    fn fix_index_builtin_expr(&mut self, e: &hir::Expr) {
        if let hir::ExprKind::Index(ref base, ref index) = e.node {
            let mut tables = self.fcx.tables.borrow_mut();

            match tables.expr_ty_adjusted(&base).sty {
                // All valid indexing looks like this
                ty::Ref(_, base_ty, _) => {
                    let index_ty = tables.expr_ty_adjusted(&index);
                    let index_ty = self.fcx.resolve_type_vars_if_possible(&index_ty);

                    if base_ty.builtin_index().is_some() && index_ty == self.fcx.tcx.types.usize {
                        // Remove the method call record
                        tables.type_dependent_defs_mut().remove(e.hir_id);
                        tables.node_substs_mut().remove(e.hir_id);

                        tables.adjustments_mut().get_mut(base.hir_id).map(|a| {
                            // Discard the need for a mutable borrow
                            match a.pop() {
                                // Extra adjustment made when indexing causes a drop
                                // of size information - we need to get rid of it
                                // Since this is "after" the other adjustment to be
                                // discarded, we do an extra `pop()`
                                Some(Adjustment {
                                    kind: Adjust::Unsize,
                                    ..
                                }) => {
                                    // So the borrow discard actually happens here
                                    a.pop();
                                }
                                _ => {}
                            }
                        });
                    }
                }
                // Might encounter non-valid indexes at this point, so there
                // has to be a fall-through
                _ => {}
            }
        }
    }
}

///////////////////////////////////////////////////////////////////////////
// Impl of Visitor for Resolver
//
// This is the master code which walks the AST. It delegates most of
// the heavy lifting to the generic visit and resolve functions
// below. In general, a function is made into a `visitor` if it must
// traffic in node-ids or update tables in the type context etc.

impl<'cx, 'gcx, 'tcx> Visitor<'gcx> for WritebackCx<'cx, 'gcx, 'tcx> {
    fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'gcx> {
        NestedVisitorMap::None
    }

    fn visit_expr(&mut self, e: &'gcx hir::Expr) {
        self.fix_scalar_builtin_expr(e);
        self.fix_index_builtin_expr(e);

        self.visit_node_id(e.span, e.hir_id);

        match e.node {
            hir::ExprKind::Closure(_, _, body, _, _) => {
                let body = self.fcx.tcx.hir.body(body);
                for arg in &body.arguments {
                    self.visit_node_id(e.span, arg.hir_id);
                }

                self.visit_body(body);
            }
            hir::ExprKind::Struct(_, ref fields, _) => {
                for field in fields {
                    self.visit_field_id(field.id);
                }
            }
            hir::ExprKind::Field(..) => {
                self.visit_field_id(e.id);
            }
            _ => {}
        }

        intravisit::walk_expr(self, e);
    }

    fn visit_block(&mut self, b: &'gcx hir::Block) {
        self.visit_node_id(b.span, b.hir_id);
        intravisit::walk_block(self, b);
    }

    fn visit_pat(&mut self, p: &'gcx hir::Pat) {
        match p.node {
            hir::PatKind::Binding(..) => {
                if let Some(&bm) = self.fcx.tables.borrow().pat_binding_modes().get(p.hir_id) {
                    self.tables.pat_binding_modes_mut().insert(p.hir_id, bm);
                } else {
                    self.tcx()
                        .sess
                        .delay_span_bug(p.span, "missing binding mode");
                }
            }
            hir::PatKind::Struct(_, ref fields, _) => {
                for field in fields {
                    self.visit_field_id(field.node.id);
                }
            }
            _ => {}
        };

        self.visit_pat_adjustments(p.span, p.hir_id);

        self.visit_node_id(p.span, p.hir_id);
        intravisit::walk_pat(self, p);
    }

    fn visit_local(&mut self, l: &'gcx hir::Local) {
        intravisit::walk_local(self, l);
        let var_ty = self.fcx.local_ty(l.span, l.id);
        let var_ty = self.resolve(&var_ty, &l.span);
        self.write_ty_to_tables(l.hir_id, var_ty);
    }

    fn visit_ty(&mut self, hir_ty: &'gcx hir::Ty) {
        intravisit::walk_ty(self, hir_ty);
        let ty = self.fcx.node_ty(hir_ty.hir_id);
        let ty = self.resolve(&ty, &hir_ty.span);
        self.write_ty_to_tables(hir_ty.hir_id, ty);
    }
}

impl<'cx, 'gcx, 'tcx> WritebackCx<'cx, 'gcx, 'tcx> {
    fn visit_upvar_borrow_map(&mut self) {
        for (upvar_id, upvar_capture) in self.fcx.tables.borrow().upvar_capture_map.iter() {
            let new_upvar_capture = match *upvar_capture {
                ty::UpvarCapture::ByValue => ty::UpvarCapture::ByValue,
                ty::UpvarCapture::ByRef(ref upvar_borrow) => {
                    let r = upvar_borrow.region;
                    let r = self.resolve(&r, &upvar_id.var_id);
                    ty::UpvarCapture::ByRef(ty::UpvarBorrow {
                        kind: upvar_borrow.kind,
                        region: r,
                    })
                }
            };
            debug!(
                "Upvar capture for {:?} resolved to {:?}",
                upvar_id, new_upvar_capture
            );
            self.tables
                .upvar_capture_map
                .insert(*upvar_id, new_upvar_capture);
        }
    }

    fn visit_closures(&mut self) {
        let fcx_tables = self.fcx.tables.borrow();
        debug_assert_eq!(fcx_tables.local_id_root, self.tables.local_id_root);
        let common_local_id_root = fcx_tables.local_id_root.unwrap();

        for (&id, &origin) in fcx_tables.closure_kind_origins().iter() {
            let hir_id = hir::HirId {
                owner: common_local_id_root.index,
                local_id: id,
            };
            self.tables
                .closure_kind_origins_mut()
                .insert(hir_id, origin);
        }
    }

    fn visit_cast_types(&mut self) {
        let fcx_tables = self.fcx.tables.borrow();
        let fcx_cast_kinds = fcx_tables.cast_kinds();
        debug_assert_eq!(fcx_tables.local_id_root, self.tables.local_id_root);
        let mut self_cast_kinds = self.tables.cast_kinds_mut();
        let common_local_id_root = fcx_tables.local_id_root.unwrap();

        for (&local_id, &cast_kind) in fcx_cast_kinds.iter() {
            let hir_id = hir::HirId {
                owner: common_local_id_root.index,
                local_id,
            };
            self_cast_kinds.insert(hir_id, cast_kind);
        }
    }

    fn visit_free_region_map(&mut self) {
        let free_region_map = self.tcx()
            .lift_to_global(&self.fcx.tables.borrow().free_region_map);
        let free_region_map = free_region_map.expect("all regions in free-region-map are global");
        self.tables.free_region_map = free_region_map;
    }

    fn visit_user_provided_tys(&mut self) {
        let fcx_tables = self.fcx.tables.borrow();
        debug_assert_eq!(fcx_tables.local_id_root, self.tables.local_id_root);
        let common_local_id_root = fcx_tables.local_id_root.unwrap();

        for (&local_id, c_ty) in fcx_tables.user_provided_tys().iter() {
            let hir_id = hir::HirId {
                owner: common_local_id_root.index,
                local_id,
            };

            let c_ty = if let Some(c_ty) = self.tcx().lift_to_global(c_ty) {
                c_ty
            } else {
                span_bug!(
                    hir_id.to_span(&self.fcx.tcx),
                    "writeback: `{:?}` missing from the global type context",
                    c_ty
                );
            };

            self.tables
                .user_provided_tys_mut()
                .insert(hir_id, c_ty.clone());
        }
    }

    fn visit_opaque_types(&mut self, span: Span) {
        for (&def_id, opaque_defn) in self.fcx.opaque_types.borrow().iter() {
            let node_id = self.tcx().hir.as_local_node_id(def_id).unwrap();
            let instantiated_ty = self.resolve(&opaque_defn.concrete_ty, &node_id);

            let generics = self.tcx().generics_of(def_id);

            let definition_ty = if generics.parent.is_some() {
                // impl trait
                self.fcx.infer_opaque_definition_from_instantiation(
                    def_id,
                    opaque_defn,
                    instantiated_ty,
                )
            } else {
                // prevent
                // * `fn foo<T>() -> Foo<T>`
                // * `fn foo<T: Bound + Other>() -> Foo<T>`
                // from being defining

                // Also replace all generic params with the ones from the existential type
                // definition so
                // ```rust
                // existential type Foo<T>: 'static;
                // fn foo<U>() -> Foo<U> { .. }
                // ```
                // figures out the concrete type with `U`, but the stored type is with `T`
                instantiated_ty.fold_with(&mut BottomUpFolder {
                    tcx: self.tcx().global_tcx(),
                    fldop: |ty| {
                        trace!("checking type {:?}: {:#?}", ty, ty.sty);
                        // find a type parameter
                        if let ty::Param(..) = ty.sty {
                            // look it up in the substitution list
                            assert_eq!(opaque_defn.substs.len(), generics.params.len());
                            for (subst, param) in opaque_defn.substs.iter().zip(&generics.params) {
                                if let UnpackedKind::Type(subst) = subst.unpack() {
                                    if subst == ty {
                                        // found it in the substitution list, replace with the
                                        // parameter from the existential type
                                        return self.tcx()
                                            .global_tcx()
                                            .mk_ty_param(param.index, param.name);
                                    }
                                }
                            }
                            self.tcx()
                                .sess
                                .struct_span_err(
                                    span,
                                    &format!(
                                        "type parameter `{}` is part of concrete type but not used \
                                        in parameter list for existential type",
                                        ty,
                                    ),
                                )
                                .emit();
                            return self.tcx().types.err;
                        }
                        ty
                    },
                    reg_op: |region| {
                        match region {
                            // ignore static regions
                            ty::ReStatic => region,
                            _ => {
                                trace!("checking {:?}", region);
                                for (subst, p) in opaque_defn.substs.iter().zip(&generics.params) {
                                    if let UnpackedKind::Lifetime(subst) = subst.unpack() {
                                        if subst == region {
                                            // found it in the substitution list, replace with the
                                            // parameter from the existential type
                                            let reg = ty::EarlyBoundRegion {
                                                def_id: p.def_id,
                                                index: p.index,
                                                name: p.name,
                                            };
                                            trace!("replace {:?} with {:?}", region, reg);
                                            return self.tcx()
                                                .global_tcx()
                                                .mk_region(ty::ReEarlyBound(reg));
                                        }
                                    }
                                }
                                trace!("opaque_defn: {:#?}", opaque_defn);
                                trace!("generics: {:#?}", generics);
                                self.tcx()
                                    .sess
                                    .struct_span_err(
                                        span,
                                        "non-defining existential type use in defining scope",
                                    )
                                    .span_label(
                                        span,
                                        format!(
                                            "lifetime `{}` is part of concrete type but not used \
                                             in parameter list of existential type",
                                            region,
                                        ),
                                    )
                                    .emit();
                                self.tcx().global_tcx().mk_region(ty::ReStatic)
                            }
                        }
                    },
                })
            };

            if let ty::Opaque(defin_ty_def_id, _substs) = definition_ty.sty {
                if def_id == defin_ty_def_id {
                    // Concrete type resolved to the existential type itself
                    // Force a cycle error
                    self.tcx().at(span).type_of(defin_ty_def_id);
                }
            }

            let old = self.tables
                .concrete_existential_types
                .insert(def_id, definition_ty);
            if let Some(old) = old {
                if old != definition_ty {
                    span_bug!(
                        span,
                        "visit_opaque_types tried to write \
                        different types for the same existential type: {:?}, {:?}, {:?}",
                        def_id,
                        definition_ty,
                        old,
                    );
                }
            }
        }
    }

    fn visit_field_id(&mut self, node_id: ast::NodeId) {
        let hir_id = self.tcx().hir.node_to_hir_id(node_id);
        if let Some(index) = self.fcx
            .tables
            .borrow_mut()
            .field_indices_mut()
            .remove(hir_id)
        {
            self.tables.field_indices_mut().insert(hir_id, index);
        }
    }

    fn visit_node_id(&mut self, span: Span, hir_id: hir::HirId) {
        // Export associated path extensions and method resolutions.
        if let Some(def) = self.fcx
            .tables
            .borrow_mut()
            .type_dependent_defs_mut()
            .remove(hir_id)
        {
            self.tables.type_dependent_defs_mut().insert(hir_id, def);
        }

        // Resolve any borrowings for the node with id `node_id`
        self.visit_adjustments(span, hir_id);

        // Resolve the type of the node with id `node_id`
        let n_ty = self.fcx.node_ty(hir_id);
        let n_ty = self.resolve(&n_ty, &span);
        self.write_ty_to_tables(hir_id, n_ty);
        debug!("Node {:?} has type {:?}", hir_id, n_ty);

        // Resolve any substitutions
        if let Some(substs) = self.fcx.tables.borrow().node_substs_opt(hir_id) {
            let substs = self.resolve(&substs, &span);
            debug!("write_substs_to_tcx({:?}, {:?})", hir_id, substs);
            assert!(!substs.needs_infer() && !substs.has_skol());
            self.tables.node_substs_mut().insert(hir_id, substs);
        }

        // Copy over any user-substs
        if let Some(user_substs) = self.fcx.tables.borrow().user_substs(hir_id) {
            let user_substs = self.tcx().lift_to_global(&user_substs).unwrap();
            self.tables.user_substs_mut().insert(hir_id, user_substs);

            // Unit-testing mechanism:
            if self.rustc_dump_user_substs {
                let node_id = self.tcx().hir.hir_to_node_id(hir_id);
                let span = self.tcx().hir.span(node_id);
                self.tcx().sess.span_err(
                    span,
                    &format!("user substs: {:?}", user_substs),
                );
            }
        }
    }

    fn visit_adjustments(&mut self, span: Span, hir_id: hir::HirId) {
        let adjustment = self.fcx
            .tables
            .borrow_mut()
            .adjustments_mut()
            .remove(hir_id);
        match adjustment {
            None => {
                debug!("No adjustments for node {:?}", hir_id);
            }

            Some(adjustment) => {
                let resolved_adjustment = self.resolve(&adjustment, &span);
                debug!(
                    "Adjustments for node {:?}: {:?}",
                    hir_id, resolved_adjustment
                );
                self.tables
                    .adjustments_mut()
                    .insert(hir_id, resolved_adjustment);
            }
        }
    }

    fn visit_pat_adjustments(&mut self, span: Span, hir_id: hir::HirId) {
        let adjustment = self.fcx
            .tables
            .borrow_mut()
            .pat_adjustments_mut()
            .remove(hir_id);
        match adjustment {
            None => {
                debug!("No pat_adjustments for node {:?}", hir_id);
            }

            Some(adjustment) => {
                let resolved_adjustment = self.resolve(&adjustment, &span);
                debug!(
                    "pat_adjustments for node {:?}: {:?}",
                    hir_id, resolved_adjustment
                );
                self.tables
                    .pat_adjustments_mut()
                    .insert(hir_id, resolved_adjustment);
            }
        }
    }

    fn visit_liberated_fn_sigs(&mut self) {
        let fcx_tables = self.fcx.tables.borrow();
        debug_assert_eq!(fcx_tables.local_id_root, self.tables.local_id_root);
        let common_local_id_root = fcx_tables.local_id_root.unwrap();

        for (&local_id, fn_sig) in fcx_tables.liberated_fn_sigs().iter() {
            let hir_id = hir::HirId {
                owner: common_local_id_root.index,
                local_id,
            };
            let fn_sig = self.resolve(fn_sig, &hir_id);
            self.tables
                .liberated_fn_sigs_mut()
                .insert(hir_id, fn_sig.clone());
        }
    }

    fn visit_fru_field_types(&mut self) {
        let fcx_tables = self.fcx.tables.borrow();
        debug_assert_eq!(fcx_tables.local_id_root, self.tables.local_id_root);
        let common_local_id_root = fcx_tables.local_id_root.unwrap();

        for (&local_id, ftys) in fcx_tables.fru_field_types().iter() {
            let hir_id = hir::HirId {
                owner: common_local_id_root.index,
                local_id,
            };
            let ftys = self.resolve(ftys, &hir_id);
            self.tables.fru_field_types_mut().insert(hir_id, ftys);
        }
    }

    fn resolve<T>(&self, x: &T, span: &dyn Locatable) -> T::Lifted
    where
        T: TypeFoldable<'tcx> + ty::Lift<'gcx>,
    {
        let x = x.fold_with(&mut Resolver::new(self.fcx, span, self.body));
        if let Some(lifted) = self.tcx().lift_to_global(&x) {
            lifted
        } else {
            span_bug!(
                span.to_span(&self.fcx.tcx),
                "writeback: `{:?}` missing from the global type context",
                x
            );
        }
    }
}

trait Locatable {
    fn to_span(&self, tcx: &TyCtxt) -> Span;
}

impl Locatable for Span {
    fn to_span(&self, _: &TyCtxt) -> Span {
        *self
    }
}

impl Locatable for ast::NodeId {
    fn to_span(&self, tcx: &TyCtxt) -> Span {
        tcx.hir.span(*self)
    }
}

impl Locatable for DefIndex {
    fn to_span(&self, tcx: &TyCtxt) -> Span {
        let node_id = tcx.hir.def_index_to_node_id(*self);
        tcx.hir.span(node_id)
    }
}

impl Locatable for hir::HirId {
    fn to_span(&self, tcx: &TyCtxt) -> Span {
        let node_id = tcx.hir.hir_to_node_id(*self);
        tcx.hir.span(node_id)
    }
}

///////////////////////////////////////////////////////////////////////////
// The Resolver. This is the type folding engine that detects
// unresolved types and so forth.

struct Resolver<'cx, 'gcx: 'cx + 'tcx, 'tcx: 'cx> {
    tcx: TyCtxt<'cx, 'gcx, 'tcx>,
    infcx: &'cx InferCtxt<'cx, 'gcx, 'tcx>,
    span: &'cx dyn Locatable,
    body: &'gcx hir::Body,
}

impl<'cx, 'gcx, 'tcx> Resolver<'cx, 'gcx, 'tcx> {
    fn new(
        fcx: &'cx FnCtxt<'cx, 'gcx, 'tcx>,
        span: &'cx dyn Locatable,
        body: &'gcx hir::Body,
    ) -> Resolver<'cx, 'gcx, 'tcx> {
        Resolver {
            tcx: fcx.tcx,
            infcx: fcx,
            span,
            body,
        }
    }

    fn report_error(&self, t: Ty<'tcx>) {
        if !self.tcx.sess.has_errors() {
            self.infcx
                .need_type_info_err(Some(self.body.id()), self.span.to_span(&self.tcx), t)
                .emit();
        }
    }
}

impl<'cx, 'gcx, 'tcx> TypeFolder<'gcx, 'tcx> for Resolver<'cx, 'gcx, 'tcx> {
    fn tcx<'a>(&'a self) -> TyCtxt<'a, 'gcx, 'tcx> {
        self.tcx
    }

    fn fold_ty(&mut self, t: Ty<'tcx>) -> Ty<'tcx> {
        match self.infcx.fully_resolve(&t) {
            Ok(t) => t,
            Err(_) => {
                debug!(
                    "Resolver::fold_ty: input type `{:?}` not fully resolvable",
                    t
                );
                self.report_error(t);
                self.tcx().types.err
            }
        }
    }

    // FIXME This should be carefully checked
    // We could use `self.report_error` but it doesn't accept a ty::Region, right now.
    fn fold_region(&mut self, r: ty::Region<'tcx>) -> ty::Region<'tcx> {
        match self.infcx.fully_resolve(&r) {
            Ok(r) => r,
            Err(_) => self.tcx.types.re_static,
        }
    }
}

///////////////////////////////////////////////////////////////////////////
// During type check, we store promises with the result of trait
// lookup rather than the actual results (because the results are not
// necessarily available immediately). These routines unwind the
// promises. It is expected that we will have already reported any
// errors that may be encountered, so if the promises store an error,
// a dummy result is returned.