1 //! Code to extract the universally quantified regions declared on a
2 //! function and the relationships between them. For example:
5 //! fn foo<'a, 'b, 'c: 'b>() { }
8 //! here we would return a map assigning each of `{'a, 'b, 'c}`
9 //! to an index, as well as the `FreeRegionMap` which can compute
10 //! relationships between them.
12 //! The code in this file doesn't *do anything* with those results; it
13 //! just returns them for other code to use.
16 use rustc_data_structures::fx::FxHashMap;
17 use rustc_errors::DiagnosticBuilder;
19 use rustc_hir::def_id::{DefId, LocalDefId};
20 use rustc_hir::lang_items::LangItem;
21 use rustc_hir::{BodyOwnerKind, HirId};
22 use rustc_index::vec::{Idx, IndexVec};
23 use rustc_infer::infer::{InferCtxt, NllRegionVariableOrigin};
24 use rustc_middle::ty::fold::TypeFoldable;
25 use rustc_middle::ty::subst::{InternalSubsts, Subst, SubstsRef};
26 use rustc_middle::ty::{self, InlineConstSubsts, InlineConstSubstsParts, RegionVid, Ty, TyCtxt};
29 use crate::nll::ToRegionVid;
32 pub struct UniversalRegions<'tcx> {
33 indices: UniversalRegionIndices<'tcx>,
35 /// The vid assigned to `'static`
36 pub fr_static: RegionVid,
38 /// A special region vid created to represent the current MIR fn
39 /// body. It will outlive the entire CFG but it will not outlive
40 /// any other universal regions.
41 pub fr_fn_body: RegionVid,
43 /// We create region variables such that they are ordered by their
44 /// `RegionClassification`. The first block are globals, then
45 /// externals, then locals. So, things from:
46 /// - `FIRST_GLOBAL_INDEX..first_extern_index` are global,
47 /// - `first_extern_index..first_local_index` are external,
48 /// - `first_local_index..num_universals` are local.
49 first_extern_index: usize,
51 /// See `first_extern_index`.
52 first_local_index: usize,
54 /// The total number of universal region variables instantiated.
55 num_universals: usize,
57 /// A special region variable created for the `'empty(U0)` region.
58 /// Note that this is **not** a "universal" region, as it doesn't
59 /// represent a universally bound placeholder or any such thing.
60 /// But we do create it here in this type because it's a useful region
61 /// to have around in a few limited cases.
62 pub root_empty: RegionVid,
64 /// The "defining" type for this function, with all universal
65 /// regions instantiated. For a closure or generator, this is the
66 /// closure type, but for a top-level function it's the `FnDef`.
67 pub defining_ty: DefiningTy<'tcx>,
69 /// The return type of this function, with all regions replaced by
70 /// their universal `RegionVid` equivalents.
72 /// N.B., associated types in this type have not been normalized,
73 /// as the name suggests. =)
74 pub unnormalized_output_ty: Ty<'tcx>,
76 /// The fully liberated input types of this function, with all
77 /// regions replaced by their universal `RegionVid` equivalents.
79 /// N.B., associated types in these types have not been normalized,
80 /// as the name suggests. =)
81 pub unnormalized_input_tys: &'tcx [Ty<'tcx>],
83 pub yield_ty: Option<Ty<'tcx>>,
86 /// The "defining type" for this MIR. The key feature of the "defining
87 /// type" is that it contains the information needed to derive all the
88 /// universal regions that are in scope as well as the types of the
89 /// inputs/output from the MIR. In general, early-bound universal
90 /// regions appear free in the defining type and late-bound regions
91 /// appear bound in the signature.
92 #[derive(Copy, Clone, Debug)]
93 pub enum DefiningTy<'tcx> {
94 /// The MIR is a closure. The signature is found via
95 /// `ClosureSubsts::closure_sig_ty`.
96 Closure(DefId, SubstsRef<'tcx>),
98 /// The MIR is a generator. The signature is that generators take
99 /// no parameters and return the result of
100 /// `ClosureSubsts::generator_return_ty`.
101 Generator(DefId, SubstsRef<'tcx>, hir::Movability),
103 /// The MIR is a fn item with the given `DefId` and substs. The signature
104 /// of the function can be bound then with the `fn_sig` query.
105 FnDef(DefId, SubstsRef<'tcx>),
107 /// The MIR represents some form of constant. The signature then
108 /// is that it has no inputs and a single return value, which is
109 /// the value of the constant.
110 Const(DefId, SubstsRef<'tcx>),
112 /// The MIR represents an inline const. The signature has no inputs and a
113 /// single return value found via `InlineConstSubsts::ty`.
114 InlineConst(DefId, SubstsRef<'tcx>),
117 impl<'tcx> DefiningTy<'tcx> {
118 /// Returns a list of all the upvar types for this MIR. If this is
119 /// not a closure or generator, there are no upvars, and hence it
120 /// will be an empty list. The order of types in this list will
121 /// match up with the upvar order in the HIR, typesystem, and MIR.
122 pub fn upvar_tys(self) -> impl Iterator<Item = Ty<'tcx>> + 'tcx {
124 DefiningTy::Closure(_, substs) => Either::Left(substs.as_closure().upvar_tys()),
125 DefiningTy::Generator(_, substs, _) => {
126 Either::Right(Either::Left(substs.as_generator().upvar_tys()))
128 DefiningTy::FnDef(..) | DefiningTy::Const(..) | DefiningTy::InlineConst(..) => {
129 Either::Right(Either::Right(iter::empty()))
134 /// Number of implicit inputs -- notably the "environment"
135 /// parameter for closures -- that appear in MIR but not in the
137 pub fn implicit_inputs(self) -> usize {
139 DefiningTy::Closure(..) | DefiningTy::Generator(..) => 1,
140 DefiningTy::FnDef(..) | DefiningTy::Const(..) | DefiningTy::InlineConst(..) => 0,
144 pub fn is_fn_def(&self) -> bool {
145 matches!(*self, DefiningTy::FnDef(..))
148 pub fn is_const(&self) -> bool {
149 matches!(*self, DefiningTy::Const(..) | DefiningTy::InlineConst(..))
152 pub fn def_id(&self) -> DefId {
154 DefiningTy::Closure(def_id, ..)
155 | DefiningTy::Generator(def_id, ..)
156 | DefiningTy::FnDef(def_id, ..)
157 | DefiningTy::Const(def_id, ..)
158 | DefiningTy::InlineConst(def_id, ..) => def_id,
164 struct UniversalRegionIndices<'tcx> {
165 /// For those regions that may appear in the parameter environment
166 /// ('static and early-bound regions), we maintain a map from the
167 /// `ty::Region` to the internal `RegionVid` we are using. This is
168 /// used because trait matching and type-checking will feed us
169 /// region constraints that reference those regions and we need to
170 /// be able to map them our internal `RegionVid`. This is
171 /// basically equivalent to an `InternalSubsts`, except that it also
172 /// contains an entry for `ReStatic` -- it might be nice to just
173 /// use a substs, and then handle `ReStatic` another way.
174 indices: FxHashMap<ty::Region<'tcx>, RegionVid>,
177 #[derive(Debug, PartialEq)]
178 pub enum RegionClassification {
179 /// A **global** region is one that can be named from
180 /// anywhere. There is only one, `'static`.
183 /// An **external** region is only relevant for closures. In that
184 /// case, it refers to regions that are free in the closure type
185 /// -- basically, something bound in the surrounding context.
187 /// Consider this example:
190 /// fn foo<'a, 'b>(a: &'a u32, b: &'b u32, c: &'static u32) {
191 /// let closure = for<'x> |x: &'x u32| { .. };
192 /// ^^^^^^^ pretend this were legal syntax
193 /// for declaring a late-bound region in
194 /// a closure signature
198 /// Here, the lifetimes `'a` and `'b` would be **external** to the
201 /// If we are not analyzing a closure, there are no external
205 /// A **local** lifetime is one about which we know the full set
206 /// of relevant constraints (that is, relationships to other named
207 /// regions). For a closure, this includes any region bound in
208 /// the closure's signature. For a fn item, this includes all
209 /// regions other than global ones.
211 /// Continuing with the example from `External`, if we were
212 /// analyzing the closure, then `'x` would be local (and `'a` and
213 /// `'b` are external). If we are analyzing the function item
214 /// `foo`, then `'a` and `'b` are local (and `'x` is not in
219 const FIRST_GLOBAL_INDEX: usize = 0;
221 impl<'tcx> UniversalRegions<'tcx> {
222 /// Creates a new and fully initialized `UniversalRegions` that
223 /// contains indices for all the free regions found in the given
224 /// MIR -- that is, all the regions that appear in the function's
225 /// signature. This will also compute the relationships that are
226 /// known between those regions.
228 infcx: &InferCtxt<'_, 'tcx>,
229 mir_def: ty::WithOptConstParam<LocalDefId>,
230 param_env: ty::ParamEnv<'tcx>,
233 let mir_hir_id = tcx.hir().local_def_id_to_hir_id(mir_def.did);
234 UniversalRegionsBuilder { infcx, mir_def, mir_hir_id, param_env }.build()
237 /// Given a reference to a closure type, extracts all the values
238 /// from its free regions and returns a vector with them. This is
239 /// used when the closure's creator checks that the
240 /// `ClosureRegionRequirements` are met. The requirements from
241 /// `ClosureRegionRequirements` are expressed in terms of
242 /// `RegionVid` entries that map into the returned vector `V`: so
243 /// if the `ClosureRegionRequirements` contains something like
244 /// `'1: '2`, then the caller would impose the constraint that
246 pub fn closure_mapping(
248 closure_substs: SubstsRef<'tcx>,
249 expected_num_vars: usize,
250 typeck_root_def_id: DefId,
251 ) -> IndexVec<RegionVid, ty::Region<'tcx>> {
252 let mut region_mapping = IndexVec::with_capacity(expected_num_vars);
253 region_mapping.push(tcx.lifetimes.re_static);
254 tcx.for_each_free_region(&closure_substs, |fr| {
255 region_mapping.push(fr);
258 for_each_late_bound_region_defined_on(tcx, typeck_root_def_id, |r| {
259 region_mapping.push(r);
263 region_mapping.len(),
265 "index vec had unexpected number of variables"
271 /// Returns `true` if `r` is a member of this set of universal regions.
272 pub fn is_universal_region(&self, r: RegionVid) -> bool {
273 (FIRST_GLOBAL_INDEX..self.num_universals).contains(&r.index())
276 /// Classifies `r` as a universal region, returning `None` if this
277 /// is not a member of this set of universal regions.
278 pub fn region_classification(&self, r: RegionVid) -> Option<RegionClassification> {
279 let index = r.index();
280 if (FIRST_GLOBAL_INDEX..self.first_extern_index).contains(&index) {
281 Some(RegionClassification::Global)
282 } else if (self.first_extern_index..self.first_local_index).contains(&index) {
283 Some(RegionClassification::External)
284 } else if (self.first_local_index..self.num_universals).contains(&index) {
285 Some(RegionClassification::Local)
291 /// Returns an iterator over all the RegionVids corresponding to
292 /// universally quantified free regions.
293 pub fn universal_regions(&self) -> impl Iterator<Item = RegionVid> {
294 (FIRST_GLOBAL_INDEX..self.num_universals).map(RegionVid::new)
297 /// Returns `true` if `r` is classified as an local region.
298 pub fn is_local_free_region(&self, r: RegionVid) -> bool {
299 self.region_classification(r) == Some(RegionClassification::Local)
302 /// Returns the number of universal regions created in any category.
303 pub fn len(&self) -> usize {
307 /// Returns the number of global plus external universal regions.
308 /// For closures, these are the regions that appear free in the
309 /// closure type (versus those bound in the closure
310 /// signature). They are therefore the regions between which the
311 /// closure may impose constraints that its creator must verify.
312 pub fn num_global_and_external_regions(&self) -> usize {
313 self.first_local_index
316 /// Gets an iterator over all the early-bound regions that have names.
317 pub fn named_universal_regions<'s>(
319 ) -> impl Iterator<Item = (ty::Region<'tcx>, ty::RegionVid)> + 's {
320 self.indices.indices.iter().map(|(&r, &v)| (r, v))
323 /// See `UniversalRegionIndices::to_region_vid`.
324 pub fn to_region_vid(&self, r: ty::Region<'tcx>) -> RegionVid {
325 if let ty::ReEmpty(ty::UniverseIndex::ROOT) = r {
328 self.indices.to_region_vid(r)
332 /// As part of the NLL unit tests, you can annotate a function with
333 /// `#[rustc_regions]`, and we will emit information about the region
334 /// inference context and -- in particular -- the external constraints
335 /// that this region imposes on others. The methods in this file
336 /// handle the part about dumping the inference context internal
338 crate fn annotate(&self, tcx: TyCtxt<'tcx>, err: &mut DiagnosticBuilder<'_>) {
339 match self.defining_ty {
340 DefiningTy::Closure(def_id, substs) => {
342 "defining type: {} with closure substs {:#?}",
343 tcx.def_path_str_with_substs(def_id, substs),
344 &substs[tcx.generics_of(def_id).parent_count..],
347 // FIXME: It'd be nice to print the late-bound regions
348 // here, but unfortunately these wind up stored into
349 // tests, and the resulting print-outs include def-ids
350 // and other things that are not stable across tests!
351 // So we just include the region-vid. Annoying.
352 let typeck_root_def_id = tcx.typeck_root_def_id(def_id);
353 for_each_late_bound_region_defined_on(tcx, typeck_root_def_id, |r| {
354 err.note(&format!("late-bound region is {:?}", self.to_region_vid(r),));
357 DefiningTy::Generator(def_id, substs, _) => {
359 "defining type: {} with generator substs {:#?}",
360 tcx.def_path_str_with_substs(def_id, substs),
361 &substs[tcx.generics_of(def_id).parent_count..],
364 // FIXME: As above, we'd like to print out the region
365 // `r` but doing so is not stable across architectures
367 let typeck_root_def_id = tcx.typeck_root_def_id(def_id);
368 for_each_late_bound_region_defined_on(tcx, typeck_root_def_id, |r| {
369 err.note(&format!("late-bound region is {:?}", self.to_region_vid(r),));
372 DefiningTy::FnDef(def_id, substs) => {
375 tcx.def_path_str_with_substs(def_id, substs),
378 DefiningTy::Const(def_id, substs) => {
380 "defining constant type: {}",
381 tcx.def_path_str_with_substs(def_id, substs),
384 DefiningTy::InlineConst(def_id, substs) => {
386 "defining inline constant type: {}",
387 tcx.def_path_str_with_substs(def_id, substs),
394 struct UniversalRegionsBuilder<'cx, 'tcx> {
395 infcx: &'cx InferCtxt<'cx, 'tcx>,
396 mir_def: ty::WithOptConstParam<LocalDefId>,
398 param_env: ty::ParamEnv<'tcx>,
401 const FR: NllRegionVariableOrigin = NllRegionVariableOrigin::FreeRegion;
403 impl<'cx, 'tcx> UniversalRegionsBuilder<'cx, 'tcx> {
404 fn build(self) -> UniversalRegions<'tcx> {
405 debug!("build(mir_def={:?})", self.mir_def);
407 let param_env = self.param_env;
408 debug!("build: param_env={:?}", param_env);
410 assert_eq!(FIRST_GLOBAL_INDEX, self.infcx.num_region_vars());
412 // Create the "global" region that is always free in all contexts: 'static.
413 let fr_static = self.infcx.next_nll_region_var(FR).to_region_vid();
415 // We've now added all the global regions. The next ones we
416 // add will be external.
417 let first_extern_index = self.infcx.num_region_vars();
419 let defining_ty = self.defining_ty();
420 debug!("build: defining_ty={:?}", defining_ty);
422 let mut indices = self.compute_indices(fr_static, defining_ty);
423 debug!("build: indices={:?}", indices);
425 let typeck_root_def_id = self.infcx.tcx.typeck_root_def_id(self.mir_def.did.to_def_id());
427 // If this is a closure or generator, then the late-bound regions from the enclosing
428 // function are actually external regions to us. For example, here, 'a is not local
429 // to the closure c (although it is local to the fn foo):
431 // let c = || { let x: &'a u32 = ...; }
433 if self.mir_def.did.to_def_id() != typeck_root_def_id {
435 .replace_late_bound_regions_with_nll_infer_vars(self.mir_def.did, &mut indices)
438 let bound_inputs_and_output = self.compute_inputs_and_output(&indices, defining_ty);
440 // "Liberate" the late-bound regions. These correspond to
441 // "local" free regions.
442 let first_local_index = self.infcx.num_region_vars();
443 let inputs_and_output = self.infcx.replace_bound_regions_with_nll_infer_vars(
446 bound_inputs_and_output,
449 // Converse of above, if this is a function then the late-bound regions declared on its
450 // signature are local to the fn.
451 if self.mir_def.did.to_def_id() == typeck_root_def_id {
453 .replace_late_bound_regions_with_nll_infer_vars(self.mir_def.did, &mut indices);
456 let (unnormalized_output_ty, mut unnormalized_input_tys) =
457 inputs_and_output.split_last().unwrap();
459 // C-variadic fns also have a `VaList` input that's not listed in the signature
460 // (as it's created inside the body itself, not passed in from outside).
461 if let DefiningTy::FnDef(def_id, _) = defining_ty {
462 if self.infcx.tcx.fn_sig(def_id).c_variadic() {
463 let va_list_did = self.infcx.tcx.require_lang_item(
465 Some(self.infcx.tcx.def_span(self.mir_def.did)),
470 .mk_region(ty::ReVar(self.infcx.next_nll_region_var(FR).to_region_vid()));
472 self.infcx.tcx.type_of(va_list_did).subst(self.infcx.tcx, &[region.into()]);
474 unnormalized_input_tys = self.infcx.tcx.mk_type_list(
475 unnormalized_input_tys.iter().copied().chain(iter::once(va_list_ty)),
480 let fr_fn_body = self.infcx.next_nll_region_var(FR).to_region_vid();
481 let num_universals = self.infcx.num_region_vars();
483 debug!("build: global regions = {}..{}", FIRST_GLOBAL_INDEX, first_extern_index);
484 debug!("build: extern regions = {}..{}", first_extern_index, first_local_index);
485 debug!("build: local regions = {}..{}", first_local_index, num_universals);
487 let yield_ty = match defining_ty {
488 DefiningTy::Generator(_, substs, _) => Some(substs.as_generator().yield_ty()),
492 let root_empty = self
494 .next_nll_region_var(NllRegionVariableOrigin::RootEmptyRegion)
506 unnormalized_output_ty,
507 unnormalized_input_tys,
512 /// Returns the "defining type" of the current MIR;
513 /// see `DefiningTy` for details.
514 fn defining_ty(&self) -> DefiningTy<'tcx> {
515 let tcx = self.infcx.tcx;
516 let typeck_root_def_id = tcx.typeck_root_def_id(self.mir_def.did.to_def_id());
518 match tcx.hir().body_owner_kind(self.mir_hir_id) {
519 BodyOwnerKind::Closure | BodyOwnerKind::Fn => {
520 let defining_ty = if self.mir_def.did.to_def_id() == typeck_root_def_id {
521 tcx.type_of(typeck_root_def_id)
523 let tables = tcx.typeck(self.mir_def.did);
524 tables.node_type(self.mir_hir_id)
527 debug!("defining_ty (pre-replacement): {:?}", defining_ty);
530 self.infcx.replace_free_regions_with_nll_infer_vars(FR, defining_ty);
532 match *defining_ty.kind() {
533 ty::Closure(def_id, substs) => DefiningTy::Closure(def_id, substs),
534 ty::Generator(def_id, substs, movability) => {
535 DefiningTy::Generator(def_id, substs, movability)
537 ty::FnDef(def_id, substs) => DefiningTy::FnDef(def_id, substs),
539 tcx.def_span(self.mir_def.did),
540 "expected defining type for `{:?}`: `{:?}`",
547 BodyOwnerKind::Const | BodyOwnerKind::Static(..) => {
548 let identity_substs = InternalSubsts::identity_for_item(tcx, typeck_root_def_id);
549 if self.mir_def.did.to_def_id() == typeck_root_def_id {
551 self.infcx.replace_free_regions_with_nll_infer_vars(FR, identity_substs);
552 DefiningTy::Const(self.mir_def.did.to_def_id(), substs)
554 let ty = tcx.typeck(self.mir_def.did).node_type(self.mir_hir_id);
555 let substs = InlineConstSubsts::new(
557 InlineConstSubstsParts { parent_substs: identity_substs, ty },
560 let substs = self.infcx.replace_free_regions_with_nll_infer_vars(FR, substs);
561 DefiningTy::InlineConst(self.mir_def.did.to_def_id(), substs)
567 /// Builds a hashmap that maps from the universal regions that are
568 /// in scope (as a `ty::Region<'tcx>`) to their indices (as a
569 /// `RegionVid`). The map returned by this function contains only
570 /// the early-bound regions.
573 fr_static: RegionVid,
574 defining_ty: DefiningTy<'tcx>,
575 ) -> UniversalRegionIndices<'tcx> {
576 let tcx = self.infcx.tcx;
577 let typeck_root_def_id = tcx.typeck_root_def_id(self.mir_def.did.to_def_id());
578 let identity_substs = InternalSubsts::identity_for_item(tcx, typeck_root_def_id);
579 let fr_substs = match defining_ty {
580 DefiningTy::Closure(_, ref substs)
581 | DefiningTy::Generator(_, ref substs, _)
582 | DefiningTy::InlineConst(_, ref substs) => {
583 // In the case of closures, we rely on the fact that
584 // the first N elements in the ClosureSubsts are
585 // inherited from the `typeck_root_def_id`.
586 // Therefore, when we zip together (below) with
587 // `identity_substs`, we will get only those regions
588 // that correspond to early-bound regions declared on
589 // the `typeck_root_def_id`.
590 assert!(substs.len() >= identity_substs.len());
591 assert_eq!(substs.regions().count(), identity_substs.regions().count());
595 DefiningTy::FnDef(_, substs) | DefiningTy::Const(_, substs) => substs,
598 let global_mapping = iter::once((tcx.lifetimes.re_static, fr_static));
600 iter::zip(identity_substs.regions(), fr_substs.regions().map(|r| r.to_region_vid()));
602 UniversalRegionIndices { indices: global_mapping.chain(subst_mapping).collect() }
605 fn compute_inputs_and_output(
607 indices: &UniversalRegionIndices<'tcx>,
608 defining_ty: DefiningTy<'tcx>,
609 ) -> ty::Binder<'tcx, &'tcx ty::List<Ty<'tcx>>> {
610 let tcx = self.infcx.tcx;
612 DefiningTy::Closure(def_id, substs) => {
613 assert_eq!(self.mir_def.did.to_def_id(), def_id);
614 let closure_sig = substs.as_closure().sig();
615 let inputs_and_output = closure_sig.inputs_and_output();
616 let bound_vars = tcx.mk_bound_variable_kinds(
620 .chain(iter::once(ty::BoundVariableKind::Region(ty::BrEnv))),
622 let br = ty::BoundRegion {
623 var: ty::BoundVar::from_usize(bound_vars.len() - 1),
626 let env_region = ty::ReLateBound(ty::INNERMOST, br);
627 let closure_ty = tcx.closure_env_ty(def_id, substs, env_region).unwrap();
629 // The "inputs" of the closure in the
630 // signature appear as a tuple. The MIR side
631 // flattens this tuple.
632 let (&output, tuplized_inputs) =
633 inputs_and_output.skip_binder().split_last().unwrap();
634 assert_eq!(tuplized_inputs.len(), 1, "multiple closure inputs");
635 let inputs = match tuplized_inputs[0].kind() {
636 ty::Tuple(inputs) => inputs,
637 _ => bug!("closure inputs not a tuple: {:?}", tuplized_inputs[0]),
640 ty::Binder::bind_with_vars(
642 iter::once(closure_ty)
643 .chain(inputs.iter().map(|k| k.expect_ty()))
644 .chain(iter::once(output)),
650 DefiningTy::Generator(def_id, substs, movability) => {
651 assert_eq!(self.mir_def.did.to_def_id(), def_id);
652 let resume_ty = substs.as_generator().resume_ty();
653 let output = substs.as_generator().return_ty();
654 let generator_ty = tcx.mk_generator(def_id, substs, movability);
655 let inputs_and_output =
656 self.infcx.tcx.intern_type_list(&[generator_ty, resume_ty, output]);
657 ty::Binder::dummy(inputs_and_output)
660 DefiningTy::FnDef(def_id, _) => {
661 let sig = tcx.fn_sig(def_id);
662 let sig = indices.fold_to_region_vids(tcx, sig);
663 sig.inputs_and_output()
666 DefiningTy::Const(def_id, _) => {
667 // For a constant body, there are no inputs, and one
668 // "output" (the type of the constant).
669 assert_eq!(self.mir_def.did.to_def_id(), def_id);
670 let ty = tcx.type_of(self.mir_def.def_id_for_type_of());
671 let ty = indices.fold_to_region_vids(tcx, ty);
672 ty::Binder::dummy(tcx.intern_type_list(&[ty]))
675 DefiningTy::InlineConst(def_id, substs) => {
676 assert_eq!(self.mir_def.did.to_def_id(), def_id);
677 let ty = substs.as_inline_const().ty();
678 ty::Binder::dummy(tcx.intern_type_list(&[ty]))
684 trait InferCtxtExt<'tcx> {
685 fn replace_free_regions_with_nll_infer_vars<T>(
687 origin: NllRegionVariableOrigin,
691 T: TypeFoldable<'tcx>;
693 fn replace_bound_regions_with_nll_infer_vars<T>(
695 origin: NllRegionVariableOrigin,
696 all_outlive_scope: LocalDefId,
697 value: ty::Binder<'tcx, T>,
698 indices: &mut UniversalRegionIndices<'tcx>,
701 T: TypeFoldable<'tcx>;
703 fn replace_late_bound_regions_with_nll_infer_vars(
705 mir_def_id: LocalDefId,
706 indices: &mut UniversalRegionIndices<'tcx>,
710 impl<'cx, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'cx, 'tcx> {
711 fn replace_free_regions_with_nll_infer_vars<T>(
713 origin: NllRegionVariableOrigin,
717 T: TypeFoldable<'tcx>,
719 self.tcx.fold_regions(value, &mut false, |_region, _depth| self.next_nll_region_var(origin))
722 fn replace_bound_regions_with_nll_infer_vars<T>(
724 origin: NllRegionVariableOrigin,
725 all_outlive_scope: LocalDefId,
726 value: ty::Binder<'tcx, T>,
727 indices: &mut UniversalRegionIndices<'tcx>,
730 T: TypeFoldable<'tcx>,
733 "replace_bound_regions_with_nll_infer_vars(value={:?}, all_outlive_scope={:?})",
734 value, all_outlive_scope,
736 let (value, _map) = self.tcx.replace_late_bound_regions(value, |br| {
737 debug!("replace_bound_regions_with_nll_infer_vars: br={:?}", br);
738 let liberated_region = self.tcx.mk_region(ty::ReFree(ty::FreeRegion {
739 scope: all_outlive_scope.to_def_id(),
740 bound_region: br.kind,
742 let region_vid = self.next_nll_region_var(origin);
743 indices.insert_late_bound_region(liberated_region, region_vid.to_region_vid());
745 "replace_bound_regions_with_nll_infer_vars: liberated_region={:?} => {:?}",
746 liberated_region, region_vid
753 /// Finds late-bound regions that do not appear in the parameter listing and adds them to the
754 /// indices vector. Typically, we identify late-bound regions as we process the inputs and
755 /// outputs of the closure/function. However, sometimes there are late-bound regions which do
756 /// not appear in the fn parameters but which are nonetheless in scope. The simplest case of
757 /// this are unused functions, like fn foo<'a>() { } (see e.g., #51351). Despite not being used,
758 /// users can still reference these regions (e.g., let x: &'a u32 = &22;), so we need to create
759 /// entries for them and store them in the indices map. This code iterates over the complete
760 /// set of late-bound regions and checks for any that we have not yet seen, adding them to the
762 fn replace_late_bound_regions_with_nll_infer_vars(
764 mir_def_id: LocalDefId,
765 indices: &mut UniversalRegionIndices<'tcx>,
767 debug!("replace_late_bound_regions_with_nll_infer_vars(mir_def_id={:?})", mir_def_id);
768 let typeck_root_def_id = self.tcx.typeck_root_def_id(mir_def_id.to_def_id());
769 for_each_late_bound_region_defined_on(self.tcx, typeck_root_def_id, |r| {
770 debug!("replace_late_bound_regions_with_nll_infer_vars: r={:?}", r);
771 if !indices.indices.contains_key(&r) {
772 let region_vid = self.next_nll_region_var(FR);
773 indices.insert_late_bound_region(r, region_vid.to_region_vid());
779 impl<'tcx> UniversalRegionIndices<'tcx> {
780 /// Initially, the `UniversalRegionIndices` map contains only the
781 /// early-bound regions in scope. Once that is all setup, we come
782 /// in later and instantiate the late-bound regions, and then we
783 /// insert the `ReFree` version of those into the map as
784 /// well. These are used for error reporting.
785 fn insert_late_bound_region(&mut self, r: ty::Region<'tcx>, vid: ty::RegionVid) {
786 debug!("insert_late_bound_region({:?}, {:?})", r, vid);
787 self.indices.insert(r, vid);
790 /// Converts `r` into a local inference variable: `r` can either
791 /// by a `ReVar` (i.e., already a reference to an inference
792 /// variable) or it can be `'static` or some early-bound
793 /// region. This is useful when taking the results from
794 /// type-checking and trait-matching, which may sometimes
795 /// reference those regions from the `ParamEnv`. It is also used
796 /// during initialization. Relies on the `indices` map having been
797 /// fully initialized.
798 pub fn to_region_vid(&self, r: ty::Region<'tcx>) -> RegionVid {
799 if let ty::ReVar(..) = r {
805 .unwrap_or_else(|| bug!("cannot convert `{:?}` to a region vid", r))
809 /// Replaces all free regions in `value` with region vids, as
810 /// returned by `to_region_vid`.
811 pub fn fold_to_region_vids<T>(&self, tcx: TyCtxt<'tcx>, value: T) -> T
813 T: TypeFoldable<'tcx>,
815 tcx.fold_regions(value, &mut false, |region, _| {
816 tcx.mk_region(ty::ReVar(self.to_region_vid(region)))
821 /// Iterates over the late-bound regions defined on fn_def_id and
822 /// invokes `f` with the liberated form of each one.
823 fn for_each_late_bound_region_defined_on<'tcx>(
826 mut f: impl FnMut(ty::Region<'tcx>),
828 if let Some((owner, late_bounds)) = tcx.is_late_bound_map(fn_def_id.expect_local()) {
829 for &late_bound in late_bounds.iter() {
830 let hir_id = HirId { owner, local_id: late_bound };
831 let name = tcx.hir().name(hir_id);
832 let region_def_id = tcx.hir().local_def_id(hir_id);
833 let liberated_region = tcx.mk_region(ty::ReFree(ty::FreeRegion {
834 scope: owner.to_def_id(),
835 bound_region: ty::BoundRegionKind::BrNamed(region_def_id.to_def_id(), name),