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
184 /// closures, generators, and inline consts. In that
185 /// case, it refers to regions that are free in the type
186 /// -- basically, something bound in the surrounding context.
188 /// Consider this example:
191 /// fn foo<'a, 'b>(a: &'a u32, b: &'b u32, c: &'static u32) {
192 /// let closure = for<'x> |x: &'x u32| { .. };
193 /// ^^^^^^^ pretend this were legal syntax
194 /// for declaring a late-bound region in
195 /// a closure signature
199 /// Here, the lifetimes `'a` and `'b` would be **external** to the
202 /// If we are not analyzing a closure/generator/inline-const,
203 /// there are no external lifetimes.
206 /// A **local** lifetime is one about which we know the full set
207 /// of relevant constraints (that is, relationships to other named
208 /// regions). For a closure, this includes any region bound in
209 /// the closure's signature. For a fn item, this includes all
210 /// regions other than global ones.
212 /// Continuing with the example from `External`, if we were
213 /// analyzing the closure, then `'x` would be local (and `'a` and
214 /// `'b` are external). If we are analyzing the function item
215 /// `foo`, then `'a` and `'b` are local (and `'x` is not in
220 const FIRST_GLOBAL_INDEX: usize = 0;
222 impl<'tcx> UniversalRegions<'tcx> {
223 /// Creates a new and fully initialized `UniversalRegions` that
224 /// contains indices for all the free regions found in the given
225 /// MIR -- that is, all the regions that appear in the function's
226 /// signature. This will also compute the relationships that are
227 /// known between those regions.
229 infcx: &InferCtxt<'_, 'tcx>,
230 mir_def: ty::WithOptConstParam<LocalDefId>,
231 param_env: ty::ParamEnv<'tcx>,
234 let mir_hir_id = tcx.hir().local_def_id_to_hir_id(mir_def.did);
235 UniversalRegionsBuilder { infcx, mir_def, mir_hir_id, param_env }.build()
238 /// Given a reference to a closure type, extracts all the values
239 /// from its free regions and returns a vector with them. This is
240 /// used when the closure's creator checks that the
241 /// `ClosureRegionRequirements` are met. The requirements from
242 /// `ClosureRegionRequirements` are expressed in terms of
243 /// `RegionVid` entries that map into the returned vector `V`: so
244 /// if the `ClosureRegionRequirements` contains something like
245 /// `'1: '2`, then the caller would impose the constraint that
247 pub fn closure_mapping(
249 closure_substs: SubstsRef<'tcx>,
250 expected_num_vars: usize,
251 typeck_root_def_id: DefId,
252 ) -> IndexVec<RegionVid, ty::Region<'tcx>> {
253 let mut region_mapping = IndexVec::with_capacity(expected_num_vars);
254 region_mapping.push(tcx.lifetimes.re_static);
255 tcx.for_each_free_region(&closure_substs, |fr| {
256 region_mapping.push(fr);
259 for_each_late_bound_region_defined_on(tcx, typeck_root_def_id, |r| {
260 region_mapping.push(r);
264 region_mapping.len(),
266 "index vec had unexpected number of variables"
272 /// Returns `true` if `r` is a member of this set of universal regions.
273 pub fn is_universal_region(&self, r: RegionVid) -> bool {
274 (FIRST_GLOBAL_INDEX..self.num_universals).contains(&r.index())
277 /// Classifies `r` as a universal region, returning `None` if this
278 /// is not a member of this set of universal regions.
279 pub fn region_classification(&self, r: RegionVid) -> Option<RegionClassification> {
280 let index = r.index();
281 if (FIRST_GLOBAL_INDEX..self.first_extern_index).contains(&index) {
282 Some(RegionClassification::Global)
283 } else if (self.first_extern_index..self.first_local_index).contains(&index) {
284 Some(RegionClassification::External)
285 } else if (self.first_local_index..self.num_universals).contains(&index) {
286 Some(RegionClassification::Local)
292 /// Returns an iterator over all the RegionVids corresponding to
293 /// universally quantified free regions.
294 pub fn universal_regions(&self) -> impl Iterator<Item = RegionVid> {
295 (FIRST_GLOBAL_INDEX..self.num_universals).map(RegionVid::new)
298 /// Returns `true` if `r` is classified as an local region.
299 pub fn is_local_free_region(&self, r: RegionVid) -> bool {
300 self.region_classification(r) == Some(RegionClassification::Local)
303 /// Returns the number of universal regions created in any category.
304 pub fn len(&self) -> usize {
308 /// Returns the number of global plus external universal regions.
309 /// For closures, these are the regions that appear free in the
310 /// closure type (versus those bound in the closure
311 /// signature). They are therefore the regions between which the
312 /// closure may impose constraints that its creator must verify.
313 pub fn num_global_and_external_regions(&self) -> usize {
314 self.first_local_index
317 /// Gets an iterator over all the early-bound regions that have names.
318 pub fn named_universal_regions<'s>(
320 ) -> impl Iterator<Item = (ty::Region<'tcx>, ty::RegionVid)> + 's {
321 self.indices.indices.iter().map(|(&r, &v)| (r, v))
324 /// See `UniversalRegionIndices::to_region_vid`.
325 pub fn to_region_vid(&self, r: ty::Region<'tcx>) -> RegionVid {
326 if let ty::ReEmpty(ty::UniverseIndex::ROOT) = r {
329 self.indices.to_region_vid(r)
333 /// As part of the NLL unit tests, you can annotate a function with
334 /// `#[rustc_regions]`, and we will emit information about the region
335 /// inference context and -- in particular -- the external constraints
336 /// that this region imposes on others. The methods in this file
337 /// handle the part about dumping the inference context internal
339 crate fn annotate(&self, tcx: TyCtxt<'tcx>, err: &mut DiagnosticBuilder<'_>) {
340 match self.defining_ty {
341 DefiningTy::Closure(def_id, substs) => {
343 "defining type: {} with closure substs {:#?}",
344 tcx.def_path_str_with_substs(def_id, substs),
345 &substs[tcx.generics_of(def_id).parent_count..],
348 // FIXME: It'd be nice to print the late-bound regions
349 // here, but unfortunately these wind up stored into
350 // tests, and the resulting print-outs include def-ids
351 // and other things that are not stable across tests!
352 // So we just include the region-vid. Annoying.
353 let typeck_root_def_id = tcx.typeck_root_def_id(def_id);
354 for_each_late_bound_region_defined_on(tcx, typeck_root_def_id, |r| {
355 err.note(&format!("late-bound region is {:?}", self.to_region_vid(r),));
358 DefiningTy::Generator(def_id, substs, _) => {
360 "defining type: {} with generator substs {:#?}",
361 tcx.def_path_str_with_substs(def_id, substs),
362 &substs[tcx.generics_of(def_id).parent_count..],
365 // FIXME: As above, we'd like to print out the region
366 // `r` but doing so is not stable across architectures
368 let typeck_root_def_id = tcx.typeck_root_def_id(def_id);
369 for_each_late_bound_region_defined_on(tcx, typeck_root_def_id, |r| {
370 err.note(&format!("late-bound region is {:?}", self.to_region_vid(r),));
373 DefiningTy::FnDef(def_id, substs) => {
376 tcx.def_path_str_with_substs(def_id, substs),
379 DefiningTy::Const(def_id, substs) => {
381 "defining constant type: {}",
382 tcx.def_path_str_with_substs(def_id, substs),
385 DefiningTy::InlineConst(def_id, substs) => {
387 "defining inline constant type: {}",
388 tcx.def_path_str_with_substs(def_id, substs),
395 struct UniversalRegionsBuilder<'cx, 'tcx> {
396 infcx: &'cx InferCtxt<'cx, 'tcx>,
397 mir_def: ty::WithOptConstParam<LocalDefId>,
399 param_env: ty::ParamEnv<'tcx>,
402 const FR: NllRegionVariableOrigin = NllRegionVariableOrigin::FreeRegion;
404 impl<'cx, 'tcx> UniversalRegionsBuilder<'cx, 'tcx> {
405 fn build(self) -> UniversalRegions<'tcx> {
406 debug!("build(mir_def={:?})", self.mir_def);
408 let param_env = self.param_env;
409 debug!("build: param_env={:?}", param_env);
411 assert_eq!(FIRST_GLOBAL_INDEX, self.infcx.num_region_vars());
413 // Create the "global" region that is always free in all contexts: 'static.
414 let fr_static = self.infcx.next_nll_region_var(FR).to_region_vid();
416 // We've now added all the global regions. The next ones we
417 // add will be external.
418 let first_extern_index = self.infcx.num_region_vars();
420 let defining_ty = self.defining_ty();
421 debug!("build: defining_ty={:?}", defining_ty);
423 let mut indices = self.compute_indices(fr_static, defining_ty);
424 debug!("build: indices={:?}", indices);
426 let typeck_root_def_id = self.infcx.tcx.typeck_root_def_id(self.mir_def.did.to_def_id());
428 // If this is is a 'root' body (not a closure/generator/inline const), then
429 // there are no extern regions, so the local regions start at the same
430 // position as the (empty) sub-list of extern regions
431 let first_local_index = if self.mir_def.did.to_def_id() == typeck_root_def_id {
434 // If this is a closure, generator, or inline-const, then the late-bound regions from the enclosing
435 // function are actually external regions to us. For example, here, 'a is not local
436 // to the closure c (although it is local to the fn foo):
438 // let c = || { let x: &'a u32 = ...; }
441 .replace_late_bound_regions_with_nll_infer_vars(self.mir_def.did, &mut indices);
442 // Any regions created during the execution of `defining_ty` or during the above
443 // late-bound region replacement are all considered 'extern' regions
444 self.infcx.num_region_vars()
447 // "Liberate" the late-bound regions. These correspond to
448 // "local" free regions.
450 let bound_inputs_and_output = self.compute_inputs_and_output(&indices, defining_ty);
452 let inputs_and_output = self.infcx.replace_bound_regions_with_nll_infer_vars(
455 bound_inputs_and_output,
458 // Converse of above, if this is a function then the late-bound regions declared on its
459 // signature are local to the fn.
460 if self.mir_def.did.to_def_id() == typeck_root_def_id {
462 .replace_late_bound_regions_with_nll_infer_vars(self.mir_def.did, &mut indices);
465 let (unnormalized_output_ty, mut unnormalized_input_tys) =
466 inputs_and_output.split_last().unwrap();
468 // C-variadic fns also have a `VaList` input that's not listed in the signature
469 // (as it's created inside the body itself, not passed in from outside).
470 if let DefiningTy::FnDef(def_id, _) = defining_ty {
471 if self.infcx.tcx.fn_sig(def_id).c_variadic() {
472 let va_list_did = self.infcx.tcx.require_lang_item(
474 Some(self.infcx.tcx.def_span(self.mir_def.did)),
479 .mk_region(ty::ReVar(self.infcx.next_nll_region_var(FR).to_region_vid()));
481 self.infcx.tcx.type_of(va_list_did).subst(self.infcx.tcx, &[region.into()]);
483 unnormalized_input_tys = self.infcx.tcx.mk_type_list(
484 unnormalized_input_tys.iter().copied().chain(iter::once(va_list_ty)),
489 let fr_fn_body = self.infcx.next_nll_region_var(FR).to_region_vid();
490 let num_universals = self.infcx.num_region_vars();
492 debug!("build: global regions = {}..{}", FIRST_GLOBAL_INDEX, first_extern_index);
493 debug!("build: extern regions = {}..{}", first_extern_index, first_local_index);
494 debug!("build: local regions = {}..{}", first_local_index, num_universals);
496 let yield_ty = match defining_ty {
497 DefiningTy::Generator(_, substs, _) => Some(substs.as_generator().yield_ty()),
501 let root_empty = self
503 .next_nll_region_var(NllRegionVariableOrigin::RootEmptyRegion)
515 unnormalized_output_ty,
516 unnormalized_input_tys,
521 /// Returns the "defining type" of the current MIR;
522 /// see `DefiningTy` for details.
523 fn defining_ty(&self) -> DefiningTy<'tcx> {
524 let tcx = self.infcx.tcx;
525 let typeck_root_def_id = tcx.typeck_root_def_id(self.mir_def.did.to_def_id());
527 match tcx.hir().body_owner_kind(self.mir_hir_id) {
528 BodyOwnerKind::Closure | BodyOwnerKind::Fn => {
529 let defining_ty = if self.mir_def.did.to_def_id() == typeck_root_def_id {
530 tcx.type_of(typeck_root_def_id)
532 let tables = tcx.typeck(self.mir_def.did);
533 tables.node_type(self.mir_hir_id)
536 debug!("defining_ty (pre-replacement): {:?}", defining_ty);
539 self.infcx.replace_free_regions_with_nll_infer_vars(FR, defining_ty);
541 match *defining_ty.kind() {
542 ty::Closure(def_id, substs) => DefiningTy::Closure(def_id, substs),
543 ty::Generator(def_id, substs, movability) => {
544 DefiningTy::Generator(def_id, substs, movability)
546 ty::FnDef(def_id, substs) => DefiningTy::FnDef(def_id, substs),
548 tcx.def_span(self.mir_def.did),
549 "expected defining type for `{:?}`: `{:?}`",
556 BodyOwnerKind::Const | BodyOwnerKind::Static(..) => {
557 let identity_substs = InternalSubsts::identity_for_item(tcx, typeck_root_def_id);
558 if self.mir_def.did.to_def_id() == typeck_root_def_id {
560 self.infcx.replace_free_regions_with_nll_infer_vars(FR, identity_substs);
561 DefiningTy::Const(self.mir_def.did.to_def_id(), substs)
563 let ty = tcx.typeck(self.mir_def.did).node_type(self.mir_hir_id);
564 let substs = InlineConstSubsts::new(
566 InlineConstSubstsParts { parent_substs: identity_substs, ty },
569 let substs = self.infcx.replace_free_regions_with_nll_infer_vars(FR, substs);
570 DefiningTy::InlineConst(self.mir_def.did.to_def_id(), substs)
576 /// Builds a hashmap that maps from the universal regions that are
577 /// in scope (as a `ty::Region<'tcx>`) to their indices (as a
578 /// `RegionVid`). The map returned by this function contains only
579 /// the early-bound regions.
582 fr_static: RegionVid,
583 defining_ty: DefiningTy<'tcx>,
584 ) -> UniversalRegionIndices<'tcx> {
585 let tcx = self.infcx.tcx;
586 let typeck_root_def_id = tcx.typeck_root_def_id(self.mir_def.did.to_def_id());
587 let identity_substs = InternalSubsts::identity_for_item(tcx, typeck_root_def_id);
588 let fr_substs = match defining_ty {
589 DefiningTy::Closure(_, ref substs)
590 | DefiningTy::Generator(_, ref substs, _)
591 | DefiningTy::InlineConst(_, ref substs) => {
592 // In the case of closures, we rely on the fact that
593 // the first N elements in the ClosureSubsts are
594 // inherited from the `typeck_root_def_id`.
595 // Therefore, when we zip together (below) with
596 // `identity_substs`, we will get only those regions
597 // that correspond to early-bound regions declared on
598 // the `typeck_root_def_id`.
599 assert!(substs.len() >= identity_substs.len());
600 assert_eq!(substs.regions().count(), identity_substs.regions().count());
604 DefiningTy::FnDef(_, substs) | DefiningTy::Const(_, substs) => substs,
607 let global_mapping = iter::once((tcx.lifetimes.re_static, fr_static));
609 iter::zip(identity_substs.regions(), fr_substs.regions().map(|r| r.to_region_vid()));
611 UniversalRegionIndices { indices: global_mapping.chain(subst_mapping).collect() }
614 fn compute_inputs_and_output(
616 indices: &UniversalRegionIndices<'tcx>,
617 defining_ty: DefiningTy<'tcx>,
618 ) -> ty::Binder<'tcx, &'tcx ty::List<Ty<'tcx>>> {
619 let tcx = self.infcx.tcx;
621 DefiningTy::Closure(def_id, substs) => {
622 assert_eq!(self.mir_def.did.to_def_id(), def_id);
623 let closure_sig = substs.as_closure().sig();
624 let inputs_and_output = closure_sig.inputs_and_output();
625 let bound_vars = tcx.mk_bound_variable_kinds(
629 .chain(iter::once(ty::BoundVariableKind::Region(ty::BrEnv))),
631 let br = ty::BoundRegion {
632 var: ty::BoundVar::from_usize(bound_vars.len() - 1),
635 let env_region = ty::ReLateBound(ty::INNERMOST, br);
636 let closure_ty = tcx.closure_env_ty(def_id, substs, env_region).unwrap();
638 // The "inputs" of the closure in the
639 // signature appear as a tuple. The MIR side
640 // flattens this tuple.
641 let (&output, tuplized_inputs) =
642 inputs_and_output.skip_binder().split_last().unwrap();
643 assert_eq!(tuplized_inputs.len(), 1, "multiple closure inputs");
644 let inputs = match tuplized_inputs[0].kind() {
645 ty::Tuple(inputs) => inputs,
646 _ => bug!("closure inputs not a tuple: {:?}", tuplized_inputs[0]),
649 ty::Binder::bind_with_vars(
651 iter::once(closure_ty)
652 .chain(inputs.iter().map(|k| k.expect_ty()))
653 .chain(iter::once(output)),
659 DefiningTy::Generator(def_id, substs, movability) => {
660 assert_eq!(self.mir_def.did.to_def_id(), def_id);
661 let resume_ty = substs.as_generator().resume_ty();
662 let output = substs.as_generator().return_ty();
663 let generator_ty = tcx.mk_generator(def_id, substs, movability);
664 let inputs_and_output =
665 self.infcx.tcx.intern_type_list(&[generator_ty, resume_ty, output]);
666 ty::Binder::dummy(inputs_and_output)
669 DefiningTy::FnDef(def_id, _) => {
670 let sig = tcx.fn_sig(def_id);
671 let sig = indices.fold_to_region_vids(tcx, sig);
672 sig.inputs_and_output()
675 DefiningTy::Const(def_id, _) => {
676 // For a constant body, there are no inputs, and one
677 // "output" (the type of the constant).
678 assert_eq!(self.mir_def.did.to_def_id(), def_id);
679 let ty = tcx.type_of(self.mir_def.def_id_for_type_of());
680 let ty = indices.fold_to_region_vids(tcx, ty);
681 ty::Binder::dummy(tcx.intern_type_list(&[ty]))
684 DefiningTy::InlineConst(def_id, substs) => {
685 assert_eq!(self.mir_def.did.to_def_id(), def_id);
686 let ty = substs.as_inline_const().ty();
687 ty::Binder::dummy(tcx.intern_type_list(&[ty]))
693 trait InferCtxtExt<'tcx> {
694 fn replace_free_regions_with_nll_infer_vars<T>(
696 origin: NllRegionVariableOrigin,
700 T: TypeFoldable<'tcx>;
702 fn replace_bound_regions_with_nll_infer_vars<T>(
704 origin: NllRegionVariableOrigin,
705 all_outlive_scope: LocalDefId,
706 value: ty::Binder<'tcx, T>,
707 indices: &mut UniversalRegionIndices<'tcx>,
710 T: TypeFoldable<'tcx>;
712 fn replace_late_bound_regions_with_nll_infer_vars(
714 mir_def_id: LocalDefId,
715 indices: &mut UniversalRegionIndices<'tcx>,
719 impl<'cx, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'cx, 'tcx> {
720 fn replace_free_regions_with_nll_infer_vars<T>(
722 origin: NllRegionVariableOrigin,
726 T: TypeFoldable<'tcx>,
728 self.tcx.fold_regions(value, &mut false, |_region, _depth| self.next_nll_region_var(origin))
731 fn replace_bound_regions_with_nll_infer_vars<T>(
733 origin: NllRegionVariableOrigin,
734 all_outlive_scope: LocalDefId,
735 value: ty::Binder<'tcx, T>,
736 indices: &mut UniversalRegionIndices<'tcx>,
739 T: TypeFoldable<'tcx>,
742 "replace_bound_regions_with_nll_infer_vars(value={:?}, all_outlive_scope={:?})",
743 value, all_outlive_scope,
745 let (value, _map) = self.tcx.replace_late_bound_regions(value, |br| {
746 debug!("replace_bound_regions_with_nll_infer_vars: br={:?}", br);
747 let liberated_region = self.tcx.mk_region(ty::ReFree(ty::FreeRegion {
748 scope: all_outlive_scope.to_def_id(),
749 bound_region: br.kind,
751 let region_vid = self.next_nll_region_var(origin);
752 indices.insert_late_bound_region(liberated_region, region_vid.to_region_vid());
754 "replace_bound_regions_with_nll_infer_vars: liberated_region={:?} => {:?}",
755 liberated_region, region_vid
762 /// Finds late-bound regions that do not appear in the parameter listing and adds them to the
763 /// indices vector. Typically, we identify late-bound regions as we process the inputs and
764 /// outputs of the closure/function. However, sometimes there are late-bound regions which do
765 /// not appear in the fn parameters but which are nonetheless in scope. The simplest case of
766 /// this are unused functions, like fn foo<'a>() { } (see e.g., #51351). Despite not being used,
767 /// users can still reference these regions (e.g., let x: &'a u32 = &22;), so we need to create
768 /// entries for them and store them in the indices map. This code iterates over the complete
769 /// set of late-bound regions and checks for any that we have not yet seen, adding them to the
771 fn replace_late_bound_regions_with_nll_infer_vars(
773 mir_def_id: LocalDefId,
774 indices: &mut UniversalRegionIndices<'tcx>,
776 debug!("replace_late_bound_regions_with_nll_infer_vars(mir_def_id={:?})", mir_def_id);
777 let typeck_root_def_id = self.tcx.typeck_root_def_id(mir_def_id.to_def_id());
778 for_each_late_bound_region_defined_on(self.tcx, typeck_root_def_id, |r| {
779 debug!("replace_late_bound_regions_with_nll_infer_vars: r={:?}", r);
780 if !indices.indices.contains_key(&r) {
781 let region_vid = self.next_nll_region_var(FR);
782 indices.insert_late_bound_region(r, region_vid.to_region_vid());
788 impl<'tcx> UniversalRegionIndices<'tcx> {
789 /// Initially, the `UniversalRegionIndices` map contains only the
790 /// early-bound regions in scope. Once that is all setup, we come
791 /// in later and instantiate the late-bound regions, and then we
792 /// insert the `ReFree` version of those into the map as
793 /// well. These are used for error reporting.
794 fn insert_late_bound_region(&mut self, r: ty::Region<'tcx>, vid: ty::RegionVid) {
795 debug!("insert_late_bound_region({:?}, {:?})", r, vid);
796 self.indices.insert(r, vid);
799 /// Converts `r` into a local inference variable: `r` can either
800 /// by a `ReVar` (i.e., already a reference to an inference
801 /// variable) or it can be `'static` or some early-bound
802 /// region. This is useful when taking the results from
803 /// type-checking and trait-matching, which may sometimes
804 /// reference those regions from the `ParamEnv`. It is also used
805 /// during initialization. Relies on the `indices` map having been
806 /// fully initialized.
807 pub fn to_region_vid(&self, r: ty::Region<'tcx>) -> RegionVid {
808 if let ty::ReVar(..) = r {
814 .unwrap_or_else(|| bug!("cannot convert `{:?}` to a region vid", r))
818 /// Replaces all free regions in `value` with region vids, as
819 /// returned by `to_region_vid`.
820 pub fn fold_to_region_vids<T>(&self, tcx: TyCtxt<'tcx>, value: T) -> T
822 T: TypeFoldable<'tcx>,
824 tcx.fold_regions(value, &mut false, |region, _| {
825 tcx.mk_region(ty::ReVar(self.to_region_vid(region)))
830 /// Iterates over the late-bound regions defined on fn_def_id and
831 /// invokes `f` with the liberated form of each one.
832 fn for_each_late_bound_region_defined_on<'tcx>(
835 mut f: impl FnMut(ty::Region<'tcx>),
837 if let Some((owner, late_bounds)) = tcx.is_late_bound_map(fn_def_id.expect_local()) {
838 for &late_bound in late_bounds.iter() {
839 let hir_id = HirId { owner, local_id: late_bound };
840 let name = tcx.hir().name(hir_id);
841 let region_def_id = tcx.hir().local_def_id(hir_id);
842 let liberated_region = tcx.mk_region(ty::ReFree(ty::FreeRegion {
843 scope: owner.to_def_id(),
844 bound_region: ty::BoundRegionKind::BrNamed(region_def_id.to_def_id(), name),