//! Code to extract the universally quantified regions declared on a //! function and the relationships between them. For example: //! //! ``` //! fn foo<'a, 'b, 'c: 'b>() { } //! ``` //! //! here we would return a map assigning each of `{'a, 'b, 'c}` //! to an index, as well as the `FreeRegionMap` which can compute //! relationships between them. //! //! The code in this file doesn't *do anything* with those results; it //! just returns them for other code to use. use either::Either; use rustc_data_structures::fx::FxHashMap; use rustc_errors::Diagnostic; use rustc_hir as hir; use rustc_hir::def_id::{DefId, LocalDefId}; use rustc_hir::lang_items::LangItem; use rustc_hir::{BodyOwnerKind, HirId}; use rustc_index::vec::{Idx, IndexVec}; use rustc_infer::infer::{InferCtxt, NllRegionVariableOrigin}; use rustc_middle::ty::fold::TypeFoldable; use rustc_middle::ty::{ self, DefIdTree, InlineConstSubsts, InlineConstSubstsParts, RegionVid, Ty, TyCtxt, }; use rustc_middle::ty::{InternalSubsts, SubstsRef}; use std::iter; use crate::nll::ToRegionVid; #[derive(Debug)] pub struct UniversalRegions<'tcx> { indices: UniversalRegionIndices<'tcx>, /// The vid assigned to `'static` pub fr_static: RegionVid, /// A special region vid created to represent the current MIR fn /// body. It will outlive the entire CFG but it will not outlive /// any other universal regions. pub fr_fn_body: RegionVid, /// We create region variables such that they are ordered by their /// `RegionClassification`. The first block are globals, then /// externals, then locals. So, things from: /// - `FIRST_GLOBAL_INDEX..first_extern_index` are global, /// - `first_extern_index..first_local_index` are external, /// - `first_local_index..num_universals` are local. first_extern_index: usize, /// See `first_extern_index`. first_local_index: usize, /// The total number of universal region variables instantiated. num_universals: usize, /// The "defining" type for this function, with all universal /// regions instantiated. For a closure or generator, this is the /// closure type, but for a top-level function it's the `FnDef`. pub defining_ty: DefiningTy<'tcx>, /// The return type of this function, with all regions replaced by /// their universal `RegionVid` equivalents. /// /// N.B., associated types in this type have not been normalized, /// as the name suggests. =) pub unnormalized_output_ty: Ty<'tcx>, /// The fully liberated input types of this function, with all /// regions replaced by their universal `RegionVid` equivalents. /// /// N.B., associated types in these types have not been normalized, /// as the name suggests. =) pub unnormalized_input_tys: &'tcx [Ty<'tcx>], pub yield_ty: Option>, } /// The "defining type" for this MIR. The key feature of the "defining /// type" is that it contains the information needed to derive all the /// universal regions that are in scope as well as the types of the /// inputs/output from the MIR. In general, early-bound universal /// regions appear free in the defining type and late-bound regions /// appear bound in the signature. #[derive(Copy, Clone, Debug)] pub enum DefiningTy<'tcx> { /// The MIR is a closure. The signature is found via /// `ClosureSubsts::closure_sig_ty`. Closure(DefId, SubstsRef<'tcx>), /// The MIR is a generator. The signature is that generators take /// no parameters and return the result of /// `ClosureSubsts::generator_return_ty`. Generator(DefId, SubstsRef<'tcx>, hir::Movability), /// The MIR is a fn item with the given `DefId` and substs. The signature /// of the function can be bound then with the `fn_sig` query. FnDef(DefId, SubstsRef<'tcx>), /// The MIR represents some form of constant. The signature then /// is that it has no inputs and a single return value, which is /// the value of the constant. Const(DefId, SubstsRef<'tcx>), /// The MIR represents an inline const. The signature has no inputs and a /// single return value found via `InlineConstSubsts::ty`. InlineConst(DefId, SubstsRef<'tcx>), } impl<'tcx> DefiningTy<'tcx> { /// Returns a list of all the upvar types for this MIR. If this is /// not a closure or generator, there are no upvars, and hence it /// will be an empty list. The order of types in this list will /// match up with the upvar order in the HIR, typesystem, and MIR. pub fn upvar_tys(self) -> impl Iterator> + 'tcx { match self { DefiningTy::Closure(_, substs) => Either::Left(substs.as_closure().upvar_tys()), DefiningTy::Generator(_, substs, _) => { Either::Right(Either::Left(substs.as_generator().upvar_tys())) } DefiningTy::FnDef(..) | DefiningTy::Const(..) | DefiningTy::InlineConst(..) => { Either::Right(Either::Right(iter::empty())) } } } /// Number of implicit inputs -- notably the "environment" /// parameter for closures -- that appear in MIR but not in the /// user's code. pub fn implicit_inputs(self) -> usize { match self { DefiningTy::Closure(..) | DefiningTy::Generator(..) => 1, DefiningTy::FnDef(..) | DefiningTy::Const(..) | DefiningTy::InlineConst(..) => 0, } } pub fn is_fn_def(&self) -> bool { matches!(*self, DefiningTy::FnDef(..)) } pub fn is_const(&self) -> bool { matches!(*self, DefiningTy::Const(..) | DefiningTy::InlineConst(..)) } pub fn def_id(&self) -> DefId { match *self { DefiningTy::Closure(def_id, ..) | DefiningTy::Generator(def_id, ..) | DefiningTy::FnDef(def_id, ..) | DefiningTy::Const(def_id, ..) | DefiningTy::InlineConst(def_id, ..) => def_id, } } } #[derive(Debug)] struct UniversalRegionIndices<'tcx> { /// For those regions that may appear in the parameter environment /// ('static and early-bound regions), we maintain a map from the /// `ty::Region` to the internal `RegionVid` we are using. This is /// used because trait matching and type-checking will feed us /// region constraints that reference those regions and we need to /// be able to map them our internal `RegionVid`. This is /// basically equivalent to an `InternalSubsts`, except that it also /// contains an entry for `ReStatic` -- it might be nice to just /// use a substs, and then handle `ReStatic` another way. indices: FxHashMap, RegionVid>, } #[derive(Debug, PartialEq)] pub enum RegionClassification { /// A **global** region is one that can be named from /// anywhere. There is only one, `'static`. Global, /// An **external** region is only relevant for /// closures, generators, and inline consts. In that /// case, it refers to regions that are free in the type /// -- basically, something bound in the surrounding context. /// /// Consider this example: /// /// ```ignore (pseudo-rust) /// fn foo<'a, 'b>(a: &'a u32, b: &'b u32, c: &'static u32) { /// let closure = for<'x> |x: &'x u32| { .. }; /// // ^^^^^^^ pretend this were legal syntax /// // for declaring a late-bound region in /// // a closure signature /// } /// ``` /// /// Here, the lifetimes `'a` and `'b` would be **external** to the /// closure. /// /// If we are not analyzing a closure/generator/inline-const, /// there are no external lifetimes. External, /// A **local** lifetime is one about which we know the full set /// of relevant constraints (that is, relationships to other named /// regions). For a closure, this includes any region bound in /// the closure's signature. For a fn item, this includes all /// regions other than global ones. /// /// Continuing with the example from `External`, if we were /// analyzing the closure, then `'x` would be local (and `'a` and /// `'b` are external). If we are analyzing the function item /// `foo`, then `'a` and `'b` are local (and `'x` is not in /// scope). Local, } const FIRST_GLOBAL_INDEX: usize = 0; impl<'tcx> UniversalRegions<'tcx> { /// Creates a new and fully initialized `UniversalRegions` that /// contains indices for all the free regions found in the given /// MIR -- that is, all the regions that appear in the function's /// signature. This will also compute the relationships that are /// known between those regions. pub fn new( infcx: &InferCtxt<'tcx>, mir_def: ty::WithOptConstParam, param_env: ty::ParamEnv<'tcx>, ) -> Self { let tcx = infcx.tcx; let mir_hir_id = tcx.hir().local_def_id_to_hir_id(mir_def.did); UniversalRegionsBuilder { infcx, mir_def, mir_hir_id, param_env }.build() } /// Given a reference to a closure type, extracts all the values /// from its free regions and returns a vector with them. This is /// used when the closure's creator checks that the /// `ClosureRegionRequirements` are met. The requirements from /// `ClosureRegionRequirements` are expressed in terms of /// `RegionVid` entries that map into the returned vector `V`: so /// if the `ClosureRegionRequirements` contains something like /// `'1: '2`, then the caller would impose the constraint that /// `V[1]: V[2]`. pub fn closure_mapping( tcx: TyCtxt<'tcx>, closure_substs: SubstsRef<'tcx>, expected_num_vars: usize, closure_def_id: LocalDefId, ) -> IndexVec> { let mut region_mapping = IndexVec::with_capacity(expected_num_vars); region_mapping.push(tcx.lifetimes.re_static); tcx.for_each_free_region(&closure_substs, |fr| { region_mapping.push(fr); }); for_each_late_bound_region_in_recursive_scope(tcx, tcx.local_parent(closure_def_id), |r| { region_mapping.push(r); }); assert_eq!( region_mapping.len(), expected_num_vars, "index vec had unexpected number of variables" ); region_mapping } /// Returns `true` if `r` is a member of this set of universal regions. pub fn is_universal_region(&self, r: RegionVid) -> bool { (FIRST_GLOBAL_INDEX..self.num_universals).contains(&r.index()) } /// Classifies `r` as a universal region, returning `None` if this /// is not a member of this set of universal regions. pub fn region_classification(&self, r: RegionVid) -> Option { let index = r.index(); if (FIRST_GLOBAL_INDEX..self.first_extern_index).contains(&index) { Some(RegionClassification::Global) } else if (self.first_extern_index..self.first_local_index).contains(&index) { Some(RegionClassification::External) } else if (self.first_local_index..self.num_universals).contains(&index) { Some(RegionClassification::Local) } else { None } } /// Returns an iterator over all the RegionVids corresponding to /// universally quantified free regions. pub fn universal_regions(&self) -> impl Iterator { (FIRST_GLOBAL_INDEX..self.num_universals).map(RegionVid::new) } /// Returns `true` if `r` is classified as an local region. pub fn is_local_free_region(&self, r: RegionVid) -> bool { self.region_classification(r) == Some(RegionClassification::Local) } /// Returns the number of universal regions created in any category. pub fn len(&self) -> usize { self.num_universals } /// Returns the number of global plus external universal regions. /// For closures, these are the regions that appear free in the /// closure type (versus those bound in the closure /// signature). They are therefore the regions between which the /// closure may impose constraints that its creator must verify. pub fn num_global_and_external_regions(&self) -> usize { self.first_local_index } /// Gets an iterator over all the early-bound regions that have names. pub fn named_universal_regions<'s>( &'s self, ) -> impl Iterator, ty::RegionVid)> + 's { self.indices.indices.iter().map(|(&r, &v)| (r, v)) } /// See `UniversalRegionIndices::to_region_vid`. pub fn to_region_vid(&self, r: ty::Region<'tcx>) -> RegionVid { self.indices.to_region_vid(r) } /// As part of the NLL unit tests, you can annotate a function with /// `#[rustc_regions]`, and we will emit information about the region /// inference context and -- in particular -- the external constraints /// that this region imposes on others. The methods in this file /// handle the part about dumping the inference context internal /// state. pub(crate) fn annotate(&self, tcx: TyCtxt<'tcx>, err: &mut Diagnostic) { match self.defining_ty { DefiningTy::Closure(def_id, substs) => { err.note(&format!( "defining type: {} with closure substs {:#?}", tcx.def_path_str_with_substs(def_id, substs), &substs[tcx.generics_of(def_id).parent_count..], )); // FIXME: It'd be nice to print the late-bound regions // here, but unfortunately these wind up stored into // tests, and the resulting print-outs include def-ids // and other things that are not stable across tests! // So we just include the region-vid. Annoying. for_each_late_bound_region_in_recursive_scope(tcx, def_id.expect_local(), |r| { err.note(&format!("late-bound region is {:?}", self.to_region_vid(r))); }); } DefiningTy::Generator(def_id, substs, _) => { err.note(&format!( "defining type: {} with generator substs {:#?}", tcx.def_path_str_with_substs(def_id, substs), &substs[tcx.generics_of(def_id).parent_count..], )); // FIXME: As above, we'd like to print out the region // `r` but doing so is not stable across architectures // and so forth. for_each_late_bound_region_in_recursive_scope(tcx, def_id.expect_local(), |r| { err.note(&format!("late-bound region is {:?}", self.to_region_vid(r))); }); } DefiningTy::FnDef(def_id, substs) => { err.note(&format!( "defining type: {}", tcx.def_path_str_with_substs(def_id, substs), )); } DefiningTy::Const(def_id, substs) => { err.note(&format!( "defining constant type: {}", tcx.def_path_str_with_substs(def_id, substs), )); } DefiningTy::InlineConst(def_id, substs) => { err.note(&format!( "defining inline constant type: {}", tcx.def_path_str_with_substs(def_id, substs), )); } } } } struct UniversalRegionsBuilder<'cx, 'tcx> { infcx: &'cx InferCtxt<'tcx>, mir_def: ty::WithOptConstParam, mir_hir_id: HirId, param_env: ty::ParamEnv<'tcx>, } const FR: NllRegionVariableOrigin = NllRegionVariableOrigin::FreeRegion; impl<'cx, 'tcx> UniversalRegionsBuilder<'cx, 'tcx> { fn build(self) -> UniversalRegions<'tcx> { debug!("build(mir_def={:?})", self.mir_def); let param_env = self.param_env; debug!("build: param_env={:?}", param_env); assert_eq!(FIRST_GLOBAL_INDEX, self.infcx.num_region_vars()); // Create the "global" region that is always free in all contexts: 'static. let fr_static = self.infcx.next_nll_region_var(FR).to_region_vid(); // We've now added all the global regions. The next ones we // add will be external. let first_extern_index = self.infcx.num_region_vars(); let defining_ty = self.defining_ty(); debug!("build: defining_ty={:?}", defining_ty); let mut indices = self.compute_indices(fr_static, defining_ty); debug!("build: indices={:?}", indices); let typeck_root_def_id = self.infcx.tcx.typeck_root_def_id(self.mir_def.did.to_def_id()); // If this is a 'root' body (not a closure/generator/inline const), then // there are no extern regions, so the local regions start at the same // position as the (empty) sub-list of extern regions let first_local_index = if self.mir_def.did.to_def_id() == typeck_root_def_id { first_extern_index } else { // If this is a closure, generator, or inline-const, then the late-bound regions from the enclosing // function/closures are actually external regions to us. For example, here, 'a is not local // to the closure c (although it is local to the fn foo): // fn foo<'a>() { // let c = || { let x: &'a u32 = ...; } // } for_each_late_bound_region_in_recursive_scope( self.infcx.tcx, self.infcx.tcx.local_parent(self.mir_def.did), |r| { debug!(?r); if !indices.indices.contains_key(&r) { let region_vid = self.infcx.next_nll_region_var(FR); debug!(?region_vid); indices.insert_late_bound_region(r, region_vid.to_region_vid()); } }, ); // Any regions created during the execution of `defining_ty` or during the above // late-bound region replacement are all considered 'extern' regions self.infcx.num_region_vars() }; // "Liberate" the late-bound regions. These correspond to // "local" free regions. let bound_inputs_and_output = self.compute_inputs_and_output(&indices, defining_ty); let inputs_and_output = self.infcx.replace_bound_regions_with_nll_infer_vars( FR, self.mir_def.did, bound_inputs_and_output, &mut indices, ); // Converse of above, if this is a function/closure then the late-bound regions declared on its // signature are local. for_each_late_bound_region_in_item(self.infcx.tcx, self.mir_def.did, |r| { debug!(?r); if !indices.indices.contains_key(&r) { let region_vid = self.infcx.next_nll_region_var(FR); debug!(?region_vid); indices.insert_late_bound_region(r, region_vid.to_region_vid()); } }); let (unnormalized_output_ty, mut unnormalized_input_tys) = inputs_and_output.split_last().unwrap(); // C-variadic fns also have a `VaList` input that's not listed in the signature // (as it's created inside the body itself, not passed in from outside). if let DefiningTy::FnDef(def_id, _) = defining_ty { if self.infcx.tcx.fn_sig(def_id).c_variadic() { let va_list_did = self.infcx.tcx.require_lang_item( LangItem::VaList, Some(self.infcx.tcx.def_span(self.mir_def.did)), ); let region = self .infcx .tcx .mk_region(ty::ReVar(self.infcx.next_nll_region_var(FR).to_region_vid())); let va_list_ty = self .infcx .tcx .bound_type_of(va_list_did) .subst(self.infcx.tcx, &[region.into()]); unnormalized_input_tys = self.infcx.tcx.mk_type_list( unnormalized_input_tys.iter().copied().chain(iter::once(va_list_ty)), ); } } let fr_fn_body = self.infcx.next_nll_region_var(FR).to_region_vid(); let num_universals = self.infcx.num_region_vars(); debug!("build: global regions = {}..{}", FIRST_GLOBAL_INDEX, first_extern_index); debug!("build: extern regions = {}..{}", first_extern_index, first_local_index); debug!("build: local regions = {}..{}", first_local_index, num_universals); let yield_ty = match defining_ty { DefiningTy::Generator(_, substs, _) => Some(substs.as_generator().yield_ty()), _ => None, }; UniversalRegions { indices, fr_static, fr_fn_body, first_extern_index, first_local_index, num_universals, defining_ty, unnormalized_output_ty: *unnormalized_output_ty, unnormalized_input_tys, yield_ty, } } /// Returns the "defining type" of the current MIR; /// see `DefiningTy` for details. fn defining_ty(&self) -> DefiningTy<'tcx> { let tcx = self.infcx.tcx; let typeck_root_def_id = tcx.typeck_root_def_id(self.mir_def.did.to_def_id()); match tcx.hir().body_owner_kind(self.mir_def.did) { BodyOwnerKind::Closure | BodyOwnerKind::Fn => { let defining_ty = if self.mir_def.did.to_def_id() == typeck_root_def_id { tcx.type_of(typeck_root_def_id) } else { let tables = tcx.typeck(self.mir_def.did); tables.node_type(self.mir_hir_id) }; debug!("defining_ty (pre-replacement): {:?}", defining_ty); let defining_ty = self.infcx.replace_free_regions_with_nll_infer_vars(FR, defining_ty); match *defining_ty.kind() { ty::Closure(def_id, substs) => DefiningTy::Closure(def_id, substs), ty::Generator(def_id, substs, movability) => { DefiningTy::Generator(def_id, substs, movability) } ty::FnDef(def_id, substs) => DefiningTy::FnDef(def_id, substs), _ => span_bug!( tcx.def_span(self.mir_def.did), "expected defining type for `{:?}`: `{:?}`", self.mir_def.did, defining_ty ), } } BodyOwnerKind::Const | BodyOwnerKind::Static(..) => { let identity_substs = InternalSubsts::identity_for_item(tcx, typeck_root_def_id); if self.mir_def.did.to_def_id() == typeck_root_def_id { let substs = self.infcx.replace_free_regions_with_nll_infer_vars(FR, identity_substs); DefiningTy::Const(self.mir_def.did.to_def_id(), substs) } else { let ty = tcx.typeck(self.mir_def.did).node_type(self.mir_hir_id); let substs = InlineConstSubsts::new( tcx, InlineConstSubstsParts { parent_substs: identity_substs, ty }, ) .substs; let substs = self.infcx.replace_free_regions_with_nll_infer_vars(FR, substs); DefiningTy::InlineConst(self.mir_def.did.to_def_id(), substs) } } } } /// Builds a hashmap that maps from the universal regions that are /// in scope (as a `ty::Region<'tcx>`) to their indices (as a /// `RegionVid`). The map returned by this function contains only /// the early-bound regions. fn compute_indices( &self, fr_static: RegionVid, defining_ty: DefiningTy<'tcx>, ) -> UniversalRegionIndices<'tcx> { let tcx = self.infcx.tcx; let typeck_root_def_id = tcx.typeck_root_def_id(self.mir_def.did.to_def_id()); let identity_substs = InternalSubsts::identity_for_item(tcx, typeck_root_def_id); let fr_substs = match defining_ty { DefiningTy::Closure(_, substs) | DefiningTy::Generator(_, substs, _) | DefiningTy::InlineConst(_, substs) => { // In the case of closures, we rely on the fact that // the first N elements in the ClosureSubsts are // inherited from the `typeck_root_def_id`. // Therefore, when we zip together (below) with // `identity_substs`, we will get only those regions // that correspond to early-bound regions declared on // the `typeck_root_def_id`. assert!(substs.len() >= identity_substs.len()); assert_eq!(substs.regions().count(), identity_substs.regions().count()); substs } DefiningTy::FnDef(_, substs) | DefiningTy::Const(_, substs) => substs, }; let global_mapping = iter::once((tcx.lifetimes.re_static, fr_static)); let subst_mapping = iter::zip(identity_substs.regions(), fr_substs.regions().map(|r| r.to_region_vid())); UniversalRegionIndices { indices: global_mapping.chain(subst_mapping).collect() } } fn compute_inputs_and_output( &self, indices: &UniversalRegionIndices<'tcx>, defining_ty: DefiningTy<'tcx>, ) -> ty::Binder<'tcx, &'tcx ty::List>> { let tcx = self.infcx.tcx; match defining_ty { DefiningTy::Closure(def_id, substs) => { assert_eq!(self.mir_def.did.to_def_id(), def_id); let closure_sig = substs.as_closure().sig(); let inputs_and_output = closure_sig.inputs_and_output(); let bound_vars = tcx.mk_bound_variable_kinds( inputs_and_output .bound_vars() .iter() .chain(iter::once(ty::BoundVariableKind::Region(ty::BrEnv))), ); let br = ty::BoundRegion { var: ty::BoundVar::from_usize(bound_vars.len() - 1), kind: ty::BrEnv, }; let env_region = ty::ReLateBound(ty::INNERMOST, br); let closure_ty = tcx.closure_env_ty(def_id, substs, env_region).unwrap(); // The "inputs" of the closure in the // signature appear as a tuple. The MIR side // flattens this tuple. let (&output, tuplized_inputs) = inputs_and_output.skip_binder().split_last().unwrap(); assert_eq!(tuplized_inputs.len(), 1, "multiple closure inputs"); let &ty::Tuple(inputs) = tuplized_inputs[0].kind() else { bug!("closure inputs not a tuple: {:?}", tuplized_inputs[0]); }; ty::Binder::bind_with_vars( tcx.mk_type_list( iter::once(closure_ty).chain(inputs).chain(iter::once(output)), ), bound_vars, ) } DefiningTy::Generator(def_id, substs, movability) => { assert_eq!(self.mir_def.did.to_def_id(), def_id); let resume_ty = substs.as_generator().resume_ty(); let output = substs.as_generator().return_ty(); let generator_ty = tcx.mk_generator(def_id, substs, movability); let inputs_and_output = self.infcx.tcx.intern_type_list(&[generator_ty, resume_ty, output]); ty::Binder::dummy(inputs_and_output) } DefiningTy::FnDef(def_id, _) => { let sig = tcx.fn_sig(def_id); let sig = indices.fold_to_region_vids(tcx, sig); sig.inputs_and_output() } DefiningTy::Const(def_id, _) => { // For a constant body, there are no inputs, and one // "output" (the type of the constant). assert_eq!(self.mir_def.did.to_def_id(), def_id); let ty = tcx.type_of(self.mir_def.def_id_for_type_of()); let ty = indices.fold_to_region_vids(tcx, ty); ty::Binder::dummy(tcx.intern_type_list(&[ty])) } DefiningTy::InlineConst(def_id, substs) => { assert_eq!(self.mir_def.did.to_def_id(), def_id); let ty = substs.as_inline_const().ty(); ty::Binder::dummy(tcx.intern_type_list(&[ty])) } } } } trait InferCtxtExt<'tcx> { fn replace_free_regions_with_nll_infer_vars( &self, origin: NllRegionVariableOrigin, value: T, ) -> T where T: TypeFoldable<'tcx>; fn replace_bound_regions_with_nll_infer_vars( &self, origin: NllRegionVariableOrigin, all_outlive_scope: LocalDefId, value: ty::Binder<'tcx, T>, indices: &mut UniversalRegionIndices<'tcx>, ) -> T where T: TypeFoldable<'tcx>; fn replace_late_bound_regions_with_nll_infer_vars_in_recursive_scope( &self, mir_def_id: LocalDefId, indices: &mut UniversalRegionIndices<'tcx>, ); fn replace_late_bound_regions_with_nll_infer_vars_in_item( &self, mir_def_id: LocalDefId, indices: &mut UniversalRegionIndices<'tcx>, ); } impl<'tcx> InferCtxtExt<'tcx> for InferCtxt<'tcx> { fn replace_free_regions_with_nll_infer_vars( &self, origin: NllRegionVariableOrigin, value: T, ) -> T where T: TypeFoldable<'tcx>, { self.tcx.fold_regions(value, |_region, _depth| self.next_nll_region_var(origin)) } #[instrument(level = "debug", skip(self, indices))] fn replace_bound_regions_with_nll_infer_vars( &self, origin: NllRegionVariableOrigin, all_outlive_scope: LocalDefId, value: ty::Binder<'tcx, T>, indices: &mut UniversalRegionIndices<'tcx>, ) -> T where T: TypeFoldable<'tcx>, { let (value, _map) = self.tcx.replace_late_bound_regions(value, |br| { debug!(?br); let liberated_region = self.tcx.mk_region(ty::ReFree(ty::FreeRegion { scope: all_outlive_scope.to_def_id(), bound_region: br.kind, })); let region_vid = self.next_nll_region_var(origin); indices.insert_late_bound_region(liberated_region, region_vid.to_region_vid()); debug!(?liberated_region, ?region_vid); region_vid }); value } /// Finds late-bound regions that do not appear in the parameter listing and adds them to the /// indices vector. Typically, we identify late-bound regions as we process the inputs and /// outputs of the closure/function. However, sometimes there are late-bound regions which do /// not appear in the fn parameters but which are nonetheless in scope. The simplest case of /// this are unused functions, like fn foo<'a>() { } (see e.g., #51351). Despite not being used, /// users can still reference these regions (e.g., let x: &'a u32 = &22;), so we need to create /// entries for them and store them in the indices map. This code iterates over the complete /// set of late-bound regions and checks for any that we have not yet seen, adding them to the /// inputs vector. #[instrument(skip(self, indices))] fn replace_late_bound_regions_with_nll_infer_vars_in_recursive_scope( &self, mir_def_id: LocalDefId, indices: &mut UniversalRegionIndices<'tcx>, ) { for_each_late_bound_region_in_recursive_scope(self.tcx, mir_def_id, |r| { debug!(?r); if !indices.indices.contains_key(&r) { let region_vid = self.next_nll_region_var(FR); debug!(?region_vid); indices.insert_late_bound_region(r, region_vid.to_region_vid()); } }); } #[instrument(skip(self, indices))] fn replace_late_bound_regions_with_nll_infer_vars_in_item( &self, mir_def_id: LocalDefId, indices: &mut UniversalRegionIndices<'tcx>, ) { for_each_late_bound_region_in_item(self.tcx, mir_def_id, |r| { debug!(?r); if !indices.indices.contains_key(&r) { let region_vid = self.next_nll_region_var(FR); debug!(?region_vid); indices.insert_late_bound_region(r, region_vid.to_region_vid()); } }); } } impl<'tcx> UniversalRegionIndices<'tcx> { /// Initially, the `UniversalRegionIndices` map contains only the /// early-bound regions in scope. Once that is all setup, we come /// in later and instantiate the late-bound regions, and then we /// insert the `ReFree` version of those into the map as /// well. These are used for error reporting. fn insert_late_bound_region(&mut self, r: ty::Region<'tcx>, vid: ty::RegionVid) { debug!("insert_late_bound_region({:?}, {:?})", r, vid); self.indices.insert(r, vid); } /// Converts `r` into a local inference variable: `r` can either /// by a `ReVar` (i.e., already a reference to an inference /// variable) or it can be `'static` or some early-bound /// region. This is useful when taking the results from /// type-checking and trait-matching, which may sometimes /// reference those regions from the `ParamEnv`. It is also used /// during initialization. Relies on the `indices` map having been /// fully initialized. pub fn to_region_vid(&self, r: ty::Region<'tcx>) -> RegionVid { if let ty::ReVar(..) = *r { r.to_region_vid() } else { *self .indices .get(&r) .unwrap_or_else(|| bug!("cannot convert `{:?}` to a region vid", r)) } } /// Replaces all free regions in `value` with region vids, as /// returned by `to_region_vid`. pub fn fold_to_region_vids(&self, tcx: TyCtxt<'tcx>, value: T) -> T where T: TypeFoldable<'tcx>, { tcx.fold_regions(value, |region, _| tcx.mk_region(ty::ReVar(self.to_region_vid(region)))) } } /// Iterates over the late-bound regions defined on `mir_def_id` and all of its /// parents, up to the typeck root, and invokes `f` with the liberated form /// of each one. fn for_each_late_bound_region_in_recursive_scope<'tcx>( tcx: TyCtxt<'tcx>, mut mir_def_id: LocalDefId, mut f: impl FnMut(ty::Region<'tcx>), ) { let typeck_root_def_id = tcx.typeck_root_def_id(mir_def_id.to_def_id()); // Walk up the tree, collecting late-bound regions until we hit the typeck root loop { for_each_late_bound_region_in_item(tcx, mir_def_id, &mut f); if mir_def_id.to_def_id() == typeck_root_def_id { break; } else { mir_def_id = tcx.local_parent(mir_def_id); } } } /// Iterates over the late-bound regions defined on `mir_def_id` and all of its /// parents, up to the typeck root, and invokes `f` with the liberated form /// of each one. fn for_each_late_bound_region_in_item<'tcx>( tcx: TyCtxt<'tcx>, mir_def_id: LocalDefId, mut f: impl FnMut(ty::Region<'tcx>), ) { if !tcx.def_kind(mir_def_id).is_fn_like() { return; } for bound_var in tcx.late_bound_vars(tcx.hir().local_def_id_to_hir_id(mir_def_id)) { let ty::BoundVariableKind::Region(bound_region) = bound_var else { continue; }; let liberated_region = tcx .mk_region(ty::ReFree(ty::FreeRegion { scope: mir_def_id.to_def_id(), bound_region })); f(liberated_region); } }