| //! 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 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; |
| use rustc_index::IndexVec; |
| use rustc_infer::infer::NllRegionVariableOrigin; |
| use rustc_middle::ty::fold::TypeFoldable; |
| use rustc_middle::ty::print::with_no_trimmed_paths; |
| use rustc_middle::ty::{self, InlineConstArgs, InlineConstArgsParts, RegionVid, Ty, TyCtxt}; |
| use rustc_middle::ty::{GenericArgs, GenericArgsRef}; |
| use rustc_span::symbol::{kw, sym}; |
| use rustc_span::Symbol; |
| use std::iter; |
| |
| use crate::renumber::RegionCtxt; |
| use crate::BorrowckInferCtxt; |
| |
| #[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 coroutine, 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<Ty<'tcx>>, |
| } |
| |
| /// 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 |
| /// `ClosureArgs::closure_sig_ty`. |
| Closure(DefId, GenericArgsRef<'tcx>), |
| |
| /// The MIR is a coroutine. The signature is that coroutines take |
| /// no parameters and return the result of |
| /// `ClosureArgs::coroutine_return_ty`. |
| Coroutine(DefId, GenericArgsRef<'tcx>, hir::Movability), |
| |
| /// The MIR is a fn item with the given `DefId` and args. The signature |
| /// of the function can be bound then with the `fn_sig` query. |
| FnDef(DefId, GenericArgsRef<'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, GenericArgsRef<'tcx>), |
| |
| /// The MIR represents an inline const. The signature has no inputs and a |
| /// single return value found via `InlineConstArgs::ty`. |
| InlineConst(DefId, GenericArgsRef<'tcx>), |
| } |
| |
| impl<'tcx> DefiningTy<'tcx> { |
| /// Returns a list of all the upvar types for this MIR. If this is |
| /// not a closure or coroutine, 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) -> &'tcx ty::List<Ty<'tcx>> { |
| match self { |
| DefiningTy::Closure(_, args) => args.as_closure().upvar_tys(), |
| DefiningTy::Coroutine(_, args, _) => args.as_coroutine().upvar_tys(), |
| DefiningTy::FnDef(..) | DefiningTy::Const(..) | DefiningTy::InlineConst(..) => { |
| ty::List::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::Coroutine(..) => 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::Coroutine(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 to our internal `RegionVid`. This is |
| /// basically equivalent to an `GenericArgs`, except that it also |
| /// contains an entry for `ReStatic` -- it might be nice to just |
| /// use an args, and then handle `ReStatic` another way. |
| indices: FxHashMap<ty::Region<'tcx>, RegionVid>, |
| |
| /// The vid assigned to `'static`. Used only for diagnostics. |
| pub fr_static: 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, coroutines, 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/coroutine/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: &BorrowckInferCtxt<'_, 'tcx>, |
| mir_def: LocalDefId, |
| param_env: ty::ParamEnv<'tcx>, |
| ) -> Self { |
| UniversalRegionsBuilder { infcx, mir_def, 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_args: GenericArgsRef<'tcx>, |
| expected_num_vars: usize, |
| closure_def_id: LocalDefId, |
| ) -> IndexVec<RegionVid, ty::Region<'tcx>> { |
| let mut region_mapping = IndexVec::with_capacity(expected_num_vars); |
| region_mapping.push(tcx.lifetimes.re_static); |
| tcx.for_each_free_region(&closure_args, |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<RegionClassification> { |
| 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<Item = RegionVid> { |
| (FIRST_GLOBAL_INDEX..self.num_universals).map(RegionVid::from_usize) |
| } |
| |
| /// Returns `true` if `r` is classified as a 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. |
| /// Iteration order may be unstable, so this should only be used when |
| /// iteration order doesn't affect anything |
| #[allow(rustc::potential_query_instability)] |
| pub fn named_universal_regions<'s>( |
| &'s self, |
| ) -> impl Iterator<Item = (ty::Region<'tcx>, 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, args) => { |
| let v = with_no_trimmed_paths!( |
| args[tcx.generics_of(def_id).parent_count..] |
| .iter() |
| .map(|arg| arg.to_string()) |
| .collect::<Vec<_>>() |
| ); |
| err.note(format!( |
| "defining type: {} with closure args [\n {},\n]", |
| tcx.def_path_str_with_args(def_id, args), |
| v.join(",\n "), |
| )); |
| |
| // 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::Coroutine(def_id, args, _) => { |
| let v = with_no_trimmed_paths!( |
| args[tcx.generics_of(def_id).parent_count..] |
| .iter() |
| .map(|arg| arg.to_string()) |
| .collect::<Vec<_>>() |
| ); |
| err.note(format!( |
| "defining type: {} with coroutine args [\n {},\n]", |
| tcx.def_path_str_with_args(def_id, args), |
| v.join(",\n "), |
| )); |
| |
| // 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, args) => { |
| err.note(format!("defining type: {}", tcx.def_path_str_with_args(def_id, args),)); |
| } |
| DefiningTy::Const(def_id, args) => { |
| err.note(format!( |
| "defining constant type: {}", |
| tcx.def_path_str_with_args(def_id, args), |
| )); |
| } |
| DefiningTy::InlineConst(def_id, args) => { |
| err.note(format!( |
| "defining inline constant type: {}", |
| tcx.def_path_str_with_args(def_id, args), |
| )); |
| } |
| } |
| } |
| } |
| |
| struct UniversalRegionsBuilder<'cx, 'tcx> { |
| infcx: &'cx BorrowckInferCtxt<'cx, 'tcx>, |
| mir_def: LocalDefId, |
| 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, || RegionCtxt::Free(kw::Static)).as_var(); |
| |
| // 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.to_def_id()); |
| |
| // If this is a 'root' body (not a closure/coroutine/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.to_def_id() == typeck_root_def_id { |
| first_extern_index |
| } else { |
| // If this is a closure, coroutine, 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), |
| |r| { |
| debug!(?r); |
| if !indices.indices.contains_key(&r) { |
| let region_vid = { |
| let name = r.get_name_or_anon(); |
| self.infcx.next_nll_region_var(FR, || RegionCtxt::LateBound(name)) |
| }; |
| |
| debug!(?region_vid); |
| indices.insert_late_bound_region(r, region_vid.as_var()); |
| } |
| }, |
| ); |
| |
| // 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, |
| 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, |r| { |
| debug!(?r); |
| if !indices.indices.contains_key(&r) { |
| let region_vid = { |
| let name = r.get_name_or_anon(); |
| self.infcx.next_nll_region_var(FR, || RegionCtxt::LateBound(name)) |
| }; |
| |
| debug!(?region_vid); |
| indices.insert_late_bound_region(r, region_vid.as_var()); |
| } |
| }); |
| |
| 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).skip_binder().c_variadic() { |
| let va_list_did = self.infcx.tcx.require_lang_item( |
| LangItem::VaList, |
| Some(self.infcx.tcx.def_span(self.mir_def)), |
| ); |
| |
| let reg_vid = self |
| .infcx |
| .next_nll_region_var(FR, || RegionCtxt::Free(Symbol::intern("c-variadic"))) |
| .as_var(); |
| |
| let region = ty::Region::new_var(self.infcx.tcx, reg_vid); |
| let va_list_ty = self |
| .infcx |
| .tcx |
| .type_of(va_list_did) |
| .instantiate(self.infcx.tcx, &[region.into()]); |
| |
| unnormalized_input_tys = self.infcx.tcx.mk_type_list_from_iter( |
| unnormalized_input_tys.iter().copied().chain(iter::once(va_list_ty)), |
| ); |
| } |
| } |
| |
| let fr_fn_body = self |
| .infcx |
| .next_nll_region_var(FR, || RegionCtxt::Free(Symbol::intern("fn_body"))) |
| .as_var(); |
| |
| 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::Coroutine(_, args, _) => Some(args.as_coroutine().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.to_def_id()); |
| |
| match tcx.hir().body_owner_kind(self.mir_def) { |
| BodyOwnerKind::Closure | BodyOwnerKind::Fn => { |
| let defining_ty = tcx.type_of(self.mir_def).instantiate_identity(); |
| |
| 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, args) => DefiningTy::Closure(def_id, args), |
| ty::Coroutine(def_id, args, movability) => { |
| DefiningTy::Coroutine(def_id, args, movability) |
| } |
| ty::FnDef(def_id, args) => DefiningTy::FnDef(def_id, args), |
| _ => span_bug!( |
| tcx.def_span(self.mir_def), |
| "expected defining type for `{:?}`: `{:?}`", |
| self.mir_def, |
| defining_ty |
| ), |
| } |
| } |
| |
| BodyOwnerKind::Const { .. } | BodyOwnerKind::Static(..) => { |
| let identity_args = GenericArgs::identity_for_item(tcx, typeck_root_def_id); |
| if self.mir_def.to_def_id() == typeck_root_def_id { |
| let args = |
| self.infcx.replace_free_regions_with_nll_infer_vars(FR, identity_args); |
| DefiningTy::Const(self.mir_def.to_def_id(), args) |
| } else { |
| // FIXME this line creates a dependency between borrowck and typeck. |
| // |
| // This is required for `AscribeUserType` canonical query, which will call |
| // `type_of(inline_const_def_id)`. That `type_of` would inject erased lifetimes |
| // into borrowck, which is ICE #78174. |
| // |
| // As a workaround, inline consts have an additional generic param (`ty` |
| // below), so that `type_of(inline_const_def_id).args(args)` uses the |
| // proper type with NLL infer vars. |
| let ty = tcx |
| .typeck(self.mir_def) |
| .node_type(tcx.local_def_id_to_hir_id(self.mir_def)); |
| let args = InlineConstArgs::new( |
| tcx, |
| InlineConstArgsParts { parent_args: identity_args, ty }, |
| ) |
| .args; |
| let args = self.infcx.replace_free_regions_with_nll_infer_vars(FR, args); |
| DefiningTy::InlineConst(self.mir_def.to_def_id(), args) |
| } |
| } |
| } |
| } |
| |
| /// 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.to_def_id()); |
| let identity_args = GenericArgs::identity_for_item(tcx, typeck_root_def_id); |
| let fr_args = match defining_ty { |
| DefiningTy::Closure(_, args) |
| | DefiningTy::Coroutine(_, args, _) |
| | DefiningTy::InlineConst(_, args) => { |
| // In the case of closures, we rely on the fact that |
| // the first N elements in the ClosureArgs are |
| // inherited from the `typeck_root_def_id`. |
| // Therefore, when we zip together (below) with |
| // `identity_args`, we will get only those regions |
| // that correspond to early-bound regions declared on |
| // the `typeck_root_def_id`. |
| assert!(args.len() >= identity_args.len()); |
| assert_eq!(args.regions().count(), identity_args.regions().count()); |
| args |
| } |
| |
| DefiningTy::FnDef(_, args) | DefiningTy::Const(_, args) => args, |
| }; |
| |
| let global_mapping = iter::once((tcx.lifetimes.re_static, fr_static)); |
| let arg_mapping = iter::zip(identity_args.regions(), fr_args.regions().map(|r| r.as_var())); |
| |
| UniversalRegionIndices { indices: global_mapping.chain(arg_mapping).collect(), fr_static } |
| } |
| |
| fn compute_inputs_and_output( |
| &self, |
| indices: &UniversalRegionIndices<'tcx>, |
| defining_ty: DefiningTy<'tcx>, |
| ) -> ty::Binder<'tcx, &'tcx ty::List<Ty<'tcx>>> { |
| let tcx = self.infcx.tcx; |
| match defining_ty { |
| DefiningTy::Closure(def_id, args) => { |
| assert_eq!(self.mir_def.to_def_id(), def_id); |
| let closure_sig = args.as_closure().sig(); |
| let inputs_and_output = closure_sig.inputs_and_output(); |
| let bound_vars = tcx.mk_bound_variable_kinds_from_iter( |
| 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::Region::new_late_bound(tcx, ty::INNERMOST, br); |
| let closure_ty = tcx.closure_env_ty(def_id, args, 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_from_iter( |
| iter::once(closure_ty).chain(inputs).chain(iter::once(output)), |
| ), |
| bound_vars, |
| ) |
| } |
| |
| DefiningTy::Coroutine(def_id, args, movability) => { |
| assert_eq!(self.mir_def.to_def_id(), def_id); |
| let resume_ty = args.as_coroutine().resume_ty(); |
| let output = args.as_coroutine().return_ty(); |
| let coroutine_ty = Ty::new_coroutine(tcx, def_id, args, movability); |
| let inputs_and_output = |
| self.infcx.tcx.mk_type_list(&[coroutine_ty, resume_ty, output]); |
| ty::Binder::dummy(inputs_and_output) |
| } |
| |
| DefiningTy::FnDef(def_id, _) => { |
| let sig = tcx.fn_sig(def_id).instantiate_identity(); |
| 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.to_def_id(), def_id); |
| let ty = tcx.type_of(self.mir_def).instantiate_identity(); |
| let ty = indices.fold_to_region_vids(tcx, ty); |
| ty::Binder::dummy(tcx.mk_type_list(&[ty])) |
| } |
| |
| DefiningTy::InlineConst(def_id, args) => { |
| assert_eq!(self.mir_def.to_def_id(), def_id); |
| let ty = args.as_inline_const().ty(); |
| ty::Binder::dummy(tcx.mk_type_list(&[ty])) |
| } |
| } |
| } |
| } |
| |
| trait InferCtxtExt<'tcx> { |
| fn replace_free_regions_with_nll_infer_vars<T>( |
| &self, |
| origin: NllRegionVariableOrigin, |
| value: T, |
| ) -> T |
| where |
| T: TypeFoldable<TyCtxt<'tcx>>; |
| |
| fn replace_bound_regions_with_nll_infer_vars<T>( |
| &self, |
| origin: NllRegionVariableOrigin, |
| all_outlive_scope: LocalDefId, |
| value: ty::Binder<'tcx, T>, |
| indices: &mut UniversalRegionIndices<'tcx>, |
| ) -> T |
| where |
| T: TypeFoldable<TyCtxt<'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<'cx, 'tcx> InferCtxtExt<'tcx> for BorrowckInferCtxt<'cx, 'tcx> { |
| #[instrument(skip(self), level = "debug")] |
| fn replace_free_regions_with_nll_infer_vars<T>( |
| &self, |
| origin: NllRegionVariableOrigin, |
| value: T, |
| ) -> T |
| where |
| T: TypeFoldable<TyCtxt<'tcx>>, |
| { |
| self.infcx.tcx.fold_regions(value, |region, _depth| { |
| let name = region.get_name_or_anon(); |
| debug!(?region, ?name); |
| |
| self.next_nll_region_var(origin, || RegionCtxt::Free(name)) |
| }) |
| } |
| |
| #[instrument(level = "debug", skip(self, indices))] |
| fn replace_bound_regions_with_nll_infer_vars<T>( |
| &self, |
| origin: NllRegionVariableOrigin, |
| all_outlive_scope: LocalDefId, |
| value: ty::Binder<'tcx, T>, |
| indices: &mut UniversalRegionIndices<'tcx>, |
| ) -> T |
| where |
| T: TypeFoldable<TyCtxt<'tcx>>, |
| { |
| let (value, _map) = self.tcx.replace_late_bound_regions(value, |br| { |
| debug!(?br); |
| let liberated_region = |
| ty::Region::new_free(self.tcx, all_outlive_scope.to_def_id(), br.kind); |
| let region_vid = { |
| let name = match br.kind.get_name() { |
| Some(name) => name, |
| _ => sym::anon, |
| }; |
| |
| self.next_nll_region_var(origin, || RegionCtxt::Bound(name)) |
| }; |
| |
| indices.insert_late_bound_region(liberated_region, region_vid.as_var()); |
| 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 = { |
| let name = r.get_name_or_anon(); |
| self.next_nll_region_var(FR, || RegionCtxt::LateBound(name)) |
| }; |
| |
| debug!(?region_vid); |
| indices.insert_late_bound_region(r, region_vid.as_var()); |
| } |
| }); |
| } |
| |
| #[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 = { |
| let name = r.get_name_or_anon(); |
| self.next_nll_region_var(FR, || RegionCtxt::LateBound(name)) |
| }; |
| |
| indices.insert_late_bound_region(r, region_vid.as_var()); |
| } |
| }); |
| } |
| } |
| |
| 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 |
| /// be 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.as_var() |
| } else if r.is_error() { |
| // We use the `'static` `RegionVid` because `ReError` doesn't actually exist in the |
| // `UniversalRegionIndices`. This is fine because 1) it is a fallback only used if |
| // errors are being emitted and 2) it leaves the happy path unaffected. |
| self.fr_static |
| } 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<T>(&self, tcx: TyCtxt<'tcx>, value: T) -> T |
| where |
| T: TypeFoldable<TyCtxt<'tcx>>, |
| { |
| tcx.fold_regions(value, |region, _| ty::Region::new_var(tcx, 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 = ty::Region::new_free(tcx, mir_def_id.to_def_id(), bound_region); |
| f(liberated_region); |
| } |
| } |
