1 use crate::infer::error_reporting::nice_region_error::NiceRegionError;
3 use rustc_hir::intravisit::{self, NestedVisitorMap, Visitor};
5 use rustc_middle::hir::map::Map;
6 use rustc_middle::middle::resolve_lifetime as rl;
7 use rustc_middle::ty::{self, Region, TyCtxt};
9 impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
10 /// This function calls the `visit_ty` method for the parameters
11 /// corresponding to the anonymous regions. The `nested_visitor.found_type`
12 /// contains the anonymous type.
15 /// region - the anonymous region corresponding to the anon_anon conflict
16 /// br - the bound region corresponding to the above region which is of type `BrAnon(_)`
20 /// fn foo(x: &mut Vec<&u8>, y: &u8)
23 /// The function returns the nested type corresponding to the anonymous region
24 /// for e.g., `&u8` and Vec<`&u8`.
25 pub(super) fn find_anon_type(
29 ) -> Option<(&hir::Ty<'_>, &hir::FnDecl<'_>)> {
30 if let Some(anon_reg) = self.tcx().is_suitable_region(region) {
31 let def_id = anon_reg.def_id;
32 if let Some(def_id) = def_id.as_local() {
33 let hir_id = self.tcx().hir().as_local_hir_id(def_id);
34 let fndecl = match self.tcx().hir().get(hir_id) {
35 Node::Item(&hir::Item { kind: hir::ItemKind::Fn(ref m, ..), .. })
36 | Node::TraitItem(&hir::TraitItem {
37 kind: hir::TraitItemKind::Fn(ref m, ..),
40 | Node::ImplItem(&hir::ImplItem {
41 kind: hir::ImplItemKind::Fn(ref m, ..),
50 .filter_map(|arg| self.find_component_for_bound_region(arg, br))
52 .map(|ty| (ty, &**fndecl));
58 // This method creates a FindNestedTypeVisitor which returns the type corresponding
59 // to the anonymous region.
60 fn find_component_for_bound_region(
62 arg: &'tcx hir::Ty<'tcx>,
64 ) -> Option<&'tcx hir::Ty<'tcx>> {
65 let mut nested_visitor = FindNestedTypeVisitor {
69 current_index: ty::INNERMOST,
71 nested_visitor.visit_ty(arg);
72 nested_visitor.found_type
76 // The FindNestedTypeVisitor captures the corresponding `hir::Ty` of the
77 // anonymous region. The example above would lead to a conflict between
78 // the two anonymous lifetimes for &u8 in x and y respectively. This visitor
79 // would be invoked twice, once for each lifetime, and would
80 // walk the types like &mut Vec<&u8> and &u8 looking for the HIR
81 // where that lifetime appears. This allows us to highlight the
82 // specific part of the type in the error message.
83 struct FindNestedTypeVisitor<'tcx> {
85 // The bound_region corresponding to the Refree(freeregion)
86 // associated with the anonymous region we are looking for.
87 bound_region: ty::BoundRegion,
88 // The type where the anonymous lifetime appears
89 // for e.g., Vec<`&u8`> and <`&u8`>
90 found_type: Option<&'tcx hir::Ty<'tcx>>,
91 current_index: ty::DebruijnIndex,
94 impl Visitor<'tcx> for FindNestedTypeVisitor<'tcx> {
97 fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
98 NestedVisitorMap::OnlyBodies(self.tcx.hir())
101 fn visit_ty(&mut self, arg: &'tcx hir::Ty<'tcx>) {
103 hir::TyKind::BareFn(_) => {
104 self.current_index.shift_in(1);
105 intravisit::walk_ty(self, arg);
106 self.current_index.shift_out(1);
110 hir::TyKind::TraitObject(bounds, _) => {
111 for bound in bounds {
112 self.current_index.shift_in(1);
113 self.visit_poly_trait_ref(bound, hir::TraitBoundModifier::None);
114 self.current_index.shift_out(1);
118 hir::TyKind::Rptr(ref lifetime, _) => {
119 // the lifetime of the TyRptr
120 let hir_id = lifetime.hir_id;
121 match (self.tcx.named_region(hir_id), self.bound_region) {
122 // Find the index of the anonymous region that was part of the
123 // error. We will then search the function parameters for a bound
124 // region at the right depth with the same index
126 Some(rl::Region::LateBoundAnon(debruijn_index, anon_index)),
127 ty::BrAnon(br_index),
130 "LateBoundAnon depth = {:?} anon_index = {:?} br_index={:?}",
131 debruijn_index, anon_index, br_index
133 if debruijn_index == self.current_index && anon_index == br_index {
134 self.found_type = Some(arg);
135 return; // we can stop visiting now
139 // Find the index of the named region that was part of the
140 // error. We will then search the function parameters for a bound
141 // region at the right depth with the same index
142 (Some(rl::Region::EarlyBound(_, id, _)), ty::BrNamed(def_id, _)) => {
143 debug!("EarlyBound id={:?} def_id={:?}", id, def_id);
145 self.found_type = Some(arg);
146 return; // we can stop visiting now
150 // Find the index of the named region that was part of the
151 // error. We will then search the function parameters for a bound
152 // region at the right depth with the same index
154 Some(rl::Region::LateBound(debruijn_index, id, _)),
155 ty::BrNamed(def_id, _),
158 "FindNestedTypeVisitor::visit_ty: LateBound depth = {:?}",
161 debug!("LateBound id={:?} def_id={:?}", id, def_id);
162 if debruijn_index == self.current_index && id == def_id {
163 self.found_type = Some(arg);
164 return; // we can stop visiting now
171 | rl::Region::Free(_, _)
172 | rl::Region::EarlyBound(_, _, _)
173 | rl::Region::LateBound(_, _, _)
174 | rl::Region::LateBoundAnon(_, _),
179 debug!("no arg found");
183 // Checks if it is of type `hir::TyKind::Path` which corresponds to a struct.
184 hir::TyKind::Path(_) => {
185 let subvisitor = &mut TyPathVisitor {
188 bound_region: self.bound_region,
189 current_index: self.current_index,
191 intravisit::walk_ty(subvisitor, arg); // call walk_ty; as visit_ty is empty,
192 // this will visit only outermost type
193 if subvisitor.found_it {
194 self.found_type = Some(arg);
199 // walk the embedded contents: e.g., if we are visiting `Vec<&Foo>`,
200 // go on to visit `&Foo`
201 intravisit::walk_ty(self, arg);
205 // The visitor captures the corresponding `hir::Ty` of the anonymous region
206 // in the case of structs ie. `hir::TyKind::Path`.
207 // This visitor would be invoked for each lifetime corresponding to a struct,
208 // and would walk the types like Vec<Ref> in the above example and Ref looking for the HIR
209 // where that lifetime appears. This allows us to highlight the
210 // specific part of the type in the error message.
211 struct TyPathVisitor<'tcx> {
214 bound_region: ty::BoundRegion,
215 current_index: ty::DebruijnIndex,
218 impl Visitor<'tcx> for TyPathVisitor<'tcx> {
219 type Map = Map<'tcx>;
221 fn nested_visit_map(&mut self) -> NestedVisitorMap<Map<'tcx>> {
222 NestedVisitorMap::OnlyBodies(self.tcx.hir())
225 fn visit_lifetime(&mut self, lifetime: &hir::Lifetime) {
226 match (self.tcx.named_region(lifetime.hir_id), self.bound_region) {
227 // the lifetime of the TyPath!
228 (Some(rl::Region::LateBoundAnon(debruijn_index, anon_index)), ty::BrAnon(br_index)) => {
229 if debruijn_index == self.current_index && anon_index == br_index {
230 self.found_it = true;
235 (Some(rl::Region::EarlyBound(_, id, _)), ty::BrNamed(def_id, _)) => {
236 debug!("EarlyBound id={:?} def_id={:?}", id, def_id);
238 self.found_it = true;
239 return; // we can stop visiting now
243 (Some(rl::Region::LateBound(debruijn_index, id, _)), ty::BrNamed(def_id, _)) => {
244 debug!("FindNestedTypeVisitor::visit_ty: LateBound depth = {:?}", debruijn_index,);
245 debug!("id={:?}", id);
246 debug!("def_id={:?}", def_id);
247 if debruijn_index == self.current_index && id == def_id {
248 self.found_it = true;
249 return; // we can stop visiting now
256 | rl::Region::EarlyBound(_, _, _)
257 | rl::Region::LateBound(_, _, _)
258 | rl::Region::LateBoundAnon(_, _)
259 | rl::Region::Free(_, _),
264 debug!("no arg found");
269 fn visit_ty(&mut self, arg: &'tcx hir::Ty<'tcx>) {
270 // ignore nested types
272 // If you have a type like `Foo<'a, &Ty>` we
273 // are only interested in the immediate lifetimes ('a).
275 // Making `visit_ty` empty will ignore the `&Ty` embedded
276 // inside, it will get reached by the outer visitor.
277 debug!("`Ty` corresponding to a struct is {:?}", arg);