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<'tcx>, &hir::FnDecl<'tcx>)> {
30 if let Some(anon_reg) = self.tcx().is_suitable_region(region) {
31 let hir_id = self.tcx().hir().local_def_id_to_hir_id(anon_reg.def_id);
32 let fndecl = match self.tcx().hir().get(hir_id) {
33 Node::Item(&hir::Item { kind: hir::ItemKind::Fn(ref m, ..), .. })
34 | Node::TraitItem(&hir::TraitItem {
35 kind: hir::TraitItemKind::Fn(ref m, ..),
38 | Node::ImplItem(&hir::ImplItem {
39 kind: hir::ImplItemKind::Fn(ref m, ..), ..
47 .find_map(|arg| self.find_component_for_bound_region(arg, br))
48 .map(|ty| (ty, &**fndecl))
54 // This method creates a FindNestedTypeVisitor which returns the type corresponding
55 // to the anonymous region.
56 fn find_component_for_bound_region(
58 arg: &'tcx hir::Ty<'tcx>,
60 ) -> Option<&'tcx hir::Ty<'tcx>> {
61 let mut nested_visitor = FindNestedTypeVisitor {
65 current_index: ty::INNERMOST,
67 nested_visitor.visit_ty(arg);
68 nested_visitor.found_type
72 // The FindNestedTypeVisitor captures the corresponding `hir::Ty` of the
73 // anonymous region. The example above would lead to a conflict between
74 // the two anonymous lifetimes for &u8 in x and y respectively. This visitor
75 // would be invoked twice, once for each lifetime, and would
76 // walk the types like &mut Vec<&u8> and &u8 looking for the HIR
77 // where that lifetime appears. This allows us to highlight the
78 // specific part of the type in the error message.
79 struct FindNestedTypeVisitor<'tcx> {
81 // The bound_region corresponding to the Refree(freeregion)
82 // associated with the anonymous region we are looking for.
83 bound_region: ty::BoundRegion,
84 // The type where the anonymous lifetime appears
85 // for e.g., Vec<`&u8`> and <`&u8`>
86 found_type: Option<&'tcx hir::Ty<'tcx>>,
87 current_index: ty::DebruijnIndex,
90 impl Visitor<'tcx> for FindNestedTypeVisitor<'tcx> {
93 fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
94 NestedVisitorMap::OnlyBodies(self.tcx.hir())
97 fn visit_ty(&mut self, arg: &'tcx hir::Ty<'tcx>) {
99 hir::TyKind::BareFn(_) => {
100 self.current_index.shift_in(1);
101 intravisit::walk_ty(self, arg);
102 self.current_index.shift_out(1);
106 hir::TyKind::TraitObject(bounds, _) => {
107 for bound in bounds {
108 self.current_index.shift_in(1);
109 self.visit_poly_trait_ref(bound, hir::TraitBoundModifier::None);
110 self.current_index.shift_out(1);
114 hir::TyKind::Rptr(ref lifetime, _) => {
115 // the lifetime of the TyRptr
116 let hir_id = lifetime.hir_id;
117 match (self.tcx.named_region(hir_id), self.bound_region) {
118 // Find the index of the anonymous region that was part of the
119 // error. We will then search the function parameters for a bound
120 // region at the right depth with the same index
122 Some(rl::Region::LateBoundAnon(debruijn_index, anon_index)),
123 ty::BrAnon(br_index),
126 "LateBoundAnon depth = {:?} anon_index = {:?} br_index={:?}",
127 debruijn_index, anon_index, br_index
129 if debruijn_index == self.current_index && anon_index == br_index {
130 self.found_type = Some(arg);
131 return; // we can stop visiting now
135 // Find the index of the named region that was part of the
136 // error. We will then search the function parameters for a bound
137 // region at the right depth with the same index
138 (Some(rl::Region::EarlyBound(_, id, _)), ty::BrNamed(def_id, _)) => {
139 debug!("EarlyBound id={:?} def_id={:?}", id, def_id);
141 self.found_type = Some(arg);
142 return; // we can stop visiting now
146 // Find the index of the named region that was part of the
147 // error. We will then search the function parameters for a bound
148 // region at the right depth with the same index
150 Some(rl::Region::LateBound(debruijn_index, id, _)),
151 ty::BrNamed(def_id, _),
154 "FindNestedTypeVisitor::visit_ty: LateBound depth = {:?}",
157 debug!("LateBound id={:?} def_id={:?}", id, def_id);
158 if debruijn_index == self.current_index && id == def_id {
159 self.found_type = Some(arg);
160 return; // we can stop visiting now
167 | rl::Region::Free(_, _)
168 | rl::Region::EarlyBound(_, _, _)
169 | rl::Region::LateBound(_, _, _)
170 | rl::Region::LateBoundAnon(_, _),
175 debug!("no arg found");
179 // Checks if it is of type `hir::TyKind::Path` which corresponds to a struct.
180 hir::TyKind::Path(_) => {
181 let subvisitor = &mut TyPathVisitor {
184 bound_region: self.bound_region,
185 current_index: self.current_index,
187 intravisit::walk_ty(subvisitor, arg); // call walk_ty; as visit_ty is empty,
188 // this will visit only outermost type
189 if subvisitor.found_it {
190 self.found_type = Some(arg);
195 // walk the embedded contents: e.g., if we are visiting `Vec<&Foo>`,
196 // go on to visit `&Foo`
197 intravisit::walk_ty(self, arg);
201 // The visitor captures the corresponding `hir::Ty` of the anonymous region
202 // in the case of structs ie. `hir::TyKind::Path`.
203 // This visitor would be invoked for each lifetime corresponding to a struct,
204 // and would walk the types like Vec<Ref> in the above example and Ref looking for the HIR
205 // where that lifetime appears. This allows us to highlight the
206 // specific part of the type in the error message.
207 struct TyPathVisitor<'tcx> {
210 bound_region: ty::BoundRegion,
211 current_index: ty::DebruijnIndex,
214 impl Visitor<'tcx> for TyPathVisitor<'tcx> {
215 type Map = Map<'tcx>;
217 fn nested_visit_map(&mut self) -> NestedVisitorMap<Map<'tcx>> {
218 NestedVisitorMap::OnlyBodies(self.tcx.hir())
221 fn visit_lifetime(&mut self, lifetime: &hir::Lifetime) {
222 match (self.tcx.named_region(lifetime.hir_id), self.bound_region) {
223 // the lifetime of the TyPath!
224 (Some(rl::Region::LateBoundAnon(debruijn_index, anon_index)), ty::BrAnon(br_index)) => {
225 if debruijn_index == self.current_index && anon_index == br_index {
226 self.found_it = true;
231 (Some(rl::Region::EarlyBound(_, id, _)), ty::BrNamed(def_id, _)) => {
232 debug!("EarlyBound id={:?} def_id={:?}", id, def_id);
234 self.found_it = true;
235 return; // we can stop visiting now
239 (Some(rl::Region::LateBound(debruijn_index, id, _)), ty::BrNamed(def_id, _)) => {
240 debug!("FindNestedTypeVisitor::visit_ty: LateBound depth = {:?}", debruijn_index,);
241 debug!("id={:?}", id);
242 debug!("def_id={:?}", def_id);
243 if debruijn_index == self.current_index && id == def_id {
244 self.found_it = true;
245 return; // we can stop visiting now
252 | rl::Region::EarlyBound(_, _, _)
253 | rl::Region::LateBound(_, _, _)
254 | rl::Region::LateBoundAnon(_, _)
255 | rl::Region::Free(_, _),
260 debug!("no arg found");
265 fn visit_ty(&mut self, arg: &'tcx hir::Ty<'tcx>) {
266 // ignore nested types
268 // If you have a type like `Foo<'a, &Ty>` we
269 // are only interested in the immediate lifetimes ('a).
271 // Making `visit_ty` empty will ignore the `&Ty` embedded
272 // inside, it will get reached by the outer visitor.
273 debug!("`Ty` corresponding to a struct is {:?}", arg);