1 // Copyright 2012-2013 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
11 //! Error Reporting for Anonymous Region Lifetime Errors
12 //! where both the regions are anonymous.
15 use ty::{self, Region};
16 use infer::region_inference::RegionResolutionError::*;
17 use infer::region_inference::RegionResolutionError;
18 use hir::map as hir_map;
19 use middle::resolve_lifetime as rl;
20 use hir::intravisit::{self, Visitor, NestedVisitorMap};
22 impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
23 // This method prints the error message for lifetime errors when both the concerned regions
25 // Consider a case where we have
26 // fn foo(x: &mut Vec<&u8>, y: &u8)
29 // fn foo(x: &mut Vec<&u8>, y: &u8) {
30 // --- --- these references are declared with different lifetimes...
32 // ^ ...but data from `y` flows into `x` here
33 // It has been extended for the case of structs too.
34 // Consider the example
35 // struct Ref<'a> { x: &'a u32 }
36 // fn foo(mut x: Vec<Ref>, y: Ref) {
37 // --- --- these structs are declared with different lifetimes...
39 // ^ ...but data from `y` flows into `x` here
41 // It will later be extended to trait objects.
42 pub fn try_report_anon_anon_conflict(&self, error: &RegionResolutionError<'tcx>) -> bool {
43 let (span, sub, sup) = match *error {
44 ConcreteFailure(ref origin, sub, sup) => (origin.span(), sub, sup),
45 _ => return false, // inapplicable
48 // Determine whether the sub and sup consist of both anonymous (elided) regions.
49 let anon_reg_sup = or_false!(self.is_suitable_anonymous_region(sup));
51 let anon_reg_sub = or_false!(self.is_suitable_anonymous_region(sub));
52 let scope_def_id_sup = anon_reg_sup.def_id;
53 let bregion_sup = anon_reg_sup.boundregion;
54 let scope_def_id_sub = anon_reg_sub.def_id;
55 let bregion_sub = anon_reg_sub.boundregion;
57 let ty_sup = or_false!(self.find_anon_type(sup, &bregion_sup));
59 let ty_sub = or_false!(self.find_anon_type(sub, &bregion_sub));
61 let (main_label, label1, label2) = if let (Some(sup_arg), Some(sub_arg)) =
62 (self.find_arg_with_anonymous_region(sup, sup),
63 self.find_arg_with_anonymous_region(sub, sub)) {
65 let (anon_arg_sup, is_first_sup, anon_arg_sub, is_first_sub) =
66 (sup_arg.arg, sup_arg.is_first, sub_arg.arg, sub_arg.is_first);
67 if self.is_self_anon(is_first_sup, scope_def_id_sup) ||
68 self.is_self_anon(is_first_sub, scope_def_id_sub) {
72 if self.is_return_type_anon(scope_def_id_sup, bregion_sup) ||
73 self.is_return_type_anon(scope_def_id_sub, bregion_sub) {
77 if anon_arg_sup == anon_arg_sub {
78 (format!("this type was declared with multiple lifetimes..."),
79 format!(" with one lifetime"),
80 format!(" into the other"))
82 let span_label_var1 = if let Some(simple_name) = anon_arg_sup.pat.simple_name() {
83 format!(" from `{}`", simple_name)
88 let span_label_var2 = if let Some(simple_name) = anon_arg_sub.pat.simple_name() {
89 format!(" into `{}`", simple_name)
95 format!("these two types are declared with different lifetimes...",);
97 (span_label, span_label_var1, span_label_var2)
103 struct_span_err!(self.tcx.sess, span, E0623, "lifetime mismatch")
104 .span_label(ty_sup.span, main_label)
105 .span_label(ty_sub.span, format!(""))
106 .span_label(span, format!("...but data{} flows{} here", label1, label2))
111 /// This function calls the `visit_ty` method for the parameters
112 /// corresponding to the anonymous regions. The `nested_visitor.found_type`
113 /// contains the anonymous type.
116 /// region - the anonymous region corresponding to the anon_anon conflict
117 /// br - the bound region corresponding to the above region which is of type `BrAnon(_)`
121 /// fn foo(x: &mut Vec<&u8>, y: &u8)
124 /// The function returns the nested type corresponding to the anonymous region
125 /// for e.g. `&u8` and Vec<`&u8`.
126 pub fn find_anon_type(&self, region: Region<'tcx>, br: &ty::BoundRegion) -> Option<&hir::Ty> {
127 if let Some(anon_reg) = self.is_suitable_anonymous_region(region) {
128 let def_id = anon_reg.def_id;
129 if let Some(node_id) = self.tcx.hir.as_local_node_id(def_id) {
130 let ret_ty = self.tcx.type_of(def_id);
131 if let ty::TyFnDef(_, _) = ret_ty.sty {
133 match self.tcx.hir.get(node_id) {
134 hir_map::NodeItem(&hir::Item {
135 node: hir::ItemFn(ref fndecl, ..), ..
136 }) => &fndecl.inputs,
137 hir_map::NodeTraitItem(&hir::TraitItem {
138 node: hir::TraitItemKind::Method(ref fndecl, ..),
140 }) => &fndecl.decl.inputs,
141 hir_map::NodeImplItem(&hir::ImplItem {
142 node: hir::ImplItemKind::Method(ref fndecl, ..),
144 }) => &fndecl.decl.inputs,
152 self.find_component_for_bound_region(&**arg, br)
161 // This method creates a FindNestedTypeVisitor which returns the type corresponding
162 // to the anonymous region.
163 fn find_component_for_bound_region(&self,
165 br: &ty::BoundRegion)
166 -> Option<(&'gcx hir::Ty)> {
167 let mut nested_visitor = FindNestedTypeVisitor {
169 hir_map: &self.tcx.hir,
173 nested_visitor.visit_ty(arg);
174 nested_visitor.found_type
178 // The FindNestedTypeVisitor captures the corresponding `hir::Ty` of the
179 // anonymous region. The example above would lead to a conflict between
180 // the two anonymous lifetimes for &u8 in x and y respectively. This visitor
181 // would be invoked twice, once for each lifetime, and would
182 // walk the types like &mut Vec<&u8> and &u8 looking for the HIR
183 // where that lifetime appears. This allows us to highlight the
184 // specific part of the type in the error message.
185 struct FindNestedTypeVisitor<'a, 'gcx: 'a + 'tcx, 'tcx: 'a> {
186 infcx: &'a InferCtxt<'a, 'gcx, 'tcx>,
187 hir_map: &'a hir::map::Map<'gcx>,
188 // The bound_region corresponding to the Refree(freeregion)
189 // associated with the anonymous region we are looking for.
190 bound_region: ty::BoundRegion,
191 // The type where the anonymous lifetime appears
192 // for e.g. Vec<`&u8`> and <`&u8`>
193 found_type: Option<&'gcx hir::Ty>,
196 impl<'a, 'gcx, 'tcx> Visitor<'gcx> for FindNestedTypeVisitor<'a, 'gcx, 'tcx> {
197 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'gcx> {
198 NestedVisitorMap::OnlyBodies(&self.hir_map)
201 fn visit_ty(&mut self, arg: &'gcx hir::Ty) {
202 // Find the index of the anonymous region that was part of the
203 // error. We will then search the function parameters for a bound
204 // region at the right depth with the same index.
205 let br_index = match self.bound_region {
206 ty::BrAnon(index) => index,
211 hir::TyRptr(ref lifetime, _) => {
212 match self.infcx.tcx.named_region_map.defs.get(&lifetime.id) {
213 // the lifetime of the TyRptr
214 Some(&rl::Region::LateBoundAnon(debruijn_index, anon_index)) => {
215 if debruijn_index.depth == 1 && anon_index == br_index {
216 self.found_type = Some(arg);
217 return; // we can stop visiting now
220 Some(&rl::Region::Static) |
221 Some(&rl::Region::EarlyBound(_, _)) |
222 Some(&rl::Region::LateBound(_, _)) |
223 Some(&rl::Region::Free(_, _)) |
225 debug!("no arg found");
229 // Checks if it is of type `hir::TyPath` which corresponds to a struct.
231 let subvisitor = &mut TyPathVisitor {
234 bound_region: self.bound_region,
235 hir_map: self.hir_map,
237 intravisit::walk_ty(subvisitor, arg); // call walk_ty; as visit_ty is empty,
238 // this will visit only outermost type
239 if subvisitor.found_it {
240 self.found_type = Some(arg);
245 // walk the embedded contents: e.g., if we are visiting `Vec<&Foo>`,
246 // go on to visit `&Foo`
247 intravisit::walk_ty(self, arg);
251 // The visitor captures the corresponding `hir::Ty` of the anonymous region
252 // in the case of structs ie. `hir::TyPath`.
253 // This visitor would be invoked for each lifetime corresponding to a struct,
254 // and would walk the types like Vec<Ref> in the above example and Ref looking for the HIR
255 // where that lifetime appears. This allows us to highlight the
256 // specific part of the type in the error message.
257 struct TyPathVisitor<'a, 'gcx: 'a + 'tcx, 'tcx: 'a> {
258 infcx: &'a InferCtxt<'a, 'gcx, 'tcx>,
259 hir_map: &'a hir::map::Map<'gcx>,
261 bound_region: ty::BoundRegion,
264 impl<'a, 'gcx, 'tcx> Visitor<'gcx> for TyPathVisitor<'a, 'gcx, 'tcx> {
265 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'gcx> {
266 NestedVisitorMap::OnlyBodies(&self.hir_map)
269 fn visit_lifetime(&mut self, lifetime: &hir::Lifetime) {
270 let br_index = match self.bound_region {
271 ty::BrAnon(index) => index,
275 match self.infcx.tcx.named_region_map.defs.get(&lifetime.id) {
276 // the lifetime of the TyPath!
277 Some(&rl::Region::LateBoundAnon(debruijn_index, anon_index)) => {
278 if debruijn_index.depth == 1 && anon_index == br_index {
279 self.found_it = true;
282 Some(&rl::Region::Static) |
283 Some(&rl::Region::EarlyBound(_, _)) |
284 Some(&rl::Region::LateBound(_, _)) |
285 Some(&rl::Region::Free(_, _)) |
287 debug!("no arg found");
292 fn visit_ty(&mut self, arg: &'gcx hir::Ty) {
293 // ignore nested types
295 // If you have a type like `Foo<'a, &Ty>` we
296 // are only interested in the immediate lifetimes ('a).
298 // Making `visit_ty` empty will ignore the `&Ty` embedded
299 // inside, it will get reached by the outer visitor.
300 debug!("`Ty` corresponding to a struct is {:?}", arg);