1 //! Error Reporting for Anonymous Region Lifetime Errors
2 //! where both the regions are anonymous.
4 use crate::infer::error_reporting::nice_region_error::find_anon_type::find_anon_type;
5 use crate::infer::error_reporting::nice_region_error::util::AnonymousParamInfo;
6 use crate::infer::error_reporting::nice_region_error::NiceRegionError;
7 use crate::infer::lexical_region_resolve::RegionResolutionError;
8 use crate::infer::SubregionOrigin;
9 use crate::infer::TyCtxt;
11 use rustc_errors::{struct_span_err, Applicability, Diagnostic, ErrorGuaranteed};
13 use rustc_hir::{GenericParamKind, Ty};
14 use rustc_middle::ty::Region;
16 impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
17 /// Print the error message for lifetime errors when both the concerned regions are anonymous.
19 /// Consider a case where we have
21 /// ```compile_fail,E0623
22 /// fn foo(x: &mut Vec<&u8>, y: &u8) {
30 /// fn foo(x: &mut Vec<&u8>, y: &u8) {
31 /// --- --- these references are declared with different lifetimes...
33 /// ^ ...but data from `y` flows into `x` here
36 /// It has been extended for the case of structs too.
38 /// Consider the example
41 /// struct Ref<'a> { x: &'a u32 }
45 /// fn foo(mut x: Vec<Ref>, y: Ref) {
46 /// --- --- these structs are declared with different lifetimes...
48 /// ^ ...but data from `y` flows into `x` here
52 /// It will later be extended to trait objects.
53 pub(super) fn try_report_anon_anon_conflict(&self) -> Option<ErrorGuaranteed> {
54 let (span, sub, sup) = self.regions()?;
56 if let Some(RegionResolutionError::ConcreteFailure(
57 SubregionOrigin::ReferenceOutlivesReferent(..),
61 // This error doesn't make much sense in this case.
65 // Determine whether the sub and sup consist of both anonymous (elided) regions.
66 let anon_reg_sup = self.tcx().is_suitable_region(sup)?;
68 let anon_reg_sub = self.tcx().is_suitable_region(sub)?;
69 let scope_def_id_sup = anon_reg_sup.def_id;
70 let bregion_sup = anon_reg_sup.boundregion;
71 let scope_def_id_sub = anon_reg_sub.def_id;
72 let bregion_sub = anon_reg_sub.boundregion;
74 let ty_sup = find_anon_type(self.tcx(), sup, &bregion_sup)?;
76 let ty_sub = find_anon_type(self.tcx(), sub, &bregion_sub)?;
79 "try_report_anon_anon_conflict: found_param1={:?} sup={:?} br1={:?}",
80 ty_sub, sup, bregion_sup
83 "try_report_anon_anon_conflict: found_param2={:?} sub={:?} br2={:?}",
84 ty_sup, sub, bregion_sub
87 let (ty_sup, ty_fndecl_sup) = ty_sup;
88 let (ty_sub, ty_fndecl_sub) = ty_sub;
90 let AnonymousParamInfo { param: anon_param_sup, .. } =
91 self.find_param_with_region(sup, sup)?;
92 let AnonymousParamInfo { param: anon_param_sub, .. } =
93 self.find_param_with_region(sub, sub)?;
96 self.is_return_type_anon(scope_def_id_sup, bregion_sup, ty_fndecl_sup);
98 self.is_return_type_anon(scope_def_id_sub, bregion_sub, ty_fndecl_sub);
100 let span_label_var1 = match anon_param_sup.pat.simple_ident() {
101 Some(simple_ident) => format!(" from `{}`", simple_ident),
102 None => String::new(),
105 let span_label_var2 = match anon_param_sub.pat.simple_ident() {
106 Some(simple_ident) => format!(" into `{}`", simple_ident),
107 None => String::new(),
111 "try_report_anon_anon_conflict: sub_is_ret_type={:?} sup_is_ret_type={:?}",
112 sub_is_ret_type, sup_is_ret_type
115 let mut err = struct_span_err!(self.tcx().sess, span, E0623, "lifetime mismatch");
117 match (sup_is_ret_type, sub_is_ret_type) {
118 (ret_capture @ Some(ret_span), _) | (_, ret_capture @ Some(ret_span)) => {
120 if sup_is_ret_type == ret_capture { ty_sub.span } else { ty_sup.span };
124 "this parameter and the return type are declared with different lifetimes...",
126 err.span_label(ret_span, "");
127 err.span_label(span, format!("...but data{} is returned here", span_label_var1));
131 if ty_sup.hir_id == ty_sub.hir_id {
132 err.span_label(ty_sup.span, "this type is declared with multiple lifetimes...");
133 err.span_label(ty_sub.span, "");
134 err.span_label(span, "...but data with one lifetime flows into the other here");
138 "these two types are declared with different lifetimes...",
140 err.span_label(ty_sub.span, "");
143 format!("...but data{} flows{} here", span_label_var1, span_label_var2),
149 if suggest_adding_lifetime_params(self.tcx(), sub, ty_sup, ty_sub, &mut err) {
150 err.note("each elided lifetime in input position becomes a distinct lifetime");
153 let reported = err.emit();
158 pub fn suggest_adding_lifetime_params<'tcx>(
163 err: &mut Diagnostic,
166 hir::Ty { kind: hir::TyKind::Rptr(lifetime_sub, _), .. },
167 hir::Ty { kind: hir::TyKind::Rptr(lifetime_sup, _), .. },
168 ) = (ty_sub, ty_sup) else {
172 if !lifetime_sub.name.is_elided() || !lifetime_sup.name.is_elided() {
176 let Some(anon_reg) = tcx.is_suitable_region(sub) else {
180 let hir_id = tcx.hir().local_def_id_to_hir_id(anon_reg.def_id);
182 let node = tcx.hir().get(hir_id);
183 let is_impl = matches!(&node, hir::Node::ImplItem(_));
184 let generics = match node {
185 hir::Node::Item(&hir::Item { kind: hir::ItemKind::Fn(_, ref generics, ..), .. })
186 | hir::Node::TraitItem(&hir::TraitItem { ref generics, .. })
187 | hir::Node::ImplItem(&hir::ImplItem { ref generics, .. }) => generics,
191 let (suggestion_param_name, introduce_new) = generics
194 .find(|p| matches!(p.kind, GenericParamKind::Lifetime { .. }))
195 .and_then(|p| tcx.sess.source_map().span_to_snippet(p.span).ok())
196 .map(|name| (name, false))
197 .unwrap_or_else(|| ("'a".to_string(), true));
199 let mut suggestions = vec![
200 if let hir::LifetimeName::Underscore = lifetime_sub.name {
201 (lifetime_sub.span, suggestion_param_name.clone())
203 (lifetime_sub.span.shrink_to_hi(), suggestion_param_name.clone() + " ")
205 if let hir::LifetimeName::Underscore = lifetime_sup.name {
206 (lifetime_sup.span, suggestion_param_name.clone())
208 (lifetime_sup.span.shrink_to_hi(), suggestion_param_name.clone() + " ")
213 let new_param_suggestion = match &generics.params {
214 [] => (generics.span, format!("<{}>", suggestion_param_name)),
215 [first, ..] => (first.span.shrink_to_lo(), format!("{}, ", suggestion_param_name)),
218 suggestions.push(new_param_suggestion);
221 let mut sugg = String::from("consider introducing a named lifetime parameter");
223 sugg.push_str(" and update trait if needed");
225 err.multipart_suggestion(sugg.as_str(), suggestions, Applicability::MaybeIncorrect);