1 //! Error Reporting for Anonymous Region Lifetime Errors
2 //! where one region is named and the other is anonymous.
3 use crate::infer::error_reporting::nice_region_error::find_anon_type::find_anon_type;
4 use crate::infer::error_reporting::nice_region_error::NiceRegionError;
5 use rustc_errors::{struct_span_err, Applicability, DiagnosticBuilder, ErrorGuaranteed};
7 use rustc_span::symbol::kw;
9 impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
10 /// When given a `ConcreteFailure` for a function with parameters containing a named region and
11 /// an anonymous region, emit an descriptive diagnostic error.
12 pub(super) fn try_report_named_anon_conflict(
14 ) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>> {
15 let (span, sub, sup) = self.regions()?;
18 "try_report_named_anon_conflict(sub={:?}, sup={:?}, error={:?})",
22 // Determine whether the sub and sup consist of one named region ('a)
23 // and one anonymous (elided) region. If so, find the parameter arg
24 // where the anonymous region appears (there must always be one; we
25 // only introduced anonymous regions in parameters) as well as a
26 // version new_ty of its type where the anonymous region is replaced
27 // with the named one.
28 let (named, anon, anon_param_info, region_info) = if sub.has_name()
29 && self.tcx().is_suitable_region(sup).is_some()
30 && self.find_param_with_region(sup, sub).is_some()
35 self.find_param_with_region(sup, sub).unwrap(),
36 self.tcx().is_suitable_region(sup).unwrap(),
38 } else if sup.has_name()
39 && self.tcx().is_suitable_region(sub).is_some()
40 && self.find_param_with_region(sub, sup).is_some()
45 self.find_param_with_region(sub, sup).unwrap(),
46 self.tcx().is_suitable_region(sub).unwrap(),
49 return None; // inapplicable
52 // Suggesting to add a `'static` lifetime to a parameter is nearly always incorrect,
53 // and can steer users down the wrong path.
54 if named.is_static() {
58 debug!("try_report_named_anon_conflict: named = {:?}", named);
59 debug!("try_report_named_anon_conflict: anon_param_info = {:?}", anon_param_info);
60 debug!("try_report_named_anon_conflict: region_info = {:?}", region_info);
62 let param = anon_param_info.param;
63 let new_ty = anon_param_info.param_ty;
64 let new_ty_span = anon_param_info.param_ty_span;
65 let br = anon_param_info.bound_region;
66 let is_first = anon_param_info.is_first;
67 let scope_def_id = region_info.def_id;
68 let is_impl_item = region_info.is_impl_item;
71 ty::BrNamed(_, kw::UnderscoreLifetime) | ty::BrAnon(_) => {}
73 /* not an anonymous region */
74 debug!("try_report_named_anon_conflict: not an anonymous region");
80 debug!("try_report_named_anon_conflict: impl item, bail out");
84 if find_anon_type(self.tcx(), anon, &br).is_some()
85 && self.is_self_anon(is_first, scope_def_id)
90 let (error_var, span_label_var) = match param.pat.simple_ident() {
91 Some(simple_ident) => (
92 format!("the type of `{}`", simple_ident),
93 format!("the type of `{}`", simple_ident),
95 None => ("parameter type".to_owned(), "type".to_owned()),
98 let mut diag = struct_span_err!(
102 "explicit lifetime required in {}",
106 diag.span_label(span, format!("lifetime `{}` required", named));
107 diag.span_suggestion(
109 &format!("add explicit lifetime `{}` to {}", named, span_label_var),
111 Applicability::Unspecified,