1 //! Error Reporting for when the lifetime for a type doesn't match the `impl` selected for a predicate
4 use crate::infer::error_reporting::nice_region_error::NiceRegionError;
5 use crate::infer::error_reporting::note_and_explain_region;
6 use crate::infer::lexical_region_resolve::RegionResolutionError;
7 use crate::infer::{SubregionOrigin, TypeTrace};
8 use crate::traits::ObligationCauseCode;
9 use rustc_data_structures::fx::FxHashSet;
10 use rustc_errors::{Applicability, ErrorGuaranteed, MultiSpan};
12 use rustc_hir::intravisit::Visitor;
13 use rustc_middle::ty::TypeVisitor;
15 impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
16 pub(super) fn try_report_mismatched_static_lifetime(&self) -> Option<ErrorGuaranteed> {
17 let error = self.error.as_ref()?;
18 debug!("try_report_mismatched_static_lifetime {:?}", error);
20 let RegionResolutionError::ConcreteFailure(origin, sub, sup) = error.clone() else {
26 let SubregionOrigin::Subtype(box TypeTrace { ref cause, .. }) = origin else {
29 // If we added a "points at argument expression" obligation, we remove it here, we care
30 // about the original obligation only.
31 let code = match cause.code() {
32 ObligationCauseCode::FunctionArgumentObligation { parent_code, .. } => &*parent_code,
35 let ObligationCauseCode::MatchImpl(parent, impl_def_id) = code else {
38 let (ObligationCauseCode::BindingObligation(_, binding_span) | ObligationCauseCode::ExprBindingObligation(_, binding_span, ..))
39 = *parent.code() else {
42 let mut err = self.tcx().sess.struct_span_err(cause.span, "incompatible lifetime on type");
43 // FIXME: we should point at the lifetime
44 let mut multi_span: MultiSpan = vec![binding_span].into();
45 multi_span.push_span_label(binding_span, "introduces a `'static` lifetime requirement");
46 err.span_note(multi_span, "because this has an unmet lifetime requirement");
47 note_and_explain_region(self.tcx(), &mut err, "", sup, "...", Some(binding_span));
48 if let Some(impl_node) = self.tcx().hir().get_if_local(*impl_def_id) {
49 // If an impl is local, then maybe this isn't what they want. Try to
50 // be as helpful as possible with implicit lifetimes.
52 // First, let's get the hir self type of the impl
53 let hir::Node::Item(hir::Item {
54 kind: hir::ItemKind::Impl(hir::Impl { self_ty: impl_self_ty, .. }),
57 bug!("Node not an impl.");
60 // Next, let's figure out the set of trait objects with implicit static bounds
61 let ty = self.tcx().type_of(*impl_def_id);
62 let mut v = super::static_impl_trait::TraitObjectVisitor(FxHashSet::default());
64 let mut traits = vec![];
65 for matching_def_id in v.0 {
67 super::static_impl_trait::HirTraitObjectVisitor(&mut traits, matching_def_id);
68 hir_v.visit_ty(&impl_self_ty);
71 if traits.is_empty() {
72 // If there are no trait object traits to point at, either because
73 // there aren't trait objects or because none are implicit, then just
74 // write a single note on the impl itself.
76 let impl_span = self.tcx().def_span(*impl_def_id);
77 err.span_note(impl_span, "...does not necessarily outlive the static lifetime introduced by the compatible `impl`");
79 // Otherwise, point at all implicit static lifetimes
81 err.note("...does not necessarily outlive the static lifetime introduced by the compatible `impl`");
83 err.span_note(*span, "this has an implicit `'static` lifetime requirement");
84 // It would be nice to put this immediately under the above note, but they get
86 err.span_suggestion_verbose(
88 "consider relaxing the implicit `'static` requirement",
90 Applicability::MaybeIncorrect,
95 // Otherwise just point out the impl.
97 let impl_span = self.tcx().def_span(*impl_def_id);
98 err.span_note(impl_span, "...does not necessarily outlive the static lifetime introduced by the compatible `impl`");
100 let reported = err.emit();