1 //! Error Reporting for `impl` items that do not match the obligations from their `trait`.
3 use crate::infer::error_reporting::nice_region_error::NiceRegionError;
4 use crate::infer::lexical_region_resolve::RegionResolutionError;
5 use crate::infer::Subtype;
6 use crate::traits::ObligationCauseCode::CompareImplItemObligation;
7 use rustc_errors::{ErrorGuaranteed, MultiSpan};
9 use rustc_hir::def::Res;
10 use rustc_hir::def_id::DefId;
11 use rustc_hir::intravisit::Visitor;
12 use rustc_middle::hir::nested_filter;
13 use rustc_middle::ty::print::RegionHighlightMode;
14 use rustc_middle::ty::{self, Ty, TyCtxt, TypeSuperVisitable, TypeVisitor};
17 use std::ops::ControlFlow;
19 impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
20 /// Print the error message for lifetime errors when the `impl` doesn't conform to the `trait`.
21 pub(super) fn try_report_impl_not_conforming_to_trait(&self) -> Option<ErrorGuaranteed> {
22 let error = self.error.as_ref()?;
23 debug!("try_report_impl_not_conforming_to_trait {:?}", error);
24 if let RegionResolutionError::SubSupConflict(
33 && let (Subtype(sup_trace), Subtype(sub_trace)) = (&sup_origin, &sub_origin)
34 && let sub_expected_found @ Some((sub_expected, sub_found)) = sub_trace.values.ty()
35 && let sup_expected_found @ Some(_) = sup_trace.values.ty()
36 && let CompareImplItemObligation { trait_item_def_id, .. } = sub_trace.cause.code()
37 && sup_expected_found == sub_expected_found
40 self.emit_err(var_origin.span(), sub_expected, sub_found, *trait_item_def_id);
52 ) -> ErrorGuaranteed {
53 let trait_sp = self.tcx().def_span(trait_def_id);
57 .struct_span_err(sp, "`impl` item signature doesn't match `trait` item signature");
59 // Mark all unnamed regions in the type with a number.
60 // This diagnostic is called in response to lifetime errors, so be informative.
61 struct HighlightBuilder<'tcx> {
62 highlight: RegionHighlightMode<'tcx>,
66 impl<'tcx> HighlightBuilder<'tcx> {
67 fn build(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> RegionHighlightMode<'tcx> {
69 HighlightBuilder { highlight: RegionHighlightMode::new(tcx), counter: 1 };
75 impl<'tcx> ty::visit::TypeVisitor<'tcx> for HighlightBuilder<'tcx> {
76 fn visit_region(&mut self, r: ty::Region<'tcx>) -> ControlFlow<Self::BreakTy> {
77 if !r.has_name() && self.counter <= 3 {
78 self.highlight.highlighting_region(r, self.counter);
81 r.super_visit_with(self)
85 let expected_highlight = HighlightBuilder::build(self.tcx(), expected);
88 .extract_inference_diagnostics_data(expected.into(), Some(expected_highlight))
90 let found_highlight = HighlightBuilder::build(self.tcx(), found);
92 self.infcx.extract_inference_diagnostics_data(found.into(), Some(found_highlight)).name;
94 err.span_label(sp, &format!("found `{}`", found));
95 err.span_label(trait_sp, &format!("expected `{}`", expected));
97 // Get the span of all the used type parameters in the method.
98 let assoc_item = self.tcx().associated_item(trait_def_id);
99 let mut visitor = TypeParamSpanVisitor { tcx: self.tcx(), types: vec![] };
100 match assoc_item.kind {
101 ty::AssocKind::Fn => {
102 let hir = self.tcx().hir();
103 if let Some(hir_id) =
104 assoc_item.def_id.as_local().map(|id| hir.local_def_id_to_hir_id(id))
106 if let Some(decl) = hir.fn_decl_by_hir_id(hir_id) {
107 visitor.visit_fn_decl(decl);
113 let mut type_param_span: MultiSpan = visitor.types.to_vec().into();
114 for &span in &visitor.types {
116 .push_span_label(span, "consider borrowing this type parameter in the trait");
119 err.note(&format!("expected `{}`\n found `{}`", expected, found));
123 "the lifetime requirements from the `impl` do not correspond to the requirements in \
126 if visitor.types.is_empty() {
128 "verify the lifetime relationships in the `trait` and `impl` between the `self` \
129 argument, the other inputs and its output",
136 struct TypeParamSpanVisitor<'tcx> {
141 impl<'tcx> Visitor<'tcx> for TypeParamSpanVisitor<'tcx> {
142 type NestedFilter = nested_filter::OnlyBodies;
144 fn nested_visit_map(&mut self) -> Self::Map {
148 fn visit_ty(&mut self, arg: &'tcx hir::Ty<'tcx>) {
150 hir::TyKind::Rptr(_, ref mut_ty) => {
151 // We don't want to suggest looking into borrowing `&T` or `&Self`.
152 hir::intravisit::walk_ty(self, mut_ty.ty);
155 hir::TyKind::Path(hir::QPath::Resolved(None, path)) => match &path.segments {
162 Res::SelfTy { trait_: _, alias_to: _ }
163 | Res::Def(hir::def::DefKind::TyParam, _)
168 self.types.push(path.span);
174 hir::intravisit::walk_ty(self, arg);