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::{SubregionOrigin, Subtype, ValuePairs};
6 use crate::traits::ObligationCauseCode::CompareImplMethodObligation;
7 use rustc_errors::ErrorReported;
9 use rustc_hir::def::Res;
10 use rustc_hir::def_id::DefId;
11 use rustc_hir::intravisit::Visitor;
12 use rustc_middle::ty::print::RegionHighlightMode;
13 use rustc_middle::ty::{self, Ty, TyCtxt, TypeFoldable, TypeVisitor};
15 use rustc_span::{MultiSpan, Span, Symbol};
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<ErrorReported> {
22 let error = self.error.as_ref()?;
23 debug!("try_report_impl_not_conforming_to_trait {:?}", error);
24 if let RegionResolutionError::SubSupConflict(
33 if let (&Subtype(ref sup_trace), &Subtype(ref sub_trace)) = (&sup_origin, &sub_origin) {
35 ValuePairs::Types(sub_expected_found),
36 ValuePairs::Types(sup_expected_found),
37 CompareImplMethodObligation { trait_item_def_id, .. },
38 ) = (&sub_trace.values, &sup_trace.values, &sub_trace.cause.code)
40 if sup_expected_found == sub_expected_found {
43 sub_expected_found.expected,
44 sub_expected_found.found,
47 return Some(ErrorReported);
52 if let RegionResolutionError::ConcreteFailure(origin, _, _)
53 | RegionResolutionError::GenericBoundFailure(origin, _, _) = error.clone()
55 if let SubregionOrigin::CompareImplTypeObligation {
62 self.emit_associated_type_err(span, item_name, impl_item_def_id, trait_item_def_id);
63 return Some(ErrorReported);
69 fn emit_err(&self, sp: Span, expected: Ty<'tcx>, found: Ty<'tcx>, trait_def_id: DefId) {
70 let trait_sp = self.tcx().def_span(trait_def_id);
74 .struct_span_err(sp, "`impl` item signature doesn't match `trait` item signature");
76 // Mark all unnamed regions in the type with a number.
77 // This diagnostic is called in response to lifetime errors, so be informative.
78 struct HighlightBuilder<'tcx> {
79 highlight: RegionHighlightMode,
84 impl HighlightBuilder<'tcx> {
85 fn build(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> RegionHighlightMode {
87 HighlightBuilder { highlight: RegionHighlightMode::default(), counter: 1, tcx };
93 impl<'tcx> ty::fold::TypeVisitor<'tcx> for HighlightBuilder<'tcx> {
94 fn tcx_for_anon_const_substs(&self) -> Option<TyCtxt<'tcx>> {
98 fn visit_region(&mut self, r: ty::Region<'tcx>) -> ControlFlow<Self::BreakTy> {
99 if !r.has_name() && self.counter <= 3 {
100 self.highlight.highlighting_region(r, self.counter);
103 r.super_visit_with(self)
107 let expected_highlight = HighlightBuilder::build(self.tcx(), expected);
110 .extract_inference_diagnostics_data(expected.into(), Some(expected_highlight))
112 let found_highlight = HighlightBuilder::build(self.tcx(), found);
114 self.infcx.extract_inference_diagnostics_data(found.into(), Some(found_highlight)).name;
116 err.span_label(sp, &format!("found `{}`", found));
117 err.span_label(trait_sp, &format!("expected `{}`", expected));
119 // Get the span of all the used type parameters in the method.
120 let assoc_item = self.tcx().associated_item(trait_def_id);
121 let mut visitor = TypeParamSpanVisitor { tcx: self.tcx(), types: vec![] };
122 match assoc_item.kind {
123 ty::AssocKind::Fn => {
124 let hir = self.tcx().hir();
125 if let Some(hir_id) =
126 assoc_item.def_id.as_local().map(|id| hir.local_def_id_to_hir_id(id))
128 if let Some(decl) = hir.fn_decl_by_hir_id(hir_id) {
129 visitor.visit_fn_decl(decl);
135 let mut type_param_span: MultiSpan = visitor.types.to_vec().into();
136 for &span in &visitor.types {
137 type_param_span.push_span_label(
139 "consider borrowing this type parameter in the trait".to_string(),
143 err.note(&format!("expected `{}`\n found `{}`", expected, found));
147 "the lifetime requirements from the `impl` do not correspond to the requirements in \
150 if visitor.types.is_empty() {
152 "verify the lifetime relationships in the `trait` and `impl` between the `self` \
153 argument, the other inputs and its output",
159 fn emit_associated_type_err(
163 impl_item_def_id: DefId,
164 trait_item_def_id: DefId,
166 let impl_sp = self.tcx().def_span(impl_item_def_id);
167 let trait_sp = self.tcx().def_span(trait_item_def_id);
171 .struct_span_err(span, &format!("`impl` associated type signature for `{}` doesn't match `trait` associated type signature", item_name));
172 err.span_label(impl_sp, "found");
173 err.span_label(trait_sp, "expected");
179 struct TypeParamSpanVisitor<'tcx> {
184 impl Visitor<'tcx> for TypeParamSpanVisitor<'tcx> {
185 type Map = rustc_middle::hir::map::Map<'tcx>;
187 fn nested_visit_map(&mut self) -> hir::intravisit::NestedVisitorMap<Self::Map> {
188 hir::intravisit::NestedVisitorMap::OnlyBodies(self.tcx.hir())
191 fn visit_ty(&mut self, arg: &'tcx hir::Ty<'tcx>) {
193 hir::TyKind::Rptr(_, ref mut_ty) => {
194 // We don't want to suggest looking into borrowing `&T` or `&Self`.
195 hir::intravisit::walk_ty(self, mut_ty.ty);
198 hir::TyKind::Path(hir::QPath::Resolved(None, path)) => match &path.segments {
205 Res::SelfTy(_, _) | Res::Def(hir::def::DefKind::TyParam, _)
210 self.types.push(path.span);
216 hir::intravisit::walk_ty(self, arg);