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, 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::error::ExpectedFound;
13 use rustc_middle::ty::{self, Ty, TyCtxt};
14 use rustc_span::{MultiSpan, Span};
16 impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
17 /// Print the error message for lifetime errors when the `impl` doesn't conform to the `trait`.
18 pub(super) fn try_report_impl_not_conforming_to_trait(&self) -> Option<ErrorReported> {
19 if let Some(ref error) = self.error {
20 debug!("try_report_impl_not_conforming_to_trait {:?}", error);
21 if let RegionResolutionError::SubSupConflict(
30 if let (&Subtype(ref sup_trace), &Subtype(ref sub_trace)) =
31 (&sup_origin, &sub_origin)
34 ValuePairs::Types(sub_expected_found),
35 ValuePairs::Types(sup_expected_found),
36 CompareImplMethodObligation { trait_item_def_id, .. },
37 ) = (&sub_trace.values, &sup_trace.values, &sub_trace.cause.code)
39 if sup_expected_found == sub_expected_found {
42 sub_expected_found.expected,
43 sub_expected_found.found,
46 return Some(ErrorReported);
55 fn emit_err(&self, sp: Span, expected: Ty<'tcx>, found: Ty<'tcx>, trait_def_id: DefId) {
56 let trait_sp = self.tcx().def_span(trait_def_id);
60 .struct_span_err(sp, "`impl` item signature doesn't match `trait` item signature");
61 err.span_label(sp, &format!("found `{:?}`", found));
62 err.span_label(trait_sp, &format!("expected `{:?}`", expected));
64 // Get the span of all the used type parameters in the method.
65 let assoc_item = self.tcx().associated_item(trait_def_id);
66 let mut visitor = TypeParamSpanVisitor { tcx: self.tcx(), types: vec![] };
67 match assoc_item.kind {
68 ty::AssocKind::Fn => {
69 let hir = self.tcx().hir();
71 assoc_item.def_id.as_local().map(|id| hir.local_def_id_to_hir_id(id))
73 if let Some(decl) = hir.fn_decl_by_hir_id(hir_id) {
74 visitor.visit_fn_decl(decl);
80 let mut type_param_span: MultiSpan = visitor.types.to_vec().into();
81 for &span in &visitor.types {
82 type_param_span.push_span_label(
84 "consider borrowing this type parameter in the trait".to_string(),
88 if let Some((expected, found)) =
89 self.infcx.expected_found_str_ty(&ExpectedFound { expected, found })
91 // Highlighted the differences when showing the "expected/found" note.
92 err.note_expected_found(&"", expected, &"", found);
94 // This fallback shouldn't be necessary, but let's keep it in just in case.
95 err.note(&format!("expected `{:?}`\n found `{:?}`", expected, found));
99 "the lifetime requirements from the `impl` do not correspond to the requirements in \
102 if visitor.types.is_empty() {
104 "verify the lifetime relationships in the `trait` and `impl` between the `self` \
105 argument, the other inputs and its output",
112 struct TypeParamSpanVisitor<'tcx> {
117 impl Visitor<'tcx> for TypeParamSpanVisitor<'tcx> {
118 type Map = rustc_middle::hir::map::Map<'tcx>;
120 fn nested_visit_map(&mut self) -> hir::intravisit::NestedVisitorMap<Self::Map> {
121 hir::intravisit::NestedVisitorMap::OnlyBodies(self.tcx.hir())
124 fn visit_ty(&mut self, arg: &'tcx hir::Ty<'tcx>) {
126 hir::TyKind::Rptr(_, ref mut_ty) => {
127 // We don't want to suggest looking into borrowing `&T` or `&Self`.
128 hir::intravisit::walk_ty(self, mut_ty.ty);
131 hir::TyKind::Path(hir::QPath::Resolved(None, path)) => match &path.segments {
135 .map(|res| match res {
136 Res::SelfTy(_, _) | Res::Def(hir::def::DefKind::TyParam, _) => true,
141 self.types.push(path.span);
147 hir::intravisit::walk_ty(self, arg);