| use errors::DiagnosticBuilder; |
| use crate::hir::def::Namespace; |
| use crate::hir::def_id::DefId; |
| use crate::infer::error_reporting::nice_region_error::NiceRegionError; |
| use crate::infer::lexical_region_resolve::RegionResolutionError; |
| use crate::infer::ValuePairs; |
| use crate::infer::{SubregionOrigin, TypeTrace}; |
| use crate::traits::{ObligationCause, ObligationCauseCode}; |
| use crate::ty::{self, TyCtxt}; |
| use crate::ty::error::ExpectedFound; |
| use crate::ty::subst::SubstsRef; |
| use crate::ty::print::{Print, RegionHighlightMode, FmtPrinter}; |
| |
| use std::fmt::{self, Write}; |
| |
| impl NiceRegionError<'me, 'tcx> { |
| /// When given a `ConcreteFailure` for a function with arguments containing a named region and |
| /// an anonymous region, emit a descriptive diagnostic error. |
| pub(super) fn try_report_placeholder_conflict(&self) -> Option<DiagnosticBuilder<'me>> { |
| match &self.error { |
| /////////////////////////////////////////////////////////////////////////// |
| // NB. The ordering of cases in this match is very |
| // sensitive, because we are often matching against |
| // specific cases and then using an `_` to match all |
| // others. |
| |
| /////////////////////////////////////////////////////////////////////////// |
| // Check for errors from comparing trait failures -- first |
| // with two placeholders, then with one. |
| Some(RegionResolutionError::SubSupConflict( |
| vid, |
| _, |
| SubregionOrigin::Subtype(box TypeTrace { |
| cause, |
| values: ValuePairs::TraitRefs(ExpectedFound { expected, found }), |
| }), |
| sub_placeholder @ ty::RePlaceholder(_), |
| _, |
| sup_placeholder @ ty::RePlaceholder(_), |
| )) if expected.def_id == found.def_id => Some(self.try_report_placeholders_trait( |
| Some(self.tcx().mk_region(ty::ReVar(*vid))), |
| cause, |
| Some(sub_placeholder), |
| Some(sup_placeholder), |
| expected.def_id, |
| expected.substs, |
| found.substs, |
| )), |
| |
| Some(RegionResolutionError::SubSupConflict( |
| vid, |
| _, |
| SubregionOrigin::Subtype(box TypeTrace { |
| cause, |
| values: ValuePairs::TraitRefs(ExpectedFound { expected, found }), |
| }), |
| sub_placeholder @ ty::RePlaceholder(_), |
| _, |
| _, |
| )) if expected.def_id == found.def_id => Some(self.try_report_placeholders_trait( |
| Some(self.tcx().mk_region(ty::ReVar(*vid))), |
| cause, |
| Some(sub_placeholder), |
| None, |
| expected.def_id, |
| expected.substs, |
| found.substs, |
| )), |
| |
| Some(RegionResolutionError::SubSupConflict( |
| vid, |
| _, |
| SubregionOrigin::Subtype(box TypeTrace { |
| cause, |
| values: ValuePairs::TraitRefs(ExpectedFound { expected, found }), |
| }), |
| _, |
| _, |
| sup_placeholder @ ty::RePlaceholder(_), |
| )) if expected.def_id == found.def_id => Some(self.try_report_placeholders_trait( |
| Some(self.tcx().mk_region(ty::ReVar(*vid))), |
| cause, |
| None, |
| Some(*sup_placeholder), |
| expected.def_id, |
| expected.substs, |
| found.substs, |
| )), |
| |
| Some(RegionResolutionError::SubSupConflict( |
| vid, |
| _, |
| _, |
| _, |
| SubregionOrigin::Subtype(box TypeTrace { |
| cause, |
| values: ValuePairs::TraitRefs(ExpectedFound { expected, found }), |
| }), |
| sup_placeholder @ ty::RePlaceholder(_), |
| )) if expected.def_id == found.def_id => Some(self.try_report_placeholders_trait( |
| Some(self.tcx().mk_region(ty::ReVar(*vid))), |
| cause, |
| None, |
| Some(*sup_placeholder), |
| expected.def_id, |
| expected.substs, |
| found.substs, |
| )), |
| |
| Some(RegionResolutionError::ConcreteFailure( |
| SubregionOrigin::Subtype(box TypeTrace { |
| cause, |
| values: ValuePairs::TraitRefs(ExpectedFound { expected, found }), |
| }), |
| sub_region @ ty::RePlaceholder(_), |
| sup_region @ ty::RePlaceholder(_), |
| )) if expected.def_id == found.def_id => Some(self.try_report_placeholders_trait( |
| None, |
| cause, |
| Some(*sub_region), |
| Some(*sup_region), |
| expected.def_id, |
| expected.substs, |
| found.substs, |
| )), |
| |
| Some(RegionResolutionError::ConcreteFailure( |
| SubregionOrigin::Subtype(box TypeTrace { |
| cause, |
| values: ValuePairs::TraitRefs(ExpectedFound { expected, found }), |
| }), |
| sub_region @ ty::RePlaceholder(_), |
| sup_region, |
| )) if expected.def_id == found.def_id => Some(self.try_report_placeholders_trait( |
| Some(sup_region), |
| cause, |
| Some(*sub_region), |
| None, |
| expected.def_id, |
| expected.substs, |
| found.substs, |
| )), |
| |
| Some(RegionResolutionError::ConcreteFailure( |
| SubregionOrigin::Subtype(box TypeTrace { |
| cause, |
| values: ValuePairs::TraitRefs(ExpectedFound { expected, found }), |
| }), |
| sub_region, |
| sup_region @ ty::RePlaceholder(_), |
| )) if expected.def_id == found.def_id => Some(self.try_report_placeholders_trait( |
| Some(sub_region), |
| cause, |
| None, |
| Some(*sup_region), |
| expected.def_id, |
| expected.substs, |
| found.substs, |
| )), |
| |
| _ => None, |
| } |
| } |
| |
| // error[E0308]: implementation of `Foo` does not apply to enough lifetimes |
| // --> /home/nmatsakis/tmp/foo.rs:12:5 |
| // | |
| // 12 | all::<&'static u32>(); |
| // | ^^^^^^^^^^^^^^^^^^^ lifetime mismatch |
| // | |
| // = note: Due to a where-clause on the function `all`, |
| // = note: `T` must implement `...` for any two lifetimes `'1` and `'2`. |
| // = note: However, the type `T` only implements `...` for some specific lifetime `'2`. |
| fn try_report_placeholders_trait( |
| &self, |
| vid: Option<ty::Region<'tcx>>, |
| cause: &ObligationCause<'tcx>, |
| sub_placeholder: Option<ty::Region<'tcx>>, |
| sup_placeholder: Option<ty::Region<'tcx>>, |
| trait_def_id: DefId, |
| expected_substs: SubstsRef<'tcx>, |
| actual_substs: SubstsRef<'tcx>, |
| ) -> DiagnosticBuilder<'me> { |
| debug!( |
| "try_report_placeholders_trait(\ |
| vid={:?}, \ |
| sub_placeholder={:?}, \ |
| sup_placeholder={:?}, \ |
| trait_def_id={:?}, \ |
| expected_substs={:?}, \ |
| actual_substs={:?})", |
| vid, sub_placeholder, sup_placeholder, trait_def_id, expected_substs, actual_substs |
| ); |
| |
| let span = cause.span(self.tcx()); |
| let msg = format!( |
| "implementation of `{}` is not general enough", |
| self.tcx().def_path_str(trait_def_id), |
| ); |
| let mut err = self.tcx().sess.struct_span_err(span, &msg); |
| err.span_label( |
| self.tcx().def_span(trait_def_id), |
| format!("trait `{}` defined here", self.tcx().def_path_str(trait_def_id)), |
| ); |
| |
| let leading_ellipsis = if let ObligationCauseCode::ItemObligation(def_id) = cause.code { |
| err.span_label(span, "doesn't satisfy where-clause"); |
| err.span_label( |
| self.tcx().def_span(def_id), |
| &format!("due to a where-clause on `{}`...", self.tcx().def_path_str(def_id)), |
| ); |
| true |
| } else { |
| err.span_label(span, &msg); |
| false |
| }; |
| |
| let expected_trait_ref = self.infcx.resolve_vars_if_possible(&ty::TraitRef { |
| def_id: trait_def_id, |
| substs: expected_substs, |
| }); |
| let actual_trait_ref = self.infcx.resolve_vars_if_possible(&ty::TraitRef { |
| def_id: trait_def_id, |
| substs: actual_substs, |
| }); |
| |
| // Search the expected and actual trait references to see (a) |
| // whether the sub/sup placeholders appear in them (sometimes |
| // you have a trait ref like `T: Foo<fn(&u8)>`, where the |
| // placeholder was created as part of an inner type) and (b) |
| // whether the inference variable appears. In each case, |
| // assign a counter value in each case if so. |
| let mut counter = 0; |
| let mut has_sub = None; |
| let mut has_sup = None; |
| |
| let mut actual_has_vid = None; |
| let mut expected_has_vid = None; |
| |
| self.tcx().for_each_free_region(&expected_trait_ref, |r| { |
| if Some(r) == sub_placeholder && has_sub.is_none() { |
| has_sub = Some(counter); |
| counter += 1; |
| } else if Some(r) == sup_placeholder && has_sup.is_none() { |
| has_sup = Some(counter); |
| counter += 1; |
| } |
| |
| if Some(r) == vid && expected_has_vid.is_none() { |
| expected_has_vid = Some(counter); |
| counter += 1; |
| } |
| }); |
| |
| self.tcx().for_each_free_region(&actual_trait_ref, |r| { |
| if Some(r) == vid && actual_has_vid.is_none() { |
| actual_has_vid = Some(counter); |
| counter += 1; |
| } |
| }); |
| |
| let actual_self_ty_has_vid = self |
| .tcx() |
| .any_free_region_meets(&actual_trait_ref.self_ty(), |r| Some(r) == vid); |
| |
| let expected_self_ty_has_vid = self |
| .tcx() |
| .any_free_region_meets(&expected_trait_ref.self_ty(), |r| Some(r) == vid); |
| |
| let any_self_ty_has_vid = actual_self_ty_has_vid || expected_self_ty_has_vid; |
| |
| debug!( |
| "try_report_placeholders_trait: actual_has_vid={:?}", |
| actual_has_vid |
| ); |
| debug!( |
| "try_report_placeholders_trait: expected_has_vid={:?}", |
| expected_has_vid |
| ); |
| debug!("try_report_placeholders_trait: has_sub={:?}", has_sub); |
| debug!("try_report_placeholders_trait: has_sup={:?}", has_sup); |
| debug!( |
| "try_report_placeholders_trait: actual_self_ty_has_vid={:?}", |
| actual_self_ty_has_vid |
| ); |
| debug!( |
| "try_report_placeholders_trait: expected_self_ty_has_vid={:?}", |
| expected_self_ty_has_vid |
| ); |
| |
| self.explain_actual_impl_that_was_found( |
| &mut err, |
| sub_placeholder, |
| sup_placeholder, |
| has_sub, |
| has_sup, |
| expected_trait_ref, |
| actual_trait_ref, |
| vid, |
| expected_has_vid, |
| actual_has_vid, |
| any_self_ty_has_vid, |
| leading_ellipsis, |
| ); |
| |
| err |
| } |
| |
| /// Add notes with details about the expected and actual trait refs, with attention to cases |
| /// when placeholder regions are involved: either the trait or the self type containing |
| /// them needs to be mentioned the closest to the placeholders. |
| /// This makes the error messages read better, however at the cost of some complexity |
| /// due to the number of combinations we have to deal with. |
| fn explain_actual_impl_that_was_found( |
| &self, |
| err: &mut DiagnosticBuilder<'_>, |
| sub_placeholder: Option<ty::Region<'tcx>>, |
| sup_placeholder: Option<ty::Region<'tcx>>, |
| has_sub: Option<usize>, |
| has_sup: Option<usize>, |
| expected_trait_ref: ty::TraitRef<'tcx>, |
| actual_trait_ref: ty::TraitRef<'tcx>, |
| vid: Option<ty::Region<'tcx>>, |
| expected_has_vid: Option<usize>, |
| actual_has_vid: Option<usize>, |
| any_self_ty_has_vid: bool, |
| leading_ellipsis: bool, |
| ) { |
| // HACK(eddyb) maybe move this in a more central location. |
| #[derive(Copy, Clone)] |
| struct Highlighted<'tcx, T> { |
| tcx: TyCtxt<'tcx>, |
| highlight: RegionHighlightMode, |
| value: T, |
| } |
| |
| impl<'tcx, T> Highlighted<'tcx, T> { |
| fn map<U>(self, f: impl FnOnce(T) -> U) -> Highlighted<'tcx, U> { |
| Highlighted { |
| tcx: self.tcx, |
| highlight: self.highlight, |
| value: f(self.value), |
| } |
| } |
| } |
| |
| impl<'tcx, T> fmt::Display for Highlighted<'tcx, T> |
| where |
| T: for<'a, 'b, 'c> Print< |
| 'tcx, |
| FmtPrinter<'a, 'tcx, &'b mut fmt::Formatter<'c>>, |
| Error = fmt::Error, |
| >, |
| { |
| fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { |
| let mut printer = ty::print::FmtPrinter::new(self.tcx, f, Namespace::TypeNS); |
| printer.region_highlight_mode = self.highlight; |
| |
| self.value.print(printer)?; |
| Ok(()) |
| } |
| } |
| |
| // The weird thing here with the `maybe_highlighting_region` calls and the |
| // the match inside is meant to be like this: |
| // |
| // - The match checks whether the given things (placeholders, etc) appear |
| // in the types are about to print |
| // - Meanwhile, the `maybe_highlighting_region` calls set up |
| // highlights so that, if they do appear, we will replace |
| // them `'0` and whatever. (This replacement takes place |
| // inside the closure given to `maybe_highlighting_region`.) |
| // |
| // There is some duplication between the calls -- i.e., the |
| // `maybe_highlighting_region` checks if (e.g.) `has_sub` is |
| // None, an then we check again inside the closure, but this |
| // setup sort of minimized the number of calls and so form. |
| |
| let highlight_trait_ref = |trait_ref| Highlighted { |
| tcx: self.tcx(), |
| highlight: RegionHighlightMode::default(), |
| value: trait_ref, |
| }; |
| |
| let mut expected_trait_ref = highlight_trait_ref(expected_trait_ref); |
| expected_trait_ref.highlight.maybe_highlighting_region(sub_placeholder, has_sub); |
| expected_trait_ref.highlight.maybe_highlighting_region(sup_placeholder, has_sup); |
| err.note(&{ |
| let passive_voice = match (has_sub, has_sup) { |
| (Some(_), _) | (_, Some(_)) => any_self_ty_has_vid, |
| (None, None) => { |
| expected_trait_ref.highlight.maybe_highlighting_region(vid, expected_has_vid); |
| match expected_has_vid { |
| Some(_) => true, |
| None => any_self_ty_has_vid, |
| } |
| } |
| }; |
| |
| let mut note = if passive_voice { |
| format!( |
| "{}`{}` would have to be implemented for the type `{}`", |
| if leading_ellipsis { "..." } else { "" }, |
| expected_trait_ref, |
| expected_trait_ref.map(|tr| tr.self_ty()), |
| ) |
| } else { |
| format!( |
| "{}`{}` must implement `{}`", |
| if leading_ellipsis { "..." } else { "" }, |
| expected_trait_ref.map(|tr| tr.self_ty()), |
| expected_trait_ref, |
| ) |
| }; |
| |
| match (has_sub, has_sup) { |
| (Some(n1), Some(n2)) => { |
| let _ = write!(note, |
| ", for any two lifetimes `'{}` and `'{}`...", |
| std::cmp::min(n1, n2), |
| std::cmp::max(n1, n2), |
| ); |
| } |
| (Some(n), _) | (_, Some(n)) => { |
| let _ = write!(note, |
| ", for any lifetime `'{}`...", |
| n, |
| ); |
| } |
| (None, None) => if let Some(n) = expected_has_vid { |
| let _ = write!(note, |
| ", for some specific lifetime `'{}`...", |
| n, |
| ); |
| }, |
| } |
| |
| note |
| }); |
| |
| let mut actual_trait_ref = highlight_trait_ref(actual_trait_ref); |
| actual_trait_ref.highlight.maybe_highlighting_region(vid, actual_has_vid); |
| err.note(&{ |
| let passive_voice = match actual_has_vid { |
| Some(_) => any_self_ty_has_vid, |
| None => true, |
| }; |
| |
| let mut note = if passive_voice { |
| format!( |
| "...but `{}` is actually implemented for the type `{}`", |
| actual_trait_ref, |
| actual_trait_ref.map(|tr| tr.self_ty()), |
| ) |
| } else { |
| format!( |
| "...but `{}` actually implements `{}`", |
| actual_trait_ref.map(|tr| tr.self_ty()), |
| actual_trait_ref, |
| ) |
| }; |
| |
| if let Some(n) = actual_has_vid { |
| let _ = write!(note, ", for some specific lifetime `'{}`", n); |
| } |
| |
| note |
| }); |
| } |
| } |