| //! Error reporting machinery for lifetime errors. |
| |
| use rustc_data_structures::fx::FxIndexSet; |
| use rustc_errors::{Applicability, Diag, ErrorGuaranteed, MultiSpan}; |
| use rustc_hir as hir; |
| use rustc_hir::GenericBound::Trait; |
| use rustc_hir::QPath::Resolved; |
| use rustc_hir::WherePredicateKind::BoundPredicate; |
| use rustc_hir::def::Res::Def; |
| use rustc_hir::def_id::DefId; |
| use rustc_hir::intravisit::VisitorExt; |
| use rustc_hir::{PolyTraitRef, TyKind, WhereBoundPredicate}; |
| use rustc_infer::infer::{NllRegionVariableOrigin, SubregionOrigin}; |
| use rustc_middle::bug; |
| use rustc_middle::hir::place::PlaceBase; |
| use rustc_middle::mir::{AnnotationSource, ConstraintCategory, ReturnConstraint}; |
| use rustc_middle::ty::{ |
| self, GenericArgs, Region, RegionVid, Ty, TyCtxt, TypeFoldable, TypeVisitor, fold_regions, |
| }; |
| use rustc_span::{Ident, Span, kw}; |
| use rustc_trait_selection::error_reporting::InferCtxtErrorExt; |
| use rustc_trait_selection::error_reporting::infer::nice_region_error::{ |
| self, HirTraitObjectVisitor, NiceRegionError, TraitObjectVisitor, find_anon_type, |
| find_param_with_region, suggest_adding_lifetime_params, |
| }; |
| use rustc_trait_selection::infer::InferCtxtExt; |
| use rustc_trait_selection::traits::{Obligation, ObligationCtxt}; |
| use tracing::{debug, instrument, trace}; |
| |
| use super::{OutlivesSuggestionBuilder, RegionName, RegionNameSource}; |
| use crate::nll::ConstraintDescription; |
| use crate::region_infer::values::RegionElement; |
| use crate::region_infer::{BlameConstraint, TypeTest}; |
| use crate::session_diagnostics::{ |
| FnMutError, FnMutReturnTypeErr, GenericDoesNotLiveLongEnough, LifetimeOutliveErr, |
| LifetimeReturnCategoryErr, RequireStaticErr, VarHereDenote, |
| }; |
| use crate::universal_regions::DefiningTy; |
| use crate::{MirBorrowckCtxt, borrowck_errors, fluent_generated as fluent}; |
| |
| impl<'tcx> ConstraintDescription for ConstraintCategory<'tcx> { |
| fn description(&self) -> &'static str { |
| // Must end with a space. Allows for empty names to be provided. |
| match self { |
| ConstraintCategory::Assignment => "assignment ", |
| ConstraintCategory::Return(_) => "returning this value ", |
| ConstraintCategory::Yield => "yielding this value ", |
| ConstraintCategory::UseAsConst => "using this value as a constant ", |
| ConstraintCategory::UseAsStatic => "using this value as a static ", |
| ConstraintCategory::Cast { is_implicit_coercion: false, .. } => "cast ", |
| ConstraintCategory::Cast { is_implicit_coercion: true, .. } => "coercion ", |
| ConstraintCategory::CallArgument(_) => "argument ", |
| ConstraintCategory::TypeAnnotation(AnnotationSource::GenericArg) => "generic argument ", |
| ConstraintCategory::TypeAnnotation(_) => "type annotation ", |
| ConstraintCategory::SizedBound => "proving this value is `Sized` ", |
| ConstraintCategory::CopyBound => "copying this value ", |
| ConstraintCategory::OpaqueType => "opaque type ", |
| ConstraintCategory::ClosureUpvar(_) => "closure capture ", |
| ConstraintCategory::Usage => "this usage ", |
| ConstraintCategory::Predicate(_) |
| | ConstraintCategory::Boring |
| | ConstraintCategory::BoringNoLocation |
| | ConstraintCategory::Internal |
| | ConstraintCategory::OutlivesUnnameablePlaceholder(..) => "", |
| } |
| } |
| } |
| |
| /// A collection of errors encountered during region inference. This is needed to efficiently |
| /// report errors after borrow checking. |
| /// |
| /// Usually we expect this to either be empty or contain a small number of items, so we can avoid |
| /// allocation most of the time. |
| pub(crate) struct RegionErrors<'tcx>(Vec<(RegionErrorKind<'tcx>, ErrorGuaranteed)>, TyCtxt<'tcx>); |
| |
| impl<'tcx> RegionErrors<'tcx> { |
| pub(crate) fn new(tcx: TyCtxt<'tcx>) -> Self { |
| Self(vec![], tcx) |
| } |
| #[track_caller] |
| pub(crate) fn push(&mut self, val: impl Into<RegionErrorKind<'tcx>>) { |
| let val = val.into(); |
| let guar = self.1.sess.dcx().delayed_bug(format!("{val:?}")); |
| self.0.push((val, guar)); |
| } |
| pub(crate) fn is_empty(&self) -> bool { |
| self.0.is_empty() |
| } |
| pub(crate) fn into_iter( |
| self, |
| ) -> impl Iterator<Item = (RegionErrorKind<'tcx>, ErrorGuaranteed)> { |
| self.0.into_iter() |
| } |
| } |
| |
| impl std::fmt::Debug for RegionErrors<'_> { |
| fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result { |
| f.debug_tuple("RegionErrors").field(&self.0).finish() |
| } |
| } |
| |
| #[derive(Clone, Debug)] |
| pub(crate) enum RegionErrorKind<'tcx> { |
| /// A generic bound failure for a type test (`T: 'a`). |
| TypeTestError { type_test: TypeTest<'tcx> }, |
| |
| /// Higher-ranked subtyping error. |
| BoundUniversalRegionError { |
| /// The placeholder free region. |
| longer_fr: RegionVid, |
| /// The region element that erroneously must be outlived by `longer_fr`. |
| error_element: RegionElement, |
| /// The placeholder region. |
| placeholder: ty::PlaceholderRegion, |
| }, |
| |
| /// Any other lifetime error. |
| RegionError { |
| /// The origin of the region. |
| fr_origin: NllRegionVariableOrigin, |
| /// The region that should outlive `shorter_fr`. |
| longer_fr: RegionVid, |
| /// The region that should be shorter, but we can't prove it. |
| shorter_fr: RegionVid, |
| /// Indicates whether this is a reported error. We currently only report the first error |
| /// encountered and leave the rest unreported so as not to overwhelm the user. |
| is_reported: bool, |
| }, |
| } |
| |
| /// Information about the various region constraints involved in a borrow checker error. |
| #[derive(Clone, Debug)] |
| pub(crate) struct ErrorConstraintInfo<'tcx> { |
| // fr: outlived_fr |
| pub(super) fr: RegionVid, |
| pub(super) outlived_fr: RegionVid, |
| |
| // Category and span for best blame constraint |
| pub(super) category: ConstraintCategory<'tcx>, |
| pub(super) span: Span, |
| } |
| |
| impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> { |
| /// Converts a region inference variable into a `ty::Region` that |
| /// we can use for error reporting. If `r` is universally bound, |
| /// then we use the name that we have on record for it. If `r` is |
| /// existentially bound, then we check its inferred value and try |
| /// to find a good name from that. Returns `None` if we can't find |
| /// one (e.g., this is just some random part of the CFG). |
| pub(super) fn to_error_region(&self, r: RegionVid) -> Option<ty::Region<'tcx>> { |
| self.to_error_region_vid(r).and_then(|r| self.regioncx.region_definition(r).external_name) |
| } |
| |
| /// Returns the `RegionVid` corresponding to the region returned by |
| /// `to_error_region`. |
| pub(super) fn to_error_region_vid(&self, r: RegionVid) -> Option<RegionVid> { |
| if self.regioncx.universal_regions().is_universal_region(r) { |
| Some(r) |
| } else { |
| // We just want something nameable, even if it's not |
| // actually an upper bound. |
| let upper_bound = self.regioncx.approx_universal_upper_bound(r); |
| |
| if self.regioncx.upper_bound_in_region_scc(r, upper_bound) { |
| self.to_error_region_vid(upper_bound) |
| } else { |
| None |
| } |
| } |
| } |
| |
| /// Map the regions in the type to named regions, where possible. |
| fn name_regions<T>(&self, tcx: TyCtxt<'tcx>, ty: T) -> T |
| where |
| T: TypeFoldable<TyCtxt<'tcx>>, |
| { |
| fold_regions(tcx, ty, |region, _| match region.kind() { |
| ty::ReVar(vid) => self.to_error_region(vid).unwrap_or(region), |
| _ => region, |
| }) |
| } |
| |
| /// Returns `true` if a closure is inferred to be an `FnMut` closure. |
| fn is_closure_fn_mut(&self, fr: RegionVid) -> bool { |
| if let Some(r) = self.to_error_region(fr) |
| && let ty::ReLateParam(late_param) = r.kind() |
| && let ty::LateParamRegionKind::ClosureEnv = late_param.kind |
| && let DefiningTy::Closure(_, args) = self.regioncx.universal_regions().defining_ty |
| { |
| return args.as_closure().kind() == ty::ClosureKind::FnMut; |
| } |
| |
| false |
| } |
| |
| // For generic associated types (GATs) which implied 'static requirement |
| // from higher-ranked trait bounds (HRTB). Try to locate span of the trait |
| // and the span which bounded to the trait for adding 'static lifetime suggestion |
| #[allow(rustc::diagnostic_outside_of_impl)] |
| fn suggest_static_lifetime_for_gat_from_hrtb( |
| &self, |
| diag: &mut Diag<'_>, |
| lower_bound: RegionVid, |
| ) { |
| let tcx = self.infcx.tcx; |
| |
| // find generic associated types in the given region 'lower_bound' |
| let gat_id_and_generics = self |
| .regioncx |
| .placeholders_contained_in(lower_bound) |
| .map(|placeholder| { |
| if let Some(id) = placeholder.bound.kind.get_id() |
| && let Some(placeholder_id) = id.as_local() |
| && let gat_hir_id = tcx.local_def_id_to_hir_id(placeholder_id) |
| && let Some(generics_impl) = |
| tcx.parent_hir_node(tcx.parent_hir_id(gat_hir_id)).generics() |
| { |
| Some((gat_hir_id, generics_impl)) |
| } else { |
| None |
| } |
| }) |
| .collect::<Vec<_>>(); |
| debug!(?gat_id_and_generics); |
| |
| // Look for the where-bound which introduces the placeholder. |
| // As we're using the HIR, we need to handle both `for<'a> T: Trait<'a>` |
| // and `T: for<'a> Trait`<'a>. |
| let mut hrtb_bounds = vec![]; |
| gat_id_and_generics.iter().flatten().for_each(|&(gat_hir_id, generics)| { |
| for pred in generics.predicates { |
| let BoundPredicate(WhereBoundPredicate { bound_generic_params, bounds, .. }) = |
| pred.kind |
| else { |
| continue; |
| }; |
| if bound_generic_params |
| .iter() |
| .rfind(|bgp| tcx.local_def_id_to_hir_id(bgp.def_id) == gat_hir_id) |
| .is_some() |
| { |
| for bound in *bounds { |
| hrtb_bounds.push(bound); |
| } |
| } else { |
| for bound in *bounds { |
| if let Trait(trait_bound) = bound { |
| if trait_bound |
| .bound_generic_params |
| .iter() |
| .rfind(|bgp| tcx.local_def_id_to_hir_id(bgp.def_id) == gat_hir_id) |
| .is_some() |
| { |
| hrtb_bounds.push(bound); |
| return; |
| } |
| } |
| } |
| } |
| } |
| }); |
| debug!(?hrtb_bounds); |
| |
| let mut suggestions = vec![]; |
| hrtb_bounds.iter().for_each(|bound| { |
| let Trait(PolyTraitRef { trait_ref, span: trait_span, .. }) = bound else { |
| return; |
| }; |
| diag.span_note(*trait_span, fluent::borrowck_limitations_implies_static); |
| let Some(generics_fn) = tcx.hir_get_generics(self.body.source.def_id().expect_local()) |
| else { |
| return; |
| }; |
| let Def(_, trait_res_defid) = trait_ref.path.res else { |
| return; |
| }; |
| debug!(?generics_fn); |
| generics_fn.predicates.iter().for_each(|predicate| { |
| let BoundPredicate(WhereBoundPredicate { bounded_ty, bounds, .. }) = predicate.kind |
| else { |
| return; |
| }; |
| bounds.iter().for_each(|bd| { |
| if let Trait(PolyTraitRef { trait_ref: tr_ref, .. }) = bd |
| && let Def(_, res_defid) = tr_ref.path.res |
| && res_defid == trait_res_defid // trait id matches |
| && let TyKind::Path(Resolved(_, path)) = bounded_ty.kind |
| && let Def(_, defid) = path.res |
| && generics_fn.params |
| .iter() |
| .rfind(|param| param.def_id.to_def_id() == defid) |
| .is_some() |
| { |
| suggestions.push((predicate.span.shrink_to_hi(), " + 'static".to_string())); |
| } |
| }); |
| }); |
| }); |
| if suggestions.len() > 0 { |
| suggestions.dedup(); |
| diag.multipart_suggestion_verbose( |
| fluent::borrowck_restrict_to_static, |
| suggestions, |
| Applicability::MaybeIncorrect, |
| ); |
| } |
| } |
| |
| /// Produces nice borrowck error diagnostics for all the errors collected in `nll_errors`. |
| pub(crate) fn report_region_errors(&mut self, nll_errors: RegionErrors<'tcx>) { |
| // Iterate through all the errors, producing a diagnostic for each one. The diagnostics are |
| // buffered in the `MirBorrowckCtxt`. |
| let mut outlives_suggestion = OutlivesSuggestionBuilder::default(); |
| for (nll_error, _) in nll_errors.into_iter() { |
| match nll_error { |
| RegionErrorKind::TypeTestError { type_test } => { |
| // Try to convert the lower-bound region into something named we can print for |
| // the user. |
| let lower_bound_region = self.to_error_region(type_test.lower_bound); |
| |
| let type_test_span = type_test.span; |
| |
| if let Some(lower_bound_region) = lower_bound_region { |
| let generic_ty = self.name_regions( |
| self.infcx.tcx, |
| type_test.generic_kind.to_ty(self.infcx.tcx), |
| ); |
| let origin = |
| SubregionOrigin::RelateParamBound(type_test_span, generic_ty, None); |
| self.buffer_error(self.infcx.err_ctxt().construct_generic_bound_failure( |
| self.body.source.def_id().expect_local(), |
| type_test_span, |
| Some(origin), |
| self.name_regions(self.infcx.tcx, type_test.generic_kind), |
| lower_bound_region, |
| )); |
| } else { |
| // FIXME. We should handle this case better. It |
| // indicates that we have e.g., some region variable |
| // whose value is like `'a+'b` where `'a` and `'b` are |
| // distinct unrelated universal regions that are not |
| // known to outlive one another. It'd be nice to have |
| // some examples where this arises to decide how best |
| // to report it; we could probably handle it by |
| // iterating over the universal regions and reporting |
| // an error that multiple bounds are required. |
| let mut diag = self.dcx().create_err(GenericDoesNotLiveLongEnough { |
| kind: type_test.generic_kind.to_string(), |
| span: type_test_span, |
| }); |
| |
| // Add notes and suggestions for the case of 'static lifetime |
| // implied but not specified when a generic associated types |
| // are from higher-ranked trait bounds |
| self.suggest_static_lifetime_for_gat_from_hrtb( |
| &mut diag, |
| type_test.lower_bound, |
| ); |
| |
| self.buffer_error(diag); |
| } |
| } |
| |
| RegionErrorKind::BoundUniversalRegionError { |
| longer_fr, |
| placeholder, |
| error_element, |
| } => { |
| let error_vid = self.regioncx.region_from_element(longer_fr, &error_element); |
| |
| // Find the code to blame for the fact that `longer_fr` outlives `error_fr`. |
| let cause = self |
| .regioncx |
| .best_blame_constraint( |
| longer_fr, |
| NllRegionVariableOrigin::Placeholder(placeholder), |
| error_vid, |
| ) |
| .0 |
| .cause; |
| |
| let universe = placeholder.universe; |
| let universe_info = self.regioncx.universe_info(universe); |
| |
| universe_info.report_erroneous_element(self, placeholder, error_element, cause); |
| } |
| |
| RegionErrorKind::RegionError { fr_origin, longer_fr, shorter_fr, is_reported } => { |
| if is_reported { |
| self.report_region_error( |
| longer_fr, |
| fr_origin, |
| shorter_fr, |
| &mut outlives_suggestion, |
| ); |
| } else { |
| // We only report the first error, so as not to overwhelm the user. See |
| // `RegRegionErrorKind` docs. |
| // |
| // FIXME: currently we do nothing with these, but perhaps we can do better? |
| // FIXME: try collecting these constraints on the outlives suggestion |
| // builder. Does it make the suggestions any better? |
| debug!( |
| "Unreported region error: can't prove that {:?}: {:?}", |
| longer_fr, shorter_fr |
| ); |
| } |
| } |
| } |
| } |
| |
| // Emit one outlives suggestions for each MIR def we borrowck |
| outlives_suggestion.add_suggestion(self); |
| } |
| |
| /// Report an error because the universal region `fr` was required to outlive |
| /// `outlived_fr` but it is not known to do so. For example: |
| /// |
| /// ```compile_fail |
| /// fn foo<'a, 'b>(x: &'a u32) -> &'b u32 { x } |
| /// ``` |
| /// |
| /// Here we would be invoked with `fr = 'a` and `outlived_fr = 'b`. |
| // FIXME: make this translatable |
| #[allow(rustc::diagnostic_outside_of_impl)] |
| #[allow(rustc::untranslatable_diagnostic)] |
| pub(crate) fn report_region_error( |
| &mut self, |
| fr: RegionVid, |
| fr_origin: NllRegionVariableOrigin, |
| outlived_fr: RegionVid, |
| outlives_suggestion: &mut OutlivesSuggestionBuilder, |
| ) { |
| debug!("report_region_error(fr={:?}, outlived_fr={:?})", fr, outlived_fr); |
| |
| let (blame_constraint, path) = |
| self.regioncx.best_blame_constraint(fr, fr_origin, outlived_fr); |
| let BlameConstraint { category, cause, variance_info, .. } = blame_constraint; |
| |
| debug!("report_region_error: category={:?} {:?} {:?}", category, cause, variance_info); |
| |
| // Check if we can use one of the "nice region errors". |
| if let (Some(f), Some(o)) = (self.to_error_region(fr), self.to_error_region(outlived_fr)) { |
| let infer_err = self.infcx.err_ctxt(); |
| let nice = |
| NiceRegionError::new_from_span(&infer_err, self.mir_def_id(), cause.span, o, f); |
| if let Some(diag) = nice.try_report_from_nll() { |
| self.buffer_error(diag); |
| return; |
| } |
| } |
| |
| let (fr_is_local, outlived_fr_is_local): (bool, bool) = ( |
| self.regioncx.universal_regions().is_local_free_region(fr), |
| self.regioncx.universal_regions().is_local_free_region(outlived_fr), |
| ); |
| |
| debug!( |
| "report_region_error: fr_is_local={:?} outlived_fr_is_local={:?} category={:?}", |
| fr_is_local, outlived_fr_is_local, category |
| ); |
| |
| let errci = ErrorConstraintInfo { fr, outlived_fr, category, span: cause.span }; |
| |
| let mut diag = match (category, fr_is_local, outlived_fr_is_local) { |
| (ConstraintCategory::Return(kind), true, false) if self.is_closure_fn_mut(fr) => { |
| self.report_fnmut_error(&errci, kind) |
| } |
| (ConstraintCategory::Assignment, true, false) |
| | (ConstraintCategory::CallArgument(_), true, false) => { |
| let mut db = self.report_escaping_data_error(&errci); |
| |
| outlives_suggestion.intermediate_suggestion(self, &errci, &mut db); |
| outlives_suggestion.collect_constraint(fr, outlived_fr); |
| |
| db |
| } |
| _ => { |
| let mut db = self.report_general_error(&errci); |
| |
| outlives_suggestion.intermediate_suggestion(self, &errci, &mut db); |
| outlives_suggestion.collect_constraint(fr, outlived_fr); |
| |
| db |
| } |
| }; |
| |
| match variance_info { |
| ty::VarianceDiagInfo::None => {} |
| ty::VarianceDiagInfo::Invariant { ty, param_index } => { |
| let (desc, note) = match ty.kind() { |
| ty::RawPtr(ty, mutbl) => { |
| assert_eq!(*mutbl, hir::Mutability::Mut); |
| ( |
| format!("a mutable pointer to `{}`", ty), |
| "mutable pointers are invariant over their type parameter".to_string(), |
| ) |
| } |
| ty::Ref(_, inner_ty, mutbl) => { |
| assert_eq!(*mutbl, hir::Mutability::Mut); |
| ( |
| format!("a mutable reference to `{inner_ty}`"), |
| "mutable references are invariant over their type parameter" |
| .to_string(), |
| ) |
| } |
| ty::Adt(adt, args) => { |
| let generic_arg = args[param_index as usize]; |
| let identity_args = |
| GenericArgs::identity_for_item(self.infcx.tcx, adt.did()); |
| let base_ty = Ty::new_adt(self.infcx.tcx, *adt, identity_args); |
| let base_generic_arg = identity_args[param_index as usize]; |
| let adt_desc = adt.descr(); |
| |
| let desc = format!( |
| "the type `{ty}`, which makes the generic argument `{generic_arg}` invariant" |
| ); |
| let note = format!( |
| "the {adt_desc} `{base_ty}` is invariant over the parameter `{base_generic_arg}`" |
| ); |
| (desc, note) |
| } |
| ty::FnDef(def_id, _) => { |
| let name = self.infcx.tcx.item_name(*def_id); |
| let identity_args = GenericArgs::identity_for_item(self.infcx.tcx, *def_id); |
| let desc = format!("a function pointer to `{name}`"); |
| let note = format!( |
| "the function `{name}` is invariant over the parameter `{}`", |
| identity_args[param_index as usize] |
| ); |
| (desc, note) |
| } |
| _ => panic!("Unexpected type {ty:?}"), |
| }; |
| diag.note(format!("requirement occurs because of {desc}",)); |
| diag.note(note); |
| diag.help("see <https://doc.rust-lang.org/nomicon/subtyping.html> for more information about variance"); |
| } |
| } |
| |
| self.add_placeholder_from_predicate_note(&mut diag, &path); |
| self.add_sized_or_copy_bound_info(&mut diag, category, &path); |
| |
| self.buffer_error(diag); |
| } |
| |
| /// Report a specialized error when `FnMut` closures return a reference to a captured variable. |
| /// This function expects `fr` to be local and `outlived_fr` to not be local. |
| /// |
| /// ```text |
| /// error: captured variable cannot escape `FnMut` closure body |
| /// --> $DIR/issue-53040.rs:15:8 |
| /// | |
| /// LL | || &mut v; |
| /// | -- ^^^^^^ creates a reference to a captured variable which escapes the closure body |
| /// | | |
| /// | inferred to be a `FnMut` closure |
| /// | |
| /// = note: `FnMut` closures only have access to their captured variables while they are |
| /// executing... |
| /// = note: ...therefore, returned references to captured variables will escape the closure |
| /// ``` |
| #[allow(rustc::diagnostic_outside_of_impl)] // FIXME |
| fn report_fnmut_error( |
| &self, |
| errci: &ErrorConstraintInfo<'tcx>, |
| kind: ReturnConstraint, |
| ) -> Diag<'infcx> { |
| let ErrorConstraintInfo { outlived_fr, span, .. } = errci; |
| |
| let mut output_ty = self.regioncx.universal_regions().unnormalized_output_ty; |
| if let ty::Alias(ty::Opaque, ty::AliasTy { def_id, .. }) = *output_ty.kind() { |
| output_ty = self.infcx.tcx.type_of(def_id).instantiate_identity() |
| }; |
| |
| debug!("report_fnmut_error: output_ty={:?}", output_ty); |
| |
| let err = FnMutError { |
| span: *span, |
| ty_err: match output_ty.kind() { |
| ty::Coroutine(def, ..) if self.infcx.tcx.coroutine_is_async(*def) => { |
| FnMutReturnTypeErr::ReturnAsyncBlock { span: *span } |
| } |
| _ if output_ty.contains_closure() => { |
| FnMutReturnTypeErr::ReturnClosure { span: *span } |
| } |
| _ => FnMutReturnTypeErr::ReturnRef { span: *span }, |
| }, |
| }; |
| |
| let mut diag = self.dcx().create_err(err); |
| |
| if let ReturnConstraint::ClosureUpvar(upvar_field) = kind { |
| let def_id = match self.regioncx.universal_regions().defining_ty { |
| DefiningTy::Closure(def_id, _) => def_id, |
| ty => bug!("unexpected DefiningTy {:?}", ty), |
| }; |
| |
| let captured_place = &self.upvars[upvar_field.index()].place; |
| let defined_hir = match captured_place.base { |
| PlaceBase::Local(hirid) => Some(hirid), |
| PlaceBase::Upvar(upvar) => Some(upvar.var_path.hir_id), |
| _ => None, |
| }; |
| |
| if let Some(def_hir) = defined_hir { |
| let upvars_map = self.infcx.tcx.upvars_mentioned(def_id).unwrap(); |
| let upvar_def_span = self.infcx.tcx.hir_span(def_hir); |
| let upvar_span = upvars_map.get(&def_hir).unwrap().span; |
| diag.subdiagnostic(VarHereDenote::Defined { span: upvar_def_span }); |
| diag.subdiagnostic(VarHereDenote::Captured { span: upvar_span }); |
| } |
| } |
| |
| if let Some(fr_span) = self.give_region_a_name(*outlived_fr).unwrap().span() { |
| diag.subdiagnostic(VarHereDenote::FnMutInferred { span: fr_span }); |
| } |
| |
| self.suggest_move_on_borrowing_closure(&mut diag); |
| |
| diag |
| } |
| |
| /// Reports an error specifically for when data is escaping a closure. |
| /// |
| /// ```text |
| /// error: borrowed data escapes outside of function |
| /// --> $DIR/lifetime-bound-will-change-warning.rs:44:5 |
| /// | |
| /// LL | fn test2<'a>(x: &'a Box<Fn()+'a>) { |
| /// | - `x` is a reference that is only valid in the function body |
| /// LL | // but ref_obj will not, so warn. |
| /// LL | ref_obj(x) |
| /// | ^^^^^^^^^^ `x` escapes the function body here |
| /// ``` |
| #[instrument(level = "debug", skip(self))] |
| fn report_escaping_data_error(&self, errci: &ErrorConstraintInfo<'tcx>) -> Diag<'infcx> { |
| let ErrorConstraintInfo { span, category, .. } = errci; |
| |
| let fr_name_and_span = self.regioncx.get_var_name_and_span_for_region( |
| self.infcx.tcx, |
| self.body, |
| &self.local_names(), |
| &self.upvars, |
| errci.fr, |
| ); |
| let outlived_fr_name_and_span = self.regioncx.get_var_name_and_span_for_region( |
| self.infcx.tcx, |
| self.body, |
| &self.local_names(), |
| &self.upvars, |
| errci.outlived_fr, |
| ); |
| |
| let escapes_from = |
| self.infcx.tcx.def_descr(self.regioncx.universal_regions().defining_ty.def_id()); |
| |
| // Revert to the normal error in these cases. |
| // Assignments aren't "escapes" in function items. |
| if (fr_name_and_span.is_none() && outlived_fr_name_and_span.is_none()) |
| || (*category == ConstraintCategory::Assignment |
| && self.regioncx.universal_regions().defining_ty.is_fn_def()) |
| || self.regioncx.universal_regions().defining_ty.is_const() |
| { |
| return self.report_general_error(errci); |
| } |
| |
| let mut diag = |
| borrowck_errors::borrowed_data_escapes_closure(self.infcx.tcx, *span, escapes_from); |
| |
| if let Some((Some(outlived_fr_name), outlived_fr_span)) = outlived_fr_name_and_span { |
| // FIXME: make this translatable |
| #[allow(rustc::diagnostic_outside_of_impl)] |
| #[allow(rustc::untranslatable_diagnostic)] |
| diag.span_label( |
| outlived_fr_span, |
| format!("`{outlived_fr_name}` declared here, outside of the {escapes_from} body",), |
| ); |
| } |
| |
| // FIXME: make this translatable |
| #[allow(rustc::diagnostic_outside_of_impl)] |
| #[allow(rustc::untranslatable_diagnostic)] |
| if let Some((Some(fr_name), fr_span)) = fr_name_and_span { |
| diag.span_label( |
| fr_span, |
| format!( |
| "`{fr_name}` is a reference that is only valid in the {escapes_from} body", |
| ), |
| ); |
| |
| diag.span_label(*span, format!("`{fr_name}` escapes the {escapes_from} body here")); |
| } |
| |
| // Only show an extra note if we can find an 'error region' for both of the region |
| // variables. This avoids showing a noisy note that just mentions 'synthetic' regions |
| // that don't help the user understand the error. |
| match (self.to_error_region(errci.fr), self.to_error_region(errci.outlived_fr)) { |
| (Some(f), Some(o)) => { |
| self.maybe_suggest_constrain_dyn_trait_impl(&mut diag, f, o, category); |
| |
| let fr_region_name = self.give_region_a_name(errci.fr).unwrap(); |
| fr_region_name.highlight_region_name(&mut diag); |
| let outlived_fr_region_name = self.give_region_a_name(errci.outlived_fr).unwrap(); |
| outlived_fr_region_name.highlight_region_name(&mut diag); |
| |
| // FIXME: make this translatable |
| #[allow(rustc::diagnostic_outside_of_impl)] |
| #[allow(rustc::untranslatable_diagnostic)] |
| diag.span_label( |
| *span, |
| format!( |
| "{}requires that `{}` must outlive `{}`", |
| category.description(), |
| fr_region_name, |
| outlived_fr_region_name, |
| ), |
| ); |
| } |
| _ => {} |
| } |
| |
| diag |
| } |
| |
| /// Reports a region inference error for the general case with named/synthesized lifetimes to |
| /// explain what is happening. |
| /// |
| /// ```text |
| /// error: unsatisfied lifetime constraints |
| /// --> $DIR/regions-creating-enums3.rs:17:5 |
| /// | |
| /// LL | fn mk_add_bad1<'a,'b>(x: &'a ast<'a>, y: &'b ast<'b>) -> ast<'a> { |
| /// | -- -- lifetime `'b` defined here |
| /// | | |
| /// | lifetime `'a` defined here |
| /// LL | ast::add(x, y) |
| /// | ^^^^^^^^^^^^^^ function was supposed to return data with lifetime `'a` but it |
| /// | is returning data with lifetime `'b` |
| /// ``` |
| #[allow(rustc::diagnostic_outside_of_impl)] // FIXME |
| fn report_general_error(&self, errci: &ErrorConstraintInfo<'tcx>) -> Diag<'infcx> { |
| let ErrorConstraintInfo { fr, outlived_fr, span, category, .. } = errci; |
| |
| let mir_def_name = self.infcx.tcx.def_descr(self.mir_def_id().to_def_id()); |
| |
| let err = LifetimeOutliveErr { span: *span }; |
| let mut diag = self.dcx().create_err(err); |
| |
| // In certain scenarios, such as the one described in issue #118021, |
| // we might encounter a lifetime that cannot be named. |
| // These situations are bound to result in errors. |
| // To prevent an immediate ICE, we opt to create a dummy name instead. |
| let fr_name = self.give_region_a_name(*fr).unwrap_or(RegionName { |
| name: kw::UnderscoreLifetime, |
| source: RegionNameSource::Static, |
| }); |
| fr_name.highlight_region_name(&mut diag); |
| let outlived_fr_name = self.give_region_a_name(*outlived_fr).unwrap(); |
| outlived_fr_name.highlight_region_name(&mut diag); |
| |
| let err_category = if matches!(category, ConstraintCategory::Return(_)) |
| && self.regioncx.universal_regions().is_local_free_region(*outlived_fr) |
| { |
| LifetimeReturnCategoryErr::WrongReturn { |
| span: *span, |
| mir_def_name, |
| outlived_fr_name, |
| fr_name: &fr_name, |
| } |
| } else { |
| LifetimeReturnCategoryErr::ShortReturn { |
| span: *span, |
| category_desc: category.description(), |
| free_region_name: &fr_name, |
| outlived_fr_name, |
| } |
| }; |
| |
| diag.subdiagnostic(err_category); |
| |
| self.add_static_impl_trait_suggestion(&mut diag, *fr, fr_name, *outlived_fr); |
| self.suggest_adding_lifetime_params(&mut diag, *fr, *outlived_fr); |
| self.suggest_move_on_borrowing_closure(&mut diag); |
| self.suggest_deref_closure_return(&mut diag); |
| |
| diag |
| } |
| |
| /// Adds a suggestion to errors where an `impl Trait` is returned. |
| /// |
| /// ```text |
| /// help: to allow this `impl Trait` to capture borrowed data with lifetime `'1`, add `'_` as |
| /// a constraint |
| /// | |
| /// LL | fn iter_values_anon(&self) -> impl Iterator<Item=u32> + 'a { |
| /// | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ |
| /// ``` |
| #[allow(rustc::diagnostic_outside_of_impl)] |
| #[allow(rustc::untranslatable_diagnostic)] // FIXME: make this translatable |
| fn add_static_impl_trait_suggestion( |
| &self, |
| diag: &mut Diag<'_>, |
| fr: RegionVid, |
| // We need to pass `fr_name` - computing it again will label it twice. |
| fr_name: RegionName, |
| outlived_fr: RegionVid, |
| ) { |
| if let (Some(f), Some(outlived_f)) = |
| (self.to_error_region(fr), self.to_error_region(outlived_fr)) |
| { |
| if outlived_f.kind() != ty::ReStatic { |
| return; |
| } |
| let suitable_region = self.infcx.tcx.is_suitable_region(self.mir_def_id(), f); |
| let Some(suitable_region) = suitable_region else { |
| return; |
| }; |
| |
| let fn_returns = self.infcx.tcx.return_type_impl_or_dyn_traits(suitable_region.scope); |
| |
| let param = if let Some(param) = |
| find_param_with_region(self.infcx.tcx, self.mir_def_id(), f, outlived_f) |
| { |
| param |
| } else { |
| return; |
| }; |
| |
| let lifetime = |
| if f.is_named(self.infcx.tcx) { fr_name.name } else { kw::UnderscoreLifetime }; |
| |
| let arg = match param.param.pat.simple_ident() { |
| Some(simple_ident) => format!("argument `{simple_ident}`"), |
| None => "the argument".to_string(), |
| }; |
| let captures = format!("captures data from {arg}"); |
| |
| if !fn_returns.is_empty() { |
| nice_region_error::suggest_new_region_bound( |
| self.infcx.tcx, |
| diag, |
| fn_returns, |
| lifetime.to_string(), |
| Some(arg), |
| captures, |
| Some((param.param_ty_span, param.param_ty.to_string())), |
| Some(suitable_region.scope), |
| ); |
| return; |
| } |
| |
| let Some((alias_tys, alias_span, lt_addition_span)) = self |
| .infcx |
| .tcx |
| .return_type_impl_or_dyn_traits_with_type_alias(suitable_region.scope) |
| else { |
| return; |
| }; |
| |
| // in case the return type of the method is a type alias |
| let mut spans_suggs: Vec<_> = Vec::new(); |
| for alias_ty in alias_tys { |
| if alias_ty.span.desugaring_kind().is_some() { |
| // Skip `async` desugaring `impl Future`. |
| } |
| if let TyKind::TraitObject(_, lt) = alias_ty.kind { |
| if lt.kind == hir::LifetimeKind::ImplicitObjectLifetimeDefault { |
| spans_suggs.push((lt.ident.span.shrink_to_hi(), " + 'a".to_string())); |
| } else { |
| spans_suggs.push((lt.ident.span, "'a".to_string())); |
| } |
| } |
| } |
| |
| if let Some(lt_addition_span) = lt_addition_span { |
| spans_suggs.push((lt_addition_span, "'a, ".to_string())); |
| } else { |
| spans_suggs.push((alias_span.shrink_to_hi(), "<'a>".to_string())); |
| } |
| |
| diag.multipart_suggestion_verbose( |
| format!( |
| "to declare that the trait object {captures}, you can add a lifetime parameter `'a` in the type alias" |
| ), |
| spans_suggs, |
| Applicability::MaybeIncorrect, |
| ); |
| } |
| } |
| |
| fn maybe_suggest_constrain_dyn_trait_impl( |
| &self, |
| diag: &mut Diag<'_>, |
| f: Region<'tcx>, |
| o: Region<'tcx>, |
| category: &ConstraintCategory<'tcx>, |
| ) { |
| if !o.is_static() { |
| return; |
| } |
| |
| let tcx = self.infcx.tcx; |
| |
| let instance = if let ConstraintCategory::CallArgument(Some(func_ty)) = category { |
| let (fn_did, args) = match func_ty.kind() { |
| ty::FnDef(fn_did, args) => (fn_did, args), |
| _ => return, |
| }; |
| debug!(?fn_did, ?args); |
| |
| // Only suggest this on function calls, not closures |
| let ty = tcx.type_of(fn_did).instantiate_identity(); |
| debug!("ty: {:?}, ty.kind: {:?}", ty, ty.kind()); |
| if let ty::Closure(_, _) = ty.kind() { |
| return; |
| } |
| |
| if let Ok(Some(instance)) = ty::Instance::try_resolve( |
| tcx, |
| self.infcx.typing_env(self.infcx.param_env), |
| *fn_did, |
| self.infcx.resolve_vars_if_possible(args), |
| ) { |
| instance |
| } else { |
| return; |
| } |
| } else { |
| return; |
| }; |
| |
| let param = match find_param_with_region(tcx, self.mir_def_id(), f, o) { |
| Some(param) => param, |
| None => return, |
| }; |
| debug!(?param); |
| |
| let mut visitor = TraitObjectVisitor(FxIndexSet::default()); |
| visitor.visit_ty(param.param_ty); |
| |
| let Some((ident, self_ty)) = NiceRegionError::get_impl_ident_and_self_ty_from_trait( |
| tcx, |
| instance.def_id(), |
| &visitor.0, |
| ) else { |
| return; |
| }; |
| |
| self.suggest_constrain_dyn_trait_in_impl(diag, &visitor.0, ident, self_ty); |
| } |
| |
| #[allow(rustc::diagnostic_outside_of_impl)] |
| #[instrument(skip(self, err), level = "debug")] |
| fn suggest_constrain_dyn_trait_in_impl( |
| &self, |
| err: &mut Diag<'_>, |
| found_dids: &FxIndexSet<DefId>, |
| ident: Ident, |
| self_ty: &hir::Ty<'_>, |
| ) -> bool { |
| debug!("err: {:#?}", err); |
| let mut suggested = false; |
| for found_did in found_dids { |
| let mut traits = vec![]; |
| let mut hir_v = HirTraitObjectVisitor(&mut traits, *found_did); |
| hir_v.visit_ty_unambig(self_ty); |
| debug!("trait spans found: {:?}", traits); |
| for span in &traits { |
| let mut multi_span: MultiSpan = vec![*span].into(); |
| multi_span.push_span_label(*span, fluent::borrowck_implicit_static); |
| multi_span.push_span_label(ident.span, fluent::borrowck_implicit_static_introduced); |
| err.subdiagnostic(RequireStaticErr::UsedImpl { multi_span }); |
| err.span_suggestion_verbose( |
| span.shrink_to_hi(), |
| fluent::borrowck_implicit_static_relax, |
| " + '_", |
| Applicability::MaybeIncorrect, |
| ); |
| suggested = true; |
| } |
| } |
| suggested |
| } |
| |
| fn suggest_adding_lifetime_params(&self, diag: &mut Diag<'_>, sub: RegionVid, sup: RegionVid) { |
| let (Some(sub), Some(sup)) = (self.to_error_region(sub), self.to_error_region(sup)) else { |
| return; |
| }; |
| |
| let Some((ty_sub, _)) = self |
| .infcx |
| .tcx |
| .is_suitable_region(self.mir_def_id(), sub) |
| .and_then(|_| find_anon_type(self.infcx.tcx, self.mir_def_id(), sub)) |
| else { |
| return; |
| }; |
| |
| let Some((ty_sup, _)) = self |
| .infcx |
| .tcx |
| .is_suitable_region(self.mir_def_id(), sup) |
| .and_then(|_| find_anon_type(self.infcx.tcx, self.mir_def_id(), sup)) |
| else { |
| return; |
| }; |
| |
| suggest_adding_lifetime_params( |
| self.infcx.tcx, |
| diag, |
| self.mir_def_id(), |
| sub, |
| ty_sup, |
| ty_sub, |
| ); |
| } |
| |
| #[allow(rustc::diagnostic_outside_of_impl)] |
| /// When encountering a lifetime error caused by the return type of a closure, check the |
| /// corresponding trait bound and see if dereferencing the closure return value would satisfy |
| /// them. If so, we produce a structured suggestion. |
| fn suggest_deref_closure_return(&self, diag: &mut Diag<'_>) { |
| let tcx = self.infcx.tcx; |
| |
| // Get the closure return value and type. |
| let closure_def_id = self.mir_def_id(); |
| let hir::Node::Expr( |
| closure_expr @ hir::Expr { |
| kind: hir::ExprKind::Closure(hir::Closure { body, .. }), .. |
| }, |
| ) = tcx.hir_node_by_def_id(closure_def_id) |
| else { |
| return; |
| }; |
| let ty::Closure(_, args) = *tcx.type_of(closure_def_id).instantiate_identity().kind() |
| else { |
| return; |
| }; |
| let args = args.as_closure(); |
| |
| // Make sure that the parent expression is a method call. |
| let parent_expr_id = tcx.parent_hir_id(self.mir_hir_id()); |
| let hir::Node::Expr( |
| parent_expr @ hir::Expr { |
| kind: hir::ExprKind::MethodCall(_, rcvr, call_args, _), .. |
| }, |
| ) = tcx.hir_node(parent_expr_id) |
| else { |
| return; |
| }; |
| let typeck_results = tcx.typeck(self.mir_def_id()); |
| |
| // We don't use `ty.peel_refs()` to get the number of `*`s needed to get the root type. |
| let liberated_sig = tcx.liberate_late_bound_regions(closure_def_id.to_def_id(), args.sig()); |
| let mut peeled_ty = liberated_sig.output(); |
| let mut count = 0; |
| while let ty::Ref(_, ref_ty, _) = *peeled_ty.kind() { |
| peeled_ty = ref_ty; |
| count += 1; |
| } |
| if !self.infcx.type_is_copy_modulo_regions(self.infcx.param_env, peeled_ty) { |
| return; |
| } |
| |
| // Build a new closure where the return type is an owned value, instead of a ref. |
| let closure_sig_as_fn_ptr_ty = Ty::new_fn_ptr( |
| tcx, |
| ty::Binder::dummy(tcx.mk_fn_sig( |
| liberated_sig.inputs().iter().copied(), |
| peeled_ty, |
| liberated_sig.c_variadic, |
| hir::Safety::Safe, |
| rustc_abi::ExternAbi::Rust, |
| )), |
| ); |
| let closure_ty = Ty::new_closure( |
| tcx, |
| closure_def_id.to_def_id(), |
| ty::ClosureArgs::new( |
| tcx, |
| ty::ClosureArgsParts { |
| parent_args: args.parent_args(), |
| closure_kind_ty: args.kind_ty(), |
| tupled_upvars_ty: args.tupled_upvars_ty(), |
| closure_sig_as_fn_ptr_ty, |
| }, |
| ) |
| .args, |
| ); |
| |
| let Some((closure_arg_pos, _)) = |
| call_args.iter().enumerate().find(|(_, arg)| arg.hir_id == closure_expr.hir_id) |
| else { |
| return; |
| }; |
| // Get the type for the parameter corresponding to the argument the closure with the |
| // lifetime error we had. |
| let Some(method_def_id) = typeck_results.type_dependent_def_id(parent_expr.hir_id) else { |
| return; |
| }; |
| let Some(input_arg) = tcx |
| .fn_sig(method_def_id) |
| .skip_binder() |
| .inputs() |
| .skip_binder() |
| // Methods have a `self` arg, so `pos` is actually `+ 1` to match the method call arg. |
| .get(closure_arg_pos + 1) |
| else { |
| return; |
| }; |
| // If this isn't a param, then we can't substitute a new closure. |
| let ty::Param(closure_param) = input_arg.kind() else { return }; |
| |
| // Get the arguments for the found method, only specifying that `Self` is the receiver type. |
| let Some(possible_rcvr_ty) = typeck_results.node_type_opt(rcvr.hir_id) else { return }; |
| let args = GenericArgs::for_item(tcx, method_def_id, |param, _| { |
| if let ty::GenericParamDefKind::Lifetime = param.kind { |
| tcx.lifetimes.re_erased.into() |
| } else if param.index == 0 && param.name == kw::SelfUpper { |
| possible_rcvr_ty.into() |
| } else if param.index == closure_param.index { |
| closure_ty.into() |
| } else { |
| self.infcx.var_for_def(parent_expr.span, param) |
| } |
| }); |
| |
| let preds = tcx.predicates_of(method_def_id).instantiate(tcx, args); |
| |
| let ocx = ObligationCtxt::new(&self.infcx); |
| ocx.register_obligations(preds.iter().map(|(pred, span)| { |
| trace!(?pred); |
| Obligation::misc(tcx, span, self.mir_def_id(), self.infcx.param_env, pred) |
| })); |
| |
| if ocx.evaluate_obligations_error_on_ambiguity().is_empty() && count > 0 { |
| diag.span_suggestion_verbose( |
| tcx.hir_body(*body).value.peel_blocks().span.shrink_to_lo(), |
| fluent::borrowck_dereference_suggestion, |
| "*".repeat(count), |
| Applicability::MachineApplicable, |
| ); |
| } |
| } |
| |
| #[allow(rustc::diagnostic_outside_of_impl)] |
| fn suggest_move_on_borrowing_closure(&self, diag: &mut Diag<'_>) { |
| let body = self.infcx.tcx.hir_body_owned_by(self.mir_def_id()); |
| let expr = &body.value.peel_blocks(); |
| let mut closure_span = None::<rustc_span::Span>; |
| match expr.kind { |
| hir::ExprKind::MethodCall(.., args, _) => { |
| for arg in args { |
| if let hir::ExprKind::Closure(hir::Closure { |
| capture_clause: hir::CaptureBy::Ref, |
| .. |
| }) = arg.kind |
| { |
| closure_span = Some(arg.span.shrink_to_lo()); |
| break; |
| } |
| } |
| } |
| hir::ExprKind::Closure(hir::Closure { |
| capture_clause: hir::CaptureBy::Ref, |
| kind, |
| .. |
| }) => { |
| if !matches!( |
| kind, |
| hir::ClosureKind::Coroutine(hir::CoroutineKind::Desugared( |
| hir::CoroutineDesugaring::Async, |
| _ |
| ),) |
| ) { |
| closure_span = Some(expr.span.shrink_to_lo()); |
| } |
| } |
| _ => {} |
| } |
| if let Some(closure_span) = closure_span { |
| diag.span_suggestion_verbose( |
| closure_span, |
| fluent::borrowck_move_closure_suggestion, |
| "move ", |
| Applicability::MaybeIncorrect, |
| ); |
| } |
| } |
| } |
