| use super::{ |
| ConstEvalFailure, |
| EvaluationResult, |
| FulfillmentError, |
| FulfillmentErrorCode, |
| MismatchedProjectionTypes, |
| ObjectSafetyViolation, |
| Obligation, |
| ObligationCause, |
| ObligationCauseCode, |
| OnUnimplementedDirective, |
| OnUnimplementedNote, |
| OutputTypeParameterMismatch, |
| Overflow, |
| PredicateObligation, |
| SelectionContext, |
| SelectionError, |
| TraitNotObjectSafe, |
| }; |
| |
| use crate::hir; |
| use crate::hir::Node; |
| use crate::hir::def_id::DefId; |
| use crate::infer::{self, InferCtxt}; |
| use crate::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind}; |
| use crate::session::DiagnosticMessageId; |
| use crate::ty::{self, AdtKind, DefIdTree, ToPredicate, ToPolyTraitRef, Ty, TyCtxt, TypeFoldable}; |
| use crate::ty::GenericParamDefKind; |
| use crate::ty::error::ExpectedFound; |
| use crate::ty::fast_reject; |
| use crate::ty::fold::TypeFolder; |
| use crate::ty::subst::Subst; |
| use crate::ty::SubtypePredicate; |
| use crate::util::nodemap::{FxHashMap, FxHashSet}; |
| |
| use errors::{Applicability, DiagnosticBuilder, pluralize, Style}; |
| use std::fmt; |
| use syntax::ast; |
| use syntax::symbol::{sym, kw}; |
| use syntax_pos::{DUMMY_SP, Span, ExpnKind, MultiSpan}; |
| use rustc::hir::def_id::LOCAL_CRATE; |
| use syntax_pos::source_map::SourceMap; |
| |
| use rustc_error_codes::*; |
| |
| impl<'a, 'tcx> InferCtxt<'a, 'tcx> { |
| pub fn report_fulfillment_errors( |
| &self, |
| errors: &[FulfillmentError<'tcx>], |
| body_id: Option<hir::BodyId>, |
| fallback_has_occurred: bool, |
| ) { |
| #[derive(Debug)] |
| struct ErrorDescriptor<'tcx> { |
| predicate: ty::Predicate<'tcx>, |
| index: Option<usize>, // None if this is an old error |
| } |
| |
| let mut error_map: FxHashMap<_, Vec<_>> = |
| self.reported_trait_errors.borrow().iter().map(|(&span, predicates)| { |
| (span, predicates.iter().map(|predicate| ErrorDescriptor { |
| predicate: predicate.clone(), |
| index: None |
| }).collect()) |
| }).collect(); |
| |
| for (index, error) in errors.iter().enumerate() { |
| // We want to ignore desugarings here: spans are equivalent even |
| // if one is the result of a desugaring and the other is not. |
| let mut span = error.obligation.cause.span; |
| let expn_data = span.ctxt().outer_expn_data(); |
| if let ExpnKind::Desugaring(_) = expn_data.kind { |
| span = expn_data.call_site; |
| } |
| |
| error_map.entry(span).or_default().push( |
| ErrorDescriptor { |
| predicate: error.obligation.predicate.clone(), |
| index: Some(index) |
| } |
| ); |
| |
| self.reported_trait_errors.borrow_mut() |
| .entry(span).or_default() |
| .push(error.obligation.predicate.clone()); |
| } |
| |
| // We do this in 2 passes because we want to display errors in order, though |
| // maybe it *is* better to sort errors by span or something. |
| let mut is_suppressed = vec![false; errors.len()]; |
| for (_, error_set) in error_map.iter() { |
| // We want to suppress "duplicate" errors with the same span. |
| for error in error_set { |
| if let Some(index) = error.index { |
| // Suppress errors that are either: |
| // 1) strictly implied by another error. |
| // 2) implied by an error with a smaller index. |
| for error2 in error_set { |
| if error2.index.map_or(false, |index2| is_suppressed[index2]) { |
| // Avoid errors being suppressed by already-suppressed |
| // errors, to prevent all errors from being suppressed |
| // at once. |
| continue |
| } |
| |
| if self.error_implies(&error2.predicate, &error.predicate) && |
| !(error2.index >= error.index && |
| self.error_implies(&error.predicate, &error2.predicate)) |
| { |
| info!("skipping {:?} (implied by {:?})", error, error2); |
| is_suppressed[index] = true; |
| break |
| } |
| } |
| } |
| } |
| } |
| |
| for (error, suppressed) in errors.iter().zip(is_suppressed) { |
| if !suppressed { |
| self.report_fulfillment_error(error, body_id, fallback_has_occurred); |
| } |
| } |
| } |
| |
| // returns if `cond` not occurring implies that `error` does not occur - i.e., that |
| // `error` occurring implies that `cond` occurs. |
| fn error_implies( |
| &self, |
| cond: &ty::Predicate<'tcx>, |
| error: &ty::Predicate<'tcx>, |
| ) -> bool { |
| if cond == error { |
| return true |
| } |
| |
| let (cond, error) = match (cond, error) { |
| (&ty::Predicate::Trait(..), &ty::Predicate::Trait(ref error)) |
| => (cond, error), |
| _ => { |
| // FIXME: make this work in other cases too. |
| return false |
| } |
| }; |
| |
| for implication in super::elaborate_predicates(self.tcx, vec![cond.clone()]) { |
| if let ty::Predicate::Trait(implication) = implication { |
| let error = error.to_poly_trait_ref(); |
| let implication = implication.to_poly_trait_ref(); |
| // FIXME: I'm just not taking associated types at all here. |
| // Eventually I'll need to implement param-env-aware |
| // `Γ₁ ⊦ φ₁ => Γ₂ ⊦ φ₂` logic. |
| let param_env = ty::ParamEnv::empty(); |
| if self.can_sub(param_env, error, implication).is_ok() { |
| debug!("error_implies: {:?} -> {:?} -> {:?}", cond, error, implication); |
| return true |
| } |
| } |
| } |
| |
| false |
| } |
| |
| fn report_fulfillment_error( |
| &self, |
| error: &FulfillmentError<'tcx>, |
| body_id: Option<hir::BodyId>, |
| fallback_has_occurred: bool, |
| ) { |
| debug!("report_fulfillment_error({:?})", error); |
| match error.code { |
| FulfillmentErrorCode::CodeSelectionError(ref selection_error) => { |
| self.report_selection_error( |
| &error.obligation, |
| selection_error, |
| fallback_has_occurred, |
| error.points_at_arg_span, |
| ); |
| } |
| FulfillmentErrorCode::CodeProjectionError(ref e) => { |
| self.report_projection_error(&error.obligation, e); |
| } |
| FulfillmentErrorCode::CodeAmbiguity => { |
| self.maybe_report_ambiguity(&error.obligation, body_id); |
| } |
| FulfillmentErrorCode::CodeSubtypeError(ref expected_found, ref err) => { |
| self.report_mismatched_types( |
| &error.obligation.cause, |
| expected_found.expected, |
| expected_found.found, |
| err.clone(), |
| ).emit(); |
| } |
| } |
| } |
| |
| fn report_projection_error( |
| &self, |
| obligation: &PredicateObligation<'tcx>, |
| error: &MismatchedProjectionTypes<'tcx>, |
| ) { |
| let predicate = self.resolve_vars_if_possible(&obligation.predicate); |
| |
| if predicate.references_error() { |
| return |
| } |
| |
| self.probe(|_| { |
| let err_buf; |
| let mut err = &error.err; |
| let mut values = None; |
| |
| // try to find the mismatched types to report the error with. |
| // |
| // this can fail if the problem was higher-ranked, in which |
| // cause I have no idea for a good error message. |
| if let ty::Predicate::Projection(ref data) = predicate { |
| let mut selcx = SelectionContext::new(self); |
| let (data, _) = self.replace_bound_vars_with_fresh_vars( |
| obligation.cause.span, |
| infer::LateBoundRegionConversionTime::HigherRankedType, |
| data |
| ); |
| let mut obligations = vec![]; |
| let normalized_ty = super::normalize_projection_type( |
| &mut selcx, |
| obligation.param_env, |
| data.projection_ty, |
| obligation.cause.clone(), |
| 0, |
| &mut obligations |
| ); |
| |
| debug!("report_projection_error obligation.cause={:?} obligation.param_env={:?}", |
| obligation.cause, obligation.param_env); |
| |
| debug!("report_projection_error normalized_ty={:?} data.ty={:?}", |
| normalized_ty, data.ty); |
| |
| let is_normalized_ty_expected = match &obligation.cause.code { |
| ObligationCauseCode::ItemObligation(_) | |
| ObligationCauseCode::BindingObligation(_, _) | |
| ObligationCauseCode::ObjectCastObligation(_) => false, |
| _ => true, |
| }; |
| |
| if let Err(error) = self.at(&obligation.cause, obligation.param_env) |
| .eq_exp(is_normalized_ty_expected, normalized_ty, data.ty) |
| { |
| values = Some(infer::ValuePairs::Types( |
| ExpectedFound::new(is_normalized_ty_expected, normalized_ty, data.ty))); |
| |
| err_buf = error; |
| err = &err_buf; |
| } |
| } |
| |
| let msg = format!("type mismatch resolving `{}`", predicate); |
| let error_id = ( |
| DiagnosticMessageId::ErrorId(271), |
| Some(obligation.cause.span), |
| msg, |
| ); |
| let fresh = self.tcx.sess.one_time_diagnostics.borrow_mut().insert(error_id); |
| if fresh { |
| let mut diag = struct_span_err!( |
| self.tcx.sess, |
| obligation.cause.span, |
| E0271, |
| "type mismatch resolving `{}`", |
| predicate |
| ); |
| self.note_type_err(&mut diag, &obligation.cause, None, values, err); |
| self.note_obligation_cause(&mut diag, obligation); |
| diag.emit(); |
| } |
| }); |
| } |
| |
| fn fuzzy_match_tys(&self, a: Ty<'tcx>, b: Ty<'tcx>) -> bool { |
| /// returns the fuzzy category of a given type, or None |
| /// if the type can be equated to any type. |
| fn type_category(t: Ty<'_>) -> Option<u32> { |
| match t.kind { |
| ty::Bool => Some(0), |
| ty::Char => Some(1), |
| ty::Str => Some(2), |
| ty::Int(..) | ty::Uint(..) | ty::Infer(ty::IntVar(..)) => Some(3), |
| ty::Float(..) | ty::Infer(ty::FloatVar(..)) => Some(4), |
| ty::Ref(..) | ty::RawPtr(..) => Some(5), |
| ty::Array(..) | ty::Slice(..) => Some(6), |
| ty::FnDef(..) | ty::FnPtr(..) => Some(7), |
| ty::Dynamic(..) => Some(8), |
| ty::Closure(..) => Some(9), |
| ty::Tuple(..) => Some(10), |
| ty::Projection(..) => Some(11), |
| ty::Param(..) => Some(12), |
| ty::Opaque(..) => Some(13), |
| ty::Never => Some(14), |
| ty::Adt(adt, ..) => match adt.adt_kind() { |
| AdtKind::Struct => Some(15), |
| AdtKind::Union => Some(16), |
| AdtKind::Enum => Some(17), |
| }, |
| ty::Generator(..) => Some(18), |
| ty::Foreign(..) => Some(19), |
| ty::GeneratorWitness(..) => Some(20), |
| ty::Placeholder(..) | ty::Bound(..) | ty::Infer(..) | ty::Error => None, |
| ty::UnnormalizedProjection(..) => bug!("only used with chalk-engine"), |
| } |
| } |
| |
| match (type_category(a), type_category(b)) { |
| (Some(cat_a), Some(cat_b)) => match (&a.kind, &b.kind) { |
| (&ty::Adt(def_a, _), &ty::Adt(def_b, _)) => def_a == def_b, |
| _ => cat_a == cat_b |
| }, |
| // infer and error can be equated to all types |
| _ => true |
| } |
| } |
| |
| fn impl_similar_to(&self, |
| trait_ref: ty::PolyTraitRef<'tcx>, |
| obligation: &PredicateObligation<'tcx>) |
| -> Option<DefId> |
| { |
| let tcx = self.tcx; |
| let param_env = obligation.param_env; |
| let trait_ref = tcx.erase_late_bound_regions(&trait_ref); |
| let trait_self_ty = trait_ref.self_ty(); |
| |
| let mut self_match_impls = vec![]; |
| let mut fuzzy_match_impls = vec![]; |
| |
| self.tcx.for_each_relevant_impl( |
| trait_ref.def_id, trait_self_ty, |def_id| { |
| let impl_substs = self.fresh_substs_for_item(obligation.cause.span, def_id); |
| let impl_trait_ref = tcx |
| .impl_trait_ref(def_id) |
| .unwrap() |
| .subst(tcx, impl_substs); |
| |
| let impl_self_ty = impl_trait_ref.self_ty(); |
| |
| if let Ok(..) = self.can_eq(param_env, trait_self_ty, impl_self_ty) { |
| self_match_impls.push(def_id); |
| |
| if trait_ref.substs.types().skip(1) |
| .zip(impl_trait_ref.substs.types().skip(1)) |
| .all(|(u,v)| self.fuzzy_match_tys(u, v)) |
| { |
| fuzzy_match_impls.push(def_id); |
| } |
| } |
| }); |
| |
| let impl_def_id = if self_match_impls.len() == 1 { |
| self_match_impls[0] |
| } else if fuzzy_match_impls.len() == 1 { |
| fuzzy_match_impls[0] |
| } else { |
| return None |
| }; |
| |
| tcx.has_attr(impl_def_id, sym::rustc_on_unimplemented).then_some(impl_def_id) |
| } |
| |
| fn describe_generator(&self, body_id: hir::BodyId) -> Option<&'static str> { |
| self.tcx.hir().body(body_id).generator_kind.map(|gen_kind| { |
| match gen_kind { |
| hir::GeneratorKind::Gen => "a generator", |
| hir::GeneratorKind::Async(hir::AsyncGeneratorKind::Block) => "an async block", |
| hir::GeneratorKind::Async(hir::AsyncGeneratorKind::Fn) => "an async function", |
| hir::GeneratorKind::Async(hir::AsyncGeneratorKind::Closure) => "an async closure", |
| } |
| }) |
| } |
| |
| /// Used to set on_unimplemented's `ItemContext` |
| /// to be the enclosing (async) block/function/closure |
| fn describe_enclosure(&self, hir_id: hir::HirId) -> Option<&'static str> { |
| let hir = &self.tcx.hir(); |
| let node = hir.find(hir_id)?; |
| if let hir::Node::Item( |
| hir::Item{kind: hir::ItemKind::Fn(sig, _, body_id), .. }) = &node { |
| self.describe_generator(*body_id).or_else(|| |
| Some(if let hir::FnHeader{ asyncness: hir::IsAsync::Async, .. } = sig.header { |
| "an async function" |
| } else { |
| "a function" |
| }) |
| ) |
| } else if let hir::Node::Expr(hir::Expr { |
| kind: hir::ExprKind::Closure(_is_move, _, body_id, _, gen_movability), .. }) = &node { |
| self.describe_generator(*body_id).or_else(|| |
| Some(if gen_movability.is_some() { |
| "an async closure" |
| } else { |
| "a closure" |
| }) |
| ) |
| } else if let hir::Node::Expr(hir::Expr { .. }) = &node { |
| let parent_hid = hir.get_parent_node(hir_id); |
| if parent_hid != hir_id { |
| return self.describe_enclosure(parent_hid); |
| } else { |
| None |
| } |
| } else { |
| None |
| } |
| } |
| |
| fn on_unimplemented_note( |
| &self, |
| trait_ref: ty::PolyTraitRef<'tcx>, |
| obligation: &PredicateObligation<'tcx>, |
| ) -> OnUnimplementedNote { |
| let def_id = self.impl_similar_to(trait_ref, obligation) |
| .unwrap_or_else(|| trait_ref.def_id()); |
| let trait_ref = *trait_ref.skip_binder(); |
| |
| let mut flags = vec![]; |
| flags.push((sym::item_context, |
| self.describe_enclosure(obligation.cause.body_id).map(|s|s.to_owned()))); |
| |
| match obligation.cause.code { |
| ObligationCauseCode::BuiltinDerivedObligation(..) | |
| ObligationCauseCode::ImplDerivedObligation(..) => {} |
| _ => { |
| // this is a "direct", user-specified, rather than derived, |
| // obligation. |
| flags.push((sym::direct, None)); |
| } |
| } |
| |
| if let ObligationCauseCode::ItemObligation(item) = obligation.cause.code { |
| // FIXME: maybe also have some way of handling methods |
| // from other traits? That would require name resolution, |
| // which we might want to be some sort of hygienic. |
| // |
| // Currently I'm leaving it for what I need for `try`. |
| if self.tcx.trait_of_item(item) == Some(trait_ref.def_id) { |
| let method = self.tcx.item_name(item); |
| flags.push((sym::from_method, None)); |
| flags.push((sym::from_method, Some(method.to_string()))); |
| } |
| } |
| if let Some(t) = self.get_parent_trait_ref(&obligation.cause.code) { |
| flags.push((sym::parent_trait, Some(t))); |
| } |
| |
| if let Some(k) = obligation.cause.span.desugaring_kind() { |
| flags.push((sym::from_desugaring, None)); |
| flags.push((sym::from_desugaring, Some(format!("{:?}", k)))); |
| } |
| let generics = self.tcx.generics_of(def_id); |
| let self_ty = trait_ref.self_ty(); |
| // This is also included through the generics list as `Self`, |
| // but the parser won't allow you to use it |
| flags.push((sym::_Self, Some(self_ty.to_string()))); |
| if let Some(def) = self_ty.ty_adt_def() { |
| // We also want to be able to select self's original |
| // signature with no type arguments resolved |
| flags.push((sym::_Self, Some(self.tcx.type_of(def.did).to_string()))); |
| } |
| |
| for param in generics.params.iter() { |
| let value = match param.kind { |
| GenericParamDefKind::Type { .. } | |
| GenericParamDefKind::Const => { |
| trait_ref.substs[param.index as usize].to_string() |
| }, |
| GenericParamDefKind::Lifetime => continue, |
| }; |
| let name = param.name; |
| flags.push((name, Some(value))); |
| } |
| |
| if let Some(true) = self_ty.ty_adt_def().map(|def| def.did.is_local()) { |
| flags.push((sym::crate_local, None)); |
| } |
| |
| // Allow targeting all integers using `{integral}`, even if the exact type was resolved |
| if self_ty.is_integral() { |
| flags.push((sym::_Self, Some("{integral}".to_owned()))); |
| } |
| |
| if let ty::Array(aty, len) = self_ty.kind { |
| flags.push((sym::_Self, Some("[]".to_owned()))); |
| flags.push((sym::_Self, Some(format!("[{}]", aty)))); |
| if let Some(def) = aty.ty_adt_def() { |
| // We also want to be able to select the array's type's original |
| // signature with no type arguments resolved |
| flags.push(( |
| sym::_Self, |
| Some(format!("[{}]", self.tcx.type_of(def.did).to_string())), |
| )); |
| let tcx = self.tcx; |
| if let Some(len) = len.try_eval_usize(tcx, ty::ParamEnv::empty()) { |
| flags.push(( |
| sym::_Self, |
| Some(format!("[{}; {}]", self.tcx.type_of(def.did).to_string(), len)), |
| )); |
| } else { |
| flags.push(( |
| sym::_Self, |
| Some(format!("[{}; _]", self.tcx.type_of(def.did).to_string())), |
| )); |
| } |
| } |
| } |
| |
| if let Ok(Some(command)) = OnUnimplementedDirective::of_item( |
| self.tcx, trait_ref.def_id, def_id |
| ) { |
| command.evaluate(self.tcx, trait_ref, &flags[..]) |
| } else { |
| OnUnimplementedNote::default() |
| } |
| } |
| |
| fn find_similar_impl_candidates( |
| &self, |
| trait_ref: ty::PolyTraitRef<'tcx>, |
| ) -> Vec<ty::TraitRef<'tcx>> { |
| let simp = fast_reject::simplify_type(self.tcx, trait_ref.skip_binder().self_ty(), true); |
| let all_impls = self.tcx.all_impls(trait_ref.def_id()); |
| |
| match simp { |
| Some(simp) => all_impls.iter().filter_map(|&def_id| { |
| let imp = self.tcx.impl_trait_ref(def_id).unwrap(); |
| let imp_simp = fast_reject::simplify_type(self.tcx, imp.self_ty(), true); |
| if let Some(imp_simp) = imp_simp { |
| if simp != imp_simp { |
| return None |
| } |
| } |
| |
| Some(imp) |
| }).collect(), |
| None => all_impls.iter().map(|&def_id| |
| self.tcx.impl_trait_ref(def_id).unwrap() |
| ).collect() |
| } |
| } |
| |
| fn report_similar_impl_candidates( |
| &self, |
| impl_candidates: Vec<ty::TraitRef<'tcx>>, |
| err: &mut DiagnosticBuilder<'_>, |
| ) { |
| if impl_candidates.is_empty() { |
| return; |
| } |
| |
| let len = impl_candidates.len(); |
| let end = if impl_candidates.len() <= 5 { |
| impl_candidates.len() |
| } else { |
| 4 |
| }; |
| |
| let normalize = |candidate| self.tcx.infer_ctxt().enter(|ref infcx| { |
| let normalized = infcx |
| .at(&ObligationCause::dummy(), ty::ParamEnv::empty()) |
| .normalize(candidate) |
| .ok(); |
| match normalized { |
| Some(normalized) => format!("\n {:?}", normalized.value), |
| None => format!("\n {:?}", candidate), |
| } |
| }); |
| |
| // Sort impl candidates so that ordering is consistent for UI tests. |
| let mut normalized_impl_candidates = impl_candidates |
| .iter() |
| .map(normalize) |
| .collect::<Vec<String>>(); |
| |
| // Sort before taking the `..end` range, |
| // because the ordering of `impl_candidates` may not be deterministic: |
| // https://github.com/rust-lang/rust/pull/57475#issuecomment-455519507 |
| normalized_impl_candidates.sort(); |
| |
| err.help(&format!("the following implementations were found:{}{}", |
| normalized_impl_candidates[..end].join(""), |
| if len > 5 { |
| format!("\nand {} others", len - 4) |
| } else { |
| String::new() |
| } |
| )); |
| } |
| |
| /// Reports that an overflow has occurred and halts compilation. We |
| /// halt compilation unconditionally because it is important that |
| /// overflows never be masked -- they basically represent computations |
| /// whose result could not be truly determined and thus we can't say |
| /// if the program type checks or not -- and they are unusual |
| /// occurrences in any case. |
| pub fn report_overflow_error<T>( |
| &self, |
| obligation: &Obligation<'tcx, T>, |
| suggest_increasing_limit: bool, |
| ) -> ! |
| where T: fmt::Display + TypeFoldable<'tcx> |
| { |
| let predicate = |
| self.resolve_vars_if_possible(&obligation.predicate); |
| let mut err = struct_span_err!( |
| self.tcx.sess, |
| obligation.cause.span, |
| E0275, |
| "overflow evaluating the requirement `{}`", |
| predicate |
| ); |
| |
| if suggest_increasing_limit { |
| self.suggest_new_overflow_limit(&mut err); |
| } |
| |
| self.note_obligation_cause_code( |
| &mut err, |
| &obligation.predicate, |
| &obligation.cause.code, |
| &mut vec![], |
| ); |
| |
| err.emit(); |
| self.tcx.sess.abort_if_errors(); |
| bug!(); |
| } |
| |
| /// Reports that a cycle was detected which led to overflow and halts |
| /// compilation. This is equivalent to `report_overflow_error` except |
| /// that we can give a more helpful error message (and, in particular, |
| /// we do not suggest increasing the overflow limit, which is not |
| /// going to help). |
| pub fn report_overflow_error_cycle(&self, cycle: &[PredicateObligation<'tcx>]) -> ! { |
| let cycle = self.resolve_vars_if_possible(&cycle.to_owned()); |
| assert!(cycle.len() > 0); |
| |
| debug!("report_overflow_error_cycle: cycle={:?}", cycle); |
| |
| self.report_overflow_error(&cycle[0], false); |
| } |
| |
| pub fn report_extra_impl_obligation(&self, |
| error_span: Span, |
| item_name: ast::Name, |
| _impl_item_def_id: DefId, |
| trait_item_def_id: DefId, |
| requirement: &dyn fmt::Display) |
| -> DiagnosticBuilder<'tcx> |
| { |
| let msg = "impl has stricter requirements than trait"; |
| let sp = self.tcx.sess.source_map().def_span(error_span); |
| |
| let mut err = struct_span_err!(self.tcx.sess, sp, E0276, "{}", msg); |
| |
| if let Some(trait_item_span) = self.tcx.hir().span_if_local(trait_item_def_id) { |
| let span = self.tcx.sess.source_map().def_span(trait_item_span); |
| err.span_label(span, format!("definition of `{}` from trait", item_name)); |
| } |
| |
| err.span_label(sp, format!("impl has extra requirement {}", requirement)); |
| |
| err |
| } |
| |
| |
| /// Gets the parent trait chain start |
| fn get_parent_trait_ref(&self, code: &ObligationCauseCode<'tcx>) -> Option<String> { |
| match code { |
| &ObligationCauseCode::BuiltinDerivedObligation(ref data) => { |
| let parent_trait_ref = self.resolve_vars_if_possible( |
| &data.parent_trait_ref); |
| match self.get_parent_trait_ref(&data.parent_code) { |
| Some(t) => Some(t), |
| None => Some(parent_trait_ref.skip_binder().self_ty().to_string()), |
| } |
| } |
| _ => None, |
| } |
| } |
| |
| pub fn report_selection_error( |
| &self, |
| obligation: &PredicateObligation<'tcx>, |
| error: &SelectionError<'tcx>, |
| fallback_has_occurred: bool, |
| points_at_arg: bool, |
| ) { |
| let tcx = self.tcx; |
| let span = obligation.cause.span; |
| |
| let mut err = match *error { |
| SelectionError::Unimplemented => { |
| if let ObligationCauseCode::CompareImplMethodObligation { |
| item_name, impl_item_def_id, trait_item_def_id, |
| } = obligation.cause.code { |
| self.report_extra_impl_obligation( |
| span, |
| item_name, |
| impl_item_def_id, |
| trait_item_def_id, |
| &format!("`{}`", obligation.predicate)) |
| .emit(); |
| return; |
| } |
| match obligation.predicate { |
| ty::Predicate::Trait(ref trait_predicate) => { |
| let trait_predicate = self.resolve_vars_if_possible(trait_predicate); |
| |
| if self.tcx.sess.has_errors() && trait_predicate.references_error() { |
| return; |
| } |
| let trait_ref = trait_predicate.to_poly_trait_ref(); |
| let ( |
| post_message, |
| pre_message, |
| ) = self.get_parent_trait_ref(&obligation.cause.code) |
| .map(|t| (format!(" in `{}`", t), format!("within `{}`, ", t))) |
| .unwrap_or_default(); |
| |
| let OnUnimplementedNote { |
| message, |
| label, |
| note, |
| enclosing_scope, |
| } = self.on_unimplemented_note(trait_ref, obligation); |
| let have_alt_message = message.is_some() || label.is_some(); |
| let is_try = self.tcx.sess.source_map().span_to_snippet(span) |
| .map(|s| &s == "?") |
| .unwrap_or(false); |
| let is_from = |
| format!("{}", trait_ref.print_only_trait_path()) |
| .starts_with("std::convert::From<"); |
| let (message, note) = if is_try && is_from { |
| (Some(format!( |
| "`?` couldn't convert the error to `{}`", |
| trait_ref.self_ty(), |
| )), Some( |
| "the question mark operation (`?`) implicitly performs a \ |
| conversion on the error value using the `From` trait".to_owned() |
| )) |
| } else { |
| (message, note) |
| }; |
| |
| let mut err = struct_span_err!( |
| self.tcx.sess, |
| span, |
| E0277, |
| "{}", |
| message.unwrap_or_else(|| format!( |
| "the trait bound `{}` is not satisfied{}", |
| trait_ref.to_predicate(), |
| post_message, |
| ))); |
| |
| let explanation = |
| if obligation.cause.code == ObligationCauseCode::MainFunctionType { |
| "consider using `()`, or a `Result`".to_owned() |
| } else { |
| format!( |
| "{}the trait `{}` is not implemented for `{}`", |
| pre_message, |
| trait_ref.print_only_trait_path(), |
| trait_ref.self_ty(), |
| ) |
| }; |
| |
| if self.suggest_add_reference_to_arg( |
| &obligation, |
| &mut err, |
| &trait_ref, |
| points_at_arg, |
| have_alt_message, |
| ) { |
| self.note_obligation_cause(&mut err, obligation); |
| err.emit(); |
| return; |
| } |
| if let Some(ref s) = label { |
| // If it has a custom `#[rustc_on_unimplemented]` |
| // error message, let's display it as the label! |
| err.span_label(span, s.as_str()); |
| err.help(&explanation); |
| } else { |
| err.span_label(span, explanation); |
| } |
| if let Some(ref s) = note { |
| // If it has a custom `#[rustc_on_unimplemented]` note, let's display it |
| err.note(s.as_str()); |
| } |
| if let Some(ref s) = enclosing_scope { |
| let enclosing_scope_span = tcx.def_span( |
| tcx.hir() |
| .opt_local_def_id(obligation.cause.body_id) |
| .unwrap_or_else(|| { |
| tcx.hir().body_owner_def_id(hir::BodyId { |
| hir_id: obligation.cause.body_id, |
| }) |
| }), |
| ); |
| |
| err.span_label(enclosing_scope_span, s.as_str()); |
| } |
| |
| self.suggest_borrow_on_unsized_slice(&obligation.cause.code, &mut err); |
| self.suggest_fn_call(&obligation, &mut err, &trait_ref, points_at_arg); |
| self.suggest_remove_reference(&obligation, &mut err, &trait_ref); |
| self.suggest_semicolon_removal(&obligation, &mut err, span, &trait_ref); |
| self.note_version_mismatch(&mut err, &trait_ref); |
| |
| // Try to report a help message |
| if !trait_ref.has_infer_types() && |
| self.predicate_can_apply(obligation.param_env, trait_ref) { |
| // If a where-clause may be useful, remind the |
| // user that they can add it. |
| // |
| // don't display an on-unimplemented note, as |
| // these notes will often be of the form |
| // "the type `T` can't be frobnicated" |
| // which is somewhat confusing. |
| self.suggest_restricting_param_bound( |
| &mut err, |
| &trait_ref, |
| obligation.cause.body_id, |
| ); |
| } else { |
| if !have_alt_message { |
| // Can't show anything else useful, try to find similar impls. |
| let impl_candidates = self.find_similar_impl_candidates(trait_ref); |
| self.report_similar_impl_candidates(impl_candidates, &mut err); |
| } |
| self.suggest_change_mut( |
| &obligation, |
| &mut err, |
| &trait_ref, |
| points_at_arg, |
| ); |
| } |
| |
| // If this error is due to `!: Trait` not implemented but `(): Trait` is |
| // implemented, and fallback has occurred, then it could be due to a |
| // variable that used to fallback to `()` now falling back to `!`. Issue a |
| // note informing about the change in behaviour. |
| if trait_predicate.skip_binder().self_ty().is_never() |
| && fallback_has_occurred |
| { |
| let predicate = trait_predicate.map_bound(|mut trait_pred| { |
| trait_pred.trait_ref.substs = self.tcx.mk_substs_trait( |
| self.tcx.mk_unit(), |
| &trait_pred.trait_ref.substs[1..], |
| ); |
| trait_pred |
| }); |
| let unit_obligation = Obligation { |
| predicate: ty::Predicate::Trait(predicate), |
| .. obligation.clone() |
| }; |
| if self.predicate_may_hold(&unit_obligation) { |
| err.note("the trait is implemented for `()`. \ |
| Possibly this error has been caused by changes to \ |
| Rust's type-inference algorithm \ |
| (see: https://github.com/rust-lang/rust/issues/48950 \ |
| for more info). Consider whether you meant to use the \ |
| type `()` here instead."); |
| } |
| } |
| |
| err |
| } |
| |
| ty::Predicate::Subtype(ref predicate) => { |
| // Errors for Subtype predicates show up as |
| // `FulfillmentErrorCode::CodeSubtypeError`, |
| // not selection error. |
| span_bug!(span, "subtype requirement gave wrong error: `{:?}`", predicate) |
| } |
| |
| ty::Predicate::RegionOutlives(ref predicate) => { |
| let predicate = self.resolve_vars_if_possible(predicate); |
| let err = self.region_outlives_predicate(&obligation.cause, |
| &predicate).err().unwrap(); |
| struct_span_err!( |
| self.tcx.sess, span, E0279, |
| "the requirement `{}` is not satisfied (`{}`)", |
| predicate, err, |
| ) |
| } |
| |
| ty::Predicate::Projection(..) | ty::Predicate::TypeOutlives(..) => { |
| let predicate = |
| self.resolve_vars_if_possible(&obligation.predicate); |
| struct_span_err!(self.tcx.sess, span, E0280, |
| "the requirement `{}` is not satisfied", |
| predicate) |
| } |
| |
| ty::Predicate::ObjectSafe(trait_def_id) => { |
| let violations = self.tcx.object_safety_violations(trait_def_id); |
| self.tcx.report_object_safety_error( |
| span, |
| trait_def_id, |
| violations, |
| ) |
| } |
| |
| ty::Predicate::ClosureKind(closure_def_id, closure_substs, kind) => { |
| let found_kind = self.closure_kind(closure_def_id, closure_substs).unwrap(); |
| let closure_span = self.tcx.sess.source_map() |
| .def_span(self.tcx.hir().span_if_local(closure_def_id).unwrap()); |
| let hir_id = self.tcx.hir().as_local_hir_id(closure_def_id).unwrap(); |
| let mut err = struct_span_err!( |
| self.tcx.sess, closure_span, E0525, |
| "expected a closure that implements the `{}` trait, \ |
| but this closure only implements `{}`", |
| kind, |
| found_kind); |
| |
| err.span_label( |
| closure_span, |
| format!("this closure implements `{}`, not `{}`", found_kind, kind)); |
| err.span_label( |
| obligation.cause.span, |
| format!("the requirement to implement `{}` derives from here", kind)); |
| |
| // Additional context information explaining why the closure only implements |
| // a particular trait. |
| if let Some(tables) = self.in_progress_tables { |
| let tables = tables.borrow(); |
| match (found_kind, tables.closure_kind_origins().get(hir_id)) { |
| (ty::ClosureKind::FnOnce, Some((span, name))) => { |
| err.span_label(*span, format!( |
| "closure is `FnOnce` because it moves the \ |
| variable `{}` out of its environment", name)); |
| }, |
| (ty::ClosureKind::FnMut, Some((span, name))) => { |
| err.span_label(*span, format!( |
| "closure is `FnMut` because it mutates the \ |
| variable `{}` here", name)); |
| }, |
| _ => {} |
| } |
| } |
| |
| err.emit(); |
| return; |
| } |
| |
| ty::Predicate::WellFormed(ty) => { |
| if !self.tcx.sess.opts.debugging_opts.chalk { |
| // WF predicates cannot themselves make |
| // errors. They can only block due to |
| // ambiguity; otherwise, they always |
| // degenerate into other obligations |
| // (which may fail). |
| span_bug!(span, "WF predicate not satisfied for {:?}", ty); |
| } else { |
| // FIXME: we'll need a better message which takes into account |
| // which bounds actually failed to hold. |
| self.tcx.sess.struct_span_err( |
| span, |
| &format!("the type `{}` is not well-formed (chalk)", ty) |
| ) |
| } |
| } |
| |
| ty::Predicate::ConstEvaluatable(..) => { |
| // Errors for `ConstEvaluatable` predicates show up as |
| // `SelectionError::ConstEvalFailure`, |
| // not `Unimplemented`. |
| span_bug!(span, |
| "const-evaluatable requirement gave wrong error: `{:?}`", obligation) |
| } |
| } |
| } |
| |
| OutputTypeParameterMismatch(ref found_trait_ref, ref expected_trait_ref, _) => { |
| let found_trait_ref = self.resolve_vars_if_possible(&*found_trait_ref); |
| let expected_trait_ref = self.resolve_vars_if_possible(&*expected_trait_ref); |
| |
| if expected_trait_ref.self_ty().references_error() { |
| return; |
| } |
| |
| let found_trait_ty = found_trait_ref.self_ty(); |
| |
| let found_did = match found_trait_ty.kind { |
| ty::Closure(did, _) | ty::Foreign(did) | ty::FnDef(did, _) => Some(did), |
| ty::Adt(def, _) => Some(def.did), |
| _ => None, |
| }; |
| |
| let found_span = found_did.and_then(|did| |
| self.tcx.hir().span_if_local(did) |
| ).map(|sp| self.tcx.sess.source_map().def_span(sp)); // the sp could be an fn def |
| |
| if self.reported_closure_mismatch.borrow().contains(&(span, found_span)) { |
| // We check closures twice, with obligations flowing in different directions, |
| // but we want to complain about them only once. |
| return; |
| } |
| |
| self.reported_closure_mismatch.borrow_mut().insert((span, found_span)); |
| |
| let found = match found_trait_ref.skip_binder().substs.type_at(1).kind { |
| ty::Tuple(ref tys) => vec![ArgKind::empty(); tys.len()], |
| _ => vec![ArgKind::empty()], |
| }; |
| |
| let expected_ty = expected_trait_ref.skip_binder().substs.type_at(1); |
| let expected = match expected_ty.kind { |
| ty::Tuple(ref tys) => tys.iter() |
| .map(|t| ArgKind::from_expected_ty(t.expect_ty(), Some(span))).collect(), |
| _ => vec![ArgKind::Arg("_".to_owned(), expected_ty.to_string())], |
| }; |
| |
| if found.len() == expected.len() { |
| self.report_closure_arg_mismatch(span, |
| found_span, |
| found_trait_ref, |
| expected_trait_ref) |
| } else { |
| let (closure_span, found) = found_did |
| .and_then(|did| self.tcx.hir().get_if_local(did)) |
| .map(|node| { |
| let (found_span, found) = self.get_fn_like_arguments(node); |
| (Some(found_span), found) |
| }).unwrap_or((found_span, found)); |
| |
| self.report_arg_count_mismatch(span, |
| closure_span, |
| expected, |
| found, |
| found_trait_ty.is_closure()) |
| } |
| } |
| |
| TraitNotObjectSafe(did) => { |
| let violations = self.tcx.object_safety_violations(did); |
| self.tcx.report_object_safety_error(span, did, violations) |
| } |
| |
| // already reported in the query |
| ConstEvalFailure(err) => { |
| self.tcx.sess.delay_span_bug( |
| span, |
| &format!("constant in type had an ignored error: {:?}", err), |
| ); |
| return; |
| } |
| |
| Overflow => { |
| bug!("overflow should be handled before the `report_selection_error` path"); |
| } |
| }; |
| |
| self.note_obligation_cause(&mut err, obligation); |
| |
| err.emit(); |
| } |
| |
| /// If the `Self` type of the unsatisfied trait `trait_ref` implements a trait |
| /// with the same path as `trait_ref`, a help message about |
| /// a probable version mismatch is added to `err` |
| fn note_version_mismatch( |
| &self, |
| err: &mut DiagnosticBuilder<'_>, |
| trait_ref: &ty::PolyTraitRef<'tcx>, |
| ) { |
| let get_trait_impl = |trait_def_id| { |
| let mut trait_impl = None; |
| self.tcx.for_each_relevant_impl(trait_def_id, trait_ref.self_ty(), |impl_def_id| { |
| if trait_impl.is_none() { |
| trait_impl = Some(impl_def_id); |
| } |
| }); |
| trait_impl |
| }; |
| let required_trait_path = self.tcx.def_path_str(trait_ref.def_id()); |
| let all_traits = self.tcx.all_traits(LOCAL_CRATE); |
| let traits_with_same_path: std::collections::BTreeSet<_> = all_traits |
| .iter() |
| .filter(|trait_def_id| **trait_def_id != trait_ref.def_id()) |
| .filter(|trait_def_id| self.tcx.def_path_str(**trait_def_id) == required_trait_path) |
| .collect(); |
| for trait_with_same_path in traits_with_same_path { |
| if let Some(impl_def_id) = get_trait_impl(*trait_with_same_path) { |
| let impl_span = self.tcx.def_span(impl_def_id); |
| err.span_help(impl_span, "trait impl with same name found"); |
| let trait_crate = self.tcx.crate_name(trait_with_same_path.krate); |
| let crate_msg = format!( |
| "Perhaps two different versions of crate `{}` are being used?", |
| trait_crate |
| ); |
| err.note(&crate_msg); |
| } |
| } |
| } |
| fn suggest_restricting_param_bound( |
| &self, |
| mut err: &mut DiagnosticBuilder<'_>, |
| trait_ref: &ty::PolyTraitRef<'_>, |
| body_id: hir::HirId, |
| ) { |
| let self_ty = trait_ref.self_ty(); |
| let (param_ty, projection) = match &self_ty.kind { |
| ty::Param(_) => (true, None), |
| ty::Projection(projection) => (false, Some(projection)), |
| _ => return, |
| }; |
| |
| let suggest_restriction = | |
| generics: &hir::Generics, |
| msg, |
| err: &mut DiagnosticBuilder<'_>, |
| | { |
| let span = generics.where_clause.span_for_predicates_or_empty_place(); |
| if !span.from_expansion() && span.desugaring_kind().is_none() { |
| err.span_suggestion( |
| generics.where_clause.span_for_predicates_or_empty_place().shrink_to_hi(), |
| &format!("consider further restricting {}", msg), |
| format!( |
| "{} {} ", |
| if !generics.where_clause.predicates.is_empty() { |
| "," |
| } else { |
| " where" |
| }, |
| trait_ref.to_predicate(), |
| ), |
| Applicability::MachineApplicable, |
| ); |
| } |
| }; |
| |
| // FIXME: Add check for trait bound that is already present, particularly `?Sized` so we |
| // don't suggest `T: Sized + ?Sized`. |
| let mut hir_id = body_id; |
| while let Some(node) = self.tcx.hir().find(hir_id) { |
| match node { |
| hir::Node::TraitItem(hir::TraitItem { |
| generics, |
| kind: hir::TraitItemKind::Method(..), .. |
| }) if param_ty && self_ty == self.tcx.types.self_param => { |
| // Restricting `Self` for a single method. |
| suggest_restriction(&generics, "`Self`", err); |
| return; |
| } |
| |
| hir::Node::Item(hir::Item { |
| kind: hir::ItemKind::Fn(_, generics, _), .. |
| }) | |
| hir::Node::TraitItem(hir::TraitItem { |
| generics, |
| kind: hir::TraitItemKind::Method(..), .. |
| }) | |
| hir::Node::ImplItem(hir::ImplItem { |
| generics, |
| kind: hir::ImplItemKind::Method(..), .. |
| }) | |
| hir::Node::Item(hir::Item { |
| kind: hir::ItemKind::Trait(_, _, generics, _, _), .. |
| }) | |
| hir::Node::Item(hir::Item { |
| kind: hir::ItemKind::Impl(_, _, _, generics, ..), .. |
| }) if projection.is_some() => { |
| // Missing associated type bound. |
| suggest_restriction(&generics, "the associated type", err); |
| return; |
| } |
| |
| hir::Node::Item(hir::Item { kind: hir::ItemKind::Struct(_, generics), span, .. }) | |
| hir::Node::Item(hir::Item { kind: hir::ItemKind::Enum(_, generics), span, .. }) | |
| hir::Node::Item(hir::Item { kind: hir::ItemKind::Union(_, generics), span, .. }) | |
| hir::Node::Item(hir::Item { |
| kind: hir::ItemKind::Trait(_, _, generics, ..), span, .. |
| }) | |
| hir::Node::Item(hir::Item { |
| kind: hir::ItemKind::Impl(_, _, _, generics, ..), span, .. |
| }) | |
| hir::Node::Item(hir::Item { |
| kind: hir::ItemKind::Fn(_, generics, _), span, .. |
| }) | |
| hir::Node::Item(hir::Item { |
| kind: hir::ItemKind::TyAlias(_, generics), span, .. |
| }) | |
| hir::Node::Item(hir::Item { |
| kind: hir::ItemKind::TraitAlias(generics, _), span, .. |
| }) | |
| hir::Node::Item(hir::Item { |
| kind: hir::ItemKind::OpaqueTy(hir::OpaqueTy { generics, .. }), span, .. |
| }) | |
| hir::Node::TraitItem(hir::TraitItem { generics, span, .. }) | |
| hir::Node::ImplItem(hir::ImplItem { generics, span, .. }) |
| if param_ty => { |
| // Missing generic type parameter bound. |
| let param_name = self_ty.to_string(); |
| let constraint = trait_ref.print_only_trait_path().to_string(); |
| if suggest_constraining_type_param( |
| generics, |
| &mut err, |
| ¶m_name, |
| &constraint, |
| self.tcx.sess.source_map(), |
| *span, |
| ) { |
| return; |
| } |
| } |
| |
| hir::Node::Crate => return, |
| |
| _ => {} |
| } |
| |
| hir_id = self.tcx.hir().get_parent_item(hir_id); |
| } |
| } |
| |
| /// When encountering an assignment of an unsized trait, like `let x = ""[..];`, provide a |
| /// suggestion to borrow the initializer in order to use have a slice instead. |
| fn suggest_borrow_on_unsized_slice( |
| &self, |
| code: &ObligationCauseCode<'tcx>, |
| err: &mut DiagnosticBuilder<'tcx>, |
| ) { |
| if let &ObligationCauseCode::VariableType(hir_id) = code { |
| let parent_node = self.tcx.hir().get_parent_node(hir_id); |
| if let Some(Node::Local(ref local)) = self.tcx.hir().find(parent_node) { |
| if let Some(ref expr) = local.init { |
| if let hir::ExprKind::Index(_, _) = expr.kind { |
| if let Ok(snippet) = self.tcx.sess.source_map().span_to_snippet(expr.span) { |
| err.span_suggestion( |
| expr.span, |
| "consider borrowing here", |
| format!("&{}", snippet), |
| Applicability::MachineApplicable |
| ); |
| } |
| } |
| } |
| } |
| } |
| } |
| |
| fn mk_obligation_for_def_id( |
| &self, |
| def_id: DefId, |
| output_ty: Ty<'tcx>, |
| cause: ObligationCause<'tcx>, |
| param_env: ty::ParamEnv<'tcx>, |
| ) -> PredicateObligation<'tcx> { |
| let new_trait_ref = ty::TraitRef { |
| def_id, |
| substs: self.tcx.mk_substs_trait(output_ty, &[]), |
| }; |
| Obligation::new(cause, param_env, new_trait_ref.to_predicate()) |
| } |
| |
| /// Given a closure's `DefId`, return the given name of the closure. |
| /// |
| /// This doesn't account for reassignments, but it's only used for suggestions. |
| fn get_closure_name( |
| &self, |
| def_id: DefId, |
| err: &mut DiagnosticBuilder<'_>, |
| msg: &str, |
| ) -> Option<String> { |
| let get_name = |err: &mut DiagnosticBuilder<'_>, kind: &hir::PatKind| -> Option<String> { |
| // Get the local name of this closure. This can be inaccurate because |
| // of the possibility of reassignment, but this should be good enough. |
| match &kind { |
| hir::PatKind::Binding(hir::BindingAnnotation::Unannotated, _, name, None) => { |
| Some(format!("{}", name)) |
| } |
| _ => { |
| err.note(&msg); |
| None |
| } |
| } |
| }; |
| |
| let hir = self.tcx.hir(); |
| let hir_id = hir.as_local_hir_id(def_id)?; |
| let parent_node = hir.get_parent_node(hir_id); |
| match hir.find(parent_node) { |
| Some(hir::Node::Stmt(hir::Stmt { |
| kind: hir::StmtKind::Local(local), .. |
| })) => get_name(err, &local.pat.kind), |
| // Different to previous arm because one is `&hir::Local` and the other |
| // is `P<hir::Local>`. |
| Some(hir::Node::Local(local)) => get_name(err, &local.pat.kind), |
| _ => return None, |
| } |
| } |
| |
| /// We tried to apply the bound to an `fn` or closure. Check whether calling it would |
| /// evaluate to a type that *would* satisfy the trait binding. If it would, suggest calling |
| /// it: `bar(foo)` → `bar(foo())`. This case is *very* likely to be hit if `foo` is `async`. |
| fn suggest_fn_call( |
| &self, |
| obligation: &PredicateObligation<'tcx>, |
| err: &mut DiagnosticBuilder<'_>, |
| trait_ref: &ty::Binder<ty::TraitRef<'tcx>>, |
| points_at_arg: bool, |
| ) { |
| let self_ty = trait_ref.self_ty(); |
| let (def_id, output_ty, callable) = match self_ty.kind { |
| ty::Closure(def_id, substs) => { |
| (def_id, self.closure_sig(def_id, substs).output(), "closure") |
| } |
| ty::FnDef(def_id, _) => { |
| (def_id, self_ty.fn_sig(self.tcx).output(), "function") |
| } |
| _ => return, |
| }; |
| let msg = format!("use parentheses to call the {}", callable); |
| |
| let obligation = self.mk_obligation_for_def_id( |
| trait_ref.def_id(), |
| output_ty.skip_binder(), |
| obligation.cause.clone(), |
| obligation.param_env, |
| ); |
| |
| match self.evaluate_obligation(&obligation) { |
| Ok(EvaluationResult::EvaluatedToOk) | |
| Ok(EvaluationResult::EvaluatedToOkModuloRegions) | |
| Ok(EvaluationResult::EvaluatedToAmbig) => {} |
| _ => return, |
| } |
| let hir = self.tcx.hir(); |
| // Get the name of the callable and the arguments to be used in the suggestion. |
| let snippet = match hir.get_if_local(def_id) { |
| Some(hir::Node::Expr(hir::Expr { |
| kind: hir::ExprKind::Closure(_, decl, _, span, ..), |
| .. |
| })) => { |
| err.span_label(*span, "consider calling this closure"); |
| let name = match self.get_closure_name(def_id, err, &msg) { |
| Some(name) => name, |
| None => return, |
| }; |
| let args = decl.inputs.iter() |
| .map(|_| "_") |
| .collect::<Vec<_>>() |
| .join(", "); |
| format!("{}({})", name, args) |
| } |
| Some(hir::Node::Item(hir::Item { |
| ident, |
| kind: hir::ItemKind::Fn(.., body_id), |
| .. |
| })) => { |
| err.span_label(ident.span, "consider calling this function"); |
| let body = hir.body(*body_id); |
| let args = body.params.iter() |
| .map(|arg| match &arg.pat.kind { |
| hir::PatKind::Binding(_, _, ident, None) |
| // FIXME: provide a better suggestion when encountering `SelfLower`, it |
| // should suggest a method call. |
| if ident.name != kw::SelfLower => ident.to_string(), |
| _ => "_".to_string(), |
| }) |
| .collect::<Vec<_>>() |
| .join(", "); |
| format!("{}({})", ident, args) |
| } |
| _ => return, |
| }; |
| if points_at_arg { |
| // When the obligation error has been ensured to have been caused by |
| // an argument, the `obligation.cause.span` points at the expression |
| // of the argument, so we can provide a suggestion. This is signaled |
| // by `points_at_arg`. Otherwise, we give a more general note. |
| err.span_suggestion( |
| obligation.cause.span, |
| &msg, |
| snippet, |
| Applicability::HasPlaceholders, |
| ); |
| } else { |
| err.help(&format!("{}: `{}`", msg, snippet)); |
| } |
| } |
| |
| fn suggest_add_reference_to_arg( |
| &self, |
| obligation: &PredicateObligation<'tcx>, |
| err: &mut DiagnosticBuilder<'tcx>, |
| trait_ref: &ty::Binder<ty::TraitRef<'tcx>>, |
| points_at_arg: bool, |
| has_custom_message: bool, |
| ) -> bool { |
| if !points_at_arg { |
| return false; |
| } |
| |
| let span = obligation.cause.span; |
| let param_env = obligation.param_env; |
| let trait_ref = trait_ref.skip_binder(); |
| |
| if let ObligationCauseCode::ImplDerivedObligation(obligation) = &obligation.cause.code { |
| // Try to apply the original trait binding obligation by borrowing. |
| let self_ty = trait_ref.self_ty(); |
| let found = self_ty.to_string(); |
| let new_self_ty = self.tcx.mk_imm_ref(self.tcx.lifetimes.re_static, self_ty); |
| let substs = self.tcx.mk_substs_trait(new_self_ty, &[]); |
| let new_trait_ref = ty::TraitRef::new(obligation.parent_trait_ref.def_id(), substs); |
| let new_obligation = Obligation::new( |
| ObligationCause::dummy(), |
| param_env, |
| new_trait_ref.to_predicate(), |
| ); |
| if self.predicate_must_hold_modulo_regions(&new_obligation) { |
| if let Ok(snippet) = self.tcx.sess.source_map().span_to_snippet(span) { |
| // We have a very specific type of error, where just borrowing this argument |
| // might solve the problem. In cases like this, the important part is the |
| // original type obligation, not the last one that failed, which is arbitrary. |
| // Because of this, we modify the error to refer to the original obligation and |
| // return early in the caller. |
| let msg = format!( |
| "the trait bound `{}: {}` is not satisfied", |
| found, |
| obligation.parent_trait_ref.skip_binder().print_only_trait_path(), |
| ); |
| if has_custom_message { |
| err.note(&msg); |
| } else { |
| err.message = vec![(msg, Style::NoStyle)]; |
| } |
| if snippet.starts_with('&') { |
| // This is already a literal borrow and the obligation is failing |
| // somewhere else in the obligation chain. Do not suggest non-sense. |
| return false; |
| } |
| err.span_label(span, &format!( |
| "expected an implementor of trait `{}`", |
| obligation.parent_trait_ref.skip_binder().print_only_trait_path(), |
| )); |
| err.span_suggestion( |
| span, |
| "consider borrowing here", |
| format!("&{}", snippet), |
| Applicability::MaybeIncorrect, |
| ); |
| return true; |
| } |
| } |
| } |
| false |
| } |
| |
| /// Whenever references are used by mistake, like `for (i, e) in &vec.iter().enumerate()`, |
| /// suggest removing these references until we reach a type that implements the trait. |
| fn suggest_remove_reference( |
| &self, |
| obligation: &PredicateObligation<'tcx>, |
| err: &mut DiagnosticBuilder<'tcx>, |
| trait_ref: &ty::Binder<ty::TraitRef<'tcx>>, |
| ) { |
| let trait_ref = trait_ref.skip_binder(); |
| let span = obligation.cause.span; |
| |
| if let Ok(snippet) = self.tcx.sess.source_map().span_to_snippet(span) { |
| let refs_number = snippet.chars() |
| .filter(|c| !c.is_whitespace()) |
| .take_while(|c| *c == '&') |
| .count(); |
| if let Some('\'') = snippet.chars() |
| .filter(|c| !c.is_whitespace()) |
| .skip(refs_number) |
| .next() |
| { // Do not suggest removal of borrow from type arguments. |
| return; |
| } |
| |
| let mut trait_type = trait_ref.self_ty(); |
| |
| for refs_remaining in 0..refs_number { |
| if let ty::Ref(_, t_type, _) = trait_type.kind { |
| trait_type = t_type; |
| |
| let new_obligation = self.mk_obligation_for_def_id( |
| trait_ref.def_id, |
| trait_type, |
| ObligationCause::dummy(), |
| obligation.param_env, |
| ); |
| |
| if self.predicate_may_hold(&new_obligation) { |
| let sp = self.tcx.sess.source_map() |
| .span_take_while(span, |c| c.is_whitespace() || *c == '&'); |
| |
| let remove_refs = refs_remaining + 1; |
| let format_str = format!("consider removing {} leading `&`-references", |
| remove_refs); |
| |
| err.span_suggestion_short( |
| sp, &format_str, String::new(), Applicability::MachineApplicable |
| ); |
| break; |
| } |
| } else { |
| break; |
| } |
| } |
| } |
| } |
| |
| /// Check if the trait bound is implemented for a different mutability and note it in the |
| /// final error. |
| fn suggest_change_mut( |
| &self, |
| obligation: &PredicateObligation<'tcx>, |
| err: &mut DiagnosticBuilder<'tcx>, |
| trait_ref: &ty::Binder<ty::TraitRef<'tcx>>, |
| points_at_arg: bool, |
| ) { |
| let span = obligation.cause.span; |
| if let Ok(snippet) = self.tcx.sess.source_map().span_to_snippet(span) { |
| let refs_number = snippet.chars() |
| .filter(|c| !c.is_whitespace()) |
| .take_while(|c| *c == '&') |
| .count(); |
| if let Some('\'') = snippet.chars() |
| .filter(|c| !c.is_whitespace()) |
| .skip(refs_number) |
| .next() |
| { // Do not suggest removal of borrow from type arguments. |
| return; |
| } |
| let trait_ref = self.resolve_vars_if_possible(trait_ref); |
| if trait_ref.has_infer_types() { |
| // Do not ICE while trying to find if a reborrow would succeed on a trait with |
| // unresolved bindings. |
| return; |
| } |
| |
| if let ty::Ref(region, t_type, mutability) = trait_ref.skip_binder().self_ty().kind { |
| let trait_type = match mutability { |
| hir::Mutability::Mutable => self.tcx.mk_imm_ref(region, t_type), |
| hir::Mutability::Immutable => self.tcx.mk_mut_ref(region, t_type), |
| }; |
| |
| let new_obligation = self.mk_obligation_for_def_id( |
| trait_ref.skip_binder().def_id, |
| trait_type, |
| ObligationCause::dummy(), |
| obligation.param_env, |
| ); |
| |
| if self.evaluate_obligation_no_overflow( |
| &new_obligation, |
| ).must_apply_modulo_regions() { |
| let sp = self.tcx.sess.source_map() |
| .span_take_while(span, |c| c.is_whitespace() || *c == '&'); |
| if points_at_arg && |
| mutability == hir::Mutability::Immutable && |
| refs_number > 0 |
| { |
| err.span_suggestion( |
| sp, |
| "consider changing this borrow's mutability", |
| "&mut ".to_string(), |
| Applicability::MachineApplicable, |
| ); |
| } else { |
| err.note(&format!( |
| "`{}` is implemented for `{:?}`, but not for `{:?}`", |
| trait_ref.print_only_trait_path(), |
| trait_type, |
| trait_ref.skip_binder().self_ty(), |
| )); |
| } |
| } |
| } |
| } |
| } |
| |
| fn suggest_semicolon_removal( |
| &self, |
| obligation: &PredicateObligation<'tcx>, |
| err: &mut DiagnosticBuilder<'tcx>, |
| span: Span, |
| trait_ref: &ty::Binder<ty::TraitRef<'tcx>>, |
| ) { |
| let hir = self.tcx.hir(); |
| let parent_node = hir.get_parent_node(obligation.cause.body_id); |
| let node = hir.find(parent_node); |
| if let Some(hir::Node::Item(hir::Item { |
| kind: hir::ItemKind::Fn(sig, _, body_id), |
| .. |
| })) = node { |
| let body = hir.body(*body_id); |
| if let hir::ExprKind::Block(blk, _) = &body.value.kind { |
| if sig.decl.output.span().overlaps(span) && blk.expr.is_none() && |
| "()" == &trait_ref.self_ty().to_string() |
| { |
| // FIXME(estebank): When encountering a method with a trait |
| // bound not satisfied in the return type with a body that has |
| // no return, suggest removal of semicolon on last statement. |
| // Once that is added, close #54771. |
| if let Some(ref stmt) = blk.stmts.last() { |
| let sp = self.tcx.sess.source_map().end_point(stmt.span); |
| err.span_label(sp, "consider removing this semicolon"); |
| } |
| } |
| } |
| } |
| } |
| |
| /// Given some node representing a fn-like thing in the HIR map, |
| /// returns a span and `ArgKind` information that describes the |
| /// arguments it expects. This can be supplied to |
| /// `report_arg_count_mismatch`. |
| pub fn get_fn_like_arguments(&self, node: Node<'_>) -> (Span, Vec<ArgKind>) { |
| match node { |
| Node::Expr(&hir::Expr { |
| kind: hir::ExprKind::Closure(_, ref _decl, id, span, _), |
| .. |
| }) => { |
| (self.tcx.sess.source_map().def_span(span), |
| self.tcx.hir().body(id).params.iter() |
| .map(|arg| { |
| if let hir::Pat { |
| kind: hir::PatKind::Tuple(ref args, _), |
| span, |
| .. |
| } = *arg.pat { |
| ArgKind::Tuple( |
| Some(span), |
| args.iter().map(|pat| { |
| let snippet = self.tcx.sess.source_map() |
| .span_to_snippet(pat.span).unwrap(); |
| (snippet, "_".to_owned()) |
| }).collect::<Vec<_>>(), |
| ) |
| } else { |
| let name = self.tcx.sess.source_map() |
| .span_to_snippet(arg.pat.span).unwrap(); |
| ArgKind::Arg(name, "_".to_owned()) |
| } |
| }) |
| .collect::<Vec<ArgKind>>()) |
| } |
| Node::Item(&hir::Item { |
| span, |
| kind: hir::ItemKind::Fn(ref sig, ..), |
| .. |
| }) | |
| Node::ImplItem(&hir::ImplItem { |
| span, |
| kind: hir::ImplItemKind::Method(ref sig, _), |
| .. |
| }) | |
| Node::TraitItem(&hir::TraitItem { |
| span, |
| kind: hir::TraitItemKind::Method(ref sig, _), |
| .. |
| }) => { |
| (self.tcx.sess.source_map().def_span(span), sig.decl.inputs.iter() |
| .map(|arg| match arg.clone().kind { |
| hir::TyKind::Tup(ref tys) => ArgKind::Tuple( |
| Some(arg.span), |
| vec![("_".to_owned(), "_".to_owned()); tys.len()] |
| ), |
| _ => ArgKind::empty() |
| }).collect::<Vec<ArgKind>>()) |
| } |
| Node::Ctor(ref variant_data) => { |
| let span = variant_data.ctor_hir_id() |
| .map(|hir_id| self.tcx.hir().span(hir_id)) |
| .unwrap_or(DUMMY_SP); |
| let span = self.tcx.sess.source_map().def_span(span); |
| |
| (span, vec![ArgKind::empty(); variant_data.fields().len()]) |
| } |
| _ => panic!("non-FnLike node found: {:?}", node), |
| } |
| } |
| |
| /// Reports an error when the number of arguments needed by a |
| /// trait match doesn't match the number that the expression |
| /// provides. |
| pub fn report_arg_count_mismatch( |
| &self, |
| span: Span, |
| found_span: Option<Span>, |
| expected_args: Vec<ArgKind>, |
| found_args: Vec<ArgKind>, |
| is_closure: bool, |
| ) -> DiagnosticBuilder<'tcx> { |
| let kind = if is_closure { "closure" } else { "function" }; |
| |
| let args_str = |arguments: &[ArgKind], other: &[ArgKind]| { |
| let arg_length = arguments.len(); |
| let distinct = match &other[..] { |
| &[ArgKind::Tuple(..)] => true, |
| _ => false, |
| }; |
| match (arg_length, arguments.get(0)) { |
| (1, Some(&ArgKind::Tuple(_, ref fields))) => { |
| format!("a single {}-tuple as argument", fields.len()) |
| } |
| _ => format!("{} {}argument{}", |
| arg_length, |
| if distinct && arg_length > 1 { "distinct " } else { "" }, |
| pluralize!(arg_length)) |
| } |
| }; |
| |
| let expected_str = args_str(&expected_args, &found_args); |
| let found_str = args_str(&found_args, &expected_args); |
| |
| let mut err = struct_span_err!( |
| self.tcx.sess, |
| span, |
| E0593, |
| "{} is expected to take {}, but it takes {}", |
| kind, |
| expected_str, |
| found_str, |
| ); |
| |
| err.span_label(span, format!("expected {} that takes {}", kind, expected_str)); |
| |
| if let Some(found_span) = found_span { |
| err.span_label(found_span, format!("takes {}", found_str)); |
| |
| // move |_| { ... } |
| // ^^^^^^^^-- def_span |
| // |
| // move |_| { ... } |
| // ^^^^^-- prefix |
| let prefix_span = self.tcx.sess.source_map().span_until_non_whitespace(found_span); |
| // move |_| { ... } |
| // ^^^-- pipe_span |
| let pipe_span = if let Some(span) = found_span.trim_start(prefix_span) { |
| span |
| } else { |
| found_span |
| }; |
| |
| // Suggest to take and ignore the arguments with expected_args_length `_`s if |
| // found arguments is empty (assume the user just wants to ignore args in this case). |
| // For example, if `expected_args_length` is 2, suggest `|_, _|`. |
| if found_args.is_empty() && is_closure { |
| let underscores = vec!["_"; expected_args.len()].join(", "); |
| err.span_suggestion( |
| pipe_span, |
| &format!( |
| "consider changing the closure to take and ignore the expected argument{}", |
| if expected_args.len() < 2 { |
| "" |
| } else { |
| "s" |
| } |
| ), |
| format!("|{}|", underscores), |
| Applicability::MachineApplicable, |
| ); |
| } |
| |
| if let &[ArgKind::Tuple(_, ref fields)] = &found_args[..] { |
| if fields.len() == expected_args.len() { |
| let sugg = fields.iter() |
| .map(|(name, _)| name.to_owned()) |
| .collect::<Vec<String>>() |
| .join(", "); |
| err.span_suggestion( |
| found_span, |
| "change the closure to take multiple arguments instead of a single tuple", |
| format!("|{}|", sugg), |
| Applicability::MachineApplicable, |
| ); |
| } |
| } |
| if let &[ArgKind::Tuple(_, ref fields)] = &expected_args[..] { |
| if fields.len() == found_args.len() && is_closure { |
| let sugg = format!( |
| "|({}){}|", |
| found_args.iter() |
| .map(|arg| match arg { |
| ArgKind::Arg(name, _) => name.to_owned(), |
| _ => "_".to_owned(), |
| }) |
| .collect::<Vec<String>>() |
| .join(", "), |
| // add type annotations if available |
| if found_args.iter().any(|arg| match arg { |
| ArgKind::Arg(_, ty) => ty != "_", |
| _ => false, |
| }) { |
| format!(": ({})", |
| fields.iter() |
| .map(|(_, ty)| ty.to_owned()) |
| .collect::<Vec<String>>() |
| .join(", ")) |
| } else { |
| String::new() |
| }, |
| ); |
| err.span_suggestion( |
| found_span, |
| "change the closure to accept a tuple instead of individual arguments", |
| sugg, |
| Applicability::MachineApplicable, |
| ); |
| } |
| } |
| } |
| |
| err |
| } |
| |
| fn report_closure_arg_mismatch( |
| &self, |
| span: Span, |
| found_span: Option<Span>, |
| expected_ref: ty::PolyTraitRef<'tcx>, |
| found: ty::PolyTraitRef<'tcx>, |
| ) -> DiagnosticBuilder<'tcx> { |
| fn build_fn_sig_string<'tcx>(tcx: TyCtxt<'tcx>, trait_ref: &ty::TraitRef<'tcx>) -> String { |
| let inputs = trait_ref.substs.type_at(1); |
| let sig = if let ty::Tuple(inputs) = inputs.kind { |
| tcx.mk_fn_sig( |
| inputs.iter().map(|k| k.expect_ty()), |
| tcx.mk_ty_infer(ty::TyVar(ty::TyVid { index: 0 })), |
| false, |
| hir::Unsafety::Normal, |
| ::rustc_target::spec::abi::Abi::Rust |
| ) |
| } else { |
| tcx.mk_fn_sig( |
| ::std::iter::once(inputs), |
| tcx.mk_ty_infer(ty::TyVar(ty::TyVid { index: 0 })), |
| false, |
| hir::Unsafety::Normal, |
| ::rustc_target::spec::abi::Abi::Rust |
| ) |
| }; |
| ty::Binder::bind(sig).to_string() |
| } |
| |
| let argument_is_closure = expected_ref.skip_binder().substs.type_at(0).is_closure(); |
| let mut err = struct_span_err!(self.tcx.sess, span, E0631, |
| "type mismatch in {} arguments", |
| if argument_is_closure { "closure" } else { "function" }); |
| |
| let found_str = format!( |
| "expected signature of `{}`", |
| build_fn_sig_string(self.tcx, found.skip_binder()) |
| ); |
| err.span_label(span, found_str); |
| |
| let found_span = found_span.unwrap_or(span); |
| let expected_str = format!( |
| "found signature of `{}`", |
| build_fn_sig_string(self.tcx, expected_ref.skip_binder()) |
| ); |
| err.span_label(found_span, expected_str); |
| |
| err |
| } |
| } |
| |
| impl<'tcx> TyCtxt<'tcx> { |
| pub fn recursive_type_with_infinite_size_error(self, |
| type_def_id: DefId) |
| -> DiagnosticBuilder<'tcx> |
| { |
| assert!(type_def_id.is_local()); |
| let span = self.hir().span_if_local(type_def_id).unwrap(); |
| let span = self.sess.source_map().def_span(span); |
| let mut err = struct_span_err!(self.sess, span, E0072, |
| "recursive type `{}` has infinite size", |
| self.def_path_str(type_def_id)); |
| err.span_label(span, "recursive type has infinite size"); |
| err.help(&format!("insert indirection (e.g., a `Box`, `Rc`, or `&`) \ |
| at some point to make `{}` representable", |
| self.def_path_str(type_def_id))); |
| err |
| } |
| |
| pub fn report_object_safety_error( |
| self, |
| span: Span, |
| trait_def_id: DefId, |
| violations: Vec<ObjectSafetyViolation>, |
| ) -> DiagnosticBuilder<'tcx> { |
| let trait_str = self.def_path_str(trait_def_id); |
| let span = self.sess.source_map().def_span(span); |
| let mut err = struct_span_err!( |
| self.sess, span, E0038, |
| "the trait `{}` cannot be made into an object", |
| trait_str); |
| err.span_label(span, format!("the trait `{}` cannot be made into an object", trait_str)); |
| |
| let mut reported_violations = FxHashSet::default(); |
| for violation in violations { |
| if reported_violations.insert(violation.clone()) { |
| match violation.span() { |
| Some(span) => err.span_label(span, violation.error_msg()), |
| None => err.note(&violation.error_msg()), |
| }; |
| } |
| } |
| |
| if self.sess.trait_methods_not_found.borrow().contains(&span) { |
| // Avoid emitting error caused by non-existing method (#58734) |
| err.cancel(); |
| } |
| |
| err |
| } |
| } |
| |
| impl<'a, 'tcx> InferCtxt<'a, 'tcx> { |
| fn maybe_report_ambiguity( |
| &self, |
| obligation: &PredicateObligation<'tcx>, |
| body_id: Option<hir::BodyId>, |
| ) { |
| // Unable to successfully determine, probably means |
| // insufficient type information, but could mean |
| // ambiguous impls. The latter *ought* to be a |
| // coherence violation, so we don't report it here. |
| |
| let predicate = self.resolve_vars_if_possible(&obligation.predicate); |
| let span = obligation.cause.span; |
| |
| debug!( |
| "maybe_report_ambiguity(predicate={:?}, obligation={:?} body_id={:?}, code={:?})", |
| predicate, |
| obligation, |
| body_id, |
| obligation.cause.code, |
| ); |
| |
| // Ambiguity errors are often caused as fallout from earlier |
| // errors. So just ignore them if this infcx is tainted. |
| if self.is_tainted_by_errors() { |
| return; |
| } |
| |
| match predicate { |
| ty::Predicate::Trait(ref data) => { |
| let trait_ref = data.to_poly_trait_ref(); |
| let self_ty = trait_ref.self_ty(); |
| debug!("self_ty {:?} {:?} trait_ref {:?}", self_ty, self_ty.kind, trait_ref); |
| |
| if predicate.references_error() { |
| return; |
| } |
| // Typically, this ambiguity should only happen if |
| // there are unresolved type inference variables |
| // (otherwise it would suggest a coherence |
| // failure). But given #21974 that is not necessarily |
| // the case -- we can have multiple where clauses that |
| // are only distinguished by a region, which results |
| // in an ambiguity even when all types are fully |
| // known, since we don't dispatch based on region |
| // relationships. |
| |
| // This is kind of a hack: it frequently happens that some earlier |
| // error prevents types from being fully inferred, and then we get |
| // a bunch of uninteresting errors saying something like "<generic |
| // #0> doesn't implement Sized". It may even be true that we |
| // could just skip over all checks where the self-ty is an |
| // inference variable, but I was afraid that there might be an |
| // inference variable created, registered as an obligation, and |
| // then never forced by writeback, and hence by skipping here we'd |
| // be ignoring the fact that we don't KNOW the type works |
| // out. Though even that would probably be harmless, given that |
| // we're only talking about builtin traits, which are known to be |
| // inhabited. We used to check for `self.tcx.sess.has_errors()` to |
| // avoid inundating the user with unnecessary errors, but we now |
| // check upstream for type errors and dont add the obligations to |
| // begin with in those cases. |
| if |
| self.tcx.lang_items().sized_trait() |
| .map_or(false, |sized_id| sized_id == trait_ref.def_id()) |
| { |
| self.need_type_info_err(body_id, span, self_ty).emit(); |
| } else { |
| let mut err = struct_span_err!( |
| self.tcx.sess, |
| span, |
| E0283, |
| "type annotations needed: cannot resolve `{}`", |
| predicate, |
| ); |
| self.note_obligation_cause(&mut err, obligation); |
| err.emit(); |
| } |
| } |
| |
| ty::Predicate::WellFormed(ty) => { |
| // Same hacky approach as above to avoid deluging user |
| // with error messages. |
| if !ty.references_error() && !self.tcx.sess.has_errors() { |
| self.need_type_info_err(body_id, span, ty).emit(); |
| } |
| } |
| |
| ty::Predicate::Subtype(ref data) => { |
| if data.references_error() || self.tcx.sess.has_errors() { |
| // no need to overload user in such cases |
| } else { |
| let &SubtypePredicate { a_is_expected: _, a, b } = data.skip_binder(); |
| // both must be type variables, or the other would've been instantiated |
| assert!(a.is_ty_var() && b.is_ty_var()); |
| self.need_type_info_err(body_id, |
| obligation.cause.span, |
| a).emit(); |
| } |
| } |
| |
| _ => { |
| if !self.tcx.sess.has_errors() { |
| let mut err = struct_span_err!( |
| self.tcx.sess, |
| obligation.cause.span, |
| E0284, |
| "type annotations needed: cannot resolve `{}`", |
| predicate, |
| ); |
| self.note_obligation_cause(&mut err, obligation); |
| err.emit(); |
| } |
| } |
| } |
| } |
| |
| /// Returns `true` if the trait predicate may apply for *some* assignment |
| /// to the type parameters. |
| fn predicate_can_apply( |
| &self, |
| param_env: ty::ParamEnv<'tcx>, |
| pred: ty::PolyTraitRef<'tcx>, |
| ) -> bool { |
| struct ParamToVarFolder<'a, 'tcx> { |
| infcx: &'a InferCtxt<'a, 'tcx>, |
| var_map: FxHashMap<Ty<'tcx>, Ty<'tcx>>, |
| } |
| |
| impl<'a, 'tcx> TypeFolder<'tcx> for ParamToVarFolder<'a, 'tcx> { |
| fn tcx<'b>(&'b self) -> TyCtxt<'tcx> { self.infcx.tcx } |
| |
| fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> { |
| if let ty::Param(ty::ParamTy {name, .. }) = ty.kind { |
| let infcx = self.infcx; |
| self.var_map.entry(ty).or_insert_with(|| |
| infcx.next_ty_var( |
| TypeVariableOrigin { |
| kind: TypeVariableOriginKind::TypeParameterDefinition(name), |
| span: DUMMY_SP, |
| } |
| ) |
| ) |
| } else { |
| ty.super_fold_with(self) |
| } |
| } |
| } |
| |
| self.probe(|_| { |
| let mut selcx = SelectionContext::new(self); |
| |
| let cleaned_pred = pred.fold_with(&mut ParamToVarFolder { |
| infcx: self, |
| var_map: Default::default() |
| }); |
| |
| let cleaned_pred = super::project::normalize( |
| &mut selcx, |
| param_env, |
| ObligationCause::dummy(), |
| &cleaned_pred |
| ).value; |
| |
| let obligation = Obligation::new( |
| ObligationCause::dummy(), |
| param_env, |
| cleaned_pred.to_predicate() |
| ); |
| |
| self.predicate_may_hold(&obligation) |
| }) |
| } |
| |
| fn note_obligation_cause( |
| &self, |
| err: &mut DiagnosticBuilder<'_>, |
| obligation: &PredicateObligation<'tcx>, |
| ) { |
| // First, attempt to add note to this error with an async-await-specific |
| // message, and fall back to regular note otherwise. |
| if !self.note_obligation_cause_for_async_await(err, obligation) { |
| self.note_obligation_cause_code(err, &obligation.predicate, &obligation.cause.code, |
| &mut vec![]); |
| } |
| } |
| |
| /// Adds an async-await specific note to the diagnostic: |
| /// |
| /// ```ignore (diagnostic) |
| /// note: future does not implement `std::marker::Send` because this value is used across an |
| /// await |
| /// --> $DIR/issue-64130-non-send-future-diags.rs:15:5 |
| /// | |
| /// LL | let g = x.lock().unwrap(); |
| /// | - has type `std::sync::MutexGuard<'_, u32>` |
| /// LL | baz().await; |
| /// | ^^^^^^^^^^^ await occurs here, with `g` maybe used later |
| /// LL | } |
| /// | - `g` is later dropped here |
| /// ``` |
| /// |
| /// Returns `true` if an async-await specific note was added to the diagnostic. |
| fn note_obligation_cause_for_async_await( |
| &self, |
| err: &mut DiagnosticBuilder<'_>, |
| obligation: &PredicateObligation<'tcx>, |
| ) -> bool { |
| debug!("note_obligation_cause_for_async_await: obligation.predicate={:?} \ |
| obligation.cause.span={:?}", obligation.predicate, obligation.cause.span); |
| let source_map = self.tcx.sess.source_map(); |
| |
| // Look into the obligation predicate to determine the type in the generator which meant |
| // that the predicate was not satisifed. |
| let (trait_ref, target_ty) = match obligation.predicate { |
| ty::Predicate::Trait(trait_predicate) => |
| (trait_predicate.skip_binder().trait_ref, trait_predicate.skip_binder().self_ty()), |
| _ => return false, |
| }; |
| debug!("note_obligation_cause_for_async_await: target_ty={:?}", target_ty); |
| |
| // Attempt to detect an async-await error by looking at the obligation causes, looking |
| // for only generators, generator witnesses, opaque types or `std::future::GenFuture` to |
| // be present. |
| // |
| // When a future does not implement a trait because of a captured type in one of the |
| // generators somewhere in the call stack, then the result is a chain of obligations. |
| // Given a `async fn` A that calls a `async fn` B which captures a non-send type and that |
| // future is passed as an argument to a function C which requires a `Send` type, then the |
| // chain looks something like this: |
| // |
| // - `BuiltinDerivedObligation` with a generator witness (B) |
| // - `BuiltinDerivedObligation` with a generator (B) |
| // - `BuiltinDerivedObligation` with `std::future::GenFuture` (B) |
| // - `BuiltinDerivedObligation` with `impl std::future::Future` (B) |
| // - `BuiltinDerivedObligation` with `impl std::future::Future` (B) |
| // - `BuiltinDerivedObligation` with a generator witness (A) |
| // - `BuiltinDerivedObligation` with a generator (A) |
| // - `BuiltinDerivedObligation` with `std::future::GenFuture` (A) |
| // - `BuiltinDerivedObligation` with `impl std::future::Future` (A) |
| // - `BuiltinDerivedObligation` with `impl std::future::Future` (A) |
| // - `BindingObligation` with `impl_send (Send requirement) |
| // |
| // The first obligations in the chain can be used to get the details of the type that is |
| // captured but the entire chain must be inspected to detect this case. |
| let mut generator = None; |
| let mut next_code = Some(&obligation.cause.code); |
| while let Some(code) = next_code { |
| debug!("note_obligation_cause_for_async_await: code={:?}", code); |
| match code { |
| ObligationCauseCode::BuiltinDerivedObligation(derived_obligation) | |
| ObligationCauseCode::ImplDerivedObligation(derived_obligation) => { |
| debug!("note_obligation_cause_for_async_await: self_ty.kind={:?}", |
| derived_obligation.parent_trait_ref.self_ty().kind); |
| match derived_obligation.parent_trait_ref.self_ty().kind { |
| ty::Adt(ty::AdtDef { did, .. }, ..) if |
| self.tcx.is_diagnostic_item(sym::gen_future, *did) => {}, |
| ty::Generator(did, ..) => generator = generator.or(Some(did)), |
| ty::GeneratorWitness(_) | ty::Opaque(..) => {}, |
| _ => return false, |
| } |
| |
| next_code = Some(derived_obligation.parent_code.as_ref()); |
| }, |
| ObligationCauseCode::ItemObligation(_) | ObligationCauseCode::BindingObligation(..) |
| if generator.is_some() => break, |
| _ => return false, |
| } |
| } |
| |
| let generator_did = generator.expect("can only reach this if there was a generator"); |
| |
| // Only continue to add a note if the generator is from an `async` function. |
| let parent_node = self.tcx.parent(generator_did) |
| .and_then(|parent_did| self.tcx.hir().get_if_local(parent_did)); |
| debug!("note_obligation_cause_for_async_await: parent_node={:?}", parent_node); |
| if let Some(hir::Node::Item(hir::Item { |
| kind: hir::ItemKind::Fn(sig, _, _), |
| .. |
| })) = parent_node { |
| debug!("note_obligation_cause_for_async_await: header={:?}", sig.header); |
| if sig.header.asyncness != hir::IsAsync::Async { |
| return false; |
| } |
| } |
| |
| let span = self.tcx.def_span(generator_did); |
| // Do not ICE on closure typeck (#66868). |
| if let None = self.tcx.hir().as_local_hir_id(generator_did) { |
| return false; |
| } |
| let tables = self.tcx.typeck_tables_of(generator_did); |
| debug!("note_obligation_cause_for_async_await: generator_did={:?} span={:?} ", |
| generator_did, span); |
| |
| // Look for a type inside the generator interior that matches the target type to get |
| // a span. |
| let target_span = tables.generator_interior_types.iter() |
| .find(|ty::GeneratorInteriorTypeCause { ty, .. }| ty::TyS::same_type(*ty, target_ty)) |
| .map(|ty::GeneratorInteriorTypeCause { span, scope_span, .. }| |
| (span, source_map.span_to_snippet(*span), scope_span)); |
| if let Some((target_span, Ok(snippet), scope_span)) = target_span { |
| // Look at the last interior type to get a span for the `.await`. |
| let await_span = tables.generator_interior_types.iter().map(|i| i.span).last().unwrap(); |
| let mut span = MultiSpan::from_span(await_span); |
| span.push_span_label( |
| await_span, format!("await occurs here, with `{}` maybe used later", snippet)); |
| |
| span.push_span_label(*target_span, format!("has type `{}`", target_ty)); |
| |
| // If available, use the scope span to annotate the drop location. |
| if let Some(scope_span) = scope_span { |
| span.push_span_label( |
| source_map.end_point(*scope_span), |
| format!("`{}` is later dropped here", snippet), |
| ); |
| } |
| |
| err.span_note(span, &format!( |
| "future does not implement `{}` as this value is used across an await", |
| trait_ref.print_only_trait_path(), |
| )); |
| |
| // Add a note for the item obligation that remains - normally a note pointing to the |
| // bound that introduced the obligation (e.g. `T: Send`). |
| debug!("note_obligation_cause_for_async_await: next_code={:?}", next_code); |
| self.note_obligation_cause_code( |
| err, |
| &obligation.predicate, |
| next_code.unwrap(), |
| &mut Vec::new(), |
| ); |
| |
| true |
| } else { |
| false |
| } |
| } |
| |
| fn note_obligation_cause_code<T>(&self, |
| err: &mut DiagnosticBuilder<'_>, |
| predicate: &T, |
| cause_code: &ObligationCauseCode<'tcx>, |
| obligated_types: &mut Vec<&ty::TyS<'tcx>>) |
| where T: fmt::Display |
| { |
| let tcx = self.tcx; |
| match *cause_code { |
| ObligationCauseCode::ExprAssignable | |
| ObligationCauseCode::MatchExpressionArm { .. } | |
| ObligationCauseCode::MatchExpressionArmPattern { .. } | |
| ObligationCauseCode::IfExpression { .. } | |
| ObligationCauseCode::IfExpressionWithNoElse | |
| ObligationCauseCode::MainFunctionType | |
| ObligationCauseCode::StartFunctionType | |
| ObligationCauseCode::IntrinsicType | |
| ObligationCauseCode::MethodReceiver | |
| ObligationCauseCode::ReturnNoExpression | |
| ObligationCauseCode::MiscObligation => {} |
| ObligationCauseCode::SliceOrArrayElem => { |
| err.note("slice and array elements must have `Sized` type"); |
| } |
| ObligationCauseCode::TupleElem => { |
| err.note("only the last element of a tuple may have a dynamically sized type"); |
| } |
| ObligationCauseCode::ProjectionWf(data) => { |
| err.note(&format!( |
| "required so that the projection `{}` is well-formed", |
| data, |
| )); |
| } |
| ObligationCauseCode::ReferenceOutlivesReferent(ref_ty) => { |
| err.note(&format!( |
| "required so that reference `{}` does not outlive its referent", |
| ref_ty, |
| )); |
| } |
| ObligationCauseCode::ObjectTypeBound(object_ty, region) => { |
| err.note(&format!( |
| "required so that the lifetime bound of `{}` for `{}` is satisfied", |
| region, |
| object_ty, |
| )); |
| } |
| ObligationCauseCode::ItemObligation(item_def_id) => { |
| let item_name = tcx.def_path_str(item_def_id); |
| let msg = format!("required by `{}`", item_name); |
| |
| if let Some(sp) = tcx.hir().span_if_local(item_def_id) { |
| let sp = tcx.sess.source_map().def_span(sp); |
| err.span_label(sp, &msg); |
| } else { |
| err.note(&msg); |
| } |
| } |
| ObligationCauseCode::BindingObligation(item_def_id, span) => { |
| let item_name = tcx.def_path_str(item_def_id); |
| let msg = format!("required by this bound in `{}`", item_name); |
| if let Some(ident) = tcx.opt_item_name(item_def_id) { |
| err.span_label(ident.span, ""); |
| } |
| if span != DUMMY_SP { |
| err.span_label(span, &msg); |
| } else { |
| err.note(&msg); |
| } |
| } |
| ObligationCauseCode::ObjectCastObligation(object_ty) => { |
| err.note(&format!("required for the cast to the object type `{}`", |
| self.ty_to_string(object_ty))); |
| } |
| ObligationCauseCode::Coercion { source: _, target } => { |
| err.note(&format!("required by cast to type `{}`", |
| self.ty_to_string(target))); |
| } |
| ObligationCauseCode::RepeatVec(suggest_const_in_array_repeat_expressions) => { |
| err.note("the `Copy` trait is required because the \ |
| repeated element will be copied"); |
| if suggest_const_in_array_repeat_expressions { |
| err.note("this array initializer can be evaluated at compile-time, for more \ |
| information, see issue \ |
| https://github.com/rust-lang/rust/issues/49147"); |
| if tcx.sess.opts.unstable_features.is_nightly_build() { |
| err.help("add `#![feature(const_in_array_repeat_expressions)]` to the \ |
| crate attributes to enable"); |
| } |
| } |
| } |
| ObligationCauseCode::VariableType(_) => { |
| err.note("all local variables must have a statically known size"); |
| if !self.tcx.features().unsized_locals { |
| err.help("unsized locals are gated as an unstable feature"); |
| } |
| } |
| ObligationCauseCode::SizedArgumentType => { |
| err.note("all function arguments must have a statically known size"); |
| if !self.tcx.features().unsized_locals { |
| err.help("unsized locals are gated as an unstable feature"); |
| } |
| } |
| ObligationCauseCode::SizedReturnType => { |
| err.note("the return type of a function must have a \ |
| statically known size"); |
| } |
| ObligationCauseCode::SizedYieldType => { |
| err.note("the yield type of a generator must have a \ |
| statically known size"); |
| } |
| ObligationCauseCode::AssignmentLhsSized => { |
| err.note("the left-hand-side of an assignment must have a statically known size"); |
| } |
| ObligationCauseCode::TupleInitializerSized => { |
| err.note("tuples must have a statically known size to be initialized"); |
| } |
| ObligationCauseCode::StructInitializerSized => { |
| err.note("structs must have a statically known size to be initialized"); |
| } |
| ObligationCauseCode::FieldSized { adt_kind: ref item, last } => { |
| match *item { |
| AdtKind::Struct => { |
| if last { |
| err.note("the last field of a packed struct may only have a \ |
| dynamically sized type if it does not need drop to be run"); |
| } else { |
| err.note("only the last field of a struct may have a dynamically \ |
| sized type"); |
| } |
| } |
| AdtKind::Union => { |
| err.note("no field of a union may have a dynamically sized type"); |
| } |
| AdtKind::Enum => { |
| err.note("no field of an enum variant may have a dynamically sized type"); |
| } |
| } |
| } |
| ObligationCauseCode::ConstSized => { |
| err.note("constant expressions must have a statically known size"); |
| } |
| ObligationCauseCode::ConstPatternStructural => { |
| err.note("constants used for pattern-matching must derive `PartialEq` and `Eq`"); |
| } |
| ObligationCauseCode::SharedStatic => { |
| err.note("shared static variables must have a type that implements `Sync`"); |
| } |
| ObligationCauseCode::BuiltinDerivedObligation(ref data) => { |
| let parent_trait_ref = self.resolve_vars_if_possible(&data.parent_trait_ref); |
| let ty = parent_trait_ref.skip_binder().self_ty(); |
| err.note(&format!("required because it appears within the type `{}`", ty)); |
| obligated_types.push(ty); |
| |
| let parent_predicate = parent_trait_ref.to_predicate(); |
| if !self.is_recursive_obligation(obligated_types, &data.parent_code) { |
| self.note_obligation_cause_code(err, |
| &parent_predicate, |
| &data.parent_code, |
| obligated_types); |
| } |
| } |
| ObligationCauseCode::ImplDerivedObligation(ref data) => { |
| let parent_trait_ref = self.resolve_vars_if_possible(&data.parent_trait_ref); |
| err.note( |
| &format!("required because of the requirements on the impl of `{}` for `{}`", |
| parent_trait_ref.print_only_trait_path(), |
| parent_trait_ref.skip_binder().self_ty())); |
| let parent_predicate = parent_trait_ref.to_predicate(); |
| self.note_obligation_cause_code(err, |
| &parent_predicate, |
| &data.parent_code, |
| obligated_types); |
| } |
| ObligationCauseCode::CompareImplMethodObligation { .. } => { |
| err.note( |
| &format!("the requirement `{}` appears on the impl method \ |
| but not on the corresponding trait method", |
| predicate)); |
| } |
| ObligationCauseCode::ReturnType | |
| ObligationCauseCode::ReturnValue(_) | |
| ObligationCauseCode::BlockTailExpression(_) => (), |
| ObligationCauseCode::TrivialBound => { |
| err.help("see issue #48214"); |
| if tcx.sess.opts.unstable_features.is_nightly_build() { |
| err.help("add `#![feature(trivial_bounds)]` to the \ |
| crate attributes to enable", |
| ); |
| } |
| } |
| ObligationCauseCode::AssocTypeBound(ref data) => { |
| err.span_label(data.original, "associated type defined here"); |
| if let Some(sp) = data.impl_span { |
| err.span_label(sp, "in this `impl` item"); |
| } |
| for sp in &data.bounds { |
| err.span_label(*sp, "restricted in this bound"); |
| } |
| } |
| } |
| } |
| |
| fn suggest_new_overflow_limit(&self, err: &mut DiagnosticBuilder<'_>) { |
| let current_limit = self.tcx.sess.recursion_limit.get(); |
| let suggested_limit = current_limit * 2; |
| err.help(&format!("consider adding a `#![recursion_limit=\"{}\"]` attribute to your crate", |
| suggested_limit)); |
| } |
| |
| fn is_recursive_obligation(&self, |
| obligated_types: &mut Vec<&ty::TyS<'tcx>>, |
| cause_code: &ObligationCauseCode<'tcx>) -> bool { |
| if let ObligationCauseCode::BuiltinDerivedObligation(ref data) = cause_code { |
| let parent_trait_ref = self.resolve_vars_if_possible(&data.parent_trait_ref); |
| |
| if obligated_types.iter().any(|ot| ot == &parent_trait_ref.skip_binder().self_ty()) { |
| return true; |
| } |
| } |
| false |
| } |
| } |
| |
| /// Summarizes information |
| #[derive(Clone)] |
| pub enum ArgKind { |
| /// An argument of non-tuple type. Parameters are (name, ty) |
| Arg(String, String), |
| |
| /// An argument of tuple type. For a "found" argument, the span is |
| /// the locationo in the source of the pattern. For a "expected" |
| /// argument, it will be None. The vector is a list of (name, ty) |
| /// strings for the components of the tuple. |
| Tuple(Option<Span>, Vec<(String, String)>), |
| } |
| |
| impl ArgKind { |
| fn empty() -> ArgKind { |
| ArgKind::Arg("_".to_owned(), "_".to_owned()) |
| } |
| |
| /// Creates an `ArgKind` from the expected type of an |
| /// argument. It has no name (`_`) and an optional source span. |
| pub fn from_expected_ty(t: Ty<'_>, span: Option<Span>) -> ArgKind { |
| match t.kind { |
| ty::Tuple(ref tys) => ArgKind::Tuple( |
| span, |
| tys.iter() |
| .map(|ty| ("_".to_owned(), ty.to_string())) |
| .collect::<Vec<_>>() |
| ), |
| _ => ArgKind::Arg("_".to_owned(), t.to_string()), |
| } |
| } |
| } |
| |
| /// Suggest restricting a type param with a new bound. |
| pub fn suggest_constraining_type_param( |
| generics: &hir::Generics, |
| err: &mut DiagnosticBuilder<'_>, |
| param_name: &str, |
| constraint: &str, |
| source_map: &SourceMap, |
| span: Span, |
| ) -> bool { |
| let restrict_msg = "consider further restricting this bound"; |
| if let Some(param) = generics.params.iter().filter(|p| { |
| p.name.ident().as_str() == param_name |
| }).next() { |
| if param_name.starts_with("impl ") { |
| // `impl Trait` in argument: |
| // `fn foo(x: impl Trait) {}` → `fn foo(t: impl Trait + Trait2) {}` |
| err.span_suggestion( |
| param.span, |
| restrict_msg, |
| // `impl CurrentTrait + MissingTrait` |
| format!("{} + {}", param_name, constraint), |
| Applicability::MachineApplicable, |
| ); |
| } else if generics.where_clause.predicates.is_empty() && |
| param.bounds.is_empty() |
| { |
| // If there are no bounds whatsoever, suggest adding a constraint |
| // to the type parameter: |
| // `fn foo<T>(t: T) {}` → `fn foo<T: Trait>(t: T) {}` |
| err.span_suggestion( |
| param.span, |
| "consider restricting this bound", |
| format!("{}: {}", param_name, constraint), |
| Applicability::MachineApplicable, |
| ); |
| } else if !generics.where_clause.predicates.is_empty() { |
| // There is a `where` clause, so suggest expanding it: |
| // `fn foo<T>(t: T) where T: Debug {}` → |
| // `fn foo<T>(t: T) where T: Debug, T: Trait {}` |
| err.span_suggestion( |
| generics.where_clause.span().unwrap().shrink_to_hi(), |
| &format!("consider further restricting type parameter `{}`", param_name), |
| format!(", {}: {}", param_name, constraint), |
| Applicability::MachineApplicable, |
| ); |
| } else { |
| // If there is no `where` clause lean towards constraining to the |
| // type parameter: |
| // `fn foo<X: Bar, T>(t: T, x: X) {}` → `fn foo<T: Trait>(t: T) {}` |
| // `fn foo<T: Bar>(t: T) {}` → `fn foo<T: Bar + Trait>(t: T) {}` |
| let sp = param.span.with_hi(span.hi()); |
| let span = source_map.span_through_char(sp, ':'); |
| if sp != param.span && sp != span { |
| // Only suggest if we have high certainty that the span |
| // covers the colon in `foo<T: Trait>`. |
| err.span_suggestion( |
| span, |
| restrict_msg, |
| format!("{}: {} + ", param_name, constraint), |
| Applicability::MachineApplicable, |
| ); |
| } else { |
| err.span_label( |
| param.span, |
| &format!("consider adding a `where {}: {}` bound", param_name, constraint), |
| ); |
| } |
| } |
| return true; |
| } |
| false |
| } |
