diff --git a/src/librustc/traits/error_reporting/mod.rs b/src/librustc/traits/error_reporting/mod.rs new file mode 100644 index 0000000000000..f8329124851b0 --- /dev/null +++ b/src/librustc/traits/error_reporting/mod.rs @@ -0,0 +1,1442 @@ +pub mod on_unimplemented; +pub mod suggestions; + +use super::{ + ConstEvalFailure, EvaluationResult, FulfillmentError, FulfillmentErrorCode, + MismatchedProjectionTypes, ObjectSafetyViolation, Obligation, ObligationCause, + ObligationCauseCode, OnUnimplementedDirective, OnUnimplementedNote, + OutputTypeParameterMismatch, Overflow, PredicateObligation, SelectionContext, SelectionError, + TraitNotObjectSafe, +}; + +use crate::infer::error_reporting::{TyCategory, TypeAnnotationNeeded as ErrorCode}; +use crate::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind}; +use crate::infer::{self, InferCtxt}; +use crate::mir::interpret::ErrorHandled; +use crate::session::DiagnosticMessageId; +use crate::traits::object_safety_violations; +use crate::ty::error::ExpectedFound; +use crate::ty::fast_reject; +use crate::ty::fold::TypeFolder; +use crate::ty::SubtypePredicate; +use crate::ty::{self, AdtKind, ToPolyTraitRef, ToPredicate, Ty, TyCtxt, TypeFoldable}; + +use rustc_data_structures::fx::{FxHashMap, FxHashSet}; +use rustc_errors::{struct_span_err, Applicability, DiagnosticBuilder}; +use rustc_hir as hir; +use rustc_hir::def_id::{DefId, LOCAL_CRATE}; +use rustc_hir::intravisit::Visitor; +use rustc_span::source_map::SourceMap; +use rustc_span::{ExpnKind, Span, DUMMY_SP}; +use std::fmt; +use syntax::ast; + +use rustc_error_codes::*; + +impl<'a, 'tcx> InferCtxt<'a, 'tcx> { + pub fn report_fulfillment_errors( + &self, + errors: &[FulfillmentError<'tcx>], + body_id: Option, + fallback_has_occurred: bool, + ) { + #[derive(Debug)] + struct ErrorDescriptor<'tcx> { + predicate: ty::Predicate<'tcx>, + index: Option, // 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, + 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 { + 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 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", + }) + } + + fn find_similar_impl_candidates( + &self, + trait_ref: ty::PolyTraitRef<'tcx>, + ) -> Vec> { + 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>, + 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::>(); + + // 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( + &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, Option)> { + 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 => { + let ty = parent_trait_ref.skip_binder().self_ty(); + let span = + TyCategory::from_ty(ty).map(|(_, def_id)| self.tcx.def_span(def_id)); + Some((ty.to_string(), span)) + } + } + } + _ => 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, + } + | ObligationCauseCode::CompareImplTypeObligation { + 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, type_def) = self + .get_parent_trait_ref(&obligation.cause.code) + .map(|(t, s)| { + ( + format!(" in `{}`", t), + format!("within `{}`, ", t), + s.map(|s| (format!("within this `{}`", t), s)), + ) + }) + .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((msg, span)) = type_def { + err.span_label(span, &msg); + } + 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); + if self.suggest_impl_trait(&mut err, span, &obligation, &trait_ref) { + err.emit(); + return; + } + + // 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 = object_safety_violations(self.tcx, trait_def_id); + report_object_safety_error(self.tcx, 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 = object_safety_violations(self.tcx, did); + report_object_safety_error(self.tcx, span, did, violations) + } + + // already reported in the query + ConstEvalFailure(err) => { + if let ErrorHandled::TooGeneric = err { + // Silence this error, as it can be produced during intermediate steps + // when a constant is not yet able to be evaluated (but will be later). + return; + } + 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); + self.point_at_returns_when_relevant(&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 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()) + } +} + +pub fn recursive_type_with_infinite_size_error( + tcx: TyCtxt<'tcx>, + type_def_id: DefId, +) -> DiagnosticBuilder<'tcx> { + assert!(type_def_id.is_local()); + let span = tcx.hir().span_if_local(type_def_id).unwrap(); + let span = tcx.sess.source_map().def_span(span); + let mut err = struct_span_err!( + tcx.sess, + span, + E0072, + "recursive type `{}` has infinite size", + tcx.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", + tcx.def_path_str(type_def_id) + )); + err +} + +pub fn report_object_safety_error( + tcx: TyCtxt<'tcx>, + span: Span, + trait_def_id: DefId, + violations: Vec, +) -> DiagnosticBuilder<'tcx> { + let trait_str = tcx.def_path_str(trait_def_id); + let span = tcx.sess.source_map().def_span(span); + let mut err = struct_span_err!( + tcx.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 tcx.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, + ) { + // 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; + } + + let mut err = 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 " 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, ErrorCode::E0282).emit(); + return; + } + let mut err = self.need_type_info_err(body_id, span, self_ty, ErrorCode::E0283); + err.note(&format!("cannot resolve `{}`", predicate)); + if let ObligationCauseCode::ItemObligation(def_id) = obligation.cause.code { + self.suggest_fully_qualified_path(&mut err, def_id, span, trait_ref.def_id()); + } else if let ( + Ok(ref snippet), + ObligationCauseCode::BindingObligation(ref def_id, _), + ) = + (self.tcx.sess.source_map().span_to_snippet(span), &obligation.cause.code) + { + let generics = self.tcx.generics_of(*def_id); + if !generics.params.is_empty() && !snippet.ends_with('>') { + // FIXME: To avoid spurious suggestions in functions where type arguments + // where already supplied, we check the snippet to make sure it doesn't + // end with a turbofish. Ideally we would have access to a `PathSegment` + // instead. Otherwise we would produce the following output: + // + // error[E0283]: type annotations needed + // --> $DIR/issue-54954.rs:3:24 + // | + // LL | const ARR_LEN: usize = Tt::const_val::<[i8; 123]>(); + // | ^^^^^^^^^^^^^^^^^^^^^^^^^^ + // | | + // | cannot infer type + // | help: consider specifying the type argument + // | in the function call: + // | `Tt::const_val::<[i8; 123]>::` + // ... + // LL | const fn const_val() -> usize { + // | --------- - required by this bound in `Tt::const_val` + // | + // = note: cannot resolve `_: Tt` + + err.span_suggestion( + span, + &format!( + "consider specifying the type argument{} in the function call", + if generics.params.len() > 1 { "s" } else { "" }, + ), + format!( + "{}::<{}>", + snippet, + generics + .params + .iter() + .map(|p| p.name.to_string()) + .collect::>() + .join(", ") + ), + Applicability::HasPlaceholders, + ); + } + } + err + } + + 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() { + return; + } + self.need_type_info_err(body_id, span, ty, ErrorCode::E0282) + } + + ty::Predicate::Subtype(ref data) => { + if data.references_error() || self.tcx.sess.has_errors() { + // no need to overload user in such cases + return; + } + 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, span, a, ErrorCode::E0282) + } + ty::Predicate::Projection(ref data) => { + let trait_ref = data.to_poly_trait_ref(self.tcx); + let self_ty = trait_ref.self_ty(); + if predicate.references_error() { + return; + } + let mut err = self.need_type_info_err(body_id, span, self_ty, ErrorCode::E0284); + err.note(&format!("cannot resolve `{}`", predicate)); + err + } + + _ => { + if self.tcx.sess.has_errors() { + return; + } + let mut err = struct_span_err!( + self.tcx.sess, + span, + E0284, + "type annotations needed: cannot resolve `{}`", + predicate, + ); + err.span_label(span, &format!("cannot resolve `{}`", predicate)); + err + } + }; + 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>>, + } + + 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, None), + 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.maybe_note_obligation_cause_for_async_await(err, obligation) { + self.note_obligation_cause_code( + err, + &obligation.predicate, + &obligation.cause.code, + &mut vec![], + ); + } + } + + 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, 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) -> ArgKind { + match t.kind { + ty::Tuple(ref tys) => ArgKind::Tuple( + span, + tys.iter().map(|ty| ("_".to_owned(), ty.to_string())).collect::>(), + ), + _ => 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) {}` → `fn foo(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) where T: Debug {}` → + // `fn foo(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(t: T, x: X) {}` → `fn foo(t: T) {}` + // `fn foo(t: T) {}` → `fn foo(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`. + 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 +} + +struct ReturnsVisitor<'v>(Vec<&'v hir::Expr<'v>>); + +impl<'v> Visitor<'v> for ReturnsVisitor<'v> { + type Map = rustc::hir::map::Map<'v>; + + fn nested_visit_map(&mut self) -> hir::intravisit::NestedVisitorMap<'_, Self::Map> { + hir::intravisit::NestedVisitorMap::None + } + + fn visit_expr(&mut self, ex: &'v hir::Expr<'v>) { + match ex.kind { + hir::ExprKind::Ret(Some(ex)) => self.0.push(ex), + _ => {} + } + hir::intravisit::walk_expr(self, ex); + } + + fn visit_body(&mut self, body: &'v hir::Body<'v>) { + if body.generator_kind().is_none() { + if let hir::ExprKind::Block(block, None) = body.value.kind { + if let Some(expr) = block.expr { + self.0.push(expr); + } + } + } + hir::intravisit::walk_body(self, body); + } +} diff --git a/src/librustc/traits/error_reporting/on_unimplemented.rs b/src/librustc/traits/error_reporting/on_unimplemented.rs new file mode 100644 index 0000000000000..9f3fc91548b21 --- /dev/null +++ b/src/librustc/traits/error_reporting/on_unimplemented.rs @@ -0,0 +1,199 @@ +use super::{ + ObligationCauseCode, OnUnimplementedDirective, OnUnimplementedNote, PredicateObligation, +}; +use crate::infer::InferCtxt; +use crate::ty::subst::Subst; +use crate::ty::{self, GenericParamDefKind}; +use rustc_hir as hir; +use rustc_hir::def_id::DefId; +use rustc_span::symbol::sym; + +impl<'a, 'tcx> InferCtxt<'a, 'tcx> { + fn impl_similar_to( + &self, + trait_ref: ty::PolyTraitRef<'tcx>, + obligation: &PredicateObligation<'tcx>, + ) -> Option { + 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) + } + + /// 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 + } + } + + crate 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() + } + } +} diff --git a/src/librustc/traits/error_reporting.rs b/src/librustc/traits/error_reporting/suggestions.rs similarity index 52% rename from src/librustc/traits/error_reporting.rs rename to src/librustc/traits/error_reporting/suggestions.rs index 77a73aba45484..389edfa071794 100644 --- a/src/librustc/traits/error_reporting.rs +++ b/src/librustc/traits/error_reporting/suggestions.rs @@ -1,1178 +1,28 @@ -// ignore-tidy-filelength use super::{ - ConstEvalFailure, EvaluationResult, FulfillmentError, FulfillmentErrorCode, - MismatchedProjectionTypes, ObjectSafetyViolation, Obligation, ObligationCause, - ObligationCauseCode, OnUnimplementedDirective, OnUnimplementedNote, - OutputTypeParameterMismatch, Overflow, PredicateObligation, SelectionContext, SelectionError, - TraitNotObjectSafe, + ArgKind, EvaluationResult, Obligation, ObligationCause, ObligationCauseCode, + PredicateObligation, }; -use crate::infer::error_reporting::{TyCategory, TypeAnnotationNeeded as ErrorCode}; -use crate::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind}; -use crate::infer::{self, InferCtxt}; -use crate::mir::interpret::ErrorHandled; -use crate::session::DiagnosticMessageId; -use crate::traits::object_safety_violations; -use crate::ty::error::ExpectedFound; -use crate::ty::fast_reject; -use crate::ty::fold::TypeFolder; -use crate::ty::subst::Subst; -use crate::ty::GenericParamDefKind; -use crate::ty::SubtypePredicate; +use crate::infer::InferCtxt; use crate::ty::TypeckTables; -use crate::ty::{self, AdtKind, DefIdTree, ToPolyTraitRef, ToPredicate, Ty, TyCtxt, TypeFoldable}; +use crate::ty::{self, AdtKind, DefIdTree, ToPredicate, Ty, TyCtxt, TypeFoldable}; -use rustc_data_structures::fx::{FxHashMap, FxHashSet}; use rustc_errors::{ error_code, pluralize, struct_span_err, Applicability, DiagnosticBuilder, Style, }; use rustc_hir as hir; -use rustc_hir::def_id::{DefId, LOCAL_CRATE}; +use rustc_hir::def_id::DefId; use rustc_hir::intravisit::Visitor; use rustc_hir::Node; use rustc_span::source_map::SourceMap; use rustc_span::symbol::{kw, sym}; -use rustc_span::{ExpnKind, MultiSpan, Span, DUMMY_SP}; +use rustc_span::{MultiSpan, Span, DUMMY_SP}; use std::fmt; -use syntax::ast; use rustc_error_codes::*; impl<'a, 'tcx> InferCtxt<'a, 'tcx> { - pub fn report_fulfillment_errors( - &self, - errors: &[FulfillmentError<'tcx>], - body_id: Option, - fallback_has_occurred: bool, - ) { - #[derive(Debug)] - struct ErrorDescriptor<'tcx> { - predicate: ty::Predicate<'tcx>, - index: Option, // 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, - 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 { - 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 { - 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> { - 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>, - 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::>(); - - // 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( - &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, Option)> { - 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 => { - let ty = parent_trait_ref.skip_binder().self_ty(); - let span = - TyCategory::from_ty(ty).map(|(_, def_id)| self.tcx.def_span(def_id)); - Some((ty.to_string(), span)) - } - } - } - _ => 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, - } - | ObligationCauseCode::CompareImplTypeObligation { - 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, type_def) = self - .get_parent_trait_ref(&obligation.cause.code) - .map(|(t, s)| { - ( - format!(" in `{}`", t), - format!("within `{}`, ", t), - s.map(|s| (format!("within this `{}`", t), s)), - ) - }) - .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((msg, span)) = type_def { - err.span_label(span, &msg); - } - 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); - if self.suggest_impl_trait(&mut err, span, &obligation, &trait_ref) { - err.emit(); - return; - } - - // 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 = object_safety_violations(self.tcx, trait_def_id); - report_object_safety_error(self.tcx, 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 = object_safety_violations(self.tcx, did); - report_object_safety_error(self.tcx, span, did, violations) - } - - // already reported in the query - ConstEvalFailure(err) => { - if let ErrorHandled::TooGeneric = err { - // Silence this error, as it can be produced during intermediate steps - // when a constant is not yet able to be evaluated (but will be later). - return; - } - 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); - self.point_at_returns_when_relevant(&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( + crate fn suggest_restricting_param_bound( &self, mut err: &mut DiagnosticBuilder<'_>, trait_ref: &ty::PolyTraitRef<'_>, @@ -1318,7 +168,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> { /// 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( + crate fn suggest_borrow_on_unsized_slice( &self, code: &ObligationCauseCode<'tcx>, err: &mut DiagnosticBuilder<'tcx>, @@ -1342,22 +192,10 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> { } } - 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( + crate fn get_closure_name( &self, def_id: DefId, err: &mut DiagnosticBuilder<'_>, @@ -1395,7 +233,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> { /// 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( + crate fn suggest_fn_call( &self, obligation: &PredicateObligation<'tcx>, err: &mut DiagnosticBuilder<'_>, @@ -1479,7 +317,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> { } } - fn suggest_add_reference_to_arg( + crate fn suggest_add_reference_to_arg( &self, obligation: &PredicateObligation<'tcx>, err: &mut DiagnosticBuilder<'tcx>, @@ -1548,7 +386,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> { /// 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( + crate fn suggest_remove_reference( &self, obligation: &PredicateObligation<'tcx>, err: &mut DiagnosticBuilder<'tcx>, @@ -1608,7 +446,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> { /// Check if the trait bound is implemented for a different mutability and note it in the /// final error. - fn suggest_change_mut( + crate fn suggest_change_mut( &self, obligation: &PredicateObligation<'tcx>, err: &mut DiagnosticBuilder<'tcx>, @@ -1672,7 +510,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> { } } - fn suggest_semicolon_removal( + crate fn suggest_semicolon_removal( &self, obligation: &PredicateObligation<'tcx>, err: &mut DiagnosticBuilder<'tcx>, @@ -1705,7 +543,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> { } } - fn suggest_impl_trait( + crate fn suggest_impl_trait( &self, err: &mut DiagnosticBuilder<'tcx>, span: Span, @@ -1865,7 +703,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> { false } - fn point_at_returns_when_relevant( + crate fn point_at_returns_when_relevant( &self, err: &mut DiagnosticBuilder<'tcx>, obligation: &PredicateObligation<'tcx>, @@ -2110,14 +948,17 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> { err } - fn report_closure_arg_mismatch( + crate fn report_closure_arg_mismatch( &self, span: Span, found_span: Option, 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 { + crate 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( @@ -2165,238 +1006,8 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> { } } -pub fn recursive_type_with_infinite_size_error( - tcx: TyCtxt<'tcx>, - type_def_id: DefId, -) -> DiagnosticBuilder<'tcx> { - assert!(type_def_id.is_local()); - let span = tcx.hir().span_if_local(type_def_id).unwrap(); - let span = tcx.sess.source_map().def_span(span); - let mut err = struct_span_err!( - tcx.sess, - span, - E0072, - "recursive type `{}` has infinite size", - tcx.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", - tcx.def_path_str(type_def_id) - )); - err -} - -pub fn report_object_safety_error( - tcx: TyCtxt<'tcx>, - span: Span, - trait_def_id: DefId, - violations: Vec, -) -> DiagnosticBuilder<'tcx> { - let trait_str = tcx.def_path_str(trait_def_id); - let span = tcx.sess.source_map().def_span(span); - let mut err = struct_span_err!( - tcx.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 tcx.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, - ) { - // 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; - } - - let mut err = 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 " 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, ErrorCode::E0282).emit(); - return; - } - let mut err = self.need_type_info_err(body_id, span, self_ty, ErrorCode::E0283); - err.note(&format!("cannot resolve `{}`", predicate)); - if let ObligationCauseCode::ItemObligation(def_id) = obligation.cause.code { - self.suggest_fully_qualified_path(&mut err, def_id, span, trait_ref.def_id()); - } else if let ( - Ok(ref snippet), - ObligationCauseCode::BindingObligation(ref def_id, _), - ) = - (self.tcx.sess.source_map().span_to_snippet(span), &obligation.cause.code) - { - let generics = self.tcx.generics_of(*def_id); - if !generics.params.is_empty() && !snippet.ends_with('>') { - // FIXME: To avoid spurious suggestions in functions where type arguments - // where already supplied, we check the snippet to make sure it doesn't - // end with a turbofish. Ideally we would have access to a `PathSegment` - // instead. Otherwise we would produce the following output: - // - // error[E0283]: type annotations needed - // --> $DIR/issue-54954.rs:3:24 - // | - // LL | const ARR_LEN: usize = Tt::const_val::<[i8; 123]>(); - // | ^^^^^^^^^^^^^^^^^^^^^^^^^^ - // | | - // | cannot infer type - // | help: consider specifying the type argument - // | in the function call: - // | `Tt::const_val::<[i8; 123]>::` - // ... - // LL | const fn const_val() -> usize { - // | --------- - required by this bound in `Tt::const_val` - // | - // = note: cannot resolve `_: Tt` - - err.span_suggestion( - span, - &format!( - "consider specifying the type argument{} in the function call", - if generics.params.len() > 1 { "s" } else { "" }, - ), - format!( - "{}::<{}>", - snippet, - generics - .params - .iter() - .map(|p| p.name.to_string()) - .collect::>() - .join(", ") - ), - Applicability::HasPlaceholders, - ); - } - } - err - } - - 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() { - return; - } - self.need_type_info_err(body_id, span, ty, ErrorCode::E0282) - } - - ty::Predicate::Subtype(ref data) => { - if data.references_error() || self.tcx.sess.has_errors() { - // no need to overload user in such cases - return; - } - 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, span, a, ErrorCode::E0282) - } - ty::Predicate::Projection(ref data) => { - let trait_ref = data.to_poly_trait_ref(self.tcx); - let self_ty = trait_ref.self_ty(); - if predicate.references_error() { - return; - } - let mut err = self.need_type_info_err(body_id, span, self_ty, ErrorCode::E0284); - err.note(&format!("cannot resolve `{}`", predicate)); - err - } - - _ => { - if self.tcx.sess.has_errors() { - return; - } - let mut err = struct_span_err!( - self.tcx.sess, - span, - E0284, - "type annotations needed: cannot resolve `{}`", - predicate, - ); - err.span_label(span, &format!("cannot resolve `{}`", predicate)); - err - } - }; - self.note_obligation_cause(&mut err, obligation); - err.emit(); - } - - fn suggest_fully_qualified_path( + crate fn suggest_fully_qualified_path( &self, err: &mut DiagnosticBuilder<'_>, def_id: DefId, @@ -2420,76 +1031,6 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> { } } - /// 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>>, - } - - 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, None), - 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.maybe_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 when the future does not implement /// an auto trait because of a captured type. /// @@ -2532,7 +1073,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> { /// ``` /// /// Returns `true` if an async-await specific note was added to the diagnostic. - fn maybe_note_obligation_cause_for_async_await( + crate fn maybe_note_obligation_cause_for_async_await( &self, err: &mut DiagnosticBuilder<'_>, obligation: &PredicateObligation<'tcx>, @@ -2712,7 +1253,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> { /// Unconditionally adds the diagnostic note described in /// `maybe_note_obligation_cause_for_async_await`'s documentation comment. - fn note_obligation_cause_for_async_await( + crate fn note_obligation_cause_for_async_await( &self, err: &mut DiagnosticBuilder<'_>, target_span: Span, @@ -2838,7 +1379,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> { ); } - fn note_obligation_cause_code( + crate fn note_obligation_cause_code( &self, err: &mut DiagnosticBuilder<'_>, predicate: &T, @@ -3053,7 +1594,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> { } } - fn suggest_new_overflow_limit(&self, err: &mut DiagnosticBuilder<'_>) { + crate 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!( @@ -3061,52 +1602,6 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> { 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, 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) -> ArgKind { - match t.kind { - ty::Tuple(ref tys) => ArgKind::Tuple( - span, - tys.iter().map(|ty| ("_".to_owned(), ty.to_string())).collect::>(), - ), - _ => ArgKind::Arg("_".to_owned(), t.to_string()), - } - } } /// Suggest restricting a type param with a new bound.