1 // Copyright 2014 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
14 MismatchedProjectionTypes,
18 OnUnimplementedDirective,
20 OutputTypeParameterMismatch,
27 ObjectSafetyViolation,
30 use errors::DiagnosticBuilder;
32 use hir::def_id::DefId;
33 use infer::{self, InferCtxt};
34 use infer::type_variable::TypeVariableOrigin;
35 use middle::const_val;
38 use session::DiagnosticMessageId;
39 use ty::{self, AdtKind, ToPredicate, ToPolyTraitRef, Ty, TyCtxt, TypeFoldable};
40 use ty::error::ExpectedFound;
42 use ty::fold::TypeFolder;
44 use ty::SubtypePredicate;
45 use util::nodemap::{FxHashMap, FxHashSet};
47 use syntax_pos::{DUMMY_SP, Span};
49 impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
50 pub fn report_fulfillment_errors(&self,
51 errors: &Vec<FulfillmentError<'tcx>>,
52 body_id: Option<hir::BodyId>) {
54 struct ErrorDescriptor<'tcx> {
55 predicate: ty::Predicate<'tcx>,
56 index: Option<usize>, // None if this is an old error
59 let mut error_map : FxHashMap<_, _> =
60 self.reported_trait_errors.borrow().iter().map(|(&span, predicates)| {
61 (span, predicates.iter().map(|predicate| ErrorDescriptor {
62 predicate: predicate.clone(),
67 for (index, error) in errors.iter().enumerate() {
68 error_map.entry(error.obligation.cause.span).or_insert(Vec::new()).push(
70 predicate: error.obligation.predicate.clone(),
74 self.reported_trait_errors.borrow_mut()
75 .entry(error.obligation.cause.span).or_insert(Vec::new())
76 .push(error.obligation.predicate.clone());
79 // We do this in 2 passes because we want to display errors in order, tho
80 // maybe it *is* better to sort errors by span or something.
81 let mut is_suppressed: Vec<bool> = errors.iter().map(|_| false).collect();
82 for (_, error_set) in error_map.iter() {
83 // We want to suppress "duplicate" errors with the same span.
84 for error in error_set {
85 if let Some(index) = error.index {
86 // Suppress errors that are either:
87 // 1) strictly implied by another error.
88 // 2) implied by an error with a smaller index.
89 for error2 in error_set {
90 if error2.index.map_or(false, |index2| is_suppressed[index2]) {
91 // Avoid errors being suppressed by already-suppressed
92 // errors, to prevent all errors from being suppressed
97 if self.error_implies(&error2.predicate, &error.predicate) &&
98 !(error2.index >= error.index &&
99 self.error_implies(&error.predicate, &error2.predicate))
101 info!("skipping {:?} (implied by {:?})", error, error2);
102 is_suppressed[index] = true;
110 for (error, suppressed) in errors.iter().zip(is_suppressed) {
112 self.report_fulfillment_error(error, body_id);
117 // returns if `cond` not occurring implies that `error` does not occur - i.e. that
118 // `error` occurring implies that `cond` occurs.
119 fn error_implies(&self,
120 cond: &ty::Predicate<'tcx>,
121 error: &ty::Predicate<'tcx>)
128 let (cond, error) = match (cond, error) {
129 (&ty::Predicate::Trait(..), &ty::Predicate::Trait(ref error))
132 // FIXME: make this work in other cases too.
137 for implication in super::elaborate_predicates(self.tcx, vec![cond.clone()]) {
138 if let ty::Predicate::Trait(implication) = implication {
139 let error = error.to_poly_trait_ref();
140 let implication = implication.to_poly_trait_ref();
141 // FIXME: I'm just not taking associated types at all here.
142 // Eventually I'll need to implement param-env-aware
143 // `Γ₁ ⊦ φ₁ => Γ₂ ⊦ φ₂` logic.
144 let param_env = ty::ParamEnv::empty(Reveal::UserFacing);
145 if let Ok(_) = self.can_sub(param_env, error, implication) {
146 debug!("error_implies: {:?} -> {:?} -> {:?}", cond, error, implication);
155 fn report_fulfillment_error(&self, error: &FulfillmentError<'tcx>,
156 body_id: Option<hir::BodyId>) {
157 debug!("report_fulfillment_errors({:?})", error);
159 FulfillmentErrorCode::CodeSelectionError(ref e) => {
160 self.report_selection_error(&error.obligation, e);
162 FulfillmentErrorCode::CodeProjectionError(ref e) => {
163 self.report_projection_error(&error.obligation, e);
165 FulfillmentErrorCode::CodeAmbiguity => {
166 self.maybe_report_ambiguity(&error.obligation, body_id);
168 FulfillmentErrorCode::CodeSubtypeError(ref expected_found, ref err) => {
169 self.report_mismatched_types(&error.obligation.cause,
170 expected_found.expected,
171 expected_found.found,
178 fn report_projection_error(&self,
179 obligation: &PredicateObligation<'tcx>,
180 error: &MismatchedProjectionTypes<'tcx>)
183 self.resolve_type_vars_if_possible(&obligation.predicate);
185 if predicate.references_error() {
191 let mut err = &error.err;
192 let mut values = None;
194 // try to find the mismatched types to report the error with.
196 // this can fail if the problem was higher-ranked, in which
197 // cause I have no idea for a good error message.
198 if let ty::Predicate::Projection(ref data) = predicate {
199 let mut selcx = SelectionContext::new(self);
200 let (data, _) = self.replace_late_bound_regions_with_fresh_var(
201 obligation.cause.span,
202 infer::LateBoundRegionConversionTime::HigherRankedType,
204 let normalized = super::normalize_projection_type(
206 obligation.param_env,
208 obligation.cause.clone(),
211 if let Err(error) = self.at(&obligation.cause, obligation.param_env)
212 .eq(normalized.value, data.ty) {
213 values = Some(infer::ValuePairs::Types(ExpectedFound {
214 expected: normalized.value,
222 let msg = format!("type mismatch resolving `{}`", predicate);
223 let error_id = (DiagnosticMessageId::ErrorId(271),
224 Some(obligation.cause.span), msg.clone());
225 let fresh = self.tcx.sess.one_time_diagnostics.borrow_mut().insert(error_id);
227 let mut diag = struct_span_err!(
228 self.tcx.sess, obligation.cause.span, E0271,
229 "type mismatch resolving `{}`", predicate
231 self.note_type_err(&mut diag, &obligation.cause, None, values, err);
232 self.note_obligation_cause(&mut diag, obligation);
238 fn fuzzy_match_tys(&self, a: Ty<'tcx>, b: Ty<'tcx>) -> bool {
239 /// returns the fuzzy category of a given type, or None
240 /// if the type can be equated to any type.
241 fn type_category<'tcx>(t: Ty<'tcx>) -> Option<u32> {
243 ty::TyBool => Some(0),
244 ty::TyChar => Some(1),
245 ty::TyStr => Some(2),
246 ty::TyInt(..) | ty::TyUint(..) | ty::TyInfer(ty::IntVar(..)) => Some(3),
247 ty::TyFloat(..) | ty::TyInfer(ty::FloatVar(..)) => Some(4),
248 ty::TyRef(..) | ty::TyRawPtr(..) => Some(5),
249 ty::TyArray(..) | ty::TySlice(..) => Some(6),
250 ty::TyFnDef(..) | ty::TyFnPtr(..) => Some(7),
251 ty::TyDynamic(..) => Some(8),
252 ty::TyClosure(..) => Some(9),
253 ty::TyTuple(..) => Some(10),
254 ty::TyProjection(..) => Some(11),
255 ty::TyParam(..) => Some(12),
256 ty::TyAnon(..) => Some(13),
257 ty::TyNever => Some(14),
258 ty::TyAdt(adt, ..) => match adt.adt_kind() {
259 AdtKind::Struct => Some(15),
260 AdtKind::Union => Some(16),
261 AdtKind::Enum => Some(17),
263 ty::TyGenerator(..) => Some(18),
264 ty::TyForeign(..) => Some(19),
265 ty::TyGeneratorWitness(..) => Some(20),
266 ty::TyInfer(..) | ty::TyError => None
270 match (type_category(a), type_category(b)) {
271 (Some(cat_a), Some(cat_b)) => match (&a.sty, &b.sty) {
272 (&ty::TyAdt(def_a, _), &ty::TyAdt(def_b, _)) => def_a == def_b,
275 // infer and error can be equated to all types
280 fn impl_similar_to(&self,
281 trait_ref: ty::PolyTraitRef<'tcx>,
282 obligation: &PredicateObligation<'tcx>)
286 let param_env = obligation.param_env;
287 let trait_ref = tcx.erase_late_bound_regions(&trait_ref);
288 let trait_self_ty = trait_ref.self_ty();
290 let mut self_match_impls = vec![];
291 let mut fuzzy_match_impls = vec![];
293 self.tcx.for_each_relevant_impl(
294 trait_ref.def_id, trait_self_ty, |def_id| {
295 let impl_substs = self.fresh_substs_for_item(param_env.universe,
296 obligation.cause.span,
298 let impl_trait_ref = tcx
299 .impl_trait_ref(def_id)
301 .subst(tcx, impl_substs);
303 let impl_self_ty = impl_trait_ref.self_ty();
305 if let Ok(..) = self.can_eq(param_env, trait_self_ty, impl_self_ty) {
306 self_match_impls.push(def_id);
308 if trait_ref.substs.types().skip(1)
309 .zip(impl_trait_ref.substs.types().skip(1))
310 .all(|(u,v)| self.fuzzy_match_tys(u, v))
312 fuzzy_match_impls.push(def_id);
317 let impl_def_id = if self_match_impls.len() == 1 {
319 } else if fuzzy_match_impls.len() == 1 {
325 if tcx.has_attr(impl_def_id, "rustc_on_unimplemented") {
332 fn on_unimplemented_note(
334 trait_ref: ty::PolyTraitRef<'tcx>,
335 obligation: &PredicateObligation<'tcx>) ->
338 let def_id = self.impl_similar_to(trait_ref, obligation)
339 .unwrap_or(trait_ref.def_id());
340 let trait_ref = *trait_ref.skip_binder();
344 let mut flags = vec![];
345 let direct = match obligation.cause.code {
346 ObligationCauseCode::BuiltinDerivedObligation(..) |
347 ObligationCauseCode::ImplDerivedObligation(..) => false,
351 // this is a "direct", user-specified, rather than derived,
353 flags.push(("direct".to_string(), None));
356 if let ObligationCauseCode::ItemObligation(item) = obligation.cause.code {
357 // FIXME: maybe also have some way of handling methods
358 // from other traits? That would require name resolution,
359 // which we might want to be some sort of hygienic.
361 // Currently I'm leaving it for what I need for `try`.
362 if self.tcx.trait_of_item(item) == Some(trait_ref.def_id) {
363 method = self.tcx.item_name(item);
364 flags.push(("from_method".to_string(), None));
365 flags.push(("from_method".to_string(), Some(method.to_string())));
369 if let Some(k) = obligation.cause.span.compiler_desugaring_kind() {
370 desugaring = k.as_symbol().as_str();
371 flags.push(("from_desugaring".to_string(), None));
372 flags.push(("from_desugaring".to_string(), Some(desugaring.to_string())));
374 let generics = self.tcx.generics_of(def_id);
375 let self_ty = trait_ref.self_ty();
376 let self_ty_str = self_ty.to_string();
377 flags.push(("_Self".to_string(), Some(self_ty_str.clone())));
379 for param in generics.types.iter() {
380 let name = param.name.as_str().to_string();
381 let ty = trait_ref.substs.type_for_def(param);
382 let ty_str = ty.to_string();
383 flags.push((name.clone(),
384 Some(ty_str.clone())));
387 if let Some(true) = self_ty.ty_to_def_id().map(|def_id| def_id.is_local()) {
388 flags.push(("crate_local".to_string(), None));
391 if let Ok(Some(command)) = OnUnimplementedDirective::of_item(
392 self.tcx, trait_ref.def_id, def_id
394 command.evaluate(self.tcx, trait_ref, &flags[..])
396 OnUnimplementedNote::empty()
400 fn find_similar_impl_candidates(&self,
401 trait_ref: ty::PolyTraitRef<'tcx>)
402 -> Vec<ty::TraitRef<'tcx>>
404 let simp = fast_reject::simplify_type(self.tcx,
405 trait_ref.skip_binder().self_ty(),
407 let mut impl_candidates = Vec::new();
410 Some(simp) => self.tcx.for_each_impl(trait_ref.def_id(), |def_id| {
411 let imp = self.tcx.impl_trait_ref(def_id).unwrap();
412 let imp_simp = fast_reject::simplify_type(self.tcx,
415 if let Some(imp_simp) = imp_simp {
416 if simp != imp_simp {
420 impl_candidates.push(imp);
422 None => self.tcx.for_each_impl(trait_ref.def_id(), |def_id| {
423 impl_candidates.push(
424 self.tcx.impl_trait_ref(def_id).unwrap());
430 fn report_similar_impl_candidates(&self,
431 impl_candidates: Vec<ty::TraitRef<'tcx>>,
432 err: &mut DiagnosticBuilder)
434 if impl_candidates.is_empty() {
438 let end = if impl_candidates.len() <= 5 {
439 impl_candidates.len()
443 err.help(&format!("the following implementations were found:{}{}",
444 &impl_candidates[0..end].iter().map(|candidate| {
445 format!("\n {:?}", candidate)
446 }).collect::<String>(),
447 if impl_candidates.len() > 5 {
448 format!("\nand {} others", impl_candidates.len() - 4)
455 /// Reports that an overflow has occurred and halts compilation. We
456 /// halt compilation unconditionally because it is important that
457 /// overflows never be masked -- they basically represent computations
458 /// whose result could not be truly determined and thus we can't say
459 /// if the program type checks or not -- and they are unusual
460 /// occurrences in any case.
461 pub fn report_overflow_error<T>(&self,
462 obligation: &Obligation<'tcx, T>,
463 suggest_increasing_limit: bool) -> !
464 where T: fmt::Display + TypeFoldable<'tcx>
467 self.resolve_type_vars_if_possible(&obligation.predicate);
468 let mut err = struct_span_err!(self.tcx.sess, obligation.cause.span, E0275,
469 "overflow evaluating the requirement `{}`",
472 if suggest_increasing_limit {
473 self.suggest_new_overflow_limit(&mut err);
476 self.note_obligation_cause(&mut err, obligation);
479 self.tcx.sess.abort_if_errors();
483 /// Reports that a cycle was detected which led to overflow and halts
484 /// compilation. This is equivalent to `report_overflow_error` except
485 /// that we can give a more helpful error message (and, in particular,
486 /// we do not suggest increasing the overflow limit, which is not
488 pub fn report_overflow_error_cycle(&self, cycle: &[PredicateObligation<'tcx>]) -> ! {
489 let cycle = self.resolve_type_vars_if_possible(&cycle.to_owned());
490 assert!(cycle.len() > 0);
492 debug!("report_overflow_error_cycle: cycle={:?}", cycle);
494 self.report_overflow_error(&cycle[0], false);
497 pub fn report_extra_impl_obligation(&self,
499 item_name: ast::Name,
500 _impl_item_def_id: DefId,
501 trait_item_def_id: DefId,
502 requirement: &fmt::Display)
503 -> DiagnosticBuilder<'tcx>
505 let msg = "impl has stricter requirements than trait";
506 let sp = self.tcx.sess.codemap().def_span(error_span);
508 let mut err = struct_span_err!(self.tcx.sess, sp, E0276, "{}", msg);
510 if let Some(trait_item_span) = self.tcx.hir.span_if_local(trait_item_def_id) {
511 let span = self.tcx.sess.codemap().def_span(trait_item_span);
512 err.span_label(span, format!("definition of `{}` from trait", item_name));
515 err.span_label(sp, format!("impl has extra requirement {}", requirement));
521 /// Get the parent trait chain start
522 fn get_parent_trait_ref(&self, code: &ObligationCauseCode<'tcx>) -> Option<String> {
524 &ObligationCauseCode::BuiltinDerivedObligation(ref data) => {
525 let parent_trait_ref = self.resolve_type_vars_if_possible(
526 &data.parent_trait_ref);
527 match self.get_parent_trait_ref(&data.parent_code) {
529 None => Some(format!("{}", parent_trait_ref.0.self_ty())),
536 pub fn report_selection_error(&self,
537 obligation: &PredicateObligation<'tcx>,
538 error: &SelectionError<'tcx>)
540 let span = obligation.cause.span;
542 let mut err = match *error {
543 SelectionError::Unimplemented => {
544 if let ObligationCauseCode::CompareImplMethodObligation {
545 item_name, impl_item_def_id, trait_item_def_id,
546 } = obligation.cause.code {
547 self.report_extra_impl_obligation(
552 &format!("`{}`", obligation.predicate))
556 match obligation.predicate {
557 ty::Predicate::Trait(ref trait_predicate) => {
558 let trait_predicate =
559 self.resolve_type_vars_if_possible(trait_predicate);
561 if self.tcx.sess.has_errors() && trait_predicate.references_error() {
564 let trait_ref = trait_predicate.to_poly_trait_ref();
565 let (post_message, pre_message) =
566 self.get_parent_trait_ref(&obligation.cause.code)
567 .map(|t| (format!(" in `{}`", t), format!("within `{}`, ", t)))
568 .unwrap_or((String::new(), String::new()));
570 let OnUnimplementedNote { message, label, note }
571 = self.on_unimplemented_note(trait_ref, obligation);
572 let have_alt_message = message.is_some() || label.is_some();
574 let mut err = struct_span_err!(
579 message.unwrap_or_else(|| {
580 format!("the trait bound `{}` is not satisfied{}",
581 trait_ref.to_predicate(), post_message)
584 if let Some(ref s) = label {
585 // If it has a custom "#[rustc_on_unimplemented]"
586 // error message, let's display it as the label!
587 err.span_label(span, s.as_str());
588 err.help(&format!("{}the trait `{}` is not implemented for `{}`",
591 trait_ref.self_ty()));
594 &*format!("{}the trait `{}` is not implemented for `{}`",
597 trait_ref.self_ty()));
599 if let Some(ref s) = note {
600 // If it has a custom "#[rustc_on_unimplemented]" note, let's display it
601 err.note(s.as_str());
604 self.suggest_borrow_on_unsized_slice(&obligation.cause.code, &mut err);
606 // Try to report a help message
607 if !trait_ref.has_infer_types() &&
608 self.predicate_can_apply(obligation.param_env, trait_ref) {
609 // If a where-clause may be useful, remind the
610 // user that they can add it.
612 // don't display an on-unimplemented note, as
613 // these notes will often be of the form
614 // "the type `T` can't be frobnicated"
615 // which is somewhat confusing.
616 err.help(&format!("consider adding a `where {}` bound",
617 trait_ref.to_predicate()));
618 } else if !have_alt_message {
619 // Can't show anything else useful, try to find similar impls.
620 let impl_candidates = self.find_similar_impl_candidates(trait_ref);
621 self.report_similar_impl_candidates(impl_candidates, &mut err);
627 ty::Predicate::Subtype(ref predicate) => {
628 // Errors for Subtype predicates show up as
629 // `FulfillmentErrorCode::CodeSubtypeError`,
630 // not selection error.
631 span_bug!(span, "subtype requirement gave wrong error: `{:?}`", predicate)
634 ty::Predicate::Equate(ref predicate) => {
635 let predicate = self.resolve_type_vars_if_possible(predicate);
636 let err = self.equality_predicate(&obligation.cause,
637 obligation.param_env,
638 &predicate).err().unwrap();
639 struct_span_err!(self.tcx.sess, span, E0278,
640 "the requirement `{}` is not satisfied (`{}`)",
644 ty::Predicate::RegionOutlives(ref predicate) => {
645 let predicate = self.resolve_type_vars_if_possible(predicate);
646 let err = self.region_outlives_predicate(&obligation.cause,
647 &predicate).err().unwrap();
648 struct_span_err!(self.tcx.sess, span, E0279,
649 "the requirement `{}` is not satisfied (`{}`)",
653 ty::Predicate::Projection(..) | ty::Predicate::TypeOutlives(..) => {
655 self.resolve_type_vars_if_possible(&obligation.predicate);
656 struct_span_err!(self.tcx.sess, span, E0280,
657 "the requirement `{}` is not satisfied",
661 ty::Predicate::ObjectSafe(trait_def_id) => {
662 let violations = self.tcx.object_safety_violations(trait_def_id);
663 self.tcx.report_object_safety_error(span,
668 ty::Predicate::ClosureKind(closure_def_id, closure_substs, kind) => {
669 let found_kind = self.closure_kind(closure_def_id, closure_substs).unwrap();
670 let closure_span = self.tcx.sess.codemap()
671 .def_span(self.tcx.hir.span_if_local(closure_def_id).unwrap());
672 let node_id = self.tcx.hir.as_local_node_id(closure_def_id).unwrap();
673 let mut err = struct_span_err!(
674 self.tcx.sess, closure_span, E0525,
675 "expected a closure that implements the `{}` trait, \
676 but this closure only implements `{}`",
682 format!("this closure implements `{}`, not `{}`", found_kind, kind));
684 obligation.cause.span,
685 format!("the requirement to implement `{}` derives from here", kind));
687 // Additional context information explaining why the closure only implements
688 // a particular trait.
689 if let Some(tables) = self.in_progress_tables {
690 let tables = tables.borrow();
691 let closure_hir_id = self.tcx.hir.node_to_hir_id(node_id);
692 match (found_kind, tables.closure_kind_origins().get(closure_hir_id)) {
693 (ty::ClosureKind::FnOnce, Some((span, name))) => {
694 err.span_label(*span, format!(
695 "closure is `FnOnce` because it moves the \
696 variable `{}` out of its environment", name));
698 (ty::ClosureKind::FnMut, Some((span, name))) => {
699 err.span_label(*span, format!(
700 "closure is `FnMut` because it mutates the \
701 variable `{}` here", name));
711 ty::Predicate::WellFormed(ty) => {
712 // WF predicates cannot themselves make
713 // errors. They can only block due to
714 // ambiguity; otherwise, they always
715 // degenerate into other obligations
717 span_bug!(span, "WF predicate not satisfied for {:?}", ty);
720 ty::Predicate::ConstEvaluatable(..) => {
721 // Errors for `ConstEvaluatable` predicates show up as
722 // `SelectionError::ConstEvalFailure`,
723 // not `Unimplemented`.
725 "const-evaluatable requirement gave wrong error: `{:?}`", obligation)
730 OutputTypeParameterMismatch(ref found_trait_ref, ref expected_trait_ref, _) => {
731 let found_trait_ref = self.resolve_type_vars_if_possible(&*found_trait_ref);
732 let expected_trait_ref = self.resolve_type_vars_if_possible(&*expected_trait_ref);
733 if expected_trait_ref.self_ty().references_error() {
736 let found_trait_ty = found_trait_ref.self_ty();
738 let found_did = found_trait_ty.ty_to_def_id();
739 let found_span = found_did.and_then(|did| {
740 self.tcx.hir.span_if_local(did)
741 }).map(|sp| self.tcx.sess.codemap().def_span(sp)); // the sp could be an fn def
743 let found = match found_trait_ref.skip_binder().substs.type_at(1).sty {
744 ty::TyTuple(ref tys, _) => tys.iter()
745 .map(|_| ArgKind::empty()).collect::<Vec<_>>(),
746 _ => vec![ArgKind::empty()],
748 let expected = match expected_trait_ref.skip_binder().substs.type_at(1).sty {
749 ty::TyTuple(ref tys, _) => tys.iter()
750 .map(|t| match t.sty {
751 ty::TypeVariants::TyTuple(ref tys, _) => ArgKind::Tuple(
754 .map(|ty| ("_".to_owned(), format!("{}", ty.sty)))
757 _ => ArgKind::Arg("_".to_owned(), format!("{}", t.sty)),
759 ref sty => vec![ArgKind::Arg("_".to_owned(), format!("{}", sty))],
761 if found.len() == expected.len() {
762 self.report_closure_arg_mismatch(span,
767 let (closure_span, found) = found_did
768 .and_then(|did| self.tcx.hir.get_if_local(did))
770 let (found_span, found) = self.get_fn_like_arguments(node);
771 (Some(found_span), found)
772 }).unwrap_or((found_span, found));
774 self.report_arg_count_mismatch(span,
778 found_trait_ty.is_closure())
782 TraitNotObjectSafe(did) => {
783 let violations = self.tcx.object_safety_violations(did);
784 self.tcx.report_object_safety_error(span, did,
788 ConstEvalFailure(ref err) => {
789 if let const_val::ErrKind::TypeckError = err.kind {
792 err.struct_error(self.tcx, span, "constant expression")
795 self.note_obligation_cause(&mut err, obligation);
799 /// When encountering an assignment of an unsized trait, like `let x = ""[..];`, provide a
800 /// suggestion to borrow the initializer in order to use have a slice instead.
801 fn suggest_borrow_on_unsized_slice(&self,
802 code: &ObligationCauseCode<'tcx>,
803 err: &mut DiagnosticBuilder<'tcx>) {
804 if let &ObligationCauseCode::VariableType(node_id) = code {
805 let parent_node = self.tcx.hir.get_parent_node(node_id);
806 if let Some(hir::map::NodeLocal(ref local)) = self.tcx.hir.find(parent_node) {
807 if let Some(ref expr) = local.init {
808 if let hir::ExprIndex(_, _) = expr.node {
809 if let Ok(snippet) = self.tcx.sess.codemap().span_to_snippet(expr.span) {
810 err.span_suggestion(expr.span,
811 "consider borrowing here",
812 format!("&{}", snippet));
820 /// Given some node representing a fn-like thing in the HIR map,
821 /// returns a span and `ArgKind` information that describes the
822 /// arguments it expects. This can be supplied to
823 /// `report_arg_count_mismatch`.
824 pub fn get_fn_like_arguments(&self, node: hir::map::Node) -> (Span, Vec<ArgKind>) {
826 hir::map::NodeExpr(&hir::Expr {
827 node: hir::ExprClosure(_, ref _decl, id, span, _),
830 (self.tcx.sess.codemap().def_span(span), self.tcx.hir.body(id).arguments.iter()
833 node: hir::PatKind::Tuple(args, _),
836 } = arg.pat.clone().into_inner() {
839 args.iter().map(|pat| {
840 let snippet = self.tcx.sess.codemap()
841 .span_to_snippet(pat.span).unwrap();
842 (snippet, "_".to_owned())
843 }).collect::<Vec<_>>(),
846 let name = self.tcx.sess.codemap()
847 .span_to_snippet(arg.pat.span).unwrap();
848 ArgKind::Arg(name, "_".to_owned())
851 .collect::<Vec<ArgKind>>())
853 hir::map::NodeItem(&hir::Item {
855 node: hir::ItemFn(ref decl, ..),
858 hir::map::NodeImplItem(&hir::ImplItem {
860 node: hir::ImplItemKind::Method(hir::MethodSig { ref decl, .. }, _),
863 hir::map::NodeTraitItem(&hir::TraitItem {
865 node: hir::TraitItemKind::Method(hir::MethodSig { ref decl, .. }, _),
868 (self.tcx.sess.codemap().def_span(span), decl.inputs.iter()
869 .map(|arg| match arg.clone().into_inner().node {
870 hir::TyTup(ref tys) => ArgKind::Tuple(
873 .map(|_| ("_".to_owned(), "_".to_owned()))
874 .collect::<Vec<_>>(),
876 _ => ArgKind::Arg("_".to_owned(), "_".to_owned())
877 }).collect::<Vec<ArgKind>>())
879 hir::map::NodeVariant(&hir::Variant {
881 node: hir::Variant_ {
882 data: hir::VariantData::Tuple(ref fields, _),
887 (self.tcx.sess.codemap().def_span(span),
888 fields.iter().map(|field| {
889 ArgKind::Arg(format!("{}", field.name), "_".to_string())
890 }).collect::<Vec<_>>())
892 _ => panic!("non-FnLike node found: {:?}", node),
896 /// Reports an error when the number of arguments needed by a
897 /// trait match doesn't match the number that the expression
899 pub fn report_arg_count_mismatch(
902 found_span: Option<Span>,
903 expected_args: Vec<ArgKind>,
904 found_args: Vec<ArgKind>,
906 ) -> DiagnosticBuilder<'tcx> {
907 let kind = if is_closure { "closure" } else { "function" };
909 let args_str = |arguments: &Vec<ArgKind>, other: &Vec<ArgKind>| {
910 let arg_length = arguments.len();
911 let distinct = match &other[..] {
912 &[ArgKind::Tuple(..)] => true,
915 match (arg_length, arguments.get(0)) {
916 (1, Some(&ArgKind::Tuple(_, ref fields))) => {
917 format!("a single {}-tuple as argument", fields.len())
919 _ => format!("{} {}argument{}",
921 if distinct && arg_length > 1 { "distinct " } else { "" },
922 if arg_length == 1 { "" } else { "s" }),
926 let expected_str = args_str(&expected_args, &found_args);
927 let found_str = args_str(&found_args, &expected_args);
929 let mut err = struct_span_err!(
933 "{} is expected to take {}, but it takes {}",
939 err.span_label(span, format!( "expected {} that takes {}", kind, expected_str));
941 if let Some(found_span) = found_span {
942 err.span_label(found_span, format!("takes {}", found_str));
944 if let &[ArgKind::Tuple(_, ref fields)] = &found_args[..] {
945 if fields.len() == expected_args.len() {
946 let sugg = fields.iter()
947 .map(|(name, _)| name.to_owned())
948 .collect::<Vec<String>>().join(", ");
949 err.span_suggestion(found_span,
950 "change the closure to take multiple arguments instead of \
952 format!("|{}|", sugg));
955 if let &[ArgKind::Tuple(_, ref fields)] = &expected_args[..] {
956 if fields.len() == found_args.len() && is_closure {
960 .map(|arg| match arg {
961 ArgKind::Arg(name, _) => name.to_owned(),
964 .collect::<Vec<String>>()
966 // add type annotations if available
967 if found_args.iter().any(|arg| match arg {
968 ArgKind::Arg(_, ty) => ty != "_",
973 .map(|(_, ty)| ty.to_owned())
974 .collect::<Vec<String>>()
980 err.span_suggestion(found_span,
981 "change the closure to accept a tuple instead of \
982 individual arguments",
991 fn report_closure_arg_mismatch(&self,
993 found_span: Option<Span>,
994 expected_ref: ty::PolyTraitRef<'tcx>,
995 found: ty::PolyTraitRef<'tcx>)
996 -> DiagnosticBuilder<'tcx>
998 fn build_fn_sig_string<'a, 'gcx, 'tcx>(tcx: ty::TyCtxt<'a, 'gcx, 'tcx>,
999 trait_ref: &ty::TraitRef<'tcx>) -> String {
1000 let inputs = trait_ref.substs.type_at(1);
1001 let sig = if let ty::TyTuple(inputs, _) = inputs.sty {
1003 inputs.iter().map(|&x| x),
1004 tcx.mk_infer(ty::TyVar(ty::TyVid { index: 0 })),
1006 hir::Unsafety::Normal,
1007 ::syntax::abi::Abi::Rust
1011 ::std::iter::once(inputs),
1012 tcx.mk_infer(ty::TyVar(ty::TyVid { index: 0 })),
1014 hir::Unsafety::Normal,
1015 ::syntax::abi::Abi::Rust
1018 format!("{}", ty::Binder(sig))
1021 let argument_is_closure = expected_ref.skip_binder().substs.type_at(0).is_closure();
1022 let mut err = struct_span_err!(self.tcx.sess, span, E0631,
1023 "type mismatch in {} arguments",
1024 if argument_is_closure { "closure" } else { "function" });
1026 let found_str = format!(
1027 "expected signature of `{}`",
1028 build_fn_sig_string(self.tcx, found.skip_binder())
1030 err.span_label(span, found_str);
1032 let found_span = found_span.unwrap_or(span);
1033 let expected_str = format!(
1034 "found signature of `{}`",
1035 build_fn_sig_string(self.tcx, expected_ref.skip_binder())
1037 err.span_label(found_span, expected_str);
1043 impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
1044 pub fn recursive_type_with_infinite_size_error(self,
1046 -> DiagnosticBuilder<'tcx>
1048 assert!(type_def_id.is_local());
1049 let span = self.hir.span_if_local(type_def_id).unwrap();
1050 let span = self.sess.codemap().def_span(span);
1051 let mut err = struct_span_err!(self.sess, span, E0072,
1052 "recursive type `{}` has infinite size",
1053 self.item_path_str(type_def_id));
1054 err.span_label(span, "recursive type has infinite size");
1055 err.help(&format!("insert indirection (e.g., a `Box`, `Rc`, or `&`) \
1056 at some point to make `{}` representable",
1057 self.item_path_str(type_def_id)));
1061 pub fn report_object_safety_error(self,
1063 trait_def_id: DefId,
1064 violations: Vec<ObjectSafetyViolation>)
1065 -> DiagnosticBuilder<'tcx>
1067 let trait_str = self.item_path_str(trait_def_id);
1068 let span = self.sess.codemap().def_span(span);
1069 let mut err = struct_span_err!(
1070 self.sess, span, E0038,
1071 "the trait `{}` cannot be made into an object",
1073 err.span_label(span, format!("the trait `{}` cannot be made into an object", trait_str));
1075 let mut reported_violations = FxHashSet();
1076 for violation in violations {
1077 if !reported_violations.insert(violation.clone()) {
1080 err.note(&violation.error_msg());
1086 impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
1087 fn maybe_report_ambiguity(&self, obligation: &PredicateObligation<'tcx>,
1088 body_id: Option<hir::BodyId>) {
1089 // Unable to successfully determine, probably means
1090 // insufficient type information, but could mean
1091 // ambiguous impls. The latter *ought* to be a
1092 // coherence violation, so we don't report it here.
1094 let predicate = self.resolve_type_vars_if_possible(&obligation.predicate);
1095 let span = obligation.cause.span;
1097 debug!("maybe_report_ambiguity(predicate={:?}, obligation={:?})",
1101 // Ambiguity errors are often caused as fallout from earlier
1102 // errors. So just ignore them if this infcx is tainted.
1103 if self.is_tainted_by_errors() {
1108 ty::Predicate::Trait(ref data) => {
1109 let trait_ref = data.to_poly_trait_ref();
1110 let self_ty = trait_ref.self_ty();
1111 if predicate.references_error() {
1114 // Typically, this ambiguity should only happen if
1115 // there are unresolved type inference variables
1116 // (otherwise it would suggest a coherence
1117 // failure). But given #21974 that is not necessarily
1118 // the case -- we can have multiple where clauses that
1119 // are only distinguished by a region, which results
1120 // in an ambiguity even when all types are fully
1121 // known, since we don't dispatch based on region
1124 // This is kind of a hack: it frequently happens that some earlier
1125 // error prevents types from being fully inferred, and then we get
1126 // a bunch of uninteresting errors saying something like "<generic
1127 // #0> doesn't implement Sized". It may even be true that we
1128 // could just skip over all checks where the self-ty is an
1129 // inference variable, but I was afraid that there might be an
1130 // inference variable created, registered as an obligation, and
1131 // then never forced by writeback, and hence by skipping here we'd
1132 // be ignoring the fact that we don't KNOW the type works
1133 // out. Though even that would probably be harmless, given that
1134 // we're only talking about builtin traits, which are known to be
1135 // inhabited. But in any case I just threw in this check for
1136 // has_errors() to be sure that compilation isn't happening
1137 // anyway. In that case, why inundate the user.
1138 if !self.tcx.sess.has_errors() {
1140 self.tcx.lang_items().sized_trait()
1141 .map_or(false, |sized_id| sized_id == trait_ref.def_id())
1143 self.need_type_info(body_id, span, self_ty);
1145 let mut err = struct_span_err!(self.tcx.sess,
1147 "type annotations required: \
1148 cannot resolve `{}`",
1150 self.note_obligation_cause(&mut err, obligation);
1156 ty::Predicate::WellFormed(ty) => {
1157 // Same hacky approach as above to avoid deluging user
1158 // with error messages.
1159 if !ty.references_error() && !self.tcx.sess.has_errors() {
1160 self.need_type_info(body_id, span, ty);
1164 ty::Predicate::Subtype(ref data) => {
1165 if data.references_error() || self.tcx.sess.has_errors() {
1166 // no need to overload user in such cases
1168 let &SubtypePredicate { a_is_expected: _, a, b } = data.skip_binder();
1169 // both must be type variables, or the other would've been instantiated
1170 assert!(a.is_ty_var() && b.is_ty_var());
1171 self.need_type_info(body_id,
1172 obligation.cause.span,
1178 if !self.tcx.sess.has_errors() {
1179 let mut err = struct_span_err!(self.tcx.sess,
1180 obligation.cause.span, E0284,
1181 "type annotations required: \
1182 cannot resolve `{}`",
1184 self.note_obligation_cause(&mut err, obligation);
1191 /// Returns whether the trait predicate may apply for *some* assignment
1192 /// to the type parameters.
1193 fn predicate_can_apply(&self,
1194 param_env: ty::ParamEnv<'tcx>,
1195 pred: ty::PolyTraitRef<'tcx>)
1197 struct ParamToVarFolder<'a, 'gcx: 'a+'tcx, 'tcx: 'a> {
1198 infcx: &'a InferCtxt<'a, 'gcx, 'tcx>,
1199 param_env: ty::ParamEnv<'tcx>,
1200 var_map: FxHashMap<Ty<'tcx>, Ty<'tcx>>
1203 impl<'a, 'gcx, 'tcx> TypeFolder<'gcx, 'tcx> for ParamToVarFolder<'a, 'gcx, 'tcx> {
1204 fn tcx<'b>(&'b self) -> TyCtxt<'b, 'gcx, 'tcx> { self.infcx.tcx }
1206 fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> {
1207 if let ty::TyParam(ty::ParamTy {name, ..}) = ty.sty {
1208 let infcx = self.infcx;
1209 let param_env = self.param_env;
1212 .or_insert_with(|| {
1213 let origin = TypeVariableOrigin::TypeParameterDefinition(DUMMY_SP,
1215 infcx.next_ty_var(param_env.universe, origin)
1218 ty.super_fold_with(self)
1224 let mut selcx = SelectionContext::new(self);
1226 let cleaned_pred = pred.fold_with(&mut ParamToVarFolder {
1229 var_map: FxHashMap()
1232 let cleaned_pred = super::project::normalize(
1235 ObligationCause::dummy(),
1239 let obligation = Obligation::new(
1240 ObligationCause::dummy(),
1242 cleaned_pred.to_predicate()
1245 selcx.evaluate_obligation(&obligation)
1249 fn note_obligation_cause<T>(&self,
1250 err: &mut DiagnosticBuilder,
1251 obligation: &Obligation<'tcx, T>)
1252 where T: fmt::Display
1254 self.note_obligation_cause_code(err,
1255 &obligation.predicate,
1256 &obligation.cause.code,
1260 fn note_obligation_cause_code<T>(&self,
1261 err: &mut DiagnosticBuilder,
1263 cause_code: &ObligationCauseCode<'tcx>,
1264 obligated_types: &mut Vec<&ty::TyS<'tcx>>)
1265 where T: fmt::Display
1269 ObligationCauseCode::ExprAssignable |
1270 ObligationCauseCode::MatchExpressionArm { .. } |
1271 ObligationCauseCode::IfExpression |
1272 ObligationCauseCode::IfExpressionWithNoElse |
1273 ObligationCauseCode::EquatePredicate |
1274 ObligationCauseCode::MainFunctionType |
1275 ObligationCauseCode::StartFunctionType |
1276 ObligationCauseCode::IntrinsicType |
1277 ObligationCauseCode::MethodReceiver |
1278 ObligationCauseCode::ReturnNoExpression |
1279 ObligationCauseCode::MiscObligation => {
1281 ObligationCauseCode::SliceOrArrayElem => {
1282 err.note("slice and array elements must have `Sized` type");
1284 ObligationCauseCode::TupleElem => {
1285 err.note("only the last element of a tuple may have a dynamically sized type");
1287 ObligationCauseCode::ProjectionWf(data) => {
1288 err.note(&format!("required so that the projection `{}` is well-formed",
1291 ObligationCauseCode::ReferenceOutlivesReferent(ref_ty) => {
1292 err.note(&format!("required so that reference `{}` does not outlive its referent",
1295 ObligationCauseCode::ObjectTypeBound(object_ty, region) => {
1296 err.note(&format!("required so that the lifetime bound of `{}` for `{}` \
1298 region, object_ty));
1300 ObligationCauseCode::ItemObligation(item_def_id) => {
1301 let item_name = tcx.item_path_str(item_def_id);
1302 let msg = format!("required by `{}`", item_name);
1303 if let Some(sp) = tcx.hir.span_if_local(item_def_id) {
1304 let sp = tcx.sess.codemap().def_span(sp);
1305 err.span_note(sp, &msg);
1310 ObligationCauseCode::ObjectCastObligation(object_ty) => {
1311 err.note(&format!("required for the cast to the object type `{}`",
1312 self.ty_to_string(object_ty)));
1314 ObligationCauseCode::RepeatVec => {
1315 err.note("the `Copy` trait is required because the \
1316 repeated element will be copied");
1318 ObligationCauseCode::VariableType(_) => {
1319 err.note("all local variables must have a statically known size");
1321 ObligationCauseCode::SizedReturnType => {
1322 err.note("the return type of a function must have a \
1323 statically known size");
1325 ObligationCauseCode::SizedYieldType => {
1326 err.note("the yield type of a generator must have a \
1327 statically known size");
1329 ObligationCauseCode::AssignmentLhsSized => {
1330 err.note("the left-hand-side of an assignment must have a statically known size");
1332 ObligationCauseCode::TupleInitializerSized => {
1333 err.note("tuples must have a statically known size to be initialized");
1335 ObligationCauseCode::StructInitializerSized => {
1336 err.note("structs must have a statically known size to be initialized");
1338 ObligationCauseCode::FieldSized(ref item) => {
1340 AdtKind::Struct => {
1341 err.note("only the last field of a struct may have a dynamically \
1345 err.note("no field of a union may have a dynamically sized type");
1348 err.note("no field of an enum variant may have a dynamically sized type");
1352 ObligationCauseCode::ConstSized => {
1353 err.note("constant expressions must have a statically known size");
1355 ObligationCauseCode::SharedStatic => {
1356 err.note("shared static variables must have a type that implements `Sync`");
1358 ObligationCauseCode::BuiltinDerivedObligation(ref data) => {
1359 let parent_trait_ref = self.resolve_type_vars_if_possible(&data.parent_trait_ref);
1360 let ty = parent_trait_ref.0.self_ty();
1361 err.note(&format!("required because it appears within the type `{}`", ty));
1362 obligated_types.push(ty);
1364 let parent_predicate = parent_trait_ref.to_predicate();
1365 if !self.is_recursive_obligation(obligated_types, &data.parent_code) {
1366 self.note_obligation_cause_code(err,
1372 ObligationCauseCode::ImplDerivedObligation(ref data) => {
1373 let parent_trait_ref = self.resolve_type_vars_if_possible(&data.parent_trait_ref);
1375 &format!("required because of the requirements on the impl of `{}` for `{}`",
1377 parent_trait_ref.0.self_ty()));
1378 let parent_predicate = parent_trait_ref.to_predicate();
1379 self.note_obligation_cause_code(err,
1384 ObligationCauseCode::CompareImplMethodObligation { .. } => {
1386 &format!("the requirement `{}` appears on the impl method \
1387 but not on the corresponding trait method",
1390 ObligationCauseCode::ReturnType(_) |
1391 ObligationCauseCode::BlockTailExpression(_) => (),
1395 fn suggest_new_overflow_limit(&self, err: &mut DiagnosticBuilder) {
1396 let current_limit = self.tcx.sess.recursion_limit.get();
1397 let suggested_limit = current_limit * 2;
1398 err.help(&format!("consider adding a `#![recursion_limit=\"{}\"]` attribute to your crate",
1402 fn is_recursive_obligation(&self,
1403 obligated_types: &mut Vec<&ty::TyS<'tcx>>,
1404 cause_code: &ObligationCauseCode<'tcx>) -> bool {
1405 if let ObligationCauseCode::BuiltinDerivedObligation(ref data) = cause_code {
1406 let parent_trait_ref = self.resolve_type_vars_if_possible(&data.parent_trait_ref);
1407 for obligated_type in obligated_types {
1408 if obligated_type == &parent_trait_ref.0.self_ty() {
1417 /// Summarizes information
1419 /// An argument of non-tuple type. Parameters are (name, ty)
1420 Arg(String, String),
1422 /// An argument of tuple type. For a "found" argument, the span is
1423 /// the locationo in the source of the pattern. For a "expected"
1424 /// argument, it will be None. The vector is a list of (name, ty)
1425 /// strings for the components of the tuple.
1426 Tuple(Option<Span>, Vec<(String, String)>),
1430 fn empty() -> ArgKind {
1431 ArgKind::Arg("_".to_owned(), "_".to_owned())
1434 /// Creates an `ArgKind` from the expected type of an
1435 /// argument. This has no name (`_`) and no source spans..
1436 pub fn from_expected_ty(t: Ty<'_>) -> ArgKind {
1438 ty::TyTuple(ref tys, _) => ArgKind::Tuple(
1441 .map(|ty| ("_".to_owned(), format!("{}", ty.sty)))
1442 .collect::<Vec<_>>()
1444 _ => ArgKind::Arg("_".to_owned(), format!("{}", t.sty)),