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;
36 use rustc::lint::builtin::EXTRA_REQUIREMENT_IN_IMPL;
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 mut diag = struct_span_err!(
223 self.tcx.sess, obligation.cause.span, E0271,
224 "type mismatch resolving `{}`", predicate
226 self.note_type_err(&mut diag, &obligation.cause, None, values, err);
227 self.note_obligation_cause(&mut diag, obligation);
232 fn fuzzy_match_tys(&self, a: Ty<'tcx>, b: Ty<'tcx>) -> bool {
233 /// returns the fuzzy category of a given type, or None
234 /// if the type can be equated to any type.
235 fn type_category<'tcx>(t: Ty<'tcx>) -> Option<u32> {
237 ty::TyBool => Some(0),
238 ty::TyChar => Some(1),
239 ty::TyStr => Some(2),
240 ty::TyInt(..) | ty::TyUint(..) | ty::TyInfer(ty::IntVar(..)) => Some(3),
241 ty::TyFloat(..) | ty::TyInfer(ty::FloatVar(..)) => Some(4),
242 ty::TyRef(..) | ty::TyRawPtr(..) => Some(5),
243 ty::TyArray(..) | ty::TySlice(..) => Some(6),
244 ty::TyFnDef(..) | ty::TyFnPtr(..) => Some(7),
245 ty::TyDynamic(..) => Some(8),
246 ty::TyClosure(..) => Some(9),
247 ty::TyTuple(..) => Some(10),
248 ty::TyProjection(..) => Some(11),
249 ty::TyParam(..) => Some(12),
250 ty::TyAnon(..) => Some(13),
251 ty::TyNever => Some(14),
252 ty::TyAdt(adt, ..) => match adt.adt_kind() {
253 AdtKind::Struct => Some(15),
254 AdtKind::Union => Some(16),
255 AdtKind::Enum => Some(17),
257 ty::TyGenerator(..) => Some(18),
258 ty::TyInfer(..) | ty::TyError => None
262 match (type_category(a), type_category(b)) {
263 (Some(cat_a), Some(cat_b)) => match (&a.sty, &b.sty) {
264 (&ty::TyAdt(def_a, _), &ty::TyAdt(def_b, _)) => def_a == def_b,
267 // infer and error can be equated to all types
272 fn impl_similar_to(&self,
273 trait_ref: ty::PolyTraitRef<'tcx>,
274 obligation: &PredicateObligation<'tcx>)
278 let param_env = obligation.param_env;
279 let trait_ref = tcx.erase_late_bound_regions(&trait_ref);
280 let trait_self_ty = trait_ref.self_ty();
282 let mut self_match_impls = vec![];
283 let mut fuzzy_match_impls = vec![];
285 self.tcx.for_each_relevant_impl(
286 trait_ref.def_id, trait_self_ty, |def_id| {
287 let impl_substs = self.fresh_substs_for_item(obligation.cause.span, def_id);
288 let impl_trait_ref = tcx
289 .impl_trait_ref(def_id)
291 .subst(tcx, impl_substs);
293 let impl_self_ty = impl_trait_ref.self_ty();
295 if let Ok(..) = self.can_eq(param_env, trait_self_ty, impl_self_ty) {
296 self_match_impls.push(def_id);
298 if trait_ref.substs.types().skip(1)
299 .zip(impl_trait_ref.substs.types().skip(1))
300 .all(|(u,v)| self.fuzzy_match_tys(u, v))
302 fuzzy_match_impls.push(def_id);
307 let impl_def_id = if self_match_impls.len() == 1 {
309 } else if fuzzy_match_impls.len() == 1 {
315 if tcx.has_attr(impl_def_id, "rustc_on_unimplemented") {
322 fn on_unimplemented_note(
324 trait_ref: ty::PolyTraitRef<'tcx>,
325 obligation: &PredicateObligation<'tcx>) ->
328 let def_id = self.impl_similar_to(trait_ref, obligation)
329 .unwrap_or(trait_ref.def_id());
330 let trait_ref = *trait_ref.skip_binder();
334 let mut flags = vec![];
335 let direct = match obligation.cause.code {
336 ObligationCauseCode::BuiltinDerivedObligation(..) |
337 ObligationCauseCode::ImplDerivedObligation(..) => false,
341 // this is a "direct", user-specified, rather than derived,
343 flags.push(("direct", None));
346 if let ObligationCauseCode::ItemObligation(item) = obligation.cause.code {
347 // FIXME: maybe also have some way of handling methods
348 // from other traits? That would require name resolution,
349 // which we might want to be some sort of hygienic.
351 // Currently I'm leaving it for what I need for `try`.
352 if self.tcx.trait_of_item(item) == Some(trait_ref.def_id) {
353 method = self.tcx.item_name(item);
354 flags.push(("from_method", None));
355 flags.push(("from_method", Some(&*method)));
359 if let Some(k) = obligation.cause.span.compiler_desugaring_kind() {
360 desugaring = k.as_symbol().as_str();
361 flags.push(("from_desugaring", None));
362 flags.push(("from_desugaring", Some(&*desugaring)));
365 if let Ok(Some(command)) = OnUnimplementedDirective::of_item(
366 self.tcx, trait_ref.def_id, def_id
368 command.evaluate(self.tcx, trait_ref, &flags)
370 OnUnimplementedNote::empty()
374 fn find_similar_impl_candidates(&self,
375 trait_ref: ty::PolyTraitRef<'tcx>)
376 -> Vec<ty::TraitRef<'tcx>>
378 let simp = fast_reject::simplify_type(self.tcx,
379 trait_ref.skip_binder().self_ty(),
381 let mut impl_candidates = Vec::new();
384 Some(simp) => self.tcx.for_each_impl(trait_ref.def_id(), |def_id| {
385 let imp = self.tcx.impl_trait_ref(def_id).unwrap();
386 let imp_simp = fast_reject::simplify_type(self.tcx,
389 if let Some(imp_simp) = imp_simp {
390 if simp != imp_simp {
394 impl_candidates.push(imp);
396 None => self.tcx.for_each_impl(trait_ref.def_id(), |def_id| {
397 impl_candidates.push(
398 self.tcx.impl_trait_ref(def_id).unwrap());
404 fn report_similar_impl_candidates(&self,
405 impl_candidates: Vec<ty::TraitRef<'tcx>>,
406 err: &mut DiagnosticBuilder)
408 if impl_candidates.is_empty() {
412 let end = if impl_candidates.len() <= 5 {
413 impl_candidates.len()
417 err.help(&format!("the following implementations were found:{}{}",
418 &impl_candidates[0..end].iter().map(|candidate| {
419 format!("\n {:?}", candidate)
420 }).collect::<String>(),
421 if impl_candidates.len() > 5 {
422 format!("\nand {} others", impl_candidates.len() - 4)
429 /// Reports that an overflow has occurred and halts compilation. We
430 /// halt compilation unconditionally because it is important that
431 /// overflows never be masked -- they basically represent computations
432 /// whose result could not be truly determined and thus we can't say
433 /// if the program type checks or not -- and they are unusual
434 /// occurrences in any case.
435 pub fn report_overflow_error<T>(&self,
436 obligation: &Obligation<'tcx, T>,
437 suggest_increasing_limit: bool) -> !
438 where T: fmt::Display + TypeFoldable<'tcx>
441 self.resolve_type_vars_if_possible(&obligation.predicate);
442 let mut err = struct_span_err!(self.tcx.sess, obligation.cause.span, E0275,
443 "overflow evaluating the requirement `{}`",
446 if suggest_increasing_limit {
447 self.suggest_new_overflow_limit(&mut err);
450 self.note_obligation_cause(&mut err, obligation);
453 self.tcx.sess.abort_if_errors();
457 /// Reports that a cycle was detected which led to overflow and halts
458 /// compilation. This is equivalent to `report_overflow_error` except
459 /// that we can give a more helpful error message (and, in particular,
460 /// we do not suggest increasing the overflow limit, which is not
462 pub fn report_overflow_error_cycle(&self, cycle: &[PredicateObligation<'tcx>]) -> ! {
463 let cycle = self.resolve_type_vars_if_possible(&cycle.to_owned());
464 assert!(cycle.len() > 0);
466 debug!("report_overflow_error_cycle: cycle={:?}", cycle);
468 self.report_overflow_error(&cycle[0], false);
471 pub fn report_extra_impl_obligation(&self,
473 item_name: ast::Name,
474 _impl_item_def_id: DefId,
475 trait_item_def_id: DefId,
476 requirement: &fmt::Display,
477 lint_id: Option<ast::NodeId>) // (*)
478 -> DiagnosticBuilder<'tcx>
480 // (*) This parameter is temporary and used only for phasing
481 // in the bug fix to #18937. If it is `Some`, it has a kind of
482 // weird effect -- the diagnostic is reported as a lint, and
483 // the builder which is returned is marked as canceled.
485 let msg = "impl has stricter requirements than trait";
486 let mut err = match lint_id {
488 self.tcx.struct_span_lint_node(EXTRA_REQUIREMENT_IN_IMPL,
494 struct_span_err!(self.tcx.sess,
501 if let Some(trait_item_span) = self.tcx.hir.span_if_local(trait_item_def_id) {
502 let span = self.tcx.sess.codemap().def_span(trait_item_span);
503 err.span_label(span, format!("definition of `{}` from trait", item_name));
508 format!("impl has extra requirement {}", requirement));
514 /// Get the parent trait chain start
515 fn get_parent_trait_ref(&self, code: &ObligationCauseCode<'tcx>) -> Option<String> {
517 &ObligationCauseCode::BuiltinDerivedObligation(ref data) => {
518 let parent_trait_ref = self.resolve_type_vars_if_possible(
519 &data.parent_trait_ref);
520 match self.get_parent_trait_ref(&data.parent_code) {
522 None => Some(format!("{}", parent_trait_ref.0.self_ty())),
529 pub fn report_selection_error(&self,
530 obligation: &PredicateObligation<'tcx>,
531 error: &SelectionError<'tcx>)
533 let span = obligation.cause.span;
535 let mut err = match *error {
536 SelectionError::Unimplemented => {
537 if let ObligationCauseCode::CompareImplMethodObligation {
538 item_name, impl_item_def_id, trait_item_def_id, lint_id
539 } = obligation.cause.code {
540 self.report_extra_impl_obligation(
545 &format!("`{}`", obligation.predicate),
550 match obligation.predicate {
551 ty::Predicate::Trait(ref trait_predicate) => {
552 let trait_predicate =
553 self.resolve_type_vars_if_possible(trait_predicate);
555 if self.tcx.sess.has_errors() && trait_predicate.references_error() {
558 let trait_ref = trait_predicate.to_poly_trait_ref();
559 let (post_message, pre_message) =
560 self.get_parent_trait_ref(&obligation.cause.code)
561 .map(|t| (format!(" in `{}`", t), format!("within `{}`, ", t)))
562 .unwrap_or((String::new(), String::new()));
564 let OnUnimplementedNote { message, label }
565 = self.on_unimplemented_note(trait_ref, obligation);
566 let have_alt_message = message.is_some() || label.is_some();
568 let mut err = struct_span_err!(
573 message.unwrap_or_else(|| {
574 format!("the trait bound `{}` is not satisfied{}",
575 trait_ref.to_predicate(), post_message)
578 if let Some(ref s) = label {
579 // If it has a custom "#[rustc_on_unimplemented]"
580 // error message, let's display it as the label!
581 err.span_label(span, s.as_str());
582 err.help(&format!("{}the trait `{}` is not implemented for `{}`",
585 trait_ref.self_ty()));
588 &*format!("{}the trait `{}` is not implemented for `{}`",
591 trait_ref.self_ty()));
594 // Try to report a help message
595 if !trait_ref.has_infer_types() &&
596 self.predicate_can_apply(obligation.param_env, trait_ref) {
597 // If a where-clause may be useful, remind the
598 // user that they can add it.
600 // don't display an on-unimplemented note, as
601 // these notes will often be of the form
602 // "the type `T` can't be frobnicated"
603 // which is somewhat confusing.
604 err.help(&format!("consider adding a `where {}` bound",
605 trait_ref.to_predicate()));
606 } else if !have_alt_message {
607 // Can't show anything else useful, try to find similar impls.
608 let impl_candidates = self.find_similar_impl_candidates(trait_ref);
609 self.report_similar_impl_candidates(impl_candidates, &mut err);
615 ty::Predicate::Subtype(ref predicate) => {
616 // Errors for Subtype predicates show up as
617 // `FulfillmentErrorCode::CodeSubtypeError`,
618 // not selection error.
619 span_bug!(span, "subtype requirement gave wrong error: `{:?}`", predicate)
622 ty::Predicate::Equate(ref predicate) => {
623 let predicate = self.resolve_type_vars_if_possible(predicate);
624 let err = self.equality_predicate(&obligation.cause,
625 obligation.param_env,
626 &predicate).err().unwrap();
627 struct_span_err!(self.tcx.sess, span, E0278,
628 "the requirement `{}` is not satisfied (`{}`)",
632 ty::Predicate::RegionOutlives(ref predicate) => {
633 let predicate = self.resolve_type_vars_if_possible(predicate);
634 let err = self.region_outlives_predicate(&obligation.cause,
635 &predicate).err().unwrap();
636 struct_span_err!(self.tcx.sess, span, E0279,
637 "the requirement `{}` is not satisfied (`{}`)",
641 ty::Predicate::Projection(..) | ty::Predicate::TypeOutlives(..) => {
643 self.resolve_type_vars_if_possible(&obligation.predicate);
644 struct_span_err!(self.tcx.sess, span, E0280,
645 "the requirement `{}` is not satisfied",
649 ty::Predicate::ObjectSafe(trait_def_id) => {
650 let violations = self.tcx.object_safety_violations(trait_def_id);
651 self.tcx.report_object_safety_error(span,
656 ty::Predicate::ClosureKind(closure_def_id, kind) => {
657 let found_kind = self.closure_kind(closure_def_id).unwrap();
658 let closure_span = self.tcx.hir.span_if_local(closure_def_id).unwrap();
659 let node_id = self.tcx.hir.as_local_node_id(closure_def_id).unwrap();
660 let mut err = struct_span_err!(
661 self.tcx.sess, closure_span, E0525,
662 "expected a closure that implements the `{}` trait, \
663 but this closure only implements `{}`",
668 obligation.cause.span,
669 format!("the requirement to implement `{}` derives from here", kind));
671 // Additional context information explaining why the closure only implements
672 // a particular trait.
673 if let Some(tables) = self.in_progress_tables {
674 let tables = tables.borrow();
675 let closure_hir_id = self.tcx.hir.node_to_hir_id(node_id);
676 match tables.closure_kinds().get(closure_hir_id) {
677 Some(&(ty::ClosureKind::FnOnce, Some((span, name)))) => {
678 err.span_note(span, &format!(
679 "closure is `FnOnce` because it moves the \
680 variable `{}` out of its environment", name));
682 Some(&(ty::ClosureKind::FnMut, Some((span, name)))) => {
683 err.span_note(span, &format!(
684 "closure is `FnMut` because it mutates the \
685 variable `{}` here", name));
695 ty::Predicate::WellFormed(ty) => {
696 // WF predicates cannot themselves make
697 // errors. They can only block due to
698 // ambiguity; otherwise, they always
699 // degenerate into other obligations
701 span_bug!(span, "WF predicate not satisfied for {:?}", ty);
704 ty::Predicate::ConstEvaluatable(..) => {
705 // Errors for `ConstEvaluatable` predicates show up as
706 // `SelectionError::ConstEvalFailure`,
707 // not `Unimplemented`.
709 "const-evaluatable requirement gave wrong error: `{:?}`", obligation)
714 OutputTypeParameterMismatch(ref found_trait_ref, ref expected_trait_ref, _) => {
715 let found_trait_ref = self.resolve_type_vars_if_possible(&*found_trait_ref);
716 let expected_trait_ref = self.resolve_type_vars_if_possible(&*expected_trait_ref);
717 if expected_trait_ref.self_ty().references_error() {
720 let found_trait_ty = found_trait_ref.self_ty();
722 let found_did = found_trait_ty.ty_to_def_id();
723 let found_span = found_did.and_then(|did| {
724 self.tcx.hir.span_if_local(did)
728 match found_trait_ref.skip_binder().substs.type_at(1).sty {
729 ty::TyTuple(ref tys, _) => tys.len(),
732 let (expected_tys, expected_ty_count) =
733 match expected_trait_ref.skip_binder().substs.type_at(1).sty {
734 ty::TyTuple(ref tys, _) =>
735 (tys.iter().map(|t| &t.sty).collect(), tys.len()),
736 ref sty => (vec![sty], 1),
738 if found_ty_count == expected_ty_count {
739 self.report_closure_arg_mismatch(span,
744 let expected_tuple = if expected_ty_count == 1 {
745 expected_tys.first().and_then(|t| {
746 if let &&ty::TyTuple(ref tuptys, _) = t {
756 // FIXME(#44150): Expand this to "N args expected but a N-tuple found."
757 // Type of the 1st expected argument is somehow provided as type of a
758 // found one in that case.
761 // [1i32, 2, 3].sort_by(|(a, b)| ..)
763 // // expected_trait_ref: std::ops::FnMut<(&i32, &i32)>
764 // // found_trait_ref: std::ops::FnMut<(&i32,)>
767 let (closure_span, closure_args) = found_did
768 .and_then(|did| self.tcx.hir.get_if_local(did))
770 if let hir::map::NodeExpr(
772 node: hir::ExprClosure(_, ref decl, id, span, _),
776 let ty_snips = decl.inputs.iter()
778 self.tcx.sess.codemap().span_to_snippet(ty.span).ok()
780 // filter out dummy spans
781 if snip == "," || snip == "|" {
788 .collect::<Vec<Option<String>>>();
790 let body = self.tcx.hir.body(id);
791 let pat_snips = body.arguments.iter()
793 self.tcx.sess.codemap().span_to_snippet(arg.pat.span).ok())
794 .collect::<Option<Vec<String>>>();
796 Some((span, pat_snips, ty_snips))
801 .map(|(span, pat, ty)| (Some(span), Some((pat, ty))))
802 .unwrap_or((None, None));
803 let closure_args = closure_args.and_then(|(pat, ty)| Some((pat?, ty)));
805 self.report_arg_count_mismatch(
807 closure_span.or(found_span),
812 found_trait_ty.is_closure()
817 TraitNotObjectSafe(did) => {
818 let violations = self.tcx.object_safety_violations(did);
819 self.tcx.report_object_safety_error(span, did,
823 ConstEvalFailure(ref err) => {
824 if let const_val::ErrKind::TypeckError = err.kind {
827 err.struct_error(self.tcx, span, "constant expression")
830 self.note_obligation_cause(&mut err, obligation);
834 fn report_arg_count_mismatch(
837 found_span: Option<Span>,
839 expected_tuple: Option<usize>,
841 closure_args: Option<(Vec<String>, Vec<Option<String>>)>,
843 ) -> DiagnosticBuilder<'tcx> {
844 use std::borrow::Cow;
846 let kind = if is_closure { "closure" } else { "function" };
848 let args_str = |n, distinct| format!(
851 if distinct && n >= 2 { "distinct " } else { "" },
852 if n == 1 { "" } else { "s" },
855 let expected_str = if let Some(n) = expected_tuple {
856 assert!(expected == 1);
857 if closure_args.as_ref().map(|&(ref pats, _)| pats.len()) == Some(n) {
858 Cow::from("a single tuple as argument")
860 // be verbose when numbers differ
861 Cow::from(format!("a single {}-tuple as argument", n))
864 Cow::from(args_str(expected, false))
867 let found_str = if expected_tuple.is_some() {
868 args_str(found, true)
870 args_str(found, false)
874 let mut err = struct_span_err!(self.tcx.sess, span, E0593,
875 "{} is expected to take {}, but it takes {}",
884 "expected {} that takes {}",
890 if let Some(span) = found_span {
891 if let (Some(expected_tuple), Some((pats, tys))) = (expected_tuple, closure_args) {
892 if expected_tuple != found || pats.len() != found {
893 err.span_label(span, format!("takes {}", found_str));
899 // add type annotations if available
900 if tys.iter().any(|ty| ty.is_some()) {
903 tys.into_iter().map(|ty| if let Some(ty) = ty {
907 }).collect::<Vec<String>>().join(", ")
916 "consider changing the closure to accept a tuple",
921 err.span_label(span, format!("takes {}", found_str));
928 fn report_closure_arg_mismatch(&self,
930 found_span: Option<Span>,
931 expected_ref: ty::PolyTraitRef<'tcx>,
932 found: ty::PolyTraitRef<'tcx>)
933 -> DiagnosticBuilder<'tcx>
935 fn build_fn_sig_string<'a, 'gcx, 'tcx>(tcx: ty::TyCtxt<'a, 'gcx, 'tcx>,
936 trait_ref: &ty::TraitRef<'tcx>) -> String {
937 let inputs = trait_ref.substs.type_at(1);
938 let sig = if let ty::TyTuple(inputs, _) = inputs.sty {
940 inputs.iter().map(|&x| x),
941 tcx.mk_infer(ty::TyVar(ty::TyVid { index: 0 })),
943 hir::Unsafety::Normal,
944 ::syntax::abi::Abi::Rust
948 ::std::iter::once(inputs),
949 tcx.mk_infer(ty::TyVar(ty::TyVid { index: 0 })),
951 hir::Unsafety::Normal,
952 ::syntax::abi::Abi::Rust
955 format!("{}", ty::Binder(sig))
958 let argument_is_closure = expected_ref.skip_binder().substs.type_at(0).is_closure();
959 let mut err = struct_span_err!(self.tcx.sess, span, E0631,
960 "type mismatch in {} arguments",
961 if argument_is_closure { "closure" } else { "function" });
963 let found_str = format!(
964 "expected signature of `{}`",
965 build_fn_sig_string(self.tcx, found.skip_binder())
967 err.span_label(span, found_str);
969 let found_span = found_span.unwrap_or(span);
970 let expected_str = format!(
971 "found signature of `{}`",
972 build_fn_sig_string(self.tcx, expected_ref.skip_binder())
974 err.span_label(found_span, expected_str);
980 impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
981 pub fn recursive_type_with_infinite_size_error(self,
983 -> DiagnosticBuilder<'tcx>
985 assert!(type_def_id.is_local());
986 let span = self.hir.span_if_local(type_def_id).unwrap();
987 let span = self.sess.codemap().def_span(span);
988 let mut err = struct_span_err!(self.sess, span, E0072,
989 "recursive type `{}` has infinite size",
990 self.item_path_str(type_def_id));
991 err.span_label(span, "recursive type has infinite size");
992 err.help(&format!("insert indirection (e.g., a `Box`, `Rc`, or `&`) \
993 at some point to make `{}` representable",
994 self.item_path_str(type_def_id)));
998 pub fn report_object_safety_error(self,
1000 trait_def_id: DefId,
1001 violations: Vec<ObjectSafetyViolation>)
1002 -> DiagnosticBuilder<'tcx>
1004 let trait_str = self.item_path_str(trait_def_id);
1005 let span = self.sess.codemap().def_span(span);
1006 let mut err = struct_span_err!(
1007 self.sess, span, E0038,
1008 "the trait `{}` cannot be made into an object",
1010 err.span_label(span, format!("the trait `{}` cannot be made into an object", trait_str));
1012 let mut reported_violations = FxHashSet();
1013 for violation in violations {
1014 if !reported_violations.insert(violation.clone()) {
1017 err.note(&violation.error_msg());
1023 impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
1024 fn maybe_report_ambiguity(&self, obligation: &PredicateObligation<'tcx>,
1025 body_id: Option<hir::BodyId>) {
1026 // Unable to successfully determine, probably means
1027 // insufficient type information, but could mean
1028 // ambiguous impls. The latter *ought* to be a
1029 // coherence violation, so we don't report it here.
1031 let predicate = self.resolve_type_vars_if_possible(&obligation.predicate);
1032 let span = obligation.cause.span;
1034 debug!("maybe_report_ambiguity(predicate={:?}, obligation={:?})",
1038 // Ambiguity errors are often caused as fallout from earlier
1039 // errors. So just ignore them if this infcx is tainted.
1040 if self.is_tainted_by_errors() {
1045 ty::Predicate::Trait(ref data) => {
1046 let trait_ref = data.to_poly_trait_ref();
1047 let self_ty = trait_ref.self_ty();
1048 if predicate.references_error() {
1051 // Typically, this ambiguity should only happen if
1052 // there are unresolved type inference variables
1053 // (otherwise it would suggest a coherence
1054 // failure). But given #21974 that is not necessarily
1055 // the case -- we can have multiple where clauses that
1056 // are only distinguished by a region, which results
1057 // in an ambiguity even when all types are fully
1058 // known, since we don't dispatch based on region
1061 // This is kind of a hack: it frequently happens that some earlier
1062 // error prevents types from being fully inferred, and then we get
1063 // a bunch of uninteresting errors saying something like "<generic
1064 // #0> doesn't implement Sized". It may even be true that we
1065 // could just skip over all checks where the self-ty is an
1066 // inference variable, but I was afraid that there might be an
1067 // inference variable created, registered as an obligation, and
1068 // then never forced by writeback, and hence by skipping here we'd
1069 // be ignoring the fact that we don't KNOW the type works
1070 // out. Though even that would probably be harmless, given that
1071 // we're only talking about builtin traits, which are known to be
1072 // inhabited. But in any case I just threw in this check for
1073 // has_errors() to be sure that compilation isn't happening
1074 // anyway. In that case, why inundate the user.
1075 if !self.tcx.sess.has_errors() {
1077 self.tcx.lang_items().sized_trait()
1078 .map_or(false, |sized_id| sized_id == trait_ref.def_id())
1080 self.need_type_info(body_id, span, self_ty);
1082 let mut err = struct_span_err!(self.tcx.sess,
1084 "type annotations required: \
1085 cannot resolve `{}`",
1087 self.note_obligation_cause(&mut err, obligation);
1093 ty::Predicate::WellFormed(ty) => {
1094 // Same hacky approach as above to avoid deluging user
1095 // with error messages.
1096 if !ty.references_error() && !self.tcx.sess.has_errors() {
1097 self.need_type_info(body_id, span, ty);
1101 ty::Predicate::Subtype(ref data) => {
1102 if data.references_error() || self.tcx.sess.has_errors() {
1103 // no need to overload user in such cases
1105 let &SubtypePredicate { a_is_expected: _, a, b } = data.skip_binder();
1106 // both must be type variables, or the other would've been instantiated
1107 assert!(a.is_ty_var() && b.is_ty_var());
1108 self.need_type_info(body_id,
1109 obligation.cause.span,
1115 if !self.tcx.sess.has_errors() {
1116 let mut err = struct_span_err!(self.tcx.sess,
1117 obligation.cause.span, E0284,
1118 "type annotations required: \
1119 cannot resolve `{}`",
1121 self.note_obligation_cause(&mut err, obligation);
1128 /// Returns whether the trait predicate may apply for *some* assignment
1129 /// to the type parameters.
1130 fn predicate_can_apply(&self,
1131 param_env: ty::ParamEnv<'tcx>,
1132 pred: ty::PolyTraitRef<'tcx>)
1134 struct ParamToVarFolder<'a, 'gcx: 'a+'tcx, 'tcx: 'a> {
1135 infcx: &'a InferCtxt<'a, 'gcx, 'tcx>,
1136 var_map: FxHashMap<Ty<'tcx>, Ty<'tcx>>
1139 impl<'a, 'gcx, 'tcx> TypeFolder<'gcx, 'tcx> for ParamToVarFolder<'a, 'gcx, 'tcx> {
1140 fn tcx<'b>(&'b self) -> TyCtxt<'b, 'gcx, 'tcx> { self.infcx.tcx }
1142 fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> {
1143 if let ty::TyParam(ty::ParamTy {name, ..}) = ty.sty {
1144 let infcx = self.infcx;
1145 self.var_map.entry(ty).or_insert_with(||
1147 TypeVariableOrigin::TypeParameterDefinition(DUMMY_SP, name)))
1149 ty.super_fold_with(self)
1155 let mut selcx = SelectionContext::new(self);
1157 let cleaned_pred = pred.fold_with(&mut ParamToVarFolder {
1159 var_map: FxHashMap()
1162 let cleaned_pred = super::project::normalize(
1165 ObligationCause::dummy(),
1169 let obligation = Obligation::new(
1170 ObligationCause::dummy(),
1172 cleaned_pred.to_predicate()
1175 selcx.evaluate_obligation(&obligation)
1179 fn note_obligation_cause<T>(&self,
1180 err: &mut DiagnosticBuilder,
1181 obligation: &Obligation<'tcx, T>)
1182 where T: fmt::Display
1184 self.note_obligation_cause_code(err,
1185 &obligation.predicate,
1186 &obligation.cause.code);
1189 fn note_obligation_cause_code<T>(&self,
1190 err: &mut DiagnosticBuilder,
1192 cause_code: &ObligationCauseCode<'tcx>)
1193 where T: fmt::Display
1197 ObligationCauseCode::ExprAssignable |
1198 ObligationCauseCode::MatchExpressionArm { .. } |
1199 ObligationCauseCode::IfExpression |
1200 ObligationCauseCode::IfExpressionWithNoElse |
1201 ObligationCauseCode::EquatePredicate |
1202 ObligationCauseCode::MainFunctionType |
1203 ObligationCauseCode::StartFunctionType |
1204 ObligationCauseCode::IntrinsicType |
1205 ObligationCauseCode::MethodReceiver |
1206 ObligationCauseCode::ReturnNoExpression |
1207 ObligationCauseCode::MiscObligation => {
1209 ObligationCauseCode::SliceOrArrayElem => {
1210 err.note("slice and array elements must have `Sized` type");
1212 ObligationCauseCode::TupleElem => {
1213 err.note("only the last element of a tuple may have a dynamically sized type");
1215 ObligationCauseCode::ProjectionWf(data) => {
1216 err.note(&format!("required so that the projection `{}` is well-formed",
1219 ObligationCauseCode::ReferenceOutlivesReferent(ref_ty) => {
1220 err.note(&format!("required so that reference `{}` does not outlive its referent",
1223 ObligationCauseCode::ObjectTypeBound(object_ty, region) => {
1224 err.note(&format!("required so that the lifetime bound of `{}` for `{}` \
1226 region, object_ty));
1228 ObligationCauseCode::ItemObligation(item_def_id) => {
1229 let item_name = tcx.item_path_str(item_def_id);
1230 err.note(&format!("required by `{}`", item_name));
1232 ObligationCauseCode::ObjectCastObligation(object_ty) => {
1233 err.note(&format!("required for the cast to the object type `{}`",
1234 self.ty_to_string(object_ty)));
1236 ObligationCauseCode::RepeatVec => {
1237 err.note("the `Copy` trait is required because the \
1238 repeated element will be copied");
1240 ObligationCauseCode::VariableType(_) => {
1241 err.note("all local variables must have a statically known size");
1243 ObligationCauseCode::SizedReturnType => {
1244 err.note("the return type of a function must have a \
1245 statically known size");
1247 ObligationCauseCode::AssignmentLhsSized => {
1248 err.note("the left-hand-side of an assignment must have a statically known size");
1250 ObligationCauseCode::TupleInitializerSized => {
1251 err.note("tuples must have a statically known size to be initialized");
1253 ObligationCauseCode::StructInitializerSized => {
1254 err.note("structs must have a statically known size to be initialized");
1256 ObligationCauseCode::FieldSized(ref item) => {
1258 AdtKind::Struct => {
1259 err.note("only the last field of a struct may have a dynamically \
1263 err.note("no field of a union may have a dynamically sized type");
1266 err.note("no field of an enum variant may have a dynamically sized type");
1270 ObligationCauseCode::ConstSized => {
1271 err.note("constant expressions must have a statically known size");
1273 ObligationCauseCode::SharedStatic => {
1274 err.note("shared static variables must have a type that implements `Sync`");
1276 ObligationCauseCode::BuiltinDerivedObligation(ref data) => {
1277 let parent_trait_ref = self.resolve_type_vars_if_possible(&data.parent_trait_ref);
1278 err.note(&format!("required because it appears within the type `{}`",
1279 parent_trait_ref.0.self_ty()));
1280 let parent_predicate = parent_trait_ref.to_predicate();
1281 self.note_obligation_cause_code(err,
1285 ObligationCauseCode::ImplDerivedObligation(ref data) => {
1286 let parent_trait_ref = self.resolve_type_vars_if_possible(&data.parent_trait_ref);
1288 &format!("required because of the requirements on the impl of `{}` for `{}`",
1290 parent_trait_ref.0.self_ty()));
1291 let parent_predicate = parent_trait_ref.to_predicate();
1292 self.note_obligation_cause_code(err,
1296 ObligationCauseCode::CompareImplMethodObligation { .. } => {
1298 &format!("the requirement `{}` appears on the impl method \
1299 but not on the corresponding trait method",
1302 ObligationCauseCode::ReturnType(_) |
1303 ObligationCauseCode::BlockTailExpression(_) => (),
1307 fn suggest_new_overflow_limit(&self, err: &mut DiagnosticBuilder) {
1308 let current_limit = self.tcx.sess.recursion_limit.get();
1309 let suggested_limit = current_limit * 2;
1310 err.help(&format!("consider adding a `#![recursion_limit=\"{}\"]` attribute to your crate",