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(obligation.cause.span, def_id);
296 let impl_trait_ref = tcx
297 .impl_trait_ref(def_id)
299 .subst(tcx, impl_substs);
301 let impl_self_ty = impl_trait_ref.self_ty();
303 if let Ok(..) = self.can_eq(param_env, trait_self_ty, impl_self_ty) {
304 self_match_impls.push(def_id);
306 if trait_ref.substs.types().skip(1)
307 .zip(impl_trait_ref.substs.types().skip(1))
308 .all(|(u,v)| self.fuzzy_match_tys(u, v))
310 fuzzy_match_impls.push(def_id);
315 let impl_def_id = if self_match_impls.len() == 1 {
317 } else if fuzzy_match_impls.len() == 1 {
323 if tcx.has_attr(impl_def_id, "rustc_on_unimplemented") {
330 fn on_unimplemented_note(
332 trait_ref: ty::PolyTraitRef<'tcx>,
333 obligation: &PredicateObligation<'tcx>) ->
336 let def_id = self.impl_similar_to(trait_ref, obligation)
337 .unwrap_or(trait_ref.def_id());
338 let trait_ref = *trait_ref.skip_binder();
342 let mut flags = vec![];
343 let direct = match obligation.cause.code {
344 ObligationCauseCode::BuiltinDerivedObligation(..) |
345 ObligationCauseCode::ImplDerivedObligation(..) => false,
349 // this is a "direct", user-specified, rather than derived,
351 flags.push(("direct", None));
354 if let ObligationCauseCode::ItemObligation(item) = obligation.cause.code {
355 // FIXME: maybe also have some way of handling methods
356 // from other traits? That would require name resolution,
357 // which we might want to be some sort of hygienic.
359 // Currently I'm leaving it for what I need for `try`.
360 if self.tcx.trait_of_item(item) == Some(trait_ref.def_id) {
361 method = self.tcx.item_name(item);
362 flags.push(("from_method", None));
363 flags.push(("from_method", Some(&*method)));
367 if let Some(k) = obligation.cause.span.compiler_desugaring_kind() {
368 desugaring = k.as_symbol().as_str();
369 flags.push(("from_desugaring", None));
370 flags.push(("from_desugaring", Some(&*desugaring)));
373 if let Ok(Some(command)) = OnUnimplementedDirective::of_item(
374 self.tcx, trait_ref.def_id, def_id
376 command.evaluate(self.tcx, trait_ref, &flags)
378 OnUnimplementedNote::empty()
382 fn find_similar_impl_candidates(&self,
383 trait_ref: ty::PolyTraitRef<'tcx>)
384 -> Vec<ty::TraitRef<'tcx>>
386 let simp = fast_reject::simplify_type(self.tcx,
387 trait_ref.skip_binder().self_ty(),
389 let mut impl_candidates = Vec::new();
392 Some(simp) => self.tcx.for_each_impl(trait_ref.def_id(), |def_id| {
393 let imp = self.tcx.impl_trait_ref(def_id).unwrap();
394 let imp_simp = fast_reject::simplify_type(self.tcx,
397 if let Some(imp_simp) = imp_simp {
398 if simp != imp_simp {
402 impl_candidates.push(imp);
404 None => self.tcx.for_each_impl(trait_ref.def_id(), |def_id| {
405 impl_candidates.push(
406 self.tcx.impl_trait_ref(def_id).unwrap());
412 fn report_similar_impl_candidates(&self,
413 impl_candidates: Vec<ty::TraitRef<'tcx>>,
414 err: &mut DiagnosticBuilder)
416 if impl_candidates.is_empty() {
420 let end = if impl_candidates.len() <= 5 {
421 impl_candidates.len()
425 err.help(&format!("the following implementations were found:{}{}",
426 &impl_candidates[0..end].iter().map(|candidate| {
427 format!("\n {:?}", candidate)
428 }).collect::<String>(),
429 if impl_candidates.len() > 5 {
430 format!("\nand {} others", impl_candidates.len() - 4)
437 /// Reports that an overflow has occurred and halts compilation. We
438 /// halt compilation unconditionally because it is important that
439 /// overflows never be masked -- they basically represent computations
440 /// whose result could not be truly determined and thus we can't say
441 /// if the program type checks or not -- and they are unusual
442 /// occurrences in any case.
443 pub fn report_overflow_error<T>(&self,
444 obligation: &Obligation<'tcx, T>,
445 suggest_increasing_limit: bool) -> !
446 where T: fmt::Display + TypeFoldable<'tcx>
449 self.resolve_type_vars_if_possible(&obligation.predicate);
450 let mut err = struct_span_err!(self.tcx.sess, obligation.cause.span, E0275,
451 "overflow evaluating the requirement `{}`",
454 if suggest_increasing_limit {
455 self.suggest_new_overflow_limit(&mut err);
458 self.note_obligation_cause(&mut err, obligation);
461 self.tcx.sess.abort_if_errors();
465 /// Reports that a cycle was detected which led to overflow and halts
466 /// compilation. This is equivalent to `report_overflow_error` except
467 /// that we can give a more helpful error message (and, in particular,
468 /// we do not suggest increasing the overflow limit, which is not
470 pub fn report_overflow_error_cycle(&self, cycle: &[PredicateObligation<'tcx>]) -> ! {
471 let cycle = self.resolve_type_vars_if_possible(&cycle.to_owned());
472 assert!(cycle.len() > 0);
474 debug!("report_overflow_error_cycle: cycle={:?}", cycle);
476 self.report_overflow_error(&cycle[0], false);
479 pub fn report_extra_impl_obligation(&self,
481 item_name: ast::Name,
482 _impl_item_def_id: DefId,
483 trait_item_def_id: DefId,
484 requirement: &fmt::Display)
485 -> DiagnosticBuilder<'tcx>
487 let msg = "impl has stricter requirements than trait";
488 let sp = self.tcx.sess.codemap().def_span(error_span);
490 let mut err = struct_span_err!(self.tcx.sess, sp, E0276, "{}", msg);
492 if let Some(trait_item_span) = self.tcx.hir.span_if_local(trait_item_def_id) {
493 let span = self.tcx.sess.codemap().def_span(trait_item_span);
494 err.span_label(span, format!("definition of `{}` from trait", item_name));
497 err.span_label(sp, format!("impl has extra requirement {}", requirement));
503 /// Get the parent trait chain start
504 fn get_parent_trait_ref(&self, code: &ObligationCauseCode<'tcx>) -> Option<String> {
506 &ObligationCauseCode::BuiltinDerivedObligation(ref data) => {
507 let parent_trait_ref = self.resolve_type_vars_if_possible(
508 &data.parent_trait_ref);
509 match self.get_parent_trait_ref(&data.parent_code) {
511 None => Some(format!("{}", parent_trait_ref.0.self_ty())),
518 pub fn report_selection_error(&self,
519 obligation: &PredicateObligation<'tcx>,
520 error: &SelectionError<'tcx>)
522 let span = obligation.cause.span;
524 let mut err = match *error {
525 SelectionError::Unimplemented => {
526 if let ObligationCauseCode::CompareImplMethodObligation {
527 item_name, impl_item_def_id, trait_item_def_id,
528 } = obligation.cause.code {
529 self.report_extra_impl_obligation(
534 &format!("`{}`", obligation.predicate))
538 match obligation.predicate {
539 ty::Predicate::Trait(ref trait_predicate) => {
540 let trait_predicate =
541 self.resolve_type_vars_if_possible(trait_predicate);
543 if self.tcx.sess.has_errors() && trait_predicate.references_error() {
546 let trait_ref = trait_predicate.to_poly_trait_ref();
547 let (post_message, pre_message) =
548 self.get_parent_trait_ref(&obligation.cause.code)
549 .map(|t| (format!(" in `{}`", t), format!("within `{}`, ", t)))
550 .unwrap_or((String::new(), String::new()));
552 let OnUnimplementedNote { message, label }
553 = self.on_unimplemented_note(trait_ref, obligation);
554 let have_alt_message = message.is_some() || label.is_some();
556 let mut err = struct_span_err!(
561 message.unwrap_or_else(|| {
562 format!("the trait bound `{}` is not satisfied{}",
563 trait_ref.to_predicate(), post_message)
566 if let Some(ref s) = label {
567 // If it has a custom "#[rustc_on_unimplemented]"
568 // error message, let's display it as the label!
569 err.span_label(span, s.as_str());
570 err.help(&format!("{}the trait `{}` is not implemented for `{}`",
573 trait_ref.self_ty()));
576 &*format!("{}the trait `{}` is not implemented for `{}`",
579 trait_ref.self_ty()));
582 self.suggest_borrow_on_unsized_slice(&obligation.cause.code, &mut err);
584 // Try to report a help message
585 if !trait_ref.has_infer_types() &&
586 self.predicate_can_apply(obligation.param_env, trait_ref) {
587 // If a where-clause may be useful, remind the
588 // user that they can add it.
590 // don't display an on-unimplemented note, as
591 // these notes will often be of the form
592 // "the type `T` can't be frobnicated"
593 // which is somewhat confusing.
594 err.help(&format!("consider adding a `where {}` bound",
595 trait_ref.to_predicate()));
596 } else if !have_alt_message {
597 // Can't show anything else useful, try to find similar impls.
598 let impl_candidates = self.find_similar_impl_candidates(trait_ref);
599 self.report_similar_impl_candidates(impl_candidates, &mut err);
605 ty::Predicate::Subtype(ref predicate) => {
606 // Errors for Subtype predicates show up as
607 // `FulfillmentErrorCode::CodeSubtypeError`,
608 // not selection error.
609 span_bug!(span, "subtype requirement gave wrong error: `{:?}`", predicate)
612 ty::Predicate::Equate(ref predicate) => {
613 let predicate = self.resolve_type_vars_if_possible(predicate);
614 let err = self.equality_predicate(&obligation.cause,
615 obligation.param_env,
616 &predicate).err().unwrap();
617 struct_span_err!(self.tcx.sess, span, E0278,
618 "the requirement `{}` is not satisfied (`{}`)",
622 ty::Predicate::RegionOutlives(ref predicate) => {
623 let predicate = self.resolve_type_vars_if_possible(predicate);
624 let err = self.region_outlives_predicate(&obligation.cause,
625 &predicate).err().unwrap();
626 struct_span_err!(self.tcx.sess, span, E0279,
627 "the requirement `{}` is not satisfied (`{}`)",
631 ty::Predicate::Projection(..) | ty::Predicate::TypeOutlives(..) => {
633 self.resolve_type_vars_if_possible(&obligation.predicate);
634 struct_span_err!(self.tcx.sess, span, E0280,
635 "the requirement `{}` is not satisfied",
639 ty::Predicate::ObjectSafe(trait_def_id) => {
640 let violations = self.tcx.object_safety_violations(trait_def_id);
641 self.tcx.report_object_safety_error(span,
646 ty::Predicate::ClosureKind(closure_def_id, closure_substs, kind) => {
647 let found_kind = self.closure_kind(closure_def_id, closure_substs).unwrap();
648 let closure_span = self.tcx.sess.codemap()
649 .def_span(self.tcx.hir.span_if_local(closure_def_id).unwrap());
650 let node_id = self.tcx.hir.as_local_node_id(closure_def_id).unwrap();
651 let mut err = struct_span_err!(
652 self.tcx.sess, closure_span, E0525,
653 "expected a closure that implements the `{}` trait, \
654 but this closure only implements `{}`",
660 format!("this closure implements `{}`, not `{}`", found_kind, kind));
662 obligation.cause.span,
663 format!("the requirement to implement `{}` derives from here", kind));
665 // Additional context information explaining why the closure only implements
666 // a particular trait.
667 if let Some(tables) = self.in_progress_tables {
668 let tables = tables.borrow();
669 let closure_hir_id = self.tcx.hir.node_to_hir_id(node_id);
670 match (found_kind, tables.closure_kind_origins().get(closure_hir_id)) {
671 (ty::ClosureKind::FnOnce, Some((span, name))) => {
672 err.span_label(*span, format!(
673 "closure is `FnOnce` because it moves the \
674 variable `{}` out of its environment", name));
676 (ty::ClosureKind::FnMut, Some((span, name))) => {
677 err.span_label(*span, format!(
678 "closure is `FnMut` because it mutates the \
679 variable `{}` here", name));
689 ty::Predicate::WellFormed(ty) => {
690 // WF predicates cannot themselves make
691 // errors. They can only block due to
692 // ambiguity; otherwise, they always
693 // degenerate into other obligations
695 span_bug!(span, "WF predicate not satisfied for {:?}", ty);
698 ty::Predicate::ConstEvaluatable(..) => {
699 // Errors for `ConstEvaluatable` predicates show up as
700 // `SelectionError::ConstEvalFailure`,
701 // not `Unimplemented`.
703 "const-evaluatable requirement gave wrong error: `{:?}`", obligation)
708 OutputTypeParameterMismatch(ref found_trait_ref, ref expected_trait_ref, _) => {
709 let found_trait_ref = self.resolve_type_vars_if_possible(&*found_trait_ref);
710 let expected_trait_ref = self.resolve_type_vars_if_possible(&*expected_trait_ref);
711 if expected_trait_ref.self_ty().references_error() {
714 let found_trait_ty = found_trait_ref.self_ty();
716 let found_did = found_trait_ty.ty_to_def_id();
717 let found_span = found_did.and_then(|did| {
718 self.tcx.hir.span_if_local(did)
719 }).map(|sp| self.tcx.sess.codemap().def_span(sp)); // the sp could be an fn def
721 let found = match found_trait_ref.skip_binder().substs.type_at(1).sty {
722 ty::TyTuple(ref tys, _) => tys.iter()
723 .map(|_| ArgKind::empty()).collect::<Vec<_>>(),
724 _ => vec![ArgKind::empty()],
726 let expected = match expected_trait_ref.skip_binder().substs.type_at(1).sty {
727 ty::TyTuple(ref tys, _) => tys.iter()
728 .map(|t| match t.sty {
729 ty::TypeVariants::TyTuple(ref tys, _) => ArgKind::Tuple(
732 .map(|ty| ("_".to_owned(), format!("{}", ty.sty)))
735 _ => ArgKind::Arg("_".to_owned(), format!("{}", t.sty)),
737 ref sty => vec![ArgKind::Arg("_".to_owned(), format!("{}", sty))],
739 if found.len()== expected.len() {
740 self.report_closure_arg_mismatch(span,
745 let (closure_span, found) = found_did
746 .and_then(|did| self.tcx.hir.get_if_local(did))
747 .map(|node| self.get_fn_like_arguments(node))
748 .unwrap_or((found_span.unwrap(), found));
750 self.report_arg_count_mismatch(span,
754 found_trait_ty.is_closure())
758 TraitNotObjectSafe(did) => {
759 let violations = self.tcx.object_safety_violations(did);
760 self.tcx.report_object_safety_error(span, did,
764 ConstEvalFailure(ref err) => {
765 if let const_val::ErrKind::TypeckError = err.kind {
768 err.struct_error(self.tcx, span, "constant expression")
771 self.note_obligation_cause(&mut err, obligation);
775 /// When encountering an assignment of an unsized trait, like `let x = ""[..];`, provide a
776 /// suggestion to borrow the initializer in order to use have a slice instead.
777 fn suggest_borrow_on_unsized_slice(&self,
778 code: &ObligationCauseCode<'tcx>,
779 err: &mut DiagnosticBuilder<'tcx>) {
780 if let &ObligationCauseCode::VariableType(node_id) = code {
781 let parent_node = self.tcx.hir.get_parent_node(node_id);
782 if let Some(hir::map::NodeLocal(ref local)) = self.tcx.hir.find(parent_node) {
783 if let Some(ref expr) = local.init {
784 if let hir::ExprIndex(_, _) = expr.node {
785 if let Ok(snippet) = self.tcx.sess.codemap().span_to_snippet(expr.span) {
786 err.span_suggestion(expr.span,
787 "consider borrowing here",
788 format!("&{}", snippet));
796 fn get_fn_like_arguments(&self, node: hir::map::Node) -> (Span, Vec<ArgKind>) {
798 hir::map::NodeExpr(&hir::Expr {
799 node: hir::ExprClosure(_, ref _decl, id, span, _),
802 (self.tcx.sess.codemap().def_span(span), self.tcx.hir.body(id).arguments.iter()
805 node: hir::PatKind::Tuple(args, _),
808 } = arg.pat.clone().into_inner() {
811 args.iter().map(|pat| {
812 let snippet = self.tcx.sess.codemap()
813 .span_to_snippet(pat.span).unwrap();
814 (snippet, "_".to_owned())
815 }).collect::<Vec<_>>(),
818 let name = self.tcx.sess.codemap()
819 .span_to_snippet(arg.pat.span).unwrap();
820 ArgKind::Arg(name, "_".to_owned())
823 .collect::<Vec<ArgKind>>())
825 hir::map::NodeItem(&hir::Item {
827 node: hir::ItemFn(ref decl, ..),
830 hir::map::NodeImplItem(&hir::ImplItem {
832 node: hir::ImplItemKind::Method(hir::MethodSig { ref decl, .. }, _),
835 hir::map::NodeTraitItem(&hir::TraitItem {
837 node: hir::TraitItemKind::Method(hir::MethodSig { ref decl, .. }, _),
840 (self.tcx.sess.codemap().def_span(span), decl.inputs.iter()
841 .map(|arg| match arg.clone().into_inner().node {
842 hir::TyTup(ref tys) => ArgKind::Tuple(
845 .map(|_| ("_".to_owned(), "_".to_owned()))
846 .collect::<Vec<_>>(),
848 _ => ArgKind::Arg("_".to_owned(), "_".to_owned())
849 }).collect::<Vec<ArgKind>>())
851 _ => panic!("non-FnLike node found: {:?}", node),
855 fn report_arg_count_mismatch(
859 expected_args: Vec<ArgKind>,
860 found_args: Vec<ArgKind>,
862 ) -> DiagnosticBuilder<'tcx> {
863 let kind = if is_closure { "closure" } else { "function" };
865 let args_str = |arguments: &Vec<ArgKind>, other: &Vec<ArgKind>| {
866 let arg_length = arguments.len();
867 let distinct = match &other[..] {
868 &[ArgKind::Tuple(..)] => true,
871 match (arg_length, arguments.get(0)) {
872 (1, Some(&ArgKind::Tuple(_, ref fields))) => {
873 format!("a single {}-tuple as argument", fields.len())
875 _ => format!("{} {}argument{}",
877 if distinct && arg_length > 1 { "distinct " } else { "" },
878 if arg_length == 1 { "" } else { "s" }),
882 let expected_str = args_str(&expected_args, &found_args);
883 let found_str = args_str(&found_args, &expected_args);
885 let mut err = struct_span_err!(
889 "{} is expected to take {}, but it takes {}",
895 err.span_label(span, format!( "expected {} that takes {}", kind, expected_str));
896 err.span_label(found_span, format!("takes {}", found_str));
898 if let &[ArgKind::Tuple(_, ref fields)] = &found_args[..] {
899 if fields.len() == expected_args.len() {
900 let sugg = fields.iter()
901 .map(|(name, _)| name.to_owned())
902 .collect::<Vec<String>>().join(", ");
903 err.span_suggestion(found_span,
904 "change the closure to take multiple arguments instead of \
906 format!("|{}|", sugg));
909 if let &[ArgKind::Tuple(_, ref fields)] = &expected_args[..] {
910 if fields.len() == found_args.len() && is_closure {
914 .map(|arg| match arg {
915 ArgKind::Arg(name, _) => name.to_owned(),
918 .collect::<Vec<String>>()
920 // add type annotations if available
921 if found_args.iter().any(|arg| match arg {
922 ArgKind::Arg(_, ty) => ty != "_",
927 .map(|(_, ty)| ty.to_owned())
928 .collect::<Vec<String>>()
934 err.span_suggestion(found_span,
935 "change the closure to accept a tuple instead of individual \
944 fn report_closure_arg_mismatch(&self,
946 found_span: Option<Span>,
947 expected_ref: ty::PolyTraitRef<'tcx>,
948 found: ty::PolyTraitRef<'tcx>)
949 -> DiagnosticBuilder<'tcx>
951 fn build_fn_sig_string<'a, 'gcx, 'tcx>(tcx: ty::TyCtxt<'a, 'gcx, 'tcx>,
952 trait_ref: &ty::TraitRef<'tcx>) -> String {
953 let inputs = trait_ref.substs.type_at(1);
954 let sig = if let ty::TyTuple(inputs, _) = inputs.sty {
956 inputs.iter().map(|&x| x),
957 tcx.mk_infer(ty::TyVar(ty::TyVid { index: 0 })),
959 hir::Unsafety::Normal,
960 ::syntax::abi::Abi::Rust
964 ::std::iter::once(inputs),
965 tcx.mk_infer(ty::TyVar(ty::TyVid { index: 0 })),
967 hir::Unsafety::Normal,
968 ::syntax::abi::Abi::Rust
971 format!("{}", ty::Binder(sig))
974 let argument_is_closure = expected_ref.skip_binder().substs.type_at(0).is_closure();
975 let mut err = struct_span_err!(self.tcx.sess, span, E0631,
976 "type mismatch in {} arguments",
977 if argument_is_closure { "closure" } else { "function" });
979 let found_str = format!(
980 "expected signature of `{}`",
981 build_fn_sig_string(self.tcx, found.skip_binder())
983 err.span_label(span, found_str);
985 let found_span = found_span.unwrap_or(span);
986 let expected_str = format!(
987 "found signature of `{}`",
988 build_fn_sig_string(self.tcx, expected_ref.skip_binder())
990 err.span_label(found_span, expected_str);
996 impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
997 pub fn recursive_type_with_infinite_size_error(self,
999 -> DiagnosticBuilder<'tcx>
1001 assert!(type_def_id.is_local());
1002 let span = self.hir.span_if_local(type_def_id).unwrap();
1003 let span = self.sess.codemap().def_span(span);
1004 let mut err = struct_span_err!(self.sess, span, E0072,
1005 "recursive type `{}` has infinite size",
1006 self.item_path_str(type_def_id));
1007 err.span_label(span, "recursive type has infinite size");
1008 err.help(&format!("insert indirection (e.g., a `Box`, `Rc`, or `&`) \
1009 at some point to make `{}` representable",
1010 self.item_path_str(type_def_id)));
1014 pub fn report_object_safety_error(self,
1016 trait_def_id: DefId,
1017 violations: Vec<ObjectSafetyViolation>)
1018 -> DiagnosticBuilder<'tcx>
1020 let trait_str = self.item_path_str(trait_def_id);
1021 let span = self.sess.codemap().def_span(span);
1022 let mut err = struct_span_err!(
1023 self.sess, span, E0038,
1024 "the trait `{}` cannot be made into an object",
1026 err.span_label(span, format!("the trait `{}` cannot be made into an object", trait_str));
1028 let mut reported_violations = FxHashSet();
1029 for violation in violations {
1030 if !reported_violations.insert(violation.clone()) {
1033 err.note(&violation.error_msg());
1039 impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
1040 fn maybe_report_ambiguity(&self, obligation: &PredicateObligation<'tcx>,
1041 body_id: Option<hir::BodyId>) {
1042 // Unable to successfully determine, probably means
1043 // insufficient type information, but could mean
1044 // ambiguous impls. The latter *ought* to be a
1045 // coherence violation, so we don't report it here.
1047 let predicate = self.resolve_type_vars_if_possible(&obligation.predicate);
1048 let span = obligation.cause.span;
1050 debug!("maybe_report_ambiguity(predicate={:?}, obligation={:?})",
1054 // Ambiguity errors are often caused as fallout from earlier
1055 // errors. So just ignore them if this infcx is tainted.
1056 if self.is_tainted_by_errors() {
1061 ty::Predicate::Trait(ref data) => {
1062 let trait_ref = data.to_poly_trait_ref();
1063 let self_ty = trait_ref.self_ty();
1064 if predicate.references_error() {
1067 // Typically, this ambiguity should only happen if
1068 // there are unresolved type inference variables
1069 // (otherwise it would suggest a coherence
1070 // failure). But given #21974 that is not necessarily
1071 // the case -- we can have multiple where clauses that
1072 // are only distinguished by a region, which results
1073 // in an ambiguity even when all types are fully
1074 // known, since we don't dispatch based on region
1077 // This is kind of a hack: it frequently happens that some earlier
1078 // error prevents types from being fully inferred, and then we get
1079 // a bunch of uninteresting errors saying something like "<generic
1080 // #0> doesn't implement Sized". It may even be true that we
1081 // could just skip over all checks where the self-ty is an
1082 // inference variable, but I was afraid that there might be an
1083 // inference variable created, registered as an obligation, and
1084 // then never forced by writeback, and hence by skipping here we'd
1085 // be ignoring the fact that we don't KNOW the type works
1086 // out. Though even that would probably be harmless, given that
1087 // we're only talking about builtin traits, which are known to be
1088 // inhabited. But in any case I just threw in this check for
1089 // has_errors() to be sure that compilation isn't happening
1090 // anyway. In that case, why inundate the user.
1091 if !self.tcx.sess.has_errors() {
1093 self.tcx.lang_items().sized_trait()
1094 .map_or(false, |sized_id| sized_id == trait_ref.def_id())
1096 self.need_type_info(body_id, span, self_ty);
1098 let mut err = struct_span_err!(self.tcx.sess,
1100 "type annotations required: \
1101 cannot resolve `{}`",
1103 self.note_obligation_cause(&mut err, obligation);
1109 ty::Predicate::WellFormed(ty) => {
1110 // Same hacky approach as above to avoid deluging user
1111 // with error messages.
1112 if !ty.references_error() && !self.tcx.sess.has_errors() {
1113 self.need_type_info(body_id, span, ty);
1117 ty::Predicate::Subtype(ref data) => {
1118 if data.references_error() || self.tcx.sess.has_errors() {
1119 // no need to overload user in such cases
1121 let &SubtypePredicate { a_is_expected: _, a, b } = data.skip_binder();
1122 // both must be type variables, or the other would've been instantiated
1123 assert!(a.is_ty_var() && b.is_ty_var());
1124 self.need_type_info(body_id,
1125 obligation.cause.span,
1131 if !self.tcx.sess.has_errors() {
1132 let mut err = struct_span_err!(self.tcx.sess,
1133 obligation.cause.span, E0284,
1134 "type annotations required: \
1135 cannot resolve `{}`",
1137 self.note_obligation_cause(&mut err, obligation);
1144 /// Returns whether the trait predicate may apply for *some* assignment
1145 /// to the type parameters.
1146 fn predicate_can_apply(&self,
1147 param_env: ty::ParamEnv<'tcx>,
1148 pred: ty::PolyTraitRef<'tcx>)
1150 struct ParamToVarFolder<'a, 'gcx: 'a+'tcx, 'tcx: 'a> {
1151 infcx: &'a InferCtxt<'a, 'gcx, 'tcx>,
1152 var_map: FxHashMap<Ty<'tcx>, Ty<'tcx>>
1155 impl<'a, 'gcx, 'tcx> TypeFolder<'gcx, 'tcx> for ParamToVarFolder<'a, 'gcx, 'tcx> {
1156 fn tcx<'b>(&'b self) -> TyCtxt<'b, 'gcx, 'tcx> { self.infcx.tcx }
1158 fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> {
1159 if let ty::TyParam(ty::ParamTy {name, ..}) = ty.sty {
1160 let infcx = self.infcx;
1161 self.var_map.entry(ty).or_insert_with(||
1163 TypeVariableOrigin::TypeParameterDefinition(DUMMY_SP, name)))
1165 ty.super_fold_with(self)
1171 let mut selcx = SelectionContext::new(self);
1173 let cleaned_pred = pred.fold_with(&mut ParamToVarFolder {
1175 var_map: FxHashMap()
1178 let cleaned_pred = super::project::normalize(
1181 ObligationCause::dummy(),
1185 let obligation = Obligation::new(
1186 ObligationCause::dummy(),
1188 cleaned_pred.to_predicate()
1191 selcx.evaluate_obligation(&obligation)
1195 fn note_obligation_cause<T>(&self,
1196 err: &mut DiagnosticBuilder,
1197 obligation: &Obligation<'tcx, T>)
1198 where T: fmt::Display
1200 self.note_obligation_cause_code(err,
1201 &obligation.predicate,
1202 &obligation.cause.code);
1205 fn note_obligation_cause_code<T>(&self,
1206 err: &mut DiagnosticBuilder,
1208 cause_code: &ObligationCauseCode<'tcx>)
1209 where T: fmt::Display
1213 ObligationCauseCode::ExprAssignable |
1214 ObligationCauseCode::MatchExpressionArm { .. } |
1215 ObligationCauseCode::IfExpression |
1216 ObligationCauseCode::IfExpressionWithNoElse |
1217 ObligationCauseCode::EquatePredicate |
1218 ObligationCauseCode::MainFunctionType |
1219 ObligationCauseCode::StartFunctionType |
1220 ObligationCauseCode::IntrinsicType |
1221 ObligationCauseCode::MethodReceiver |
1222 ObligationCauseCode::ReturnNoExpression |
1223 ObligationCauseCode::MiscObligation => {
1225 ObligationCauseCode::SliceOrArrayElem => {
1226 err.note("slice and array elements must have `Sized` type");
1228 ObligationCauseCode::TupleElem => {
1229 err.note("only the last element of a tuple may have a dynamically sized type");
1231 ObligationCauseCode::ProjectionWf(data) => {
1232 err.note(&format!("required so that the projection `{}` is well-formed",
1235 ObligationCauseCode::ReferenceOutlivesReferent(ref_ty) => {
1236 err.note(&format!("required so that reference `{}` does not outlive its referent",
1239 ObligationCauseCode::ObjectTypeBound(object_ty, region) => {
1240 err.note(&format!("required so that the lifetime bound of `{}` for `{}` \
1242 region, object_ty));
1244 ObligationCauseCode::ItemObligation(item_def_id) => {
1245 let item_name = tcx.item_path_str(item_def_id);
1246 let msg = format!("required by `{}`", item_name);
1247 if let Some(sp) = tcx.hir.span_if_local(item_def_id) {
1248 let sp = tcx.sess.codemap().def_span(sp);
1249 err.span_note(sp, &msg);
1254 ObligationCauseCode::ObjectCastObligation(object_ty) => {
1255 err.note(&format!("required for the cast to the object type `{}`",
1256 self.ty_to_string(object_ty)));
1258 ObligationCauseCode::RepeatVec => {
1259 err.note("the `Copy` trait is required because the \
1260 repeated element will be copied");
1262 ObligationCauseCode::VariableType(_) => {
1263 err.note("all local variables must have a statically known size");
1265 ObligationCauseCode::SizedReturnType => {
1266 err.note("the return type of a function must have a \
1267 statically known size");
1269 ObligationCauseCode::SizedYieldType => {
1270 err.note("the yield type of a generator must have a \
1271 statically known size");
1273 ObligationCauseCode::AssignmentLhsSized => {
1274 err.note("the left-hand-side of an assignment must have a statically known size");
1276 ObligationCauseCode::TupleInitializerSized => {
1277 err.note("tuples must have a statically known size to be initialized");
1279 ObligationCauseCode::StructInitializerSized => {
1280 err.note("structs must have a statically known size to be initialized");
1282 ObligationCauseCode::FieldSized(ref item) => {
1284 AdtKind::Struct => {
1285 err.note("only the last field of a struct may have a dynamically \
1289 err.note("no field of a union may have a dynamically sized type");
1292 err.note("no field of an enum variant may have a dynamically sized type");
1296 ObligationCauseCode::ConstSized => {
1297 err.note("constant expressions must have a statically known size");
1299 ObligationCauseCode::SharedStatic => {
1300 err.note("shared static variables must have a type that implements `Sync`");
1302 ObligationCauseCode::BuiltinDerivedObligation(ref data) => {
1303 let parent_trait_ref = self.resolve_type_vars_if_possible(&data.parent_trait_ref);
1304 err.note(&format!("required because it appears within the type `{}`",
1305 parent_trait_ref.0.self_ty()));
1306 let parent_predicate = parent_trait_ref.to_predicate();
1307 self.note_obligation_cause_code(err,
1311 ObligationCauseCode::ImplDerivedObligation(ref data) => {
1312 let parent_trait_ref = self.resolve_type_vars_if_possible(&data.parent_trait_ref);
1314 &format!("required because of the requirements on the impl of `{}` for `{}`",
1316 parent_trait_ref.0.self_ty()));
1317 let parent_predicate = parent_trait_ref.to_predicate();
1318 self.note_obligation_cause_code(err,
1322 ObligationCauseCode::CompareImplMethodObligation { .. } => {
1324 &format!("the requirement `{}` appears on the impl method \
1325 but not on the corresponding trait method",
1328 ObligationCauseCode::ReturnType(_) |
1329 ObligationCauseCode::BlockTailExpression(_) => (),
1333 fn suggest_new_overflow_limit(&self, err: &mut DiagnosticBuilder) {
1334 let current_limit = self.tcx.sess.recursion_limit.get();
1335 let suggested_limit = current_limit * 2;
1336 err.help(&format!("consider adding a `#![recursion_limit=\"{}\"]` attribute to your crate",
1342 Arg(String, String),
1343 Tuple(Span, Vec<(String, String)>),
1347 fn empty() -> ArgKind {
1348 ArgKind::Arg("_".to_owned(), "_".to_owned())