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 OutputTypeParameterMismatch,
23 ObjectSafetyViolation,
26 use errors::DiagnosticBuilder;
27 use fmt_macros::{Parser, Piece, Position};
28 use hir::{intravisit, Local, Pat};
29 use hir::intravisit::{Visitor, NestedVisitorMap};
30 use hir::map::NodeExpr;
31 use hir::def_id::DefId;
32 use infer::{self, InferCtxt};
33 use infer::type_variable::TypeVariableOrigin;
34 use rustc::lint::builtin::EXTRA_REQUIREMENT_IN_IMPL;
37 use ty::{self, AdtKind, ToPredicate, ToPolyTraitRef, Ty, TyCtxt, TypeFoldable};
38 use ty::error::ExpectedFound;
40 use ty::fold::TypeFolder;
42 use util::nodemap::{FxHashMap, FxHashSet};
44 use syntax_pos::{DUMMY_SP, Span};
47 #[derive(Debug, PartialEq, Eq, Hash)]
48 pub struct TraitErrorKey<'tcx> {
50 predicate: ty::Predicate<'tcx>
53 impl<'a, 'gcx, 'tcx> TraitErrorKey<'tcx> {
54 fn from_error(infcx: &InferCtxt<'a, 'gcx, 'tcx>,
55 e: &FulfillmentError<'tcx>) -> Self {
57 infcx.resolve_type_vars_if_possible(&e.obligation.predicate);
59 span: e.obligation.cause.span,
60 predicate: infcx.tcx.erase_regions(&predicate)
65 struct FindLocalByTypeVisitor<'a, 'gcx: 'a + 'tcx, 'tcx: 'a> {
66 infcx: &'a InferCtxt<'a, 'gcx, 'tcx>,
67 target_ty: &'a Ty<'tcx>,
68 found_pattern: Option<&'a Pat>,
71 impl<'a, 'gcx, 'tcx> Visitor<'a> for FindLocalByTypeVisitor<'a, 'gcx, 'tcx> {
72 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'a> {
73 NestedVisitorMap::None
76 fn visit_local(&mut self, local: &'a Local) {
77 if let Some(&ty) = self.infcx.tables.borrow().node_types.get(&local.id) {
78 let ty = self.infcx.resolve_type_vars_if_possible(&ty);
79 let is_match = ty.walk().any(|t| t == *self.target_ty);
81 if is_match && self.found_pattern.is_none() {
82 self.found_pattern = Some(&*local.pat);
85 intravisit::walk_local(self, local);
89 impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
90 pub fn report_fulfillment_errors(&self, errors: &Vec<FulfillmentError<'tcx>>) {
92 self.report_fulfillment_error(error);
96 fn report_fulfillment_error(&self,
97 error: &FulfillmentError<'tcx>) {
98 let error_key = TraitErrorKey::from_error(self, error);
99 debug!("report_fulfillment_errors({:?}) - key={:?}",
101 if !self.reported_trait_errors.borrow_mut().insert(error_key) {
102 debug!("report_fulfillment_errors: skipping duplicate");
106 FulfillmentErrorCode::CodeSelectionError(ref e) => {
107 self.report_selection_error(&error.obligation, e);
109 FulfillmentErrorCode::CodeProjectionError(ref e) => {
110 self.report_projection_error(&error.obligation, e);
112 FulfillmentErrorCode::CodeAmbiguity => {
113 self.maybe_report_ambiguity(&error.obligation);
118 fn report_projection_error(&self,
119 obligation: &PredicateObligation<'tcx>,
120 error: &MismatchedProjectionTypes<'tcx>)
123 self.resolve_type_vars_if_possible(&obligation.predicate);
125 if predicate.references_error() {
131 let mut err = &error.err;
132 let mut values = None;
134 // try to find the mismatched types to report the error with.
136 // this can fail if the problem was higher-ranked, in which
137 // cause I have no idea for a good error message.
138 if let ty::Predicate::Projection(ref data) = predicate {
139 let mut selcx = SelectionContext::new(self);
140 let (data, _) = self.replace_late_bound_regions_with_fresh_var(
141 obligation.cause.span,
142 infer::LateBoundRegionConversionTime::HigherRankedType,
144 let normalized = super::normalize_projection_type(
147 obligation.cause.clone(),
150 if let Err(error) = self.eq_types(
151 false, &obligation.cause,
152 data.ty, normalized.value
154 values = Some(infer::ValuePairs::Types(ExpectedFound {
155 expected: normalized.value,
163 let mut diag = struct_span_err!(
164 self.tcx.sess, obligation.cause.span, E0271,
165 "type mismatch resolving `{}`", predicate
167 self.note_type_err(&mut diag, &obligation.cause, None, values, err);
168 self.note_obligation_cause(&mut diag, obligation);
173 fn fuzzy_match_tys(&self, a: Ty<'tcx>, b: Ty<'tcx>) -> bool {
174 /// returns the fuzzy category of a given type, or None
175 /// if the type can be equated to any type.
176 fn type_category<'tcx>(t: Ty<'tcx>) -> Option<u32> {
178 ty::TyBool => Some(0),
179 ty::TyChar => Some(1),
180 ty::TyStr => Some(2),
181 ty::TyInt(..) | ty::TyUint(..) | ty::TyInfer(ty::IntVar(..)) => Some(3),
182 ty::TyFloat(..) | ty::TyInfer(ty::FloatVar(..)) => Some(4),
183 ty::TyRef(..) | ty::TyRawPtr(..) => Some(5),
184 ty::TyArray(..) | ty::TySlice(..) => Some(6),
185 ty::TyFnDef(..) | ty::TyFnPtr(..) => Some(7),
186 ty::TyDynamic(..) => Some(8),
187 ty::TyClosure(..) => Some(9),
188 ty::TyTuple(..) => Some(10),
189 ty::TyProjection(..) => Some(11),
190 ty::TyParam(..) => Some(12),
191 ty::TyAnon(..) => Some(13),
192 ty::TyNever => Some(14),
193 ty::TyAdt(adt, ..) => match adt.adt_kind() {
194 AdtKind::Struct => Some(15),
195 AdtKind::Union => Some(16),
196 AdtKind::Enum => Some(17),
198 ty::TyInfer(..) | ty::TyError => None
202 match (type_category(a), type_category(b)) {
203 (Some(cat_a), Some(cat_b)) => match (&a.sty, &b.sty) {
204 (&ty::TyAdt(def_a, _), &ty::TyAdt(def_b, _)) => def_a == def_b,
207 // infer and error can be equated to all types
212 fn impl_similar_to(&self,
213 trait_ref: ty::PolyTraitRef<'tcx>,
214 obligation: &PredicateObligation<'tcx>)
219 let trait_ref = tcx.erase_late_bound_regions(&trait_ref);
220 let trait_self_ty = trait_ref.self_ty();
222 let mut self_match_impls = vec![];
223 let mut fuzzy_match_impls = vec![];
225 self.tcx.lookup_trait_def(trait_ref.def_id)
226 .for_each_relevant_impl(self.tcx, trait_self_ty, |def_id| {
227 let impl_substs = self.fresh_substs_for_item(obligation.cause.span, def_id);
228 let impl_trait_ref = tcx
229 .impl_trait_ref(def_id)
231 .subst(tcx, impl_substs);
233 let impl_self_ty = impl_trait_ref.self_ty();
235 if let Ok(..) = self.can_equate(&trait_self_ty, &impl_self_ty) {
236 self_match_impls.push(def_id);
238 if trait_ref.substs.types().skip(1)
239 .zip(impl_trait_ref.substs.types().skip(1))
240 .all(|(u,v)| self.fuzzy_match_tys(u, v))
242 fuzzy_match_impls.push(def_id);
247 let impl_def_id = if self_match_impls.len() == 1 {
249 } else if fuzzy_match_impls.len() == 1 {
255 if tcx.has_attr(impl_def_id, "rustc_on_unimplemented") {
262 fn on_unimplemented_note(&self,
263 trait_ref: ty::PolyTraitRef<'tcx>,
264 obligation: &PredicateObligation<'tcx>) -> Option<String> {
265 let def_id = self.impl_similar_to(trait_ref, obligation)
266 .unwrap_or(trait_ref.def_id());
267 let trait_ref = trait_ref.skip_binder();
269 let span = obligation.cause.span;
270 let mut report = None;
271 if let Some(item) = self.tcx
274 .filter(|a| a.check_name("rustc_on_unimplemented"))
277 let err_sp = item.span.substitute_dummy(span);
278 let trait_str = self.tcx.item_path_str(trait_ref.def_id);
279 if let Some(istring) = item.value_str() {
280 let istring = &*istring.as_str();
281 let generics = self.tcx.item_generics(trait_ref.def_id);
282 let generic_map = generics.types.iter().map(|param| {
283 (param.name.as_str().to_string(),
284 trait_ref.substs.type_for_def(param).to_string())
285 }).collect::<FxHashMap<String, String>>();
286 let parser = Parser::new(istring);
287 let mut errored = false;
288 let err: String = parser.filter_map(|p| {
290 Piece::String(s) => Some(s),
291 Piece::NextArgument(a) => match a.position {
292 Position::ArgumentNamed(s) => match generic_map.get(s) {
293 Some(val) => Some(val),
295 span_err!(self.tcx.sess, err_sp, E0272,
296 "the #[rustc_on_unimplemented] \
298 trait definition for {} refers to \
299 non-existent type parameter {}",
306 span_err!(self.tcx.sess, err_sp, E0273,
307 "the #[rustc_on_unimplemented] attribute \
308 on trait definition for {} must have \
309 named format arguments, eg \
310 `#[rustc_on_unimplemented = \
311 \"foo {{T}}\"]`", trait_str);
318 // Report only if the format string checks out
323 span_err!(self.tcx.sess, err_sp, E0274,
324 "the #[rustc_on_unimplemented] attribute on \
325 trait definition for {} must have a value, \
326 eg `#[rustc_on_unimplemented = \"foo\"]`",
333 fn find_similar_impl_candidates(&self,
334 trait_ref: ty::PolyTraitRef<'tcx>)
335 -> Vec<ty::TraitRef<'tcx>>
337 let simp = fast_reject::simplify_type(self.tcx,
338 trait_ref.skip_binder().self_ty(),
340 let mut impl_candidates = Vec::new();
341 let trait_def = self.tcx.lookup_trait_def(trait_ref.def_id());
344 Some(simp) => trait_def.for_each_impl(self.tcx, |def_id| {
345 let imp = self.tcx.impl_trait_ref(def_id).unwrap();
346 let imp_simp = fast_reject::simplify_type(self.tcx,
349 if let Some(imp_simp) = imp_simp {
350 if simp != imp_simp {
354 impl_candidates.push(imp);
356 None => trait_def.for_each_impl(self.tcx, |def_id| {
357 impl_candidates.push(
358 self.tcx.impl_trait_ref(def_id).unwrap());
364 fn report_similar_impl_candidates(&self,
365 impl_candidates: Vec<ty::TraitRef<'tcx>>,
366 err: &mut DiagnosticBuilder)
368 if impl_candidates.is_empty() {
372 let end = if impl_candidates.len() <= 5 {
373 impl_candidates.len()
377 err.help(&format!("the following implementations were found:{}{}",
378 &impl_candidates[0..end].iter().map(|candidate| {
379 format!("\n {:?}", candidate)
380 }).collect::<String>(),
381 if impl_candidates.len() > 5 {
382 format!("\nand {} others", impl_candidates.len() - 4)
389 /// Reports that an overflow has occurred and halts compilation. We
390 /// halt compilation unconditionally because it is important that
391 /// overflows never be masked -- they basically represent computations
392 /// whose result could not be truly determined and thus we can't say
393 /// if the program type checks or not -- and they are unusual
394 /// occurrences in any case.
395 pub fn report_overflow_error<T>(&self,
396 obligation: &Obligation<'tcx, T>,
397 suggest_increasing_limit: bool) -> !
398 where T: fmt::Display + TypeFoldable<'tcx>
401 self.resolve_type_vars_if_possible(&obligation.predicate);
402 let mut err = struct_span_err!(self.tcx.sess, obligation.cause.span, E0275,
403 "overflow evaluating the requirement `{}`",
406 if suggest_increasing_limit {
407 self.suggest_new_overflow_limit(&mut err);
410 self.note_obligation_cause(&mut err, obligation);
413 self.tcx.sess.abort_if_errors();
417 /// Reports that a cycle was detected which led to overflow and halts
418 /// compilation. This is equivalent to `report_overflow_error` except
419 /// that we can give a more helpful error message (and, in particular,
420 /// we do not suggest increasing the overflow limit, which is not
422 pub fn report_overflow_error_cycle(&self, cycle: &[PredicateObligation<'tcx>]) -> ! {
423 let cycle = self.resolve_type_vars_if_possible(&cycle.to_owned());
424 assert!(cycle.len() > 0);
426 debug!("report_overflow_error_cycle: cycle={:?}", cycle);
428 self.report_overflow_error(&cycle[0], false);
431 pub fn report_extra_impl_obligation(&self,
433 item_name: ast::Name,
434 _impl_item_def_id: DefId,
435 trait_item_def_id: DefId,
436 requirement: &fmt::Display,
437 lint_id: Option<ast::NodeId>) // (*)
438 -> DiagnosticBuilder<'tcx>
440 // (*) This parameter is temporary and used only for phasing
441 // in the bug fix to #18937. If it is `Some`, it has a kind of
442 // weird effect -- the diagnostic is reported as a lint, and
443 // the builder which is returned is marked as canceled.
446 struct_span_err!(self.tcx.sess,
449 "impl has stricter requirements than trait");
451 if let Some(trait_item_span) = self.tcx.hir.span_if_local(trait_item_def_id) {
452 err.span_label(trait_item_span,
453 &format!("definition of `{}` from trait", item_name));
458 &format!("impl has extra requirement {}", requirement));
460 if let Some(node_id) = lint_id {
461 self.tcx.sess.add_lint_diagnostic(EXTRA_REQUIREMENT_IN_IMPL,
471 /// Get the parent trait chain start
472 fn get_parent_trait_ref(&self, code: &ObligationCauseCode<'tcx>) -> Option<String> {
474 &ObligationCauseCode::BuiltinDerivedObligation(ref data) => {
475 let parent_trait_ref = self.resolve_type_vars_if_possible(
476 &data.parent_trait_ref);
477 match self.get_parent_trait_ref(&data.parent_code) {
479 None => Some(format!("{}", parent_trait_ref.0.self_ty())),
486 pub fn report_selection_error(&self,
487 obligation: &PredicateObligation<'tcx>,
488 error: &SelectionError<'tcx>)
490 let span = obligation.cause.span;
492 let mut err = match *error {
493 SelectionError::Unimplemented => {
494 if let ObligationCauseCode::CompareImplMethodObligation {
495 item_name, impl_item_def_id, trait_item_def_id, lint_id
496 } = obligation.cause.code {
497 self.report_extra_impl_obligation(
502 &format!("`{}`", obligation.predicate),
507 match obligation.predicate {
508 ty::Predicate::Trait(ref trait_predicate) => {
509 let trait_predicate =
510 self.resolve_type_vars_if_possible(trait_predicate);
512 if self.tcx.sess.has_errors() && trait_predicate.references_error() {
515 let trait_ref = trait_predicate.to_poly_trait_ref();
516 let (post_message, pre_message) =
517 self.get_parent_trait_ref(&obligation.cause.code)
518 .map(|t| (format!(" in `{}`", t), format!("within `{}`, ", t)))
519 .unwrap_or((String::new(), String::new()));
520 let mut err = struct_span_err!(
524 "the trait bound `{}` is not satisfied{}",
525 trait_ref.to_predicate(),
528 &format!("{}the trait `{}` is not \
529 implemented for `{}`",
532 trait_ref.self_ty()));
534 // Try to report a help message
536 if !trait_ref.has_infer_types() &&
537 self.predicate_can_apply(trait_ref) {
538 // If a where-clause may be useful, remind the
539 // user that they can add it.
541 // don't display an on-unimplemented note, as
542 // these notes will often be of the form
543 // "the type `T` can't be frobnicated"
544 // which is somewhat confusing.
545 err.help(&format!("consider adding a `where {}` bound",
546 trait_ref.to_predicate()));
547 } else if let Some(s) = self.on_unimplemented_note(trait_ref,
549 // If it has a custom "#[rustc_on_unimplemented]"
550 // error message, let's display it!
553 // If we can't show anything useful, try to find
555 let impl_candidates = self.find_similar_impl_candidates(trait_ref);
556 self.report_similar_impl_candidates(impl_candidates, &mut err);
561 ty::Predicate::Equate(ref predicate) => {
562 let predicate = self.resolve_type_vars_if_possible(predicate);
563 let err = self.equality_predicate(&obligation.cause,
564 &predicate).err().unwrap();
565 struct_span_err!(self.tcx.sess, span, E0278,
566 "the requirement `{}` is not satisfied (`{}`)",
570 ty::Predicate::RegionOutlives(ref predicate) => {
571 let predicate = self.resolve_type_vars_if_possible(predicate);
572 let err = self.region_outlives_predicate(&obligation.cause,
573 &predicate).err().unwrap();
574 struct_span_err!(self.tcx.sess, span, E0279,
575 "the requirement `{}` is not satisfied (`{}`)",
579 ty::Predicate::Projection(..) | ty::Predicate::TypeOutlives(..) => {
581 self.resolve_type_vars_if_possible(&obligation.predicate);
582 struct_span_err!(self.tcx.sess, span, E0280,
583 "the requirement `{}` is not satisfied",
587 ty::Predicate::ObjectSafe(trait_def_id) => {
588 let violations = self.tcx.object_safety_violations(trait_def_id);
589 self.tcx.report_object_safety_error(span,
594 ty::Predicate::ClosureKind(closure_def_id, kind) => {
595 let found_kind = self.closure_kind(closure_def_id).unwrap();
596 let closure_span = self.tcx.hir.span_if_local(closure_def_id).unwrap();
597 let mut err = struct_span_err!(
598 self.tcx.sess, closure_span, E0525,
599 "expected a closure that implements the `{}` trait, \
600 but this closure only implements `{}`",
604 obligation.cause.span,
605 &format!("the requirement to implement \
606 `{}` derives from here", kind));
611 ty::Predicate::WellFormed(ty) => {
612 // WF predicates cannot themselves make
613 // errors. They can only block due to
614 // ambiguity; otherwise, they always
615 // degenerate into other obligations
617 span_bug!(span, "WF predicate not satisfied for {:?}", ty);
622 OutputTypeParameterMismatch(ref expected_trait_ref, ref actual_trait_ref, ref e) => {
623 let expected_trait_ref = self.resolve_type_vars_if_possible(&*expected_trait_ref);
624 let actual_trait_ref = self.resolve_type_vars_if_possible(&*actual_trait_ref);
625 if actual_trait_ref.self_ty().references_error() {
628 struct_span_err!(self.tcx.sess, span, E0281,
629 "type mismatch: the type `{}` implements the trait `{}`, \
630 but the trait `{}` is required ({})",
631 expected_trait_ref.self_ty(),
637 TraitNotObjectSafe(did) => {
638 let violations = self.tcx.object_safety_violations(did);
639 self.tcx.report_object_safety_error(span, did,
643 self.note_obligation_cause(&mut err, obligation);
648 impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
649 pub fn recursive_type_with_infinite_size_error(self,
651 -> DiagnosticBuilder<'tcx>
653 assert!(type_def_id.is_local());
654 let span = self.hir.span_if_local(type_def_id).unwrap();
655 let mut err = struct_span_err!(self.sess, span, E0072,
656 "recursive type `{}` has infinite size",
657 self.item_path_str(type_def_id));
658 err.span_label(span, &format!("recursive type has infinite size"));
659 err.help(&format!("insert indirection (e.g., a `Box`, `Rc`, or `&`) \
660 at some point to make `{}` representable",
661 self.item_path_str(type_def_id)));
665 pub fn report_object_safety_error(self,
668 violations: Vec<ObjectSafetyViolation>)
669 -> DiagnosticBuilder<'tcx>
671 let trait_str = self.item_path_str(trait_def_id);
672 let mut err = struct_span_err!(
673 self.sess, span, E0038,
674 "the trait `{}` cannot be made into an object",
676 err.span_label(span, &format!(
677 "the trait `{}` cannot be made into an object", trait_str
680 let mut reported_violations = FxHashSet();
681 for violation in violations {
682 if !reported_violations.insert(violation.clone()) {
685 err.note(&violation.error_msg());
691 impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
692 fn maybe_report_ambiguity(&self, obligation: &PredicateObligation<'tcx>) {
693 // Unable to successfully determine, probably means
694 // insufficient type information, but could mean
695 // ambiguous impls. The latter *ought* to be a
696 // coherence violation, so we don't report it here.
698 let predicate = self.resolve_type_vars_if_possible(&obligation.predicate);
700 debug!("maybe_report_ambiguity(predicate={:?}, obligation={:?})",
704 // Ambiguity errors are often caused as fallout from earlier
705 // errors. So just ignore them if this infcx is tainted.
706 if self.is_tainted_by_errors() {
711 ty::Predicate::Trait(ref data) => {
712 let trait_ref = data.to_poly_trait_ref();
713 let self_ty = trait_ref.self_ty();
714 if predicate.references_error() {
717 // Typically, this ambiguity should only happen if
718 // there are unresolved type inference variables
719 // (otherwise it would suggest a coherence
720 // failure). But given #21974 that is not necessarily
721 // the case -- we can have multiple where clauses that
722 // are only distinguished by a region, which results
723 // in an ambiguity even when all types are fully
724 // known, since we don't dispatch based on region
727 // This is kind of a hack: it frequently happens that some earlier
728 // error prevents types from being fully inferred, and then we get
729 // a bunch of uninteresting errors saying something like "<generic
730 // #0> doesn't implement Sized". It may even be true that we
731 // could just skip over all checks where the self-ty is an
732 // inference variable, but I was afraid that there might be an
733 // inference variable created, registered as an obligation, and
734 // then never forced by writeback, and hence by skipping here we'd
735 // be ignoring the fact that we don't KNOW the type works
736 // out. Though even that would probably be harmless, given that
737 // we're only talking about builtin traits, which are known to be
738 // inhabited. But in any case I just threw in this check for
739 // has_errors() to be sure that compilation isn't happening
740 // anyway. In that case, why inundate the user.
741 if !self.tcx.sess.has_errors() {
743 self.tcx.lang_items.sized_trait()
744 .map_or(false, |sized_id| sized_id == trait_ref.def_id())
746 self.need_type_info(obligation, self_ty);
748 let mut err = struct_span_err!(self.tcx.sess,
749 obligation.cause.span, E0283,
750 "type annotations required: \
751 cannot resolve `{}`",
753 self.note_obligation_cause(&mut err, obligation);
759 ty::Predicate::WellFormed(ty) => {
760 // Same hacky approach as above to avoid deluging user
761 // with error messages.
762 if !ty.references_error() && !self.tcx.sess.has_errors() {
763 self.need_type_info(obligation, ty);
768 if !self.tcx.sess.has_errors() {
769 let mut err = struct_span_err!(self.tcx.sess,
770 obligation.cause.span, E0284,
771 "type annotations required: \
772 cannot resolve `{}`",
774 self.note_obligation_cause(&mut err, obligation);
781 /// Returns whether the trait predicate may apply for *some* assignment
782 /// to the type parameters.
783 fn predicate_can_apply(&self, pred: ty::PolyTraitRef<'tcx>) -> bool {
784 struct ParamToVarFolder<'a, 'gcx: 'a+'tcx, 'tcx: 'a> {
785 infcx: &'a InferCtxt<'a, 'gcx, 'tcx>,
786 var_map: FxHashMap<Ty<'tcx>, Ty<'tcx>>
789 impl<'a, 'gcx, 'tcx> TypeFolder<'gcx, 'tcx> for ParamToVarFolder<'a, 'gcx, 'tcx> {
790 fn tcx<'b>(&'b self) -> TyCtxt<'b, 'gcx, 'tcx> { self.infcx.tcx }
792 fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> {
793 if let ty::TyParam(ty::ParamTy {name, ..}) = ty.sty {
794 let infcx = self.infcx;
795 self.var_map.entry(ty).or_insert_with(||
797 TypeVariableOrigin::TypeParameterDefinition(DUMMY_SP, name)))
799 ty.super_fold_with(self)
805 let mut selcx = SelectionContext::new(self);
807 let cleaned_pred = pred.fold_with(&mut ParamToVarFolder {
812 let cleaned_pred = super::project::normalize(
814 ObligationCause::dummy(),
818 let obligation = Obligation::new(
819 ObligationCause::dummy(),
820 cleaned_pred.to_predicate()
823 selcx.evaluate_obligation(&obligation)
827 fn extract_type_name(&self, ty: &'a Ty<'tcx>) -> String {
828 if let ty::TyInfer(ty::TyVar(ty_vid)) = (*ty).sty {
829 let ty_vars = self.type_variables.borrow();
830 if let TypeVariableOrigin::TypeParameterDefinition(_, name) =
831 *ty_vars.var_origin(ty_vid) {
841 fn need_type_info(&self, obligation: &PredicateObligation<'tcx>, ty: Ty<'tcx>) {
842 let ty = self.resolve_type_vars_if_possible(&ty);
843 let name = self.extract_type_name(&ty);
844 let ref cause = obligation.cause;
846 let mut err = struct_span_err!(self.tcx.sess,
849 "type annotations needed");
851 err.span_label(cause.span, &format!("cannot infer type for `{}`", name));
853 let mut local_visitor = FindLocalByTypeVisitor {
859 // #40294: cause.body_id can also be a fn declaration.
860 // Currently, if it's anything other than NodeExpr, we just ignore it
861 match self.tcx.hir.find(cause.body_id) {
862 Some(NodeExpr(expr)) => local_visitor.visit_expr(expr),
866 if let Some(pattern) = local_visitor.found_pattern {
867 let pattern_span = pattern.span;
868 if let Some(simple_name) = pattern.simple_name() {
869 err.span_label(pattern_span,
870 &format!("consider giving `{}` a type",
873 err.span_label(pattern_span, &format!("consider giving a type to pattern"));
880 fn note_obligation_cause<T>(&self,
881 err: &mut DiagnosticBuilder,
882 obligation: &Obligation<'tcx, T>)
883 where T: fmt::Display
885 self.note_obligation_cause_code(err,
886 &obligation.predicate,
887 &obligation.cause.code);
890 fn note_obligation_cause_code<T>(&self,
891 err: &mut DiagnosticBuilder,
893 cause_code: &ObligationCauseCode<'tcx>)
894 where T: fmt::Display
898 ObligationCauseCode::ExprAssignable |
899 ObligationCauseCode::MatchExpressionArm { .. } |
900 ObligationCauseCode::IfExpression |
901 ObligationCauseCode::IfExpressionWithNoElse |
902 ObligationCauseCode::EquatePredicate |
903 ObligationCauseCode::MainFunctionType |
904 ObligationCauseCode::StartFunctionType |
905 ObligationCauseCode::IntrinsicType |
906 ObligationCauseCode::MethodReceiver |
907 ObligationCauseCode::MiscObligation => {
909 ObligationCauseCode::SliceOrArrayElem => {
910 err.note("slice and array elements must have `Sized` type");
912 ObligationCauseCode::TupleElem => {
913 err.note("tuple elements must have `Sized` type");
915 ObligationCauseCode::ProjectionWf(data) => {
916 err.note(&format!("required so that the projection `{}` is well-formed",
919 ObligationCauseCode::ReferenceOutlivesReferent(ref_ty) => {
920 err.note(&format!("required so that reference `{}` does not outlive its referent",
923 ObligationCauseCode::ObjectTypeBound(object_ty, region) => {
924 err.note(&format!("required so that the lifetime bound of `{}` for `{}` \
928 ObligationCauseCode::ItemObligation(item_def_id) => {
929 let item_name = tcx.item_path_str(item_def_id);
930 err.note(&format!("required by `{}`", item_name));
932 ObligationCauseCode::ObjectCastObligation(object_ty) => {
933 err.note(&format!("required for the cast to the object type `{}`",
934 self.ty_to_string(object_ty)));
936 ObligationCauseCode::RepeatVec => {
937 err.note("the `Copy` trait is required because the \
938 repeated element will be copied");
940 ObligationCauseCode::VariableType(_) => {
941 err.note("all local variables must have a statically known size");
943 ObligationCauseCode::ReturnType => {
944 err.note("the return type of a function must have a \
945 statically known size");
947 ObligationCauseCode::AssignmentLhsSized => {
948 err.note("the left-hand-side of an assignment must have a statically known size");
950 ObligationCauseCode::StructInitializerSized => {
951 err.note("structs must have a statically known size to be initialized");
953 ObligationCauseCode::FieldSized => {
954 err.note("only the last field of a struct may have a dynamically sized type");
956 ObligationCauseCode::ConstSized => {
957 err.note("constant expressions must have a statically known size");
959 ObligationCauseCode::SharedStatic => {
960 err.note("shared static variables must have a type that implements `Sync`");
962 ObligationCauseCode::BuiltinDerivedObligation(ref data) => {
963 let parent_trait_ref = self.resolve_type_vars_if_possible(&data.parent_trait_ref);
964 err.note(&format!("required because it appears within the type `{}`",
965 parent_trait_ref.0.self_ty()));
966 let parent_predicate = parent_trait_ref.to_predicate();
967 self.note_obligation_cause_code(err,
971 ObligationCauseCode::ImplDerivedObligation(ref data) => {
972 let parent_trait_ref = self.resolve_type_vars_if_possible(&data.parent_trait_ref);
974 &format!("required because of the requirements on the impl of `{}` for `{}`",
976 parent_trait_ref.0.self_ty()));
977 let parent_predicate = parent_trait_ref.to_predicate();
978 self.note_obligation_cause_code(err,
982 ObligationCauseCode::CompareImplMethodObligation { .. } => {
984 &format!("the requirement `{}` appears on the impl method \
985 but not on the corresponding trait method",
991 fn suggest_new_overflow_limit(&self, err: &mut DiagnosticBuilder) {
992 let current_limit = self.tcx.sess.recursion_limit.get();
993 let suggested_limit = current_limit * 2;
995 "consider adding a `#![recursion_limit=\"{}\"]` attribute to your crate",