1 // Copyright 2012-2013 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.
11 //! Error Reporting Code for the inference engine
13 //! Because of the way inference, and in particular region inference,
14 //! works, it often happens that errors are not detected until far after
15 //! the relevant line of code has been type-checked. Therefore, there is
16 //! an elaborate system to track why a particular constraint in the
17 //! inference graph arose so that we can explain to the user what gave
18 //! rise to a particular error.
20 //! The basis of the system are the "origin" types. An "origin" is the
21 //! reason that a constraint or inference variable arose. There are
22 //! different "origin" enums for different kinds of constraints/variables
23 //! (e.g., `TypeOrigin`, `RegionVariableOrigin`). An origin always has
24 //! a span, but also more information so that we can generate a meaningful
27 //! Having a catalogue of all the different reasons an error can arise is
28 //! also useful for other reasons, like cross-referencing FAQs etc, though
29 //! we are not really taking advantage of this yet.
31 //! # Region Inference
33 //! Region inference is particularly tricky because it always succeeds "in
34 //! the moment" and simply registers a constraint. Then, at the end, we
35 //! can compute the full graph and report errors, so we need to be able to
36 //! store and later report what gave rise to the conflicting constraints.
40 //! Determining whether `T1 <: T2` often involves a number of subtypes and
41 //! subconstraints along the way. A "TypeTrace" is an extended version
42 //! of an origin that traces the types and other values that were being
43 //! compared. It is not necessarily comprehensive (in fact, at the time of
44 //! this writing it only tracks the root values being compared) but I'd
45 //! like to extend it to include significant "waypoints". For example, if
46 //! you are comparing `(T1, T2) <: (T3, T4)`, and the problem is that `T2
47 //! <: T4` fails, I'd like the trace to include enough information to say
48 //! "in the 2nd element of the tuple". Similarly, failures when comparing
49 //! arguments or return types in fn types should be able to cite the
50 //! specific position, etc.
54 //! Of course, there is still a LOT of code in typeck that has yet to be
55 //! ported to this system, and which relies on string concatenation at the
56 //! time of error detection.
58 use self::FreshOrKept::*;
62 use super::SubregionOrigin;
63 use super::RegionVariableOrigin;
64 use super::ValuePairs;
65 use super::region_inference::RegionResolutionError;
66 use super::region_inference::ConcreteFailure;
67 use super::region_inference::SubSupConflict;
68 use super::region_inference::GenericBoundFailure;
69 use super::region_inference::GenericKind;
70 use super::region_inference::ProcessedErrors;
71 use super::region_inference::SameRegions;
73 use std::collections::HashSet;
75 use front::map as ast_map;
77 use rustc_front::print::pprust;
79 use middle::cstore::CrateStore;
81 use middle::def_id::DefId;
82 use middle::infer::{self, TypeOrigin};
85 use middle::ty::{self, Ty, HasTypeFlags};
86 use middle::ty::{Region, ReFree};
87 use middle::ty::error::TypeError;
89 use std::cell::{Cell, RefCell};
90 use std::char::from_u32;
93 use syntax::owned_slice::OwnedSlice;
94 use syntax::codemap::{self, Pos, Span};
95 use syntax::parse::token;
98 impl<'tcx> ty::ctxt<'tcx> {
99 pub fn note_and_explain_region(&self,
103 fn item_scope_tag(item: &hir::Item) -> &'static str {
105 hir::ItemImpl(..) => "impl",
106 hir::ItemStruct(..) => "struct",
107 hir::ItemEnum(..) => "enum",
108 hir::ItemTrait(..) => "trait",
109 hir::ItemFn(..) => "function body",
114 fn explain_span(tcx: &ty::ctxt, heading: &str, span: Span)
115 -> (String, Option<Span>) {
116 let lo = tcx.sess.codemap().lookup_char_pos_adj(span.lo);
117 (format!("the {} at {}:{}", heading, lo.line, lo.col.to_usize()),
121 let (description, span) = match region {
122 ty::ReScope(scope) => {
124 let unknown_scope = || {
125 format!("{}unknown scope: {:?}{}. Please report a bug.",
126 prefix, scope, suffix)
128 let span = match scope.span(&self.region_maps, &self.map) {
130 None => return self.sess.note(&unknown_scope())
132 let tag = match self.map.find(scope.node_id(&self.region_maps)) {
133 Some(ast_map::NodeBlock(_)) => "block",
134 Some(ast_map::NodeExpr(expr)) => match expr.node {
135 hir::ExprCall(..) => "call",
136 hir::ExprMethodCall(..) => "method call",
137 hir::ExprMatch(_, _, hir::MatchSource::IfLetDesugar { .. }) => "if let",
138 hir::ExprMatch(_, _, hir::MatchSource::WhileLetDesugar) => "while let",
139 hir::ExprMatch(_, _, hir::MatchSource::ForLoopDesugar) => "for",
140 hir::ExprMatch(..) => "match",
143 Some(ast_map::NodeStmt(_)) => "statement",
144 Some(ast_map::NodeItem(it)) => item_scope_tag(&*it),
146 return self.sess.span_note(span, &unknown_scope());
149 let scope_decorated_tag = match self.region_maps.code_extent_data(scope) {
150 region::CodeExtentData::Misc(_) => tag,
151 region::CodeExtentData::ParameterScope { .. } => {
152 "scope of parameters for function"
154 region::CodeExtentData::DestructionScope(_) => {
155 new_string = format!("destruction scope surrounding {}", tag);
158 region::CodeExtentData::Remainder(r) => {
159 new_string = format!("block suffix following statement {}",
160 r.first_statement_index);
164 explain_span(self, scope_decorated_tag, span)
167 ty::ReFree(ref fr) => {
168 let prefix = match fr.bound_region {
170 format!("the anonymous lifetime #{} defined on", idx + 1)
172 ty::BrFresh(_) => "an anonymous lifetime defined on".to_owned(),
174 format!("the lifetime {} as defined on",
179 match self.map.find(fr.scope.node_id(&self.region_maps)) {
180 Some(ast_map::NodeBlock(ref blk)) => {
181 let (msg, opt_span) = explain_span(self, "block", blk.span);
182 (format!("{} {}", prefix, msg), opt_span)
184 Some(ast_map::NodeItem(it)) => {
185 let tag = item_scope_tag(&*it);
186 let (msg, opt_span) = explain_span(self, tag, it.span);
187 (format!("{} {}", prefix, msg), opt_span)
190 // this really should not happen, but it does:
192 (format!("{} unknown free region bounded by scope {:?}",
193 prefix, fr.scope), None)
198 ty::ReStatic => ("the static lifetime".to_owned(), None),
200 ty::ReEmpty => ("the empty lifetime".to_owned(), None),
202 ty::ReEarlyBound(ref data) => (data.name.to_string(), None),
204 // FIXME(#13998) ReSkolemized should probably print like
205 // ReFree rather than dumping Debug output on the user.
207 // We shouldn't really be having unification failures with ReVar
208 // and ReLateBound though.
209 ty::ReSkolemized(..) | ty::ReVar(_) | ty::ReLateBound(..) => {
210 (format!("lifetime {:?}", region), None)
213 let message = format!("{}{}{}", prefix, description, suffix);
214 if let Some(span) = span {
215 self.sess.span_note(span, &message);
217 self.sess.note(&message);
222 pub trait ErrorReporting<'tcx> {
223 fn report_region_errors(&self,
224 errors: &Vec<RegionResolutionError<'tcx>>);
226 fn process_errors(&self, errors: &Vec<RegionResolutionError<'tcx>>)
227 -> Vec<RegionResolutionError<'tcx>>;
229 fn report_type_error(&self, trace: TypeTrace<'tcx>, terr: &TypeError<'tcx>);
231 fn check_and_note_conflicting_crates(&self, terr: &TypeError<'tcx>, sp: Span);
233 fn report_and_explain_type_error(&self,
234 trace: TypeTrace<'tcx>,
235 terr: &TypeError<'tcx>);
237 fn values_str(&self, values: &ValuePairs<'tcx>) -> Option<String>;
239 fn expected_found_str<T: fmt::Display + Resolvable<'tcx> + HasTypeFlags>(
241 exp_found: &ty::error::ExpectedFound<T>)
244 fn report_concrete_failure(&self,
245 origin: SubregionOrigin<'tcx>,
249 fn report_generic_bound_failure(&self,
250 origin: SubregionOrigin<'tcx>,
251 kind: GenericKind<'tcx>,
254 fn report_sub_sup_conflict(&self,
255 var_origin: RegionVariableOrigin,
256 sub_origin: SubregionOrigin<'tcx>,
258 sup_origin: SubregionOrigin<'tcx>,
261 fn report_processed_errors(&self,
262 var_origin: &[RegionVariableOrigin],
263 trace_origin: &[(TypeTrace<'tcx>, TypeError<'tcx>)],
264 same_regions: &[SameRegions]);
266 fn give_suggestion(&self, same_regions: &[SameRegions]);
269 trait ErrorReportingHelpers<'tcx> {
270 fn report_inference_failure(&self,
271 var_origin: RegionVariableOrigin);
273 fn note_region_origin(&self,
274 origin: &SubregionOrigin<'tcx>);
276 fn give_expl_lifetime_param(&self,
278 unsafety: hir::Unsafety,
279 constness: hir::Constness,
281 opt_explicit_self: Option<&hir::ExplicitSelf_>,
282 generics: &hir::Generics,
286 impl<'a, 'tcx> ErrorReporting<'tcx> for InferCtxt<'a, 'tcx> {
287 fn report_region_errors(&self,
288 errors: &Vec<RegionResolutionError<'tcx>>) {
289 let p_errors = self.process_errors(errors);
290 let errors = if p_errors.is_empty() { errors } else { &p_errors };
291 for error in errors {
292 match error.clone() {
293 ConcreteFailure(origin, sub, sup) => {
294 self.report_concrete_failure(origin, sub, sup);
297 GenericBoundFailure(kind, param_ty, sub) => {
298 self.report_generic_bound_failure(kind, param_ty, sub);
301 SubSupConflict(var_origin,
303 sup_origin, sup_r) => {
304 self.report_sub_sup_conflict(var_origin,
309 ProcessedErrors(ref var_origins,
311 ref same_regions) => {
312 if !same_regions.is_empty() {
313 self.report_processed_errors(&var_origins[..],
322 // This method goes through all the errors and try to group certain types
323 // of error together, for the purpose of suggesting explicit lifetime
324 // parameters to the user. This is done so that we can have a more
325 // complete view of what lifetimes should be the same.
326 // If the return value is an empty vector, it means that processing
327 // failed (so the return value of this method should not be used)
328 fn process_errors(&self, errors: &Vec<RegionResolutionError<'tcx>>)
329 -> Vec<RegionResolutionError<'tcx>> {
330 debug!("process_errors()");
331 let mut var_origins = Vec::new();
332 let mut trace_origins = Vec::new();
333 let mut same_regions = Vec::new();
334 let mut processed_errors = Vec::new();
335 for error in errors {
336 match error.clone() {
337 ConcreteFailure(origin, sub, sup) => {
338 debug!("processing ConcreteFailure");
339 let trace = match origin {
340 infer::Subtype(trace) => Some(trace),
343 match free_regions_from_same_fn(self.tcx, sub, sup) {
344 Some(ref same_frs) if trace.is_some() => {
345 let trace = trace.unwrap();
346 let terr = TypeError::RegionsDoesNotOutlive(sup,
348 trace_origins.push((trace, terr));
349 append_to_same_regions(&mut same_regions, same_frs);
351 _ => processed_errors.push((*error).clone()),
354 SubSupConflict(var_origin, _, sub_r, _, sup_r) => {
355 debug!("processing SubSupConflict sub: {:?} sup: {:?}", sub_r, sup_r);
356 match free_regions_from_same_fn(self.tcx, sub_r, sup_r) {
357 Some(ref same_frs) => {
358 var_origins.push(var_origin);
359 append_to_same_regions(&mut same_regions, same_frs);
361 None => processed_errors.push((*error).clone()),
364 _ => () // This shouldn't happen
367 if !same_regions.is_empty() {
368 let common_scope_id = same_regions[0].scope_id;
369 for sr in &same_regions {
370 // Since ProcessedErrors is used to reconstruct the function
371 // declaration, we want to make sure that they are, in fact,
372 // from the same scope
373 if sr.scope_id != common_scope_id {
374 debug!("returning empty result from process_errors because
375 {} != {}", sr.scope_id, common_scope_id);
379 let pe = ProcessedErrors(var_origins, trace_origins, same_regions);
380 debug!("errors processed: {:?}", pe);
381 processed_errors.push(pe);
383 return processed_errors;
386 struct FreeRegionsFromSameFn {
387 sub_fr: ty::FreeRegion,
388 sup_fr: ty::FreeRegion,
389 scope_id: ast::NodeId
392 impl FreeRegionsFromSameFn {
393 fn new(sub_fr: ty::FreeRegion,
394 sup_fr: ty::FreeRegion,
395 scope_id: ast::NodeId)
396 -> FreeRegionsFromSameFn {
397 FreeRegionsFromSameFn {
405 fn free_regions_from_same_fn(tcx: &ty::ctxt,
408 -> Option<FreeRegionsFromSameFn> {
409 debug!("free_regions_from_same_fn(sub={:?}, sup={:?})", sub, sup);
410 let (scope_id, fr1, fr2) = match (sub, sup) {
411 (ReFree(fr1), ReFree(fr2)) => {
412 if fr1.scope != fr2.scope {
415 assert!(fr1.scope == fr2.scope);
416 (fr1.scope.node_id(&tcx.region_maps), fr1, fr2)
420 let parent = tcx.map.get_parent(scope_id);
421 let parent_node = tcx.map.find(parent);
423 Some(node) => match node {
424 ast_map::NodeItem(item) => match item.node {
426 Some(FreeRegionsFromSameFn::new(fr1, fr2, scope_id))
430 ast_map::NodeImplItem(..) |
431 ast_map::NodeTraitItem(..) => {
432 Some(FreeRegionsFromSameFn::new(fr1, fr2, scope_id))
437 debug!("no parent node of scope_id {}", scope_id);
443 fn append_to_same_regions(same_regions: &mut Vec<SameRegions>,
444 same_frs: &FreeRegionsFromSameFn) {
445 let scope_id = same_frs.scope_id;
446 let (sub_fr, sup_fr) = (same_frs.sub_fr, same_frs.sup_fr);
447 for sr in &mut *same_regions {
448 if sr.contains(&sup_fr.bound_region)
449 && scope_id == sr.scope_id {
450 sr.push(sub_fr.bound_region);
454 same_regions.push(SameRegions {
456 regions: vec!(sub_fr.bound_region, sup_fr.bound_region)
461 fn report_type_error(&self, trace: TypeTrace<'tcx>, terr: &TypeError<'tcx>) {
462 let expected_found_str = match self.values_str(&trace.values) {
465 return; /* derived error */
469 span_err!(self.tcx.sess, trace.origin.span(), E0308,
475 self.check_and_note_conflicting_crates(terr, trace.origin.span());
478 TypeOrigin::MatchExpressionArm(_, arm_span, source) => match source {
479 hir::MatchSource::IfLetDesugar{..} =>
480 self.tcx.sess.span_note(arm_span, "`if let` arm with an incompatible type"),
481 _ => self.tcx.sess.span_note(arm_span, "match arm with an incompatible type"),
487 /// Adds a note if the types come from similarly named crates
488 fn check_and_note_conflicting_crates(&self, terr: &TypeError<'tcx>, sp: Span) {
489 let report_path_match = |did1: DefId, did2: DefId| {
490 // Only external crates, if either is from a local
491 // module we could have false positives
492 if !(did1.is_local() || did2.is_local()) && did1.krate != did2.krate {
493 let exp_path = self.tcx.with_path(did1,
494 |p| p.map(|x| x.to_string())
495 .collect::<Vec<_>>());
496 let found_path = self.tcx.with_path(did2,
497 |p| p.map(|x| x.to_string())
498 .collect::<Vec<_>>());
499 // We compare strings because PathMod and PathName can be different
500 // for imported and non-imported crates
501 if exp_path == found_path {
502 let crate_name = self.tcx.sess.cstore.crate_name(did1.krate);
503 self.tcx.sess.span_note(sp, &format!("Perhaps two different versions \
504 of crate `{}` are being used?",
510 TypeError::Sorts(ref exp_found) => {
511 // if they are both "path types", there's a chance of ambiguity
512 // due to different versions of the same crate
513 match (&exp_found.expected.sty, &exp_found.found.sty) {
514 (&ty::TyEnum(ref exp_adt, _), &ty::TyEnum(ref found_adt, _)) |
515 (&ty::TyStruct(ref exp_adt, _), &ty::TyStruct(ref found_adt, _)) |
516 (&ty::TyEnum(ref exp_adt, _), &ty::TyStruct(ref found_adt, _)) |
517 (&ty::TyStruct(ref exp_adt, _), &ty::TyEnum(ref found_adt, _)) => {
518 report_path_match(exp_adt.did, found_adt.did);
523 TypeError::Traits(ref exp_found) => {
524 report_path_match(exp_found.expected, exp_found.found);
526 _ => () // FIXME(#22750) handle traits and stuff
530 fn report_and_explain_type_error(&self,
531 trace: TypeTrace<'tcx>,
532 terr: &TypeError<'tcx>) {
533 let span = trace.origin.span();
534 self.report_type_error(trace, terr);
535 self.tcx.note_and_explain_type_err(terr, span);
538 /// Returns a string of the form "expected `{}`, found `{}`", or None if this is a derived
540 fn values_str(&self, values: &ValuePairs<'tcx>) -> Option<String> {
542 infer::Types(ref exp_found) => self.expected_found_str(exp_found),
543 infer::TraitRefs(ref exp_found) => self.expected_found_str(exp_found),
544 infer::PolyTraitRefs(ref exp_found) => self.expected_found_str(exp_found)
548 fn expected_found_str<T: fmt::Display + Resolvable<'tcx> + HasTypeFlags>(
550 exp_found: &ty::error::ExpectedFound<T>)
553 let expected = exp_found.expected.resolve(self);
554 if expected.references_error() {
558 let found = exp_found.found.resolve(self);
559 if found.references_error() {
563 Some(format!("expected `{}`, found `{}`",
568 fn report_generic_bound_failure(&self,
569 origin: SubregionOrigin<'tcx>,
570 bound_kind: GenericKind<'tcx>,
573 // FIXME: it would be better to report the first error message
574 // with the span of the parameter itself, rather than the span
575 // where the error was detected. But that span is not readily
578 let is_warning = match origin {
579 infer::RFC1214Subregion(_) => true,
583 let labeled_user_string = match bound_kind {
584 GenericKind::Param(ref p) =>
585 format!("the parameter type `{}`", p),
586 GenericKind::Projection(ref p) =>
587 format!("the associated type `{}`", p),
591 ty::ReFree(ty::FreeRegion {bound_region: ty::BrNamed(..), ..}) => {
592 // Does the required lifetime have a nice name we can print?
594 is_warning, self.tcx.sess, origin.span(), E0309,
595 "{} may not live long enough", labeled_user_string);
596 self.tcx.sess.fileline_help(
599 "consider adding an explicit lifetime bound `{}: {}`...",
605 // Does the required lifetime have a nice name we can print?
607 is_warning, self.tcx.sess, origin.span(), E0310,
608 "{} may not live long enough", labeled_user_string);
609 self.tcx.sess.fileline_help(
612 "consider adding an explicit lifetime bound `{}: 'static`...",
617 // If not, be less specific.
619 is_warning, self.tcx.sess, origin.span(), E0311,
620 "{} may not live long enough",
621 labeled_user_string);
622 self.tcx.sess.fileline_help(
625 "consider adding an explicit lifetime bound for `{}`",
627 self.tcx.note_and_explain_region(
628 &format!("{} must be valid for ", labeled_user_string),
635 self.tcx.sess.note_rfc_1214(origin.span());
638 self.note_region_origin(&origin);
641 fn report_concrete_failure(&self,
642 origin: SubregionOrigin<'tcx>,
646 infer::RFC1214Subregion(ref suborigin) => {
647 // Ideally, this would be a warning, but it doesn't
648 // seem to come up in practice, since the changes from
649 // RFC1214 mostly trigger errors in type definitions
650 // that don't wind up coming down this path.
651 self.report_concrete_failure((**suborigin).clone(), sub, sup);
653 infer::Subtype(trace) => {
654 let terr = TypeError::RegionsDoesNotOutlive(sup, sub);
655 self.report_and_explain_type_error(trace, &terr);
657 infer::Reborrow(span) => {
658 span_err!(self.tcx.sess, span, E0312,
659 "lifetime of reference outlines \
660 lifetime of borrowed content...");
661 self.tcx.note_and_explain_region(
662 "...the reference is valid for ",
665 self.tcx.note_and_explain_region(
666 "...but the borrowed content is only valid for ",
670 infer::ReborrowUpvar(span, ref upvar_id) => {
671 span_err!(self.tcx.sess, span, E0313,
672 "lifetime of borrowed pointer outlives \
673 lifetime of captured variable `{}`...",
674 self.tcx.local_var_name_str(upvar_id.var_id));
675 self.tcx.note_and_explain_region(
676 "...the borrowed pointer is valid for ",
679 self.tcx.note_and_explain_region(
680 &format!("...but `{}` is only valid for ",
681 self.tcx.local_var_name_str(upvar_id.var_id)),
685 infer::InfStackClosure(span) => {
686 span_err!(self.tcx.sess, span, E0314,
687 "closure outlives stack frame");
688 self.tcx.note_and_explain_region(
689 "...the closure must be valid for ",
692 self.tcx.note_and_explain_region(
693 "...but the closure's stack frame is only valid for ",
697 infer::InvokeClosure(span) => {
698 span_err!(self.tcx.sess, span, E0315,
699 "cannot invoke closure outside of its lifetime");
700 self.tcx.note_and_explain_region(
701 "the closure is only valid for ",
705 infer::DerefPointer(span) => {
706 span_err!(self.tcx.sess, span, E0473,
707 "dereference of reference outside its lifetime");
708 self.tcx.note_and_explain_region(
709 "the reference is only valid for ",
713 infer::FreeVariable(span, id) => {
714 span_err!(self.tcx.sess, span, E0474,
715 "captured variable `{}` does not outlive the enclosing closure",
716 self.tcx.local_var_name_str(id));
717 self.tcx.note_and_explain_region(
718 "captured variable is valid for ",
721 self.tcx.note_and_explain_region(
722 "closure is valid for ",
726 infer::IndexSlice(span) => {
727 span_err!(self.tcx.sess, span, E0475,
728 "index of slice outside its lifetime");
729 self.tcx.note_and_explain_region(
730 "the slice is only valid for ",
734 infer::RelateObjectBound(span) => {
735 span_err!(self.tcx.sess, span, E0476,
736 "lifetime of the source pointer does not outlive \
737 lifetime bound of the object type");
738 self.tcx.note_and_explain_region(
739 "object type is valid for ",
742 self.tcx.note_and_explain_region(
743 "source pointer is only valid for ",
747 infer::RelateParamBound(span, ty) => {
748 span_err!(self.tcx.sess, span, E0477,
749 "the type `{}` does not fulfill the required lifetime",
750 self.ty_to_string(ty));
751 self.tcx.note_and_explain_region(
752 "type must outlive ",
756 infer::RelateRegionParamBound(span) => {
757 span_err!(self.tcx.sess, span, E0478,
758 "lifetime bound not satisfied");
759 self.tcx.note_and_explain_region(
760 "lifetime parameter instantiated with ",
763 self.tcx.note_and_explain_region(
764 "but lifetime parameter must outlive ",
768 infer::RelateDefaultParamBound(span, ty) => {
769 span_err!(self.tcx.sess, span, E0479,
770 "the type `{}` (provided as the value of \
771 a type parameter) is not valid at this point",
772 self.ty_to_string(ty));
773 self.tcx.note_and_explain_region(
774 "type must outlive ",
778 infer::CallRcvr(span) => {
779 span_err!(self.tcx.sess, span, E0480,
780 "lifetime of method receiver does not outlive \
782 self.tcx.note_and_explain_region(
783 "the receiver is only valid for ",
787 infer::CallArg(span) => {
788 span_err!(self.tcx.sess, span, E0481,
789 "lifetime of function argument does not outlive \
791 self.tcx.note_and_explain_region(
792 "the function argument is only valid for ",
796 infer::CallReturn(span) => {
797 span_err!(self.tcx.sess, span, E0482,
798 "lifetime of return value does not outlive \
800 self.tcx.note_and_explain_region(
801 "the return value is only valid for ",
805 infer::Operand(span) => {
806 span_err!(self.tcx.sess, span, E0483,
807 "lifetime of operand does not outlive \
809 self.tcx.note_and_explain_region(
810 "the operand is only valid for ",
814 infer::AddrOf(span) => {
815 span_err!(self.tcx.sess, span, E0484,
816 "reference is not valid at the time of borrow");
817 self.tcx.note_and_explain_region(
818 "the borrow is only valid for ",
822 infer::AutoBorrow(span) => {
823 span_err!(self.tcx.sess, span, E0485,
824 "automatically reference is not valid \
825 at the time of borrow");
826 self.tcx.note_and_explain_region(
827 "the automatic borrow is only valid for ",
831 infer::ExprTypeIsNotInScope(t, span) => {
832 span_err!(self.tcx.sess, span, E0486,
833 "type of expression contains references \
834 that are not valid during the expression: `{}`",
835 self.ty_to_string(t));
836 self.tcx.note_and_explain_region(
837 "type is only valid for ",
841 infer::SafeDestructor(span) => {
842 span_err!(self.tcx.sess, span, E0487,
843 "unsafe use of destructor: destructor might be called \
844 while references are dead");
845 // FIXME (22171): terms "super/subregion" are suboptimal
846 self.tcx.note_and_explain_region(
850 self.tcx.note_and_explain_region(
855 infer::BindingTypeIsNotValidAtDecl(span) => {
856 span_err!(self.tcx.sess, span, E0488,
857 "lifetime of variable does not enclose its declaration");
858 self.tcx.note_and_explain_region(
859 "the variable is only valid for ",
863 infer::ParameterInScope(_, span) => {
864 span_err!(self.tcx.sess, span, E0489,
865 "type/lifetime parameter not in scope here");
866 self.tcx.note_and_explain_region(
867 "the parameter is only valid for ",
871 infer::DataBorrowed(ty, span) => {
872 span_err!(self.tcx.sess, span, E0490,
873 "a value of type `{}` is borrowed for too long",
874 self.ty_to_string(ty));
875 self.tcx.note_and_explain_region("the type is valid for ", sub, "");
876 self.tcx.note_and_explain_region("but the borrow lasts for ", sup, "");
878 infer::ReferenceOutlivesReferent(ty, span) => {
879 span_err!(self.tcx.sess, span, E0491,
880 "in type `{}`, reference has a longer lifetime \
881 than the data it references",
882 self.ty_to_string(ty));
883 self.tcx.note_and_explain_region(
884 "the pointer is valid for ",
887 self.tcx.note_and_explain_region(
888 "but the referenced data is only valid for ",
895 fn report_sub_sup_conflict(&self,
896 var_origin: RegionVariableOrigin,
897 sub_origin: SubregionOrigin<'tcx>,
899 sup_origin: SubregionOrigin<'tcx>,
900 sup_region: Region) {
901 self.report_inference_failure(var_origin);
903 self.tcx.note_and_explain_region(
904 "first, the lifetime cannot outlive ",
908 self.note_region_origin(&sup_origin);
910 self.tcx.note_and_explain_region(
911 "but, the lifetime must be valid for ",
915 self.note_region_origin(&sub_origin);
918 fn report_processed_errors(&self,
919 var_origins: &[RegionVariableOrigin],
920 trace_origins: &[(TypeTrace<'tcx>, TypeError<'tcx>)],
921 same_regions: &[SameRegions]) {
922 for vo in var_origins {
923 self.report_inference_failure(vo.clone());
925 self.give_suggestion(same_regions);
926 for &(ref trace, ref terr) in trace_origins {
927 self.report_and_explain_type_error(trace.clone(), terr);
931 fn give_suggestion(&self, same_regions: &[SameRegions]) {
932 let scope_id = same_regions[0].scope_id;
933 let parent = self.tcx.map.get_parent(scope_id);
934 let parent_node = self.tcx.map.find(parent);
935 let taken = lifetimes_in_scope(self.tcx, scope_id);
936 let life_giver = LifeGiver::with_taken(&taken[..]);
937 let node_inner = match parent_node {
938 Some(ref node) => match *node {
939 ast_map::NodeItem(ref item) => {
941 hir::ItemFn(ref fn_decl, unsafety, constness, _, ref gen, _) => {
942 Some((fn_decl, gen, unsafety, constness,
943 item.name, None, item.span))
948 ast_map::NodeImplItem(item) => {
950 hir::ImplItemKind::Method(ref sig, _) => {
956 Some(&sig.explicit_self.node),
962 ast_map::NodeTraitItem(item) => {
964 hir::MethodTraitItem(ref sig, Some(_)) => {
970 Some(&sig.explicit_self.node),
980 let (fn_decl, generics, unsafety, constness, name, expl_self, span)
981 = node_inner.expect("expect item fn");
982 let rebuilder = Rebuilder::new(self.tcx, fn_decl, expl_self,
983 generics, same_regions, &life_giver);
984 let (fn_decl, expl_self, generics) = rebuilder.rebuild();
985 self.give_expl_lifetime_param(&fn_decl, unsafety, constness, name,
986 expl_self.as_ref(), &generics, span);
990 struct RebuildPathInfo<'a> {
992 // indexes to insert lifetime on path.lifetimes
994 // number of lifetimes we expect to see on the type referred by `path`
995 // (e.g., expected=1 for struct Foo<'a>)
997 anon_nums: &'a HashSet<u32>,
998 region_names: &'a HashSet<ast::Name>
1001 struct Rebuilder<'a, 'tcx: 'a> {
1002 tcx: &'a ty::ctxt<'tcx>,
1003 fn_decl: &'a hir::FnDecl,
1004 expl_self_opt: Option<&'a hir::ExplicitSelf_>,
1005 generics: &'a hir::Generics,
1006 same_regions: &'a [SameRegions],
1007 life_giver: &'a LifeGiver,
1008 cur_anon: Cell<u32>,
1009 inserted_anons: RefCell<HashSet<u32>>,
1017 impl<'a, 'tcx> Rebuilder<'a, 'tcx> {
1018 fn new(tcx: &'a ty::ctxt<'tcx>,
1019 fn_decl: &'a hir::FnDecl,
1020 expl_self_opt: Option<&'a hir::ExplicitSelf_>,
1021 generics: &'a hir::Generics,
1022 same_regions: &'a [SameRegions],
1023 life_giver: &'a LifeGiver)
1024 -> Rebuilder<'a, 'tcx> {
1028 expl_self_opt: expl_self_opt,
1030 same_regions: same_regions,
1031 life_giver: life_giver,
1032 cur_anon: Cell::new(0),
1033 inserted_anons: RefCell::new(HashSet::new()),
1038 -> (hir::FnDecl, Option<hir::ExplicitSelf_>, hir::Generics) {
1039 let mut expl_self_opt = self.expl_self_opt.cloned();
1040 let mut inputs = self.fn_decl.inputs.clone();
1041 let mut output = self.fn_decl.output.clone();
1042 let mut ty_params = self.generics.ty_params.clone();
1043 let where_clause = self.generics.where_clause.clone();
1044 let mut kept_lifetimes = HashSet::new();
1045 for sr in self.same_regions {
1046 self.cur_anon.set(0);
1047 self.offset_cur_anon();
1048 let (anon_nums, region_names) =
1049 self.extract_anon_nums_and_names(sr);
1050 let (lifetime, fresh_or_kept) = self.pick_lifetime(®ion_names);
1051 match fresh_or_kept {
1052 Kept => { kept_lifetimes.insert(lifetime.name); }
1055 expl_self_opt = self.rebuild_expl_self(expl_self_opt, lifetime,
1056 &anon_nums, ®ion_names);
1057 inputs = self.rebuild_args_ty(&inputs[..], lifetime,
1058 &anon_nums, ®ion_names);
1059 output = self.rebuild_output(&output, lifetime, &anon_nums, ®ion_names);
1060 ty_params = self.rebuild_ty_params(ty_params, lifetime,
1063 let fresh_lifetimes = self.life_giver.get_generated_lifetimes();
1064 let all_region_names = self.extract_all_region_names();
1065 let generics = self.rebuild_generics(self.generics,
1071 let new_fn_decl = hir::FnDecl {
1074 variadic: self.fn_decl.variadic
1076 (new_fn_decl, expl_self_opt, generics)
1079 fn pick_lifetime(&self,
1080 region_names: &HashSet<ast::Name>)
1081 -> (hir::Lifetime, FreshOrKept) {
1082 if !region_names.is_empty() {
1083 // It's not necessary to convert the set of region names to a
1084 // vector of string and then sort them. However, it makes the
1085 // choice of lifetime name deterministic and thus easier to test.
1086 let mut names = Vec::new();
1087 for rn in region_names {
1088 let lt_name = rn.to_string();
1089 names.push(lt_name);
1092 let name = token::intern(&names[0]);
1093 return (name_to_dummy_lifetime(name), Kept);
1095 return (self.life_giver.give_lifetime(), Fresh);
1098 fn extract_anon_nums_and_names(&self, same_regions: &SameRegions)
1099 -> (HashSet<u32>, HashSet<ast::Name>) {
1100 let mut anon_nums = HashSet::new();
1101 let mut region_names = HashSet::new();
1102 for br in &same_regions.regions {
1105 anon_nums.insert(i);
1107 ty::BrNamed(_, name) => {
1108 region_names.insert(name);
1113 (anon_nums, region_names)
1116 fn extract_all_region_names(&self) -> HashSet<ast::Name> {
1117 let mut all_region_names = HashSet::new();
1118 for sr in self.same_regions {
1119 for br in &sr.regions {
1121 ty::BrNamed(_, name) => {
1122 all_region_names.insert(name);
1131 fn inc_cur_anon(&self, n: u32) {
1132 let anon = self.cur_anon.get();
1133 self.cur_anon.set(anon+n);
1136 fn offset_cur_anon(&self) {
1137 let mut anon = self.cur_anon.get();
1138 while self.inserted_anons.borrow().contains(&anon) {
1141 self.cur_anon.set(anon);
1144 fn inc_and_offset_cur_anon(&self, n: u32) {
1145 self.inc_cur_anon(n);
1146 self.offset_cur_anon();
1149 fn track_anon(&self, anon: u32) {
1150 self.inserted_anons.borrow_mut().insert(anon);
1153 fn rebuild_ty_params(&self,
1154 ty_params: OwnedSlice<hir::TyParam>,
1155 lifetime: hir::Lifetime,
1156 region_names: &HashSet<ast::Name>)
1157 -> OwnedSlice<hir::TyParam> {
1158 ty_params.map(|ty_param| {
1159 let bounds = self.rebuild_ty_param_bounds(ty_param.bounds.clone(),
1163 name: ty_param.name,
1166 default: ty_param.default.clone(),
1167 span: ty_param.span,
1172 fn rebuild_ty_param_bounds(&self,
1173 ty_param_bounds: OwnedSlice<hir::TyParamBound>,
1174 lifetime: hir::Lifetime,
1175 region_names: &HashSet<ast::Name>)
1176 -> OwnedSlice<hir::TyParamBound> {
1177 ty_param_bounds.map(|tpb| {
1179 &hir::RegionTyParamBound(lt) => {
1180 // FIXME -- it's unclear whether I'm supposed to
1181 // substitute lifetime here. I suspect we need to
1182 // be passing down a map.
1183 hir::RegionTyParamBound(lt)
1185 &hir::TraitTyParamBound(ref poly_tr, modifier) => {
1186 let tr = &poly_tr.trait_ref;
1187 let last_seg = tr.path.segments.last().unwrap();
1188 let mut insert = Vec::new();
1189 let lifetimes = last_seg.parameters.lifetimes();
1190 for (i, lt) in lifetimes.iter().enumerate() {
1191 if region_names.contains(<.name) {
1192 insert.push(i as u32);
1195 let rebuild_info = RebuildPathInfo {
1198 expected: lifetimes.len() as u32,
1199 anon_nums: &HashSet::new(),
1200 region_names: region_names
1202 let new_path = self.rebuild_path(rebuild_info, lifetime);
1203 hir::TraitTyParamBound(hir::PolyTraitRef {
1204 bound_lifetimes: poly_tr.bound_lifetimes.clone(),
1205 trait_ref: hir::TraitRef {
1216 fn rebuild_expl_self(&self,
1217 expl_self_opt: Option<hir::ExplicitSelf_>,
1218 lifetime: hir::Lifetime,
1219 anon_nums: &HashSet<u32>,
1220 region_names: &HashSet<ast::Name>)
1221 -> Option<hir::ExplicitSelf_> {
1222 match expl_self_opt {
1223 Some(ref expl_self) => match *expl_self {
1224 hir::SelfRegion(lt_opt, muta, id) => match lt_opt {
1225 Some(lt) => if region_names.contains(<.name) {
1226 return Some(hir::SelfRegion(Some(lifetime), muta, id));
1229 let anon = self.cur_anon.get();
1230 self.inc_and_offset_cur_anon(1);
1231 if anon_nums.contains(&anon) {
1232 self.track_anon(anon);
1233 return Some(hir::SelfRegion(Some(lifetime), muta, id));
1244 fn rebuild_generics(&self,
1245 generics: &hir::Generics,
1246 add: &Vec<hir::Lifetime>,
1247 keep: &HashSet<ast::Name>,
1248 remove: &HashSet<ast::Name>,
1249 ty_params: OwnedSlice<hir::TyParam>,
1250 where_clause: hir::WhereClause)
1252 let mut lifetimes = Vec::new();
1254 lifetimes.push(hir::LifetimeDef { lifetime: *lt,
1255 bounds: Vec::new() });
1257 for lt in &generics.lifetimes {
1258 if keep.contains(<.lifetime.name) ||
1259 !remove.contains(<.lifetime.name) {
1260 lifetimes.push((*lt).clone());
1264 lifetimes: lifetimes,
1265 ty_params: ty_params,
1266 where_clause: where_clause,
1270 fn rebuild_args_ty(&self,
1271 inputs: &[hir::Arg],
1272 lifetime: hir::Lifetime,
1273 anon_nums: &HashSet<u32>,
1274 region_names: &HashSet<ast::Name>)
1276 let mut new_inputs = Vec::new();
1278 let new_ty = self.rebuild_arg_ty_or_output(&*arg.ty, lifetime,
1279 anon_nums, region_names);
1280 let possibly_new_arg = hir::Arg {
1282 pat: arg.pat.clone(),
1285 new_inputs.push(possibly_new_arg);
1290 fn rebuild_output(&self, ty: &hir::FunctionRetTy,
1291 lifetime: hir::Lifetime,
1292 anon_nums: &HashSet<u32>,
1293 region_names: &HashSet<ast::Name>) -> hir::FunctionRetTy {
1295 hir::Return(ref ret_ty) => hir::Return(
1296 self.rebuild_arg_ty_or_output(&**ret_ty, lifetime, anon_nums, region_names)
1298 hir::DefaultReturn(span) => hir::DefaultReturn(span),
1299 hir::NoReturn(span) => hir::NoReturn(span)
1303 fn rebuild_arg_ty_or_output(&self,
1305 lifetime: hir::Lifetime,
1306 anon_nums: &HashSet<u32>,
1307 region_names: &HashSet<ast::Name>)
1309 let mut new_ty = P(ty.clone());
1310 let mut ty_queue = vec!(ty);
1311 while !ty_queue.is_empty() {
1312 let cur_ty = ty_queue.remove(0);
1314 hir::TyRptr(lt_opt, ref mut_ty) => {
1315 let rebuild = match lt_opt {
1316 Some(lt) => region_names.contains(<.name),
1318 let anon = self.cur_anon.get();
1319 let rebuild = anon_nums.contains(&anon);
1321 self.track_anon(anon);
1323 self.inc_and_offset_cur_anon(1);
1330 node: hir::TyRptr(Some(lifetime), mut_ty.clone()),
1333 new_ty = self.rebuild_ty(new_ty, P(to));
1335 ty_queue.push(&*mut_ty.ty);
1337 hir::TyPath(ref maybe_qself, ref path) => {
1338 let a_def = match self.tcx.def_map.borrow().get(&cur_ty.id) {
1344 pprust::path_to_string(path)))
1346 Some(d) => d.full_def()
1349 def::DefTy(did, _) | def::DefStruct(did) => {
1350 let generics = self.tcx.lookup_item_type(did).generics;
1353 generics.regions.len(subst::TypeSpace) as u32;
1355 path.segments.last().unwrap().parameters.lifetimes();
1356 let mut insert = Vec::new();
1357 if lifetimes.is_empty() {
1358 let anon = self.cur_anon.get();
1359 for (i, a) in (anon..anon+expected).enumerate() {
1360 if anon_nums.contains(&a) {
1361 insert.push(i as u32);
1365 self.inc_and_offset_cur_anon(expected);
1367 for (i, lt) in lifetimes.iter().enumerate() {
1368 if region_names.contains(<.name) {
1369 insert.push(i as u32);
1373 let rebuild_info = RebuildPathInfo {
1377 anon_nums: anon_nums,
1378 region_names: region_names
1380 let new_path = self.rebuild_path(rebuild_info, lifetime);
1381 let qself = maybe_qself.as_ref().map(|qself| {
1383 ty: self.rebuild_arg_ty_or_output(&qself.ty, lifetime,
1384 anon_nums, region_names),
1385 position: qself.position
1390 node: hir::TyPath(qself, new_path),
1393 new_ty = self.rebuild_ty(new_ty, P(to));
1400 hir::TyPtr(ref mut_ty) => {
1401 ty_queue.push(&*mut_ty.ty);
1403 hir::TyVec(ref ty) |
1404 hir::TyFixedLengthVec(ref ty, _) => {
1405 ty_queue.push(&**ty);
1407 hir::TyTup(ref tys) => ty_queue.extend(tys.iter().map(|ty| &**ty)),
1414 fn rebuild_ty(&self,
1419 fn build_to(from: P<hir::Ty>,
1420 to: &mut Option<P<hir::Ty>>)
1422 if Some(from.id) == to.as_ref().map(|ty| ty.id) {
1423 return to.take().expect("`to` type found more than once during rebuild");
1425 from.map(|hir::Ty {id, node, span}| {
1426 let new_node = match node {
1427 hir::TyRptr(lifetime, mut_ty) => {
1428 hir::TyRptr(lifetime, hir::MutTy {
1429 mutbl: mut_ty.mutbl,
1430 ty: build_to(mut_ty.ty, to),
1433 hir::TyPtr(mut_ty) => {
1434 hir::TyPtr(hir::MutTy {
1435 mutbl: mut_ty.mutbl,
1436 ty: build_to(mut_ty.ty, to),
1439 hir::TyVec(ty) => hir::TyVec(build_to(ty, to)),
1440 hir::TyFixedLengthVec(ty, e) => {
1441 hir::TyFixedLengthVec(build_to(ty, to), e)
1443 hir::TyTup(tys) => {
1444 hir::TyTup(tys.into_iter().map(|ty| build_to(ty, to)).collect())
1448 hir::Ty { id: id, node: new_node, span: span }
1452 build_to(from, &mut Some(to))
1455 fn rebuild_path(&self,
1456 rebuild_info: RebuildPathInfo,
1457 lifetime: hir::Lifetime)
1460 let RebuildPathInfo {
1468 let last_seg = path.segments.last().unwrap();
1469 let new_parameters = match last_seg.parameters {
1470 hir::ParenthesizedParameters(..) => {
1471 last_seg.parameters.clone()
1474 hir::AngleBracketedParameters(ref data) => {
1475 let mut new_lts = Vec::new();
1476 if data.lifetimes.is_empty() {
1477 // traverse once to see if there's a need to insert lifetime
1478 let need_insert = (0..expected).any(|i| {
1479 indexes.contains(&i)
1482 for i in 0..expected {
1483 if indexes.contains(&i) {
1484 new_lts.push(lifetime);
1486 new_lts.push(self.life_giver.give_lifetime());
1491 for (i, lt) in data.lifetimes.iter().enumerate() {
1492 if indexes.contains(&(i as u32)) {
1493 new_lts.push(lifetime);
1499 let new_types = data.types.map(|t| {
1500 self.rebuild_arg_ty_or_output(&**t, lifetime, anon_nums, region_names)
1502 let new_bindings = data.bindings.map(|b| {
1506 ty: self.rebuild_arg_ty_or_output(&*b.ty,
1513 hir::AngleBracketedParameters(hir::AngleBracketedParameterData {
1516 bindings: new_bindings,
1520 let new_seg = hir::PathSegment {
1521 identifier: last_seg.identifier,
1522 parameters: new_parameters
1524 let mut new_segs = Vec::new();
1525 new_segs.extend_from_slice(path.segments.split_last().unwrap().1);
1526 new_segs.push(new_seg);
1529 global: path.global,
1535 impl<'a, 'tcx> ErrorReportingHelpers<'tcx> for InferCtxt<'a, 'tcx> {
1536 fn give_expl_lifetime_param(&self,
1538 unsafety: hir::Unsafety,
1539 constness: hir::Constness,
1541 opt_explicit_self: Option<&hir::ExplicitSelf_>,
1542 generics: &hir::Generics,
1544 let suggested_fn = pprust::fun_to_string(decl, unsafety, constness, name,
1545 opt_explicit_self, generics);
1546 let msg = format!("consider using an explicit lifetime \
1547 parameter as shown: {}", suggested_fn);
1548 self.tcx.sess.span_help(span, &msg[..]);
1551 fn report_inference_failure(&self,
1552 var_origin: RegionVariableOrigin) {
1553 let br_string = |br: ty::BoundRegion| {
1554 let mut s = br.to_string();
1560 let var_description = match var_origin {
1561 infer::MiscVariable(_) => "".to_string(),
1562 infer::PatternRegion(_) => " for pattern".to_string(),
1563 infer::AddrOfRegion(_) => " for borrow expression".to_string(),
1564 infer::Autoref(_) => " for autoref".to_string(),
1565 infer::Coercion(_) => " for automatic coercion".to_string(),
1566 infer::LateBoundRegion(_, br, infer::FnCall) => {
1567 format!(" for lifetime parameter {}in function call",
1570 infer::LateBoundRegion(_, br, infer::HigherRankedType) => {
1571 format!(" for lifetime parameter {}in generic type", br_string(br))
1573 infer::LateBoundRegion(_, br, infer::AssocTypeProjection(type_name)) => {
1574 format!(" for lifetime parameter {}in trait containing associated type `{}`",
1575 br_string(br), type_name)
1577 infer::EarlyBoundRegion(_, name) => {
1578 format!(" for lifetime parameter `{}`",
1581 infer::BoundRegionInCoherence(name) => {
1582 format!(" for lifetime parameter `{}` in coherence check",
1585 infer::UpvarRegion(ref upvar_id, _) => {
1586 format!(" for capture of `{}` by closure",
1587 self.tcx.local_var_name_str(upvar_id.var_id).to_string())
1591 span_err!(self.tcx.sess, var_origin.span(), E0495,
1592 "cannot infer an appropriate lifetime{} \
1593 due to conflicting requirements",
1597 fn note_region_origin(&self, origin: &SubregionOrigin<'tcx>) {
1599 infer::RFC1214Subregion(ref suborigin) => {
1600 self.note_region_origin(suborigin);
1602 infer::Subtype(ref trace) => {
1603 let desc = match trace.origin {
1604 TypeOrigin::Misc(_) => {
1605 "types are compatible"
1607 TypeOrigin::MethodCompatCheck(_) => {
1608 "method type is compatible with trait"
1610 TypeOrigin::ExprAssignable(_) => {
1611 "expression is assignable"
1613 TypeOrigin::RelateTraitRefs(_) => {
1614 "traits are compatible"
1616 TypeOrigin::RelateSelfType(_) => {
1617 "self type matches impl self type"
1619 TypeOrigin::RelateOutputImplTypes(_) => {
1620 "trait type parameters matches those \
1621 specified on the impl"
1623 TypeOrigin::MatchExpressionArm(_, _, _) => {
1624 "match arms have compatible types"
1626 TypeOrigin::IfExpression(_) => {
1627 "if and else have compatible types"
1629 TypeOrigin::IfExpressionWithNoElse(_) => {
1630 "if may be missing an else clause"
1632 TypeOrigin::RangeExpression(_) => {
1633 "start and end of range have compatible types"
1635 TypeOrigin::EquatePredicate(_) => {
1636 "equality where clause is satisfied"
1640 match self.values_str(&trace.values) {
1641 Some(values_str) => {
1642 self.tcx.sess.span_note(
1643 trace.origin.span(),
1644 &format!("...so that {} ({})",
1648 // Really should avoid printing this error at
1649 // all, since it is derived, but that would
1650 // require more refactoring than I feel like
1651 // doing right now. - nmatsakis
1652 self.tcx.sess.span_note(
1653 trace.origin.span(),
1654 &format!("...so that {}", desc));
1658 infer::Reborrow(span) => {
1659 self.tcx.sess.span_note(
1661 "...so that reference does not outlive \
1664 infer::ReborrowUpvar(span, ref upvar_id) => {
1665 self.tcx.sess.span_note(
1668 "...so that closure can access `{}`",
1669 self.tcx.local_var_name_str(upvar_id.var_id)
1672 infer::InfStackClosure(span) => {
1673 self.tcx.sess.span_note(
1675 "...so that closure does not outlive its stack frame");
1677 infer::InvokeClosure(span) => {
1678 self.tcx.sess.span_note(
1680 "...so that closure is not invoked outside its lifetime");
1682 infer::DerefPointer(span) => {
1683 self.tcx.sess.span_note(
1685 "...so that pointer is not dereferenced \
1686 outside its lifetime");
1688 infer::FreeVariable(span, id) => {
1689 self.tcx.sess.span_note(
1691 &format!("...so that captured variable `{}` \
1692 does not outlive the enclosing closure",
1693 self.tcx.local_var_name_str(id)));
1695 infer::IndexSlice(span) => {
1696 self.tcx.sess.span_note(
1698 "...so that slice is not indexed outside the lifetime");
1700 infer::RelateObjectBound(span) => {
1701 self.tcx.sess.span_note(
1703 "...so that it can be closed over into an object");
1705 infer::CallRcvr(span) => {
1706 self.tcx.sess.span_note(
1708 "...so that method receiver is valid for the method call");
1710 infer::CallArg(span) => {
1711 self.tcx.sess.span_note(
1713 "...so that argument is valid for the call");
1715 infer::CallReturn(span) => {
1716 self.tcx.sess.span_note(
1718 "...so that return value is valid for the call");
1720 infer::Operand(span) => {
1721 self.tcx.sess.span_note(
1723 "...so that operand is valid for operation");
1725 infer::AddrOf(span) => {
1726 self.tcx.sess.span_note(
1728 "...so that reference is valid \
1729 at the time of borrow");
1731 infer::AutoBorrow(span) => {
1732 self.tcx.sess.span_note(
1734 "...so that auto-reference is valid \
1735 at the time of borrow");
1737 infer::ExprTypeIsNotInScope(t, span) => {
1738 self.tcx.sess.span_note(
1740 &format!("...so type `{}` of expression is valid during the \
1742 self.ty_to_string(t)));
1744 infer::BindingTypeIsNotValidAtDecl(span) => {
1745 self.tcx.sess.span_note(
1747 "...so that variable is valid at time of its declaration");
1749 infer::ParameterInScope(_, span) => {
1750 self.tcx.sess.span_note(
1752 "...so that a type/lifetime parameter is in scope here");
1754 infer::DataBorrowed(ty, span) => {
1755 self.tcx.sess.span_note(
1757 &format!("...so that the type `{}` is not borrowed for too long",
1758 self.ty_to_string(ty)));
1760 infer::ReferenceOutlivesReferent(ty, span) => {
1761 self.tcx.sess.span_note(
1763 &format!("...so that the reference type `{}` \
1764 does not outlive the data it points at",
1765 self.ty_to_string(ty)));
1767 infer::RelateParamBound(span, t) => {
1768 self.tcx.sess.span_note(
1770 &format!("...so that the type `{}` \
1771 will meet its required lifetime bounds",
1772 self.ty_to_string(t)));
1774 infer::RelateDefaultParamBound(span, t) => {
1775 self.tcx.sess.span_note(
1777 &format!("...so that type parameter \
1778 instantiated with `{}`, \
1779 will meet its declared lifetime bounds",
1780 self.ty_to_string(t)));
1782 infer::RelateRegionParamBound(span) => {
1783 self.tcx.sess.span_note(
1785 "...so that the declared lifetime parameter bounds \
1788 infer::SafeDestructor(span) => {
1789 self.tcx.sess.span_note(
1791 "...so that references are valid when the destructor \
1798 pub trait Resolvable<'tcx> {
1799 fn resolve<'a>(&self, infcx: &InferCtxt<'a, 'tcx>) -> Self;
1802 impl<'tcx> Resolvable<'tcx> for Ty<'tcx> {
1803 fn resolve<'a>(&self, infcx: &InferCtxt<'a, 'tcx>) -> Ty<'tcx> {
1804 infcx.resolve_type_vars_if_possible(self)
1808 impl<'tcx> Resolvable<'tcx> for ty::TraitRef<'tcx> {
1809 fn resolve<'a>(&self, infcx: &InferCtxt<'a, 'tcx>)
1810 -> ty::TraitRef<'tcx> {
1811 infcx.resolve_type_vars_if_possible(self)
1815 impl<'tcx> Resolvable<'tcx> for ty::PolyTraitRef<'tcx> {
1816 fn resolve<'a>(&self,
1817 infcx: &InferCtxt<'a, 'tcx>)
1818 -> ty::PolyTraitRef<'tcx>
1820 infcx.resolve_type_vars_if_possible(self)
1824 fn lifetimes_in_scope(tcx: &ty::ctxt,
1825 scope_id: ast::NodeId)
1826 -> Vec<hir::LifetimeDef> {
1827 let mut taken = Vec::new();
1828 let parent = tcx.map.get_parent(scope_id);
1829 let method_id_opt = match tcx.map.find(parent) {
1830 Some(node) => match node {
1831 ast_map::NodeItem(item) => match item.node {
1832 hir::ItemFn(_, _, _, _, ref gen, _) => {
1833 taken.extend_from_slice(&gen.lifetimes);
1838 ast_map::NodeImplItem(ii) => {
1840 hir::ImplItemKind::Method(ref sig, _) => {
1841 taken.extend_from_slice(&sig.generics.lifetimes);
1851 if method_id_opt.is_some() {
1852 let method_id = method_id_opt.unwrap();
1853 let parent = tcx.map.get_parent(method_id);
1854 match tcx.map.find(parent) {
1855 Some(node) => match node {
1856 ast_map::NodeItem(item) => match item.node {
1857 hir::ItemImpl(_, _, ref gen, _, _, _) => {
1858 taken.extend_from_slice(&gen.lifetimes);
1870 // LifeGiver is responsible for generating fresh lifetime names
1872 taken: HashSet<String>,
1873 counter: Cell<usize>,
1874 generated: RefCell<Vec<hir::Lifetime>>,
1878 fn with_taken(taken: &[hir::LifetimeDef]) -> LifeGiver {
1879 let mut taken_ = HashSet::new();
1881 let lt_name = lt.lifetime.name.to_string();
1882 taken_.insert(lt_name);
1886 counter: Cell::new(0),
1887 generated: RefCell::new(Vec::new()),
1891 fn inc_counter(&self) {
1892 let c = self.counter.get();
1893 self.counter.set(c+1);
1896 fn give_lifetime(&self) -> hir::Lifetime {
1899 let mut s = String::from("'");
1900 s.push_str(&num_to_string(self.counter.get()));
1901 if !self.taken.contains(&s) {
1902 lifetime = name_to_dummy_lifetime(token::intern(&s[..]));
1903 self.generated.borrow_mut().push(lifetime);
1911 // 0 .. 25 generates a .. z, 26 .. 51 generates aa .. zz, and so on
1912 fn num_to_string(counter: usize) -> String {
1913 let mut s = String::new();
1914 let (n, r) = (counter/26 + 1, counter % 26);
1915 let letter: char = from_u32((r+97) as u32).unwrap();
1923 fn get_generated_lifetimes(&self) -> Vec<hir::Lifetime> {
1924 self.generated.borrow().clone()
1928 fn name_to_dummy_lifetime(name: ast::Name) -> hir::Lifetime {
1929 hir::Lifetime { id: ast::DUMMY_NODE_ID,
1930 span: codemap::DUMMY_SP,