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::codemap::{self, Pos, Span};
94 use syntax::parse::token;
97 impl<'tcx> ty::ctxt<'tcx> {
98 pub fn note_and_explain_region(&self,
102 fn item_scope_tag(item: &hir::Item) -> &'static str {
104 hir::ItemImpl(..) => "impl",
105 hir::ItemStruct(..) => "struct",
106 hir::ItemEnum(..) => "enum",
107 hir::ItemTrait(..) => "trait",
108 hir::ItemFn(..) => "function body",
113 fn explain_span(tcx: &ty::ctxt, heading: &str, span: Span)
114 -> (String, Option<Span>) {
115 let lo = tcx.sess.codemap().lookup_char_pos_adj(span.lo);
116 (format!("the {} at {}:{}", heading, lo.line, lo.col.to_usize()),
120 let (description, span) = match region {
121 ty::ReScope(scope) => {
123 let unknown_scope = || {
124 format!("{}unknown scope: {:?}{}. Please report a bug.",
125 prefix, scope, suffix)
127 let span = match scope.span(&self.region_maps, &self.map) {
129 None => return self.sess.note(&unknown_scope())
131 let tag = match self.map.find(scope.node_id(&self.region_maps)) {
132 Some(ast_map::NodeBlock(_)) => "block",
133 Some(ast_map::NodeExpr(expr)) => match expr.node {
134 hir::ExprCall(..) => "call",
135 hir::ExprMethodCall(..) => "method call",
136 hir::ExprMatch(_, _, hir::MatchSource::IfLetDesugar { .. }) => "if let",
137 hir::ExprMatch(_, _, hir::MatchSource::WhileLetDesugar) => "while let",
138 hir::ExprMatch(_, _, hir::MatchSource::ForLoopDesugar) => "for",
139 hir::ExprMatch(..) => "match",
142 Some(ast_map::NodeStmt(_)) => "statement",
143 Some(ast_map::NodeItem(it)) => item_scope_tag(&*it),
145 return self.sess.span_note(span, &unknown_scope());
148 let scope_decorated_tag = match self.region_maps.code_extent_data(scope) {
149 region::CodeExtentData::Misc(_) => tag,
150 region::CodeExtentData::CallSiteScope { .. } => {
151 "scope of call-site for function"
153 region::CodeExtentData::ParameterScope { .. } => {
154 "scope of parameters for function"
156 region::CodeExtentData::DestructionScope(_) => {
157 new_string = format!("destruction scope surrounding {}", tag);
160 region::CodeExtentData::Remainder(r) => {
161 new_string = format!("block suffix following statement {}",
162 r.first_statement_index);
166 explain_span(self, scope_decorated_tag, span)
169 ty::ReFree(ref fr) => {
170 let prefix = match fr.bound_region {
172 format!("the anonymous lifetime #{} defined on", idx + 1)
174 ty::BrFresh(_) => "an anonymous lifetime defined on".to_owned(),
176 format!("the lifetime {} as defined on",
181 match self.map.find(fr.scope.node_id(&self.region_maps)) {
182 Some(ast_map::NodeBlock(ref blk)) => {
183 let (msg, opt_span) = explain_span(self, "block", blk.span);
184 (format!("{} {}", prefix, msg), opt_span)
186 Some(ast_map::NodeItem(it)) => {
187 let tag = item_scope_tag(&*it);
188 let (msg, opt_span) = explain_span(self, tag, it.span);
189 (format!("{} {}", prefix, msg), opt_span)
192 // this really should not happen, but it does:
194 (format!("{} unknown free region bounded by scope {:?}",
195 prefix, fr.scope), None)
200 ty::ReStatic => ("the static lifetime".to_owned(), None),
202 ty::ReEmpty => ("the empty lifetime".to_owned(), None),
204 ty::ReEarlyBound(ref data) => (data.name.to_string(), None),
206 // FIXME(#13998) ReSkolemized should probably print like
207 // ReFree rather than dumping Debug output on the user.
209 // We shouldn't really be having unification failures with ReVar
210 // and ReLateBound though.
211 ty::ReSkolemized(..) | ty::ReVar(_) | ty::ReLateBound(..) => {
212 (format!("lifetime {:?}", region), None)
215 let message = format!("{}{}{}", prefix, description, suffix);
216 if let Some(span) = span {
217 self.sess.span_note(span, &message);
219 self.sess.note(&message);
224 pub trait ErrorReporting<'tcx> {
225 fn report_region_errors(&self,
226 errors: &Vec<RegionResolutionError<'tcx>>);
228 fn process_errors(&self, errors: &Vec<RegionResolutionError<'tcx>>)
229 -> Vec<RegionResolutionError<'tcx>>;
231 fn report_type_error(&self, trace: TypeTrace<'tcx>, terr: &TypeError<'tcx>);
233 fn check_and_note_conflicting_crates(&self, terr: &TypeError<'tcx>, sp: Span);
235 fn report_and_explain_type_error(&self,
236 trace: TypeTrace<'tcx>,
237 terr: &TypeError<'tcx>);
239 fn values_str(&self, values: &ValuePairs<'tcx>) -> Option<String>;
241 fn expected_found_str<T: fmt::Display + Resolvable<'tcx> + HasTypeFlags>(
243 exp_found: &ty::error::ExpectedFound<T>)
246 fn report_concrete_failure(&self,
247 origin: SubregionOrigin<'tcx>,
251 fn report_generic_bound_failure(&self,
252 origin: SubregionOrigin<'tcx>,
253 kind: GenericKind<'tcx>,
256 fn report_sub_sup_conflict(&self,
257 var_origin: RegionVariableOrigin,
258 sub_origin: SubregionOrigin<'tcx>,
260 sup_origin: SubregionOrigin<'tcx>,
263 fn report_processed_errors(&self,
264 var_origin: &[RegionVariableOrigin],
265 trace_origin: &[(TypeTrace<'tcx>, TypeError<'tcx>)],
266 same_regions: &[SameRegions]);
268 fn give_suggestion(&self, same_regions: &[SameRegions]);
271 trait ErrorReportingHelpers<'tcx> {
272 fn report_inference_failure(&self,
273 var_origin: RegionVariableOrigin);
275 fn note_region_origin(&self,
276 origin: &SubregionOrigin<'tcx>);
278 fn give_expl_lifetime_param(&self,
280 unsafety: hir::Unsafety,
281 constness: hir::Constness,
283 opt_explicit_self: Option<&hir::ExplicitSelf_>,
284 generics: &hir::Generics,
288 impl<'a, 'tcx> ErrorReporting<'tcx> for InferCtxt<'a, 'tcx> {
289 fn report_region_errors(&self,
290 errors: &Vec<RegionResolutionError<'tcx>>) {
291 let p_errors = self.process_errors(errors);
292 let errors = if p_errors.is_empty() { errors } else { &p_errors };
293 for error in errors {
294 match error.clone() {
295 ConcreteFailure(origin, sub, sup) => {
296 self.report_concrete_failure(origin, sub, sup);
299 GenericBoundFailure(kind, param_ty, sub) => {
300 self.report_generic_bound_failure(kind, param_ty, sub);
303 SubSupConflict(var_origin,
305 sup_origin, sup_r) => {
306 self.report_sub_sup_conflict(var_origin,
311 ProcessedErrors(ref var_origins,
313 ref same_regions) => {
314 if !same_regions.is_empty() {
315 self.report_processed_errors(&var_origins[..],
324 // This method goes through all the errors and try to group certain types
325 // of error together, for the purpose of suggesting explicit lifetime
326 // parameters to the user. This is done so that we can have a more
327 // complete view of what lifetimes should be the same.
328 // If the return value is an empty vector, it means that processing
329 // failed (so the return value of this method should not be used)
330 fn process_errors(&self, errors: &Vec<RegionResolutionError<'tcx>>)
331 -> Vec<RegionResolutionError<'tcx>> {
332 debug!("process_errors()");
333 let mut var_origins = Vec::new();
334 let mut trace_origins = Vec::new();
335 let mut same_regions = Vec::new();
336 let mut processed_errors = Vec::new();
337 for error in errors {
338 match error.clone() {
339 ConcreteFailure(origin, sub, sup) => {
340 debug!("processing ConcreteFailure");
341 let trace = match origin {
342 infer::Subtype(trace) => Some(trace),
345 match free_regions_from_same_fn(self.tcx, sub, sup) {
346 Some(ref same_frs) if trace.is_some() => {
347 let trace = trace.unwrap();
348 let terr = TypeError::RegionsDoesNotOutlive(sup,
350 trace_origins.push((trace, terr));
351 append_to_same_regions(&mut same_regions, same_frs);
353 _ => processed_errors.push((*error).clone()),
356 SubSupConflict(var_origin, _, sub_r, _, sup_r) => {
357 debug!("processing SubSupConflict sub: {:?} sup: {:?}", sub_r, sup_r);
358 match free_regions_from_same_fn(self.tcx, sub_r, sup_r) {
359 Some(ref same_frs) => {
360 var_origins.push(var_origin);
361 append_to_same_regions(&mut same_regions, same_frs);
363 None => processed_errors.push((*error).clone()),
366 _ => () // This shouldn't happen
369 if !same_regions.is_empty() {
370 let common_scope_id = same_regions[0].scope_id;
371 for sr in &same_regions {
372 // Since ProcessedErrors is used to reconstruct the function
373 // declaration, we want to make sure that they are, in fact,
374 // from the same scope
375 if sr.scope_id != common_scope_id {
376 debug!("returning empty result from process_errors because
377 {} != {}", sr.scope_id, common_scope_id);
381 let pe = ProcessedErrors(var_origins, trace_origins, same_regions);
382 debug!("errors processed: {:?}", pe);
383 processed_errors.push(pe);
385 return processed_errors;
388 struct FreeRegionsFromSameFn {
389 sub_fr: ty::FreeRegion,
390 sup_fr: ty::FreeRegion,
391 scope_id: ast::NodeId
394 impl FreeRegionsFromSameFn {
395 fn new(sub_fr: ty::FreeRegion,
396 sup_fr: ty::FreeRegion,
397 scope_id: ast::NodeId)
398 -> FreeRegionsFromSameFn {
399 FreeRegionsFromSameFn {
407 fn free_regions_from_same_fn(tcx: &ty::ctxt,
410 -> Option<FreeRegionsFromSameFn> {
411 debug!("free_regions_from_same_fn(sub={:?}, sup={:?})", sub, sup);
412 let (scope_id, fr1, fr2) = match (sub, sup) {
413 (ReFree(fr1), ReFree(fr2)) => {
414 if fr1.scope != fr2.scope {
417 assert!(fr1.scope == fr2.scope);
418 (fr1.scope.node_id(&tcx.region_maps), fr1, fr2)
422 let parent = tcx.map.get_parent(scope_id);
423 let parent_node = tcx.map.find(parent);
425 Some(node) => match node {
426 ast_map::NodeItem(item) => match item.node {
428 Some(FreeRegionsFromSameFn::new(fr1, fr2, scope_id))
432 ast_map::NodeImplItem(..) |
433 ast_map::NodeTraitItem(..) => {
434 Some(FreeRegionsFromSameFn::new(fr1, fr2, scope_id))
439 debug!("no parent node of scope_id {}", scope_id);
445 fn append_to_same_regions(same_regions: &mut Vec<SameRegions>,
446 same_frs: &FreeRegionsFromSameFn) {
447 let scope_id = same_frs.scope_id;
448 let (sub_fr, sup_fr) = (same_frs.sub_fr, same_frs.sup_fr);
449 for sr in &mut *same_regions {
450 if sr.contains(&sup_fr.bound_region)
451 && scope_id == sr.scope_id {
452 sr.push(sub_fr.bound_region);
456 same_regions.push(SameRegions {
458 regions: vec!(sub_fr.bound_region, sup_fr.bound_region)
463 fn report_type_error(&self, trace: TypeTrace<'tcx>, terr: &TypeError<'tcx>) {
464 let expected_found_str = match self.values_str(&trace.values) {
467 return; /* derived error */
471 span_err!(self.tcx.sess, trace.origin.span(), E0308,
477 self.check_and_note_conflicting_crates(terr, trace.origin.span());
480 TypeOrigin::MatchExpressionArm(_, arm_span, source) => match source {
481 hir::MatchSource::IfLetDesugar{..} =>
482 self.tcx.sess.span_note(arm_span, "`if let` arm with an incompatible type"),
483 _ => self.tcx.sess.span_note(arm_span, "match arm with an incompatible type"),
489 /// Adds a note if the types come from similarly named crates
490 fn check_and_note_conflicting_crates(&self, terr: &TypeError<'tcx>, sp: Span) {
491 let report_path_match = |did1: DefId, did2: DefId| {
492 // Only external crates, if either is from a local
493 // module we could have false positives
494 if !(did1.is_local() || did2.is_local()) && did1.krate != did2.krate {
495 let exp_path = self.tcx.with_path(did1,
496 |p| p.map(|x| x.to_string())
497 .collect::<Vec<_>>());
498 let found_path = self.tcx.with_path(did2,
499 |p| p.map(|x| x.to_string())
500 .collect::<Vec<_>>());
501 // We compare strings because PathMod and PathName can be different
502 // for imported and non-imported crates
503 if exp_path == found_path {
504 let crate_name = self.tcx.sess.cstore.crate_name(did1.krate);
505 self.tcx.sess.span_note(sp, &format!("Perhaps two different versions \
506 of crate `{}` are being used?",
512 TypeError::Sorts(ref exp_found) => {
513 // if they are both "path types", there's a chance of ambiguity
514 // due to different versions of the same crate
515 match (&exp_found.expected.sty, &exp_found.found.sty) {
516 (&ty::TyEnum(ref exp_adt, _), &ty::TyEnum(ref found_adt, _)) |
517 (&ty::TyStruct(ref exp_adt, _), &ty::TyStruct(ref found_adt, _)) |
518 (&ty::TyEnum(ref exp_adt, _), &ty::TyStruct(ref found_adt, _)) |
519 (&ty::TyStruct(ref exp_adt, _), &ty::TyEnum(ref found_adt, _)) => {
520 report_path_match(exp_adt.did, found_adt.did);
525 TypeError::Traits(ref exp_found) => {
526 report_path_match(exp_found.expected, exp_found.found);
528 _ => () // FIXME(#22750) handle traits and stuff
532 fn report_and_explain_type_error(&self,
533 trace: TypeTrace<'tcx>,
534 terr: &TypeError<'tcx>) {
535 let span = trace.origin.span();
536 self.report_type_error(trace, terr);
537 self.tcx.note_and_explain_type_err(terr, span);
540 /// Returns a string of the form "expected `{}`, found `{}`", or None if this is a derived
542 fn values_str(&self, values: &ValuePairs<'tcx>) -> Option<String> {
544 infer::Types(ref exp_found) => self.expected_found_str(exp_found),
545 infer::TraitRefs(ref exp_found) => self.expected_found_str(exp_found),
546 infer::PolyTraitRefs(ref exp_found) => self.expected_found_str(exp_found)
550 fn expected_found_str<T: fmt::Display + Resolvable<'tcx> + HasTypeFlags>(
552 exp_found: &ty::error::ExpectedFound<T>)
555 let expected = exp_found.expected.resolve(self);
556 if expected.references_error() {
560 let found = exp_found.found.resolve(self);
561 if found.references_error() {
565 Some(format!("expected `{}`, found `{}`",
570 fn report_generic_bound_failure(&self,
571 origin: SubregionOrigin<'tcx>,
572 bound_kind: GenericKind<'tcx>,
575 // FIXME: it would be better to report the first error message
576 // with the span of the parameter itself, rather than the span
577 // where the error was detected. But that span is not readily
580 let labeled_user_string = match bound_kind {
581 GenericKind::Param(ref p) =>
582 format!("the parameter type `{}`", p),
583 GenericKind::Projection(ref p) =>
584 format!("the associated type `{}`", p),
588 ty::ReFree(ty::FreeRegion {bound_region: ty::BrNamed(..), ..}) => {
589 // Does the required lifetime have a nice name we can print?
591 self.tcx.sess, origin.span(), E0309,
592 "{} may not live long enough", labeled_user_string);
593 self.tcx.sess.fileline_help(
596 "consider adding an explicit lifetime bound `{}: {}`...",
602 // Does the required lifetime have a nice name we can print?
604 self.tcx.sess, origin.span(), E0310,
605 "{} may not live long enough", labeled_user_string);
606 self.tcx.sess.fileline_help(
609 "consider adding an explicit lifetime bound `{}: 'static`...",
614 // If not, be less specific.
616 self.tcx.sess, origin.span(), E0311,
617 "{} may not live long enough",
618 labeled_user_string);
619 self.tcx.sess.fileline_help(
622 "consider adding an explicit lifetime bound for `{}`",
624 self.tcx.note_and_explain_region(
625 &format!("{} must be valid for ", labeled_user_string),
631 self.note_region_origin(&origin);
634 fn report_concrete_failure(&self,
635 origin: SubregionOrigin<'tcx>,
639 infer::Subtype(trace) => {
640 let terr = TypeError::RegionsDoesNotOutlive(sup, sub);
641 self.report_and_explain_type_error(trace, &terr);
643 infer::Reborrow(span) => {
644 span_err!(self.tcx.sess, span, E0312,
645 "lifetime of reference outlines \
646 lifetime of borrowed content...");
647 self.tcx.note_and_explain_region(
648 "...the reference is valid for ",
651 self.tcx.note_and_explain_region(
652 "...but the borrowed content is only valid for ",
656 infer::ReborrowUpvar(span, ref upvar_id) => {
657 span_err!(self.tcx.sess, span, E0313,
658 "lifetime of borrowed pointer outlives \
659 lifetime of captured variable `{}`...",
660 self.tcx.local_var_name_str(upvar_id.var_id));
661 self.tcx.note_and_explain_region(
662 "...the borrowed pointer is valid for ",
665 self.tcx.note_and_explain_region(
666 &format!("...but `{}` is only valid for ",
667 self.tcx.local_var_name_str(upvar_id.var_id)),
671 infer::InfStackClosure(span) => {
672 span_err!(self.tcx.sess, span, E0314,
673 "closure outlives stack frame");
674 self.tcx.note_and_explain_region(
675 "...the closure must be valid for ",
678 self.tcx.note_and_explain_region(
679 "...but the closure's stack frame is only valid for ",
683 infer::InvokeClosure(span) => {
684 span_err!(self.tcx.sess, span, E0315,
685 "cannot invoke closure outside of its lifetime");
686 self.tcx.note_and_explain_region(
687 "the closure is only valid for ",
691 infer::DerefPointer(span) => {
692 span_err!(self.tcx.sess, span, E0473,
693 "dereference of reference outside its lifetime");
694 self.tcx.note_and_explain_region(
695 "the reference is only valid for ",
699 infer::FreeVariable(span, id) => {
700 span_err!(self.tcx.sess, span, E0474,
701 "captured variable `{}` does not outlive the enclosing closure",
702 self.tcx.local_var_name_str(id));
703 self.tcx.note_and_explain_region(
704 "captured variable is valid for ",
707 self.tcx.note_and_explain_region(
708 "closure is valid for ",
712 infer::IndexSlice(span) => {
713 span_err!(self.tcx.sess, span, E0475,
714 "index of slice outside its lifetime");
715 self.tcx.note_and_explain_region(
716 "the slice is only valid for ",
720 infer::RelateObjectBound(span) => {
721 span_err!(self.tcx.sess, span, E0476,
722 "lifetime of the source pointer does not outlive \
723 lifetime bound of the object type");
724 self.tcx.note_and_explain_region(
725 "object type is valid for ",
728 self.tcx.note_and_explain_region(
729 "source pointer is only valid for ",
733 infer::RelateParamBound(span, ty) => {
734 span_err!(self.tcx.sess, span, E0477,
735 "the type `{}` does not fulfill the required lifetime",
736 self.ty_to_string(ty));
737 self.tcx.note_and_explain_region(
738 "type must outlive ",
742 infer::RelateRegionParamBound(span) => {
743 span_err!(self.tcx.sess, span, E0478,
744 "lifetime bound not satisfied");
745 self.tcx.note_and_explain_region(
746 "lifetime parameter instantiated with ",
749 self.tcx.note_and_explain_region(
750 "but lifetime parameter must outlive ",
754 infer::RelateDefaultParamBound(span, ty) => {
755 span_err!(self.tcx.sess, span, E0479,
756 "the type `{}` (provided as the value of \
757 a type parameter) is not valid at this point",
758 self.ty_to_string(ty));
759 self.tcx.note_and_explain_region(
760 "type must outlive ",
764 infer::CallRcvr(span) => {
765 span_err!(self.tcx.sess, span, E0480,
766 "lifetime of method receiver does not outlive \
768 self.tcx.note_and_explain_region(
769 "the receiver is only valid for ",
773 infer::CallArg(span) => {
774 span_err!(self.tcx.sess, span, E0481,
775 "lifetime of function argument does not outlive \
777 self.tcx.note_and_explain_region(
778 "the function argument is only valid for ",
782 infer::CallReturn(span) => {
783 span_err!(self.tcx.sess, span, E0482,
784 "lifetime of return value does not outlive \
786 self.tcx.note_and_explain_region(
787 "the return value is only valid for ",
791 infer::Operand(span) => {
792 span_err!(self.tcx.sess, span, E0483,
793 "lifetime of operand does not outlive \
795 self.tcx.note_and_explain_region(
796 "the operand is only valid for ",
800 infer::AddrOf(span) => {
801 span_err!(self.tcx.sess, span, E0484,
802 "reference is not valid at the time of borrow");
803 self.tcx.note_and_explain_region(
804 "the borrow is only valid for ",
808 infer::AutoBorrow(span) => {
809 span_err!(self.tcx.sess, span, E0485,
810 "automatically reference is not valid \
811 at the time of borrow");
812 self.tcx.note_and_explain_region(
813 "the automatic borrow is only valid for ",
817 infer::ExprTypeIsNotInScope(t, span) => {
818 span_err!(self.tcx.sess, span, E0486,
819 "type of expression contains references \
820 that are not valid during the expression: `{}`",
821 self.ty_to_string(t));
822 self.tcx.note_and_explain_region(
823 "type is only valid for ",
827 infer::SafeDestructor(span) => {
828 span_err!(self.tcx.sess, span, E0487,
829 "unsafe use of destructor: destructor might be called \
830 while references are dead");
831 // FIXME (22171): terms "super/subregion" are suboptimal
832 self.tcx.note_and_explain_region(
836 self.tcx.note_and_explain_region(
841 infer::BindingTypeIsNotValidAtDecl(span) => {
842 span_err!(self.tcx.sess, span, E0488,
843 "lifetime of variable does not enclose its declaration");
844 self.tcx.note_and_explain_region(
845 "the variable is only valid for ",
849 infer::ParameterInScope(_, span) => {
850 span_err!(self.tcx.sess, span, E0489,
851 "type/lifetime parameter not in scope here");
852 self.tcx.note_and_explain_region(
853 "the parameter is only valid for ",
857 infer::DataBorrowed(ty, span) => {
858 span_err!(self.tcx.sess, span, E0490,
859 "a value of type `{}` is borrowed for too long",
860 self.ty_to_string(ty));
861 self.tcx.note_and_explain_region("the type is valid for ", sub, "");
862 self.tcx.note_and_explain_region("but the borrow lasts for ", sup, "");
864 infer::ReferenceOutlivesReferent(ty, span) => {
865 span_err!(self.tcx.sess, span, E0491,
866 "in type `{}`, reference has a longer lifetime \
867 than the data it references",
868 self.ty_to_string(ty));
869 self.tcx.note_and_explain_region(
870 "the pointer is valid for ",
873 self.tcx.note_and_explain_region(
874 "but the referenced data is only valid for ",
881 fn report_sub_sup_conflict(&self,
882 var_origin: RegionVariableOrigin,
883 sub_origin: SubregionOrigin<'tcx>,
885 sup_origin: SubregionOrigin<'tcx>,
886 sup_region: Region) {
887 self.report_inference_failure(var_origin);
889 self.tcx.note_and_explain_region(
890 "first, the lifetime cannot outlive ",
894 self.note_region_origin(&sup_origin);
896 self.tcx.note_and_explain_region(
897 "but, the lifetime must be valid for ",
901 self.note_region_origin(&sub_origin);
904 fn report_processed_errors(&self,
905 var_origins: &[RegionVariableOrigin],
906 trace_origins: &[(TypeTrace<'tcx>, TypeError<'tcx>)],
907 same_regions: &[SameRegions]) {
908 for vo in var_origins {
909 self.report_inference_failure(vo.clone());
911 self.give_suggestion(same_regions);
912 for &(ref trace, ref terr) in trace_origins {
913 self.report_and_explain_type_error(trace.clone(), terr);
917 fn give_suggestion(&self, same_regions: &[SameRegions]) {
918 let scope_id = same_regions[0].scope_id;
919 let parent = self.tcx.map.get_parent(scope_id);
920 let parent_node = self.tcx.map.find(parent);
921 let taken = lifetimes_in_scope(self.tcx, scope_id);
922 let life_giver = LifeGiver::with_taken(&taken[..]);
923 let node_inner = match parent_node {
924 Some(ref node) => match *node {
925 ast_map::NodeItem(ref item) => {
927 hir::ItemFn(ref fn_decl, unsafety, constness, _, ref gen, _) => {
928 Some((fn_decl, gen, unsafety, constness,
929 item.name, None, item.span))
934 ast_map::NodeImplItem(item) => {
936 hir::ImplItemKind::Method(ref sig, _) => {
942 Some(&sig.explicit_self.node),
948 ast_map::NodeTraitItem(item) => {
950 hir::MethodTraitItem(ref sig, Some(_)) => {
956 Some(&sig.explicit_self.node),
966 let (fn_decl, generics, unsafety, constness, name, expl_self, span)
967 = node_inner.expect("expect item fn");
968 let rebuilder = Rebuilder::new(self.tcx, fn_decl, expl_self,
969 generics, same_regions, &life_giver);
970 let (fn_decl, expl_self, generics) = rebuilder.rebuild();
971 self.give_expl_lifetime_param(&fn_decl, unsafety, constness, name,
972 expl_self.as_ref(), &generics, span);
976 struct RebuildPathInfo<'a> {
978 // indexes to insert lifetime on path.lifetimes
980 // number of lifetimes we expect to see on the type referred by `path`
981 // (e.g., expected=1 for struct Foo<'a>)
983 anon_nums: &'a HashSet<u32>,
984 region_names: &'a HashSet<ast::Name>
987 struct Rebuilder<'a, 'tcx: 'a> {
988 tcx: &'a ty::ctxt<'tcx>,
989 fn_decl: &'a hir::FnDecl,
990 expl_self_opt: Option<&'a hir::ExplicitSelf_>,
991 generics: &'a hir::Generics,
992 same_regions: &'a [SameRegions],
993 life_giver: &'a LifeGiver,
995 inserted_anons: RefCell<HashSet<u32>>,
1003 impl<'a, 'tcx> Rebuilder<'a, 'tcx> {
1004 fn new(tcx: &'a ty::ctxt<'tcx>,
1005 fn_decl: &'a hir::FnDecl,
1006 expl_self_opt: Option<&'a hir::ExplicitSelf_>,
1007 generics: &'a hir::Generics,
1008 same_regions: &'a [SameRegions],
1009 life_giver: &'a LifeGiver)
1010 -> Rebuilder<'a, 'tcx> {
1014 expl_self_opt: expl_self_opt,
1016 same_regions: same_regions,
1017 life_giver: life_giver,
1018 cur_anon: Cell::new(0),
1019 inserted_anons: RefCell::new(HashSet::new()),
1024 -> (hir::FnDecl, Option<hir::ExplicitSelf_>, hir::Generics) {
1025 let mut expl_self_opt = self.expl_self_opt.cloned();
1026 let mut inputs = self.fn_decl.inputs.clone();
1027 let mut output = self.fn_decl.output.clone();
1028 let mut ty_params = self.generics.ty_params.clone();
1029 let where_clause = self.generics.where_clause.clone();
1030 let mut kept_lifetimes = HashSet::new();
1031 for sr in self.same_regions {
1032 self.cur_anon.set(0);
1033 self.offset_cur_anon();
1034 let (anon_nums, region_names) =
1035 self.extract_anon_nums_and_names(sr);
1036 let (lifetime, fresh_or_kept) = self.pick_lifetime(®ion_names);
1037 match fresh_or_kept {
1038 Kept => { kept_lifetimes.insert(lifetime.name); }
1041 expl_self_opt = self.rebuild_expl_self(expl_self_opt, lifetime,
1042 &anon_nums, ®ion_names);
1043 inputs = self.rebuild_args_ty(&inputs[..], lifetime,
1044 &anon_nums, ®ion_names);
1045 output = self.rebuild_output(&output, lifetime, &anon_nums, ®ion_names);
1046 ty_params = self.rebuild_ty_params(ty_params, lifetime,
1049 let fresh_lifetimes = self.life_giver.get_generated_lifetimes();
1050 let all_region_names = self.extract_all_region_names();
1051 let generics = self.rebuild_generics(self.generics,
1057 let new_fn_decl = hir::FnDecl {
1060 variadic: self.fn_decl.variadic
1062 (new_fn_decl, expl_self_opt, generics)
1065 fn pick_lifetime(&self,
1066 region_names: &HashSet<ast::Name>)
1067 -> (hir::Lifetime, FreshOrKept) {
1068 if !region_names.is_empty() {
1069 // It's not necessary to convert the set of region names to a
1070 // vector of string and then sort them. However, it makes the
1071 // choice of lifetime name deterministic and thus easier to test.
1072 let mut names = Vec::new();
1073 for rn in region_names {
1074 let lt_name = rn.to_string();
1075 names.push(lt_name);
1078 let name = token::intern(&names[0]);
1079 return (name_to_dummy_lifetime(name), Kept);
1081 return (self.life_giver.give_lifetime(), Fresh);
1084 fn extract_anon_nums_and_names(&self, same_regions: &SameRegions)
1085 -> (HashSet<u32>, HashSet<ast::Name>) {
1086 let mut anon_nums = HashSet::new();
1087 let mut region_names = HashSet::new();
1088 for br in &same_regions.regions {
1091 anon_nums.insert(i);
1093 ty::BrNamed(_, name) => {
1094 region_names.insert(name);
1099 (anon_nums, region_names)
1102 fn extract_all_region_names(&self) -> HashSet<ast::Name> {
1103 let mut all_region_names = HashSet::new();
1104 for sr in self.same_regions {
1105 for br in &sr.regions {
1107 ty::BrNamed(_, name) => {
1108 all_region_names.insert(name);
1117 fn inc_cur_anon(&self, n: u32) {
1118 let anon = self.cur_anon.get();
1119 self.cur_anon.set(anon+n);
1122 fn offset_cur_anon(&self) {
1123 let mut anon = self.cur_anon.get();
1124 while self.inserted_anons.borrow().contains(&anon) {
1127 self.cur_anon.set(anon);
1130 fn inc_and_offset_cur_anon(&self, n: u32) {
1131 self.inc_cur_anon(n);
1132 self.offset_cur_anon();
1135 fn track_anon(&self, anon: u32) {
1136 self.inserted_anons.borrow_mut().insert(anon);
1139 fn rebuild_ty_params(&self,
1140 ty_params: hir::HirVec<hir::TyParam>,
1141 lifetime: hir::Lifetime,
1142 region_names: &HashSet<ast::Name>)
1143 -> hir::HirVec<hir::TyParam> {
1144 ty_params.iter().map(|ty_param| {
1145 let bounds = self.rebuild_ty_param_bounds(ty_param.bounds.clone(),
1149 name: ty_param.name,
1152 default: ty_param.default.clone(),
1153 span: ty_param.span,
1158 fn rebuild_ty_param_bounds(&self,
1159 ty_param_bounds: hir::TyParamBounds,
1160 lifetime: hir::Lifetime,
1161 region_names: &HashSet<ast::Name>)
1162 -> hir::TyParamBounds {
1163 ty_param_bounds.iter().map(|tpb| {
1165 &hir::RegionTyParamBound(lt) => {
1166 // FIXME -- it's unclear whether I'm supposed to
1167 // substitute lifetime here. I suspect we need to
1168 // be passing down a map.
1169 hir::RegionTyParamBound(lt)
1171 &hir::TraitTyParamBound(ref poly_tr, modifier) => {
1172 let tr = &poly_tr.trait_ref;
1173 let last_seg = tr.path.segments.last().unwrap();
1174 let mut insert = Vec::new();
1175 let lifetimes = last_seg.parameters.lifetimes();
1176 for (i, lt) in lifetimes.iter().enumerate() {
1177 if region_names.contains(<.name) {
1178 insert.push(i as u32);
1181 let rebuild_info = RebuildPathInfo {
1184 expected: lifetimes.len() as u32,
1185 anon_nums: &HashSet::new(),
1186 region_names: region_names
1188 let new_path = self.rebuild_path(rebuild_info, lifetime);
1189 hir::TraitTyParamBound(hir::PolyTraitRef {
1190 bound_lifetimes: poly_tr.bound_lifetimes.clone(),
1191 trait_ref: hir::TraitRef {
1202 fn rebuild_expl_self(&self,
1203 expl_self_opt: Option<hir::ExplicitSelf_>,
1204 lifetime: hir::Lifetime,
1205 anon_nums: &HashSet<u32>,
1206 region_names: &HashSet<ast::Name>)
1207 -> Option<hir::ExplicitSelf_> {
1208 match expl_self_opt {
1209 Some(ref expl_self) => match *expl_self {
1210 hir::SelfRegion(lt_opt, muta, id) => match lt_opt {
1211 Some(lt) => if region_names.contains(<.name) {
1212 return Some(hir::SelfRegion(Some(lifetime), muta, id));
1215 let anon = self.cur_anon.get();
1216 self.inc_and_offset_cur_anon(1);
1217 if anon_nums.contains(&anon) {
1218 self.track_anon(anon);
1219 return Some(hir::SelfRegion(Some(lifetime), muta, id));
1230 fn rebuild_generics(&self,
1231 generics: &hir::Generics,
1232 add: &Vec<hir::Lifetime>,
1233 keep: &HashSet<ast::Name>,
1234 remove: &HashSet<ast::Name>,
1235 ty_params: hir::HirVec<hir::TyParam>,
1236 where_clause: hir::WhereClause)
1238 let mut lifetimes = Vec::new();
1240 lifetimes.push(hir::LifetimeDef { lifetime: *lt,
1241 bounds: hir::HirVec::new() });
1243 for lt in &generics.lifetimes {
1244 if keep.contains(<.lifetime.name) ||
1245 !remove.contains(<.lifetime.name) {
1246 lifetimes.push((*lt).clone());
1250 lifetimes: lifetimes.into(),
1251 ty_params: ty_params,
1252 where_clause: where_clause,
1256 fn rebuild_args_ty(&self,
1257 inputs: &[hir::Arg],
1258 lifetime: hir::Lifetime,
1259 anon_nums: &HashSet<u32>,
1260 region_names: &HashSet<ast::Name>)
1261 -> hir::HirVec<hir::Arg> {
1262 let mut new_inputs = Vec::new();
1264 let new_ty = self.rebuild_arg_ty_or_output(&*arg.ty, lifetime,
1265 anon_nums, region_names);
1266 let possibly_new_arg = hir::Arg {
1268 pat: arg.pat.clone(),
1271 new_inputs.push(possibly_new_arg);
1276 fn rebuild_output(&self, ty: &hir::FunctionRetTy,
1277 lifetime: hir::Lifetime,
1278 anon_nums: &HashSet<u32>,
1279 region_names: &HashSet<ast::Name>) -> hir::FunctionRetTy {
1281 hir::Return(ref ret_ty) => hir::Return(
1282 self.rebuild_arg_ty_or_output(&**ret_ty, lifetime, anon_nums, region_names)
1284 hir::DefaultReturn(span) => hir::DefaultReturn(span),
1285 hir::NoReturn(span) => hir::NoReturn(span)
1289 fn rebuild_arg_ty_or_output(&self,
1291 lifetime: hir::Lifetime,
1292 anon_nums: &HashSet<u32>,
1293 region_names: &HashSet<ast::Name>)
1295 let mut new_ty = P(ty.clone());
1296 let mut ty_queue = vec!(ty);
1297 while !ty_queue.is_empty() {
1298 let cur_ty = ty_queue.remove(0);
1300 hir::TyRptr(lt_opt, ref mut_ty) => {
1301 let rebuild = match lt_opt {
1302 Some(lt) => region_names.contains(<.name),
1304 let anon = self.cur_anon.get();
1305 let rebuild = anon_nums.contains(&anon);
1307 self.track_anon(anon);
1309 self.inc_and_offset_cur_anon(1);
1316 node: hir::TyRptr(Some(lifetime), mut_ty.clone()),
1319 new_ty = self.rebuild_ty(new_ty, P(to));
1321 ty_queue.push(&*mut_ty.ty);
1323 hir::TyPath(ref maybe_qself, ref path) => {
1324 let a_def = match self.tcx.def_map.borrow().get(&cur_ty.id) {
1330 pprust::path_to_string(path)))
1332 Some(d) => d.full_def()
1335 def::DefTy(did, _) | def::DefStruct(did) => {
1336 let generics = self.tcx.lookup_item_type(did).generics;
1339 generics.regions.len(subst::TypeSpace) as u32;
1341 path.segments.last().unwrap().parameters.lifetimes();
1342 let mut insert = Vec::new();
1343 if lifetimes.is_empty() {
1344 let anon = self.cur_anon.get();
1345 for (i, a) in (anon..anon+expected).enumerate() {
1346 if anon_nums.contains(&a) {
1347 insert.push(i as u32);
1351 self.inc_and_offset_cur_anon(expected);
1353 for (i, lt) in lifetimes.iter().enumerate() {
1354 if region_names.contains(<.name) {
1355 insert.push(i as u32);
1359 let rebuild_info = RebuildPathInfo {
1363 anon_nums: anon_nums,
1364 region_names: region_names
1366 let new_path = self.rebuild_path(rebuild_info, lifetime);
1367 let qself = maybe_qself.as_ref().map(|qself| {
1369 ty: self.rebuild_arg_ty_or_output(&qself.ty, lifetime,
1370 anon_nums, region_names),
1371 position: qself.position
1376 node: hir::TyPath(qself, new_path),
1379 new_ty = self.rebuild_ty(new_ty, P(to));
1386 hir::TyPtr(ref mut_ty) => {
1387 ty_queue.push(&*mut_ty.ty);
1389 hir::TyVec(ref ty) |
1390 hir::TyFixedLengthVec(ref ty, _) => {
1391 ty_queue.push(&**ty);
1393 hir::TyTup(ref tys) => ty_queue.extend(tys.iter().map(|ty| &**ty)),
1400 fn rebuild_ty(&self,
1405 fn build_to(from: P<hir::Ty>,
1406 to: &mut Option<P<hir::Ty>>)
1408 if Some(from.id) == to.as_ref().map(|ty| ty.id) {
1409 return to.take().expect("`to` type found more than once during rebuild");
1411 from.map(|hir::Ty {id, node, span}| {
1412 let new_node = match node {
1413 hir::TyRptr(lifetime, mut_ty) => {
1414 hir::TyRptr(lifetime, hir::MutTy {
1415 mutbl: mut_ty.mutbl,
1416 ty: build_to(mut_ty.ty, to),
1419 hir::TyPtr(mut_ty) => {
1420 hir::TyPtr(hir::MutTy {
1421 mutbl: mut_ty.mutbl,
1422 ty: build_to(mut_ty.ty, to),
1425 hir::TyVec(ty) => hir::TyVec(build_to(ty, to)),
1426 hir::TyFixedLengthVec(ty, e) => {
1427 hir::TyFixedLengthVec(build_to(ty, to), e)
1429 hir::TyTup(tys) => {
1430 hir::TyTup(tys.into_iter().map(|ty| build_to(ty, to)).collect())
1434 hir::Ty { id: id, node: new_node, span: span }
1438 build_to(from, &mut Some(to))
1441 fn rebuild_path(&self,
1442 rebuild_info: RebuildPathInfo,
1443 lifetime: hir::Lifetime)
1446 let RebuildPathInfo {
1454 let last_seg = path.segments.last().unwrap();
1455 let new_parameters = match last_seg.parameters {
1456 hir::ParenthesizedParameters(..) => {
1457 last_seg.parameters.clone()
1460 hir::AngleBracketedParameters(ref data) => {
1461 let mut new_lts = Vec::new();
1462 if data.lifetimes.is_empty() {
1463 // traverse once to see if there's a need to insert lifetime
1464 let need_insert = (0..expected).any(|i| {
1465 indexes.contains(&i)
1468 for i in 0..expected {
1469 if indexes.contains(&i) {
1470 new_lts.push(lifetime);
1472 new_lts.push(self.life_giver.give_lifetime());
1477 for (i, lt) in data.lifetimes.iter().enumerate() {
1478 if indexes.contains(&(i as u32)) {
1479 new_lts.push(lifetime);
1485 let new_types = data.types.iter().map(|t| {
1486 self.rebuild_arg_ty_or_output(&**t, lifetime, anon_nums, region_names)
1488 let new_bindings = data.bindings.iter().map(|b| {
1492 ty: self.rebuild_arg_ty_or_output(&*b.ty,
1499 hir::AngleBracketedParameters(hir::AngleBracketedParameterData {
1500 lifetimes: new_lts.into(),
1502 bindings: new_bindings,
1506 let new_seg = hir::PathSegment {
1507 identifier: last_seg.identifier,
1508 parameters: new_parameters
1510 let mut new_segs = Vec::new();
1511 new_segs.extend_from_slice(path.segments.split_last().unwrap().1);
1512 new_segs.push(new_seg);
1515 global: path.global,
1516 segments: new_segs.into()
1521 impl<'a, 'tcx> ErrorReportingHelpers<'tcx> for InferCtxt<'a, 'tcx> {
1522 fn give_expl_lifetime_param(&self,
1524 unsafety: hir::Unsafety,
1525 constness: hir::Constness,
1527 opt_explicit_self: Option<&hir::ExplicitSelf_>,
1528 generics: &hir::Generics,
1530 let suggested_fn = pprust::fun_to_string(decl, unsafety, constness, name,
1531 opt_explicit_self, generics);
1532 let msg = format!("consider using an explicit lifetime \
1533 parameter as shown: {}", suggested_fn);
1534 self.tcx.sess.span_help(span, &msg[..]);
1537 fn report_inference_failure(&self,
1538 var_origin: RegionVariableOrigin) {
1539 let br_string = |br: ty::BoundRegion| {
1540 let mut s = br.to_string();
1546 let var_description = match var_origin {
1547 infer::MiscVariable(_) => "".to_string(),
1548 infer::PatternRegion(_) => " for pattern".to_string(),
1549 infer::AddrOfRegion(_) => " for borrow expression".to_string(),
1550 infer::Autoref(_) => " for autoref".to_string(),
1551 infer::Coercion(_) => " for automatic coercion".to_string(),
1552 infer::LateBoundRegion(_, br, infer::FnCall) => {
1553 format!(" for lifetime parameter {}in function call",
1556 infer::LateBoundRegion(_, br, infer::HigherRankedType) => {
1557 format!(" for lifetime parameter {}in generic type", br_string(br))
1559 infer::LateBoundRegion(_, br, infer::AssocTypeProjection(type_name)) => {
1560 format!(" for lifetime parameter {}in trait containing associated type `{}`",
1561 br_string(br), type_name)
1563 infer::EarlyBoundRegion(_, name) => {
1564 format!(" for lifetime parameter `{}`",
1567 infer::BoundRegionInCoherence(name) => {
1568 format!(" for lifetime parameter `{}` in coherence check",
1571 infer::UpvarRegion(ref upvar_id, _) => {
1572 format!(" for capture of `{}` by closure",
1573 self.tcx.local_var_name_str(upvar_id.var_id).to_string())
1577 span_err!(self.tcx.sess, var_origin.span(), E0495,
1578 "cannot infer an appropriate lifetime{} \
1579 due to conflicting requirements",
1583 fn note_region_origin(&self, origin: &SubregionOrigin<'tcx>) {
1585 infer::Subtype(ref trace) => {
1586 let desc = match trace.origin {
1587 TypeOrigin::Misc(_) => {
1588 "types are compatible"
1590 TypeOrigin::MethodCompatCheck(_) => {
1591 "method type is compatible with trait"
1593 TypeOrigin::ExprAssignable(_) => {
1594 "expression is assignable"
1596 TypeOrigin::RelateTraitRefs(_) => {
1597 "traits are compatible"
1599 TypeOrigin::RelateSelfType(_) => {
1600 "self type matches impl self type"
1602 TypeOrigin::RelateOutputImplTypes(_) => {
1603 "trait type parameters matches those \
1604 specified on the impl"
1606 TypeOrigin::MatchExpressionArm(_, _, _) => {
1607 "match arms have compatible types"
1609 TypeOrigin::IfExpression(_) => {
1610 "if and else have compatible types"
1612 TypeOrigin::IfExpressionWithNoElse(_) => {
1613 "if may be missing an else clause"
1615 TypeOrigin::RangeExpression(_) => {
1616 "start and end of range have compatible types"
1618 TypeOrigin::EquatePredicate(_) => {
1619 "equality where clause is satisfied"
1623 match self.values_str(&trace.values) {
1624 Some(values_str) => {
1625 self.tcx.sess.span_note(
1626 trace.origin.span(),
1627 &format!("...so that {} ({})",
1631 // Really should avoid printing this error at
1632 // all, since it is derived, but that would
1633 // require more refactoring than I feel like
1634 // doing right now. - nmatsakis
1635 self.tcx.sess.span_note(
1636 trace.origin.span(),
1637 &format!("...so that {}", desc));
1641 infer::Reborrow(span) => {
1642 self.tcx.sess.span_note(
1644 "...so that reference does not outlive \
1647 infer::ReborrowUpvar(span, ref upvar_id) => {
1648 self.tcx.sess.span_note(
1651 "...so that closure can access `{}`",
1652 self.tcx.local_var_name_str(upvar_id.var_id)
1655 infer::InfStackClosure(span) => {
1656 self.tcx.sess.span_note(
1658 "...so that closure does not outlive its stack frame");
1660 infer::InvokeClosure(span) => {
1661 self.tcx.sess.span_note(
1663 "...so that closure is not invoked outside its lifetime");
1665 infer::DerefPointer(span) => {
1666 self.tcx.sess.span_note(
1668 "...so that pointer is not dereferenced \
1669 outside its lifetime");
1671 infer::FreeVariable(span, id) => {
1672 self.tcx.sess.span_note(
1674 &format!("...so that captured variable `{}` \
1675 does not outlive the enclosing closure",
1676 self.tcx.local_var_name_str(id)));
1678 infer::IndexSlice(span) => {
1679 self.tcx.sess.span_note(
1681 "...so that slice is not indexed outside the lifetime");
1683 infer::RelateObjectBound(span) => {
1684 self.tcx.sess.span_note(
1686 "...so that it can be closed over into an object");
1688 infer::CallRcvr(span) => {
1689 self.tcx.sess.span_note(
1691 "...so that method receiver is valid for the method call");
1693 infer::CallArg(span) => {
1694 self.tcx.sess.span_note(
1696 "...so that argument is valid for the call");
1698 infer::CallReturn(span) => {
1699 self.tcx.sess.span_note(
1701 "...so that return value is valid for the call");
1703 infer::Operand(span) => {
1704 self.tcx.sess.span_note(
1706 "...so that operand is valid for operation");
1708 infer::AddrOf(span) => {
1709 self.tcx.sess.span_note(
1711 "...so that reference is valid \
1712 at the time of borrow");
1714 infer::AutoBorrow(span) => {
1715 self.tcx.sess.span_note(
1717 "...so that auto-reference is valid \
1718 at the time of borrow");
1720 infer::ExprTypeIsNotInScope(t, span) => {
1721 self.tcx.sess.span_note(
1723 &format!("...so type `{}` of expression is valid during the \
1725 self.ty_to_string(t)));
1727 infer::BindingTypeIsNotValidAtDecl(span) => {
1728 self.tcx.sess.span_note(
1730 "...so that variable is valid at time of its declaration");
1732 infer::ParameterInScope(_, span) => {
1733 self.tcx.sess.span_note(
1735 "...so that a type/lifetime parameter is in scope here");
1737 infer::DataBorrowed(ty, span) => {
1738 self.tcx.sess.span_note(
1740 &format!("...so that the type `{}` is not borrowed for too long",
1741 self.ty_to_string(ty)));
1743 infer::ReferenceOutlivesReferent(ty, span) => {
1744 self.tcx.sess.span_note(
1746 &format!("...so that the reference type `{}` \
1747 does not outlive the data it points at",
1748 self.ty_to_string(ty)));
1750 infer::RelateParamBound(span, t) => {
1751 self.tcx.sess.span_note(
1753 &format!("...so that the type `{}` \
1754 will meet its required lifetime bounds",
1755 self.ty_to_string(t)));
1757 infer::RelateDefaultParamBound(span, t) => {
1758 self.tcx.sess.span_note(
1760 &format!("...so that type parameter \
1761 instantiated with `{}`, \
1762 will meet its declared lifetime bounds",
1763 self.ty_to_string(t)));
1765 infer::RelateRegionParamBound(span) => {
1766 self.tcx.sess.span_note(
1768 "...so that the declared lifetime parameter bounds \
1771 infer::SafeDestructor(span) => {
1772 self.tcx.sess.span_note(
1774 "...so that references are valid when the destructor \
1781 pub trait Resolvable<'tcx> {
1782 fn resolve<'a>(&self, infcx: &InferCtxt<'a, 'tcx>) -> Self;
1785 impl<'tcx> Resolvable<'tcx> for Ty<'tcx> {
1786 fn resolve<'a>(&self, infcx: &InferCtxt<'a, 'tcx>) -> Ty<'tcx> {
1787 infcx.resolve_type_vars_if_possible(self)
1791 impl<'tcx> Resolvable<'tcx> for ty::TraitRef<'tcx> {
1792 fn resolve<'a>(&self, infcx: &InferCtxt<'a, 'tcx>)
1793 -> ty::TraitRef<'tcx> {
1794 infcx.resolve_type_vars_if_possible(self)
1798 impl<'tcx> Resolvable<'tcx> for ty::PolyTraitRef<'tcx> {
1799 fn resolve<'a>(&self,
1800 infcx: &InferCtxt<'a, 'tcx>)
1801 -> ty::PolyTraitRef<'tcx>
1803 infcx.resolve_type_vars_if_possible(self)
1807 fn lifetimes_in_scope(tcx: &ty::ctxt,
1808 scope_id: ast::NodeId)
1809 -> Vec<hir::LifetimeDef> {
1810 let mut taken = Vec::new();
1811 let parent = tcx.map.get_parent(scope_id);
1812 let method_id_opt = match tcx.map.find(parent) {
1813 Some(node) => match node {
1814 ast_map::NodeItem(item) => match item.node {
1815 hir::ItemFn(_, _, _, _, ref gen, _) => {
1816 taken.extend_from_slice(&gen.lifetimes);
1821 ast_map::NodeImplItem(ii) => {
1823 hir::ImplItemKind::Method(ref sig, _) => {
1824 taken.extend_from_slice(&sig.generics.lifetimes);
1834 if method_id_opt.is_some() {
1835 let method_id = method_id_opt.unwrap();
1836 let parent = tcx.map.get_parent(method_id);
1837 match tcx.map.find(parent) {
1838 Some(node) => match node {
1839 ast_map::NodeItem(item) => match item.node {
1840 hir::ItemImpl(_, _, ref gen, _, _, _) => {
1841 taken.extend_from_slice(&gen.lifetimes);
1853 // LifeGiver is responsible for generating fresh lifetime names
1855 taken: HashSet<String>,
1856 counter: Cell<usize>,
1857 generated: RefCell<Vec<hir::Lifetime>>,
1861 fn with_taken(taken: &[hir::LifetimeDef]) -> LifeGiver {
1862 let mut taken_ = HashSet::new();
1864 let lt_name = lt.lifetime.name.to_string();
1865 taken_.insert(lt_name);
1869 counter: Cell::new(0),
1870 generated: RefCell::new(Vec::new()),
1874 fn inc_counter(&self) {
1875 let c = self.counter.get();
1876 self.counter.set(c+1);
1879 fn give_lifetime(&self) -> hir::Lifetime {
1882 let mut s = String::from("'");
1883 s.push_str(&num_to_string(self.counter.get()));
1884 if !self.taken.contains(&s) {
1885 lifetime = name_to_dummy_lifetime(token::intern(&s[..]));
1886 self.generated.borrow_mut().push(lifetime);
1894 // 0 .. 25 generates a .. z, 26 .. 51 generates aa .. zz, and so on
1895 fn num_to_string(counter: usize) -> String {
1896 let mut s = String::new();
1897 let (n, r) = (counter/26 + 1, counter % 26);
1898 let letter: char = from_u32((r+97) as u32).unwrap();
1906 fn get_generated_lifetimes(&self) -> Vec<hir::Lifetime> {
1907 self.generated.borrow().clone()
1911 fn name_to_dummy_lifetime(name: ast::Name) -> hir::Lifetime {
1912 hir::Lifetime { id: ast::DUMMY_NODE_ID,
1913 span: codemap::DUMMY_SP,