1 // Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
11 //! See The Book chapter on the borrow checker for more details.
13 #![allow(non_camel_case_types)]
15 pub use self::LoanPathKind::*;
16 pub use self::LoanPathElem::*;
17 pub use self::bckerr_code::*;
18 pub use self::AliasableViolationKind::*;
19 pub use self::MovedValueUseKind::*;
21 use self::InteriorKind::*;
23 use rustc::hir::HirId;
24 use rustc::hir::map as hir_map;
25 use rustc::hir::map::blocks::FnLikeNode;
27 use rustc::middle::dataflow::DataFlowContext;
28 use rustc::middle::dataflow::BitwiseOperator;
29 use rustc::middle::dataflow::DataFlowOperator;
30 use rustc::middle::dataflow::KillFrom;
31 use rustc::middle::borrowck::BorrowCheckResult;
32 use rustc::hir::def_id::{DefId, LocalDefId};
33 use rustc::middle::expr_use_visitor as euv;
34 use rustc::middle::mem_categorization as mc;
35 use rustc::middle::mem_categorization::Categorization;
36 use rustc::middle::mem_categorization::ImmutabilityBlame;
37 use rustc::middle::region;
38 use rustc::middle::free_region::RegionRelations;
39 use rustc::ty::{self, Ty, TyCtxt};
40 use rustc::ty::maps::Providers;
41 use rustc_mir::util::borrowck_errors::{BorrowckErrors, Origin};
42 use rustc::util::nodemap::FxHashSet;
44 use std::cell::RefCell;
47 use rustc_data_structures::sync::Lrc;
48 use std::hash::{Hash, Hasher};
50 use syntax_pos::{MultiSpan, Span};
51 use errors::{DiagnosticBuilder, DiagnosticId};
54 use rustc::hir::intravisit::{self, Visitor};
64 #[derive(Clone, Copy)]
65 pub struct LoanDataFlowOperator;
67 pub type LoanDataFlow<'a, 'tcx> = DataFlowContext<'a, 'tcx, LoanDataFlowOperator>;
69 pub fn check_crate<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>) {
70 for body_owner_def_id in tcx.body_owners() {
71 tcx.borrowck(body_owner_def_id);
75 pub fn provide(providers: &mut Providers) {
76 *providers = Providers {
82 /// Collection of conclusions determined via borrow checker analyses.
83 pub struct AnalysisData<'a, 'tcx: 'a> {
84 pub all_loans: Vec<Loan<'tcx>>,
85 pub loans: DataFlowContext<'a, 'tcx, LoanDataFlowOperator>,
86 pub move_data: move_data::FlowedMoveData<'a, 'tcx>,
89 fn borrowck<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, owner_def_id: DefId)
90 -> Lrc<BorrowCheckResult>
92 debug!("borrowck(body_owner_def_id={:?})", owner_def_id);
94 let owner_id = tcx.hir.as_local_node_id(owner_def_id).unwrap();
96 match tcx.hir.get(owner_id) {
97 hir_map::NodeStructCtor(_) |
98 hir_map::NodeVariant(_) => {
99 // We get invoked with anything that has MIR, but some of
100 // those things (notably the synthesized constructors from
101 // tuple structs/variants) do not have an associated body
102 // and do not need borrowchecking.
103 return Lrc::new(BorrowCheckResult {
104 used_mut_nodes: FxHashSet(),
110 let body_id = tcx.hir.body_owned_by(owner_id);
111 let tables = tcx.typeck_tables_of(owner_def_id);
112 let region_scope_tree = tcx.region_scope_tree(owner_def_id);
113 let body = tcx.hir.body(body_id);
114 let mut bccx = BorrowckCtxt {
120 used_mut_nodes: RefCell::new(FxHashSet()),
123 // Eventually, borrowck will always read the MIR, but at the
124 // moment we do not. So, for now, we always force MIR to be
125 // constructed for a given fn, since this may result in errors
126 // being reported and we want that to happen.
128 // Note that `mir_validated` is a "stealable" result; the
129 // thief, `optimized_mir()`, forces borrowck, so we know that
130 // is not yet stolen.
131 tcx.mir_validated(owner_def_id).borrow();
133 // option dance because you can't capture an uninitialized variable
136 if let Some(AnalysisData { all_loans,
138 move_data: flowed_moves }) =
139 build_borrowck_dataflow_data(&mut bccx, false, body_id,
141 cfg = Some(cfg::CFG::new(bccx.tcx, &body));
142 cfg.as_mut().unwrap()
145 check_loans::check_loans(&mut bccx, &loan_dfcx, &flowed_moves, &all_loans, body);
147 unused::check(&mut bccx, body);
149 Lrc::new(BorrowCheckResult {
150 used_mut_nodes: bccx.used_mut_nodes.into_inner(),
154 fn build_borrowck_dataflow_data<'a, 'c, 'tcx, F>(this: &mut BorrowckCtxt<'a, 'tcx>,
155 force_analysis: bool,
156 body_id: hir::BodyId,
158 -> Option<AnalysisData<'a, 'tcx>>
159 where F: FnOnce(&mut BorrowckCtxt<'a, 'tcx>) -> &'c cfg::CFG
161 // Check the body of fn items.
164 let mut visitor = intravisit::IdRangeComputingVisitor::new(&tcx.hir);
165 visitor.visit_body(this.body);
168 let (all_loans, move_data) =
169 gather_loans::gather_loans_in_fn(this, body_id);
171 if !force_analysis && move_data.is_empty() && all_loans.is_empty() {
172 // large arrays of data inserted as constants can take a lot of
173 // time and memory to borrow-check - see issue #36799. However,
174 // they don't have places, so no borrow-check is actually needed.
175 // Recognize that case and skip borrow-checking.
176 debug!("skipping loan propagation for {:?} because of no loans", body_id);
179 debug!("propagating loans in {:?}", body_id);
182 let cfg = get_cfg(this);
184 DataFlowContext::new(this.tcx,
188 LoanDataFlowOperator,
191 for (loan_idx, loan) in all_loans.iter().enumerate() {
192 loan_dfcx.add_gen(loan.gen_scope.item_local_id(), loan_idx);
193 loan_dfcx.add_kill(KillFrom::ScopeEnd,
194 loan.kill_scope.item_local_id(),
197 loan_dfcx.add_kills_from_flow_exits(cfg);
198 loan_dfcx.propagate(cfg, this.body);
200 let flowed_moves = move_data::FlowedMoveData::new(move_data,
206 Some(AnalysisData { all_loans,
208 move_data:flowed_moves })
211 /// Accessor for introspective clients inspecting `AnalysisData` and
212 /// the `BorrowckCtxt` itself , e.g. the flowgraph visualizer.
213 pub fn build_borrowck_dataflow_data_for_fn<'a, 'tcx>(
214 tcx: TyCtxt<'a, 'tcx, 'tcx>,
215 body_id: hir::BodyId,
217 -> (BorrowckCtxt<'a, 'tcx>, AnalysisData<'a, 'tcx>)
219 let owner_id = tcx.hir.body_owner(body_id);
220 let owner_def_id = tcx.hir.local_def_id(owner_id);
221 let tables = tcx.typeck_tables_of(owner_def_id);
222 let region_scope_tree = tcx.region_scope_tree(owner_def_id);
223 let body = tcx.hir.body(body_id);
224 let mut bccx = BorrowckCtxt {
230 used_mut_nodes: RefCell::new(FxHashSet()),
233 let dataflow_data = build_borrowck_dataflow_data(&mut bccx, true, body_id, |_| cfg);
234 (bccx, dataflow_data.unwrap())
237 // ----------------------------------------------------------------------
240 pub struct BorrowckCtxt<'a, 'tcx: 'a> {
241 tcx: TyCtxt<'a, 'tcx, 'tcx>,
243 // tables for the current thing we are checking; set to
244 // Some in `borrowck_fn` and cleared later
245 tables: &'a ty::TypeckTables<'tcx>,
247 region_scope_tree: Lrc<region::ScopeTree>,
251 body: &'tcx hir::Body,
253 used_mut_nodes: RefCell<FxHashSet<HirId>>,
256 impl<'b, 'tcx: 'b> BorrowckErrors for BorrowckCtxt<'b, 'tcx> {
257 fn struct_span_err_with_code<'a, S: Into<MultiSpan>>(&'a self,
261 -> DiagnosticBuilder<'a>
263 self.tcx.sess.struct_span_err_with_code(sp, msg, code)
266 fn struct_span_err<'a, S: Into<MultiSpan>>(&'a self,
269 -> DiagnosticBuilder<'a>
271 self.tcx.sess.struct_span_err(sp, msg)
274 fn cancel_if_wrong_origin<'a>(&'a self,
275 mut diag: DiagnosticBuilder<'a>,
277 -> DiagnosticBuilder<'a>
279 if !o.should_emit_errors(self.tcx.borrowck_mode()) {
280 self.tcx.sess.diagnostic().cancel(&mut diag);
286 ///////////////////////////////////////////////////////////////////////////
287 // Loans and loan paths
289 /// Record of a loan that was issued.
290 pub struct Loan<'tcx> {
292 loan_path: Rc<LoanPath<'tcx>>,
293 kind: ty::BorrowKind,
294 restricted_paths: Vec<Rc<LoanPath<'tcx>>>,
296 /// gen_scope indicates where loan is introduced. Typically the
297 /// loan is introduced at the point of the borrow, but in some
298 /// cases, notably method arguments, the loan may be introduced
299 /// only later, once it comes into scope. See also
300 /// `GatherLoanCtxt::compute_gen_scope`.
301 gen_scope: region::Scope,
303 /// kill_scope indicates when the loan goes out of scope. This is
304 /// either when the lifetime expires or when the local variable
305 /// which roots the loan-path goes out of scope, whichever happens
306 /// faster. See also `GatherLoanCtxt::compute_kill_scope`.
307 kill_scope: region::Scope,
309 cause: euv::LoanCause,
312 impl<'tcx> Loan<'tcx> {
313 pub fn loan_path(&self) -> Rc<LoanPath<'tcx>> {
314 self.loan_path.clone()
319 pub struct LoanPath<'tcx> {
320 kind: LoanPathKind<'tcx>,
324 impl<'tcx> PartialEq for LoanPath<'tcx> {
325 fn eq(&self, that: &LoanPath<'tcx>) -> bool {
326 self.kind == that.kind
330 impl<'tcx> Hash for LoanPath<'tcx> {
331 fn hash<H: Hasher>(&self, state: &mut H) {
332 self.kind.hash(state);
336 #[derive(PartialEq, Eq, Hash, Debug)]
337 pub enum LoanPathKind<'tcx> {
338 LpVar(ast::NodeId), // `x` in README.md
339 LpUpvar(ty::UpvarId), // `x` captured by-value into closure
340 LpDowncast(Rc<LoanPath<'tcx>>, DefId), // `x` downcast to particular enum variant
341 LpExtend(Rc<LoanPath<'tcx>>, mc::MutabilityCategory, LoanPathElem<'tcx>)
344 impl<'tcx> LoanPath<'tcx> {
345 fn new(kind: LoanPathKind<'tcx>, ty: Ty<'tcx>) -> LoanPath<'tcx> {
346 LoanPath { kind: kind, ty: ty }
349 fn to_type(&self) -> Ty<'tcx> { self.ty }
351 fn has_downcast(&self) -> bool {
353 LpDowncast(_, _) => true,
354 LpExtend(ref lp, _, LpInterior(_, _)) => {
362 // FIXME (pnkfelix): See discussion here
363 // https://github.com/pnkfelix/rust/commit/
364 // b2b39e8700e37ad32b486b9a8409b50a8a53aa51#commitcomment-7892003
365 const DOWNCAST_PRINTED_OPERATOR: &'static str = " as ";
367 // A local, "cleaned" version of `mc::InteriorKind` that drops
368 // information that is not relevant to loan-path analysis. (In
369 // particular, the distinction between how precisely an array-element
370 // is tracked is irrelevant here.)
371 #[derive(Clone, Copy, PartialEq, Eq, Hash)]
372 pub enum InteriorKind {
373 InteriorField(mc::FieldName),
377 trait ToInteriorKind { fn cleaned(self) -> InteriorKind; }
378 impl ToInteriorKind for mc::InteriorKind {
379 fn cleaned(self) -> InteriorKind {
381 mc::InteriorField(name) => InteriorField(name),
382 mc::InteriorElement(_) => InteriorElement,
388 // - a pointer dereference (`*P` in README.md)
389 // - a field reference, with an optional definition of the containing
390 // enum variant (`P.f` in README.md)
391 // `DefId` is present when the field is part of struct that is in
392 // a variant of an enum. For instance in:
393 // `enum E { X { foo: u32 }, Y { foo: u32 }}`
394 // each `foo` is qualified by the definitition id of the variant (`X` or `Y`).
395 #[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
396 pub enum LoanPathElem<'tcx> {
397 LpDeref(mc::PointerKind<'tcx>),
398 LpInterior(Option<DefId>, InteriorKind),
401 fn closure_to_block(closure_id: LocalDefId,
402 tcx: TyCtxt) -> ast::NodeId {
403 let closure_id = tcx.hir.local_def_id_to_node_id(closure_id);
404 match tcx.hir.get(closure_id) {
405 hir_map::NodeExpr(expr) => match expr.node {
406 hir::ExprClosure(.., body_id, _, _) => {
410 bug!("encountered non-closure id: {}", closure_id)
413 _ => bug!("encountered non-expr id: {}", closure_id)
417 impl<'a, 'tcx> LoanPath<'tcx> {
418 pub fn kill_scope(&self, bccx: &BorrowckCtxt<'a, 'tcx>) -> region::Scope {
421 let hir_id = bccx.tcx.hir.node_to_hir_id(local_id);
422 bccx.region_scope_tree.var_scope(hir_id.local_id)
424 LpUpvar(upvar_id) => {
425 let block_id = closure_to_block(upvar_id.closure_expr_id, bccx.tcx);
426 let hir_id = bccx.tcx.hir.node_to_hir_id(block_id);
427 region::Scope::Node(hir_id.local_id)
429 LpDowncast(ref base, _) |
430 LpExtend(ref base, ..) => base.kill_scope(bccx),
434 fn has_fork(&self, other: &LoanPath<'tcx>) -> bool {
435 match (&self.kind, &other.kind) {
436 (&LpExtend(ref base, _, LpInterior(opt_variant_id, id)),
437 &LpExtend(ref base2, _, LpInterior(opt_variant_id2, id2))) =>
438 if id == id2 && opt_variant_id == opt_variant_id2 {
439 base.has_fork(&base2)
443 (&LpExtend(ref base, _, LpDeref(_)), _) => base.has_fork(other),
444 (_, &LpExtend(ref base, _, LpDeref(_))) => self.has_fork(&base),
449 fn depth(&self) -> usize {
451 LpExtend(ref base, _, LpDeref(_)) => base.depth(),
452 LpExtend(ref base, _, LpInterior(..)) => base.depth() + 1,
457 fn common(&self, other: &LoanPath<'tcx>) -> Option<LoanPath<'tcx>> {
458 match (&self.kind, &other.kind) {
459 (&LpExtend(ref base, a, LpInterior(opt_variant_id, id)),
460 &LpExtend(ref base2, _, LpInterior(opt_variant_id2, id2))) => {
461 if id == id2 && opt_variant_id == opt_variant_id2 {
462 base.common(&base2).map(|x| {
464 if base.depth() == xd && base2.depth() == xd {
466 kind: LpExtend(Rc::new(x), a, LpInterior(opt_variant_id, id)),
477 (&LpExtend(ref base, _, LpDeref(_)), _) => base.common(other),
478 (_, &LpExtend(ref other, _, LpDeref(_))) => self.common(&other),
479 (&LpVar(id), &LpVar(id2)) => {
481 Some(LoanPath { kind: LpVar(id), ty: self.ty })
486 (&LpUpvar(id), &LpUpvar(id2)) => {
488 Some(LoanPath { kind: LpUpvar(id), ty: self.ty })
498 // Avoid "cannot borrow immutable field `self.x` as mutable" as that implies that a field *can* be
499 // mutable independently of the struct it belongs to. (#35937)
500 pub fn opt_loan_path_is_field<'tcx>(cmt: &mc::cmt<'tcx>) -> (Option<Rc<LoanPath<'tcx>>>, bool) {
501 let new_lp = |v: LoanPathKind<'tcx>| Rc::new(LoanPath::new(v, cmt.ty));
504 Categorization::Rvalue(..) |
505 Categorization::StaticItem => {
509 Categorization::Local(id) => {
510 (Some(new_lp(LpVar(id))), false)
513 Categorization::Upvar(mc::Upvar { id, .. }) => {
514 (Some(new_lp(LpUpvar(id))), false)
517 Categorization::Deref(ref cmt_base, pk) => {
518 let lp = opt_loan_path_is_field(cmt_base);
520 new_lp(LpExtend(lp, cmt.mutbl, LpDeref(pk)))
524 Categorization::Interior(ref cmt_base, ik) => {
525 (opt_loan_path(cmt_base).map(|lp| {
526 let opt_variant_id = match cmt_base.cat {
527 Categorization::Downcast(_, did) => Some(did),
530 new_lp(LpExtend(lp, cmt.mutbl, LpInterior(opt_variant_id, ik.cleaned())))
534 Categorization::Downcast(ref cmt_base, variant_def_id) => {
535 let lp = opt_loan_path_is_field(cmt_base);
537 new_lp(LpDowncast(lp, variant_def_id))
543 /// Computes the `LoanPath` (if any) for a `cmt`.
544 /// Note that this logic is somewhat duplicated in
545 /// the method `compute()` found in `gather_loans::restrictions`,
546 /// which allows it to share common loan path pieces as it
547 /// traverses the CMT.
548 pub fn opt_loan_path<'tcx>(cmt: &mc::cmt<'tcx>) -> Option<Rc<LoanPath<'tcx>>> {
549 opt_loan_path_is_field(cmt).0
552 ///////////////////////////////////////////////////////////////////////////
555 // Errors that can occur
556 #[derive(Debug, PartialEq)]
557 pub enum bckerr_code<'tcx> {
559 /// superscope, subscope, loan cause
560 err_out_of_scope(ty::Region<'tcx>, ty::Region<'tcx>, euv::LoanCause),
561 err_borrowed_pointer_too_short(ty::Region<'tcx>, ty::Region<'tcx>), // loan, ptr
564 // Combination of an error code and the categorization of the expression
566 #[derive(Debug, PartialEq)]
567 pub struct BckError<'tcx> {
569 cause: AliasableViolationKind,
571 code: bckerr_code<'tcx>
574 #[derive(Copy, Clone, Debug, PartialEq)]
575 pub enum AliasableViolationKind {
577 BorrowViolation(euv::LoanCause)
580 #[derive(Copy, Clone, Debug)]
581 pub enum MovedValueUseKind {
586 ///////////////////////////////////////////////////////////////////////////
589 impl<'a, 'tcx> BorrowckCtxt<'a, 'tcx> {
590 pub fn is_subregion_of(&self,
591 r_sub: ty::Region<'tcx>,
592 r_sup: ty::Region<'tcx>)
595 let region_rels = RegionRelations::new(self.tcx,
597 &self.region_scope_tree,
598 &self.tables.free_region_map);
599 region_rels.is_subregion_of(r_sub, r_sup)
602 pub fn report(&self, err: BckError<'tcx>) {
603 // Catch and handle some particular cases.
604 match (&err.code, &err.cause) {
605 (&err_out_of_scope(&ty::ReScope(_), &ty::ReStatic, _),
606 &BorrowViolation(euv::ClosureCapture(span))) |
607 (&err_out_of_scope(&ty::ReScope(_), &ty::ReEarlyBound(..), _),
608 &BorrowViolation(euv::ClosureCapture(span))) |
609 (&err_out_of_scope(&ty::ReScope(_), &ty::ReFree(..), _),
610 &BorrowViolation(euv::ClosureCapture(span))) => {
611 return self.report_out_of_scope_escaping_closure_capture(&err, span);
616 self.report_bckerr(&err);
619 pub fn report_use_of_moved_value(&self,
621 use_kind: MovedValueUseKind,
623 the_move: &move_data::Move,
624 moved_lp: &LoanPath<'tcx>,
625 _param_env: ty::ParamEnv<'tcx>) {
626 let (verb, verb_participle) = match use_kind {
627 MovedInUse => ("use", "used"),
628 MovedInCapture => ("capture", "captured"),
631 let (_ol, _moved_lp_msg, mut err, need_note) = match the_move.kind {
632 move_data::Declared => {
633 // If this is an uninitialized variable, just emit a simple warning
635 self.cannot_act_on_uninitialized_variable(use_span,
637 &self.loan_path_to_string(lp),
639 .span_label(use_span, format!("use of possibly uninitialized `{}`",
640 self.loan_path_to_string(lp)))
645 // If moved_lp is something like `x.a`, and lp is something like `x.b`, we would
646 // normally generate a rather confusing message:
648 // error: use of moved value: `x.b`
649 // note: `x.a` moved here...
651 // What we want to do instead is get the 'common ancestor' of the two moves and
652 // use that for most of the message instead, giving is something like this:
654 // error: use of moved value: `x`
655 // note: `x` moved here (through moving `x.a`)...
657 let common = moved_lp.common(lp);
658 let has_common = common.is_some();
659 let has_fork = moved_lp.has_fork(lp);
660 let (nl, ol, moved_lp_msg) =
661 if has_fork && has_common {
662 let nl = self.loan_path_to_string(&common.unwrap());
664 let moved_lp_msg = format!(" (through moving `{}`)",
665 self.loan_path_to_string(moved_lp));
666 (nl, ol, moved_lp_msg)
668 (self.loan_path_to_string(lp),
669 self.loan_path_to_string(moved_lp),
673 let partial = moved_lp.depth() > lp.depth();
674 let msg = if !has_fork && partial { "partially " }
675 else if has_fork && !has_common { "collaterally "}
677 let mut err = self.cannot_act_on_moved_value(use_span,
682 let need_note = match lp.ty.sty {
683 ty::TypeVariants::TyClosure(id, _) => {
684 let node_id = self.tcx.hir.as_local_node_id(id).unwrap();
685 let hir_id = self.tcx.hir.node_to_hir_id(node_id);
686 if let Some((span, name)) = self.tables.closure_kind_origins().get(hir_id) {
687 err.span_note(*span, &format!(
688 "closure cannot be invoked more than once because \
689 it moves the variable `{}` out of its environment",
699 (ol, moved_lp_msg, err, need_note)
703 // Get type of value and span where it was previously
705 let node_id = self.tcx.hir.hir_to_node_id(hir::HirId {
706 owner: self.body.value.hir_id.owner,
707 local_id: the_move.id
709 let (move_span, move_note) = match the_move.kind {
710 move_data::Declared => {
714 move_data::MoveExpr |
715 move_data::MovePat => (self.tcx.hir.span(node_id), ""),
717 move_data::Captured =>
718 (match self.tcx.hir.expect_expr(node_id).node {
719 hir::ExprClosure(.., fn_decl_span, _) => fn_decl_span,
720 ref r => bug!("Captured({:?}) maps to non-closure: {:?}",
722 }, " (into closure)"),
725 // Annotate the use and the move in the span. Watch out for
726 // the case where the use and the move are the same. This
727 // means the use is in a loop.
728 err = if use_span == move_span {
731 format!("value moved{} here in previous iteration of loop",
735 err.span_label(use_span, format!("value {} here after move", verb_participle));
736 err.span_label(move_span, format!("value moved{} here", move_note));
742 "move occurs because {} has type `{}`, which does not implement the `Copy` trait",
743 if moved_lp.has_downcast() {
744 "the value".to_string()
746 format!("`{}`", self.loan_path_to_string(moved_lp))
751 // Note: we used to suggest adding a `ref binding` or calling
752 // `clone` but those suggestions have been removed because
753 // they are often not what you actually want to do, and were
754 // not considered particularly helpful.
759 pub fn report_partial_reinitialization_of_uninitialized_structure(
762 lp: &LoanPath<'tcx>) {
763 self.cannot_partially_reinit_an_uninit_struct(span,
764 &self.loan_path_to_string(lp),
769 pub fn report_reassigned_immutable_variable(&self,
773 &move_data::Assignment) {
774 let mut err = self.cannot_reassign_immutable(span,
775 &self.loan_path_to_string(lp),
778 err.span_label(span, "cannot assign twice to immutable variable");
779 if span != assign.span {
780 err.span_label(assign.span, format!("first assignment to `{}`",
781 self.loan_path_to_string(lp)));
786 pub fn struct_span_err_with_code<S: Into<MultiSpan>>(&self,
790 -> DiagnosticBuilder<'a> {
791 self.tcx.sess.struct_span_err_with_code(s, msg, code)
794 pub fn span_err_with_code<S: Into<MultiSpan>>(
800 self.tcx.sess.span_err_with_code(s, msg, code);
803 fn report_bckerr(&self, err: &BckError<'tcx>) {
804 let error_span = err.span.clone();
808 let descr = match err.cmt.note {
809 mc::NoteClosureEnv(_) | mc::NoteUpvarRef(_) => {
810 self.cmt_to_string(&err.cmt)
812 _ => match opt_loan_path_is_field(&err.cmt) {
814 format!("{} of {} binding",
815 self.cmt_to_string(&err.cmt),
816 err.cmt.mutbl.to_user_str())
821 err.cmt.mutbl.to_user_str(),
822 self.cmt_to_string(&err.cmt))
825 (Some(lp), true) => {
826 format!("{} `{}` of {} binding",
827 self.cmt_to_string(&err.cmt),
828 self.loan_path_to_string(&lp),
829 err.cmt.mutbl.to_user_str())
831 (Some(lp), false) => {
832 format!("{} {} `{}`",
833 err.cmt.mutbl.to_user_str(),
834 self.cmt_to_string(&err.cmt),
835 self.loan_path_to_string(&lp))
840 let mut db = match err.cause {
841 MutabilityViolation => {
842 let mut db = self.cannot_assign(error_span, &descr, Origin::Ast);
843 if let mc::NoteClosureEnv(upvar_id) = err.cmt.note {
844 let node_id = self.tcx.hir.hir_to_node_id(upvar_id.var_id);
845 let sp = self.tcx.hir.span(node_id);
846 let fn_closure_msg = "`Fn` closures cannot capture their enclosing \
847 environment for modifications";
848 match (self.tcx.sess.codemap().span_to_snippet(sp), &err.cmt.cat) {
849 (_, &Categorization::Upvar(mc::Upvar {
850 kind: ty::ClosureKind::Fn, ..
852 db.note(fn_closure_msg);
853 // we should point at the cause for this closure being
854 // identified as `Fn` (like in signature of method this
855 // closure was passed into)
857 (Ok(ref snippet), ref cat) => {
858 let msg = &format!("consider making `{}` mutable", snippet);
859 let suggestion = format!("mut {}", snippet);
861 if let &Categorization::Deref(ref cmt, _) = cat {
862 if let Categorization::Upvar(mc::Upvar {
863 kind: ty::ClosureKind::Fn, ..
865 db.note(fn_closure_msg);
867 db.span_suggestion(sp, msg, suggestion);
870 db.span_suggestion(sp, msg, suggestion);
874 db.span_help(sp, "consider making this binding mutable");
880 BorrowViolation(euv::ClosureCapture(_)) => {
881 self.closure_cannot_assign_to_borrowed(error_span, &descr, Origin::Ast)
883 BorrowViolation(euv::OverloadedOperator) |
884 BorrowViolation(euv::AddrOf) |
885 BorrowViolation(euv::RefBinding) |
886 BorrowViolation(euv::AutoRef) |
887 BorrowViolation(euv::AutoUnsafe) |
888 BorrowViolation(euv::ForLoop) |
889 BorrowViolation(euv::MatchDiscriminant) => {
890 self.cannot_borrow_path_as_mutable(error_span, &descr, Origin::Ast)
892 BorrowViolation(euv::ClosureInvocation) => {
894 "err_mutbl with a closure invocation");
898 self.note_and_explain_mutbl_error(&mut db, &err, &error_span);
899 self.note_immutability_blame(&mut db, err.cmt.immutability_blame());
902 err_out_of_scope(super_scope, sub_scope, cause) => {
903 let msg = match opt_loan_path(&err.cmt) {
904 None => "borrowed value".to_string(),
906 format!("`{}`", self.loan_path_to_string(&lp))
910 let mut db = self.path_does_not_live_long_enough(error_span, &msg, Origin::Ast);
911 let value_kind = match err.cmt.cat {
912 mc::Categorization::Rvalue(..) => "temporary value",
913 _ => "borrowed value",
916 let is_closure = match cause {
917 euv::ClosureCapture(s) => {
918 // The primary span starts out as the closure creation point.
919 // Change the primary span here to highlight the use of the variable
920 // in the closure, because it seems more natural. Highlight
921 // closure creation point as a secondary span.
922 match db.span.primary_span() {
924 db.span = MultiSpan::from_span(s);
925 db.span_label(primary, "capture occurs here");
926 db.span_label(s, format!("{} does not live long enough",
934 db.span_label(error_span, format!("{} does not live long enough",
940 let sub_span = self.region_end_span(sub_scope);
941 let super_span = self.region_end_span(super_scope);
943 match (sub_span, super_span) {
944 (Some(s1), Some(s2)) if s1 == s2 => {
946 let msg = match opt_loan_path(&err.cmt) {
947 None => value_kind.to_string(),
949 format!("`{}`", self.loan_path_to_string(&lp))
953 format!("{} dropped here while still borrowed", msg));
955 db.span_label(s1, format!("{} dropped before borrower", value_kind));
957 db.note("values in a scope are dropped in the opposite order \
960 (Some(s1), Some(s2)) if !is_closure => {
961 let msg = match opt_loan_path(&err.cmt) {
962 None => value_kind.to_string(),
964 format!("`{}`", self.loan_path_to_string(&lp))
967 db.span_label(s2, format!("{} dropped here while still borrowed", msg));
968 db.span_label(s1, format!("{} needs to live until here", value_kind));
973 db.span_label(s, format!("{} needs to live until here",
977 self.tcx.note_and_explain_region(
978 &self.region_scope_tree,
980 "borrowed value must be valid for ",
987 db.span_label(s, format!("{} only lives until here", value_kind));
990 self.tcx.note_and_explain_region(
991 &self.region_scope_tree,
993 "...but borrowed value is only valid for ",
1001 if let ty::ReScope(scope) = *super_scope {
1002 let node_id = scope.node_id(self.tcx, &self.region_scope_tree);
1003 match self.tcx.hir.find(node_id) {
1004 Some(hir_map::NodeStmt(_)) => {
1005 db.note("consider using a `let` binding to increase its lifetime");
1013 err_borrowed_pointer_too_short(loan_scope, ptr_scope) => {
1014 let descr = self.cmt_to_path_or_string(&err.cmt);
1015 let mut db = self.lifetime_too_short_for_reborrow(error_span, &descr, Origin::Ast);
1016 let descr = match opt_loan_path(&err.cmt) {
1018 format!("`{}`", self.loan_path_to_string(&lp))
1020 None => self.cmt_to_string(&err.cmt),
1022 self.tcx.note_and_explain_region(
1023 &self.region_scope_tree,
1025 &format!("{} would have to be valid for ",
1029 self.tcx.note_and_explain_region(
1030 &self.region_scope_tree,
1032 &format!("...but {} is only valid for ", descr),
1041 pub fn report_aliasability_violation(&self,
1043 kind: AliasableViolationKind,
1044 cause: mc::AliasableReason,
1045 cmt: mc::cmt<'tcx>) {
1046 let mut is_closure = false;
1047 let prefix = match kind {
1048 MutabilityViolation => {
1049 "cannot assign to data"
1051 BorrowViolation(euv::ClosureCapture(_)) |
1052 BorrowViolation(euv::OverloadedOperator) |
1053 BorrowViolation(euv::AddrOf) |
1054 BorrowViolation(euv::AutoRef) |
1055 BorrowViolation(euv::AutoUnsafe) |
1056 BorrowViolation(euv::RefBinding) |
1057 BorrowViolation(euv::MatchDiscriminant) => {
1058 "cannot borrow data mutably"
1061 BorrowViolation(euv::ClosureInvocation) => {
1063 "closure invocation"
1066 BorrowViolation(euv::ForLoop) => {
1072 mc::AliasableStaticMut => {
1073 // This path cannot occur. `static mut X` is not checked
1074 // for aliasability violations.
1075 span_bug!(span, "aliasability violation for static mut `{}`", prefix)
1077 mc::AliasableStatic | mc::AliasableBorrowed => {}
1079 let blame = cmt.immutability_blame();
1080 let mut err = match blame {
1081 Some(ImmutabilityBlame::ClosureEnv(id)) => {
1082 // FIXME: the distinction between these 2 messages looks wrong.
1083 let help_msg = if let BorrowViolation(euv::ClosureCapture(_)) = kind {
1084 // The aliasability violation with closure captures can
1085 // happen for nested closures, so we know the enclosing
1086 // closure incorrectly accepts an `Fn` while it needs to
1088 "consider changing this to accept closures that implement `FnMut`"
1091 "consider changing this closure to take self by mutable reference"
1093 let node_id = self.tcx.hir.local_def_id_to_node_id(id);
1094 let help_span = self.tcx.hir.span(node_id);
1095 self.cannot_act_on_capture_in_sharable_fn(span,
1097 (help_span, help_msg),
1101 self.cannot_assign_into_immutable_reference(span, prefix,
1105 self.note_immutability_blame(&mut err, blame);
1108 err.help("closures behind references must be called via `&mut`");
1113 /// Given a type, if it is an immutable reference, return a suggestion to make it mutable
1114 fn suggest_mut_for_immutable(&self, pty: &hir::Ty, is_implicit_self: bool) -> Option<String> {
1115 // Check whether the argument is an immutable reference
1116 debug!("suggest_mut_for_immutable({:?}, {:?})", pty, is_implicit_self);
1117 if let hir::TyRptr(lifetime, hir::MutTy {
1118 mutbl: hir::Mutability::MutImmutable,
1121 // Account for existing lifetimes when generating the message
1122 let pointee_snippet = match self.tcx.sess.codemap().span_to_snippet(ty.span) {
1123 Ok(snippet) => snippet,
1127 let lifetime_snippet = if !lifetime.is_elided() {
1128 format!("{} ", match self.tcx.sess.codemap().span_to_snippet(lifetime.span) {
1129 Ok(lifetime_snippet) => lifetime_snippet,
1135 Some(format!("use `&{}mut {}` here to make mutable",
1137 if is_implicit_self { "self" } else { &*pointee_snippet }))
1143 fn local_binding_mode(&self, node_id: ast::NodeId) -> ty::BindingMode {
1144 let pat = match self.tcx.hir.get(node_id) {
1145 hir_map::Node::NodeBinding(pat) => pat,
1146 node => bug!("bad node for local: {:?}", node)
1150 hir::PatKind::Binding(..) => {
1152 .pat_binding_modes()
1154 .expect("missing binding mode")
1156 _ => bug!("local is not a binding: {:?}", pat)
1160 fn local_ty(&self, node_id: ast::NodeId) -> (Option<&hir::Ty>, bool) {
1161 let parent = self.tcx.hir.get_parent_node(node_id);
1162 let parent_node = self.tcx.hir.get(parent);
1164 // The parent node is like a fn
1165 if let Some(fn_like) = FnLikeNode::from_node(parent_node) {
1166 // `nid`'s parent's `Body`
1167 let fn_body = self.tcx.hir.body(fn_like.body());
1168 // Get the position of `node_id` in the arguments list
1169 let arg_pos = fn_body.arguments.iter().position(|arg| arg.pat.id == node_id);
1170 if let Some(i) = arg_pos {
1171 // The argument's `Ty`
1172 (Some(&fn_like.decl().inputs[i]),
1173 i == 0 && fn_like.decl().has_implicit_self)
1182 fn note_immutability_blame(&self,
1183 db: &mut DiagnosticBuilder,
1184 blame: Option<ImmutabilityBlame>) {
1187 Some(ImmutabilityBlame::ClosureEnv(_)) => {}
1188 Some(ImmutabilityBlame::ImmLocal(node_id)) => {
1189 let let_span = self.tcx.hir.span(node_id);
1190 if let ty::BindByValue(..) = self.local_binding_mode(node_id) {
1191 if let Ok(snippet) = self.tcx.sess.codemap().span_to_snippet(let_span) {
1192 let (_, is_implicit_self) = self.local_ty(node_id);
1193 if is_implicit_self && snippet != "self" {
1194 // avoid suggesting `mut &self`.
1199 format!("consider changing this to `mut {}`", snippet)
1204 Some(ImmutabilityBlame::LocalDeref(node_id)) => {
1205 let let_span = self.tcx.hir.span(node_id);
1206 match self.local_binding_mode(node_id) {
1207 ty::BindByReference(..) => {
1208 let snippet = self.tcx.sess.codemap().span_to_snippet(let_span);
1209 if let Ok(snippet) = snippet {
1212 format!("consider changing this to `{}`",
1213 snippet.replace("ref ", "ref mut "))
1217 ty::BindByValue(..) => {
1218 if let (Some(local_ty), is_implicit_self) = self.local_ty(node_id) {
1220 self.suggest_mut_for_immutable(local_ty, is_implicit_self) {
1221 db.span_label(local_ty.span, msg);
1227 Some(ImmutabilityBlame::AdtFieldDeref(_, field)) => {
1228 let node_id = match self.tcx.hir.as_local_node_id(field.did) {
1229 Some(node_id) => node_id,
1233 if let hir_map::Node::NodeField(ref field) = self.tcx.hir.get(node_id) {
1234 if let Some(msg) = self.suggest_mut_for_immutable(&field.ty, false) {
1235 db.span_label(field.ty.span, msg);
1242 fn report_out_of_scope_escaping_closure_capture(&self,
1243 err: &BckError<'tcx>,
1246 let cmt_path_or_string = self.cmt_to_path_or_string(&err.cmt);
1249 match self.tcx.sess.codemap().span_to_snippet(err.span) {
1250 Ok(string) => format!("move {}", string),
1251 Err(_) => format!("move |<args>| <body>")
1254 self.cannot_capture_in_long_lived_closure(err.span,
1255 &cmt_path_or_string,
1258 .span_suggestion(err.span,
1259 &format!("to force the closure to take ownership of {} \
1260 (and any other referenced variables), \
1261 use the `move` keyword",
1262 cmt_path_or_string),
1267 fn region_end_span(&self, region: ty::Region<'tcx>) -> Option<Span> {
1269 ty::ReScope(scope) => {
1270 Some(self.tcx.sess.codemap().end_point(
1271 scope.span(self.tcx, &self.region_scope_tree)))
1277 fn note_and_explain_mutbl_error(&self, db: &mut DiagnosticBuilder, err: &BckError<'tcx>,
1278 error_span: &Span) {
1279 match err.cmt.note {
1280 mc::NoteClosureEnv(upvar_id) | mc::NoteUpvarRef(upvar_id) => {
1281 // If this is an `Fn` closure, it simply can't mutate upvars.
1282 // If it's an `FnMut` closure, the original variable was declared immutable.
1283 // We need to determine which is the case here.
1284 let kind = match err.cmt.upvar().unwrap().cat {
1285 Categorization::Upvar(mc::Upvar { kind, .. }) => kind,
1288 if kind == ty::ClosureKind::Fn {
1289 let closure_node_id =
1290 self.tcx.hir.local_def_id_to_node_id(upvar_id.closure_expr_id);
1291 db.span_help(self.tcx.hir.span(closure_node_id),
1292 "consider changing this closure to take \
1293 self by mutable reference");
1297 if let Categorization::Deref(..) = err.cmt.cat {
1298 db.span_label(*error_span, "cannot borrow as mutable");
1299 } else if let Categorization::Local(local_id) = err.cmt.cat {
1300 let span = self.tcx.hir.span(local_id);
1301 if let Ok(snippet) = self.tcx.sess.codemap().span_to_snippet(span) {
1302 if snippet.starts_with("ref mut ") || snippet.starts_with("&mut ") {
1303 db.span_label(*error_span, "cannot reborrow mutably");
1304 db.span_label(*error_span, "try removing `&mut` here");
1306 db.span_label(*error_span, "cannot borrow mutably");
1309 db.span_label(*error_span, "cannot borrow mutably");
1311 } else if let Categorization::Interior(ref cmt, _) = err.cmt.cat {
1312 if let mc::MutabilityCategory::McImmutable = cmt.mutbl {
1313 db.span_label(*error_span,
1314 "cannot mutably borrow field of immutable binding");
1320 pub fn append_loan_path_to_string(&self,
1321 loan_path: &LoanPath<'tcx>,
1323 match loan_path.kind {
1324 LpUpvar(ty::UpvarId { var_id: id, closure_expr_id: _ }) => {
1325 out.push_str(&self.tcx.hir.name(self.tcx.hir.hir_to_node_id(id)).as_str());
1328 out.push_str(&self.tcx.hir.name(id).as_str());
1331 LpDowncast(ref lp_base, variant_def_id) => {
1333 self.append_loan_path_to_string(&lp_base, out);
1334 out.push_str(DOWNCAST_PRINTED_OPERATOR);
1335 out.push_str(&self.tcx.item_path_str(variant_def_id));
1339 LpExtend(ref lp_base, _, LpInterior(_, InteriorField(fname))) => {
1340 self.append_autoderefd_loan_path_to_string(&lp_base, out);
1342 mc::NamedField(fname) => {
1344 out.push_str(&fname.as_str());
1346 mc::PositionalField(idx) => {
1348 out.push_str(&idx.to_string());
1353 LpExtend(ref lp_base, _, LpInterior(_, InteriorElement)) => {
1354 self.append_autoderefd_loan_path_to_string(&lp_base, out);
1355 out.push_str("[..]");
1358 LpExtend(ref lp_base, _, LpDeref(_)) => {
1360 self.append_loan_path_to_string(&lp_base, out);
1365 pub fn append_autoderefd_loan_path_to_string(&self,
1366 loan_path: &LoanPath<'tcx>,
1368 match loan_path.kind {
1369 LpExtend(ref lp_base, _, LpDeref(_)) => {
1370 // For a path like `(*x).f` or `(*x)[3]`, autoderef
1371 // rules would normally allow users to omit the `*x`.
1372 // So just serialize such paths to `x.f` or x[3]` respectively.
1373 self.append_autoderefd_loan_path_to_string(&lp_base, out)
1376 LpDowncast(ref lp_base, variant_def_id) => {
1378 self.append_autoderefd_loan_path_to_string(&lp_base, out);
1379 out.push_str(DOWNCAST_PRINTED_OPERATOR);
1380 out.push_str(&self.tcx.item_path_str(variant_def_id));
1384 LpVar(..) | LpUpvar(..) | LpExtend(.., LpInterior(..)) => {
1385 self.append_loan_path_to_string(loan_path, out)
1390 pub fn loan_path_to_string(&self, loan_path: &LoanPath<'tcx>) -> String {
1391 let mut result = String::new();
1392 self.append_loan_path_to_string(loan_path, &mut result);
1396 pub fn cmt_to_string(&self, cmt: &mc::cmt_<'tcx>) -> String {
1397 cmt.descriptive_string(self.tcx)
1400 pub fn cmt_to_path_or_string(&self, cmt: &mc::cmt<'tcx>) -> String {
1401 match opt_loan_path(cmt) {
1402 Some(lp) => format!("`{}`", self.loan_path_to_string(&lp)),
1403 None => self.cmt_to_string(cmt),
1408 impl BitwiseOperator for LoanDataFlowOperator {
1410 fn join(&self, succ: usize, pred: usize) -> usize {
1411 succ | pred // loans from both preds are in scope
1415 impl DataFlowOperator for LoanDataFlowOperator {
1417 fn initial_value(&self) -> bool {
1418 false // no loans in scope by default
1422 impl<'tcx> fmt::Debug for InteriorKind {
1423 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1425 InteriorField(mc::NamedField(fld)) => write!(f, "{}", fld),
1426 InteriorField(mc::PositionalField(i)) => write!(f, "#{}", i),
1427 InteriorElement => write!(f, "[]"),
1432 impl<'tcx> fmt::Debug for Loan<'tcx> {
1433 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1434 write!(f, "Loan_{}({:?}, {:?}, {:?}-{:?}, {:?})",
1440 self.restricted_paths)
1444 impl<'tcx> fmt::Debug for LoanPath<'tcx> {
1445 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1448 write!(f, "$({})", ty::tls::with(|tcx| tcx.hir.node_to_string(id)))
1451 LpUpvar(ty::UpvarId{ var_id, closure_expr_id }) => {
1452 let s = ty::tls::with(|tcx| {
1453 let var_node_id = tcx.hir.hir_to_node_id(var_id);
1454 tcx.hir.node_to_string(var_node_id)
1456 write!(f, "$({} captured by id={:?})", s, closure_expr_id)
1459 LpDowncast(ref lp, variant_def_id) => {
1460 let variant_str = if variant_def_id.is_local() {
1461 ty::tls::with(|tcx| tcx.item_path_str(variant_def_id))
1463 format!("{:?}", variant_def_id)
1465 write!(f, "({:?}{}{})", lp, DOWNCAST_PRINTED_OPERATOR, variant_str)
1468 LpExtend(ref lp, _, LpDeref(_)) => {
1469 write!(f, "{:?}.*", lp)
1472 LpExtend(ref lp, _, LpInterior(_, ref interior)) => {
1473 write!(f, "{:?}.{:?}", lp, interior)
1479 impl<'tcx> fmt::Display for LoanPath<'tcx> {
1480 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1483 write!(f, "$({})", ty::tls::with(|tcx| tcx.hir.node_to_user_string(id)))
1486 LpUpvar(ty::UpvarId{ var_id, closure_expr_id: _ }) => {
1487 let s = ty::tls::with(|tcx| {
1488 let var_node_id = tcx.hir.hir_to_node_id(var_id);
1489 tcx.hir.node_to_string(var_node_id)
1491 write!(f, "$({} captured by closure)", s)
1494 LpDowncast(ref lp, variant_def_id) => {
1495 let variant_str = if variant_def_id.is_local() {
1496 ty::tls::with(|tcx| tcx.item_path_str(variant_def_id))
1498 format!("{:?}", variant_def_id)
1500 write!(f, "({}{}{})", lp, DOWNCAST_PRINTED_OPERATOR, variant_str)
1503 LpExtend(ref lp, _, LpDeref(_)) => {
1504 write!(f, "{}.*", lp)
1507 LpExtend(ref lp, _, LpInterior(_, ref interior)) => {
1508 write!(f, "{}.{:?}", lp, interior)