src/librustc_borrowck/borrowck/mod.rs

   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.
   4 //
   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.
  10
  11 //! See The Book chapter on the borrow checker for more details.
  12
  13 #![allow(non_camel_case_types)]
  14
  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::*;
  20
  21 pub use self::mir::elaborate_drops::ElaborateDrops;
  22
  23 use self::InteriorKind::*;
  24
  25 use rustc::dep_graph::DepNode;
  26 use rustc::hir::map as hir_map;
  27 use rustc::hir::map::blocks::FnLikeNode;
  28 use rustc::cfg;
  29 use rustc::middle::dataflow::DataFlowContext;
  30 use rustc::middle::dataflow::BitwiseOperator;
  31 use rustc::middle::dataflow::DataFlowOperator;
  32 use rustc::middle::dataflow::KillFrom;
  33 use rustc::hir::def_id::DefId;
  34 use rustc::middle::expr_use_visitor as euv;
  35 use rustc::middle::mem_categorization as mc;
  36 use rustc::middle::mem_categorization::Categorization;
  37 use rustc::middle::mem_categorization::ImmutabilityBlame;
  38 use rustc::middle::region;
  39 use rustc::ty::{self, TyCtxt};
  40
  41 use std::fmt;
  42 use std::rc::Rc;
  43 use std::hash::{Hash, Hasher};
  44 use syntax::ast;
  45 use syntax_pos::{MultiSpan, Span};
  46 use errors::DiagnosticBuilder;
  47
  48 use rustc::hir;
  49 use rustc::hir::intravisit::{self, Visitor};
  50
  51 pub mod check_loans;
  52
  53 pub mod gather_loans;
  54
  55 pub mod move_data;
  56
  57 mod mir;
  58
  59 #[derive(Clone, Copy)]
  60 pub struct LoanDataFlowOperator;
  61
  62 pub type LoanDataFlow<'a, 'tcx> = DataFlowContext<'a, 'tcx, LoanDataFlowOperator>;
  63
  64 pub fn check_crate<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>) {
  65     tcx.dep_graph.with_task(DepNode::BorrowCheckKrate, tcx, (), check_crate_task);
  66
  67     fn check_crate_task<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, (): ()) {
  68         tcx.visit_all_bodies_in_krate(|body_owner_def_id, body_id| {
  69             tcx.dep_graph.with_task(DepNode::BorrowCheck(body_owner_def_id),
  70                                     tcx,
  71                                     body_id,
  72                                     borrowck_fn);
  73         });
  74     }
  75 }
  76
  77 /// Collection of conclusions determined via borrow checker analyses.
  78 pub struct AnalysisData<'a, 'tcx: 'a> {
  79     pub all_loans: Vec<Loan<'tcx>>,
  80     pub loans: DataFlowContext<'a, 'tcx, LoanDataFlowOperator>,
  81     pub move_data: move_data::FlowedMoveData<'a, 'tcx>,
  82 }
  83
  84 fn borrowck_fn<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, body_id: hir::BodyId) {
  85     debug!("borrowck_fn(body_id={:?})", body_id);
  86
  87     let owner_id = tcx.hir.body_owner(body_id);
  88     let owner_def_id = tcx.hir.local_def_id(owner_id);
  89     let attributes = tcx.get_attrs(owner_def_id);
  90     let tables = tcx.item_tables(owner_def_id);
  91
  92     let mut bccx = &mut BorrowckCtxt {
  93         tcx: tcx,
  94         tables: tables,
  95     };
  96
  97     let body = bccx.tcx.hir.body(body_id);
  98
  99     if bccx.tcx.has_attr(owner_def_id, "rustc_mir_borrowck") {
 100         mir::borrowck_mir(bccx, owner_id, &attributes);
 101     }
 102
 103     let cfg = cfg::CFG::new(bccx.tcx, &body);
 104     let AnalysisData { all_loans,
 105                        loans: loan_dfcx,
 106                        move_data: flowed_moves } =
 107         build_borrowck_dataflow_data(bccx, &cfg, body_id);
 108
 109     move_data::fragments::instrument_move_fragments(&flowed_moves.move_data,
 110                                                     bccx.tcx,
 111                                                     owner_id);
 112     move_data::fragments::build_unfragmented_map(bccx,
 113                                                  &flowed_moves.move_data,
 114                                                  owner_id);
 115
 116     check_loans::check_loans(bccx, &loan_dfcx, &flowed_moves, &all_loans, body);
 117 }
 118
 119 fn build_borrowck_dataflow_data<'a, 'tcx>(this: &mut BorrowckCtxt<'a, 'tcx>,
 120                                           cfg: &cfg::CFG,
 121                                           body_id: hir::BodyId)
 122                                           -> AnalysisData<'a, 'tcx>
 123 {
 124     // Check the body of fn items.
 125     let tcx = this.tcx;
 126     let body = tcx.hir.body(body_id);
 127     let id_range = {
 128         let mut visitor = intravisit::IdRangeComputingVisitor::new(&tcx.hir);
 129         visitor.visit_body(body);
 130         visitor.result()
 131     };
 132     let (all_loans, move_data) =
 133         gather_loans::gather_loans_in_fn(this, body_id);
 134
 135     let mut loan_dfcx =
 136         DataFlowContext::new(this.tcx,
 137                              "borrowck",
 138                              Some(body),
 139                              cfg,
 140                              LoanDataFlowOperator,
 141                              id_range,
 142                              all_loans.len());
 143     for (loan_idx, loan) in all_loans.iter().enumerate() {
 144         loan_dfcx.add_gen(loan.gen_scope.node_id(&tcx.region_maps), loan_idx);
 145         loan_dfcx.add_kill(KillFrom::ScopeEnd,
 146                            loan.kill_scope.node_id(&tcx.region_maps), loan_idx);
 147     }
 148     loan_dfcx.add_kills_from_flow_exits(cfg);
 149     loan_dfcx.propagate(cfg, body);
 150
 151     let flowed_moves = move_data::FlowedMoveData::new(move_data,
 152                                                       this.tcx,
 153                                                       cfg,
 154                                                       id_range,
 155                                                       body);
 156
 157     AnalysisData { all_loans: all_loans,
 158                    loans: loan_dfcx,
 159                    move_data:flowed_moves }
 160 }
 161
 162 /// Accessor for introspective clients inspecting `AnalysisData` and
 163 /// the `BorrowckCtxt` itself , e.g. the flowgraph visualizer.
 164 pub fn build_borrowck_dataflow_data_for_fn<'a, 'tcx>(
 165     tcx: TyCtxt<'a, 'tcx, 'tcx>,
 166     body_id: hir::BodyId,
 167     cfg: &cfg::CFG)
 168     -> (BorrowckCtxt<'a, 'tcx>, AnalysisData<'a, 'tcx>)
 169 {
 170     let owner_id = tcx.hir.body_owner(body_id);
 171     let owner_def_id = tcx.hir.local_def_id(owner_id);
 172     let tables = tcx.item_tables(owner_def_id);
 173
 174     let mut bccx = BorrowckCtxt {
 175         tcx: tcx,
 176         tables: tables,
 177     };
 178
 179     let dataflow_data = build_borrowck_dataflow_data(&mut bccx, cfg, body_id);
 180     (bccx, dataflow_data)
 181 }
 182
 183 // ----------------------------------------------------------------------
 184 // Type definitions
 185
 186 pub struct BorrowckCtxt<'a, 'tcx: 'a> {
 187     tcx: TyCtxt<'a, 'tcx, 'tcx>,
 188
 189     // tables for the current thing we are checking; set to
 190     // Some in `borrowck_fn` and cleared later
 191     tables: &'a ty::TypeckTables<'tcx>,
 192 }
 193
 194 ///////////////////////////////////////////////////////////////////////////
 195 // Loans and loan paths
 196
 197 /// Record of a loan that was issued.
 198 pub struct Loan<'tcx> {
 199     index: usize,
 200     loan_path: Rc<LoanPath<'tcx>>,
 201     kind: ty::BorrowKind,
 202     restricted_paths: Vec<Rc<LoanPath<'tcx>>>,
 203
 204     /// gen_scope indicates where loan is introduced. Typically the
 205     /// loan is introduced at the point of the borrow, but in some
 206     /// cases, notably method arguments, the loan may be introduced
 207     /// only later, once it comes into scope.  See also
 208     /// `GatherLoanCtxt::compute_gen_scope`.
 209     gen_scope: region::CodeExtent,
 210
 211     /// kill_scope indicates when the loan goes out of scope.  This is
 212     /// either when the lifetime expires or when the local variable
 213     /// which roots the loan-path goes out of scope, whichever happens
 214     /// faster. See also `GatherLoanCtxt::compute_kill_scope`.
 215     kill_scope: region::CodeExtent,
 216     span: Span,
 217     cause: euv::LoanCause,
 218 }
 219
 220 impl<'tcx> Loan<'tcx> {
 221     pub fn loan_path(&self) -> Rc<LoanPath<'tcx>> {
 222         self.loan_path.clone()
 223     }
 224 }
 225
 226 #[derive(Eq)]
 227 pub struct LoanPath<'tcx> {
 228     kind: LoanPathKind<'tcx>,
 229     ty: ty::Ty<'tcx>,
 230 }
 231
 232 impl<'tcx> PartialEq for LoanPath<'tcx> {
 233     fn eq(&self, that: &LoanPath<'tcx>) -> bool {
 234         self.kind == that.kind
 235     }
 236 }
 237
 238 impl<'tcx> Hash for LoanPath<'tcx> {
 239     fn hash<H: Hasher>(&self, state: &mut H) {
 240         self.kind.hash(state);
 241     }
 242 }
 243
 244 #[derive(PartialEq, Eq, Hash, Debug)]
 245 pub enum LoanPathKind<'tcx> {
 246     LpVar(ast::NodeId),                         // `x` in README.md
 247     LpUpvar(ty::UpvarId),                       // `x` captured by-value into closure
 248     LpDowncast(Rc<LoanPath<'tcx>>, DefId), // `x` downcast to particular enum variant
 249     LpExtend(Rc<LoanPath<'tcx>>, mc::MutabilityCategory, LoanPathElem<'tcx>)
 250 }
 251
 252 impl<'tcx> LoanPath<'tcx> {
 253     fn new(kind: LoanPathKind<'tcx>, ty: ty::Ty<'tcx>) -> LoanPath<'tcx> {
 254         LoanPath { kind: kind, ty: ty }
 255     }
 256
 257     fn to_type(&self) -> ty::Ty<'tcx> { self.ty }
 258 }
 259
 260 // FIXME (pnkfelix): See discussion here
 261 // https://github.com/pnkfelix/rust/commit/
 262 //     b2b39e8700e37ad32b486b9a8409b50a8a53aa51#commitcomment-7892003
 263 const DOWNCAST_PRINTED_OPERATOR: &'static str = " as ";
 264
 265 // A local, "cleaned" version of `mc::InteriorKind` that drops
 266 // information that is not relevant to loan-path analysis. (In
 267 // particular, the distinction between how precisely an array-element
 268 // is tracked is irrelevant here.)
 269 #[derive(Clone, Copy, PartialEq, Eq, Hash)]
 270 pub enum InteriorKind {
 271     InteriorField(mc::FieldName),
 272     InteriorElement(mc::ElementKind),
 273 }
 274
 275 trait ToInteriorKind { fn cleaned(self) -> InteriorKind; }
 276 impl ToInteriorKind for mc::InteriorKind {
 277     fn cleaned(self) -> InteriorKind {
 278         match self {
 279             mc::InteriorField(name) => InteriorField(name),
 280             mc::InteriorElement(_, elem_kind) => InteriorElement(elem_kind),
 281         }
 282     }
 283 }
 284
 285 // This can be:
 286 // - a pointer dereference (`*LV` in README.md)
 287 // - a field reference, with an optional definition of the containing
 288 //   enum variant (`LV.f` in README.md)
 289 // `DefId` is present when the field is part of struct that is in
 290 // a variant of an enum. For instance in:
 291 // `enum E { X { foo: u32 }, Y { foo: u32 }}`
 292 // each `foo` is qualified by the definitition id of the variant (`X` or `Y`).
 293 #[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
 294 pub enum LoanPathElem<'tcx> {
 295     LpDeref(mc::PointerKind<'tcx>),
 296     LpInterior(Option<DefId>, InteriorKind),
 297 }
 298
 299 pub fn closure_to_block(closure_id: ast::NodeId,
 300                         tcx: TyCtxt) -> ast::NodeId {
 301     match tcx.hir.get(closure_id) {
 302         hir_map::NodeExpr(expr) => match expr.node {
 303             hir::ExprClosure(.., body_id, _) => {
 304                 body_id.node_id
 305             }
 306             _ => {
 307                 bug!("encountered non-closure id: {}", closure_id)
 308             }
 309         },
 310         _ => bug!("encountered non-expr id: {}", closure_id)
 311     }
 312 }
 313
 314 impl<'a, 'tcx> LoanPath<'tcx> {
 315     pub fn kill_scope(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>) -> region::CodeExtent {
 316         match self.kind {
 317             LpVar(local_id) => tcx.region_maps.var_scope(local_id),
 318             LpUpvar(upvar_id) => {
 319                 let block_id = closure_to_block(upvar_id.closure_expr_id, tcx);
 320                 tcx.region_maps.node_extent(block_id)
 321             }
 322             LpDowncast(ref base, _) |
 323             LpExtend(ref base, ..) => base.kill_scope(tcx),
 324         }
 325     }
 326
 327     fn has_fork(&self, other: &LoanPath<'tcx>) -> bool {
 328         match (&self.kind, &other.kind) {
 329             (&LpExtend(ref base, _, LpInterior(opt_variant_id, id)),
 330              &LpExtend(ref base2, _, LpInterior(opt_variant_id2, id2))) =>
 331                 if id == id2 && opt_variant_id == opt_variant_id2 {
 332                     base.has_fork(&base2)
 333                 } else {
 334                     true
 335                 },
 336             (&LpExtend(ref base, _, LpDeref(_)), _) => base.has_fork(other),
 337             (_, &LpExtend(ref base, _, LpDeref(_))) => self.has_fork(&base),
 338             _ => false,
 339         }
 340     }
 341
 342     fn depth(&self) -> usize {
 343         match self.kind {
 344             LpExtend(ref base, _, LpDeref(_)) => base.depth(),
 345             LpExtend(ref base, _, LpInterior(..)) => base.depth() + 1,
 346             _ => 0,
 347         }
 348     }
 349
 350     fn common(&self, other: &LoanPath<'tcx>) -> Option<LoanPath<'tcx>> {
 351         match (&self.kind, &other.kind) {
 352             (&LpExtend(ref base, a, LpInterior(opt_variant_id, id)),
 353              &LpExtend(ref base2, _, LpInterior(opt_variant_id2, id2))) => {
 354                 if id == id2 && opt_variant_id == opt_variant_id2 {
 355                     base.common(&base2).map(|x| {
 356                         let xd = x.depth();
 357                         if base.depth() == xd && base2.depth() == xd {
 358                             LoanPath {
 359                                 kind: LpExtend(Rc::new(x), a, LpInterior(opt_variant_id, id)),
 360                                 ty: self.ty,
 361                             }
 362                         } else {
 363                             x
 364                         }
 365                     })
 366                 } else {
 367                     base.common(&base2)
 368                 }
 369             }
 370             (&LpExtend(ref base, _, LpDeref(_)), _) => base.common(other),
 371             (_, &LpExtend(ref other, _, LpDeref(_))) => self.common(&other),
 372             (&LpVar(id), &LpVar(id2)) => {
 373                 if id == id2 {
 374                     Some(LoanPath { kind: LpVar(id), ty: self.ty })
 375                 } else {
 376                     None
 377                 }
 378             }
 379             (&LpUpvar(id), &LpUpvar(id2)) => {
 380                 if id == id2 {
 381                     Some(LoanPath { kind: LpUpvar(id), ty: self.ty })
 382                 } else {
 383                     None
 384                 }
 385             }
 386             _ => None,
 387         }
 388     }
 389 }
 390
 391 pub fn opt_loan_path<'tcx>(cmt: &mc::cmt<'tcx>) -> Option<Rc<LoanPath<'tcx>>> {
 392     //! Computes the `LoanPath` (if any) for a `cmt`.
 393     //! Note that this logic is somewhat duplicated in
 394     //! the method `compute()` found in `gather_loans::restrictions`,
 395     //! which allows it to share common loan path pieces as it
 396     //! traverses the CMT.
 397
 398     let new_lp = |v: LoanPathKind<'tcx>| Rc::new(LoanPath::new(v, cmt.ty));
 399
 400     match cmt.cat {
 401         Categorization::Rvalue(..) |
 402         Categorization::StaticItem => {
 403             None
 404         }
 405
 406         Categorization::Local(id) => {
 407             Some(new_lp(LpVar(id)))
 408         }
 409
 410         Categorization::Upvar(mc::Upvar { id, .. }) => {
 411             Some(new_lp(LpUpvar(id)))
 412         }
 413
 414         Categorization::Deref(ref cmt_base, _, pk) => {
 415             opt_loan_path(cmt_base).map(|lp| {
 416                 new_lp(LpExtend(lp, cmt.mutbl, LpDeref(pk)))
 417             })
 418         }
 419
 420         Categorization::Interior(ref cmt_base, ik) => {
 421             opt_loan_path(cmt_base).map(|lp| {
 422                 let opt_variant_id = match cmt_base.cat {
 423                     Categorization::Downcast(_, did) =>  Some(did),
 424                     _ => None
 425                 };
 426                 new_lp(LpExtend(lp, cmt.mutbl, LpInterior(opt_variant_id, ik.cleaned())))
 427             })
 428         }
 429
 430         Categorization::Downcast(ref cmt_base, variant_def_id) =>
 431             opt_loan_path(cmt_base)
 432             .map(|lp| {
 433                 new_lp(LpDowncast(lp, variant_def_id))
 434             }),
 435
 436     }
 437 }
 438
 439 ///////////////////////////////////////////////////////////////////////////
 440 // Errors
 441
 442 // Errors that can occur
 443 #[derive(Debug, PartialEq)]
 444 pub enum bckerr_code<'tcx> {
 445     err_mutbl,
 446     /// superscope, subscope, loan cause
 447     err_out_of_scope(&'tcx ty::Region, &'tcx ty::Region, euv::LoanCause),
 448     err_borrowed_pointer_too_short(&'tcx ty::Region, &'tcx ty::Region), // loan, ptr
 449 }
 450
 451 // Combination of an error code and the categorization of the expression
 452 // that caused it
 453 #[derive(Debug, PartialEq)]
 454 pub struct BckError<'tcx> {
 455     span: Span,
 456     cause: AliasableViolationKind,
 457     cmt: mc::cmt<'tcx>,
 458     code: bckerr_code<'tcx>
 459 }
 460
 461 #[derive(Copy, Clone, Debug, PartialEq)]
 462 pub enum AliasableViolationKind {
 463     MutabilityViolation,
 464     BorrowViolation(euv::LoanCause)
 465 }
 466
 467 #[derive(Copy, Clone, Debug)]
 468 pub enum MovedValueUseKind {
 469     MovedInUse,
 470     MovedInCapture,
 471 }
 472
 473 ///////////////////////////////////////////////////////////////////////////
 474 // Misc
 475
 476 impl<'a, 'tcx> BorrowckCtxt<'a, 'tcx> {
 477     pub fn is_subregion_of(&self,
 478                            r_sub: &'tcx ty::Region,
 479                            r_sup: &'tcx ty::Region)
 480                            -> bool
 481     {
 482         self.tables.free_region_map.is_subregion_of(self.tcx, r_sub, r_sup)
 483     }
 484
 485     pub fn report(&self, err: BckError<'tcx>) {
 486         // Catch and handle some particular cases.
 487         match (&err.code, &err.cause) {
 488             (&err_out_of_scope(&ty::ReScope(_), &ty::ReStatic, _),
 489              &BorrowViolation(euv::ClosureCapture(span))) |
 490             (&err_out_of_scope(&ty::ReScope(_), &ty::ReFree(..), _),
 491              &BorrowViolation(euv::ClosureCapture(span))) => {
 492                 return self.report_out_of_scope_escaping_closure_capture(&err, span);
 493             }
 494             _ => { }
 495         }
 496
 497         let mut db = self.bckerr_to_diag(&err);
 498         self.note_and_explain_bckerr(&mut db, err);
 499         db.emit();
 500     }
 501
 502     pub fn report_use_of_moved_value(&self,
 503                                      use_span: Span,
 504                                      use_kind: MovedValueUseKind,
 505                                      lp: &LoanPath<'tcx>,
 506                                      the_move: &move_data::Move,
 507                                      moved_lp: &LoanPath<'tcx>,
 508                                      _param_env: &ty::ParameterEnvironment<'tcx>) {
 509         let (verb, verb_participle) = match use_kind {
 510             MovedInUse => ("use", "used"),
 511             MovedInCapture => ("capture", "captured"),
 512         };
 513
 514         let (_ol, _moved_lp_msg, mut err) = match the_move.kind {
 515             move_data::Declared => {
 516                 // If this is an uninitialized variable, just emit a simple warning
 517                 // and return.
 518                 struct_span_err!(
 519                     self.tcx.sess, use_span, E0381,
 520                     "{} of possibly uninitialized variable: `{}`",
 521                     verb,
 522                     self.loan_path_to_string(lp))
 523                 .span_label(use_span, &format!("use of possibly uninitialized `{}`",
 524                     self.loan_path_to_string(lp)))
 525                 .emit();
 526                 return;
 527             }
 528             _ => {
 529                 // If moved_lp is something like `x.a`, and lp is something like `x.b`, we would
 530                 // normally generate a rather confusing message:
 531                 //
 532                 //     error: use of moved value: `x.b`
 533                 //     note: `x.a` moved here...
 534                 //
 535                 // What we want to do instead is get the 'common ancestor' of the two moves and
 536                 // use that for most of the message instead, giving is something like this:
 537                 //
 538                 //     error: use of moved value: `x`
 539                 //     note: `x` moved here (through moving `x.a`)...
 540
 541                 let common = moved_lp.common(lp);
 542                 let has_common = common.is_some();
 543                 let has_fork = moved_lp.has_fork(lp);
 544                 let (nl, ol, moved_lp_msg) =
 545                     if has_fork && has_common {
 546                         let nl = self.loan_path_to_string(&common.unwrap());
 547                         let ol = nl.clone();
 548                         let moved_lp_msg = format!(" (through moving `{}`)",
 549                                                    self.loan_path_to_string(moved_lp));
 550                         (nl, ol, moved_lp_msg)
 551                     } else {
 552                         (self.loan_path_to_string(lp),
 553                          self.loan_path_to_string(moved_lp),
 554                          String::new())
 555                     };
 556
 557                 let partial = moved_lp.depth() > lp.depth();
 558                 let msg = if !has_fork && partial { "partially " }
 559                           else if has_fork && !has_common { "collaterally "}
 560                           else { "" };
 561                 let err = struct_span_err!(
 562                     self.tcx.sess, use_span, E0382,
 563                     "{} of {}moved value: `{}`",
 564                     verb, msg, nl);
 565                 (ol, moved_lp_msg, err)}
 566         };
 567
 568         // Get type of value and span where it was previously
 569         // moved.
 570         let (move_span, move_note) = match the_move.kind {
 571             move_data::Declared => {
 572                 unreachable!();
 573             }
 574
 575             move_data::MoveExpr |
 576             move_data::MovePat =>
 577                 (self.tcx.hir.span(the_move.id), ""),
 578
 579             move_data::Captured =>
 580                 (match self.tcx.hir.expect_expr(the_move.id).node {
 581                     hir::ExprClosure(.., fn_decl_span) => fn_decl_span,
 582                     ref r => bug!("Captured({}) maps to non-closure: {:?}",
 583                                   the_move.id, r),
 584                 }, " (into closure)"),
 585         };
 586
 587         // Annotate the use and the move in the span. Watch out for
 588         // the case where the use and the move are the same. This
 589         // means the use is in a loop.
 590         err = if use_span == move_span {
 591             err.span_label(
 592                 use_span,
 593                 &format!("value moved{} here in previous iteration of loop",
 594                          move_note));
 595             err
 596         } else {
 597             err.span_label(use_span, &format!("value {} here after move", verb_participle))
 598                .span_label(move_span, &format!("value moved{} here", move_note));
 599             err
 600         };
 601
 602         err.note(&format!("move occurs because `{}` has type `{}`, \
 603                            which does not implement the `Copy` trait",
 604                           self.loan_path_to_string(moved_lp),
 605                           moved_lp.ty));
 606
 607         // Note: we used to suggest adding a `ref binding` or calling
 608         // `clone` but those suggestions have been removed because
 609         // they are often not what you actually want to do, and were
 610         // not considered particularly helpful.
 611
 612         err.emit();
 613     }
 614
 615     pub fn report_partial_reinitialization_of_uninitialized_structure(
 616             &self,
 617             span: Span,
 618             lp: &LoanPath<'tcx>) {
 619         span_err!(
 620             self.tcx.sess, span, E0383,
 621             "partial reinitialization of uninitialized structure `{}`",
 622             self.loan_path_to_string(lp));
 623     }
 624
 625     pub fn report_reassigned_immutable_variable(&self,
 626                                                 span: Span,
 627                                                 lp: &LoanPath<'tcx>,
 628                                                 assign:
 629                                                 &move_data::Assignment) {
 630         let mut err = struct_span_err!(
 631             self.tcx.sess, span, E0384,
 632             "re-assignment of immutable variable `{}`",
 633             self.loan_path_to_string(lp));
 634         err.span_label(span, &format!("re-assignment of immutable variable"));
 635         if span != assign.span {
 636             err.span_label(assign.span, &format!("first assignment to `{}`",
 637                                               self.loan_path_to_string(lp)));
 638         }
 639         err.emit();
 640     }
 641
 642     pub fn span_err(&self, s: Span, m: &str) {
 643         self.tcx.sess.span_err(s, m);
 644     }
 645
 646     pub fn struct_span_err<S: Into<MultiSpan>>(&self, s: S, m: &str)
 647                                               -> DiagnosticBuilder<'a> {
 648         self.tcx.sess.struct_span_err(s, m)
 649     }
 650
 651     pub fn struct_span_err_with_code<S: Into<MultiSpan>>(&self,
 652                                                          s: S,
 653                                                          msg: &str,
 654                                                          code: &str)
 655                                                          -> DiagnosticBuilder<'a> {
 656         self.tcx.sess.struct_span_err_with_code(s, msg, code)
 657     }
 658
 659     pub fn span_err_with_code<S: Into<MultiSpan>>(&self, s: S, msg: &str, code: &str) {
 660         self.tcx.sess.span_err_with_code(s, msg, code);
 661     }
 662
 663     fn bckerr_to_diag(&self, err: &BckError<'tcx>) -> DiagnosticBuilder<'a> {
 664         let span = err.span.clone();
 665
 666         let msg = match err.code {
 667             err_mutbl => {
 668                 let descr = match err.cmt.note {
 669                     mc::NoteClosureEnv(_) | mc::NoteUpvarRef(_) => {
 670                         self.cmt_to_string(&err.cmt)
 671                     }
 672                     _ => match opt_loan_path(&err.cmt) {
 673                         None => {
 674                             format!("{} {}",
 675                                     err.cmt.mutbl.to_user_str(),
 676                                     self.cmt_to_string(&err.cmt))
 677
 678                         }
 679                         Some(lp) => {
 680                             format!("{} {} `{}`",
 681                                     err.cmt.mutbl.to_user_str(),
 682                                     self.cmt_to_string(&err.cmt),
 683                                     self.loan_path_to_string(&lp))
 684                         }
 685                     }
 686                 };
 687
 688                 match err.cause {
 689                     MutabilityViolation => {
 690                         format!("cannot assign to {}", descr)
 691                     }
 692                     BorrowViolation(euv::ClosureCapture(_)) => {
 693                         format!("closure cannot assign to {}", descr)
 694                     }
 695                     BorrowViolation(euv::OverloadedOperator) |
 696                     BorrowViolation(euv::AddrOf) |
 697                     BorrowViolation(euv::RefBinding) |
 698                     BorrowViolation(euv::AutoRef) |
 699                     BorrowViolation(euv::AutoUnsafe) |
 700                     BorrowViolation(euv::ForLoop) |
 701                     BorrowViolation(euv::MatchDiscriminant) => {
 702                         format!("cannot borrow {} as mutable", descr)
 703                     }
 704                     BorrowViolation(euv::ClosureInvocation) => {
 705                         span_bug!(err.span,
 706                             "err_mutbl with a closure invocation");
 707                     }
 708                 }
 709             }
 710             err_out_of_scope(..) => {
 711                 let msg = match opt_loan_path(&err.cmt) {
 712                     None => "borrowed value".to_string(),
 713                     Some(lp) => {
 714                         format!("`{}`", self.loan_path_to_string(&lp))
 715                     }
 716                 };
 717                 format!("{} does not live long enough", msg)
 718             }
 719             err_borrowed_pointer_too_short(..) => {
 720                 let descr = self.cmt_to_path_or_string(&err.cmt);
 721                 format!("lifetime of {} is too short to guarantee \
 722                          its contents can be safely reborrowed",
 723                         descr)
 724             }
 725         };
 726
 727         self.struct_span_err(span, &msg)
 728     }
 729
 730     pub fn report_aliasability_violation(&self,
 731                                          span: Span,
 732                                          kind: AliasableViolationKind,
 733                                          cause: mc::AliasableReason,
 734                                          cmt: mc::cmt<'tcx>) {
 735         let mut is_closure = false;
 736         let prefix = match kind {
 737             MutabilityViolation => {
 738                 "cannot assign to data"
 739             }
 740             BorrowViolation(euv::ClosureCapture(_)) |
 741             BorrowViolation(euv::OverloadedOperator) |
 742             BorrowViolation(euv::AddrOf) |
 743             BorrowViolation(euv::AutoRef) |
 744             BorrowViolation(euv::AutoUnsafe) |
 745             BorrowViolation(euv::RefBinding) |
 746             BorrowViolation(euv::MatchDiscriminant) => {
 747                 "cannot borrow data mutably"
 748             }
 749
 750             BorrowViolation(euv::ClosureInvocation) => {
 751                 is_closure = true;
 752                 "closure invocation"
 753             }
 754
 755             BorrowViolation(euv::ForLoop) => {
 756                 "`for` loop"
 757             }
 758         };
 759
 760         match cause {
 761             mc::AliasableStatic |
 762             mc::AliasableStaticMut => {
 763                 // This path cannot occur. It happens when we have an
 764                 // `&mut` or assignment to a static. But in the case
 765                 // of `static X`, we get a mutability violation first,
 766                 // and never get here. In the case of `static mut X`,
 767                 // that is unsafe and hence the aliasability error is
 768                 // ignored.
 769                 span_bug!(span, "aliasability violation for static `{}`", prefix)
 770             }
 771             mc::AliasableBorrowed => {}
 772         };
 773         let blame = cmt.immutability_blame();
 774         let mut err = match blame {
 775             Some(ImmutabilityBlame::ClosureEnv(id)) => {
 776                 let mut err = struct_span_err!(
 777                     self.tcx.sess, span, E0387,
 778                     "{} in a captured outer variable in an `Fn` closure", prefix);
 779
 780                 // FIXME: the distinction between these 2 messages looks wrong.
 781                 let help = if let BorrowViolation(euv::ClosureCapture(_)) = kind {
 782                     // The aliasability violation with closure captures can
 783                     // happen for nested closures, so we know the enclosing
 784                     // closure incorrectly accepts an `Fn` while it needs to
 785                     // be `FnMut`.
 786                     "consider changing this to accept closures that implement `FnMut`"
 787
 788                 } else {
 789                     "consider changing this closure to take self by mutable reference"
 790                 };
 791                 err.span_help(self.tcx.hir.span(id), help);
 792                 err
 793             }
 794             _ =>  {
 795                 let mut err = struct_span_err!(
 796                     self.tcx.sess, span, E0389,
 797                     "{} in a `&` reference", prefix);
 798                 err.span_label(span, &"assignment into an immutable reference");
 799                 err
 800             }
 801         };
 802         self.note_immutability_blame(&mut err, blame);
 803
 804         if is_closure {
 805             err.help("closures behind references must be called via `&mut`");
 806         }
 807         err.emit();
 808     }
 809
 810     /// Given a type, if it is an immutable reference, return a suggestion to make it mutable
 811     fn suggest_mut_for_immutable(&self, pty: &hir::Ty, is_implicit_self: bool) -> Option<String> {
 812         // Check wether the argument is an immutable reference
 813         debug!("suggest_mut_for_immutable({:?}, {:?})", pty, is_implicit_self);
 814         if let hir::TyRptr(lifetime, hir::MutTy {
 815             mutbl: hir::Mutability::MutImmutable,
 816             ref ty
 817         }) = pty.node {
 818             // Account for existing lifetimes when generating the message
 819             let pointee_snippet = match self.tcx.sess.codemap().span_to_snippet(ty.span) {
 820                 Ok(snippet) => snippet,
 821                 _ => return None
 822             };
 823
 824             let lifetime_snippet = if !lifetime.is_elided() {
 825                 format!("{} ", match self.tcx.sess.codemap().span_to_snippet(lifetime.span) {
 826                     Ok(lifetime_snippet) => lifetime_snippet,
 827                     _ => return None
 828                 })
 829             } else {
 830                 String::new()
 831             };
 832             Some(format!("use `&{}mut {}` here to make mutable",
 833                          lifetime_snippet,
 834                          if is_implicit_self { "self" } else { &*pointee_snippet }))
 835         } else {
 836             None
 837         }
 838     }
 839
 840     fn local_binding_mode(&self, node_id: ast::NodeId) -> hir::BindingMode {
 841         let pat = match self.tcx.hir.get(node_id) {
 842             hir_map::Node::NodeLocal(pat) => pat,
 843             node => bug!("bad node for local: {:?}", node)
 844         };
 845
 846         match pat.node {
 847             hir::PatKind::Binding(mode, ..) => mode,
 848             _ => bug!("local is not a binding: {:?}", pat)
 849         }
 850     }
 851
 852     fn local_ty(&self, node_id: ast::NodeId) -> (Option<&hir::Ty>, bool) {
 853         let parent = self.tcx.hir.get_parent_node(node_id);
 854         let parent_node = self.tcx.hir.get(parent);
 855
 856         // The parent node is like a fn
 857         if let Some(fn_like) = FnLikeNode::from_node(parent_node) {
 858             // `nid`'s parent's `Body`
 859             let fn_body = self.tcx.hir.body(fn_like.body());
 860             // Get the position of `node_id` in the arguments list
 861             let arg_pos = fn_body.arguments.iter().position(|arg| arg.pat.id == node_id);
 862             if let Some(i) = arg_pos {
 863                 // The argument's `Ty`
 864                 (Some(&fn_like.decl().inputs[i]),
 865                  i == 0 && fn_like.decl().has_implicit_self)
 866             } else {
 867                 (None, false)
 868             }
 869         } else {
 870             (None, false)
 871         }
 872     }
 873
 874     fn note_immutability_blame(&self,
 875                                db: &mut DiagnosticBuilder,
 876                                blame: Option<ImmutabilityBlame>) {
 877         match blame {
 878             None => {}
 879             Some(ImmutabilityBlame::ClosureEnv(_)) => {}
 880             Some(ImmutabilityBlame::ImmLocal(node_id)) => {
 881                 let let_span = self.tcx.hir.span(node_id);
 882                 if let hir::BindingMode::BindByValue(..) = self.local_binding_mode(node_id) {
 883                     if let Ok(snippet) = self.tcx.sess.codemap().span_to_snippet(let_span) {
 884                         let (_, is_implicit_self) = self.local_ty(node_id);
 885                         if is_implicit_self && snippet != "self" {
 886                             // avoid suggesting `mut &self`.
 887                             return
 888                         }
 889                         db.span_label(
 890                             let_span,
 891                             &format!("consider changing this to `mut {}`", snippet)
 892                         );
 893                     }
 894                 }
 895             }
 896             Some(ImmutabilityBlame::LocalDeref(node_id)) => {
 897                 let let_span = self.tcx.hir.span(node_id);
 898                 match self.local_binding_mode(node_id) {
 899                     hir::BindingMode::BindByRef(..) => {
 900                         let snippet = self.tcx.sess.codemap().span_to_snippet(let_span);
 901                         if let Ok(snippet) = snippet {
 902                             db.span_label(
 903                                 let_span,
 904                                 &format!("consider changing this to `{}`",
 905                                          snippet.replace("ref ", "ref mut "))
 906                             );
 907                         }
 908                     }
 909                     hir::BindingMode::BindByValue(..) => {
 910                         if let (Some(local_ty), is_implicit_self) = self.local_ty(node_id) {
 911                             if let Some(msg) =
 912                                  self.suggest_mut_for_immutable(local_ty, is_implicit_self) {
 913                                 db.span_label(local_ty.span, &msg);
 914                             }
 915                         }
 916                     }
 917                 }
 918             }
 919             Some(ImmutabilityBlame::AdtFieldDeref(_, field)) => {
 920                 let node_id = match self.tcx.hir.as_local_node_id(field.did) {
 921                     Some(node_id) => node_id,
 922                     None => return
 923                 };
 924
 925                 if let hir_map::Node::NodeField(ref field) = self.tcx.hir.get(node_id) {
 926                     if let Some(msg) = self.suggest_mut_for_immutable(&field.ty, false) {
 927                         db.span_label(field.ty.span, &msg);
 928                     }
 929                 }
 930             }
 931         }
 932     }
 933
 934     fn report_out_of_scope_escaping_closure_capture(&self,
 935                                                     err: &BckError<'tcx>,
 936                                                     capture_span: Span)
 937     {
 938         let cmt_path_or_string = self.cmt_to_path_or_string(&err.cmt);
 939
 940         let suggestion =
 941             match self.tcx.sess.codemap().span_to_snippet(err.span) {
 942                 Ok(string) => format!("move {}", string),
 943                 Err(_) => format!("move |<args>| <body>")
 944             };
 945
 946         struct_span_err!(self.tcx.sess, err.span, E0373,
 947                          "closure may outlive the current function, \
 948                           but it borrows {}, \
 949                           which is owned by the current function",
 950                          cmt_path_or_string)
 951             .span_label(capture_span,
 952                        &format!("{} is borrowed here",
 953                                 cmt_path_or_string))
 954             .span_label(err.span,
 955                        &format!("may outlive borrowed value {}",
 956                                 cmt_path_or_string))
 957             .span_suggestion(err.span,
 958                              &format!("to force the closure to take ownership of {} \
 959                                        (and any other referenced variables), \
 960                                        use the `move` keyword, as shown:",
 961                                        cmt_path_or_string),
 962                              suggestion)
 963             .emit();
 964     }
 965
 966     fn region_end_span(&self, region: &'tcx ty::Region) -> Option<Span> {
 967         match *region {
 968             ty::ReScope(scope) => {
 969                 match scope.span(&self.tcx.region_maps, &self.tcx.hir) {
 970                     Some(s) => {
 971                         Some(s.end_point())
 972                     }
 973                     None => {
 974                         None
 975                     }
 976                 }
 977             }
 978             _ => None
 979         }
 980     }
 981
 982     fn note_and_explain_bckerr(&self, db: &mut DiagnosticBuilder, err: BckError<'tcx>) {
 983         let error_span = err.span.clone();
 984         match err.code {
 985             err_mutbl => {
 986                 self.note_and_explain_mutbl_error(db, &err, &error_span);
 987                 self.note_immutability_blame(db, err.cmt.immutability_blame());
 988             }
 989             err_out_of_scope(super_scope, sub_scope, cause) => {
 990                 let (value_kind, value_msg) = match err.cmt.cat {
 991                     mc::Categorization::Rvalue(..) =>
 992                         ("temporary value", "temporary value created here"),
 993                     _ =>
 994                         ("borrowed value", "borrow occurs here")
 995                 };
 996
 997                 let is_closure = match cause {
 998                     euv::ClosureCapture(s) => {
 999                         // The primary span starts out as the closure creation point.
1000                         // Change the primary span here to highlight the use of the variable
1001                         // in the closure, because it seems more natural. Highlight
1002                         // closure creation point as a secondary span.
1003                         match db.span.primary_span() {
1004                             Some(primary) => {
1005                                 db.span = MultiSpan::from_span(s);
1006                                 db.span_label(primary, &format!("capture occurs here"));
1007                                 db.span_label(s, &"does not live long enough");
1008                                 true
1009                             }
1010                             None => false
1011                         }
1012                     }
1013                     _ => {
1014                         db.span_label(error_span, &"does not live long enough");
1015                         false
1016                     }
1017                 };
1018
1019                 let sub_span = self.region_end_span(sub_scope);
1020                 let super_span = self.region_end_span(super_scope);
1021
1022                 match (sub_span, super_span) {
1023                     (Some(s1), Some(s2)) if s1 == s2 => {
1024                         if !is_closure {
1025                             db.span = MultiSpan::from_span(s1);
1026                             db.span_label(error_span, &value_msg);
1027                             let msg = match opt_loan_path(&err.cmt) {
1028                                 None => value_kind.to_string(),
1029                                 Some(lp) => {
1030                                     format!("`{}`", self.loan_path_to_string(&lp))
1031                                 }
1032                             };
1033                             db.span_label(s1,
1034                                           &format!("{} dropped here while still borrowed", msg));
1035                         } else {
1036                             db.span_label(s1, &format!("{} dropped before borrower", value_kind));
1037                         }
1038                         db.note("values in a scope are dropped in the opposite order \
1039                                 they are created");
1040                     }
1041                     (Some(s1), Some(s2)) if !is_closure => {
1042                         db.span = MultiSpan::from_span(s2);
1043                         db.span_label(error_span, &value_msg);
1044                         let msg = match opt_loan_path(&err.cmt) {
1045                             None => value_kind.to_string(),
1046                             Some(lp) => {
1047                                 format!("`{}`", self.loan_path_to_string(&lp))
1048                             }
1049                         };
1050                         db.span_label(s2, &format!("{} dropped here while still borrowed", msg));
1051                         db.span_label(s1, &format!("{} needs to live until here", value_kind));
1052                     }
1053                     _ => {
1054                         match sub_span {
1055                             Some(s) => {
1056                                 db.span_label(s, &format!("{} needs to live until here",
1057                                                           value_kind));
1058                             }
1059                             None => {
1060                                 self.tcx.note_and_explain_region(
1061                                     db,
1062                                     "borrowed value must be valid for ",
1063                                     sub_scope,
1064                                     "...");
1065                             }
1066                         }
1067                         match super_span {
1068                             Some(s) => {
1069                                 db.span_label(s, &format!("{} only lives until here", value_kind));
1070                             }
1071                             None => {
1072                                 self.tcx.note_and_explain_region(
1073                                     db,
1074                                     "...but borrowed value is only valid for ",
1075                                     super_scope,
1076                                     "");
1077                             }
1078                         }
1079                     }
1080                 }
1081
1082                 if let Some(_) = statement_scope_span(self.tcx, super_scope) {
1083                     db.note("consider using a `let` binding to increase its lifetime");
1084                 }
1085
1086
1087
1088                 match err.cmt.cat {
1089                     mc::Categorization::Rvalue(r, or) if r != or => {
1090                         db.note("\
1091 before rustc 1.16, this temporary lived longer - see issue #39283 \
1092 (https://github.com/rust-lang/rust/issues/39283)");
1093                     }
1094                     _ => {}
1095                 }
1096             }
1097
1098             err_borrowed_pointer_too_short(loan_scope, ptr_scope) => {
1099                 let descr = match opt_loan_path(&err.cmt) {
1100                     Some(lp) => {
1101                         format!("`{}`", self.loan_path_to_string(&lp))
1102                     }
1103                     None => self.cmt_to_string(&err.cmt),
1104                 };
1105                 self.tcx.note_and_explain_region(
1106                     db,
1107                     &format!("{} would have to be valid for ",
1108                             descr),
1109                     loan_scope,
1110                     "...");
1111                 self.tcx.note_and_explain_region(
1112                     db,
1113                     &format!("...but {} is only valid for ", descr),
1114                     ptr_scope,
1115                     "");
1116             }
1117         }
1118     }
1119
1120     fn note_and_explain_mutbl_error(&self, db: &mut DiagnosticBuilder, err: &BckError<'tcx>,
1121                                     error_span: &Span) {
1122         match err.cmt.note {
1123             mc::NoteClosureEnv(upvar_id) | mc::NoteUpvarRef(upvar_id) => {
1124                 // If this is an `Fn` closure, it simply can't mutate upvars.
1125                 // If it's an `FnMut` closure, the original variable was declared immutable.
1126                 // We need to determine which is the case here.
1127                 let kind = match err.cmt.upvar().unwrap().cat {
1128                     Categorization::Upvar(mc::Upvar { kind, .. }) => kind,
1129                     _ => bug!()
1130                 };
1131                 if kind == ty::ClosureKind::Fn {
1132                     db.span_help(self.tcx.hir.span(upvar_id.closure_expr_id),
1133                                  "consider changing this closure to take \
1134                                  self by mutable reference");
1135                 }
1136             }
1137             _ => {
1138                 if let Categorization::Deref(..) = err.cmt.cat {
1139                     db.span_label(*error_span, &"cannot borrow as mutable");
1140                 } else if let Categorization::Local(local_id) = err.cmt.cat {
1141                     let span = self.tcx.hir.span(local_id);
1142                     if let Ok(snippet) = self.tcx.sess.codemap().span_to_snippet(span) {
1143                         if snippet.starts_with("ref mut ") || snippet.starts_with("&mut ") {
1144                             db.span_label(*error_span, &format!("cannot reborrow mutably"));
1145                             db.span_label(*error_span, &format!("try removing `&mut` here"));
1146                         } else {
1147                             db.span_label(*error_span, &format!("cannot borrow mutably"));
1148                         }
1149                     } else {
1150                         db.span_label(*error_span, &format!("cannot borrow mutably"));
1151                     }
1152                 } else if let Categorization::Interior(ref cmt, _) = err.cmt.cat {
1153                     if let mc::MutabilityCategory::McImmutable = cmt.mutbl {
1154                         db.span_label(*error_span,
1155                                       &"cannot mutably borrow immutable field");
1156                     }
1157                 }
1158             }
1159         }
1160     }
1161     pub fn append_loan_path_to_string(&self,
1162                                       loan_path: &LoanPath<'tcx>,
1163                                       out: &mut String) {
1164         match loan_path.kind {
1165             LpUpvar(ty::UpvarId{ var_id: id, closure_expr_id: _ }) |
1166             LpVar(id) => {
1167                 out.push_str(&self.tcx.local_var_name_str(id));
1168             }
1169
1170             LpDowncast(ref lp_base, variant_def_id) => {
1171                 out.push('(');
1172                 self.append_loan_path_to_string(&lp_base, out);
1173                 out.push_str(DOWNCAST_PRINTED_OPERATOR);
1174                 out.push_str(&self.tcx.item_path_str(variant_def_id));
1175                 out.push(')');
1176             }
1177
1178             LpExtend(ref lp_base, _, LpInterior(_, InteriorField(fname))) => {
1179                 self.append_autoderefd_loan_path_to_string(&lp_base, out);
1180                 match fname {
1181                     mc::NamedField(fname) => {
1182                         out.push('.');
1183                         out.push_str(&fname.as_str());
1184                     }
1185                     mc::PositionalField(idx) => {
1186                         out.push('.');
1187                         out.push_str(&idx.to_string());
1188                     }
1189                 }
1190             }
1191
1192             LpExtend(ref lp_base, _, LpInterior(_, InteriorElement(..))) => {
1193                 self.append_autoderefd_loan_path_to_string(&lp_base, out);
1194                 out.push_str("[..]");
1195             }
1196
1197             LpExtend(ref lp_base, _, LpDeref(_)) => {
1198                 out.push('*');
1199                 self.append_loan_path_to_string(&lp_base, out);
1200             }
1201         }
1202     }
1203
1204     pub fn append_autoderefd_loan_path_to_string(&self,
1205                                                  loan_path: &LoanPath<'tcx>,
1206                                                  out: &mut String) {
1207         match loan_path.kind {
1208             LpExtend(ref lp_base, _, LpDeref(_)) => {
1209                 // For a path like `(*x).f` or `(*x)[3]`, autoderef
1210                 // rules would normally allow users to omit the `*x`.
1211                 // So just serialize such paths to `x.f` or x[3]` respectively.
1212                 self.append_autoderefd_loan_path_to_string(&lp_base, out)
1213             }
1214
1215             LpDowncast(ref lp_base, variant_def_id) => {
1216                 out.push('(');
1217                 self.append_autoderefd_loan_path_to_string(&lp_base, out);
1218                 out.push(':');
1219                 out.push_str(&self.tcx.item_path_str(variant_def_id));
1220                 out.push(')');
1221             }
1222
1223             LpVar(..) | LpUpvar(..) | LpExtend(.., LpInterior(..)) => {
1224                 self.append_loan_path_to_string(loan_path, out)
1225             }
1226         }
1227     }
1228
1229     pub fn loan_path_to_string(&self, loan_path: &LoanPath<'tcx>) -> String {
1230         let mut result = String::new();
1231         self.append_loan_path_to_string(loan_path, &mut result);
1232         result
1233     }
1234
1235     pub fn cmt_to_string(&self, cmt: &mc::cmt_<'tcx>) -> String {
1236         cmt.descriptive_string(self.tcx)
1237     }
1238
1239     pub fn cmt_to_path_or_string(&self, cmt: &mc::cmt<'tcx>) -> String {
1240         match opt_loan_path(cmt) {
1241             Some(lp) => format!("`{}`", self.loan_path_to_string(&lp)),
1242             None => self.cmt_to_string(cmt),
1243         }
1244     }
1245 }
1246
1247 fn statement_scope_span(tcx: TyCtxt, region: &ty::Region) -> Option<Span> {
1248     match *region {
1249         ty::ReScope(scope) => {
1250             match tcx.hir.find(scope.node_id(&tcx.region_maps)) {
1251                 Some(hir_map::NodeStmt(stmt)) => Some(stmt.span),
1252                 _ => None
1253             }
1254         }
1255         _ => None
1256     }
1257 }
1258
1259 impl BitwiseOperator for LoanDataFlowOperator {
1260     #[inline]
1261     fn join(&self, succ: usize, pred: usize) -> usize {
1262         succ | pred // loans from both preds are in scope
1263     }
1264 }
1265
1266 impl DataFlowOperator for LoanDataFlowOperator {
1267     #[inline]
1268     fn initial_value(&self) -> bool {
1269         false // no loans in scope by default
1270     }
1271 }
1272
1273 impl<'tcx> fmt::Debug for InteriorKind {
1274     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1275         match *self {
1276             InteriorField(mc::NamedField(fld)) => write!(f, "{}", fld),
1277             InteriorField(mc::PositionalField(i)) => write!(f, "#{}", i),
1278             InteriorElement(..) => write!(f, "[]"),
1279         }
1280     }
1281 }
1282
1283 impl<'tcx> fmt::Debug for Loan<'tcx> {
1284     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1285         write!(f, "Loan_{}({:?}, {:?}, {:?}-{:?}, {:?})",
1286                self.index,
1287                self.loan_path,
1288                self.kind,
1289                self.gen_scope,
1290                self.kill_scope,
1291                self.restricted_paths)
1292     }
1293 }
1294
1295 impl<'tcx> fmt::Debug for LoanPath<'tcx> {
1296     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1297         match self.kind {
1298             LpVar(id) => {
1299                 write!(f, "$({})", ty::tls::with(|tcx| tcx.hir.node_to_string(id)))
1300             }
1301
1302             LpUpvar(ty::UpvarId{ var_id, closure_expr_id }) => {
1303                 let s = ty::tls::with(|tcx| tcx.hir.node_to_string(var_id));
1304                 write!(f, "$({} captured by id={})", s, closure_expr_id)
1305             }
1306
1307             LpDowncast(ref lp, variant_def_id) => {
1308                 let variant_str = if variant_def_id.is_local() {
1309                     ty::tls::with(|tcx| tcx.item_path_str(variant_def_id))
1310                 } else {
1311                     format!("{:?}", variant_def_id)
1312                 };
1313                 write!(f, "({:?}{}{})", lp, DOWNCAST_PRINTED_OPERATOR, variant_str)
1314             }
1315
1316             LpExtend(ref lp, _, LpDeref(_)) => {
1317                 write!(f, "{:?}.*", lp)
1318             }
1319
1320             LpExtend(ref lp, _, LpInterior(_, ref interior)) => {
1321                 write!(f, "{:?}.{:?}", lp, interior)
1322             }
1323         }
1324     }
1325 }
1326
1327 impl<'tcx> fmt::Display for LoanPath<'tcx> {
1328     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1329         match self.kind {
1330             LpVar(id) => {
1331                 write!(f, "$({})", ty::tls::with(|tcx| tcx.hir.node_to_user_string(id)))
1332             }
1333
1334             LpUpvar(ty::UpvarId{ var_id, closure_expr_id: _ }) => {
1335                 let s = ty::tls::with(|tcx| tcx.hir.node_to_user_string(var_id));
1336                 write!(f, "$({} captured by closure)", s)
1337             }
1338
1339             LpDowncast(ref lp, variant_def_id) => {
1340                 let variant_str = if variant_def_id.is_local() {
1341                     ty::tls::with(|tcx| tcx.item_path_str(variant_def_id))
1342                 } else {
1343                     format!("{:?}", variant_def_id)
1344                 };
1345                 write!(f, "({}{}{})", lp, DOWNCAST_PRINTED_OPERATOR, variant_str)
1346             }
1347
1348             LpExtend(ref lp, _, LpDeref(_)) => {
1349                 write!(f, "{}.*", lp)
1350             }
1351
1352             LpExtend(ref lp, _, LpInterior(_, ref interior)) => {
1353                 write!(f, "{}.{:?}", lp, interior)
1354             }
1355         }
1356     }
1357 }