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::hir::map as hir_map;
  26 use rustc::hir::map::blocks::FnLikeNode;
  27 use rustc::cfg;
  28 use rustc::middle::dataflow::DataFlowContext;
  29 use rustc::middle::dataflow::BitwiseOperator;
  30 use rustc::middle::dataflow::DataFlowOperator;
  31 use rustc::middle::dataflow::KillFrom;
  32 use rustc::hir::def_id::DefId;
  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::{self, RegionMaps};
  38 use rustc::middle::free_region::RegionRelations;
  39 use rustc::ty::{self, TyCtxt};
  40 use rustc::ty::maps::Providers;
  41
  42 use std::fmt;
  43 use std::rc::Rc;
  44 use std::hash::{Hash, Hasher};
  45 use syntax::ast;
  46 use syntax_pos::{MultiSpan, Span};
  47 use errors::DiagnosticBuilder;
  48
  49 use rustc::hir;
  50 use rustc::hir::intravisit::{self, Visitor};
  51
  52 pub mod check_loans;
  53
  54 pub mod gather_loans;
  55
  56 pub mod move_data;
  57
  58 mod mir;
  59
  60 #[derive(Clone, Copy)]
  61 pub struct LoanDataFlowOperator;
  62
  63 pub type LoanDataFlow<'a, 'tcx> = DataFlowContext<'a, 'tcx, LoanDataFlowOperator>;
  64
  65 pub fn check_crate<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>) {
  66     for body_owner_def_id in tcx.body_owners() {
  67         tcx.borrowck(body_owner_def_id);
  68     }
  69 }
  70
  71 pub fn provide(providers: &mut Providers) {
  72     *providers = Providers {
  73         borrowck,
  74         ..*providers
  75     };
  76 }
  77
  78 /// Collection of conclusions determined via borrow checker analyses.
  79 pub struct AnalysisData<'a, 'tcx: 'a> {
  80     pub all_loans: Vec<Loan<'tcx>>,
  81     pub loans: DataFlowContext<'a, 'tcx, LoanDataFlowOperator>,
  82     pub move_data: move_data::FlowedMoveData<'a, 'tcx>,
  83 }
  84
  85 fn borrowck<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, owner_def_id: DefId) {
  86     debug!("borrowck(body_owner_def_id={:?})", owner_def_id);
  87
  88     let owner_id = tcx.hir.as_local_node_id(owner_def_id).unwrap();
  89
  90     match tcx.hir.get(owner_id) {
  91         hir_map::NodeStructCtor(_) |
  92         hir_map::NodeVariant(_) => {
  93             // We get invoked with anything that has MIR, but some of
  94             // those things (notably the synthesized constructors from
  95             // tuple structs/variants) do not have an associated body
  96             // and do not need borrowchecking.
  97             return;
  98         }
  99         _ => { }
 100     }
 101
 102     let body_id = tcx.hir.body_owned_by(owner_id);
 103     let attributes = tcx.get_attrs(owner_def_id);
 104     let tables = tcx.typeck_tables_of(owner_def_id);
 105     let region_maps = tcx.region_maps(owner_def_id);
 106     let mut bccx = &mut BorrowckCtxt { tcx, tables, region_maps, owner_def_id };
 107
 108     let body = bccx.tcx.hir.body(body_id);
 109
 110     if bccx.tcx.has_attr(owner_def_id, "rustc_mir_borrowck") {
 111         mir::borrowck_mir(bccx, owner_id, &attributes);
 112     } else {
 113         // Eventually, borrowck will always read the MIR, but at the
 114         // moment we do not. So, for now, we always force MIR to be
 115         // constructed for a given fn, since this may result in errors
 116         // being reported and we want that to happen.
 117         //
 118         // Note that `mir_validated` is a "stealable" result; the
 119         // thief, `optimized_mir()`, forces borrowck, so we know that
 120         // is not yet stolen.
 121         tcx.mir_validated(owner_def_id).borrow();
 122     }
 123
 124     let cfg = cfg::CFG::new(bccx.tcx, &body);
 125     let AnalysisData { all_loans,
 126                        loans: loan_dfcx,
 127                        move_data: flowed_moves } =
 128         build_borrowck_dataflow_data(bccx, &cfg, body_id);
 129
 130     move_data::fragments::instrument_move_fragments(&flowed_moves.move_data,
 131                                                     bccx.tcx,
 132                                                     owner_id);
 133     move_data::fragments::build_unfragmented_map(bccx,
 134                                                  &flowed_moves.move_data,
 135                                                  owner_id);
 136
 137     check_loans::check_loans(bccx, &loan_dfcx, &flowed_moves, &all_loans, body);
 138 }
 139
 140 fn build_borrowck_dataflow_data<'a, 'tcx>(this: &mut BorrowckCtxt<'a, 'tcx>,
 141                                           cfg: &cfg::CFG,
 142                                           body_id: hir::BodyId)
 143                                           -> AnalysisData<'a, 'tcx>
 144 {
 145     // Check the body of fn items.
 146     let tcx = this.tcx;
 147     let body = tcx.hir.body(body_id);
 148     let id_range = {
 149         let mut visitor = intravisit::IdRangeComputingVisitor::new(&tcx.hir);
 150         visitor.visit_body(body);
 151         visitor.result()
 152     };
 153     let (all_loans, move_data) =
 154         gather_loans::gather_loans_in_fn(this, body_id);
 155
 156     let mut loan_dfcx =
 157         DataFlowContext::new(this.tcx,
 158                              "borrowck",
 159                              Some(body),
 160                              cfg,
 161                              LoanDataFlowOperator,
 162                              id_range,
 163                              all_loans.len());
 164     for (loan_idx, loan) in all_loans.iter().enumerate() {
 165         loan_dfcx.add_gen(loan.gen_scope.node_id(), loan_idx);
 166         loan_dfcx.add_kill(KillFrom::ScopeEnd,
 167                            loan.kill_scope.node_id(), loan_idx);
 168     }
 169     loan_dfcx.add_kills_from_flow_exits(cfg);
 170     loan_dfcx.propagate(cfg, body);
 171
 172     let flowed_moves = move_data::FlowedMoveData::new(move_data,
 173                                                       this,
 174                                                       cfg,
 175                                                       id_range,
 176                                                       body);
 177
 178     AnalysisData { all_loans: all_loans,
 179                    loans: loan_dfcx,
 180                    move_data:flowed_moves }
 181 }
 182
 183 /// Accessor for introspective clients inspecting `AnalysisData` and
 184 /// the `BorrowckCtxt` itself , e.g. the flowgraph visualizer.
 185 pub fn build_borrowck_dataflow_data_for_fn<'a, 'tcx>(
 186     tcx: TyCtxt<'a, 'tcx, 'tcx>,
 187     body_id: hir::BodyId,
 188     cfg: &cfg::CFG)
 189     -> (BorrowckCtxt<'a, 'tcx>, AnalysisData<'a, 'tcx>)
 190 {
 191     let owner_id = tcx.hir.body_owner(body_id);
 192     let owner_def_id = tcx.hir.local_def_id(owner_id);
 193     let tables = tcx.typeck_tables_of(owner_def_id);
 194     let region_maps = tcx.region_maps(owner_def_id);
 195     let mut bccx = BorrowckCtxt { tcx, tables, region_maps, owner_def_id };
 196
 197     let dataflow_data = build_borrowck_dataflow_data(&mut bccx, cfg, body_id);
 198     (bccx, dataflow_data)
 199 }
 200
 201 // ----------------------------------------------------------------------
 202 // Type definitions
 203
 204 pub struct BorrowckCtxt<'a, 'tcx: 'a> {
 205     tcx: TyCtxt<'a, 'tcx, 'tcx>,
 206
 207     // tables for the current thing we are checking; set to
 208     // Some in `borrowck_fn` and cleared later
 209     tables: &'a ty::TypeckTables<'tcx>,
 210
 211     region_maps: Rc<RegionMaps<'tcx>>,
 212
 213     owner_def_id: DefId,
 214 }
 215
 216 ///////////////////////////////////////////////////////////////////////////
 217 // Loans and loan paths
 218
 219 /// Record of a loan that was issued.
 220 pub struct Loan<'tcx> {
 221     index: usize,
 222     loan_path: Rc<LoanPath<'tcx>>,
 223     kind: ty::BorrowKind,
 224     restricted_paths: Vec<Rc<LoanPath<'tcx>>>,
 225
 226     /// gen_scope indicates where loan is introduced. Typically the
 227     /// loan is introduced at the point of the borrow, but in some
 228     /// cases, notably method arguments, the loan may be introduced
 229     /// only later, once it comes into scope.  See also
 230     /// `GatherLoanCtxt::compute_gen_scope`.
 231     gen_scope: region::CodeExtent<'tcx>,
 232
 233     /// kill_scope indicates when the loan goes out of scope.  This is
 234     /// either when the lifetime expires or when the local variable
 235     /// which roots the loan-path goes out of scope, whichever happens
 236     /// faster. See also `GatherLoanCtxt::compute_kill_scope`.
 237     kill_scope: region::CodeExtent<'tcx>,
 238     span: Span,
 239     cause: euv::LoanCause,
 240 }
 241
 242 impl<'tcx> Loan<'tcx> {
 243     pub fn loan_path(&self) -> Rc<LoanPath<'tcx>> {
 244         self.loan_path.clone()
 245     }
 246 }
 247
 248 #[derive(Eq)]
 249 pub struct LoanPath<'tcx> {
 250     kind: LoanPathKind<'tcx>,
 251     ty: ty::Ty<'tcx>,
 252 }
 253
 254 impl<'tcx> PartialEq for LoanPath<'tcx> {
 255     fn eq(&self, that: &LoanPath<'tcx>) -> bool {
 256         self.kind == that.kind
 257     }
 258 }
 259
 260 impl<'tcx> Hash for LoanPath<'tcx> {
 261     fn hash<H: Hasher>(&self, state: &mut H) {
 262         self.kind.hash(state);
 263     }
 264 }
 265
 266 #[derive(PartialEq, Eq, Hash, Debug)]
 267 pub enum LoanPathKind<'tcx> {
 268     LpVar(ast::NodeId),                         // `x` in README.md
 269     LpUpvar(ty::UpvarId),                       // `x` captured by-value into closure
 270     LpDowncast(Rc<LoanPath<'tcx>>, DefId), // `x` downcast to particular enum variant
 271     LpExtend(Rc<LoanPath<'tcx>>, mc::MutabilityCategory, LoanPathElem<'tcx>)
 272 }
 273
 274 impl<'tcx> LoanPath<'tcx> {
 275     fn new(kind: LoanPathKind<'tcx>, ty: ty::Ty<'tcx>) -> LoanPath<'tcx> {
 276         LoanPath { kind: kind, ty: ty }
 277     }
 278
 279     fn to_type(&self) -> ty::Ty<'tcx> { self.ty }
 280 }
 281
 282 // FIXME (pnkfelix): See discussion here
 283 // https://github.com/pnkfelix/rust/commit/
 284 //     b2b39e8700e37ad32b486b9a8409b50a8a53aa51#commitcomment-7892003
 285 const DOWNCAST_PRINTED_OPERATOR: &'static str = " as ";
 286
 287 // A local, "cleaned" version of `mc::InteriorKind` that drops
 288 // information that is not relevant to loan-path analysis. (In
 289 // particular, the distinction between how precisely an array-element
 290 // is tracked is irrelevant here.)
 291 #[derive(Clone, Copy, PartialEq, Eq, Hash)]
 292 pub enum InteriorKind {
 293     InteriorField(mc::FieldName),
 294     InteriorElement(mc::ElementKind),
 295 }
 296
 297 trait ToInteriorKind { fn cleaned(self) -> InteriorKind; }
 298 impl ToInteriorKind for mc::InteriorKind {
 299     fn cleaned(self) -> InteriorKind {
 300         match self {
 301             mc::InteriorField(name) => InteriorField(name),
 302             mc::InteriorElement(_, elem_kind) => InteriorElement(elem_kind),
 303         }
 304     }
 305 }
 306
 307 // This can be:
 308 // - a pointer dereference (`*LV` in README.md)
 309 // - a field reference, with an optional definition of the containing
 310 //   enum variant (`LV.f` in README.md)
 311 // `DefId` is present when the field is part of struct that is in
 312 // a variant of an enum. For instance in:
 313 // `enum E { X { foo: u32 }, Y { foo: u32 }}`
 314 // each `foo` is qualified by the definitition id of the variant (`X` or `Y`).
 315 #[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
 316 pub enum LoanPathElem<'tcx> {
 317     LpDeref(mc::PointerKind<'tcx>),
 318     LpInterior(Option<DefId>, InteriorKind),
 319 }
 320
 321 pub fn closure_to_block(closure_id: ast::NodeId,
 322                         tcx: TyCtxt) -> ast::NodeId {
 323     match tcx.hir.get(closure_id) {
 324         hir_map::NodeExpr(expr) => match expr.node {
 325             hir::ExprClosure(.., body_id, _) => {
 326                 body_id.node_id
 327             }
 328             _ => {
 329                 bug!("encountered non-closure id: {}", closure_id)
 330             }
 331         },
 332         _ => bug!("encountered non-expr id: {}", closure_id)
 333     }
 334 }
 335
 336 impl<'a, 'tcx> LoanPath<'tcx> {
 337     pub fn kill_scope(&self, bccx: &BorrowckCtxt<'a, 'tcx>) -> region::CodeExtent<'tcx> {
 338         match self.kind {
 339             LpVar(local_id) => bccx.region_maps.var_scope(local_id),
 340             LpUpvar(upvar_id) => {
 341                 let block_id = closure_to_block(upvar_id.closure_expr_id, bccx.tcx);
 342                 bccx.tcx.node_extent(block_id)
 343             }
 344             LpDowncast(ref base, _) |
 345             LpExtend(ref base, ..) => base.kill_scope(bccx),
 346         }
 347     }
 348
 349     fn has_fork(&self, other: &LoanPath<'tcx>) -> bool {
 350         match (&self.kind, &other.kind) {
 351             (&LpExtend(ref base, _, LpInterior(opt_variant_id, id)),
 352              &LpExtend(ref base2, _, LpInterior(opt_variant_id2, id2))) =>
 353                 if id == id2 && opt_variant_id == opt_variant_id2 {
 354                     base.has_fork(&base2)
 355                 } else {
 356                     true
 357                 },
 358             (&LpExtend(ref base, _, LpDeref(_)), _) => base.has_fork(other),
 359             (_, &LpExtend(ref base, _, LpDeref(_))) => self.has_fork(&base),
 360             _ => false,
 361         }
 362     }
 363
 364     fn depth(&self) -> usize {
 365         match self.kind {
 366             LpExtend(ref base, _, LpDeref(_)) => base.depth(),
 367             LpExtend(ref base, _, LpInterior(..)) => base.depth() + 1,
 368             _ => 0,
 369         }
 370     }
 371
 372     fn common(&self, other: &LoanPath<'tcx>) -> Option<LoanPath<'tcx>> {
 373         match (&self.kind, &other.kind) {
 374             (&LpExtend(ref base, a, LpInterior(opt_variant_id, id)),
 375              &LpExtend(ref base2, _, LpInterior(opt_variant_id2, id2))) => {
 376                 if id == id2 && opt_variant_id == opt_variant_id2 {
 377                     base.common(&base2).map(|x| {
 378                         let xd = x.depth();
 379                         if base.depth() == xd && base2.depth() == xd {
 380                             LoanPath {
 381                                 kind: LpExtend(Rc::new(x), a, LpInterior(opt_variant_id, id)),
 382                                 ty: self.ty,
 383                             }
 384                         } else {
 385                             x
 386                         }
 387                     })
 388                 } else {
 389                     base.common(&base2)
 390                 }
 391             }
 392             (&LpExtend(ref base, _, LpDeref(_)), _) => base.common(other),
 393             (_, &LpExtend(ref other, _, LpDeref(_))) => self.common(&other),
 394             (&LpVar(id), &LpVar(id2)) => {
 395                 if id == id2 {
 396                     Some(LoanPath { kind: LpVar(id), ty: self.ty })
 397                 } else {
 398                     None
 399                 }
 400             }
 401             (&LpUpvar(id), &LpUpvar(id2)) => {
 402                 if id == id2 {
 403                     Some(LoanPath { kind: LpUpvar(id), ty: self.ty })
 404                 } else {
 405                     None
 406                 }
 407             }
 408             _ => None,
 409         }
 410     }
 411 }
 412
 413 pub fn opt_loan_path<'tcx>(cmt: &mc::cmt<'tcx>) -> Option<Rc<LoanPath<'tcx>>> {
 414     //! Computes the `LoanPath` (if any) for a `cmt`.
 415     //! Note that this logic is somewhat duplicated in
 416     //! the method `compute()` found in `gather_loans::restrictions`,
 417     //! which allows it to share common loan path pieces as it
 418     //! traverses the CMT.
 419
 420     let new_lp = |v: LoanPathKind<'tcx>| Rc::new(LoanPath::new(v, cmt.ty));
 421
 422     match cmt.cat {
 423         Categorization::Rvalue(..) |
 424         Categorization::StaticItem => {
 425             None
 426         }
 427
 428         Categorization::Local(id) => {
 429             Some(new_lp(LpVar(id)))
 430         }
 431
 432         Categorization::Upvar(mc::Upvar { id, .. }) => {
 433             Some(new_lp(LpUpvar(id)))
 434         }
 435
 436         Categorization::Deref(ref cmt_base, _, pk) => {
 437             opt_loan_path(cmt_base).map(|lp| {
 438                 new_lp(LpExtend(lp, cmt.mutbl, LpDeref(pk)))
 439             })
 440         }
 441
 442         Categorization::Interior(ref cmt_base, ik) => {
 443             opt_loan_path(cmt_base).map(|lp| {
 444                 let opt_variant_id = match cmt_base.cat {
 445                     Categorization::Downcast(_, did) =>  Some(did),
 446                     _ => None
 447                 };
 448                 new_lp(LpExtend(lp, cmt.mutbl, LpInterior(opt_variant_id, ik.cleaned())))
 449             })
 450         }
 451
 452         Categorization::Downcast(ref cmt_base, variant_def_id) =>
 453             opt_loan_path(cmt_base)
 454             .map(|lp| {
 455                 new_lp(LpDowncast(lp, variant_def_id))
 456             }),
 457
 458     }
 459 }
 460
 461 ///////////////////////////////////////////////////////////////////////////
 462 // Errors
 463
 464 // Errors that can occur
 465 #[derive(Debug, PartialEq)]
 466 pub enum bckerr_code<'tcx> {
 467     err_mutbl,
 468     /// superscope, subscope, loan cause
 469     err_out_of_scope(ty::Region<'tcx>, ty::Region<'tcx>, euv::LoanCause),
 470     err_borrowed_pointer_too_short(ty::Region<'tcx>, ty::Region<'tcx>), // loan, ptr
 471 }
 472
 473 // Combination of an error code and the categorization of the expression
 474 // that caused it
 475 #[derive(Debug, PartialEq)]
 476 pub struct BckError<'tcx> {
 477     span: Span,
 478     cause: AliasableViolationKind,
 479     cmt: mc::cmt<'tcx>,
 480     code: bckerr_code<'tcx>
 481 }
 482
 483 #[derive(Copy, Clone, Debug, PartialEq)]
 484 pub enum AliasableViolationKind {
 485     MutabilityViolation,
 486     BorrowViolation(euv::LoanCause)
 487 }
 488
 489 #[derive(Copy, Clone, Debug)]
 490 pub enum MovedValueUseKind {
 491     MovedInUse,
 492     MovedInCapture,
 493 }
 494
 495 ///////////////////////////////////////////////////////////////////////////
 496 // Misc
 497
 498 impl<'a, 'tcx> BorrowckCtxt<'a, 'tcx> {
 499     pub fn is_subregion_of(&self,
 500                            r_sub: ty::Region<'tcx>,
 501                            r_sup: ty::Region<'tcx>)
 502                            -> bool
 503     {
 504         let region_rels = RegionRelations::new(self.tcx,
 505                                                self.owner_def_id,
 506                                                &self.region_maps,
 507                                                &self.tables.free_region_map);
 508         region_rels.is_subregion_of(r_sub, r_sup)
 509     }
 510
 511     pub fn report(&self, err: BckError<'tcx>) {
 512         // Catch and handle some particular cases.
 513         match (&err.code, &err.cause) {
 514             (&err_out_of_scope(&ty::ReScope(_), &ty::ReStatic, _),
 515              &BorrowViolation(euv::ClosureCapture(span))) |
 516             (&err_out_of_scope(&ty::ReScope(_), &ty::ReFree(..), _),
 517              &BorrowViolation(euv::ClosureCapture(span))) => {
 518                 return self.report_out_of_scope_escaping_closure_capture(&err, span);
 519             }
 520             _ => { }
 521         }
 522
 523         let mut db = self.bckerr_to_diag(&err);
 524         self.note_and_explain_bckerr(&mut db, err);
 525         db.emit();
 526     }
 527
 528     pub fn report_use_of_moved_value(&self,
 529                                      use_span: Span,
 530                                      use_kind: MovedValueUseKind,
 531                                      lp: &LoanPath<'tcx>,
 532                                      the_move: &move_data::Move,
 533                                      moved_lp: &LoanPath<'tcx>,
 534                                      _param_env: &ty::ParameterEnvironment<'tcx>) {
 535         let (verb, verb_participle) = match use_kind {
 536             MovedInUse => ("use", "used"),
 537             MovedInCapture => ("capture", "captured"),
 538         };
 539
 540         let (_ol, _moved_lp_msg, mut err) = match the_move.kind {
 541             move_data::Declared => {
 542                 // If this is an uninitialized variable, just emit a simple warning
 543                 // and return.
 544                 struct_span_err!(
 545                     self.tcx.sess, use_span, E0381,
 546                     "{} of possibly uninitialized variable: `{}`",
 547                     verb,
 548                     self.loan_path_to_string(lp))
 549                 .span_label(use_span, &format!("use of possibly uninitialized `{}`",
 550                     self.loan_path_to_string(lp)))
 551                 .emit();
 552                 return;
 553             }
 554             _ => {
 555                 // If moved_lp is something like `x.a`, and lp is something like `x.b`, we would
 556                 // normally generate a rather confusing message:
 557                 //
 558                 //     error: use of moved value: `x.b`
 559                 //     note: `x.a` moved here...
 560                 //
 561                 // What we want to do instead is get the 'common ancestor' of the two moves and
 562                 // use that for most of the message instead, giving is something like this:
 563                 //
 564                 //     error: use of moved value: `x`
 565                 //     note: `x` moved here (through moving `x.a`)...
 566
 567                 let common = moved_lp.common(lp);
 568                 let has_common = common.is_some();
 569                 let has_fork = moved_lp.has_fork(lp);
 570                 let (nl, ol, moved_lp_msg) =
 571                     if has_fork && has_common {
 572                         let nl = self.loan_path_to_string(&common.unwrap());
 573                         let ol = nl.clone();
 574                         let moved_lp_msg = format!(" (through moving `{}`)",
 575                                                    self.loan_path_to_string(moved_lp));
 576                         (nl, ol, moved_lp_msg)
 577                     } else {
 578                         (self.loan_path_to_string(lp),
 579                          self.loan_path_to_string(moved_lp),
 580                          String::new())
 581                     };
 582
 583                 let partial = moved_lp.depth() > lp.depth();
 584                 let msg = if !has_fork && partial { "partially " }
 585                           else if has_fork && !has_common { "collaterally "}
 586                           else { "" };
 587                 let err = struct_span_err!(
 588                     self.tcx.sess, use_span, E0382,
 589                     "{} of {}moved value: `{}`",
 590                     verb, msg, nl);
 591                 (ol, moved_lp_msg, err)}
 592         };
 593
 594         // Get type of value and span where it was previously
 595         // moved.
 596         let (move_span, move_note) = match the_move.kind {
 597             move_data::Declared => {
 598                 unreachable!();
 599             }
 600
 601             move_data::MoveExpr |
 602             move_data::MovePat =>
 603                 (self.tcx.hir.span(the_move.id), ""),
 604
 605             move_data::Captured =>
 606                 (match self.tcx.hir.expect_expr(the_move.id).node {
 607                     hir::ExprClosure(.., fn_decl_span) => fn_decl_span,
 608                     ref r => bug!("Captured({}) maps to non-closure: {:?}",
 609                                   the_move.id, r),
 610                 }, " (into closure)"),
 611         };
 612
 613         // Annotate the use and the move in the span. Watch out for
 614         // the case where the use and the move are the same. This
 615         // means the use is in a loop.
 616         err = if use_span == move_span {
 617             err.span_label(
 618                 use_span,
 619                 &format!("value moved{} here in previous iteration of loop",
 620                          move_note));
 621             err
 622         } else {
 623             err.span_label(use_span, &format!("value {} here after move", verb_participle))
 624                .span_label(move_span, &format!("value moved{} here", move_note));
 625             err
 626         };
 627
 628         err.note(&format!("move occurs because `{}` has type `{}`, \
 629                            which does not implement the `Copy` trait",
 630                           self.loan_path_to_string(moved_lp),
 631                           moved_lp.ty));
 632
 633         // Note: we used to suggest adding a `ref binding` or calling
 634         // `clone` but those suggestions have been removed because
 635         // they are often not what you actually want to do, and were
 636         // not considered particularly helpful.
 637
 638         err.emit();
 639     }
 640
 641     pub fn report_partial_reinitialization_of_uninitialized_structure(
 642             &self,
 643             span: Span,
 644             lp: &LoanPath<'tcx>) {
 645         span_err!(
 646             self.tcx.sess, span, E0383,
 647             "partial reinitialization of uninitialized structure `{}`",
 648             self.loan_path_to_string(lp));
 649     }
 650
 651     pub fn report_reassigned_immutable_variable(&self,
 652                                                 span: Span,
 653                                                 lp: &LoanPath<'tcx>,
 654                                                 assign:
 655                                                 &move_data::Assignment) {
 656         let mut err = struct_span_err!(
 657             self.tcx.sess, span, E0384,
 658             "re-assignment of immutable variable `{}`",
 659             self.loan_path_to_string(lp));
 660         err.span_label(span, &format!("re-assignment of immutable variable"));
 661         if span != assign.span {
 662             err.span_label(assign.span, &format!("first assignment to `{}`",
 663                                               self.loan_path_to_string(lp)));
 664         }
 665         err.emit();
 666     }
 667
 668     pub fn span_err(&self, s: Span, m: &str) {
 669         self.tcx.sess.span_err(s, m);
 670     }
 671
 672     pub fn struct_span_err<S: Into<MultiSpan>>(&self, s: S, m: &str)
 673                                               -> DiagnosticBuilder<'a> {
 674         self.tcx.sess.struct_span_err(s, m)
 675     }
 676
 677     pub fn struct_span_err_with_code<S: Into<MultiSpan>>(&self,
 678                                                          s: S,
 679                                                          msg: &str,
 680                                                          code: &str)
 681                                                          -> DiagnosticBuilder<'a> {
 682         self.tcx.sess.struct_span_err_with_code(s, msg, code)
 683     }
 684
 685     pub fn span_err_with_code<S: Into<MultiSpan>>(&self, s: S, msg: &str, code: &str) {
 686         self.tcx.sess.span_err_with_code(s, msg, code);
 687     }
 688
 689     fn bckerr_to_diag(&self, err: &BckError<'tcx>) -> DiagnosticBuilder<'a> {
 690         let span = err.span.clone();
 691
 692         let msg = match err.code {
 693             err_mutbl => {
 694                 let descr = match err.cmt.note {
 695                     mc::NoteClosureEnv(_) | mc::NoteUpvarRef(_) => {
 696                         self.cmt_to_string(&err.cmt)
 697                     }
 698                     _ => match opt_loan_path(&err.cmt) {
 699                         None => {
 700                             format!("{} {}",
 701                                     err.cmt.mutbl.to_user_str(),
 702                                     self.cmt_to_string(&err.cmt))
 703
 704                         }
 705                         Some(lp) => {
 706                             format!("{} {} `{}`",
 707                                     err.cmt.mutbl.to_user_str(),
 708                                     self.cmt_to_string(&err.cmt),
 709                                     self.loan_path_to_string(&lp))
 710                         }
 711                     }
 712                 };
 713
 714                 match err.cause {
 715                     MutabilityViolation => {
 716                         format!("cannot assign to {}", descr)
 717                     }
 718                     BorrowViolation(euv::ClosureCapture(_)) => {
 719                         format!("closure cannot assign to {}", descr)
 720                     }
 721                     BorrowViolation(euv::OverloadedOperator) |
 722                     BorrowViolation(euv::AddrOf) |
 723                     BorrowViolation(euv::RefBinding) |
 724                     BorrowViolation(euv::AutoRef) |
 725                     BorrowViolation(euv::AutoUnsafe) |
 726                     BorrowViolation(euv::ForLoop) |
 727                     BorrowViolation(euv::MatchDiscriminant) => {
 728                         format!("cannot borrow {} as mutable", descr)
 729                     }
 730                     BorrowViolation(euv::ClosureInvocation) => {
 731                         span_bug!(err.span,
 732                             "err_mutbl with a closure invocation");
 733                     }
 734                 }
 735             }
 736             err_out_of_scope(..) => {
 737                 let msg = match opt_loan_path(&err.cmt) {
 738                     None => "borrowed value".to_string(),
 739                     Some(lp) => {
 740                         format!("`{}`", self.loan_path_to_string(&lp))
 741                     }
 742                 };
 743                 format!("{} does not live long enough", msg)
 744             }
 745             err_borrowed_pointer_too_short(..) => {
 746                 let descr = self.cmt_to_path_or_string(&err.cmt);
 747                 format!("lifetime of {} is too short to guarantee \
 748                          its contents can be safely reborrowed",
 749                         descr)
 750             }
 751         };
 752
 753         self.struct_span_err(span, &msg)
 754     }
 755
 756     pub fn report_aliasability_violation(&self,
 757                                          span: Span,
 758                                          kind: AliasableViolationKind,
 759                                          cause: mc::AliasableReason,
 760                                          cmt: mc::cmt<'tcx>) {
 761         let mut is_closure = false;
 762         let prefix = match kind {
 763             MutabilityViolation => {
 764                 "cannot assign to data"
 765             }
 766             BorrowViolation(euv::ClosureCapture(_)) |
 767             BorrowViolation(euv::OverloadedOperator) |
 768             BorrowViolation(euv::AddrOf) |
 769             BorrowViolation(euv::AutoRef) |
 770             BorrowViolation(euv::AutoUnsafe) |
 771             BorrowViolation(euv::RefBinding) |
 772             BorrowViolation(euv::MatchDiscriminant) => {
 773                 "cannot borrow data mutably"
 774             }
 775
 776             BorrowViolation(euv::ClosureInvocation) => {
 777                 is_closure = true;
 778                 "closure invocation"
 779             }
 780
 781             BorrowViolation(euv::ForLoop) => {
 782                 "`for` loop"
 783             }
 784         };
 785
 786         match cause {
 787             mc::AliasableStatic |
 788             mc::AliasableStaticMut => {
 789                 // This path cannot occur. It happens when we have an
 790                 // `&mut` or assignment to a static. But in the case
 791                 // of `static X`, we get a mutability violation first,
 792                 // and never get here. In the case of `static mut X`,
 793                 // that is unsafe and hence the aliasability error is
 794                 // ignored.
 795                 span_bug!(span, "aliasability violation for static `{}`", prefix)
 796             }
 797             mc::AliasableBorrowed => {}
 798         };
 799         let blame = cmt.immutability_blame();
 800         let mut err = match blame {
 801             Some(ImmutabilityBlame::ClosureEnv(id)) => {
 802                 let mut err = struct_span_err!(
 803                     self.tcx.sess, span, E0387,
 804                     "{} in a captured outer variable in an `Fn` closure", prefix);
 805
 806                 // FIXME: the distinction between these 2 messages looks wrong.
 807                 let help = if let BorrowViolation(euv::ClosureCapture(_)) = kind {
 808                     // The aliasability violation with closure captures can
 809                     // happen for nested closures, so we know the enclosing
 810                     // closure incorrectly accepts an `Fn` while it needs to
 811                     // be `FnMut`.
 812                     "consider changing this to accept closures that implement `FnMut`"
 813
 814                 } else {
 815                     "consider changing this closure to take self by mutable reference"
 816                 };
 817                 err.span_help(self.tcx.hir.span(id), help);
 818                 err
 819             }
 820             _ =>  {
 821                 let mut err = struct_span_err!(
 822                     self.tcx.sess, span, E0389,
 823                     "{} in a `&` reference", prefix);
 824                 err.span_label(span, &"assignment into an immutable reference");
 825                 err
 826             }
 827         };
 828         self.note_immutability_blame(&mut err, blame);
 829
 830         if is_closure {
 831             err.help("closures behind references must be called via `&mut`");
 832         }
 833         err.emit();
 834     }
 835
 836     /// Given a type, if it is an immutable reference, return a suggestion to make it mutable
 837     fn suggest_mut_for_immutable(&self, pty: &hir::Ty, is_implicit_self: bool) -> Option<String> {
 838         // Check wether the argument is an immutable reference
 839         debug!("suggest_mut_for_immutable({:?}, {:?})", pty, is_implicit_self);
 840         if let hir::TyRptr(lifetime, hir::MutTy {
 841             mutbl: hir::Mutability::MutImmutable,
 842             ref ty
 843         }) = pty.node {
 844             // Account for existing lifetimes when generating the message
 845             let pointee_snippet = match self.tcx.sess.codemap().span_to_snippet(ty.span) {
 846                 Ok(snippet) => snippet,
 847                 _ => return None
 848             };
 849
 850             let lifetime_snippet = if !lifetime.is_elided() {
 851                 format!("{} ", match self.tcx.sess.codemap().span_to_snippet(lifetime.span) {
 852                     Ok(lifetime_snippet) => lifetime_snippet,
 853                     _ => return None
 854                 })
 855             } else {
 856                 String::new()
 857             };
 858             Some(format!("use `&{}mut {}` here to make mutable",
 859                          lifetime_snippet,
 860                          if is_implicit_self { "self" } else { &*pointee_snippet }))
 861         } else {
 862             None
 863         }
 864     }
 865
 866     fn local_binding_mode(&self, node_id: ast::NodeId) -> hir::BindingMode {
 867         let pat = match self.tcx.hir.get(node_id) {
 868             hir_map::Node::NodeLocal(pat) => pat,
 869             node => bug!("bad node for local: {:?}", node)
 870         };
 871
 872         match pat.node {
 873             hir::PatKind::Binding(mode, ..) => mode,
 874             _ => bug!("local is not a binding: {:?}", pat)
 875         }
 876     }
 877
 878     fn local_ty(&self, node_id: ast::NodeId) -> (Option<&hir::Ty>, bool) {
 879         let parent = self.tcx.hir.get_parent_node(node_id);
 880         let parent_node = self.tcx.hir.get(parent);
 881
 882         // The parent node is like a fn
 883         if let Some(fn_like) = FnLikeNode::from_node(parent_node) {
 884             // `nid`'s parent's `Body`
 885             let fn_body = self.tcx.hir.body(fn_like.body());
 886             // Get the position of `node_id` in the arguments list
 887             let arg_pos = fn_body.arguments.iter().position(|arg| arg.pat.id == node_id);
 888             if let Some(i) = arg_pos {
 889                 // The argument's `Ty`
 890                 (Some(&fn_like.decl().inputs[i]),
 891                  i == 0 && fn_like.decl().has_implicit_self)
 892             } else {
 893                 (None, false)
 894             }
 895         } else {
 896             (None, false)
 897         }
 898     }
 899
 900     fn note_immutability_blame(&self,
 901                                db: &mut DiagnosticBuilder,
 902                                blame: Option<ImmutabilityBlame>) {
 903         match blame {
 904             None => {}
 905             Some(ImmutabilityBlame::ClosureEnv(_)) => {}
 906             Some(ImmutabilityBlame::ImmLocal(node_id)) => {
 907                 let let_span = self.tcx.hir.span(node_id);
 908                 if let hir::BindingMode::BindByValue(..) = self.local_binding_mode(node_id) {
 909                     if let Ok(snippet) = self.tcx.sess.codemap().span_to_snippet(let_span) {
 910                         let (_, is_implicit_self) = self.local_ty(node_id);
 911                         if is_implicit_self && snippet != "self" {
 912                             // avoid suggesting `mut &self`.
 913                             return
 914                         }
 915                         db.span_label(
 916                             let_span,
 917                             &format!("consider changing this to `mut {}`", snippet)
 918                         );
 919                     }
 920                 }
 921             }
 922             Some(ImmutabilityBlame::LocalDeref(node_id)) => {
 923                 let let_span = self.tcx.hir.span(node_id);
 924                 match self.local_binding_mode(node_id) {
 925                     hir::BindingMode::BindByRef(..) => {
 926                         let snippet = self.tcx.sess.codemap().span_to_snippet(let_span);
 927                         if let Ok(snippet) = snippet {
 928                             db.span_label(
 929                                 let_span,
 930                                 &format!("consider changing this to `{}`",
 931                                          snippet.replace("ref ", "ref mut "))
 932                             );
 933                         }
 934                     }
 935                     hir::BindingMode::BindByValue(..) => {
 936                         if let (Some(local_ty), is_implicit_self) = self.local_ty(node_id) {
 937                             if let Some(msg) =
 938                                  self.suggest_mut_for_immutable(local_ty, is_implicit_self) {
 939                                 db.span_label(local_ty.span, &msg);
 940                             }
 941                         }
 942                     }
 943                 }
 944             }
 945             Some(ImmutabilityBlame::AdtFieldDeref(_, field)) => {
 946                 let node_id = match self.tcx.hir.as_local_node_id(field.did) {
 947                     Some(node_id) => node_id,
 948                     None => return
 949                 };
 950
 951                 if let hir_map::Node::NodeField(ref field) = self.tcx.hir.get(node_id) {
 952                     if let Some(msg) = self.suggest_mut_for_immutable(&field.ty, false) {
 953                         db.span_label(field.ty.span, &msg);
 954                     }
 955                 }
 956             }
 957         }
 958     }
 959
 960     fn report_out_of_scope_escaping_closure_capture(&self,
 961                                                     err: &BckError<'tcx>,
 962                                                     capture_span: Span)
 963     {
 964         let cmt_path_or_string = self.cmt_to_path_or_string(&err.cmt);
 965
 966         let suggestion =
 967             match self.tcx.sess.codemap().span_to_snippet(err.span) {
 968                 Ok(string) => format!("move {}", string),
 969                 Err(_) => format!("move |<args>| <body>")
 970             };
 971
 972         struct_span_err!(self.tcx.sess, err.span, E0373,
 973                          "closure may outlive the current function, \
 974                           but it borrows {}, \
 975                           which is owned by the current function",
 976                          cmt_path_or_string)
 977             .span_label(capture_span,
 978                        &format!("{} is borrowed here",
 979                                 cmt_path_or_string))
 980             .span_label(err.span,
 981                        &format!("may outlive borrowed value {}",
 982                                 cmt_path_or_string))
 983             .span_suggestion(err.span,
 984                              &format!("to force the closure to take ownership of {} \
 985                                        (and any other referenced variables), \
 986                                        use the `move` keyword, as shown:",
 987                                        cmt_path_or_string),
 988                              suggestion)
 989             .emit();
 990     }
 991
 992     fn region_end_span(&self, region: ty::Region<'tcx>) -> Option<Span> {
 993         match *region {
 994             ty::ReScope(scope) => {
 995                 match scope.span(&self.tcx.hir) {
 996                     Some(s) => {
 997                         Some(s.end_point())
 998                     }
 999                     None => {
1000                         None
1001                     }
1002                 }
1003             }
1004             _ => None
1005         }
1006     }
1007
1008     fn note_and_explain_bckerr(&self, db: &mut DiagnosticBuilder, err: BckError<'tcx>) {
1009         let error_span = err.span.clone();
1010         match err.code {
1011             err_mutbl => {
1012                 self.note_and_explain_mutbl_error(db, &err, &error_span);
1013                 self.note_immutability_blame(db, err.cmt.immutability_blame());
1014             }
1015             err_out_of_scope(super_scope, sub_scope, cause) => {
1016                 let (value_kind, value_msg) = match err.cmt.cat {
1017                     mc::Categorization::Rvalue(..) =>
1018                         ("temporary value", "temporary value created here"),
1019                     _ =>
1020                         ("borrowed value", "borrow occurs here")
1021                 };
1022
1023                 let is_closure = match cause {
1024                     euv::ClosureCapture(s) => {
1025                         // The primary span starts out as the closure creation point.
1026                         // Change the primary span here to highlight the use of the variable
1027                         // in the closure, because it seems more natural. Highlight
1028                         // closure creation point as a secondary span.
1029                         match db.span.primary_span() {
1030                             Some(primary) => {
1031                                 db.span = MultiSpan::from_span(s);
1032                                 db.span_label(primary, &format!("capture occurs here"));
1033                                 db.span_label(s, &"does not live long enough");
1034                                 true
1035                             }
1036                             None => false
1037                         }
1038                     }
1039                     _ => {
1040                         db.span_label(error_span, &"does not live long enough");
1041                         false
1042                     }
1043                 };
1044
1045                 let sub_span = self.region_end_span(sub_scope);
1046                 let super_span = self.region_end_span(super_scope);
1047
1048                 match (sub_span, super_span) {
1049                     (Some(s1), Some(s2)) if s1 == s2 => {
1050                         if !is_closure {
1051                             db.span = MultiSpan::from_span(s1);
1052                             db.span_label(error_span, &value_msg);
1053                             let msg = match opt_loan_path(&err.cmt) {
1054                                 None => value_kind.to_string(),
1055                                 Some(lp) => {
1056                                     format!("`{}`", self.loan_path_to_string(&lp))
1057                                 }
1058                             };
1059                             db.span_label(s1,
1060                                           &format!("{} dropped here while still borrowed", msg));
1061                         } else {
1062                             db.span_label(s1, &format!("{} dropped before borrower", value_kind));
1063                         }
1064                         db.note("values in a scope are dropped in the opposite order \
1065                                 they are created");
1066                     }
1067                     (Some(s1), Some(s2)) if !is_closure => {
1068                         db.span = MultiSpan::from_span(s2);
1069                         db.span_label(error_span, &value_msg);
1070                         let msg = match opt_loan_path(&err.cmt) {
1071                             None => value_kind.to_string(),
1072                             Some(lp) => {
1073                                 format!("`{}`", self.loan_path_to_string(&lp))
1074                             }
1075                         };
1076                         db.span_label(s2, &format!("{} dropped here while still borrowed", msg));
1077                         db.span_label(s1, &format!("{} needs to live until here", value_kind));
1078                     }
1079                     _ => {
1080                         match sub_span {
1081                             Some(s) => {
1082                                 db.span_label(s, &format!("{} needs to live until here",
1083                                                           value_kind));
1084                             }
1085                             None => {
1086                                 self.tcx.note_and_explain_region(
1087                                     db,
1088                                     "borrowed value must be valid for ",
1089                                     sub_scope,
1090                                     "...");
1091                             }
1092                         }
1093                         match super_span {
1094                             Some(s) => {
1095                                 db.span_label(s, &format!("{} only lives until here", value_kind));
1096                             }
1097                             None => {
1098                                 self.tcx.note_and_explain_region(
1099                                     db,
1100                                     "...but borrowed value is only valid for ",
1101                                     super_scope,
1102                                     "");
1103                             }
1104                         }
1105                     }
1106                 }
1107
1108                 if let Some(_) = statement_scope_span(self.tcx, super_scope) {
1109                     db.note("consider using a `let` binding to increase its lifetime");
1110                 }
1111
1112
1113
1114                 match err.cmt.cat {
1115                     mc::Categorization::Rvalue(r, or) if r != or => {
1116                         db.note("\
1117 before rustc 1.16, this temporary lived longer - see issue #39283 \
1118 (https://github.com/rust-lang/rust/issues/39283)");
1119                     }
1120                     _ => {}
1121                 }
1122             }
1123
1124             err_borrowed_pointer_too_short(loan_scope, ptr_scope) => {
1125                 let descr = match opt_loan_path(&err.cmt) {
1126                     Some(lp) => {
1127                         format!("`{}`", self.loan_path_to_string(&lp))
1128                     }
1129                     None => self.cmt_to_string(&err.cmt),
1130                 };
1131                 self.tcx.note_and_explain_region(
1132                     db,
1133                     &format!("{} would have to be valid for ",
1134                             descr),
1135                     loan_scope,
1136                     "...");
1137                 self.tcx.note_and_explain_region(
1138                     db,
1139                     &format!("...but {} is only valid for ", descr),
1140                     ptr_scope,
1141                     "");
1142             }
1143         }
1144     }
1145
1146     fn note_and_explain_mutbl_error(&self, db: &mut DiagnosticBuilder, err: &BckError<'tcx>,
1147                                     error_span: &Span) {
1148         match err.cmt.note {
1149             mc::NoteClosureEnv(upvar_id) | mc::NoteUpvarRef(upvar_id) => {
1150                 // If this is an `Fn` closure, it simply can't mutate upvars.
1151                 // If it's an `FnMut` closure, the original variable was declared immutable.
1152                 // We need to determine which is the case here.
1153                 let kind = match err.cmt.upvar().unwrap().cat {
1154                     Categorization::Upvar(mc::Upvar { kind, .. }) => kind,
1155                     _ => bug!()
1156                 };
1157                 if kind == ty::ClosureKind::Fn {
1158                     db.span_help(self.tcx.hir.span(upvar_id.closure_expr_id),
1159                                  "consider changing this closure to take \
1160                                  self by mutable reference");
1161                 }
1162             }
1163             _ => {
1164                 if let Categorization::Deref(..) = err.cmt.cat {
1165                     db.span_label(*error_span, &"cannot borrow as mutable");
1166                 } else if let Categorization::Local(local_id) = err.cmt.cat {
1167                     let span = self.tcx.hir.span(local_id);
1168                     if let Ok(snippet) = self.tcx.sess.codemap().span_to_snippet(span) {
1169                         if snippet.starts_with("ref mut ") || snippet.starts_with("&mut ") {
1170                             db.span_label(*error_span, &format!("cannot reborrow mutably"));
1171                             db.span_label(*error_span, &format!("try removing `&mut` here"));
1172                         } else {
1173                             db.span_label(*error_span, &format!("cannot borrow mutably"));
1174                         }
1175                     } else {
1176                         db.span_label(*error_span, &format!("cannot borrow mutably"));
1177                     }
1178                 } else if let Categorization::Interior(ref cmt, _) = err.cmt.cat {
1179                     if let mc::MutabilityCategory::McImmutable = cmt.mutbl {
1180                         db.span_label(*error_span,
1181                                       &"cannot mutably borrow immutable field");
1182                     }
1183                 }
1184             }
1185         }
1186     }
1187     pub fn append_loan_path_to_string(&self,
1188                                       loan_path: &LoanPath<'tcx>,
1189                                       out: &mut String) {
1190         match loan_path.kind {
1191             LpUpvar(ty::UpvarId{ var_id: id, closure_expr_id: _ }) |
1192             LpVar(id) => {
1193                 out.push_str(&self.tcx.local_var_name_str(id));
1194             }
1195
1196             LpDowncast(ref lp_base, variant_def_id) => {
1197                 out.push('(');
1198                 self.append_loan_path_to_string(&lp_base, out);
1199                 out.push_str(DOWNCAST_PRINTED_OPERATOR);
1200                 out.push_str(&self.tcx.item_path_str(variant_def_id));
1201                 out.push(')');
1202             }
1203
1204             LpExtend(ref lp_base, _, LpInterior(_, InteriorField(fname))) => {
1205                 self.append_autoderefd_loan_path_to_string(&lp_base, out);
1206                 match fname {
1207                     mc::NamedField(fname) => {
1208                         out.push('.');
1209                         out.push_str(&fname.as_str());
1210                     }
1211                     mc::PositionalField(idx) => {
1212                         out.push('.');
1213                         out.push_str(&idx.to_string());
1214                     }
1215                 }
1216             }
1217
1218             LpExtend(ref lp_base, _, LpInterior(_, InteriorElement(..))) => {
1219                 self.append_autoderefd_loan_path_to_string(&lp_base, out);
1220                 out.push_str("[..]");
1221             }
1222
1223             LpExtend(ref lp_base, _, LpDeref(_)) => {
1224                 out.push('*');
1225                 self.append_loan_path_to_string(&lp_base, out);
1226             }
1227         }
1228     }
1229
1230     pub fn append_autoderefd_loan_path_to_string(&self,
1231                                                  loan_path: &LoanPath<'tcx>,
1232                                                  out: &mut String) {
1233         match loan_path.kind {
1234             LpExtend(ref lp_base, _, LpDeref(_)) => {
1235                 // For a path like `(*x).f` or `(*x)[3]`, autoderef
1236                 // rules would normally allow users to omit the `*x`.
1237                 // So just serialize such paths to `x.f` or x[3]` respectively.
1238                 self.append_autoderefd_loan_path_to_string(&lp_base, out)
1239             }
1240
1241             LpDowncast(ref lp_base, variant_def_id) => {
1242                 out.push('(');
1243                 self.append_autoderefd_loan_path_to_string(&lp_base, out);
1244                 out.push(':');
1245                 out.push_str(&self.tcx.item_path_str(variant_def_id));
1246                 out.push(')');
1247             }
1248
1249             LpVar(..) | LpUpvar(..) | LpExtend(.., LpInterior(..)) => {
1250                 self.append_loan_path_to_string(loan_path, out)
1251             }
1252         }
1253     }
1254
1255     pub fn loan_path_to_string(&self, loan_path: &LoanPath<'tcx>) -> String {
1256         let mut result = String::new();
1257         self.append_loan_path_to_string(loan_path, &mut result);
1258         result
1259     }
1260
1261     pub fn cmt_to_string(&self, cmt: &mc::cmt_<'tcx>) -> String {
1262         cmt.descriptive_string(self.tcx)
1263     }
1264
1265     pub fn cmt_to_path_or_string(&self, cmt: &mc::cmt<'tcx>) -> String {
1266         match opt_loan_path(cmt) {
1267             Some(lp) => format!("`{}`", self.loan_path_to_string(&lp)),
1268             None => self.cmt_to_string(cmt),
1269         }
1270     }
1271 }
1272
1273 fn statement_scope_span(tcx: TyCtxt, region: ty::Region) -> Option<Span> {
1274     match *region {
1275         ty::ReScope(scope) => {
1276             match tcx.hir.find(scope.node_id()) {
1277                 Some(hir_map::NodeStmt(stmt)) => Some(stmt.span),
1278                 _ => None
1279             }
1280         }
1281         _ => None
1282     }
1283 }
1284
1285 impl BitwiseOperator for LoanDataFlowOperator {
1286     #[inline]
1287     fn join(&self, succ: usize, pred: usize) -> usize {
1288         succ | pred // loans from both preds are in scope
1289     }
1290 }
1291
1292 impl DataFlowOperator for LoanDataFlowOperator {
1293     #[inline]
1294     fn initial_value(&self) -> bool {
1295         false // no loans in scope by default
1296     }
1297 }
1298
1299 impl<'tcx> fmt::Debug for InteriorKind {
1300     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1301         match *self {
1302             InteriorField(mc::NamedField(fld)) => write!(f, "{}", fld),
1303             InteriorField(mc::PositionalField(i)) => write!(f, "#{}", i),
1304             InteriorElement(..) => write!(f, "[]"),
1305         }
1306     }
1307 }
1308
1309 impl<'tcx> fmt::Debug for Loan<'tcx> {
1310     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1311         write!(f, "Loan_{}({:?}, {:?}, {:?}-{:?}, {:?})",
1312                self.index,
1313                self.loan_path,
1314                self.kind,
1315                self.gen_scope,
1316                self.kill_scope,
1317                self.restricted_paths)
1318     }
1319 }
1320
1321 impl<'tcx> fmt::Debug for LoanPath<'tcx> {
1322     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1323         match self.kind {
1324             LpVar(id) => {
1325                 write!(f, "$({})", ty::tls::with(|tcx| tcx.hir.node_to_string(id)))
1326             }
1327
1328             LpUpvar(ty::UpvarId{ var_id, closure_expr_id }) => {
1329                 let s = ty::tls::with(|tcx| tcx.hir.node_to_string(var_id));
1330                 write!(f, "$({} captured by id={})", s, closure_expr_id)
1331             }
1332
1333             LpDowncast(ref lp, variant_def_id) => {
1334                 let variant_str = if variant_def_id.is_local() {
1335                     ty::tls::with(|tcx| tcx.item_path_str(variant_def_id))
1336                 } else {
1337                     format!("{:?}", variant_def_id)
1338                 };
1339                 write!(f, "({:?}{}{})", lp, DOWNCAST_PRINTED_OPERATOR, variant_str)
1340             }
1341
1342             LpExtend(ref lp, _, LpDeref(_)) => {
1343                 write!(f, "{:?}.*", lp)
1344             }
1345
1346             LpExtend(ref lp, _, LpInterior(_, ref interior)) => {
1347                 write!(f, "{:?}.{:?}", lp, interior)
1348             }
1349         }
1350     }
1351 }
1352
1353 impl<'tcx> fmt::Display for LoanPath<'tcx> {
1354     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1355         match self.kind {
1356             LpVar(id) => {
1357                 write!(f, "$({})", ty::tls::with(|tcx| tcx.hir.node_to_user_string(id)))
1358             }
1359
1360             LpUpvar(ty::UpvarId{ var_id, closure_expr_id: _ }) => {
1361                 let s = ty::tls::with(|tcx| tcx.hir.node_to_user_string(var_id));
1362                 write!(f, "$({} captured by closure)", s)
1363             }
1364
1365             LpDowncast(ref lp, variant_def_id) => {
1366                 let variant_str = if variant_def_id.is_local() {
1367                     ty::tls::with(|tcx| tcx.item_path_str(variant_def_id))
1368                 } else {
1369                     format!("{:?}", variant_def_id)
1370                 };
1371                 write!(f, "({}{}{})", lp, DOWNCAST_PRINTED_OPERATOR, variant_str)
1372             }
1373
1374             LpExtend(ref lp, _, LpDeref(_)) => {
1375                 write!(f, "{}.*", lp)
1376             }
1377
1378             LpExtend(ref lp, _, LpInterior(_, ref interior)) => {
1379                 write!(f, "{}.{:?}", lp, interior)
1380             }
1381         }
1382     }
1383 }