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 syntax_pos::DUMMY_SP;
  43
  44 use std::fmt;
  45 use std::rc::Rc;
  46 use std::hash::{Hash, Hasher};
  47 use syntax::ast;
  48 use syntax_pos::{MultiSpan, Span};
  49 use errors::DiagnosticBuilder;
  50
  51 use rustc::hir;
  52 use rustc::hir::intravisit::{self, Visitor};
  53
  54 pub mod check_loans;
  55
  56 pub mod gather_loans;
  57
  58 pub mod move_data;
  59
  60 mod mir;
  61
  62 #[derive(Clone, Copy)]
  63 pub struct LoanDataFlowOperator;
  64
  65 pub type LoanDataFlow<'a, 'tcx> = DataFlowContext<'a, 'tcx, LoanDataFlowOperator>;
  66
  67 pub fn check_crate<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>) {
  68     for body_owner_def_id in tcx.body_owners() {
  69         tcx.borrowck(body_owner_def_id);
  70     }
  71 }
  72
  73 pub fn provide(providers: &mut Providers) {
  74     *providers = Providers {
  75         borrowck,
  76         ..*providers
  77     };
  78 }
  79
  80 /// Collection of conclusions determined via borrow checker analyses.
  81 pub struct AnalysisData<'a, 'tcx: 'a> {
  82     pub all_loans: Vec<Loan<'tcx>>,
  83     pub loans: DataFlowContext<'a, 'tcx, LoanDataFlowOperator>,
  84     pub move_data: move_data::FlowedMoveData<'a, 'tcx>,
  85 }
  86
  87 fn borrowck<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, owner_def_id: DefId) {
  88     debug!("borrowck(body_owner_def_id={:?})", owner_def_id);
  89
  90     let owner_id = tcx.hir.as_local_node_id(owner_def_id).unwrap();
  91
  92     match tcx.hir.get(owner_id) {
  93         hir_map::NodeStructCtor(_) |
  94         hir_map::NodeVariant(_) => {
  95             // We get invoked with anything that has MIR, but some of
  96             // those things (notably the synthesized constructors from
  97             // tuple structs/variants) do not have an associated body
  98             // and do not need borrowchecking.
  99             return;
 100         }
 101         _ => { }
 102     }
 103
 104     let body_id = tcx.hir.body_owned_by(owner_id);
 105     let attributes = tcx.get_attrs(owner_def_id);
 106     let tables = tcx.typeck_tables_of(owner_def_id);
 107     let region_maps = tcx.region_maps(owner_def_id);
 108     let mut bccx = &mut BorrowckCtxt { tcx, tables, region_maps, owner_def_id };
 109
 110     let body = bccx.tcx.hir.body(body_id);
 111
 112     if bccx.tcx.has_attr(owner_def_id, "rustc_mir_borrowck") {
 113         mir::borrowck_mir(bccx, owner_id, &attributes);
 114     } else {
 115         // Eventually, borrowck will always read the MIR, but at the
 116         // moment we do not. So, for now, we always force MIR to be
 117         // constructed for a given fn, since this may result in errors
 118         // being reported and we want that to happen.
 119         //
 120         // Note that `mir_validated` is a "stealable" result; the
 121         // thief, `optimized_mir()`, forces borrowck, so we know that
 122         // is not yet stolen.
 123         tcx.mir_validated(owner_def_id).borrow();
 124     }
 125
 126     let cfg = cfg::CFG::new(bccx.tcx, &body);
 127     let AnalysisData { all_loans,
 128                        loans: loan_dfcx,
 129                        move_data: flowed_moves } =
 130         build_borrowck_dataflow_data(bccx, &cfg, body_id);
 131
 132     check_loans::check_loans(bccx, &loan_dfcx, &flowed_moves, &all_loans, body);
 133 }
 134
 135 fn build_borrowck_dataflow_data<'a, 'tcx>(this: &mut BorrowckCtxt<'a, 'tcx>,
 136                                           cfg: &cfg::CFG,
 137                                           body_id: hir::BodyId)
 138                                           -> AnalysisData<'a, 'tcx>
 139 {
 140     // Check the body of fn items.
 141     let tcx = this.tcx;
 142     let body = tcx.hir.body(body_id);
 143     let id_range = {
 144         let mut visitor = intravisit::IdRangeComputingVisitor::new(&tcx.hir);
 145         visitor.visit_body(body);
 146         visitor.result()
 147     };
 148     let (all_loans, move_data) =
 149         gather_loans::gather_loans_in_fn(this, body_id);
 150
 151     let mut loan_dfcx =
 152         DataFlowContext::new(this.tcx,
 153                              "borrowck",
 154                              Some(body),
 155                              cfg,
 156                              LoanDataFlowOperator,
 157                              id_range,
 158                              all_loans.len());
 159     for (loan_idx, loan) in all_loans.iter().enumerate() {
 160         loan_dfcx.add_gen(loan.gen_scope.node_id(), loan_idx);
 161         loan_dfcx.add_kill(KillFrom::ScopeEnd,
 162                            loan.kill_scope.node_id(), loan_idx);
 163     }
 164     loan_dfcx.add_kills_from_flow_exits(cfg);
 165     loan_dfcx.propagate(cfg, body);
 166
 167     let flowed_moves = move_data::FlowedMoveData::new(move_data,
 168                                                       this,
 169                                                       cfg,
 170                                                       id_range,
 171                                                       body);
 172
 173     AnalysisData { all_loans: all_loans,
 174                    loans: loan_dfcx,
 175                    move_data:flowed_moves }
 176 }
 177
 178 /// Accessor for introspective clients inspecting `AnalysisData` and
 179 /// the `BorrowckCtxt` itself , e.g. the flowgraph visualizer.
 180 pub fn build_borrowck_dataflow_data_for_fn<'a, 'tcx>(
 181     tcx: TyCtxt<'a, 'tcx, 'tcx>,
 182     body_id: hir::BodyId,
 183     cfg: &cfg::CFG)
 184     -> (BorrowckCtxt<'a, 'tcx>, AnalysisData<'a, 'tcx>)
 185 {
 186     let owner_id = tcx.hir.body_owner(body_id);
 187     let owner_def_id = tcx.hir.local_def_id(owner_id);
 188     let tables = tcx.typeck_tables_of(owner_def_id);
 189     let region_maps = tcx.region_maps(owner_def_id);
 190     let mut bccx = BorrowckCtxt { tcx, tables, region_maps, owner_def_id };
 191
 192     let dataflow_data = build_borrowck_dataflow_data(&mut bccx, cfg, body_id);
 193     (bccx, dataflow_data)
 194 }
 195
 196 // ----------------------------------------------------------------------
 197 // Type definitions
 198
 199 pub struct BorrowckCtxt<'a, 'tcx: 'a> {
 200     tcx: TyCtxt<'a, 'tcx, 'tcx>,
 201
 202     // tables for the current thing we are checking; set to
 203     // Some in `borrowck_fn` and cleared later
 204     tables: &'a ty::TypeckTables<'tcx>,
 205
 206     region_maps: Rc<RegionMaps>,
 207
 208     owner_def_id: DefId,
 209 }
 210
 211 ///////////////////////////////////////////////////////////////////////////
 212 // Loans and loan paths
 213
 214 /// Record of a loan that was issued.
 215 pub struct Loan<'tcx> {
 216     index: usize,
 217     loan_path: Rc<LoanPath<'tcx>>,
 218     kind: ty::BorrowKind,
 219     restricted_paths: Vec<Rc<LoanPath<'tcx>>>,
 220
 221     /// gen_scope indicates where loan is introduced. Typically the
 222     /// loan is introduced at the point of the borrow, but in some
 223     /// cases, notably method arguments, the loan may be introduced
 224     /// only later, once it comes into scope.  See also
 225     /// `GatherLoanCtxt::compute_gen_scope`.
 226     gen_scope: region::CodeExtent,
 227
 228     /// kill_scope indicates when the loan goes out of scope.  This is
 229     /// either when the lifetime expires or when the local variable
 230     /// which roots the loan-path goes out of scope, whichever happens
 231     /// faster. See also `GatherLoanCtxt::compute_kill_scope`.
 232     kill_scope: region::CodeExtent,
 233     span: Span,
 234     cause: euv::LoanCause,
 235 }
 236
 237 impl<'tcx> Loan<'tcx> {
 238     pub fn loan_path(&self) -> Rc<LoanPath<'tcx>> {
 239         self.loan_path.clone()
 240     }
 241 }
 242
 243 #[derive(Eq)]
 244 pub struct LoanPath<'tcx> {
 245     kind: LoanPathKind<'tcx>,
 246     ty: ty::Ty<'tcx>,
 247 }
 248
 249 impl<'tcx> PartialEq for LoanPath<'tcx> {
 250     fn eq(&self, that: &LoanPath<'tcx>) -> bool {
 251         self.kind == that.kind
 252     }
 253 }
 254
 255 impl<'tcx> Hash for LoanPath<'tcx> {
 256     fn hash<H: Hasher>(&self, state: &mut H) {
 257         self.kind.hash(state);
 258     }
 259 }
 260
 261 #[derive(PartialEq, Eq, Hash, Debug)]
 262 pub enum LoanPathKind<'tcx> {
 263     LpVar(ast::NodeId),                         // `x` in README.md
 264     LpUpvar(ty::UpvarId),                       // `x` captured by-value into closure
 265     LpDowncast(Rc<LoanPath<'tcx>>, DefId), // `x` downcast to particular enum variant
 266     LpExtend(Rc<LoanPath<'tcx>>, mc::MutabilityCategory, LoanPathElem<'tcx>)
 267 }
 268
 269 impl<'tcx> LoanPath<'tcx> {
 270     fn new(kind: LoanPathKind<'tcx>, ty: ty::Ty<'tcx>) -> LoanPath<'tcx> {
 271         LoanPath { kind: kind, ty: ty }
 272     }
 273
 274     fn to_type(&self) -> ty::Ty<'tcx> { self.ty }
 275 }
 276
 277 // FIXME (pnkfelix): See discussion here
 278 // https://github.com/pnkfelix/rust/commit/
 279 //     b2b39e8700e37ad32b486b9a8409b50a8a53aa51#commitcomment-7892003
 280 const DOWNCAST_PRINTED_OPERATOR: &'static str = " as ";
 281
 282 // A local, "cleaned" version of `mc::InteriorKind` that drops
 283 // information that is not relevant to loan-path analysis. (In
 284 // particular, the distinction between how precisely an array-element
 285 // is tracked is irrelevant here.)
 286 #[derive(Clone, Copy, PartialEq, Eq, Hash)]
 287 pub enum InteriorKind {
 288     InteriorField(mc::FieldName),
 289     InteriorElement(mc::ElementKind),
 290 }
 291
 292 trait ToInteriorKind { fn cleaned(self) -> InteriorKind; }
 293 impl ToInteriorKind for mc::InteriorKind {
 294     fn cleaned(self) -> InteriorKind {
 295         match self {
 296             mc::InteriorField(name) => InteriorField(name),
 297             mc::InteriorElement(_, elem_kind) => InteriorElement(elem_kind),
 298         }
 299     }
 300 }
 301
 302 // This can be:
 303 // - a pointer dereference (`*LV` in README.md)
 304 // - a field reference, with an optional definition of the containing
 305 //   enum variant (`LV.f` in README.md)
 306 // `DefId` is present when the field is part of struct that is in
 307 // a variant of an enum. For instance in:
 308 // `enum E { X { foo: u32 }, Y { foo: u32 }}`
 309 // each `foo` is qualified by the definitition id of the variant (`X` or `Y`).
 310 #[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
 311 pub enum LoanPathElem<'tcx> {
 312     LpDeref(mc::PointerKind<'tcx>),
 313     LpInterior(Option<DefId>, InteriorKind),
 314 }
 315
 316 pub fn closure_to_block(closure_id: ast::NodeId,
 317                         tcx: TyCtxt) -> ast::NodeId {
 318     match tcx.hir.get(closure_id) {
 319         hir_map::NodeExpr(expr) => match expr.node {
 320             hir::ExprClosure(.., body_id, _) => {
 321                 body_id.node_id
 322             }
 323             _ => {
 324                 bug!("encountered non-closure id: {}", closure_id)
 325             }
 326         },
 327         _ => bug!("encountered non-expr id: {}", closure_id)
 328     }
 329 }
 330
 331 impl<'a, 'tcx> LoanPath<'tcx> {
 332     pub fn kill_scope(&self, bccx: &BorrowckCtxt<'a, 'tcx>) -> region::CodeExtent {
 333         match self.kind {
 334             LpVar(local_id) => bccx.region_maps.var_scope(local_id),
 335             LpUpvar(upvar_id) => {
 336                 let block_id = closure_to_block(upvar_id.closure_expr_id, bccx.tcx);
 337                 region::CodeExtent::Misc(block_id)
 338             }
 339             LpDowncast(ref base, _) |
 340             LpExtend(ref base, ..) => base.kill_scope(bccx),
 341         }
 342     }
 343
 344     fn has_fork(&self, other: &LoanPath<'tcx>) -> bool {
 345         match (&self.kind, &other.kind) {
 346             (&LpExtend(ref base, _, LpInterior(opt_variant_id, id)),
 347              &LpExtend(ref base2, _, LpInterior(opt_variant_id2, id2))) =>
 348                 if id == id2 && opt_variant_id == opt_variant_id2 {
 349                     base.has_fork(&base2)
 350                 } else {
 351                     true
 352                 },
 353             (&LpExtend(ref base, _, LpDeref(_)), _) => base.has_fork(other),
 354             (_, &LpExtend(ref base, _, LpDeref(_))) => self.has_fork(&base),
 355             _ => false,
 356         }
 357     }
 358
 359     fn depth(&self) -> usize {
 360         match self.kind {
 361             LpExtend(ref base, _, LpDeref(_)) => base.depth(),
 362             LpExtend(ref base, _, LpInterior(..)) => base.depth() + 1,
 363             _ => 0,
 364         }
 365     }
 366
 367     fn common(&self, other: &LoanPath<'tcx>) -> Option<LoanPath<'tcx>> {
 368         match (&self.kind, &other.kind) {
 369             (&LpExtend(ref base, a, LpInterior(opt_variant_id, id)),
 370              &LpExtend(ref base2, _, LpInterior(opt_variant_id2, id2))) => {
 371                 if id == id2 && opt_variant_id == opt_variant_id2 {
 372                     base.common(&base2).map(|x| {
 373                         let xd = x.depth();
 374                         if base.depth() == xd && base2.depth() == xd {
 375                             LoanPath {
 376                                 kind: LpExtend(Rc::new(x), a, LpInterior(opt_variant_id, id)),
 377                                 ty: self.ty,
 378                             }
 379                         } else {
 380                             x
 381                         }
 382                     })
 383                 } else {
 384                     base.common(&base2)
 385                 }
 386             }
 387             (&LpExtend(ref base, _, LpDeref(_)), _) => base.common(other),
 388             (_, &LpExtend(ref other, _, LpDeref(_))) => self.common(&other),
 389             (&LpVar(id), &LpVar(id2)) => {
 390                 if id == id2 {
 391                     Some(LoanPath { kind: LpVar(id), ty: self.ty })
 392                 } else {
 393                     None
 394                 }
 395             }
 396             (&LpUpvar(id), &LpUpvar(id2)) => {
 397                 if id == id2 {
 398                     Some(LoanPath { kind: LpUpvar(id), ty: self.ty })
 399                 } else {
 400                     None
 401                 }
 402             }
 403             _ => None,
 404         }
 405     }
 406 }
 407
 408 pub fn opt_loan_path<'tcx>(cmt: &mc::cmt<'tcx>) -> Option<Rc<LoanPath<'tcx>>> {
 409     //! Computes the `LoanPath` (if any) for a `cmt`.
 410     //! Note that this logic is somewhat duplicated in
 411     //! the method `compute()` found in `gather_loans::restrictions`,
 412     //! which allows it to share common loan path pieces as it
 413     //! traverses the CMT.
 414
 415     let new_lp = |v: LoanPathKind<'tcx>| Rc::new(LoanPath::new(v, cmt.ty));
 416
 417     match cmt.cat {
 418         Categorization::Rvalue(..) |
 419         Categorization::StaticItem => {
 420             None
 421         }
 422
 423         Categorization::Local(id) => {
 424             Some(new_lp(LpVar(id)))
 425         }
 426
 427         Categorization::Upvar(mc::Upvar { id, .. }) => {
 428             Some(new_lp(LpUpvar(id)))
 429         }
 430
 431         Categorization::Deref(ref cmt_base, _, pk) => {
 432             opt_loan_path(cmt_base).map(|lp| {
 433                 new_lp(LpExtend(lp, cmt.mutbl, LpDeref(pk)))
 434             })
 435         }
 436
 437         Categorization::Interior(ref cmt_base, ik) => {
 438             opt_loan_path(cmt_base).map(|lp| {
 439                 let opt_variant_id = match cmt_base.cat {
 440                     Categorization::Downcast(_, did) =>  Some(did),
 441                     _ => None
 442                 };
 443                 new_lp(LpExtend(lp, cmt.mutbl, LpInterior(opt_variant_id, ik.cleaned())))
 444             })
 445         }
 446
 447         Categorization::Downcast(ref cmt_base, variant_def_id) =>
 448             opt_loan_path(cmt_base)
 449             .map(|lp| {
 450                 new_lp(LpDowncast(lp, variant_def_id))
 451             }),
 452
 453     }
 454 }
 455
 456 ///////////////////////////////////////////////////////////////////////////
 457 // Errors
 458
 459 // Errors that can occur
 460 #[derive(Debug, PartialEq)]
 461 pub enum bckerr_code<'tcx> {
 462     err_mutbl,
 463     /// superscope, subscope, loan cause
 464     err_out_of_scope(ty::Region<'tcx>, ty::Region<'tcx>, euv::LoanCause),
 465     err_borrowed_pointer_too_short(ty::Region<'tcx>, ty::Region<'tcx>), // loan, ptr
 466 }
 467
 468 // Combination of an error code and the categorization of the expression
 469 // that caused it
 470 #[derive(Debug, PartialEq)]
 471 pub struct BckError<'tcx> {
 472     span: Span,
 473     cause: AliasableViolationKind,
 474     cmt: mc::cmt<'tcx>,
 475     code: bckerr_code<'tcx>
 476 }
 477
 478 #[derive(Copy, Clone, Debug, PartialEq)]
 479 pub enum AliasableViolationKind {
 480     MutabilityViolation,
 481     BorrowViolation(euv::LoanCause)
 482 }
 483
 484 #[derive(Copy, Clone, Debug)]
 485 pub enum MovedValueUseKind {
 486     MovedInUse,
 487     MovedInCapture,
 488 }
 489
 490 ///////////////////////////////////////////////////////////////////////////
 491 // Misc
 492
 493 impl<'a, 'tcx> BorrowckCtxt<'a, 'tcx> {
 494     pub fn is_subregion_of(&self,
 495                            r_sub: ty::Region<'tcx>,
 496                            r_sup: ty::Region<'tcx>)
 497                            -> bool
 498     {
 499         let region_rels = RegionRelations::new(self.tcx,
 500                                                self.owner_def_id,
 501                                                &self.region_maps,
 502                                                &self.tables.free_region_map);
 503         region_rels.is_subregion_of(r_sub, r_sup)
 504     }
 505
 506     pub fn report(&self, err: BckError<'tcx>) {
 507         // Catch and handle some particular cases.
 508         match (&err.code, &err.cause) {
 509             (&err_out_of_scope(&ty::ReScope(_), &ty::ReStatic, _),
 510              &BorrowViolation(euv::ClosureCapture(span))) |
 511             (&err_out_of_scope(&ty::ReScope(_), &ty::ReEarlyBound(..), _),
 512              &BorrowViolation(euv::ClosureCapture(span))) |
 513             (&err_out_of_scope(&ty::ReScope(_), &ty::ReFree(..), _),
 514              &BorrowViolation(euv::ClosureCapture(span))) => {
 515                 return self.report_out_of_scope_escaping_closure_capture(&err, span);
 516             }
 517             _ => { }
 518         }
 519
 520         let mut db = self.bckerr_to_diag(&err);
 521         self.note_and_explain_bckerr(&mut db, err);
 522         db.emit();
 523     }
 524
 525     pub fn report_use_of_moved_value(&self,
 526                                      use_span: Span,
 527                                      use_kind: MovedValueUseKind,
 528                                      lp: &LoanPath<'tcx>,
 529                                      the_move: &move_data::Move,
 530                                      moved_lp: &LoanPath<'tcx>,
 531                                      _param_env: &ty::ParamEnv<'tcx>) {
 532         let (verb, verb_participle) = match use_kind {
 533             MovedInUse => ("use", "used"),
 534             MovedInCapture => ("capture", "captured"),
 535         };
 536
 537         let (_ol, _moved_lp_msg, mut err, need_note) = match the_move.kind {
 538             move_data::Declared => {
 539                 // If this is an uninitialized variable, just emit a simple warning
 540                 // and return.
 541                 struct_span_err!(
 542                     self.tcx.sess, use_span, E0381,
 543                     "{} of possibly uninitialized variable: `{}`",
 544                     verb,
 545                     self.loan_path_to_string(lp))
 546                 .span_label(use_span, format!("use of possibly uninitialized `{}`",
 547                     self.loan_path_to_string(lp)))
 548                 .emit();
 549                 return;
 550             }
 551             _ => {
 552                 // If moved_lp is something like `x.a`, and lp is something like `x.b`, we would
 553                 // normally generate a rather confusing message:
 554                 //
 555                 //     error: use of moved value: `x.b`
 556                 //     note: `x.a` moved here...
 557                 //
 558                 // What we want to do instead is get the 'common ancestor' of the two moves and
 559                 // use that for most of the message instead, giving is something like this:
 560                 //
 561                 //     error: use of moved value: `x`
 562                 //     note: `x` moved here (through moving `x.a`)...
 563
 564                 let common = moved_lp.common(lp);
 565                 let has_common = common.is_some();
 566                 let has_fork = moved_lp.has_fork(lp);
 567                 let (nl, ol, moved_lp_msg) =
 568                     if has_fork && has_common {
 569                         let nl = self.loan_path_to_string(&common.unwrap());
 570                         let ol = nl.clone();
 571                         let moved_lp_msg = format!(" (through moving `{}`)",
 572                                                    self.loan_path_to_string(moved_lp));
 573                         (nl, ol, moved_lp_msg)
 574                     } else {
 575                         (self.loan_path_to_string(lp),
 576                          self.loan_path_to_string(moved_lp),
 577                          String::new())
 578                     };
 579
 580                 let partial = moved_lp.depth() > lp.depth();
 581                 let msg = if !has_fork && partial { "partially " }
 582                           else if has_fork && !has_common { "collaterally "}
 583                           else { "" };
 584                 let mut err = struct_span_err!(
 585                     self.tcx.sess, use_span, E0382,
 586                     "{} of {}moved value: `{}`",
 587                     verb, msg, nl);
 588                 let need_note = match lp.ty.sty {
 589                     ty::TypeVariants::TyClosure(id, _) => {
 590                         if let Ok(ty::ClosureKind::FnOnce) =
 591                            ty::queries::closure_kind::try_get(self.tcx, DUMMY_SP, id) {
 592                             err.help("closure was moved because it only implements `FnOnce`");
 593                             false
 594                         } else {
 595                             true
 596                         }
 597                     }
 598                     _ => true,
 599                 };
 600                 (ol, moved_lp_msg, err, need_note)
 601             }
 602         };
 603
 604         // Get type of value and span where it was previously
 605         // moved.
 606         let (move_span, move_note) = match the_move.kind {
 607             move_data::Declared => {
 608                 unreachable!();
 609             }
 610
 611             move_data::MoveExpr |
 612             move_data::MovePat =>
 613                 (self.tcx.hir.span(the_move.id), ""),
 614
 615             move_data::Captured =>
 616                 (match self.tcx.hir.expect_expr(the_move.id).node {
 617                     hir::ExprClosure(.., fn_decl_span) => fn_decl_span,
 618                     ref r => bug!("Captured({}) maps to non-closure: {:?}",
 619                                   the_move.id, r),
 620                 }, " (into closure)"),
 621         };
 622
 623         // Annotate the use and the move in the span. Watch out for
 624         // the case where the use and the move are the same. This
 625         // means the use is in a loop.
 626         err = if use_span == move_span {
 627             err.span_label(
 628                 use_span,
 629                 format!("value moved{} here in previous iteration of loop",
 630                          move_note));
 631             err
 632         } else {
 633             err.span_label(use_span, format!("value {} here after move", verb_participle))
 634                .span_label(move_span, format!("value moved{} here", move_note));
 635             err
 636         };
 637
 638         if need_note {
 639             err.note(&format!("move occurs because `{}` has type `{}`, \
 640                                which does not implement the `Copy` trait",
 641                               self.loan_path_to_string(moved_lp),
 642                               moved_lp.ty));
 643         }
 644
 645         // Note: we used to suggest adding a `ref binding` or calling
 646         // `clone` but those suggestions have been removed because
 647         // they are often not what you actually want to do, and were
 648         // not considered particularly helpful.
 649
 650         err.emit();
 651     }
 652
 653     pub fn report_partial_reinitialization_of_uninitialized_structure(
 654             &self,
 655             span: Span,
 656             lp: &LoanPath<'tcx>) {
 657         span_err!(
 658             self.tcx.sess, span, E0383,
 659             "partial reinitialization of uninitialized structure `{}`",
 660             self.loan_path_to_string(lp));
 661     }
 662
 663     pub fn report_reassigned_immutable_variable(&self,
 664                                                 span: Span,
 665                                                 lp: &LoanPath<'tcx>,
 666                                                 assign:
 667                                                 &move_data::Assignment) {
 668         let mut err = struct_span_err!(
 669             self.tcx.sess, span, E0384,
 670             "re-assignment of immutable variable `{}`",
 671             self.loan_path_to_string(lp));
 672         err.span_label(span, "re-assignment of immutable variable");
 673         if span != assign.span {
 674             err.span_label(assign.span, format!("first assignment to `{}`",
 675                                               self.loan_path_to_string(lp)));
 676         }
 677         err.emit();
 678     }
 679
 680     pub fn span_err(&self, s: Span, m: &str) {
 681         self.tcx.sess.span_err(s, m);
 682     }
 683
 684     pub fn struct_span_err<S: Into<MultiSpan>>(&self, s: S, m: &str)
 685                                               -> DiagnosticBuilder<'a> {
 686         self.tcx.sess.struct_span_err(s, m)
 687     }
 688
 689     pub fn struct_span_err_with_code<S: Into<MultiSpan>>(&self,
 690                                                          s: S,
 691                                                          msg: &str,
 692                                                          code: &str)
 693                                                          -> DiagnosticBuilder<'a> {
 694         self.tcx.sess.struct_span_err_with_code(s, msg, code)
 695     }
 696
 697     pub fn span_err_with_code<S: Into<MultiSpan>>(&self, s: S, msg: &str, code: &str) {
 698         self.tcx.sess.span_err_with_code(s, msg, code);
 699     }
 700
 701     fn bckerr_to_diag(&self, err: &BckError<'tcx>) -> DiagnosticBuilder<'a> {
 702         let span = err.span.clone();
 703
 704         match err.code {
 705             err_mutbl => {
 706                 let descr = match err.cmt.note {
 707                     mc::NoteClosureEnv(_) | mc::NoteUpvarRef(_) => {
 708                         self.cmt_to_string(&err.cmt)
 709                     }
 710                     _ => match opt_loan_path(&err.cmt) {
 711                         None => {
 712                             format!("{} {}",
 713                                     err.cmt.mutbl.to_user_str(),
 714                                     self.cmt_to_string(&err.cmt))
 715
 716                         }
 717                         Some(lp) => {
 718                             format!("{} {} `{}`",
 719                                     err.cmt.mutbl.to_user_str(),
 720                                     self.cmt_to_string(&err.cmt),
 721                                     self.loan_path_to_string(&lp))
 722                         }
 723                     }
 724                 };
 725
 726                 match err.cause {
 727                     MutabilityViolation => {
 728                         struct_span_err!(self.tcx.sess, span, E0594, "cannot assign to {}", descr)
 729                     }
 730                     BorrowViolation(euv::ClosureCapture(_)) => {
 731                         struct_span_err!(self.tcx.sess, span, E0595,
 732                                          "closure cannot assign to {}", descr)
 733                     }
 734                     BorrowViolation(euv::OverloadedOperator) |
 735                     BorrowViolation(euv::AddrOf) |
 736                     BorrowViolation(euv::RefBinding) |
 737                     BorrowViolation(euv::AutoRef) |
 738                     BorrowViolation(euv::AutoUnsafe) |
 739                     BorrowViolation(euv::ForLoop) |
 740                     BorrowViolation(euv::MatchDiscriminant) => {
 741                         struct_span_err!(self.tcx.sess, span, E0596,
 742                                          "cannot borrow {} as mutable", descr)
 743                     }
 744                     BorrowViolation(euv::ClosureInvocation) => {
 745                         span_bug!(err.span,
 746                             "err_mutbl with a closure invocation");
 747                     }
 748                 }
 749             }
 750             err_out_of_scope(..) => {
 751                 let msg = match opt_loan_path(&err.cmt) {
 752                     None => "borrowed value".to_string(),
 753                     Some(lp) => {
 754                         format!("`{}`", self.loan_path_to_string(&lp))
 755                     }
 756                 };
 757                 struct_span_err!(self.tcx.sess, span, E0597, "{} does not live long enough", msg)
 758             }
 759             err_borrowed_pointer_too_short(..) => {
 760                 let descr = self.cmt_to_path_or_string(&err.cmt);
 761                 struct_span_err!(self.tcx.sess, span, E0598,
 762                                  "lifetime of {} is too short to guarantee \
 763                                   its contents can be safely reborrowed",
 764                                  descr)
 765             }
 766         }
 767     }
 768
 769     pub fn report_aliasability_violation(&self,
 770                                          span: Span,
 771                                          kind: AliasableViolationKind,
 772                                          cause: mc::AliasableReason,
 773                                          cmt: mc::cmt<'tcx>) {
 774         let mut is_closure = false;
 775         let prefix = match kind {
 776             MutabilityViolation => {
 777                 "cannot assign to data"
 778             }
 779             BorrowViolation(euv::ClosureCapture(_)) |
 780             BorrowViolation(euv::OverloadedOperator) |
 781             BorrowViolation(euv::AddrOf) |
 782             BorrowViolation(euv::AutoRef) |
 783             BorrowViolation(euv::AutoUnsafe) |
 784             BorrowViolation(euv::RefBinding) |
 785             BorrowViolation(euv::MatchDiscriminant) => {
 786                 "cannot borrow data mutably"
 787             }
 788
 789             BorrowViolation(euv::ClosureInvocation) => {
 790                 is_closure = true;
 791                 "closure invocation"
 792             }
 793
 794             BorrowViolation(euv::ForLoop) => {
 795                 "`for` loop"
 796             }
 797         };
 798
 799         match cause {
 800             mc::AliasableStatic |
 801             mc::AliasableStaticMut => {
 802                 // This path cannot occur. It happens when we have an
 803                 // `&mut` or assignment to a static. But in the case
 804                 // of `static X`, we get a mutability violation first,
 805                 // and never get here. In the case of `static mut X`,
 806                 // that is unsafe and hence the aliasability error is
 807                 // ignored.
 808                 span_bug!(span, "aliasability violation for static `{}`", prefix)
 809             }
 810             mc::AliasableBorrowed => {}
 811         };
 812         let blame = cmt.immutability_blame();
 813         let mut err = match blame {
 814             Some(ImmutabilityBlame::ClosureEnv(id)) => {
 815                 let mut err = struct_span_err!(
 816                     self.tcx.sess, span, E0387,
 817                     "{} in a captured outer variable in an `Fn` closure", prefix);
 818
 819                 // FIXME: the distinction between these 2 messages looks wrong.
 820                 let help = if let BorrowViolation(euv::ClosureCapture(_)) = kind {
 821                     // The aliasability violation with closure captures can
 822                     // happen for nested closures, so we know the enclosing
 823                     // closure incorrectly accepts an `Fn` while it needs to
 824                     // be `FnMut`.
 825                     "consider changing this to accept closures that implement `FnMut`"
 826
 827                 } else {
 828                     "consider changing this closure to take self by mutable reference"
 829                 };
 830                 err.span_help(self.tcx.hir.span(id), help);
 831                 err
 832             }
 833             _ =>  {
 834                 let mut err = struct_span_err!(
 835                     self.tcx.sess, span, E0389,
 836                     "{} in a `&` reference", prefix);
 837                 err.span_label(span, "assignment into an immutable reference");
 838                 err
 839             }
 840         };
 841         self.note_immutability_blame(&mut err, blame);
 842
 843         if is_closure {
 844             err.help("closures behind references must be called via `&mut`");
 845         }
 846         err.emit();
 847     }
 848
 849     /// Given a type, if it is an immutable reference, return a suggestion to make it mutable
 850     fn suggest_mut_for_immutable(&self, pty: &hir::Ty, is_implicit_self: bool) -> Option<String> {
 851         // Check wether the argument is an immutable reference
 852         debug!("suggest_mut_for_immutable({:?}, {:?})", pty, is_implicit_self);
 853         if let hir::TyRptr(lifetime, hir::MutTy {
 854             mutbl: hir::Mutability::MutImmutable,
 855             ref ty
 856         }) = pty.node {
 857             // Account for existing lifetimes when generating the message
 858             let pointee_snippet = match self.tcx.sess.codemap().span_to_snippet(ty.span) {
 859                 Ok(snippet) => snippet,
 860                 _ => return None
 861             };
 862
 863             let lifetime_snippet = if !lifetime.is_elided() {
 864                 format!("{} ", match self.tcx.sess.codemap().span_to_snippet(lifetime.span) {
 865                     Ok(lifetime_snippet) => lifetime_snippet,
 866                     _ => return None
 867                 })
 868             } else {
 869                 String::new()
 870             };
 871             Some(format!("use `&{}mut {}` here to make mutable",
 872                          lifetime_snippet,
 873                          if is_implicit_self { "self" } else { &*pointee_snippet }))
 874         } else {
 875             None
 876         }
 877     }
 878
 879     fn local_binding_mode(&self, node_id: ast::NodeId) -> hir::BindingMode {
 880         let pat = match self.tcx.hir.get(node_id) {
 881             hir_map::Node::NodeLocal(pat) => pat,
 882             node => bug!("bad node for local: {:?}", node)
 883         };
 884
 885         match pat.node {
 886             hir::PatKind::Binding(mode, ..) => mode,
 887             _ => bug!("local is not a binding: {:?}", pat)
 888         }
 889     }
 890
 891     fn local_ty(&self, node_id: ast::NodeId) -> (Option<&hir::Ty>, bool) {
 892         let parent = self.tcx.hir.get_parent_node(node_id);
 893         let parent_node = self.tcx.hir.get(parent);
 894
 895         // The parent node is like a fn
 896         if let Some(fn_like) = FnLikeNode::from_node(parent_node) {
 897             // `nid`'s parent's `Body`
 898             let fn_body = self.tcx.hir.body(fn_like.body());
 899             // Get the position of `node_id` in the arguments list
 900             let arg_pos = fn_body.arguments.iter().position(|arg| arg.pat.id == node_id);
 901             if let Some(i) = arg_pos {
 902                 // The argument's `Ty`
 903                 (Some(&fn_like.decl().inputs[i]),
 904                  i == 0 && fn_like.decl().has_implicit_self)
 905             } else {
 906                 (None, false)
 907             }
 908         } else {
 909             (None, false)
 910         }
 911     }
 912
 913     fn note_immutability_blame(&self,
 914                                db: &mut DiagnosticBuilder,
 915                                blame: Option<ImmutabilityBlame>) {
 916         match blame {
 917             None => {}
 918             Some(ImmutabilityBlame::ClosureEnv(_)) => {}
 919             Some(ImmutabilityBlame::ImmLocal(node_id)) => {
 920                 let let_span = self.tcx.hir.span(node_id);
 921                 if let hir::BindingMode::BindByValue(..) = self.local_binding_mode(node_id) {
 922                     if let Ok(snippet) = self.tcx.sess.codemap().span_to_snippet(let_span) {
 923                         let (_, is_implicit_self) = self.local_ty(node_id);
 924                         if is_implicit_self && snippet != "self" {
 925                             // avoid suggesting `mut &self`.
 926                             return
 927                         }
 928                         db.span_label(
 929                             let_span,
 930                             format!("consider changing this to `mut {}`", snippet)
 931                         );
 932                     }
 933                 }
 934             }
 935             Some(ImmutabilityBlame::LocalDeref(node_id)) => {
 936                 let let_span = self.tcx.hir.span(node_id);
 937                 match self.local_binding_mode(node_id) {
 938                     hir::BindingMode::BindByRef(..) => {
 939                         let snippet = self.tcx.sess.codemap().span_to_snippet(let_span);
 940                         if let Ok(snippet) = snippet {
 941                             db.span_label(
 942                                 let_span,
 943                                 format!("consider changing this to `{}`",
 944                                          snippet.replace("ref ", "ref mut "))
 945                             );
 946                         }
 947                     }
 948                     hir::BindingMode::BindByValue(..) => {
 949                         if let (Some(local_ty), is_implicit_self) = self.local_ty(node_id) {
 950                             if let Some(msg) =
 951                                  self.suggest_mut_for_immutable(local_ty, is_implicit_self) {
 952                                 db.span_label(local_ty.span, msg);
 953                             }
 954                         }
 955                     }
 956                 }
 957             }
 958             Some(ImmutabilityBlame::AdtFieldDeref(_, field)) => {
 959                 let node_id = match self.tcx.hir.as_local_node_id(field.did) {
 960                     Some(node_id) => node_id,
 961                     None => return
 962                 };
 963
 964                 if let hir_map::Node::NodeField(ref field) = self.tcx.hir.get(node_id) {
 965                     if let Some(msg) = self.suggest_mut_for_immutable(&field.ty, false) {
 966                         db.span_label(field.ty.span, msg);
 967                     }
 968                 }
 969             }
 970         }
 971     }
 972
 973     fn report_out_of_scope_escaping_closure_capture(&self,
 974                                                     err: &BckError<'tcx>,
 975                                                     capture_span: Span)
 976     {
 977         let cmt_path_or_string = self.cmt_to_path_or_string(&err.cmt);
 978
 979         let suggestion =
 980             match self.tcx.sess.codemap().span_to_snippet(err.span) {
 981                 Ok(string) => format!("move {}", string),
 982                 Err(_) => format!("move |<args>| <body>")
 983             };
 984
 985         struct_span_err!(self.tcx.sess, err.span, E0373,
 986                          "closure may outlive the current function, \
 987                           but it borrows {}, \
 988                           which is owned by the current function",
 989                          cmt_path_or_string)
 990             .span_label(capture_span,
 991                        format!("{} is borrowed here",
 992                                 cmt_path_or_string))
 993             .span_label(err.span,
 994                        format!("may outlive borrowed value {}",
 995                                 cmt_path_or_string))
 996             .span_suggestion(err.span,
 997                              &format!("to force the closure to take ownership of {} \
 998                                        (and any other referenced variables), \
 999                                        use the `move` keyword, as shown:",
1000                                        cmt_path_or_string),
1001                              suggestion)
1002             .emit();
1003     }
1004
1005     fn region_end_span(&self, region: ty::Region<'tcx>) -> Option<Span> {
1006         match *region {
1007             ty::ReScope(scope) => {
1008                 match scope.span(&self.tcx.hir) {
1009                     Some(s) => {
1010                         Some(s.end_point())
1011                     }
1012                     None => {
1013                         None
1014                     }
1015                 }
1016             }
1017             _ => None
1018         }
1019     }
1020
1021     fn note_and_explain_bckerr(&self, db: &mut DiagnosticBuilder, err: BckError<'tcx>) {
1022         let error_span = err.span.clone();
1023         match err.code {
1024             err_mutbl => {
1025                 self.note_and_explain_mutbl_error(db, &err, &error_span);
1026                 self.note_immutability_blame(db, err.cmt.immutability_blame());
1027             }
1028             err_out_of_scope(super_scope, sub_scope, cause) => {
1029                 let (value_kind, value_msg) = match err.cmt.cat {
1030                     mc::Categorization::Rvalue(..) =>
1031                         ("temporary value", "temporary value created here"),
1032                     _ =>
1033                         ("borrowed value", "borrow occurs here")
1034                 };
1035
1036                 let is_closure = match cause {
1037                     euv::ClosureCapture(s) => {
1038                         // The primary span starts out as the closure creation point.
1039                         // Change the primary span here to highlight the use of the variable
1040                         // in the closure, because it seems more natural. Highlight
1041                         // closure creation point as a secondary span.
1042                         match db.span.primary_span() {
1043                             Some(primary) => {
1044                                 db.span = MultiSpan::from_span(s);
1045                                 db.span_label(primary, "capture occurs here");
1046                                 db.span_label(s, "does not live long enough");
1047                                 true
1048                             }
1049                             None => false
1050                         }
1051                     }
1052                     _ => {
1053                         db.span_label(error_span, "does not live long enough");
1054                         false
1055                     }
1056                 };
1057
1058                 let sub_span = self.region_end_span(sub_scope);
1059                 let super_span = self.region_end_span(super_scope);
1060
1061                 match (sub_span, super_span) {
1062                     (Some(s1), Some(s2)) if s1 == s2 => {
1063                         if !is_closure {
1064                             db.span = MultiSpan::from_span(s1);
1065                             db.span_label(error_span, value_msg);
1066                             let msg = match opt_loan_path(&err.cmt) {
1067                                 None => value_kind.to_string(),
1068                                 Some(lp) => {
1069                                     format!("`{}`", self.loan_path_to_string(&lp))
1070                                 }
1071                             };
1072                             db.span_label(s1,
1073                                           format!("{} dropped here while still borrowed", msg));
1074                         } else {
1075                             db.span_label(s1, format!("{} dropped before borrower", value_kind));
1076                         }
1077                         db.note("values in a scope are dropped in the opposite order \
1078                                 they are created");
1079                     }
1080                     (Some(s1), Some(s2)) if !is_closure => {
1081                         db.span = MultiSpan::from_span(s2);
1082                         db.span_label(error_span, value_msg);
1083                         let msg = match opt_loan_path(&err.cmt) {
1084                             None => value_kind.to_string(),
1085                             Some(lp) => {
1086                                 format!("`{}`", self.loan_path_to_string(&lp))
1087                             }
1088                         };
1089                         db.span_label(s2, format!("{} dropped here while still borrowed", msg));
1090                         db.span_label(s1, format!("{} needs to live until here", value_kind));
1091                     }
1092                     _ => {
1093                         match sub_span {
1094                             Some(s) => {
1095                                 db.span_label(s, format!("{} needs to live until here",
1096                                                           value_kind));
1097                             }
1098                             None => {
1099                                 self.tcx.note_and_explain_region(
1100                                     db,
1101                                     "borrowed value must be valid for ",
1102                                     sub_scope,
1103                                     "...");
1104                             }
1105                         }
1106                         match super_span {
1107                             Some(s) => {
1108                                 db.span_label(s, format!("{} only lives until here", value_kind));
1109                             }
1110                             None => {
1111                                 self.tcx.note_and_explain_region(
1112                                     db,
1113                                     "...but borrowed value is only valid for ",
1114                                     super_scope,
1115                                     "");
1116                             }
1117                         }
1118                     }
1119                 }
1120
1121                 if let Some(_) = statement_scope_span(self.tcx, super_scope) {
1122                     db.note("consider using a `let` binding to increase its lifetime");
1123                 }
1124
1125
1126
1127                 match err.cmt.cat {
1128                     mc::Categorization::Rvalue(r, or) if r != or => {
1129                         db.note("\
1130 before rustc 1.16, this temporary lived longer - see issue #39283 \
1131 (https://github.com/rust-lang/rust/issues/39283)");
1132                     }
1133                     _ => {}
1134                 }
1135             }
1136
1137             err_borrowed_pointer_too_short(loan_scope, ptr_scope) => {
1138                 let descr = match opt_loan_path(&err.cmt) {
1139                     Some(lp) => {
1140                         format!("`{}`", self.loan_path_to_string(&lp))
1141                     }
1142                     None => self.cmt_to_string(&err.cmt),
1143                 };
1144                 self.tcx.note_and_explain_region(
1145                     db,
1146                     &format!("{} would have to be valid for ",
1147                             descr),
1148                     loan_scope,
1149                     "...");
1150                 self.tcx.note_and_explain_region(
1151                     db,
1152                     &format!("...but {} is only valid for ", descr),
1153                     ptr_scope,
1154                     "");
1155             }
1156         }
1157     }
1158
1159     fn note_and_explain_mutbl_error(&self, db: &mut DiagnosticBuilder, err: &BckError<'tcx>,
1160                                     error_span: &Span) {
1161         match err.cmt.note {
1162             mc::NoteClosureEnv(upvar_id) | mc::NoteUpvarRef(upvar_id) => {
1163                 // If this is an `Fn` closure, it simply can't mutate upvars.
1164                 // If it's an `FnMut` closure, the original variable was declared immutable.
1165                 // We need to determine which is the case here.
1166                 let kind = match err.cmt.upvar().unwrap().cat {
1167                     Categorization::Upvar(mc::Upvar { kind, .. }) => kind,
1168                     _ => bug!()
1169                 };
1170                 if kind == ty::ClosureKind::Fn {
1171                     db.span_help(self.tcx.hir.span(upvar_id.closure_expr_id),
1172                                  "consider changing this closure to take \
1173                                   self by mutable reference");
1174                 }
1175             }
1176             _ => {
1177                 if let Categorization::Deref(..) = err.cmt.cat {
1178                     db.span_label(*error_span, "cannot borrow as mutable");
1179                 } else if let Categorization::Local(local_id) = err.cmt.cat {
1180                     let span = self.tcx.hir.span(local_id);
1181                     if let Ok(snippet) = self.tcx.sess.codemap().span_to_snippet(span) {
1182                         if snippet.starts_with("ref mut ") || snippet.starts_with("&mut ") {
1183                             db.span_label(*error_span, "cannot reborrow mutably");
1184                             db.span_label(*error_span, "try removing `&mut` here");
1185                         } else {
1186                             db.span_label(*error_span, "cannot borrow mutably");
1187                         }
1188                     } else {
1189                         db.span_label(*error_span, "cannot borrow mutably");
1190                     }
1191                 } else if let Categorization::Interior(ref cmt, _) = err.cmt.cat {
1192                     if let mc::MutabilityCategory::McImmutable = cmt.mutbl {
1193                         db.span_label(*error_span,
1194                                       "cannot mutably borrow immutable field");
1195                     }
1196                 }
1197             }
1198         }
1199     }
1200     pub fn append_loan_path_to_string(&self,
1201                                       loan_path: &LoanPath<'tcx>,
1202                                       out: &mut String) {
1203         match loan_path.kind {
1204             LpUpvar(ty::UpvarId{ var_id: id, closure_expr_id: _ }) |
1205             LpVar(id) => {
1206                 out.push_str(&self.tcx.local_var_name_str(id));
1207             }
1208
1209             LpDowncast(ref lp_base, variant_def_id) => {
1210                 out.push('(');
1211                 self.append_loan_path_to_string(&lp_base, out);
1212                 out.push_str(DOWNCAST_PRINTED_OPERATOR);
1213                 out.push_str(&self.tcx.item_path_str(variant_def_id));
1214                 out.push(')');
1215             }
1216
1217             LpExtend(ref lp_base, _, LpInterior(_, InteriorField(fname))) => {
1218                 self.append_autoderefd_loan_path_to_string(&lp_base, out);
1219                 match fname {
1220                     mc::NamedField(fname) => {
1221                         out.push('.');
1222                         out.push_str(&fname.as_str());
1223                     }
1224                     mc::PositionalField(idx) => {
1225                         out.push('.');
1226                         out.push_str(&idx.to_string());
1227                     }
1228                 }
1229             }
1230
1231             LpExtend(ref lp_base, _, LpInterior(_, InteriorElement(..))) => {
1232                 self.append_autoderefd_loan_path_to_string(&lp_base, out);
1233                 out.push_str("[..]");
1234             }
1235
1236             LpExtend(ref lp_base, _, LpDeref(_)) => {
1237                 out.push('*');
1238                 self.append_loan_path_to_string(&lp_base, out);
1239             }
1240         }
1241     }
1242
1243     pub fn append_autoderefd_loan_path_to_string(&self,
1244                                                  loan_path: &LoanPath<'tcx>,
1245                                                  out: &mut String) {
1246         match loan_path.kind {
1247             LpExtend(ref lp_base, _, LpDeref(_)) => {
1248                 // For a path like `(*x).f` or `(*x)[3]`, autoderef
1249                 // rules would normally allow users to omit the `*x`.
1250                 // So just serialize such paths to `x.f` or x[3]` respectively.
1251                 self.append_autoderefd_loan_path_to_string(&lp_base, out)
1252             }
1253
1254             LpDowncast(ref lp_base, variant_def_id) => {
1255                 out.push('(');
1256                 self.append_autoderefd_loan_path_to_string(&lp_base, out);
1257                 out.push(':');
1258                 out.push_str(&self.tcx.item_path_str(variant_def_id));
1259                 out.push(')');
1260             }
1261
1262             LpVar(..) | LpUpvar(..) | LpExtend(.., LpInterior(..)) => {
1263                 self.append_loan_path_to_string(loan_path, out)
1264             }
1265         }
1266     }
1267
1268     pub fn loan_path_to_string(&self, loan_path: &LoanPath<'tcx>) -> String {
1269         let mut result = String::new();
1270         self.append_loan_path_to_string(loan_path, &mut result);
1271         result
1272     }
1273
1274     pub fn cmt_to_string(&self, cmt: &mc::cmt_<'tcx>) -> String {
1275         cmt.descriptive_string(self.tcx)
1276     }
1277
1278     pub fn cmt_to_path_or_string(&self, cmt: &mc::cmt<'tcx>) -> String {
1279         match opt_loan_path(cmt) {
1280             Some(lp) => format!("`{}`", self.loan_path_to_string(&lp)),
1281             None => self.cmt_to_string(cmt),
1282         }
1283     }
1284 }
1285
1286 fn statement_scope_span(tcx: TyCtxt, region: ty::Region) -> Option<Span> {
1287     match *region {
1288         ty::ReScope(scope) => {
1289             match tcx.hir.find(scope.node_id()) {
1290                 Some(hir_map::NodeStmt(stmt)) => Some(stmt.span),
1291                 _ => None
1292             }
1293         }
1294         _ => None
1295     }
1296 }
1297
1298 impl BitwiseOperator for LoanDataFlowOperator {
1299     #[inline]
1300     fn join(&self, succ: usize, pred: usize) -> usize {
1301         succ | pred // loans from both preds are in scope
1302     }
1303 }
1304
1305 impl DataFlowOperator for LoanDataFlowOperator {
1306     #[inline]
1307     fn initial_value(&self) -> bool {
1308         false // no loans in scope by default
1309     }
1310 }
1311
1312 impl<'tcx> fmt::Debug for InteriorKind {
1313     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1314         match *self {
1315             InteriorField(mc::NamedField(fld)) => write!(f, "{}", fld),
1316             InteriorField(mc::PositionalField(i)) => write!(f, "#{}", i),
1317             InteriorElement(..) => write!(f, "[]"),
1318         }
1319     }
1320 }
1321
1322 impl<'tcx> fmt::Debug for Loan<'tcx> {
1323     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1324         write!(f, "Loan_{}({:?}, {:?}, {:?}-{:?}, {:?})",
1325                self.index,
1326                self.loan_path,
1327                self.kind,
1328                self.gen_scope,
1329                self.kill_scope,
1330                self.restricted_paths)
1331     }
1332 }
1333
1334 impl<'tcx> fmt::Debug for LoanPath<'tcx> {
1335     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1336         match self.kind {
1337             LpVar(id) => {
1338                 write!(f, "$({})", ty::tls::with(|tcx| tcx.hir.node_to_string(id)))
1339             }
1340
1341             LpUpvar(ty::UpvarId{ var_id, closure_expr_id }) => {
1342                 let s = ty::tls::with(|tcx| tcx.hir.node_to_string(var_id));
1343                 write!(f, "$({} captured by id={})", s, closure_expr_id)
1344             }
1345
1346             LpDowncast(ref lp, variant_def_id) => {
1347                 let variant_str = if variant_def_id.is_local() {
1348                     ty::tls::with(|tcx| tcx.item_path_str(variant_def_id))
1349                 } else {
1350                     format!("{:?}", variant_def_id)
1351                 };
1352                 write!(f, "({:?}{}{})", lp, DOWNCAST_PRINTED_OPERATOR, variant_str)
1353             }
1354
1355             LpExtend(ref lp, _, LpDeref(_)) => {
1356                 write!(f, "{:?}.*", lp)
1357             }
1358
1359             LpExtend(ref lp, _, LpInterior(_, ref interior)) => {
1360                 write!(f, "{:?}.{:?}", lp, interior)
1361             }
1362         }
1363     }
1364 }
1365
1366 impl<'tcx> fmt::Display for LoanPath<'tcx> {
1367     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1368         match self.kind {
1369             LpVar(id) => {
1370                 write!(f, "$({})", ty::tls::with(|tcx| tcx.hir.node_to_user_string(id)))
1371             }
1372
1373             LpUpvar(ty::UpvarId{ var_id, closure_expr_id: _ }) => {
1374                 let s = ty::tls::with(|tcx| tcx.hir.node_to_user_string(var_id));
1375                 write!(f, "$({} captured by closure)", s)
1376             }
1377
1378             LpDowncast(ref lp, variant_def_id) => {
1379                 let variant_str = if variant_def_id.is_local() {
1380                     ty::tls::with(|tcx| tcx.item_path_str(variant_def_id))
1381                 } else {
1382                     format!("{:?}", variant_def_id)
1383                 };
1384                 write!(f, "({}{}{})", lp, DOWNCAST_PRINTED_OPERATOR, variant_str)
1385             }
1386
1387             LpExtend(ref lp, _, LpDeref(_)) => {
1388                 write!(f, "{}.*", lp)
1389             }
1390
1391             LpExtend(ref lp, _, LpInterior(_, ref interior)) => {
1392                 write!(f, "{}.{:?}", lp, interior)
1393             }
1394         }
1395     }
1396 }