src/librustc_typeck/check/upvar.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 //! ### Inferring borrow kinds for upvars
  12 //!
  13 //! Whenever there is a closure expression, we need to determine how each
  14 //! upvar is used. We do this by initially assigning each upvar an
  15 //! immutable "borrow kind" (see `ty::BorrowKind` for details) and then
  16 //! "escalating" the kind as needed. The borrow kind proceeds according to
  17 //! the following lattice:
  18 //!
  19 //!     ty::ImmBorrow -> ty::UniqueImmBorrow -> ty::MutBorrow
  20 //!
  21 //! So, for example, if we see an assignment `x = 5` to an upvar `x`, we
  22 //! will promote its borrow kind to mutable borrow. If we see an `&mut x`
  23 //! we'll do the same. Naturally, this applies not just to the upvar, but
  24 //! to everything owned by `x`, so the result is the same for something
  25 //! like `x.f = 5` and so on (presuming `x` is not a borrowed pointer to a
  26 //! struct). These adjustments are performed in
  27 //! `adjust_upvar_borrow_kind()` (you can trace backwards through the code
  28 //! from there).
  29 //!
  30 //! The fact that we are inferring borrow kinds as we go results in a
  31 //! semi-hacky interaction with mem-categorization. In particular,
  32 //! mem-categorization will query the current borrow kind as it
  33 //! categorizes, and we'll return the *current* value, but this may get
  34 //! adjusted later. Therefore, in this module, we generally ignore the
  35 //! borrow kind (and derived mutabilities) that are returned from
  36 //! mem-categorization, since they may be inaccurate. (Another option
  37 //! would be to use a unification scheme, where instead of returning a
  38 //! concrete borrow kind like `ty::ImmBorrow`, we return a
  39 //! `ty::InferBorrow(upvar_id)` or something like that, but this would
  40 //! then mean that all later passes would have to check for these figments
  41 //! and report an error, and it just seems like more mess in the end.)
  42
  43 use super::FnCtxt;
  44
  45 use middle::expr_use_visitor as euv;
  46 use middle::mem_categorization as mc;
  47 use middle::mem_categorization::Categorization;
  48 use rustc::ty::{self, Ty};
  49 use rustc::infer::UpvarRegion;
  50 use syntax::ast;
  51 use syntax_pos::Span;
  52 use rustc::hir;
  53 use rustc::hir::intravisit::{self, Visitor, NestedVisitorMap};
  54 use rustc::util::nodemap::NodeMap;
  55
  56 ///////////////////////////////////////////////////////////////////////////
  57 // PUBLIC ENTRY POINTS
  58
  59 impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
  60     pub fn closure_analyze(&self, body: &'gcx hir::Body) {
  61         let mut seed = SeedBorrowKind::new(self);
  62         seed.visit_body(body);
  63
  64         let mut adjust = AdjustBorrowKind::new(self, seed.temp_closure_kinds);
  65         adjust.visit_body(body);
  66
  67         // it's our job to process these.
  68         assert!(self.deferred_call_resolutions.borrow().is_empty());
  69     }
  70 }
  71
  72 ///////////////////////////////////////////////////////////////////////////
  73 // SEED BORROW KIND
  74
  75 struct SeedBorrowKind<'a, 'gcx: 'a+'tcx, 'tcx: 'a> {
  76     fcx: &'a FnCtxt<'a, 'gcx, 'tcx>,
  77     temp_closure_kinds: NodeMap<(ty::ClosureKind, Option<(Span, ast::Name)>)>,
  78 }
  79
  80 impl<'a, 'gcx, 'tcx> Visitor<'gcx> for SeedBorrowKind<'a, 'gcx, 'tcx> {
  81     fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'gcx> {
  82         NestedVisitorMap::None
  83     }
  84
  85     fn visit_expr(&mut self, expr: &'gcx hir::Expr) {
  86         match expr.node {
  87             hir::ExprClosure(cc, _, body_id, _) => {
  88                 let body = self.fcx.tcx.hir.body(body_id);
  89                 self.visit_body(body);
  90                 self.check_closure(expr, cc);
  91             }
  92
  93             _ => { }
  94         }
  95
  96         intravisit::walk_expr(self, expr);
  97     }
  98 }
  99
 100 impl<'a, 'gcx, 'tcx> SeedBorrowKind<'a, 'gcx, 'tcx> {
 101     fn new(fcx: &'a FnCtxt<'a, 'gcx, 'tcx>) -> SeedBorrowKind<'a, 'gcx, 'tcx> {
 102         SeedBorrowKind { fcx: fcx, temp_closure_kinds: NodeMap() }
 103     }
 104
 105     fn check_closure(&mut self,
 106                      expr: &hir::Expr,
 107                      capture_clause: hir::CaptureClause)
 108     {
 109         if !self.fcx.tables.borrow().closure_kinds.contains_key(&expr.id) {
 110             self.temp_closure_kinds.insert(expr.id, (ty::ClosureKind::Fn, None));
 111             debug!("check_closure: adding closure {:?} as Fn", expr.id);
 112         }
 113
 114         self.fcx.tcx.with_freevars(expr.id, |freevars| {
 115             for freevar in freevars {
 116                 let def_id = freevar.def.def_id();
 117                 let var_node_id = self.fcx.tcx.hir.as_local_node_id(def_id).unwrap();
 118                 let upvar_id = ty::UpvarId { var_id: var_node_id,
 119                                              closure_expr_id: expr.id };
 120                 debug!("seed upvar_id {:?}", upvar_id);
 121
 122                 let capture_kind = match capture_clause {
 123                     hir::CaptureByValue => {
 124                         ty::UpvarCapture::ByValue
 125                     }
 126                     hir::CaptureByRef => {
 127                         let origin = UpvarRegion(upvar_id, expr.span);
 128                         let freevar_region = self.fcx.next_region_var(origin);
 129                         let upvar_borrow = ty::UpvarBorrow { kind: ty::ImmBorrow,
 130                                                              region: freevar_region };
 131                         ty::UpvarCapture::ByRef(upvar_borrow)
 132                     }
 133                 };
 134
 135                 self.fcx.tables.borrow_mut().upvar_capture_map.insert(upvar_id, capture_kind);
 136             }
 137         });
 138     }
 139 }
 140
 141 ///////////////////////////////////////////////////////////////////////////
 142 // ADJUST BORROW KIND
 143
 144 struct AdjustBorrowKind<'a, 'gcx: 'a+'tcx, 'tcx: 'a> {
 145     fcx: &'a FnCtxt<'a, 'gcx, 'tcx>,
 146     temp_closure_kinds: NodeMap<(ty::ClosureKind, Option<(Span, ast::Name)>)>,
 147 }
 148
 149 impl<'a, 'gcx, 'tcx> AdjustBorrowKind<'a, 'gcx, 'tcx> {
 150     fn new(fcx: &'a FnCtxt<'a, 'gcx, 'tcx>,
 151            temp_closure_kinds: NodeMap<(ty::ClosureKind, Option<(Span, ast::Name)>)>)
 152            -> AdjustBorrowKind<'a, 'gcx, 'tcx> {
 153         AdjustBorrowKind { fcx: fcx, temp_closure_kinds: temp_closure_kinds }
 154     }
 155
 156     fn analyze_closure(&mut self,
 157                        id: ast::NodeId,
 158                        span: Span,
 159                        body: &hir::Body) {
 160         /*!
 161          * Analysis starting point.
 162          */
 163
 164         debug!("analyze_closure(id={:?}, body.id={:?})", id, body.id());
 165
 166         {
 167             let body_owner_def_id = self.fcx.tcx.hir.body_owner_def_id(body.id());
 168             let region_maps = &self.fcx.tcx.region_maps(body_owner_def_id);
 169             let mut euv =
 170                 euv::ExprUseVisitor::with_options(self,
 171                                                   self.fcx,
 172                                                   region_maps,
 173                                                   mc::MemCategorizationOptions {
 174                                                       during_closure_kind_inference: true
 175                                                   });
 176             euv.consume_body(body);
 177         }
 178
 179         // Now that we've analyzed the closure, we know how each
 180         // variable is borrowed, and we know what traits the closure
 181         // implements (Fn vs FnMut etc). We now have some updates to do
 182         // with that information.
 183         //
 184         // Note that no closure type C may have an upvar of type C
 185         // (though it may reference itself via a trait object). This
 186         // results from the desugaring of closures to a struct like
 187         // `Foo<..., UV0...UVn>`. If one of those upvars referenced
 188         // C, then the type would have infinite size (and the
 189         // inference algorithm will reject it).
 190
 191         // Extract the type variables UV0...UVn.
 192         let (def_id, closure_substs) = match self.fcx.node_ty(id).sty {
 193             ty::TyClosure(def_id, substs) => (def_id, substs),
 194             ref t => {
 195                 span_bug!(
 196                     span,
 197                     "type of closure expr {:?} is not a closure {:?}",
 198                     id, t);
 199             }
 200         };
 201
 202         // Equate the type variables with the actual types.
 203         let final_upvar_tys = self.final_upvar_tys(id);
 204         debug!("analyze_closure: id={:?} closure_substs={:?} final_upvar_tys={:?}",
 205                id, closure_substs, final_upvar_tys);
 206         for (upvar_ty, final_upvar_ty) in
 207             closure_substs.upvar_tys(def_id, self.fcx.tcx).zip(final_upvar_tys)
 208         {
 209             self.fcx.demand_eqtype(span, final_upvar_ty, upvar_ty);
 210         }
 211
 212         // If we are also inferred the closure kind here, update the
 213         // main table and process any deferred resolutions.
 214         if let Some(&(kind, context)) = self.temp_closure_kinds.get(&id) {
 215             self.fcx.tables.borrow_mut().closure_kinds.insert(id, (kind, context));
 216             let closure_def_id = self.fcx.tcx.hir.local_def_id(id);
 217             debug!("closure_kind({:?}) = {:?}", closure_def_id, kind);
 218
 219             let mut deferred_call_resolutions =
 220                 self.fcx.remove_deferred_call_resolutions(closure_def_id);
 221             for deferred_call_resolution in &mut deferred_call_resolutions {
 222                 deferred_call_resolution.resolve(self.fcx);
 223             }
 224         }
 225     }
 226
 227     // Returns a list of `ClosureUpvar`s for each upvar.
 228     fn final_upvar_tys(&mut self, closure_id: ast::NodeId) -> Vec<Ty<'tcx>> {
 229         // Presently an unboxed closure type cannot "escape" out of a
 230         // function, so we will only encounter ones that originated in the
 231         // local crate or were inlined into it along with some function.
 232         // This may change if abstract return types of some sort are
 233         // implemented.
 234         let tcx = self.fcx.tcx;
 235         tcx.with_freevars(closure_id, |freevars| {
 236             freevars.iter().map(|freevar| {
 237                 let def_id = freevar.def.def_id();
 238                 let var_id = tcx.hir.as_local_node_id(def_id).unwrap();
 239                 let freevar_ty = self.fcx.node_ty(var_id);
 240                 let upvar_id = ty::UpvarId {
 241                     var_id: var_id,
 242                     closure_expr_id: closure_id
 243                 };
 244                 let capture = self.fcx.upvar_capture(upvar_id).unwrap();
 245
 246                 debug!("var_id={:?} freevar_ty={:?} capture={:?}",
 247                        var_id, freevar_ty, capture);
 248
 249                 match capture {
 250                     ty::UpvarCapture::ByValue => freevar_ty,
 251                     ty::UpvarCapture::ByRef(borrow) =>
 252                         tcx.mk_ref(borrow.region,
 253                                     ty::TypeAndMut {
 254                                         ty: freevar_ty,
 255                                         mutbl: borrow.kind.to_mutbl_lossy(),
 256                                     }),
 257                 }
 258             }).collect()
 259         })
 260     }
 261
 262     fn adjust_upvar_borrow_kind_for_consume(&mut self,
 263                                             cmt: mc::cmt<'tcx>,
 264                                             mode: euv::ConsumeMode)
 265     {
 266         debug!("adjust_upvar_borrow_kind_for_consume(cmt={:?}, mode={:?})",
 267                cmt, mode);
 268
 269         // we only care about moves
 270         match mode {
 271             euv::Copy => { return; }
 272             euv::Move(_) => { }
 273         }
 274
 275         let tcx = self.fcx.tcx;
 276
 277         // watch out for a move of the deref of a borrowed pointer;
 278         // for that to be legal, the upvar would have to be borrowed
 279         // by value instead
 280         let guarantor = cmt.guarantor();
 281         debug!("adjust_upvar_borrow_kind_for_consume: guarantor={:?}",
 282                guarantor);
 283         match guarantor.cat {
 284             Categorization::Deref(.., mc::BorrowedPtr(..)) |
 285             Categorization::Deref(.., mc::Implicit(..)) => {
 286                 match cmt.note {
 287                     mc::NoteUpvarRef(upvar_id) => {
 288                         debug!("adjust_upvar_borrow_kind_for_consume: \
 289                                 setting upvar_id={:?} to by value",
 290                                upvar_id);
 291
 292                         // to move out of an upvar, this must be a FnOnce closure
 293                         self.adjust_closure_kind(upvar_id.closure_expr_id,
 294                                                  ty::ClosureKind::FnOnce,
 295                                                  guarantor.span,
 296                                                  tcx.hir.name(upvar_id.var_id));
 297
 298                         let upvar_capture_map =
 299                             &mut self.fcx.tables.borrow_mut().upvar_capture_map;
 300                         upvar_capture_map.insert(upvar_id, ty::UpvarCapture::ByValue);
 301                     }
 302                     mc::NoteClosureEnv(upvar_id) => {
 303                         // we get just a closureenv ref if this is a
 304                         // `move` closure, or if the upvar has already
 305                         // been inferred to by-value. In any case, we
 306                         // must still adjust the kind of the closure
 307                         // to be a FnOnce closure to permit moves out
 308                         // of the environment.
 309                         self.adjust_closure_kind(upvar_id.closure_expr_id,
 310                                                  ty::ClosureKind::FnOnce,
 311                                                  guarantor.span,
 312                                                  tcx.hir.name(upvar_id.var_id));
 313                     }
 314                     mc::NoteNone => {
 315                     }
 316                 }
 317             }
 318             _ => { }
 319         }
 320     }
 321
 322     /// Indicates that `cmt` is being directly mutated (e.g., assigned
 323     /// to). If cmt contains any by-ref upvars, this implies that
 324     /// those upvars must be borrowed using an `&mut` borrow.
 325     fn adjust_upvar_borrow_kind_for_mut(&mut self, cmt: mc::cmt<'tcx>) {
 326         debug!("adjust_upvar_borrow_kind_for_mut(cmt={:?})",
 327                cmt);
 328
 329         match cmt.cat.clone() {
 330             Categorization::Deref(base, _, mc::Unique) |
 331             Categorization::Interior(base, _) |
 332             Categorization::Downcast(base, _) => {
 333                 // Interior or owned data is mutable if base is
 334                 // mutable, so iterate to the base.
 335                 self.adjust_upvar_borrow_kind_for_mut(base);
 336             }
 337
 338             Categorization::Deref(base, _, mc::BorrowedPtr(..)) |
 339             Categorization::Deref(base, _, mc::Implicit(..)) => {
 340                 if !self.try_adjust_upvar_deref(cmt, ty::MutBorrow) {
 341                     // assignment to deref of an `&mut`
 342                     // borrowed pointer implies that the
 343                     // pointer itself must be unique, but not
 344                     // necessarily *mutable*
 345                     self.adjust_upvar_borrow_kind_for_unique(base);
 346                 }
 347             }
 348
 349             Categorization::Deref(.., mc::UnsafePtr(..)) |
 350             Categorization::StaticItem |
 351             Categorization::Rvalue(..) |
 352             Categorization::Local(_) |
 353             Categorization::Upvar(..) => {
 354                 return;
 355             }
 356         }
 357     }
 358
 359     fn adjust_upvar_borrow_kind_for_unique(&mut self, cmt: mc::cmt<'tcx>) {
 360         debug!("adjust_upvar_borrow_kind_for_unique(cmt={:?})",
 361                cmt);
 362
 363         match cmt.cat.clone() {
 364             Categorization::Deref(base, _, mc::Unique) |
 365             Categorization::Interior(base, _) |
 366             Categorization::Downcast(base, _) => {
 367                 // Interior or owned data is unique if base is
 368                 // unique.
 369                 self.adjust_upvar_borrow_kind_for_unique(base);
 370             }
 371
 372             Categorization::Deref(base, _, mc::BorrowedPtr(..)) |
 373             Categorization::Deref(base, _, mc::Implicit(..)) => {
 374                 if !self.try_adjust_upvar_deref(cmt, ty::UniqueImmBorrow) {
 375                     // for a borrowed pointer to be unique, its
 376                     // base must be unique
 377                     self.adjust_upvar_borrow_kind_for_unique(base);
 378                 }
 379             }
 380
 381             Categorization::Deref(.., mc::UnsafePtr(..)) |
 382             Categorization::StaticItem |
 383             Categorization::Rvalue(..) |
 384             Categorization::Local(_) |
 385             Categorization::Upvar(..) => {
 386             }
 387         }
 388     }
 389
 390     fn try_adjust_upvar_deref(&mut self,
 391                               cmt: mc::cmt<'tcx>,
 392                               borrow_kind: ty::BorrowKind)
 393                               -> bool
 394     {
 395         assert!(match borrow_kind {
 396             ty::MutBorrow => true,
 397             ty::UniqueImmBorrow => true,
 398
 399             // imm borrows never require adjusting any kinds, so we don't wind up here
 400             ty::ImmBorrow => false,
 401         });
 402
 403         let tcx = self.fcx.tcx;
 404
 405         match cmt.note {
 406             mc::NoteUpvarRef(upvar_id) => {
 407                 // if this is an implicit deref of an
 408                 // upvar, then we need to modify the
 409                 // borrow_kind of the upvar to make sure it
 410                 // is inferred to mutable if necessary
 411                 {
 412                     let upvar_capture_map = &mut self.fcx.tables.borrow_mut().upvar_capture_map;
 413                     let ub = upvar_capture_map.get_mut(&upvar_id).unwrap();
 414                     self.adjust_upvar_borrow_kind(upvar_id, ub, borrow_kind);
 415                 }
 416
 417                 // also need to be in an FnMut closure since this is not an ImmBorrow
 418                 self.adjust_closure_kind(upvar_id.closure_expr_id,
 419                                          ty::ClosureKind::FnMut,
 420                                          cmt.span,
 421                                          tcx.hir.name(upvar_id.var_id));
 422
 423                 true
 424             }
 425             mc::NoteClosureEnv(upvar_id) => {
 426                 // this kind of deref occurs in a `move` closure, or
 427                 // for a by-value upvar; in either case, to mutate an
 428                 // upvar, we need to be an FnMut closure
 429                 self.adjust_closure_kind(upvar_id.closure_expr_id,
 430                                          ty::ClosureKind::FnMut,
 431                                          cmt.span,
 432                                          tcx.hir.name(upvar_id.var_id));
 433
 434                 true
 435             }
 436             mc::NoteNone => {
 437                 false
 438             }
 439         }
 440     }
 441
 442     /// We infer the borrow_kind with which to borrow upvars in a stack closure.
 443     /// The borrow_kind basically follows a lattice of `imm < unique-imm < mut`,
 444     /// moving from left to right as needed (but never right to left).
 445     /// Here the argument `mutbl` is the borrow_kind that is required by
 446     /// some particular use.
 447     fn adjust_upvar_borrow_kind(&mut self,
 448                                 upvar_id: ty::UpvarId,
 449                                 upvar_capture: &mut ty::UpvarCapture,
 450                                 kind: ty::BorrowKind) {
 451         debug!("adjust_upvar_borrow_kind(upvar_id={:?}, upvar_capture={:?}, kind={:?})",
 452                upvar_id, upvar_capture, kind);
 453
 454         match *upvar_capture {
 455             ty::UpvarCapture::ByValue => {
 456                 // Upvar is already by-value, the strongest criteria.
 457             }
 458             ty::UpvarCapture::ByRef(ref mut upvar_borrow) => {
 459                 match (upvar_borrow.kind, kind) {
 460                     // Take RHS:
 461                     (ty::ImmBorrow, ty::UniqueImmBorrow) |
 462                     (ty::ImmBorrow, ty::MutBorrow) |
 463                     (ty::UniqueImmBorrow, ty::MutBorrow) => {
 464                         upvar_borrow.kind = kind;
 465                     }
 466                     // Take LHS:
 467                     (ty::ImmBorrow, ty::ImmBorrow) |
 468                     (ty::UniqueImmBorrow, ty::ImmBorrow) |
 469                     (ty::UniqueImmBorrow, ty::UniqueImmBorrow) |
 470                     (ty::MutBorrow, _) => {
 471                     }
 472                 }
 473             }
 474         }
 475     }
 476
 477     fn adjust_closure_kind(&mut self,
 478                            closure_id: ast::NodeId,
 479                            new_kind: ty::ClosureKind,
 480                            upvar_span: Span,
 481                            var_name: ast::Name) {
 482         debug!("adjust_closure_kind(closure_id={}, new_kind={:?}, upvar_span={:?}, var_name={})",
 483                closure_id, new_kind, upvar_span, var_name);
 484
 485         if let Some(&(existing_kind, _)) = self.temp_closure_kinds.get(&closure_id) {
 486             debug!("adjust_closure_kind: closure_id={}, existing_kind={:?}, new_kind={:?}",
 487                    closure_id, existing_kind, new_kind);
 488
 489             match (existing_kind, new_kind) {
 490                 (ty::ClosureKind::Fn, ty::ClosureKind::Fn) |
 491                 (ty::ClosureKind::FnMut, ty::ClosureKind::Fn) |
 492                 (ty::ClosureKind::FnMut, ty::ClosureKind::FnMut) |
 493                 (ty::ClosureKind::FnOnce, _) => {
 494                     // no change needed
 495                 }
 496
 497                 (ty::ClosureKind::Fn, ty::ClosureKind::FnMut) |
 498                 (ty::ClosureKind::Fn, ty::ClosureKind::FnOnce) |
 499                 (ty::ClosureKind::FnMut, ty::ClosureKind::FnOnce) => {
 500                     // new kind is stronger than the old kind
 501                     self.temp_closure_kinds.insert(
 502                         closure_id,
 503                         (new_kind, Some((upvar_span, var_name)))
 504                     );
 505                 }
 506             }
 507         }
 508     }
 509 }
 510
 511 impl<'a, 'gcx, 'tcx> Visitor<'gcx> for AdjustBorrowKind<'a, 'gcx, 'tcx> {
 512     fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'gcx> {
 513         NestedVisitorMap::None
 514     }
 515
 516     fn visit_fn(&mut self,
 517                 fn_kind: intravisit::FnKind<'gcx>,
 518                 decl: &'gcx hir::FnDecl,
 519                 body: hir::BodyId,
 520                 span: Span,
 521                 id: ast::NodeId)
 522     {
 523         intravisit::walk_fn(self, fn_kind, decl, body, span, id);
 524
 525         let body = self.fcx.tcx.hir.body(body);
 526         self.visit_body(body);
 527         self.analyze_closure(id, span, body);
 528     }
 529 }
 530
 531 impl<'a, 'gcx, 'tcx> euv::Delegate<'tcx> for AdjustBorrowKind<'a, 'gcx, 'tcx> {
 532     fn consume(&mut self,
 533                _consume_id: ast::NodeId,
 534                _consume_span: Span,
 535                cmt: mc::cmt<'tcx>,
 536                mode: euv::ConsumeMode)
 537     {
 538         debug!("consume(cmt={:?},mode={:?})", cmt, mode);
 539         self.adjust_upvar_borrow_kind_for_consume(cmt, mode);
 540     }
 541
 542     fn matched_pat(&mut self,
 543                    _matched_pat: &hir::Pat,
 544                    _cmt: mc::cmt<'tcx>,
 545                    _mode: euv::MatchMode)
 546     {}
 547
 548     fn consume_pat(&mut self,
 549                    _consume_pat: &hir::Pat,
 550                    cmt: mc::cmt<'tcx>,
 551                    mode: euv::ConsumeMode)
 552     {
 553         debug!("consume_pat(cmt={:?},mode={:?})", cmt, mode);
 554         self.adjust_upvar_borrow_kind_for_consume(cmt, mode);
 555     }
 556
 557     fn borrow(&mut self,
 558               borrow_id: ast::NodeId,
 559               _borrow_span: Span,
 560               cmt: mc::cmt<'tcx>,
 561               _loan_region: ty::Region<'tcx>,
 562               bk: ty::BorrowKind,
 563               _loan_cause: euv::LoanCause)
 564     {
 565         debug!("borrow(borrow_id={}, cmt={:?}, bk={:?})",
 566                borrow_id, cmt, bk);
 567
 568         match bk {
 569             ty::ImmBorrow => { }
 570             ty::UniqueImmBorrow => {
 571                 self.adjust_upvar_borrow_kind_for_unique(cmt);
 572             }
 573             ty::MutBorrow => {
 574                 self.adjust_upvar_borrow_kind_for_mut(cmt);
 575             }
 576         }
 577     }
 578
 579     fn decl_without_init(&mut self,
 580                          _id: ast::NodeId,
 581                          _span: Span)
 582     {}
 583
 584     fn mutate(&mut self,
 585               _assignment_id: ast::NodeId,
 586               _assignment_span: Span,
 587               assignee_cmt: mc::cmt<'tcx>,
 588               _mode: euv::MutateMode)
 589     {
 590         debug!("mutate(assignee_cmt={:?})",
 591                assignee_cmt);
 592
 593         self.adjust_upvar_borrow_kind_for_mut(assignee_cmt);
 594     }
 595 }