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 param_env = self.fcx.param_env;
 170             let mut euv =
 171                 euv::ExprUseVisitor::with_options(self,
 172                                                   self.fcx,
 173                                                   param_env,
 174                                                   region_maps,
 175                                                   mc::MemCategorizationOptions {
 176                                                       during_closure_kind_inference: true
 177                                                   });
 178             euv.consume_body(body);
 179         }
 180
 181         // Now that we've analyzed the closure, we know how each
 182         // variable is borrowed, and we know what traits the closure
 183         // implements (Fn vs FnMut etc). We now have some updates to do
 184         // with that information.
 185         //
 186         // Note that no closure type C may have an upvar of type C
 187         // (though it may reference itself via a trait object). This
 188         // results from the desugaring of closures to a struct like
 189         // `Foo<..., UV0...UVn>`. If one of those upvars referenced
 190         // C, then the type would have infinite size (and the
 191         // inference algorithm will reject it).
 192
 193         // Extract the type variables UV0...UVn.
 194         let (def_id, closure_substs) = match self.fcx.node_ty(id).sty {
 195             ty::TyClosure(def_id, substs) => (def_id, substs),
 196             ref t => {
 197                 span_bug!(
 198                     span,
 199                     "type of closure expr {:?} is not a closure {:?}",
 200                     id, t);
 201             }
 202         };
 203
 204         // Equate the type variables with the actual types.
 205         let final_upvar_tys = self.final_upvar_tys(id);
 206         debug!("analyze_closure: id={:?} closure_substs={:?} final_upvar_tys={:?}",
 207                id, closure_substs, final_upvar_tys);
 208         for (upvar_ty, final_upvar_ty) in
 209             closure_substs.upvar_tys(def_id, self.fcx.tcx).zip(final_upvar_tys)
 210         {
 211             self.fcx.demand_eqtype(span, final_upvar_ty, upvar_ty);
 212         }
 213
 214         // If we are also inferred the closure kind here, update the
 215         // main table and process any deferred resolutions.
 216         if let Some(&(kind, context)) = self.temp_closure_kinds.get(&id) {
 217             self.fcx.tables.borrow_mut().closure_kinds.insert(id, (kind, context));
 218             let closure_def_id = self.fcx.tcx.hir.local_def_id(id);
 219             debug!("closure_kind({:?}) = {:?}", closure_def_id, kind);
 220
 221             let deferred_call_resolutions =
 222                 self.fcx.remove_deferred_call_resolutions(closure_def_id);
 223             for deferred_call_resolution in deferred_call_resolutions {
 224                 deferred_call_resolution.resolve(self.fcx);
 225             }
 226         }
 227     }
 228
 229     // Returns a list of `ClosureUpvar`s for each upvar.
 230     fn final_upvar_tys(&mut self, closure_id: ast::NodeId) -> Vec<Ty<'tcx>> {
 231         // Presently an unboxed closure type cannot "escape" out of a
 232         // function, so we will only encounter ones that originated in the
 233         // local crate or were inlined into it along with some function.
 234         // This may change if abstract return types of some sort are
 235         // implemented.
 236         let tcx = self.fcx.tcx;
 237         tcx.with_freevars(closure_id, |freevars| {
 238             freevars.iter().map(|freevar| {
 239                 let def_id = freevar.def.def_id();
 240                 let var_id = tcx.hir.as_local_node_id(def_id).unwrap();
 241                 let freevar_ty = self.fcx.node_ty(var_id);
 242                 let upvar_id = ty::UpvarId {
 243                     var_id: var_id,
 244                     closure_expr_id: closure_id
 245                 };
 246                 let capture = self.fcx.upvar_capture(upvar_id).unwrap();
 247
 248                 debug!("var_id={:?} freevar_ty={:?} capture={:?}",
 249                        var_id, freevar_ty, capture);
 250
 251                 match capture {
 252                     ty::UpvarCapture::ByValue => freevar_ty,
 253                     ty::UpvarCapture::ByRef(borrow) =>
 254                         tcx.mk_ref(borrow.region,
 255                                     ty::TypeAndMut {
 256                                         ty: freevar_ty,
 257                                         mutbl: borrow.kind.to_mutbl_lossy(),
 258                                     }),
 259                 }
 260             }).collect()
 261         })
 262     }
 263
 264     fn adjust_upvar_borrow_kind_for_consume(&mut self,
 265                                             cmt: mc::cmt<'tcx>,
 266                                             mode: euv::ConsumeMode)
 267     {
 268         debug!("adjust_upvar_borrow_kind_for_consume(cmt={:?}, mode={:?})",
 269                cmt, mode);
 270
 271         // we only care about moves
 272         match mode {
 273             euv::Copy => { return; }
 274             euv::Move(_) => { }
 275         }
 276
 277         let tcx = self.fcx.tcx;
 278
 279         // watch out for a move of the deref of a borrowed pointer;
 280         // for that to be legal, the upvar would have to be borrowed
 281         // by value instead
 282         let guarantor = cmt.guarantor();
 283         debug!("adjust_upvar_borrow_kind_for_consume: guarantor={:?}",
 284                guarantor);
 285         match guarantor.cat {
 286             Categorization::Deref(_, mc::BorrowedPtr(..)) |
 287             Categorization::Deref(_, mc::Implicit(..)) => {
 288                 match cmt.note {
 289                     mc::NoteUpvarRef(upvar_id) => {
 290                         debug!("adjust_upvar_borrow_kind_for_consume: \
 291                                 setting upvar_id={:?} to by value",
 292                                upvar_id);
 293
 294                         // to move out of an upvar, this must be a FnOnce closure
 295                         self.adjust_closure_kind(upvar_id.closure_expr_id,
 296                                                  ty::ClosureKind::FnOnce,
 297                                                  guarantor.span,
 298                                                  tcx.hir.name(upvar_id.var_id));
 299
 300                         let upvar_capture_map =
 301                             &mut self.fcx.tables.borrow_mut().upvar_capture_map;
 302                         upvar_capture_map.insert(upvar_id, ty::UpvarCapture::ByValue);
 303                     }
 304                     mc::NoteClosureEnv(upvar_id) => {
 305                         // we get just a closureenv ref if this is a
 306                         // `move` closure, or if the upvar has already
 307                         // been inferred to by-value. In any case, we
 308                         // must still adjust the kind of the closure
 309                         // to be a FnOnce closure to permit moves out
 310                         // of the environment.
 311                         self.adjust_closure_kind(upvar_id.closure_expr_id,
 312                                                  ty::ClosureKind::FnOnce,
 313                                                  guarantor.span,
 314                                                  tcx.hir.name(upvar_id.var_id));
 315                     }
 316                     mc::NoteNone => {
 317                     }
 318                 }
 319             }
 320             _ => { }
 321         }
 322     }
 323
 324     /// Indicates that `cmt` is being directly mutated (e.g., assigned
 325     /// to). If cmt contains any by-ref upvars, this implies that
 326     /// those upvars must be borrowed using an `&mut` borrow.
 327     fn adjust_upvar_borrow_kind_for_mut(&mut self, cmt: mc::cmt<'tcx>) {
 328         debug!("adjust_upvar_borrow_kind_for_mut(cmt={:?})",
 329                cmt);
 330
 331         match cmt.cat.clone() {
 332             Categorization::Deref(base, mc::Unique) |
 333             Categorization::Interior(base, _) |
 334             Categorization::Downcast(base, _) => {
 335                 // Interior or owned data is mutable if base is
 336                 // mutable, so iterate to the base.
 337                 self.adjust_upvar_borrow_kind_for_mut(base);
 338             }
 339
 340             Categorization::Deref(base, mc::BorrowedPtr(..)) |
 341             Categorization::Deref(base, mc::Implicit(..)) => {
 342                 if !self.try_adjust_upvar_deref(cmt, ty::MutBorrow) {
 343                     // assignment to deref of an `&mut`
 344                     // borrowed pointer implies that the
 345                     // pointer itself must be unique, but not
 346                     // necessarily *mutable*
 347                     self.adjust_upvar_borrow_kind_for_unique(base);
 348                 }
 349             }
 350
 351             Categorization::Deref(_, mc::UnsafePtr(..)) |
 352             Categorization::StaticItem |
 353             Categorization::Rvalue(..) |
 354             Categorization::Local(_) |
 355             Categorization::Upvar(..) => {
 356                 return;
 357             }
 358         }
 359     }
 360
 361     fn adjust_upvar_borrow_kind_for_unique(&mut self, cmt: mc::cmt<'tcx>) {
 362         debug!("adjust_upvar_borrow_kind_for_unique(cmt={:?})",
 363                cmt);
 364
 365         match cmt.cat.clone() {
 366             Categorization::Deref(base, mc::Unique) |
 367             Categorization::Interior(base, _) |
 368             Categorization::Downcast(base, _) => {
 369                 // Interior or owned data is unique if base is
 370                 // unique.
 371                 self.adjust_upvar_borrow_kind_for_unique(base);
 372             }
 373
 374             Categorization::Deref(base, mc::BorrowedPtr(..)) |
 375             Categorization::Deref(base, mc::Implicit(..)) => {
 376                 if !self.try_adjust_upvar_deref(cmt, ty::UniqueImmBorrow) {
 377                     // for a borrowed pointer to be unique, its
 378                     // base must be unique
 379                     self.adjust_upvar_borrow_kind_for_unique(base);
 380                 }
 381             }
 382
 383             Categorization::Deref(_, mc::UnsafePtr(..)) |
 384             Categorization::StaticItem |
 385             Categorization::Rvalue(..) |
 386             Categorization::Local(_) |
 387             Categorization::Upvar(..) => {
 388             }
 389         }
 390     }
 391
 392     fn try_adjust_upvar_deref(&mut self,
 393                               cmt: mc::cmt<'tcx>,
 394                               borrow_kind: ty::BorrowKind)
 395                               -> bool
 396     {
 397         assert!(match borrow_kind {
 398             ty::MutBorrow => true,
 399             ty::UniqueImmBorrow => true,
 400
 401             // imm borrows never require adjusting any kinds, so we don't wind up here
 402             ty::ImmBorrow => false,
 403         });
 404
 405         let tcx = self.fcx.tcx;
 406
 407         match cmt.note {
 408             mc::NoteUpvarRef(upvar_id) => {
 409                 // if this is an implicit deref of an
 410                 // upvar, then we need to modify the
 411                 // borrow_kind of the upvar to make sure it
 412                 // is inferred to mutable if necessary
 413                 {
 414                     let upvar_capture_map = &mut self.fcx.tables.borrow_mut().upvar_capture_map;
 415                     let ub = upvar_capture_map.get_mut(&upvar_id).unwrap();
 416                     self.adjust_upvar_borrow_kind(upvar_id, ub, borrow_kind);
 417                 }
 418
 419                 // also need to be in an FnMut closure since this is not an ImmBorrow
 420                 self.adjust_closure_kind(upvar_id.closure_expr_id,
 421                                          ty::ClosureKind::FnMut,
 422                                          cmt.span,
 423                                          tcx.hir.name(upvar_id.var_id));
 424
 425                 true
 426             }
 427             mc::NoteClosureEnv(upvar_id) => {
 428                 // this kind of deref occurs in a `move` closure, or
 429                 // for a by-value upvar; in either case, to mutate an
 430                 // upvar, we need to be an FnMut closure
 431                 self.adjust_closure_kind(upvar_id.closure_expr_id,
 432                                          ty::ClosureKind::FnMut,
 433                                          cmt.span,
 434                                          tcx.hir.name(upvar_id.var_id));
 435
 436                 true
 437             }
 438             mc::NoteNone => {
 439                 false
 440             }
 441         }
 442     }
 443
 444     /// We infer the borrow_kind with which to borrow upvars in a stack closure.
 445     /// The borrow_kind basically follows a lattice of `imm < unique-imm < mut`,
 446     /// moving from left to right as needed (but never right to left).
 447     /// Here the argument `mutbl` is the borrow_kind that is required by
 448     /// some particular use.
 449     fn adjust_upvar_borrow_kind(&mut self,
 450                                 upvar_id: ty::UpvarId,
 451                                 upvar_capture: &mut ty::UpvarCapture,
 452                                 kind: ty::BorrowKind) {
 453         debug!("adjust_upvar_borrow_kind(upvar_id={:?}, upvar_capture={:?}, kind={:?})",
 454                upvar_id, upvar_capture, kind);
 455
 456         match *upvar_capture {
 457             ty::UpvarCapture::ByValue => {
 458                 // Upvar is already by-value, the strongest criteria.
 459             }
 460             ty::UpvarCapture::ByRef(ref mut upvar_borrow) => {
 461                 match (upvar_borrow.kind, kind) {
 462                     // Take RHS:
 463                     (ty::ImmBorrow, ty::UniqueImmBorrow) |
 464                     (ty::ImmBorrow, ty::MutBorrow) |
 465                     (ty::UniqueImmBorrow, ty::MutBorrow) => {
 466                         upvar_borrow.kind = kind;
 467                     }
 468                     // Take LHS:
 469                     (ty::ImmBorrow, ty::ImmBorrow) |
 470                     (ty::UniqueImmBorrow, ty::ImmBorrow) |
 471                     (ty::UniqueImmBorrow, ty::UniqueImmBorrow) |
 472                     (ty::MutBorrow, _) => {
 473                     }
 474                 }
 475             }
 476         }
 477     }
 478
 479     fn adjust_closure_kind(&mut self,
 480                            closure_id: ast::NodeId,
 481                            new_kind: ty::ClosureKind,
 482                            upvar_span: Span,
 483                            var_name: ast::Name) {
 484         debug!("adjust_closure_kind(closure_id={}, new_kind={:?}, upvar_span={:?}, var_name={})",
 485                closure_id, new_kind, upvar_span, var_name);
 486
 487         if let Some(&(existing_kind, _)) = self.temp_closure_kinds.get(&closure_id) {
 488             debug!("adjust_closure_kind: closure_id={}, existing_kind={:?}, new_kind={:?}",
 489                    closure_id, existing_kind, new_kind);
 490
 491             match (existing_kind, new_kind) {
 492                 (ty::ClosureKind::Fn, ty::ClosureKind::Fn) |
 493                 (ty::ClosureKind::FnMut, ty::ClosureKind::Fn) |
 494                 (ty::ClosureKind::FnMut, ty::ClosureKind::FnMut) |
 495                 (ty::ClosureKind::FnOnce, _) => {
 496                     // no change needed
 497                 }
 498
 499                 (ty::ClosureKind::Fn, ty::ClosureKind::FnMut) |
 500                 (ty::ClosureKind::Fn, ty::ClosureKind::FnOnce) |
 501                 (ty::ClosureKind::FnMut, ty::ClosureKind::FnOnce) => {
 502                     // new kind is stronger than the old kind
 503                     self.temp_closure_kinds.insert(
 504                         closure_id,
 505                         (new_kind, Some((upvar_span, var_name)))
 506                     );
 507                 }
 508             }
 509         }
 510     }
 511 }
 512
 513 impl<'a, 'gcx, 'tcx> Visitor<'gcx> for AdjustBorrowKind<'a, 'gcx, 'tcx> {
 514     fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'gcx> {
 515         NestedVisitorMap::None
 516     }
 517
 518     fn visit_fn(&mut self,
 519                 fn_kind: intravisit::FnKind<'gcx>,
 520                 decl: &'gcx hir::FnDecl,
 521                 body: hir::BodyId,
 522                 span: Span,
 523                 id: ast::NodeId)
 524     {
 525         intravisit::walk_fn(self, fn_kind, decl, body, span, id);
 526
 527         let body = self.fcx.tcx.hir.body(body);
 528         self.visit_body(body);
 529         self.analyze_closure(id, span, body);
 530     }
 531 }
 532
 533 impl<'a, 'gcx, 'tcx> euv::Delegate<'tcx> for AdjustBorrowKind<'a, 'gcx, 'tcx> {
 534     fn consume(&mut self,
 535                _consume_id: ast::NodeId,
 536                _consume_span: Span,
 537                cmt: mc::cmt<'tcx>,
 538                mode: euv::ConsumeMode)
 539     {
 540         debug!("consume(cmt={:?},mode={:?})", cmt, mode);
 541         self.adjust_upvar_borrow_kind_for_consume(cmt, mode);
 542     }
 543
 544     fn matched_pat(&mut self,
 545                    _matched_pat: &hir::Pat,
 546                    _cmt: mc::cmt<'tcx>,
 547                    _mode: euv::MatchMode)
 548     {}
 549
 550     fn consume_pat(&mut self,
 551                    _consume_pat: &hir::Pat,
 552                    cmt: mc::cmt<'tcx>,
 553                    mode: euv::ConsumeMode)
 554     {
 555         debug!("consume_pat(cmt={:?},mode={:?})", cmt, mode);
 556         self.adjust_upvar_borrow_kind_for_consume(cmt, mode);
 557     }
 558
 559     fn borrow(&mut self,
 560               borrow_id: ast::NodeId,
 561               _borrow_span: Span,
 562               cmt: mc::cmt<'tcx>,
 563               _loan_region: ty::Region<'tcx>,
 564               bk: ty::BorrowKind,
 565               _loan_cause: euv::LoanCause)
 566     {
 567         debug!("borrow(borrow_id={}, cmt={:?}, bk={:?})",
 568                borrow_id, cmt, bk);
 569
 570         match bk {
 571             ty::ImmBorrow => { }
 572             ty::UniqueImmBorrow => {
 573                 self.adjust_upvar_borrow_kind_for_unique(cmt);
 574             }
 575             ty::MutBorrow => {
 576                 self.adjust_upvar_borrow_kind_for_mut(cmt);
 577             }
 578         }
 579     }
 580
 581     fn decl_without_init(&mut self,
 582                          _id: ast::NodeId,
 583                          _span: Span)
 584     {}
 585
 586     fn mutate(&mut self,
 587               _assignment_id: ast::NodeId,
 588               _assignment_span: Span,
 589               assignee_cmt: mc::cmt<'tcx>,
 590               _mode: euv::MutateMode)
 591     {
 592         debug!("mutate(assignee_cmt={:?})",
 593                assignee_cmt);
 594
 595         self.adjust_upvar_borrow_kind_for_mut(assignee_cmt);
 596     }
 597 }