src/librustc/middle/expr_use_visitor.rs

   1 // Copyright 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 //! A different sort of visitor for walking fn bodies.  Unlike the
  12 //! normal visitor, which just walks the entire body in one shot, the
  13 //! `ExprUseVisitor` determines how expressions are being used.
  14
  15 pub use self::LoanCause::*;
  16 pub use self::ConsumeMode::*;
  17 pub use self::MoveReason::*;
  18 pub use self::MatchMode::*;
  19 use self::TrackMatchMode::*;
  20 use self::OverloadedCallType::*;
  21
  22 use hir::def::Def;
  23 use hir::def_id::{DefId};
  24 use infer::InferCtxt;
  25 use middle::mem_categorization as mc;
  26 use middle::region::RegionMaps;
  27 use ty::{self, TyCtxt, adjustment};
  28
  29 use hir::{self, PatKind};
  30
  31 use syntax::ast;
  32 use syntax::ptr::P;
  33 use syntax_pos::Span;
  34
  35 ///////////////////////////////////////////////////////////////////////////
  36 // The Delegate trait
  37
  38 /// This trait defines the callbacks you can expect to receive when
  39 /// employing the ExprUseVisitor.
  40 pub trait Delegate<'tcx> {
  41     // The value found at `cmt` is either copied or moved, depending
  42     // on mode.
  43     fn consume(&mut self,
  44                consume_id: ast::NodeId,
  45                consume_span: Span,
  46                cmt: mc::cmt<'tcx>,
  47                mode: ConsumeMode);
  48
  49     // The value found at `cmt` has been determined to match the
  50     // pattern binding `matched_pat`, and its subparts are being
  51     // copied or moved depending on `mode`.  Note that `matched_pat`
  52     // is called on all variant/structs in the pattern (i.e., the
  53     // interior nodes of the pattern's tree structure) while
  54     // consume_pat is called on the binding identifiers in the pattern
  55     // (which are leaves of the pattern's tree structure).
  56     //
  57     // Note that variants/structs and identifiers are disjoint; thus
  58     // `matched_pat` and `consume_pat` are never both called on the
  59     // same input pattern structure (though of `consume_pat` can be
  60     // called on a subpart of an input passed to `matched_pat).
  61     fn matched_pat(&mut self,
  62                    matched_pat: &hir::Pat,
  63                    cmt: mc::cmt<'tcx>,
  64                    mode: MatchMode);
  65
  66     // The value found at `cmt` is either copied or moved via the
  67     // pattern binding `consume_pat`, depending on mode.
  68     fn consume_pat(&mut self,
  69                    consume_pat: &hir::Pat,
  70                    cmt: mc::cmt<'tcx>,
  71                    mode: ConsumeMode);
  72
  73     // The value found at `borrow` is being borrowed at the point
  74     // `borrow_id` for the region `loan_region` with kind `bk`.
  75     fn borrow(&mut self,
  76               borrow_id: ast::NodeId,
  77               borrow_span: Span,
  78               cmt: mc::cmt<'tcx>,
  79               loan_region: ty::Region<'tcx>,
  80               bk: ty::BorrowKind,
  81               loan_cause: LoanCause);
  82
  83     // The local variable `id` is declared but not initialized.
  84     fn decl_without_init(&mut self,
  85                          id: ast::NodeId,
  86                          span: Span);
  87
  88     // The path at `cmt` is being assigned to.
  89     fn mutate(&mut self,
  90               assignment_id: ast::NodeId,
  91               assignment_span: Span,
  92               assignee_cmt: mc::cmt<'tcx>,
  93               mode: MutateMode);
  94 }
  95
  96 #[derive(Copy, Clone, PartialEq, Debug)]
  97 pub enum LoanCause {
  98     ClosureCapture(Span),
  99     AddrOf,
 100     AutoRef,
 101     AutoUnsafe,
 102     RefBinding,
 103     OverloadedOperator,
 104     ClosureInvocation,
 105     ForLoop,
 106     MatchDiscriminant
 107 }
 108
 109 #[derive(Copy, Clone, PartialEq, Debug)]
 110 pub enum ConsumeMode {
 111     Copy,                // reference to x where x has a type that copies
 112     Move(MoveReason),    // reference to x where x has a type that moves
 113 }
 114
 115 #[derive(Copy, Clone, PartialEq, Debug)]
 116 pub enum MoveReason {
 117     DirectRefMove,
 118     PatBindingMove,
 119     CaptureMove,
 120 }
 121
 122 #[derive(Copy, Clone, PartialEq, Debug)]
 123 pub enum MatchMode {
 124     NonBindingMatch,
 125     BorrowingMatch,
 126     CopyingMatch,
 127     MovingMatch,
 128 }
 129
 130 #[derive(Copy, Clone, PartialEq, Debug)]
 131 enum TrackMatchMode {
 132     Unknown,
 133     Definite(MatchMode),
 134     Conflicting,
 135 }
 136
 137 impl TrackMatchMode {
 138     // Builds up the whole match mode for a pattern from its constituent
 139     // parts.  The lattice looks like this:
 140     //
 141     //          Conflicting
 142     //            /     \
 143     //           /       \
 144     //      Borrowing   Moving
 145     //           \       /
 146     //            \     /
 147     //            Copying
 148     //               |
 149     //          NonBinding
 150     //               |
 151     //            Unknown
 152     //
 153     // examples:
 154     //
 155     // * `(_, some_int)` pattern is Copying, since
 156     //   NonBinding + Copying => Copying
 157     //
 158     // * `(some_int, some_box)` pattern is Moving, since
 159     //   Copying + Moving => Moving
 160     //
 161     // * `(ref x, some_box)` pattern is Conflicting, since
 162     //   Borrowing + Moving => Conflicting
 163     //
 164     // Note that the `Unknown` and `Conflicting` states are
 165     // represented separately from the other more interesting
 166     // `Definite` states, which simplifies logic here somewhat.
 167     fn lub(&mut self, mode: MatchMode) {
 168         *self = match (*self, mode) {
 169             // Note that clause order below is very significant.
 170             (Unknown, new) => Definite(new),
 171             (Definite(old), new) if old == new => Definite(old),
 172
 173             (Definite(old), NonBindingMatch) => Definite(old),
 174             (Definite(NonBindingMatch), new) => Definite(new),
 175
 176             (Definite(old), CopyingMatch) => Definite(old),
 177             (Definite(CopyingMatch), new) => Definite(new),
 178
 179             (Definite(_), _) => Conflicting,
 180             (Conflicting, _) => *self,
 181         };
 182     }
 183
 184     fn match_mode(&self) -> MatchMode {
 185         match *self {
 186             Unknown => NonBindingMatch,
 187             Definite(mode) => mode,
 188             Conflicting => {
 189                 // Conservatively return MovingMatch to let the
 190                 // compiler continue to make progress.
 191                 MovingMatch
 192             }
 193         }
 194     }
 195 }
 196
 197 #[derive(Copy, Clone, PartialEq, Debug)]
 198 pub enum MutateMode {
 199     Init,
 200     JustWrite,    // x = y
 201     WriteAndRead, // x += y
 202 }
 203
 204 #[derive(Copy, Clone)]
 205 enum OverloadedCallType {
 206     FnOverloadedCall,
 207     FnMutOverloadedCall,
 208     FnOnceOverloadedCall,
 209 }
 210
 211 impl OverloadedCallType {
 212     fn from_trait_id(tcx: TyCtxt, trait_id: DefId) -> OverloadedCallType {
 213         for &(maybe_function_trait, overloaded_call_type) in &[
 214             (tcx.lang_items.fn_once_trait(), FnOnceOverloadedCall),
 215             (tcx.lang_items.fn_mut_trait(), FnMutOverloadedCall),
 216             (tcx.lang_items.fn_trait(), FnOverloadedCall)
 217         ] {
 218             match maybe_function_trait {
 219                 Some(function_trait) if function_trait == trait_id => {
 220                     return overloaded_call_type
 221                 }
 222                 _ => continue,
 223             }
 224         }
 225
 226         bug!("overloaded call didn't map to known function trait")
 227     }
 228
 229     fn from_method_id(tcx: TyCtxt, method_id: DefId) -> OverloadedCallType {
 230         let method = tcx.associated_item(method_id);
 231         OverloadedCallType::from_trait_id(tcx, method.container.id())
 232     }
 233 }
 234
 235 ///////////////////////////////////////////////////////////////////////////
 236 // The ExprUseVisitor type
 237 //
 238 // This is the code that actually walks the tree.
 239 pub struct ExprUseVisitor<'a, 'gcx: 'a+'tcx, 'tcx: 'a> {
 240     mc: mc::MemCategorizationContext<'a, 'gcx, 'tcx>,
 241     delegate: &'a mut Delegate<'tcx>,
 242     param_env: ty::ParamEnv<'tcx>,
 243 }
 244
 245 // If the MC results in an error, it's because the type check
 246 // failed (or will fail, when the error is uncovered and reported
 247 // during writeback). In this case, we just ignore this part of the
 248 // code.
 249 //
 250 // Note that this macro appears similar to try!(), but, unlike try!(),
 251 // it does not propagate the error.
 252 macro_rules! return_if_err {
 253     ($inp: expr) => (
 254         match $inp {
 255             Ok(v) => v,
 256             Err(()) => {
 257                 debug!("mc reported err");
 258                 return
 259             }
 260         }
 261     )
 262 }
 263
 264 impl<'a, 'tcx> ExprUseVisitor<'a, 'tcx, 'tcx> {
 265     pub fn new(delegate: &'a mut (Delegate<'tcx>+'a),
 266                tcx: TyCtxt<'a, 'tcx, 'tcx>,
 267                param_env: ty::ParamEnv<'tcx>,
 268                region_maps: &'a RegionMaps,
 269                tables: &'a ty::TypeckTables<'tcx>)
 270                -> Self
 271     {
 272         ExprUseVisitor {
 273             mc: mc::MemCategorizationContext::new(tcx, region_maps, tables),
 274             delegate,
 275             param_env,
 276         }
 277     }
 278 }
 279
 280 impl<'a, 'gcx, 'tcx> ExprUseVisitor<'a, 'gcx, 'tcx> {
 281     pub fn with_infer(delegate: &'a mut (Delegate<'tcx>+'a),
 282                       infcx: &'a InferCtxt<'a, 'gcx, 'tcx>,
 283                       param_env: ty::ParamEnv<'tcx>,
 284                       region_maps: &'a RegionMaps,
 285                       tables: &'a ty::TypeckTables<'tcx>)
 286                       -> Self
 287     {
 288         ExprUseVisitor {
 289             mc: mc::MemCategorizationContext::with_infer(infcx, region_maps, tables),
 290             delegate,
 291             param_env,
 292         }
 293     }
 294
 295     pub fn consume_body(&mut self, body: &hir::Body) {
 296         debug!("consume_body(body={:?})", body);
 297
 298         for arg in &body.arguments {
 299             let arg_ty = return_if_err!(self.mc.node_ty(arg.pat.id));
 300
 301             let fn_body_scope_r = self.tcx().node_scope_region(body.value.id);
 302             let arg_cmt = self.mc.cat_rvalue(
 303                 arg.id,
 304                 arg.pat.span,
 305                 fn_body_scope_r, // Args live only as long as the fn body.
 306                 arg_ty);
 307
 308             self.walk_irrefutable_pat(arg_cmt, &arg.pat);
 309         }
 310
 311         self.consume_expr(&body.value);
 312     }
 313
 314     fn tcx(&self) -> TyCtxt<'a, 'gcx, 'tcx> {
 315         self.mc.tcx
 316     }
 317
 318     fn delegate_consume(&mut self,
 319                         consume_id: ast::NodeId,
 320                         consume_span: Span,
 321                         cmt: mc::cmt<'tcx>) {
 322         debug!("delegate_consume(consume_id={}, cmt={:?})",
 323                consume_id, cmt);
 324
 325         let mode = copy_or_move(&self.mc, self.param_env, &cmt, DirectRefMove);
 326         self.delegate.consume(consume_id, consume_span, cmt, mode);
 327     }
 328
 329     fn consume_exprs(&mut self, exprs: &[hir::Expr]) {
 330         for expr in exprs {
 331             self.consume_expr(&expr);
 332         }
 333     }
 334
 335     pub fn consume_expr(&mut self, expr: &hir::Expr) {
 336         debug!("consume_expr(expr={:?})", expr);
 337
 338         let cmt = return_if_err!(self.mc.cat_expr(expr));
 339         self.delegate_consume(expr.id, expr.span, cmt);
 340         self.walk_expr(expr);
 341     }
 342
 343     fn mutate_expr(&mut self,
 344                    assignment_expr: &hir::Expr,
 345                    expr: &hir::Expr,
 346                    mode: MutateMode) {
 347         let cmt = return_if_err!(self.mc.cat_expr(expr));
 348         self.delegate.mutate(assignment_expr.id, assignment_expr.span, cmt, mode);
 349         self.walk_expr(expr);
 350     }
 351
 352     fn borrow_expr(&mut self,
 353                    expr: &hir::Expr,
 354                    r: ty::Region<'tcx>,
 355                    bk: ty::BorrowKind,
 356                    cause: LoanCause) {
 357         debug!("borrow_expr(expr={:?}, r={:?}, bk={:?})",
 358                expr, r, bk);
 359
 360         let cmt = return_if_err!(self.mc.cat_expr(expr));
 361         self.delegate.borrow(expr.id, expr.span, cmt, r, bk, cause);
 362
 363         self.walk_expr(expr)
 364     }
 365
 366     fn select_from_expr(&mut self, expr: &hir::Expr) {
 367         self.walk_expr(expr)
 368     }
 369
 370     pub fn walk_expr(&mut self, expr: &hir::Expr) {
 371         debug!("walk_expr(expr={:?})", expr);
 372
 373         self.walk_adjustment(expr);
 374
 375         match expr.node {
 376             hir::ExprPath(_) => { }
 377
 378             hir::ExprType(ref subexpr, _) => {
 379                 self.walk_expr(&subexpr)
 380             }
 381
 382             hir::ExprUnary(hir::UnDeref, ref base) => {      // *base
 383                 self.select_from_expr(&base);
 384             }
 385
 386             hir::ExprField(ref base, _) => {         // base.f
 387                 self.select_from_expr(&base);
 388             }
 389
 390             hir::ExprTupField(ref base, _) => {         // base.<n>
 391                 self.select_from_expr(&base);
 392             }
 393
 394             hir::ExprIndex(ref lhs, ref rhs) => {       // lhs[rhs]
 395                 self.select_from_expr(&lhs);
 396                 self.consume_expr(&rhs);
 397             }
 398
 399             hir::ExprCall(ref callee, ref args) => {    // callee(args)
 400                 self.walk_callee(expr, &callee);
 401                 self.consume_exprs(args);
 402             }
 403
 404             hir::ExprMethodCall(.., ref args) => { // callee.m(args)
 405                 self.consume_exprs(args);
 406             }
 407
 408             hir::ExprStruct(_, ref fields, ref opt_with) => {
 409                 self.walk_struct_expr(fields, opt_with);
 410             }
 411
 412             hir::ExprTup(ref exprs) => {
 413                 self.consume_exprs(exprs);
 414             }
 415
 416             hir::ExprIf(ref cond_expr, ref then_expr, ref opt_else_expr) => {
 417                 self.consume_expr(&cond_expr);
 418                 self.walk_expr(&then_expr);
 419                 if let Some(ref else_expr) = *opt_else_expr {
 420                     self.consume_expr(&else_expr);
 421                 }
 422             }
 423
 424             hir::ExprMatch(ref discr, ref arms, _) => {
 425                 let discr_cmt = return_if_err!(self.mc.cat_expr(&discr));
 426                 let r = self.tcx().types.re_empty;
 427                 self.borrow_expr(&discr, r, ty::ImmBorrow, MatchDiscriminant);
 428
 429                 // treatment of the discriminant is handled while walking the arms.
 430                 for arm in arms {
 431                     let mode = self.arm_move_mode(discr_cmt.clone(), arm);
 432                     let mode = mode.match_mode();
 433                     self.walk_arm(discr_cmt.clone(), arm, mode);
 434                 }
 435             }
 436
 437             hir::ExprArray(ref exprs) => {
 438                 self.consume_exprs(exprs);
 439             }
 440
 441             hir::ExprAddrOf(m, ref base) => {   // &base
 442                 // make sure that the thing we are pointing out stays valid
 443                 // for the lifetime `scope_r` of the resulting ptr:
 444                 let expr_ty = return_if_err!(self.mc.expr_ty(expr));
 445                 if let ty::TyRef(r, _) = expr_ty.sty {
 446                     let bk = ty::BorrowKind::from_mutbl(m);
 447                     self.borrow_expr(&base, r, bk, AddrOf);
 448                 }
 449             }
 450
 451             hir::ExprInlineAsm(ref ia, ref outputs, ref inputs) => {
 452                 for (o, output) in ia.outputs.iter().zip(outputs) {
 453                     if o.is_indirect {
 454                         self.consume_expr(output);
 455                     } else {
 456                         self.mutate_expr(expr, output,
 457                                          if o.is_rw {
 458                                              MutateMode::WriteAndRead
 459                                          } else {
 460                                              MutateMode::JustWrite
 461                                          });
 462                     }
 463                 }
 464                 self.consume_exprs(inputs);
 465             }
 466
 467             hir::ExprAgain(..) |
 468             hir::ExprLit(..) => {}
 469
 470             hir::ExprLoop(ref blk, _, _) => {
 471                 self.walk_block(&blk);
 472             }
 473
 474             hir::ExprWhile(ref cond_expr, ref blk, _) => {
 475                 self.consume_expr(&cond_expr);
 476                 self.walk_block(&blk);
 477             }
 478
 479             hir::ExprUnary(_, ref lhs) => {
 480                 self.consume_expr(&lhs);
 481             }
 482
 483             hir::ExprBinary(_, ref lhs, ref rhs) => {
 484                 self.consume_expr(&lhs);
 485                 self.consume_expr(&rhs);
 486             }
 487
 488             hir::ExprBlock(ref blk) => {
 489                 self.walk_block(&blk);
 490             }
 491
 492             hir::ExprBreak(_, ref opt_expr) | hir::ExprRet(ref opt_expr) => {
 493                 if let Some(ref expr) = *opt_expr {
 494                     self.consume_expr(&expr);
 495                 }
 496             }
 497
 498             hir::ExprAssign(ref lhs, ref rhs) => {
 499                 self.mutate_expr(expr, &lhs, MutateMode::JustWrite);
 500                 self.consume_expr(&rhs);
 501             }
 502
 503             hir::ExprCast(ref base, _) => {
 504                 self.consume_expr(&base);
 505             }
 506
 507             hir::ExprAssignOp(_, ref lhs, ref rhs) => {
 508                 if self.mc.tables.is_method_call(expr) {
 509                     self.consume_expr(lhs);
 510                 } else {
 511                     self.mutate_expr(expr, &lhs, MutateMode::WriteAndRead);
 512                 }
 513                 self.consume_expr(&rhs);
 514             }
 515
 516             hir::ExprRepeat(ref base, _) => {
 517                 self.consume_expr(&base);
 518             }
 519
 520             hir::ExprClosure(.., fn_decl_span) => {
 521                 self.walk_captures(expr, fn_decl_span)
 522             }
 523
 524             hir::ExprBox(ref base) => {
 525                 self.consume_expr(&base);
 526             }
 527         }
 528     }
 529
 530     fn walk_callee(&mut self, call: &hir::Expr, callee: &hir::Expr) {
 531         let callee_ty = return_if_err!(self.mc.expr_ty_adjusted(callee));
 532         debug!("walk_callee: callee={:?} callee_ty={:?}",
 533                callee, callee_ty);
 534         match callee_ty.sty {
 535             ty::TyFnDef(..) | ty::TyFnPtr(_) => {
 536                 self.consume_expr(callee);
 537             }
 538             ty::TyError => { }
 539             _ => {
 540                 let def_id = self.mc.tables.type_dependent_defs[&call.id].def_id();
 541                 match OverloadedCallType::from_method_id(self.tcx(), def_id) {
 542                     FnMutOverloadedCall => {
 543                         let call_scope_r = self.tcx().node_scope_region(call.id);
 544                         self.borrow_expr(callee,
 545                                          call_scope_r,
 546                                          ty::MutBorrow,
 547                                          ClosureInvocation);
 548                     }
 549                     FnOverloadedCall => {
 550                         let call_scope_r = self.tcx().node_scope_region(call.id);
 551                         self.borrow_expr(callee,
 552                                          call_scope_r,
 553                                          ty::ImmBorrow,
 554                                          ClosureInvocation);
 555                     }
 556                     FnOnceOverloadedCall => self.consume_expr(callee),
 557                 }
 558             }
 559         }
 560     }
 561
 562     fn walk_stmt(&mut self, stmt: &hir::Stmt) {
 563         match stmt.node {
 564             hir::StmtDecl(ref decl, _) => {
 565                 match decl.node {
 566                     hir::DeclLocal(ref local) => {
 567                         self.walk_local(&local);
 568                     }
 569
 570                     hir::DeclItem(_) => {
 571                         // we don't visit nested items in this visitor,
 572                         // only the fn body we were given.
 573                     }
 574                 }
 575             }
 576
 577             hir::StmtExpr(ref expr, _) |
 578             hir::StmtSemi(ref expr, _) => {
 579                 self.consume_expr(&expr);
 580             }
 581         }
 582     }
 583
 584     fn walk_local(&mut self, local: &hir::Local) {
 585         match local.init {
 586             None => {
 587                 let delegate = &mut self.delegate;
 588                 local.pat.each_binding(|_, id, span, _| {
 589                     delegate.decl_without_init(id, span);
 590                 })
 591             }
 592
 593             Some(ref expr) => {
 594                 // Variable declarations with
 595                 // initializers are considered
 596                 // "assigns", which is handled by
 597                 // `walk_pat`:
 598                 self.walk_expr(&expr);
 599                 let init_cmt = return_if_err!(self.mc.cat_expr(&expr));
 600                 self.walk_irrefutable_pat(init_cmt, &local.pat);
 601             }
 602         }
 603     }
 604
 605     /// Indicates that the value of `blk` will be consumed, meaning either copied or moved
 606     /// depending on its type.
 607     fn walk_block(&mut self, blk: &hir::Block) {
 608         debug!("walk_block(blk.id={})", blk.id);
 609
 610         for stmt in &blk.stmts {
 611             self.walk_stmt(stmt);
 612         }
 613
 614         if let Some(ref tail_expr) = blk.expr {
 615             self.consume_expr(&tail_expr);
 616         }
 617     }
 618
 619     fn walk_struct_expr(&mut self,
 620                         fields: &[hir::Field],
 621                         opt_with: &Option<P<hir::Expr>>) {
 622         // Consume the expressions supplying values for each field.
 623         for field in fields {
 624             self.consume_expr(&field.expr);
 625         }
 626
 627         let with_expr = match *opt_with {
 628             Some(ref w) => &**w,
 629             None => { return; }
 630         };
 631
 632         let with_cmt = return_if_err!(self.mc.cat_expr(&with_expr));
 633
 634         // Select just those fields of the `with`
 635         // expression that will actually be used
 636         match with_cmt.ty.sty {
 637             ty::TyAdt(adt, substs) if adt.is_struct() => {
 638                 // Consume those fields of the with expression that are needed.
 639                 for with_field in &adt.struct_variant().fields {
 640                     if !contains_field_named(with_field, fields) {
 641                         let cmt_field = self.mc.cat_field(
 642                             &*with_expr,
 643                             with_cmt.clone(),
 644                             with_field.name,
 645                             with_field.ty(self.tcx(), substs)
 646                         );
 647                         self.delegate_consume(with_expr.id, with_expr.span, cmt_field);
 648                     }
 649                 }
 650             }
 651             _ => {
 652                 // the base expression should always evaluate to a
 653                 // struct; however, when EUV is run during typeck, it
 654                 // may not. This will generate an error earlier in typeck,
 655                 // so we can just ignore it.
 656                 if !self.tcx().sess.has_errors() {
 657                     span_bug!(
 658                         with_expr.span,
 659                         "with expression doesn't evaluate to a struct");
 660                 }
 661             }
 662         }
 663
 664         // walk the with expression so that complex expressions
 665         // are properly handled.
 666         self.walk_expr(with_expr);
 667
 668         fn contains_field_named(field: &ty::FieldDef,
 669                                 fields: &[hir::Field])
 670                                 -> bool
 671         {
 672             fields.iter().any(
 673                 |f| f.name.node == field.name)
 674         }
 675     }
 676
 677     // Invoke the appropriate delegate calls for anything that gets
 678     // consumed or borrowed as part of the automatic adjustment
 679     // process.
 680     fn walk_adjustment(&mut self, expr: &hir::Expr) {
 681         let adjustments = self.mc.tables.expr_adjustments(expr);
 682         let mut cmt = return_if_err!(self.mc.cat_expr_unadjusted(expr));
 683         for adjustment in adjustments {
 684             debug!("walk_adjustment expr={:?} adj={:?}", expr, adjustment);
 685             match adjustment.kind {
 686                 adjustment::Adjust::NeverToAny |
 687                 adjustment::Adjust::ReifyFnPointer |
 688                 adjustment::Adjust::UnsafeFnPointer |
 689                 adjustment::Adjust::ClosureFnPointer |
 690                 adjustment::Adjust::MutToConstPointer |
 691                 adjustment::Adjust::Unsize => {
 692                     // Creating a closure/fn-pointer or unsizing consumes
 693                     // the input and stores it into the resulting rvalue.
 694                     self.delegate_consume(expr.id, expr.span, cmt.clone());
 695                 }
 696
 697                 adjustment::Adjust::Deref(None) => {}
 698
 699                 // Autoderefs for overloaded Deref calls in fact reference
 700                 // their receiver. That is, if we have `(*x)` where `x`
 701                 // is of type `Rc<T>`, then this in fact is equivalent to
 702                 // `x.deref()`. Since `deref()` is declared with `&self`,
 703                 // this is an autoref of `x`.
 704                 adjustment::Adjust::Deref(Some(ref deref)) => {
 705                     let bk = ty::BorrowKind::from_mutbl(deref.mutbl);
 706                     self.delegate.borrow(expr.id, expr.span, cmt.clone(),
 707                                          deref.region, bk, AutoRef);
 708                 }
 709
 710                 adjustment::Adjust::Borrow(ref autoref) => {
 711                     self.walk_autoref(expr, cmt.clone(), autoref);
 712                 }
 713             }
 714             cmt = return_if_err!(self.mc.cat_expr_adjusted(expr, cmt, &adjustment));
 715         }
 716     }
 717
 718     /// Walks the autoref `autoref` applied to the autoderef'd
 719     /// `expr`. `cmt_base` is the mem-categorized form of `expr`
 720     /// after all relevant autoderefs have occurred.
 721     fn walk_autoref(&mut self,
 722                     expr: &hir::Expr,
 723                     cmt_base: mc::cmt<'tcx>,
 724                     autoref: &adjustment::AutoBorrow<'tcx>) {
 725         debug!("walk_autoref(expr.id={} cmt_base={:?} autoref={:?})",
 726                expr.id,
 727                cmt_base,
 728                autoref);
 729
 730         match *autoref {
 731             adjustment::AutoBorrow::Ref(r, m) => {
 732                 self.delegate.borrow(expr.id,
 733                                      expr.span,
 734                                      cmt_base,
 735                                      r,
 736                                      ty::BorrowKind::from_mutbl(m),
 737                                      AutoRef);
 738             }
 739
 740             adjustment::AutoBorrow::RawPtr(m) => {
 741                 debug!("walk_autoref: expr.id={} cmt_base={:?}",
 742                        expr.id,
 743                        cmt_base);
 744
 745                 // Converting from a &T to *T (or &mut T to *mut T) is
 746                 // treated as borrowing it for the enclosing temporary
 747                 // scope.
 748                 let r = self.tcx().node_scope_region(expr.id);
 749
 750                 self.delegate.borrow(expr.id,
 751                                      expr.span,
 752                                      cmt_base,
 753                                      r,
 754                                      ty::BorrowKind::from_mutbl(m),
 755                                      AutoUnsafe);
 756             }
 757         }
 758     }
 759
 760     fn arm_move_mode(&mut self, discr_cmt: mc::cmt<'tcx>, arm: &hir::Arm) -> TrackMatchMode {
 761         let mut mode = Unknown;
 762         for pat in &arm.pats {
 763             self.determine_pat_move_mode(discr_cmt.clone(), &pat, &mut mode);
 764         }
 765         mode
 766     }
 767
 768     fn walk_arm(&mut self, discr_cmt: mc::cmt<'tcx>, arm: &hir::Arm, mode: MatchMode) {
 769         for pat in &arm.pats {
 770             self.walk_pat(discr_cmt.clone(), &pat, mode);
 771         }
 772
 773         if let Some(ref guard) = arm.guard {
 774             self.consume_expr(&guard);
 775         }
 776
 777         self.consume_expr(&arm.body);
 778     }
 779
 780     /// Walks a pat that occurs in isolation (i.e. top-level of fn
 781     /// arg or let binding.  *Not* a match arm or nested pat.)
 782     fn walk_irrefutable_pat(&mut self, cmt_discr: mc::cmt<'tcx>, pat: &hir::Pat) {
 783         let mut mode = Unknown;
 784         self.determine_pat_move_mode(cmt_discr.clone(), pat, &mut mode);
 785         let mode = mode.match_mode();
 786         self.walk_pat(cmt_discr, pat, mode);
 787     }
 788
 789     /// Identifies any bindings within `pat` and accumulates within
 790     /// `mode` whether the overall pattern/match structure is a move,
 791     /// copy, or borrow.
 792     fn determine_pat_move_mode(&mut self,
 793                                cmt_discr: mc::cmt<'tcx>,
 794                                pat: &hir::Pat,
 795                                mode: &mut TrackMatchMode) {
 796         debug!("determine_pat_move_mode cmt_discr={:?} pat={:?}", cmt_discr,
 797                pat);
 798         return_if_err!(self.mc.cat_pattern(cmt_discr, pat, |cmt_pat, pat| {
 799             match pat.node {
 800                 PatKind::Binding(hir::BindByRef(..), ..) =>
 801                     mode.lub(BorrowingMatch),
 802                 PatKind::Binding(hir::BindByValue(..), ..) => {
 803                     match copy_or_move(&self.mc, self.param_env, &cmt_pat, PatBindingMove) {
 804                         Copy => mode.lub(CopyingMatch),
 805                         Move(..) => mode.lub(MovingMatch),
 806                     }
 807                 }
 808                 _ => {}
 809             }
 810         }));
 811     }
 812
 813     /// The core driver for walking a pattern; `match_mode` must be
 814     /// established up front, e.g. via `determine_pat_move_mode` (see
 815     /// also `walk_irrefutable_pat` for patterns that stand alone).
 816     fn walk_pat(&mut self, cmt_discr: mc::cmt<'tcx>, pat: &hir::Pat, match_mode: MatchMode) {
 817         debug!("walk_pat cmt_discr={:?} pat={:?}", cmt_discr, pat);
 818
 819         let tcx = self.tcx();
 820         let ExprUseVisitor { ref mc, ref mut delegate, param_env } = *self;
 821         return_if_err!(mc.cat_pattern(cmt_discr.clone(), pat, |cmt_pat, pat| {
 822             if let PatKind::Binding(bmode, def_id, ..) = pat.node {
 823                 debug!("binding cmt_pat={:?} pat={:?} match_mode={:?}", cmt_pat, pat, match_mode);
 824
 825                 // pat_ty: the type of the binding being produced.
 826                 let pat_ty = return_if_err!(mc.node_ty(pat.id));
 827
 828                 // Each match binding is effectively an assignment to the
 829                 // binding being produced.
 830                 let def = Def::Local(def_id);
 831                 if let Ok(binding_cmt) = mc.cat_def(pat.id, pat.span, pat_ty, def) {
 832                     delegate.mutate(pat.id, pat.span, binding_cmt, MutateMode::Init);
 833                 }
 834
 835                 // It is also a borrow or copy/move of the value being matched.
 836                 match bmode {
 837                     hir::BindByRef(m) => {
 838                         if let ty::TyRef(r, _) = pat_ty.sty {
 839                             let bk = ty::BorrowKind::from_mutbl(m);
 840                             delegate.borrow(pat.id, pat.span, cmt_pat, r, bk, RefBinding);
 841                         }
 842                     }
 843                     hir::BindByValue(..) => {
 844                         let mode = copy_or_move(mc, param_env, &cmt_pat, PatBindingMove);
 845                         debug!("walk_pat binding consuming pat");
 846                         delegate.consume_pat(pat, cmt_pat, mode);
 847                     }
 848                 }
 849             }
 850         }));
 851
 852         // Do a second pass over the pattern, calling `matched_pat` on
 853         // the interior nodes (enum variants and structs), as opposed
 854         // to the above loop's visit of than the bindings that form
 855         // the leaves of the pattern tree structure.
 856         return_if_err!(mc.cat_pattern(cmt_discr, pat, |cmt_pat, pat| {
 857             let qpath = match pat.node {
 858                 PatKind::Path(ref qpath) |
 859                 PatKind::TupleStruct(ref qpath, ..) |
 860                 PatKind::Struct(ref qpath, ..) => qpath,
 861                 _ => return
 862             };
 863             let def = mc.tables.qpath_def(qpath, pat.id);
 864             match def {
 865                 Def::Variant(variant_did) |
 866                 Def::VariantCtor(variant_did, ..) => {
 867                     let enum_did = tcx.parent_def_id(variant_did).unwrap();
 868                     let downcast_cmt = if tcx.adt_def(enum_did).is_univariant() {
 869                         cmt_pat
 870                     } else {
 871                         let cmt_pat_ty = cmt_pat.ty;
 872                         mc.cat_downcast(pat, cmt_pat, cmt_pat_ty, variant_did)
 873                     };
 874
 875                     debug!("variant downcast_cmt={:?} pat={:?}", downcast_cmt, pat);
 876                     delegate.matched_pat(pat, downcast_cmt, match_mode);
 877                 }
 878                 Def::Struct(..) | Def::StructCtor(..) | Def::Union(..) |
 879                 Def::TyAlias(..) | Def::AssociatedTy(..) | Def::SelfTy(..) => {
 880                     debug!("struct cmt_pat={:?} pat={:?}", cmt_pat, pat);
 881                     delegate.matched_pat(pat, cmt_pat, match_mode);
 882                 }
 883                 _ => {}
 884             }
 885         }));
 886     }
 887
 888     fn walk_captures(&mut self, closure_expr: &hir::Expr, fn_decl_span: Span) {
 889         debug!("walk_captures({:?})", closure_expr);
 890
 891         self.tcx().with_freevars(closure_expr.id, |freevars| {
 892             for freevar in freevars {
 893                 let def_id = freevar.def.def_id();
 894                 let id_var = self.tcx().hir.as_local_node_id(def_id).unwrap();
 895                 let upvar_id = ty::UpvarId { var_id: id_var,
 896                                              closure_expr_id: closure_expr.id };
 897                 let upvar_capture = self.mc.tables.upvar_capture(upvar_id);
 898                 let cmt_var = return_if_err!(self.cat_captured_var(closure_expr.id,
 899                                                                    fn_decl_span,
 900                                                                    freevar.def));
 901                 match upvar_capture {
 902                     ty::UpvarCapture::ByValue => {
 903                         let mode = copy_or_move(&self.mc,
 904                                                 self.param_env,
 905                                                 &cmt_var,
 906                                                 CaptureMove);
 907                         self.delegate.consume(closure_expr.id, freevar.span, cmt_var, mode);
 908                     }
 909                     ty::UpvarCapture::ByRef(upvar_borrow) => {
 910                         self.delegate.borrow(closure_expr.id,
 911                                              fn_decl_span,
 912                                              cmt_var,
 913                                              upvar_borrow.region,
 914                                              upvar_borrow.kind,
 915                                              ClosureCapture(freevar.span));
 916                     }
 917                 }
 918             }
 919         });
 920     }
 921
 922     fn cat_captured_var(&mut self,
 923                         closure_id: ast::NodeId,
 924                         closure_span: Span,
 925                         upvar_def: Def)
 926                         -> mc::McResult<mc::cmt<'tcx>> {
 927         // Create the cmt for the variable being borrowed, from the
 928         // caller's perspective
 929         let var_id = self.tcx().hir.as_local_node_id(upvar_def.def_id()).unwrap();
 930         let var_ty = self.mc.node_ty(var_id)?;
 931         self.mc.cat_def(closure_id, closure_span, var_ty, upvar_def)
 932     }
 933 }
 934
 935 fn copy_or_move<'a, 'gcx, 'tcx>(mc: &mc::MemCategorizationContext<'a, 'gcx, 'tcx>,
 936                                 param_env: ty::ParamEnv<'tcx>,
 937                                 cmt: &mc::cmt<'tcx>,
 938                                 move_reason: MoveReason)
 939                                 -> ConsumeMode
 940 {
 941     if mc.type_moves_by_default(param_env, cmt.ty, cmt.span) {
 942         Move(move_reason)
 943     } else {
 944         Copy
 945     }
 946 }