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.
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.
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.
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::*;
24 use middle::def_id::{DefId};
26 use middle::mem_categorization as mc;
28 use middle::ty::adjustment;
30 use rustc_front::hir::{self, PatKind};
34 use syntax::codemap::Span;
36 ///////////////////////////////////////////////////////////////////////////
39 /// This trait defines the callbacks you can expect to receive when
40 /// employing the ExprUseVisitor.
41 pub trait Delegate<'tcx> {
42 // The value found at `cmt` is either copied or moved, depending
45 consume_id: ast::NodeId,
50 // The value found at `cmt` has been determined to match the
51 // pattern binding `matched_pat`, and its subparts are being
52 // copied or moved depending on `mode`. Note that `matched_pat`
53 // is called on all variant/structs in the pattern (i.e., the
54 // interior nodes of the pattern's tree structure) while
55 // consume_pat is called on the binding identifiers in the pattern
56 // (which are leaves of the pattern's tree structure).
58 // Note that variants/structs and identifiers are disjoint; thus
59 // `matched_pat` and `consume_pat` are never both called on the
60 // same input pattern structure (though of `consume_pat` can be
61 // called on a subpart of an input passed to `matched_pat).
62 fn matched_pat(&mut self,
63 matched_pat: &hir::Pat,
67 // The value found at `cmt` is either copied or moved via the
68 // pattern binding `consume_pat`, depending on mode.
69 fn consume_pat(&mut self,
70 consume_pat: &hir::Pat,
74 // The value found at `borrow` is being borrowed at the point
75 // `borrow_id` for the region `loan_region` with kind `bk`.
77 borrow_id: ast::NodeId,
80 loan_region: ty::Region,
82 loan_cause: LoanCause);
84 // The local variable `id` is declared but not initialized.
85 fn decl_without_init(&mut self,
89 // The path at `cmt` is being assigned to.
91 assignment_id: ast::NodeId,
92 assignment_span: Span,
93 assignee_cmt: mc::cmt<'tcx>,
97 #[derive(Copy, Clone, PartialEq, Debug)]
110 #[derive(Copy, Clone, PartialEq, Debug)]
111 pub enum ConsumeMode {
112 Copy, // reference to x where x has a type that copies
113 Move(MoveReason), // reference to x where x has a type that moves
116 #[derive(Copy, Clone, PartialEq, Debug)]
117 pub enum MoveReason {
123 #[derive(Copy, Clone, PartialEq, Debug)]
131 #[derive(Copy, Clone, PartialEq, Debug)]
132 enum TrackMatchMode {
138 impl TrackMatchMode {
139 // Builds up the whole match mode for a pattern from its constituent
140 // parts. The lattice looks like this:
156 // * `(_, some_int)` pattern is Copying, since
157 // NonBinding + Copying => Copying
159 // * `(some_int, some_box)` pattern is Moving, since
160 // Copying + Moving => Moving
162 // * `(ref x, some_box)` pattern is Conflicting, since
163 // Borrowing + Moving => Conflicting
165 // Note that the `Unknown` and `Conflicting` states are
166 // represented separately from the other more interesting
167 // `Definite` states, which simplifies logic here somewhat.
168 fn lub(&mut self, mode: MatchMode) {
169 *self = match (*self, mode) {
170 // Note that clause order below is very significant.
171 (Unknown, new) => Definite(new),
172 (Definite(old), new) if old == new => Definite(old),
174 (Definite(old), NonBindingMatch) => Definite(old),
175 (Definite(NonBindingMatch), new) => Definite(new),
177 (Definite(old), CopyingMatch) => Definite(old),
178 (Definite(CopyingMatch), new) => Definite(new),
180 (Definite(_), _) => Conflicting,
181 (Conflicting, _) => *self,
185 fn match_mode(&self) -> MatchMode {
187 Unknown => NonBindingMatch,
188 Definite(mode) => mode,
190 // Conservatively return MovingMatch to let the
191 // compiler continue to make progress.
198 #[derive(Copy, Clone, PartialEq, Debug)]
199 pub enum MutateMode {
202 WriteAndRead, // x += y
205 #[derive(Copy, Clone)]
206 enum OverloadedCallType {
209 FnOnceOverloadedCall,
212 impl OverloadedCallType {
213 fn from_trait_id(tcx: &ty::ctxt, trait_id: DefId)
214 -> OverloadedCallType {
215 for &(maybe_function_trait, overloaded_call_type) in &[
216 (tcx.lang_items.fn_once_trait(), FnOnceOverloadedCall),
217 (tcx.lang_items.fn_mut_trait(), FnMutOverloadedCall),
218 (tcx.lang_items.fn_trait(), FnOverloadedCall)
220 match maybe_function_trait {
221 Some(function_trait) if function_trait == trait_id => {
222 return overloaded_call_type
228 tcx.sess.bug("overloaded call didn't map to known function trait")
231 fn from_method_id(tcx: &ty::ctxt, method_id: DefId)
232 -> OverloadedCallType {
233 let method = tcx.impl_or_trait_item(method_id);
234 OverloadedCallType::from_trait_id(tcx, method.container().id())
238 ///////////////////////////////////////////////////////////////////////////
239 // The ExprUseVisitor type
241 // This is the code that actually walks the tree. Like
242 // mem_categorization, it requires a TYPER, which is a type that
243 // supplies types from the tree. After type checking is complete, you
244 // can just use the tcx as the typer.
245 pub struct ExprUseVisitor<'d, 't, 'a: 't, 'tcx:'a+'d> {
246 typer: &'t infer::InferCtxt<'a, 'tcx>,
247 mc: mc::MemCategorizationContext<'t, 'a, 'tcx>,
248 delegate: &'d mut Delegate<'tcx>,
251 // If the TYPER results in an error, it's because the type check
252 // failed (or will fail, when the error is uncovered and reported
253 // during writeback). In this case, we just ignore this part of the
256 // Note that this macro appears similar to try!(), but, unlike try!(),
257 // it does not propagate the error.
258 macro_rules! return_if_err {
263 debug!("mc reported err");
270 /// Whether the elements of an overloaded operation are passed by value or by reference
276 impl<'d,'t,'a,'tcx> ExprUseVisitor<'d,'t,'a,'tcx> {
277 pub fn new(delegate: &'d mut (Delegate<'tcx>+'d),
278 typer: &'t infer::InferCtxt<'a, 'tcx>)
279 -> ExprUseVisitor<'d,'t,'a,'tcx> where 'tcx:'a+'d
281 let mc: mc::MemCategorizationContext<'t, 'a, 'tcx> =
282 mc::MemCategorizationContext::new(typer);
283 ExprUseVisitor { typer: typer, mc: mc, delegate: delegate }
286 pub fn walk_fn(&mut self,
289 self.walk_arg_patterns(decl, body);
290 self.walk_block(body);
293 fn walk_arg_patterns(&mut self,
296 for arg in &decl.inputs {
297 let arg_ty = return_if_err!(self.typer.node_ty(arg.pat.id));
299 let fn_body_scope = self.tcx().region_maps.node_extent(body.id);
300 let arg_cmt = self.mc.cat_rvalue(
303 ty::ReScope(fn_body_scope), // Args live only as long as the fn body.
306 self.walk_irrefutable_pat(arg_cmt, &arg.pat);
310 fn tcx(&self) -> &'t ty::ctxt<'tcx> {
314 fn delegate_consume(&mut self,
315 consume_id: ast::NodeId,
317 cmt: mc::cmt<'tcx>) {
318 debug!("delegate_consume(consume_id={}, cmt={:?})",
321 let mode = copy_or_move(self.typer, &cmt, DirectRefMove);
322 self.delegate.consume(consume_id, consume_span, cmt, mode);
325 fn consume_exprs(&mut self, exprs: &[P<hir::Expr>]) {
327 self.consume_expr(&expr);
331 pub fn consume_expr(&mut self, expr: &hir::Expr) {
332 debug!("consume_expr(expr={:?})", expr);
334 let cmt = return_if_err!(self.mc.cat_expr(expr));
335 self.delegate_consume(expr.id, expr.span, cmt);
336 self.walk_expr(expr);
339 fn mutate_expr(&mut self,
340 assignment_expr: &hir::Expr,
343 let cmt = return_if_err!(self.mc.cat_expr(expr));
344 self.delegate.mutate(assignment_expr.id, assignment_expr.span, cmt, mode);
345 self.walk_expr(expr);
348 fn borrow_expr(&mut self,
353 debug!("borrow_expr(expr={:?}, r={:?}, bk={:?})",
356 let cmt = return_if_err!(self.mc.cat_expr(expr));
357 self.delegate.borrow(expr.id, expr.span, cmt, r, bk, cause);
362 fn select_from_expr(&mut self, expr: &hir::Expr) {
366 pub fn walk_expr(&mut self, expr: &hir::Expr) {
367 debug!("walk_expr(expr={:?})", expr);
369 self.walk_adjustment(expr);
372 hir::ExprPath(..) => { }
374 hir::ExprType(ref subexpr, _) => {
375 self.walk_expr(&subexpr)
378 hir::ExprUnary(hir::UnDeref, ref base) => { // *base
379 if !self.walk_overloaded_operator(expr, &base, Vec::new(), PassArgs::ByRef) {
380 self.select_from_expr(&base);
384 hir::ExprField(ref base, _) => { // base.f
385 self.select_from_expr(&base);
388 hir::ExprTupField(ref base, _) => { // base.<n>
389 self.select_from_expr(&base);
392 hir::ExprIndex(ref lhs, ref rhs) => { // lhs[rhs]
393 if !self.walk_overloaded_operator(expr,
397 self.select_from_expr(&lhs);
398 self.consume_expr(&rhs);
402 hir::ExprCall(ref callee, ref args) => { // callee(args)
403 self.walk_callee(expr, &callee);
404 self.consume_exprs(args);
407 hir::ExprMethodCall(_, _, ref args) => { // callee.m(args)
408 self.consume_exprs(args);
411 hir::ExprStruct(_, ref fields, ref opt_with) => {
412 self.walk_struct_expr(expr, fields, opt_with);
415 hir::ExprTup(ref exprs) => {
416 self.consume_exprs(exprs);
419 hir::ExprIf(ref cond_expr, ref then_blk, ref opt_else_expr) => {
420 self.consume_expr(&cond_expr);
421 self.walk_block(&then_blk);
422 if let Some(ref else_expr) = *opt_else_expr {
423 self.consume_expr(&else_expr);
427 hir::ExprMatch(ref discr, ref arms, _) => {
428 let discr_cmt = return_if_err!(self.mc.cat_expr(&discr));
429 self.borrow_expr(&discr, ty::ReEmpty, ty::ImmBorrow, MatchDiscriminant);
431 // treatment of the discriminant is handled while walking the arms.
433 let mode = self.arm_move_mode(discr_cmt.clone(), arm);
434 let mode = mode.match_mode();
435 self.walk_arm(discr_cmt.clone(), arm, mode);
439 hir::ExprVec(ref exprs) => {
440 self.consume_exprs(exprs);
443 hir::ExprAddrOf(m, ref base) => { // &base
444 // make sure that the thing we are pointing out stays valid
445 // for the lifetime `scope_r` of the resulting ptr:
446 let expr_ty = return_if_err!(self.typer.node_ty(expr.id));
447 if let ty::TyRef(&r, _) = expr_ty.sty {
448 let bk = ty::BorrowKind::from_mutbl(m);
449 self.borrow_expr(&base, r, bk, AddrOf);
453 hir::ExprInlineAsm(ref ia) => {
454 for &(_, ref input) in &ia.inputs {
455 self.consume_expr(&input);
458 for output in &ia.outputs {
459 if output.is_indirect {
460 self.consume_expr(&output.expr);
462 self.mutate_expr(expr, &output.expr,
464 MutateMode::WriteAndRead
466 MutateMode::JustWrite
474 hir::ExprLit(..) => {}
476 hir::ExprLoop(ref blk, _) => {
477 self.walk_block(&blk);
480 hir::ExprWhile(ref cond_expr, ref blk, _) => {
481 self.consume_expr(&cond_expr);
482 self.walk_block(&blk);
485 hir::ExprUnary(op, ref lhs) => {
486 let pass_args = if ::rustc_front::util::is_by_value_unop(op) {
492 if !self.walk_overloaded_operator(expr, &lhs, Vec::new(), pass_args) {
493 self.consume_expr(&lhs);
497 hir::ExprBinary(op, ref lhs, ref rhs) => {
498 let pass_args = if ::rustc_front::util::is_by_value_binop(op.node) {
504 if !self.walk_overloaded_operator(expr, &lhs, vec![&rhs], pass_args) {
505 self.consume_expr(&lhs);
506 self.consume_expr(&rhs);
510 hir::ExprBlock(ref blk) => {
511 self.walk_block(&blk);
514 hir::ExprRet(ref opt_expr) => {
515 if let Some(ref expr) = *opt_expr {
516 self.consume_expr(&expr);
520 hir::ExprAssign(ref lhs, ref rhs) => {
521 self.mutate_expr(expr, &lhs, MutateMode::JustWrite);
522 self.consume_expr(&rhs);
525 hir::ExprCast(ref base, _) => {
526 self.consume_expr(&base);
529 hir::ExprAssignOp(op, ref lhs, ref rhs) => {
530 // NB All our assignment operations take the RHS by value
531 assert!(::rustc_front::util::is_by_value_binop(op.node));
533 if !self.walk_overloaded_operator(expr, lhs, vec![rhs], PassArgs::ByValue) {
534 self.mutate_expr(expr, &lhs, MutateMode::WriteAndRead);
535 self.consume_expr(&rhs);
539 hir::ExprRepeat(ref base, ref count) => {
540 self.consume_expr(&base);
541 self.consume_expr(&count);
544 hir::ExprClosure(..) => {
545 self.walk_captures(expr)
548 hir::ExprBox(ref base) => {
549 self.consume_expr(&base);
554 fn walk_callee(&mut self, call: &hir::Expr, callee: &hir::Expr) {
555 let callee_ty = return_if_err!(self.typer.expr_ty_adjusted(callee));
556 debug!("walk_callee: callee={:?} callee_ty={:?}",
558 let call_scope = self.tcx().region_maps.node_extent(call.id);
559 match callee_ty.sty {
560 ty::TyBareFn(..) => {
561 self.consume_expr(callee);
565 let overloaded_call_type =
566 match self.typer.node_method_id(ty::MethodCall::expr(call.id)) {
568 OverloadedCallType::from_method_id(self.tcx(), method_id)
571 self.tcx().sess.span_bug(
573 &format!("unexpected callee type {}", callee_ty))
576 match overloaded_call_type {
577 FnMutOverloadedCall => {
578 self.borrow_expr(callee,
579 ty::ReScope(call_scope),
583 FnOverloadedCall => {
584 self.borrow_expr(callee,
585 ty::ReScope(call_scope),
589 FnOnceOverloadedCall => self.consume_expr(callee),
595 fn walk_stmt(&mut self, stmt: &hir::Stmt) {
597 hir::StmtDecl(ref decl, _) => {
599 hir::DeclLocal(ref local) => {
600 self.walk_local(&local);
603 hir::DeclItem(_) => {
604 // we don't visit nested items in this visitor,
605 // only the fn body we were given.
610 hir::StmtExpr(ref expr, _) |
611 hir::StmtSemi(ref expr, _) => {
612 self.consume_expr(&expr);
617 fn walk_local(&mut self, local: &hir::Local) {
620 let delegate = &mut self.delegate;
621 pat_util::pat_bindings(&self.typer.tcx.def_map, &local.pat,
623 delegate.decl_without_init(id, span);
628 // Variable declarations with
629 // initializers are considered
630 // "assigns", which is handled by
632 self.walk_expr(&expr);
633 let init_cmt = return_if_err!(self.mc.cat_expr(&expr));
634 self.walk_irrefutable_pat(init_cmt, &local.pat);
639 /// Indicates that the value of `blk` will be consumed, meaning either copied or moved
640 /// depending on its type.
641 fn walk_block(&mut self, blk: &hir::Block) {
642 debug!("walk_block(blk.id={})", blk.id);
644 for stmt in &blk.stmts {
645 self.walk_stmt(stmt);
648 if let Some(ref tail_expr) = blk.expr {
649 self.consume_expr(&tail_expr);
653 fn walk_struct_expr(&mut self,
655 fields: &[hir::Field],
656 opt_with: &Option<P<hir::Expr>>) {
657 // Consume the expressions supplying values for each field.
658 for field in fields {
659 self.consume_expr(&field.expr);
662 let with_expr = match *opt_with {
667 let with_cmt = return_if_err!(self.mc.cat_expr(&with_expr));
669 // Select just those fields of the `with`
670 // expression that will actually be used
671 if let ty::TyStruct(def, substs) = with_cmt.ty.sty {
672 // Consume those fields of the with expression that are needed.
673 for with_field in &def.struct_variant().fields {
674 if !contains_field_named(with_field, fields) {
675 let cmt_field = self.mc.cat_field(
679 with_field.ty(self.tcx(), substs)
681 self.delegate_consume(with_expr.id, with_expr.span, cmt_field);
685 // the base expression should always evaluate to a
686 // struct; however, when EUV is run during typeck, it
687 // may not. This will generate an error earlier in typeck,
688 // so we can just ignore it.
689 if !self.tcx().sess.has_errors() {
690 self.tcx().sess.span_bug(
692 "with expression doesn't evaluate to a struct");
696 // walk the with expression so that complex expressions
697 // are properly handled.
698 self.walk_expr(with_expr);
700 fn contains_field_named(field: ty::FieldDef,
701 fields: &[hir::Field])
705 |f| f.name.node == field.name)
709 // Invoke the appropriate delegate calls for anything that gets
710 // consumed or borrowed as part of the automatic adjustment
712 fn walk_adjustment(&mut self, expr: &hir::Expr) {
713 let typer = self.typer;
714 //NOTE(@jroesch): mixed RefCell borrow causes crash
715 let adj = typer.adjustments().get(&expr.id).map(|x| x.clone());
716 if let Some(adjustment) = adj {
718 adjustment::AdjustReifyFnPointer |
719 adjustment::AdjustUnsafeFnPointer |
720 adjustment::AdjustMutToConstPointer => {
721 // Creating a closure/fn-pointer or unsizing consumes
722 // the input and stores it into the resulting rvalue.
723 debug!("walk_adjustment: trivial adjustment");
725 return_if_err!(self.mc.cat_expr_unadjusted(expr));
726 self.delegate_consume(expr.id, expr.span, cmt_unadjusted);
728 adjustment::AdjustDerefRef(ref adj) => {
729 self.walk_autoderefref(expr, adj);
735 /// Autoderefs for overloaded Deref calls in fact reference their receiver. That is, if we have
736 /// `(*x)` where `x` is of type `Rc<T>`, then this in fact is equivalent to `x.deref()`. Since
737 /// `deref()` is declared with `&self`, this is an autoref of `x`.
738 fn walk_autoderefs(&mut self,
741 debug!("walk_autoderefs expr={:?} autoderefs={}", expr, autoderefs);
743 for i in 0..autoderefs {
744 let deref_id = ty::MethodCall::autoderef(expr.id, i as u32);
745 match self.typer.node_method_ty(deref_id) {
748 let cmt = return_if_err!(self.mc.cat_expr_autoderefd(expr, i));
750 // the method call infrastructure should have
751 // replaced all late-bound regions with variables:
752 let self_ty = method_ty.fn_sig().input(0);
753 let self_ty = self.tcx().no_late_bound_regions(&self_ty).unwrap();
755 let (m, r) = match self_ty.sty {
756 ty::TyRef(r, ref m) => (m.mutbl, r),
757 _ => self.tcx().sess.span_bug(expr.span,
758 &format!("bad overloaded deref type {:?}",
761 let bk = ty::BorrowKind::from_mutbl(m);
762 self.delegate.borrow(expr.id, expr.span, cmt,
769 fn walk_autoderefref(&mut self,
771 adj: &adjustment::AutoDerefRef<'tcx>) {
772 debug!("walk_autoderefref expr={:?} adj={:?}",
776 self.walk_autoderefs(expr, adj.autoderefs);
779 return_if_err!(self.mc.cat_expr_autoderefd(expr, adj.autoderefs));
782 self.walk_autoref(expr, cmt_derefd, adj.autoref);
784 if adj.unsize.is_some() {
785 // Unsizing consumes the thin pointer and produces a fat one.
786 self.delegate_consume(expr.id, expr.span, cmt_refd);
791 /// Walks the autoref `opt_autoref` applied to the autoderef'd
792 /// `expr`. `cmt_derefd` is the mem-categorized form of `expr`
793 /// after all relevant autoderefs have occurred. Because AutoRefs
794 /// can be recursive, this function is recursive: it first walks
795 /// deeply all the way down the autoref chain, and then processes
796 /// the autorefs on the way out. At each point, it returns the
797 /// `cmt` for the rvalue that will be produced by introduced an
799 fn walk_autoref(&mut self,
801 cmt_base: mc::cmt<'tcx>,
802 opt_autoref: Option<adjustment::AutoRef<'tcx>>)
805 debug!("walk_autoref(expr.id={} cmt_derefd={:?} opt_autoref={:?})",
810 let cmt_base_ty = cmt_base.ty;
812 let autoref = match opt_autoref {
813 Some(ref autoref) => autoref,
821 adjustment::AutoPtr(r, m) => {
822 self.delegate.borrow(expr.id,
826 ty::BorrowKind::from_mutbl(m),
830 adjustment::AutoUnsafe(m) => {
831 debug!("walk_autoref: expr.id={} cmt_base={:?}",
835 // Converting from a &T to *T (or &mut T to *mut T) is
836 // treated as borrowing it for the enclosing temporary
838 let r = ty::ReScope(self.tcx().region_maps.node_extent(expr.id));
840 self.delegate.borrow(expr.id,
844 ty::BorrowKind::from_mutbl(m),
849 // Construct the categorization for the result of the autoref.
850 // This is always an rvalue, since we are producing a new
851 // (temporary) indirection.
853 let adj_ty = cmt_base_ty.adjust_for_autoref(self.tcx(), opt_autoref);
855 self.mc.cat_rvalue_node(expr.id, expr.span, adj_ty)
859 // When this returns true, it means that the expression *is* a
860 // method-call (i.e. via the operator-overload). This true result
861 // also implies that walk_overloaded_operator already took care of
862 // recursively processing the input arguments, and thus the caller
864 fn walk_overloaded_operator(&mut self,
866 receiver: &hir::Expr,
867 rhs: Vec<&hir::Expr>,
871 if !self.typer.is_method_call(expr.id) {
876 PassArgs::ByValue => {
877 self.consume_expr(receiver);
879 self.consume_expr(arg);
884 PassArgs::ByRef => {},
887 self.walk_expr(receiver);
889 // Arguments (but not receivers) to overloaded operator
890 // methods are implicitly autoref'd which sadly does not use
891 // adjustments, so we must hardcode the borrow here.
893 let r = ty::ReScope(self.tcx().region_maps.node_extent(expr.id));
894 let bk = ty::ImmBorrow;
897 self.borrow_expr(arg, r, bk, OverloadedOperator);
902 fn arm_move_mode(&mut self, discr_cmt: mc::cmt<'tcx>, arm: &hir::Arm) -> TrackMatchMode {
903 let mut mode = Unknown;
904 for pat in &arm.pats {
905 self.determine_pat_move_mode(discr_cmt.clone(), &pat, &mut mode);
910 fn walk_arm(&mut self, discr_cmt: mc::cmt<'tcx>, arm: &hir::Arm, mode: MatchMode) {
911 for pat in &arm.pats {
912 self.walk_pat(discr_cmt.clone(), &pat, mode);
915 if let Some(ref guard) = arm.guard {
916 self.consume_expr(&guard);
919 self.consume_expr(&arm.body);
922 /// Walks a pat that occurs in isolation (i.e. top-level of fn
923 /// arg or let binding. *Not* a match arm or nested pat.)
924 fn walk_irrefutable_pat(&mut self, cmt_discr: mc::cmt<'tcx>, pat: &hir::Pat) {
925 let mut mode = Unknown;
926 self.determine_pat_move_mode(cmt_discr.clone(), pat, &mut mode);
927 let mode = mode.match_mode();
928 self.walk_pat(cmt_discr, pat, mode);
931 /// Identifies any bindings within `pat` and accumulates within
932 /// `mode` whether the overall pattern/match structure is a move,
934 fn determine_pat_move_mode(&mut self,
935 cmt_discr: mc::cmt<'tcx>,
937 mode: &mut TrackMatchMode) {
938 debug!("determine_pat_move_mode cmt_discr={:?} pat={:?}", cmt_discr,
940 return_if_err!(self.mc.cat_pattern(cmt_discr, pat, |_mc, cmt_pat, pat| {
941 let tcx = self.tcx();
942 let def_map = &self.tcx().def_map;
943 if pat_util::pat_is_binding(&def_map.borrow(), pat) {
945 PatKind::Ident(hir::BindByRef(_), _, _) =>
946 mode.lub(BorrowingMatch),
947 PatKind::Ident(hir::BindByValue(_), _, _) => {
948 match copy_or_move(self.typer, &cmt_pat, PatBindingMove) {
949 Copy => mode.lub(CopyingMatch),
950 Move(_) => mode.lub(MovingMatch),
956 "binding pattern not an identifier");
963 /// The core driver for walking a pattern; `match_mode` must be
964 /// established up front, e.g. via `determine_pat_move_mode` (see
965 /// also `walk_irrefutable_pat` for patterns that stand alone).
966 fn walk_pat(&mut self,
967 cmt_discr: mc::cmt<'tcx>,
969 match_mode: MatchMode) {
970 debug!("walk_pat cmt_discr={:?} pat={:?}", cmt_discr,
974 let typer = self.typer;
975 let def_map = &self.tcx().def_map;
976 let delegate = &mut self.delegate;
977 return_if_err!(mc.cat_pattern(cmt_discr.clone(), pat, |mc, cmt_pat, pat| {
978 if pat_util::pat_is_binding(&def_map.borrow(), pat) {
981 debug!("binding cmt_pat={:?} pat={:?} match_mode={:?}",
986 // pat_ty: the type of the binding being produced.
987 let pat_ty = return_if_err!(typer.node_ty(pat.id));
989 // Each match binding is effectively an assignment to the
990 // binding being produced.
991 let def = def_map.borrow().get(&pat.id).unwrap().full_def();
992 match mc.cat_def(pat.id, pat.span, pat_ty, def) {
994 delegate.mutate(pat.id, pat.span, binding_cmt, MutateMode::Init);
999 // It is also a borrow or copy/move of the value being matched.
1001 PatKind::Ident(hir::BindByRef(m), _, _) => {
1002 if let ty::TyRef(&r, _) = pat_ty.sty {
1003 let bk = ty::BorrowKind::from_mutbl(m);
1004 delegate.borrow(pat.id, pat.span, cmt_pat,
1008 PatKind::Ident(hir::BindByValue(_), _, _) => {
1009 let mode = copy_or_move(typer, &cmt_pat, PatBindingMove);
1010 debug!("walk_pat binding consuming pat");
1011 delegate.consume_pat(pat, cmt_pat, mode);
1016 "binding pattern not an identifier");
1021 PatKind::Vec(_, Some(ref slice_pat), _) => {
1022 // The `slice_pat` here creates a slice into
1023 // the original vector. This is effectively a
1024 // borrow of the elements of the vector being
1027 let (slice_cmt, slice_mutbl, slice_r) =
1028 return_if_err!(mc.cat_slice_pattern(cmt_pat, &slice_pat));
1030 // Note: We declare here that the borrow
1031 // occurs upon entering the `[...]`
1032 // pattern. This implies that something like
1033 // `[a; b]` where `a` is a move is illegal,
1034 // because the borrow is already in effect.
1035 // In fact such a move would be safe-ish, but
1036 // it effectively *requires* that we use the
1037 // nulling out semantics to indicate when a
1038 // value has been moved, which we are trying
1039 // to move away from. Otherwise, how can we
1040 // indicate that the first element in the
1041 // vector has been moved? Eventually, we
1042 // could perhaps modify this rule to permit
1043 // `[..a, b]` where `b` is a move, because in
1044 // that case we can adjust the length of the
1045 // original vec accordingly, but we'd have to
1046 // make trans do the right thing, and it would
1047 // only work for `Box<[T]>`s. It seems simpler
1048 // to just require that people call
1049 // `vec.pop()` or `vec.unshift()`.
1050 let slice_bk = ty::BorrowKind::from_mutbl(slice_mutbl);
1051 delegate.borrow(pat.id, pat.span,
1053 slice_bk, RefBinding);
1060 // Do a second pass over the pattern, calling `matched_pat` on
1061 // the interior nodes (enum variants and structs), as opposed
1062 // to the above loop's visit of than the bindings that form
1063 // the leaves of the pattern tree structure.
1064 return_if_err!(mc.cat_pattern(cmt_discr, pat, |mc, cmt_pat, pat| {
1065 let def_map = def_map.borrow();
1066 let tcx = typer.tcx;
1069 PatKind::TupleStruct(..) | PatKind::Path(..) | PatKind::QPath(..) |
1070 PatKind::Ident(_, _, None) | PatKind::Struct(..) => {
1071 match def_map.get(&pat.id).map(|d| d.full_def()) {
1073 // no definition found: pat is not a
1074 // struct or enum pattern.
1077 Some(Def::Variant(enum_did, variant_did)) => {
1079 if tcx.lookup_adt_def(enum_did).is_univariant() {
1082 let cmt_pat_ty = cmt_pat.ty;
1083 mc.cat_downcast(pat, cmt_pat, cmt_pat_ty, variant_did)
1086 debug!("variant downcast_cmt={:?} pat={:?}",
1090 delegate.matched_pat(pat, downcast_cmt, match_mode);
1093 Some(Def::Struct(..)) | Some(Def::TyAlias(..)) => {
1094 // A struct (in either the value or type
1095 // namespace; we encounter the former on
1096 // e.g. patterns for unit structs).
1098 debug!("struct cmt_pat={:?} pat={:?}",
1102 delegate.matched_pat(pat, cmt_pat, match_mode);
1105 Some(Def::Const(..)) |
1106 Some(Def::AssociatedConst(..)) |
1107 Some(Def::Local(..)) => {
1108 // This is a leaf (i.e. identifier binding
1109 // or constant value to match); thus no
1110 // `matched_pat` call.
1114 // An enum type should never be in a pattern.
1115 // Remaining cases are e.g. Def::Fn, to
1116 // which identifiers within patterns
1117 // should not resolve. However, we do
1118 // encouter this when using the
1119 // expr-use-visitor during typeck. So just
1120 // ignore it, an error should have been
1123 if !tcx.sess.has_errors() {
1124 let msg = format!("Pattern has unexpected def: {:?} and type {:?}",
1127 tcx.sess.span_bug(pat.span, &msg[..])
1133 PatKind::Ident(_, _, Some(_)) => {
1134 // Do nothing; this is a binding (not an enum
1135 // variant or struct), and the cat_pattern call
1136 // will visit the substructure recursively.
1139 PatKind::Wild | PatKind::Tup(..) | PatKind::Box(..) |
1140 PatKind::Ref(..) | PatKind::Lit(..) | PatKind::Range(..) |
1141 PatKind::Vec(..) => {
1142 // Similarly, each of these cases does not
1143 // correspond to an enum variant or struct, so we
1144 // do not do any `matched_pat` calls for these
1151 fn walk_captures(&mut self, closure_expr: &hir::Expr) {
1152 debug!("walk_captures({:?})", closure_expr);
1154 self.tcx().with_freevars(closure_expr.id, |freevars| {
1155 for freevar in freevars {
1156 let id_var = freevar.def.var_id();
1157 let upvar_id = ty::UpvarId { var_id: id_var,
1158 closure_expr_id: closure_expr.id };
1159 let upvar_capture = self.typer.upvar_capture(upvar_id).unwrap();
1160 let cmt_var = return_if_err!(self.cat_captured_var(closure_expr.id,
1163 match upvar_capture {
1164 ty::UpvarCapture::ByValue => {
1165 let mode = copy_or_move(self.typer, &cmt_var, CaptureMove);
1166 self.delegate.consume(closure_expr.id, freevar.span, cmt_var, mode);
1168 ty::UpvarCapture::ByRef(upvar_borrow) => {
1169 self.delegate.borrow(closure_expr.id,
1172 upvar_borrow.region,
1174 ClosureCapture(freevar.span));
1181 fn cat_captured_var(&mut self,
1182 closure_id: ast::NodeId,
1185 -> mc::McResult<mc::cmt<'tcx>> {
1186 // Create the cmt for the variable being borrowed, from the
1187 // caller's perspective
1188 let var_id = upvar_def.var_id();
1189 let var_ty = try!(self.typer.node_ty(var_id));
1190 self.mc.cat_def(closure_id, closure_span, var_ty, upvar_def)
1194 fn copy_or_move<'a, 'tcx>(typer: &infer::InferCtxt<'a, 'tcx>,
1195 cmt: &mc::cmt<'tcx>,
1196 move_reason: MoveReason)
1199 if typer.type_moves_by_default(cmt.ty, cmt.span) {