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;
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::ExprRange(ref start, ref end) => {
403 start.as_ref().map(|e| self.consume_expr(&**e));
404 end.as_ref().map(|e| self.consume_expr(&**e));
407 hir::ExprCall(ref callee, ref args) => { // callee(args)
408 self.walk_callee(expr, &**callee);
409 self.consume_exprs(args);
412 hir::ExprMethodCall(_, _, ref args) => { // callee.m(args)
413 self.consume_exprs(args);
416 hir::ExprStruct(_, ref fields, ref opt_with) => {
417 self.walk_struct_expr(expr, fields, opt_with);
420 hir::ExprTup(ref exprs) => {
421 self.consume_exprs(exprs);
424 hir::ExprIf(ref cond_expr, ref then_blk, ref opt_else_expr) => {
425 self.consume_expr(&**cond_expr);
426 self.walk_block(&**then_blk);
427 if let Some(ref else_expr) = *opt_else_expr {
428 self.consume_expr(&**else_expr);
432 hir::ExprMatch(ref discr, ref arms, _) => {
433 let discr_cmt = return_if_err!(self.mc.cat_expr(&**discr));
434 self.borrow_expr(&**discr, ty::ReEmpty, ty::ImmBorrow, MatchDiscriminant);
436 // treatment of the discriminant is handled while walking the arms.
438 let mode = self.arm_move_mode(discr_cmt.clone(), arm);
439 let mode = mode.match_mode();
440 self.walk_arm(discr_cmt.clone(), arm, mode);
444 hir::ExprVec(ref exprs) => {
445 self.consume_exprs(exprs);
448 hir::ExprAddrOf(m, ref base) => { // &base
449 // make sure that the thing we are pointing out stays valid
450 // for the lifetime `scope_r` of the resulting ptr:
451 let expr_ty = return_if_err!(self.typer.node_ty(expr.id));
452 if let ty::TyRef(&r, _) = expr_ty.sty {
453 let bk = ty::BorrowKind::from_mutbl(m);
454 self.borrow_expr(&**base, r, bk, AddrOf);
458 hir::ExprInlineAsm(ref ia) => {
459 for &(_, ref input) in &ia.inputs {
460 self.consume_expr(&**input);
463 for output in &ia.outputs {
464 if output.is_indirect {
465 self.consume_expr(&*output.expr);
467 self.mutate_expr(expr, &*output.expr,
469 MutateMode::WriteAndRead
471 MutateMode::JustWrite
479 hir::ExprLit(..) => {}
481 hir::ExprLoop(ref blk, _) => {
482 self.walk_block(&**blk);
485 hir::ExprWhile(ref cond_expr, ref blk, _) => {
486 self.consume_expr(&**cond_expr);
487 self.walk_block(&**blk);
490 hir::ExprUnary(op, ref lhs) => {
491 let pass_args = if ::rustc_front::util::is_by_value_unop(op) {
497 if !self.walk_overloaded_operator(expr, &**lhs, Vec::new(), pass_args) {
498 self.consume_expr(&**lhs);
502 hir::ExprBinary(op, ref lhs, ref rhs) => {
503 let pass_args = if ::rustc_front::util::is_by_value_binop(op.node) {
509 if !self.walk_overloaded_operator(expr, &**lhs, vec![&**rhs], pass_args) {
510 self.consume_expr(&**lhs);
511 self.consume_expr(&**rhs);
515 hir::ExprBlock(ref blk) => {
516 self.walk_block(&**blk);
519 hir::ExprRet(ref opt_expr) => {
520 if let Some(ref expr) = *opt_expr {
521 self.consume_expr(&**expr);
525 hir::ExprAssign(ref lhs, ref rhs) => {
526 self.mutate_expr(expr, &**lhs, MutateMode::JustWrite);
527 self.consume_expr(&**rhs);
530 hir::ExprCast(ref base, _) => {
531 self.consume_expr(&**base);
534 hir::ExprAssignOp(op, ref lhs, ref rhs) => {
535 // NB All our assignment operations take the RHS by value
536 assert!(::rustc_front::util::is_by_value_binop(op.node));
538 if !self.walk_overloaded_operator(expr, lhs, vec![rhs], PassArgs::ByValue) {
539 self.mutate_expr(expr, &**lhs, MutateMode::WriteAndRead);
540 self.consume_expr(&**rhs);
544 hir::ExprRepeat(ref base, ref count) => {
545 self.consume_expr(&**base);
546 self.consume_expr(&**count);
549 hir::ExprClosure(..) => {
550 self.walk_captures(expr)
553 hir::ExprBox(ref base) => {
554 self.consume_expr(&**base);
559 fn walk_callee(&mut self, call: &hir::Expr, callee: &hir::Expr) {
560 let callee_ty = return_if_err!(self.typer.expr_ty_adjusted(callee));
561 debug!("walk_callee: callee={:?} callee_ty={:?}",
563 let call_scope = self.tcx().region_maps.node_extent(call.id);
564 match callee_ty.sty {
565 ty::TyBareFn(..) => {
566 self.consume_expr(callee);
570 let overloaded_call_type =
571 match self.typer.node_method_id(ty::MethodCall::expr(call.id)) {
573 OverloadedCallType::from_method_id(self.tcx(), method_id)
576 self.tcx().sess.span_bug(
578 &format!("unexpected callee type {}", callee_ty))
581 match overloaded_call_type {
582 FnMutOverloadedCall => {
583 self.borrow_expr(callee,
584 ty::ReScope(call_scope),
588 FnOverloadedCall => {
589 self.borrow_expr(callee,
590 ty::ReScope(call_scope),
594 FnOnceOverloadedCall => self.consume_expr(callee),
600 fn walk_stmt(&mut self, stmt: &hir::Stmt) {
602 hir::StmtDecl(ref decl, _) => {
604 hir::DeclLocal(ref local) => {
605 self.walk_local(&**local);
608 hir::DeclItem(_) => {
609 // we don't visit nested items in this visitor,
610 // only the fn body we were given.
615 hir::StmtExpr(ref expr, _) |
616 hir::StmtSemi(ref expr, _) => {
617 self.consume_expr(&**expr);
622 fn walk_local(&mut self, local: &hir::Local) {
625 let delegate = &mut self.delegate;
626 pat_util::pat_bindings(&self.typer.tcx.def_map, &*local.pat,
628 delegate.decl_without_init(id, span);
633 // Variable declarations with
634 // initializers are considered
635 // "assigns", which is handled by
637 self.walk_expr(&**expr);
638 let init_cmt = return_if_err!(self.mc.cat_expr(&**expr));
639 self.walk_irrefutable_pat(init_cmt, &*local.pat);
644 /// Indicates that the value of `blk` will be consumed, meaning either copied or moved
645 /// depending on its type.
646 fn walk_block(&mut self, blk: &hir::Block) {
647 debug!("walk_block(blk.id={})", blk.id);
649 for stmt in &blk.stmts {
650 self.walk_stmt(stmt);
653 if let Some(ref tail_expr) = blk.expr {
654 self.consume_expr(&**tail_expr);
658 fn walk_struct_expr(&mut self,
660 fields: &[hir::Field],
661 opt_with: &Option<P<hir::Expr>>) {
662 // Consume the expressions supplying values for each field.
663 for field in fields {
664 self.consume_expr(&*field.expr);
667 let with_expr = match *opt_with {
672 let with_cmt = return_if_err!(self.mc.cat_expr(&*with_expr));
674 // Select just those fields of the `with`
675 // expression that will actually be used
676 if let ty::TyStruct(def, substs) = with_cmt.ty.sty {
677 // Consume those fields of the with expression that are needed.
678 for with_field in &def.struct_variant().fields {
679 if !contains_field_named(with_field, fields) {
680 let cmt_field = self.mc.cat_field(
684 with_field.ty(self.tcx(), substs)
686 self.delegate_consume(with_expr.id, with_expr.span, cmt_field);
690 // the base expression should always evaluate to a
691 // struct; however, when EUV is run during typeck, it
692 // may not. This will generate an error earlier in typeck,
693 // so we can just ignore it.
694 if !self.tcx().sess.has_errors() {
695 self.tcx().sess.span_bug(
697 "with expression doesn't evaluate to a struct");
701 // walk the with expression so that complex expressions
702 // are properly handled.
703 self.walk_expr(with_expr);
705 fn contains_field_named(field: ty::FieldDef,
706 fields: &[hir::Field])
710 |f| f.name.node == field.name)
714 // Invoke the appropriate delegate calls for anything that gets
715 // consumed or borrowed as part of the automatic adjustment
717 fn walk_adjustment(&mut self, expr: &hir::Expr) {
718 let typer = self.typer;
719 //NOTE(@jroesch): mixed RefCell borrow causes crash
720 let adj = typer.adjustments().get(&expr.id).map(|x| x.clone());
721 if let Some(adjustment) = adj {
723 adjustment::AdjustReifyFnPointer |
724 adjustment::AdjustUnsafeFnPointer => {
725 // Creating a closure/fn-pointer or unsizing consumes
726 // the input and stores it into the resulting rvalue.
727 debug!("walk_adjustment(AdjustReifyFnPointer|AdjustUnsafeFnPointer)");
729 return_if_err!(self.mc.cat_expr_unadjusted(expr));
730 self.delegate_consume(expr.id, expr.span, cmt_unadjusted);
732 adjustment::AdjustDerefRef(ref adj) => {
733 self.walk_autoderefref(expr, adj);
739 /// Autoderefs for overloaded Deref calls in fact reference their receiver. That is, if we have
740 /// `(*x)` where `x` is of type `Rc<T>`, then this in fact is equivalent to `x.deref()`. Since
741 /// `deref()` is declared with `&self`, this is an autoref of `x`.
742 fn walk_autoderefs(&mut self,
745 debug!("walk_autoderefs expr={:?} autoderefs={}", expr, autoderefs);
747 for i in 0..autoderefs {
748 let deref_id = ty::MethodCall::autoderef(expr.id, i as u32);
749 match self.typer.node_method_ty(deref_id) {
752 let cmt = return_if_err!(self.mc.cat_expr_autoderefd(expr, i));
754 // the method call infrastructure should have
755 // replaced all late-bound regions with variables:
756 let self_ty = method_ty.fn_sig().input(0);
757 let self_ty = self.tcx().no_late_bound_regions(&self_ty).unwrap();
759 let (m, r) = match self_ty.sty {
760 ty::TyRef(r, ref m) => (m.mutbl, r),
761 _ => self.tcx().sess.span_bug(expr.span,
762 &format!("bad overloaded deref type {:?}",
765 let bk = ty::BorrowKind::from_mutbl(m);
766 self.delegate.borrow(expr.id, expr.span, cmt,
773 fn walk_autoderefref(&mut self,
775 adj: &adjustment::AutoDerefRef<'tcx>) {
776 debug!("walk_autoderefref expr={:?} adj={:?}",
780 self.walk_autoderefs(expr, adj.autoderefs);
783 return_if_err!(self.mc.cat_expr_autoderefd(expr, adj.autoderefs));
786 self.walk_autoref(expr, cmt_derefd, adj.autoref);
788 if adj.unsize.is_some() {
789 // Unsizing consumes the thin pointer and produces a fat one.
790 self.delegate_consume(expr.id, expr.span, cmt_refd);
795 /// Walks the autoref `opt_autoref` applied to the autoderef'd
796 /// `expr`. `cmt_derefd` is the mem-categorized form of `expr`
797 /// after all relevant autoderefs have occurred. Because AutoRefs
798 /// can be recursive, this function is recursive: it first walks
799 /// deeply all the way down the autoref chain, and then processes
800 /// the autorefs on the way out. At each point, it returns the
801 /// `cmt` for the rvalue that will be produced by introduced an
803 fn walk_autoref(&mut self,
805 cmt_base: mc::cmt<'tcx>,
806 opt_autoref: Option<adjustment::AutoRef<'tcx>>)
809 debug!("walk_autoref(expr.id={} cmt_derefd={:?} opt_autoref={:?})",
814 let cmt_base_ty = cmt_base.ty;
816 let autoref = match opt_autoref {
817 Some(ref autoref) => autoref,
825 adjustment::AutoPtr(r, m) => {
826 self.delegate.borrow(expr.id,
830 ty::BorrowKind::from_mutbl(m),
834 adjustment::AutoUnsafe(m) => {
835 debug!("walk_autoref: expr.id={} cmt_base={:?}",
839 // Converting from a &T to *T (or &mut T to *mut T) is
840 // treated as borrowing it for the enclosing temporary
842 let r = ty::ReScope(self.tcx().region_maps.node_extent(expr.id));
844 self.delegate.borrow(expr.id,
848 ty::BorrowKind::from_mutbl(m),
853 // Construct the categorization for the result of the autoref.
854 // This is always an rvalue, since we are producing a new
855 // (temporary) indirection.
857 let adj_ty = cmt_base_ty.adjust_for_autoref(self.tcx(), opt_autoref);
859 self.mc.cat_rvalue_node(expr.id, expr.span, adj_ty)
863 // When this returns true, it means that the expression *is* a
864 // method-call (i.e. via the operator-overload). This true result
865 // also implies that walk_overloaded_operator already took care of
866 // recursively processing the input arguments, and thus the caller
868 fn walk_overloaded_operator(&mut self,
870 receiver: &hir::Expr,
871 rhs: Vec<&hir::Expr>,
875 if !self.typer.is_method_call(expr.id) {
880 PassArgs::ByValue => {
881 self.consume_expr(receiver);
883 self.consume_expr(arg);
888 PassArgs::ByRef => {},
891 self.walk_expr(receiver);
893 // Arguments (but not receivers) to overloaded operator
894 // methods are implicitly autoref'd which sadly does not use
895 // adjustments, so we must hardcode the borrow here.
897 let r = ty::ReScope(self.tcx().region_maps.node_extent(expr.id));
898 let bk = ty::ImmBorrow;
901 self.borrow_expr(arg, r, bk, OverloadedOperator);
906 fn arm_move_mode(&mut self, discr_cmt: mc::cmt<'tcx>, arm: &hir::Arm) -> TrackMatchMode {
907 let mut mode = Unknown;
908 for pat in &arm.pats {
909 self.determine_pat_move_mode(discr_cmt.clone(), &**pat, &mut mode);
914 fn walk_arm(&mut self, discr_cmt: mc::cmt<'tcx>, arm: &hir::Arm, mode: MatchMode) {
915 for pat in &arm.pats {
916 self.walk_pat(discr_cmt.clone(), &**pat, mode);
919 if let Some(ref guard) = arm.guard {
920 self.consume_expr(&**guard);
923 self.consume_expr(&*arm.body);
926 /// Walks a pat that occurs in isolation (i.e. top-level of fn
927 /// arg or let binding. *Not* a match arm or nested pat.)
928 fn walk_irrefutable_pat(&mut self, cmt_discr: mc::cmt<'tcx>, pat: &hir::Pat) {
929 let mut mode = Unknown;
930 self.determine_pat_move_mode(cmt_discr.clone(), pat, &mut mode);
931 let mode = mode.match_mode();
932 self.walk_pat(cmt_discr, pat, mode);
935 /// Identifies any bindings within `pat` and accumulates within
936 /// `mode` whether the overall pattern/match structure is a move,
938 fn determine_pat_move_mode(&mut self,
939 cmt_discr: mc::cmt<'tcx>,
941 mode: &mut TrackMatchMode) {
942 debug!("determine_pat_move_mode cmt_discr={:?} pat={:?}", cmt_discr,
944 return_if_err!(self.mc.cat_pattern(cmt_discr, pat, |_mc, cmt_pat, pat| {
945 let tcx = self.tcx();
946 let def_map = &self.tcx().def_map;
947 if pat_util::pat_is_binding(&def_map.borrow(), pat) {
949 hir::PatIdent(hir::BindByRef(_), _, _) =>
950 mode.lub(BorrowingMatch),
951 hir::PatIdent(hir::BindByValue(_), _, _) => {
952 match copy_or_move(self.typer, &cmt_pat, PatBindingMove) {
953 Copy => mode.lub(CopyingMatch),
954 Move(_) => mode.lub(MovingMatch),
960 "binding pattern not an identifier");
967 /// The core driver for walking a pattern; `match_mode` must be
968 /// established up front, e.g. via `determine_pat_move_mode` (see
969 /// also `walk_irrefutable_pat` for patterns that stand alone).
970 fn walk_pat(&mut self,
971 cmt_discr: mc::cmt<'tcx>,
973 match_mode: MatchMode) {
974 debug!("walk_pat cmt_discr={:?} pat={:?}", cmt_discr,
978 let typer = self.typer;
979 let def_map = &self.tcx().def_map;
980 let delegate = &mut self.delegate;
981 return_if_err!(mc.cat_pattern(cmt_discr.clone(), pat, |mc, cmt_pat, pat| {
982 if pat_util::pat_is_binding(&def_map.borrow(), pat) {
985 debug!("binding cmt_pat={:?} pat={:?} match_mode={:?}",
990 // pat_ty: the type of the binding being produced.
991 let pat_ty = return_if_err!(typer.node_ty(pat.id));
993 // Each match binding is effectively an assignment to the
994 // binding being produced.
995 let def = def_map.borrow().get(&pat.id).unwrap().full_def();
996 match mc.cat_def(pat.id, pat.span, pat_ty, def) {
998 delegate.mutate(pat.id, pat.span, binding_cmt, MutateMode::Init);
1003 // It is also a borrow or copy/move of the value being matched.
1005 hir::PatIdent(hir::BindByRef(m), _, _) => {
1006 if let ty::TyRef(&r, _) = pat_ty.sty {
1007 let bk = ty::BorrowKind::from_mutbl(m);
1008 delegate.borrow(pat.id, pat.span, cmt_pat,
1012 hir::PatIdent(hir::BindByValue(_), _, _) => {
1013 let mode = copy_or_move(typer, &cmt_pat, PatBindingMove);
1014 debug!("walk_pat binding consuming pat");
1015 delegate.consume_pat(pat, cmt_pat, mode);
1020 "binding pattern not an identifier");
1025 hir::PatVec(_, Some(ref slice_pat), _) => {
1026 // The `slice_pat` here creates a slice into
1027 // the original vector. This is effectively a
1028 // borrow of the elements of the vector being
1031 let (slice_cmt, slice_mutbl, slice_r) =
1032 return_if_err!(mc.cat_slice_pattern(cmt_pat, &**slice_pat));
1034 // Note: We declare here that the borrow
1035 // occurs upon entering the `[...]`
1036 // pattern. This implies that something like
1037 // `[a; b]` where `a` is a move is illegal,
1038 // because the borrow is already in effect.
1039 // In fact such a move would be safe-ish, but
1040 // it effectively *requires* that we use the
1041 // nulling out semantics to indicate when a
1042 // value has been moved, which we are trying
1043 // to move away from. Otherwise, how can we
1044 // indicate that the first element in the
1045 // vector has been moved? Eventually, we
1046 // could perhaps modify this rule to permit
1047 // `[..a, b]` where `b` is a move, because in
1048 // that case we can adjust the length of the
1049 // original vec accordingly, but we'd have to
1050 // make trans do the right thing, and it would
1051 // only work for `Box<[T]>`s. It seems simpler
1052 // to just require that people call
1053 // `vec.pop()` or `vec.unshift()`.
1054 let slice_bk = ty::BorrowKind::from_mutbl(slice_mutbl);
1055 delegate.borrow(pat.id, pat.span,
1057 slice_bk, RefBinding);
1064 // Do a second pass over the pattern, calling `matched_pat` on
1065 // the interior nodes (enum variants and structs), as opposed
1066 // to the above loop's visit of than the bindings that form
1067 // the leaves of the pattern tree structure.
1068 return_if_err!(mc.cat_pattern(cmt_discr, pat, |mc, cmt_pat, pat| {
1069 let def_map = def_map.borrow();
1070 let tcx = typer.tcx;
1073 hir::PatEnum(_, _) | hir::PatQPath(..) |
1074 hir::PatIdent(_, _, None) | hir::PatStruct(..) => {
1075 match def_map.get(&pat.id).map(|d| d.full_def()) {
1077 // no definition found: pat is not a
1078 // struct or enum pattern.
1081 Some(Def::Variant(enum_did, variant_did)) => {
1083 if tcx.lookup_adt_def(enum_did).is_univariant() {
1086 let cmt_pat_ty = cmt_pat.ty;
1087 mc.cat_downcast(pat, cmt_pat, cmt_pat_ty, variant_did)
1090 debug!("variant downcast_cmt={:?} pat={:?}",
1094 delegate.matched_pat(pat, downcast_cmt, match_mode);
1097 Some(Def::Struct(..)) | Some(Def::TyAlias(..)) => {
1098 // A struct (in either the value or type
1099 // namespace; we encounter the former on
1100 // e.g. patterns for unit structs).
1102 debug!("struct cmt_pat={:?} pat={:?}",
1106 delegate.matched_pat(pat, cmt_pat, match_mode);
1109 Some(Def::Const(..)) |
1110 Some(Def::AssociatedConst(..)) |
1111 Some(Def::Local(..)) => {
1112 // This is a leaf (i.e. identifier binding
1113 // or constant value to match); thus no
1114 // `matched_pat` call.
1118 // An enum type should never be in a pattern.
1119 // Remaining cases are e.g. Def::Fn, to
1120 // which identifiers within patterns
1121 // should not resolve. However, we do
1122 // encouter this when using the
1123 // expr-use-visitor during typeck. So just
1124 // ignore it, an error should have been
1127 if !tcx.sess.has_errors() {
1128 let msg = format!("Pattern has unexpected def: {:?} and type {:?}",
1131 tcx.sess.span_bug(pat.span, &msg[..])
1137 hir::PatIdent(_, _, Some(_)) => {
1138 // Do nothing; this is a binding (not an enum
1139 // variant or struct), and the cat_pattern call
1140 // will visit the substructure recursively.
1143 hir::PatWild | hir::PatTup(..) | hir::PatBox(..) |
1144 hir::PatRegion(..) | hir::PatLit(..) | hir::PatRange(..) |
1145 hir::PatVec(..) => {
1146 // Similarly, each of these cases does not
1147 // correspond to an enum variant or struct, so we
1148 // do not do any `matched_pat` calls for these
1155 fn walk_captures(&mut self, closure_expr: &hir::Expr) {
1156 debug!("walk_captures({:?})", closure_expr);
1158 self.tcx().with_freevars(closure_expr.id, |freevars| {
1159 for freevar in freevars {
1160 let id_var = freevar.def.var_id();
1161 let upvar_id = ty::UpvarId { var_id: id_var,
1162 closure_expr_id: closure_expr.id };
1163 let upvar_capture = self.typer.upvar_capture(upvar_id).unwrap();
1164 let cmt_var = return_if_err!(self.cat_captured_var(closure_expr.id,
1167 match upvar_capture {
1168 ty::UpvarCapture::ByValue => {
1169 let mode = copy_or_move(self.typer, &cmt_var, CaptureMove);
1170 self.delegate.consume(closure_expr.id, freevar.span, cmt_var, mode);
1172 ty::UpvarCapture::ByRef(upvar_borrow) => {
1173 self.delegate.borrow(closure_expr.id,
1176 upvar_borrow.region,
1178 ClosureCapture(freevar.span));
1185 fn cat_captured_var(&mut self,
1186 closure_id: ast::NodeId,
1189 -> mc::McResult<mc::cmt<'tcx>> {
1190 // Create the cmt for the variable being borrowed, from the
1191 // caller's perspective
1192 let var_id = upvar_def.var_id();
1193 let var_ty = try!(self.typer.node_ty(var_id));
1194 self.mc.cat_def(closure_id, closure_span, var_ty, upvar_def)
1198 fn copy_or_move<'a, 'tcx>(typer: &infer::InferCtxt<'a, 'tcx>,
1199 cmt: &mc::cmt<'tcx>,
1200 move_reason: MoveReason)
1203 if typer.type_moves_by_default(cmt.ty, cmt.span) {