1 //! A different sort of visitor for walking fn bodies. Unlike the
2 //! normal visitor, which just walks the entire body in one shot, the
3 //! `ExprUseVisitor` determines how expressions are being used.
6 // Export these here so that Clippy can use them.
7 pub use rustc_middle::hir::place::{Place, PlaceBase, PlaceWithHirId, Projection};
9 use rustc_data_structures::fx::FxIndexMap;
11 use rustc_hir::def::Res;
12 use rustc_hir::def_id::LocalDefId;
13 use rustc_hir::PatKind;
14 use rustc_index::vec::Idx;
15 use rustc_infer::infer::InferCtxt;
16 use rustc_middle::hir::place::ProjectionKind;
17 use rustc_middle::mir::FakeReadCause;
18 use rustc_middle::ty::{self, adjustment, AdtKind, Ty, TyCtxt};
19 use rustc_target::abi::VariantIdx;
21 use crate::mem_categorization as mc;
23 /// This trait defines the callbacks you can expect to receive when
24 /// employing the ExprUseVisitor.
25 pub trait Delegate<'tcx> {
26 /// The value found at `place` is moved, depending
27 /// on `mode`. Where `diag_expr_id` is the id used for diagnostics for `place`.
29 /// Use of a `Copy` type in a ByValue context is considered a use
30 /// by `ImmBorrow` and `borrow` is called instead. This is because
31 /// a shared borrow is the "minimum access" that would be needed
32 /// to perform a copy.
35 /// The parameter `diag_expr_id` indicates the HIR id that ought to be used for
36 /// diagnostics. Around pattern matching such as `let pat = expr`, the diagnostic
37 /// id will be the id of the expression `expr` but the place itself will have
38 /// the id of the binding in the pattern `pat`.
39 fn consume(&mut self, place_with_id: &PlaceWithHirId<'tcx>, diag_expr_id: hir::HirId);
41 /// The value found at `place` is being borrowed with kind `bk`.
42 /// `diag_expr_id` is the id used for diagnostics (see `consume` for more details).
45 place_with_id: &PlaceWithHirId<'tcx>,
46 diag_expr_id: hir::HirId,
50 /// The value found at `place` is being copied.
51 /// `diag_expr_id` is the id used for diagnostics (see `consume` for more details).
52 fn copy(&mut self, place_with_id: &PlaceWithHirId<'tcx>, diag_expr_id: hir::HirId) {
53 // In most cases, copying data from `x` is equivalent to doing `*&x`, so by default
54 // we treat a copy of `x` as a borrow of `x`.
55 self.borrow(place_with_id, diag_expr_id, ty::BorrowKind::ImmBorrow)
58 /// The path at `assignee_place` is being assigned to.
59 /// `diag_expr_id` is the id used for diagnostics (see `consume` for more details).
60 fn mutate(&mut self, assignee_place: &PlaceWithHirId<'tcx>, diag_expr_id: hir::HirId);
62 /// The path at `binding_place` is a binding that is being initialized.
64 /// This covers cases such as `let x = 42;`
65 fn bind(&mut self, binding_place: &PlaceWithHirId<'tcx>, diag_expr_id: hir::HirId) {
66 // Bindings can normally be treated as a regular assignment, so by default we
67 // forward this to the mutate callback.
68 self.mutate(binding_place, diag_expr_id)
71 /// The `place` should be a fake read because of specified `cause`.
72 fn fake_read(&mut self, place: Place<'tcx>, cause: FakeReadCause, diag_expr_id: hir::HirId);
75 #[derive(Copy, Clone, PartialEq, Debug)]
77 /// reference to x where x has a type that copies
79 /// reference to x where x has a type that moves
83 #[derive(Copy, Clone, PartialEq, Debug)]
92 /// The ExprUseVisitor type
94 /// This is the code that actually walks the tree.
95 pub struct ExprUseVisitor<'a, 'tcx> {
96 mc: mc::MemCategorizationContext<'a, 'tcx>,
97 body_owner: LocalDefId,
98 delegate: &'a mut dyn Delegate<'tcx>,
101 /// If the MC results in an error, it's because the type check
102 /// failed (or will fail, when the error is uncovered and reported
103 /// during writeback). In this case, we just ignore this part of the
106 /// Note that this macro appears similar to try!(), but, unlike try!(),
107 /// it does not propagate the error.
108 macro_rules! return_if_err {
113 debug!("mc reported err");
120 impl<'a, 'tcx> ExprUseVisitor<'a, 'tcx> {
121 /// Creates the ExprUseVisitor, configuring it with the various options provided:
123 /// - `delegate` -- who receives the callbacks
124 /// - `param_env` --- parameter environment for trait lookups (esp. pertaining to `Copy`)
125 /// - `typeck_results` --- typeck results for the code being analyzed
127 delegate: &'a mut (dyn Delegate<'tcx> + 'a),
128 infcx: &'a InferCtxt<'a, 'tcx>,
129 body_owner: LocalDefId,
130 param_env: ty::ParamEnv<'tcx>,
131 typeck_results: &'a ty::TypeckResults<'tcx>,
134 mc: mc::MemCategorizationContext::new(infcx, param_env, body_owner, typeck_results),
140 #[instrument(skip(self), level = "debug")]
141 pub fn consume_body(&mut self, body: &hir::Body<'_>) {
142 for param in body.params {
143 let param_ty = return_if_err!(self.mc.pat_ty_adjusted(param.pat));
144 debug!("consume_body: param_ty = {:?}", param_ty);
146 let param_place = self.mc.cat_rvalue(param.hir_id, param.pat.span, param_ty);
148 self.walk_irrefutable_pat(¶m_place, param.pat);
151 self.consume_expr(&body.value);
154 fn tcx(&self) -> TyCtxt<'tcx> {
158 fn delegate_consume(&mut self, place_with_id: &PlaceWithHirId<'tcx>, diag_expr_id: hir::HirId) {
159 delegate_consume(&self.mc, self.delegate, place_with_id, diag_expr_id)
162 fn consume_exprs(&mut self, exprs: &[hir::Expr<'_>]) {
164 self.consume_expr(expr);
168 pub fn consume_expr(&mut self, expr: &hir::Expr<'_>) {
169 debug!("consume_expr(expr={:?})", expr);
171 let place_with_id = return_if_err!(self.mc.cat_expr(expr));
172 self.delegate_consume(&place_with_id, place_with_id.hir_id);
173 self.walk_expr(expr);
176 fn mutate_expr(&mut self, expr: &hir::Expr<'_>) {
177 let place_with_id = return_if_err!(self.mc.cat_expr(expr));
178 self.delegate.mutate(&place_with_id, place_with_id.hir_id);
179 self.walk_expr(expr);
182 fn borrow_expr(&mut self, expr: &hir::Expr<'_>, bk: ty::BorrowKind) {
183 debug!("borrow_expr(expr={:?}, bk={:?})", expr, bk);
185 let place_with_id = return_if_err!(self.mc.cat_expr(expr));
186 self.delegate.borrow(&place_with_id, place_with_id.hir_id, bk);
191 fn select_from_expr(&mut self, expr: &hir::Expr<'_>) {
195 pub fn walk_expr(&mut self, expr: &hir::Expr<'_>) {
196 debug!("walk_expr(expr={:?})", expr);
198 self.walk_adjustment(expr);
201 hir::ExprKind::Path(_) => {}
203 hir::ExprKind::Type(subexpr, _) => self.walk_expr(subexpr),
205 hir::ExprKind::Unary(hir::UnOp::Deref, base) => {
207 self.select_from_expr(base);
210 hir::ExprKind::Field(base, _) => {
212 self.select_from_expr(base);
215 hir::ExprKind::Index(lhs, rhs) => {
217 self.select_from_expr(lhs);
218 self.consume_expr(rhs);
221 hir::ExprKind::Call(callee, args) => {
223 self.consume_expr(callee);
224 self.consume_exprs(args);
227 hir::ExprKind::MethodCall(.., args, _) => {
229 self.consume_exprs(args);
232 hir::ExprKind::Struct(_, fields, ref opt_with) => {
233 self.walk_struct_expr(fields, opt_with);
236 hir::ExprKind::Tup(exprs) => {
237 self.consume_exprs(exprs);
240 hir::ExprKind::If(ref cond_expr, ref then_expr, ref opt_else_expr) => {
241 self.consume_expr(cond_expr);
242 self.consume_expr(then_expr);
243 if let Some(ref else_expr) = *opt_else_expr {
244 self.consume_expr(else_expr);
248 hir::ExprKind::Let(hir::Let { pat, init, .. }) => {
249 self.walk_local(init, pat, |t| t.borrow_expr(init, ty::ImmBorrow));
252 hir::ExprKind::Match(ref discr, arms, _) => {
253 let discr_place = return_if_err!(self.mc.cat_expr(discr));
255 // Matching should not always be considered a use of the place, hence
256 // discr does not necessarily need to be borrowed.
257 // We only want to borrow discr if the pattern contain something other
259 let ExprUseVisitor { ref mc, body_owner: _, delegate: _ } = *self;
260 let mut needs_to_be_read = false;
261 for arm in arms.iter() {
262 return_if_err!(mc.cat_pattern(discr_place.clone(), arm.pat, |place, pat| {
264 PatKind::Binding(.., opt_sub_pat) => {
265 // If the opt_sub_pat is None, than the binding does not count as
266 // a wildcard for the purpose of borrowing discr.
267 if opt_sub_pat.is_none() {
268 needs_to_be_read = true;
271 PatKind::Path(qpath) => {
272 // A `Path` pattern is just a name like `Foo`. This is either a
273 // named constant or else it refers to an ADT variant
275 let res = self.mc.typeck_results.qpath_res(qpath, pat.hir_id);
277 Res::Def(DefKind::Const, _)
278 | Res::Def(DefKind::AssocConst, _) => {
279 // Named constants have to be equated with the value
280 // being matched, so that's a read of the value being matched.
282 // FIXME: We don't actually reads for ZSTs.
283 needs_to_be_read = true;
286 // Otherwise, this is a struct/enum variant, and so it's
287 // only a read if we need to read the discriminant.
288 needs_to_be_read |= is_multivariant_adt(place.place.ty());
292 PatKind::TupleStruct(..) | PatKind::Struct(..) | PatKind::Tuple(..) => {
293 // For `Foo(..)`, `Foo { ... }` and `(...)` patterns, check if we are matching
294 // against a multivariant enum or struct. In that case, we have to read
295 // the discriminant. Otherwise this kind of pattern doesn't actually
296 // read anything (we'll get invoked for the `...`, which may indeed
297 // perform some reads).
299 let place_ty = place.place.ty();
300 needs_to_be_read |= is_multivariant_adt(place_ty);
302 PatKind::Lit(_) | PatKind::Range(..) => {
303 // If the PatKind is a Lit or a Range then we want
305 needs_to_be_read = true;
312 // If the PatKind is Or, Box, Slice or Ref, the decision is made later
313 // as these patterns contains subpatterns
314 // If the PatKind is Wild, the decision is made based on the other patterns being
321 if needs_to_be_read {
322 self.borrow_expr(discr, ty::ImmBorrow);
324 let closure_def_id = match discr_place.place.base {
325 PlaceBase::Upvar(upvar_id) => Some(upvar_id.closure_expr_id.to_def_id()),
329 self.delegate.fake_read(
330 discr_place.place.clone(),
331 FakeReadCause::ForMatchedPlace(closure_def_id),
335 // We always want to walk the discriminant. We want to make sure, for instance,
336 // that the discriminant has been initialized.
337 self.walk_expr(discr);
340 // treatment of the discriminant is handled while walking the arms.
342 self.walk_arm(&discr_place, arm);
346 hir::ExprKind::Array(exprs) => {
347 self.consume_exprs(exprs);
350 hir::ExprKind::AddrOf(_, m, ref base) => {
352 // make sure that the thing we are pointing out stays valid
353 // for the lifetime `scope_r` of the resulting ptr:
354 let bk = ty::BorrowKind::from_mutbl(m);
355 self.borrow_expr(base, bk);
358 hir::ExprKind::InlineAsm(asm) => {
359 for (op, _op_sp) in asm.operands {
361 hir::InlineAsmOperand::In { expr, .. }
362 | hir::InlineAsmOperand::Sym { expr, .. } => self.consume_expr(expr),
363 hir::InlineAsmOperand::Out { expr: Some(expr), .. }
364 | hir::InlineAsmOperand::InOut { expr, .. } => {
365 self.mutate_expr(expr);
367 hir::InlineAsmOperand::SplitInOut { in_expr, out_expr, .. } => {
368 self.consume_expr(in_expr);
369 if let Some(out_expr) = out_expr {
370 self.mutate_expr(out_expr);
373 hir::InlineAsmOperand::Out { expr: None, .. }
374 | hir::InlineAsmOperand::Const { .. } => {}
379 hir::ExprKind::Continue(..)
380 | hir::ExprKind::Lit(..)
381 | hir::ExprKind::ConstBlock(..)
382 | hir::ExprKind::Err => {}
384 hir::ExprKind::Loop(blk, ..) => {
385 self.walk_block(blk);
388 hir::ExprKind::Unary(_, lhs) => {
389 self.consume_expr(lhs);
392 hir::ExprKind::Binary(_, lhs, rhs) => {
393 self.consume_expr(lhs);
394 self.consume_expr(rhs);
397 hir::ExprKind::Block(blk, _) => {
398 self.walk_block(blk);
401 hir::ExprKind::Break(_, ref opt_expr) | hir::ExprKind::Ret(ref opt_expr) => {
402 if let Some(expr) = *opt_expr {
403 self.consume_expr(expr);
407 hir::ExprKind::Assign(lhs, rhs, _) => {
408 self.mutate_expr(lhs);
409 self.consume_expr(rhs);
412 hir::ExprKind::Cast(base, _) => {
413 self.consume_expr(base);
416 hir::ExprKind::DropTemps(expr) => {
417 self.consume_expr(expr);
420 hir::ExprKind::AssignOp(_, lhs, rhs) => {
421 if self.mc.typeck_results.is_method_call(expr) {
422 self.consume_expr(lhs);
424 self.mutate_expr(lhs);
426 self.consume_expr(rhs);
429 hir::ExprKind::Repeat(base, _) => {
430 self.consume_expr(base);
433 hir::ExprKind::Closure(..) => {
434 self.walk_captures(expr);
437 hir::ExprKind::Box(ref base) => {
438 self.consume_expr(base);
441 hir::ExprKind::Yield(value, _) => {
442 self.consume_expr(value);
447 fn walk_stmt(&mut self, stmt: &hir::Stmt<'_>) {
449 hir::StmtKind::Local(hir::Local { pat, init: Some(expr), .. }) => {
450 self.walk_local(expr, pat, |_| {});
453 hir::StmtKind::Local(_) => {}
455 hir::StmtKind::Item(_) => {
456 // We don't visit nested items in this visitor,
457 // only the fn body we were given.
460 hir::StmtKind::Expr(ref expr) | hir::StmtKind::Semi(ref expr) => {
461 self.consume_expr(expr);
466 fn walk_local<F>(&mut self, expr: &hir::Expr<'_>, pat: &hir::Pat<'_>, mut f: F)
470 self.walk_expr(expr);
471 let expr_place = return_if_err!(self.mc.cat_expr(expr));
473 self.walk_irrefutable_pat(&expr_place, &pat);
476 /// Indicates that the value of `blk` will be consumed, meaning either copied or moved
477 /// depending on its type.
478 fn walk_block(&mut self, blk: &hir::Block<'_>) {
479 debug!("walk_block(blk.hir_id={})", blk.hir_id);
481 for stmt in blk.stmts {
482 self.walk_stmt(stmt);
485 if let Some(ref tail_expr) = blk.expr {
486 self.consume_expr(tail_expr);
490 fn walk_struct_expr<'hir>(
492 fields: &[hir::ExprField<'_>],
493 opt_with: &Option<&'hir hir::Expr<'_>>,
495 // Consume the expressions supplying values for each field.
496 for field in fields {
497 self.consume_expr(field.expr);
500 let with_expr = match *opt_with {
507 let with_place = return_if_err!(self.mc.cat_expr(with_expr));
509 // Select just those fields of the `with`
510 // expression that will actually be used
511 match with_place.place.ty().kind() {
512 ty::Adt(adt, substs) if adt.is_struct() => {
513 // Consume those fields of the with expression that are needed.
514 for (f_index, with_field) in adt.non_enum_variant().fields.iter().enumerate() {
515 let is_mentioned = fields.iter().any(|f| {
516 self.tcx().field_index(f.hir_id, self.mc.typeck_results) == f_index
519 let field_place = self.mc.cat_projection(
522 with_field.ty(self.tcx(), substs),
523 ProjectionKind::Field(f_index as u32, VariantIdx::new(0)),
525 self.delegate_consume(&field_place, field_place.hir_id);
530 // the base expression should always evaluate to a
531 // struct; however, when EUV is run during typeck, it
532 // may not. This will generate an error earlier in typeck,
533 // so we can just ignore it.
534 if !self.tcx().sess.has_errors().is_some() {
535 span_bug!(with_expr.span, "with expression doesn't evaluate to a struct");
540 // walk the with expression so that complex expressions
541 // are properly handled.
542 self.walk_expr(with_expr);
545 /// Invoke the appropriate delegate calls for anything that gets
546 /// consumed or borrowed as part of the automatic adjustment
548 fn walk_adjustment(&mut self, expr: &hir::Expr<'_>) {
549 let adjustments = self.mc.typeck_results.expr_adjustments(expr);
550 let mut place_with_id = return_if_err!(self.mc.cat_expr_unadjusted(expr));
551 for adjustment in adjustments {
552 debug!("walk_adjustment expr={:?} adj={:?}", expr, adjustment);
553 match adjustment.kind {
554 adjustment::Adjust::NeverToAny | adjustment::Adjust::Pointer(_) => {
555 // Creating a closure/fn-pointer or unsizing consumes
556 // the input and stores it into the resulting rvalue.
557 self.delegate_consume(&place_with_id, place_with_id.hir_id);
560 adjustment::Adjust::Deref(None) => {}
562 // Autoderefs for overloaded Deref calls in fact reference
563 // their receiver. That is, if we have `(*x)` where `x`
564 // is of type `Rc<T>`, then this in fact is equivalent to
565 // `x.deref()`. Since `deref()` is declared with `&self`,
566 // this is an autoref of `x`.
567 adjustment::Adjust::Deref(Some(ref deref)) => {
568 let bk = ty::BorrowKind::from_mutbl(deref.mutbl);
569 self.delegate.borrow(&place_with_id, place_with_id.hir_id, bk);
572 adjustment::Adjust::Borrow(ref autoref) => {
573 self.walk_autoref(expr, &place_with_id, autoref);
577 return_if_err!(self.mc.cat_expr_adjusted(expr, place_with_id, adjustment));
581 /// Walks the autoref `autoref` applied to the autoderef'd
582 /// `expr`. `base_place` is the mem-categorized form of `expr`
583 /// after all relevant autoderefs have occurred.
586 expr: &hir::Expr<'_>,
587 base_place: &PlaceWithHirId<'tcx>,
588 autoref: &adjustment::AutoBorrow<'tcx>,
591 "walk_autoref(expr.hir_id={} base_place={:?} autoref={:?})",
592 expr.hir_id, base_place, autoref
596 adjustment::AutoBorrow::Ref(_, m) => {
597 self.delegate.borrow(
600 ty::BorrowKind::from_mutbl(m.into()),
604 adjustment::AutoBorrow::RawPtr(m) => {
605 debug!("walk_autoref: expr.hir_id={} base_place={:?}", expr.hir_id, base_place);
607 self.delegate.borrow(base_place, base_place.hir_id, ty::BorrowKind::from_mutbl(m));
612 fn walk_arm(&mut self, discr_place: &PlaceWithHirId<'tcx>, arm: &hir::Arm<'_>) {
613 let closure_def_id = match discr_place.place.base {
614 PlaceBase::Upvar(upvar_id) => Some(upvar_id.closure_expr_id.to_def_id()),
618 self.delegate.fake_read(
619 discr_place.place.clone(),
620 FakeReadCause::ForMatchedPlace(closure_def_id),
623 self.walk_pat(discr_place, arm.pat);
625 if let Some(hir::Guard::If(e)) = arm.guard {
627 } else if let Some(hir::Guard::IfLet(_, ref e)) = arm.guard {
631 self.consume_expr(arm.body);
634 /// Walks a pat that occurs in isolation (i.e., top-level of fn argument or
635 /// let binding, and *not* a match arm or nested pat.)
636 fn walk_irrefutable_pat(&mut self, discr_place: &PlaceWithHirId<'tcx>, pat: &hir::Pat<'_>) {
637 let closure_def_id = match discr_place.place.base {
638 PlaceBase::Upvar(upvar_id) => Some(upvar_id.closure_expr_id.to_def_id()),
642 self.delegate.fake_read(
643 discr_place.place.clone(),
644 FakeReadCause::ForLet(closure_def_id),
647 self.walk_pat(discr_place, pat);
650 /// The core driver for walking a pattern
651 fn walk_pat(&mut self, discr_place: &PlaceWithHirId<'tcx>, pat: &hir::Pat<'_>) {
652 debug!("walk_pat(discr_place={:?}, pat={:?})", discr_place, pat);
654 let tcx = self.tcx();
655 let ExprUseVisitor { ref mc, body_owner: _, ref mut delegate } = *self;
656 return_if_err!(mc.cat_pattern(discr_place.clone(), pat, |place, pat| {
657 if let PatKind::Binding(_, canonical_id, ..) = pat.kind {
658 debug!("walk_pat: binding place={:?} pat={:?}", place, pat,);
660 mc.typeck_results.extract_binding_mode(tcx.sess, pat.hir_id, pat.span)
662 debug!("walk_pat: pat.hir_id={:?} bm={:?}", pat.hir_id, bm);
664 // pat_ty: the type of the binding being produced.
665 let pat_ty = return_if_err!(mc.node_ty(pat.hir_id));
666 debug!("walk_pat: pat_ty={:?}", pat_ty);
668 let def = Res::Local(canonical_id);
669 if let Ok(ref binding_place) = mc.cat_res(pat.hir_id, pat.span, pat_ty, def) {
670 delegate.bind(binding_place, binding_place.hir_id);
673 // It is also a borrow or copy/move of the value being matched.
674 // In a cases of pattern like `let pat = upvar`, don't use the span
675 // of the pattern, as this just looks confusing, instead use the span
676 // of the discriminant.
678 ty::BindByReference(m) => {
679 let bk = ty::BorrowKind::from_mutbl(m);
680 delegate.borrow(place, discr_place.hir_id, bk);
682 ty::BindByValue(..) => {
683 debug!("walk_pat binding consuming pat");
684 delegate_consume(mc, *delegate, place, discr_place.hir_id);
692 /// Handle the case where the current body contains a closure.
694 /// When the current body being handled is a closure, then we must make sure that
695 /// - The parent closure only captures Places from the nested closure that are not local to it.
697 /// In the following example the closures `c` only captures `p.x` even though `incr`
698 /// is a capture of the nested closure
700 /// ```rust,ignore(cannot-test-this-because-pseudo-code)
704 /// let nested = || p.x += incr;
708 /// - When reporting the Place back to the Delegate, ensure that the UpvarId uses the enclosing
709 /// closure as the DefId.
710 fn walk_captures(&mut self, closure_expr: &hir::Expr<'_>) {
711 fn upvar_is_local_variable<'tcx>(
712 upvars: Option<&'tcx FxIndexMap<hir::HirId, hir::Upvar>>,
713 upvar_id: hir::HirId,
714 body_owner_is_closure: bool,
716 upvars.map(|upvars| !upvars.contains_key(&upvar_id)).unwrap_or(body_owner_is_closure)
719 debug!("walk_captures({:?})", closure_expr);
721 let tcx = self.tcx();
722 let closure_def_id = tcx.hir().local_def_id(closure_expr.hir_id).to_def_id();
723 let upvars = tcx.upvars_mentioned(self.body_owner);
725 // For purposes of this function, generator and closures are equivalent.
726 let body_owner_is_closure =
727 matches!(tcx.hir().body_owner_kind(self.body_owner), hir::BodyOwnerKind::Closure,);
729 // If we have a nested closure, we want to include the fake reads present in the nested closure.
730 if let Some(fake_reads) = self.mc.typeck_results.closure_fake_reads.get(&closure_def_id) {
731 for (fake_read, cause, hir_id) in fake_reads.iter() {
732 match fake_read.base {
733 PlaceBase::Upvar(upvar_id) => {
734 if upvar_is_local_variable(
736 upvar_id.var_path.hir_id,
737 body_owner_is_closure,
739 // The nested closure might be fake reading the current (enclosing) closure's local variables.
740 // The only places we want to fake read before creating the parent closure are the ones that
741 // are not local to it/ defined by it.
743 // ```rust,ignore(cannot-test-this-because-pseudo-code)
745 // let c = || { // fake reads: v1
747 // let e = || { // fake reads: v1, v2
753 // This check is performed when visiting the body of the outermost closure (`c`) and ensures
754 // that we don't add a fake read of v2 in c.
760 "Do not know how to get HirId out of Rvalue and StaticItem {:?}",
765 self.delegate.fake_read(fake_read.clone(), *cause, *hir_id);
769 if let Some(min_captures) = self.mc.typeck_results.closure_min_captures.get(&closure_def_id)
771 for (var_hir_id, min_list) in min_captures.iter() {
772 if upvars.map_or(body_owner_is_closure, |upvars| !upvars.contains_key(var_hir_id)) {
773 // The nested closure might be capturing the current (enclosing) closure's local variables.
774 // We check if the root variable is ever mentioned within the enclosing closure, if not
775 // then for the current body (if it's a closure) these aren't captures, we will ignore them.
778 for captured_place in min_list {
779 let place = &captured_place.place;
780 let capture_info = captured_place.info;
782 let place_base = if body_owner_is_closure {
783 // Mark the place to be captured by the enclosing closure
784 PlaceBase::Upvar(ty::UpvarId::new(*var_hir_id, self.body_owner))
786 // If the body owner isn't a closure then the variable must
787 // be a local variable
788 PlaceBase::Local(*var_hir_id)
790 let place_with_id = PlaceWithHirId::new(
791 capture_info.path_expr_id.unwrap_or(
792 capture_info.capture_kind_expr_id.unwrap_or(closure_expr.hir_id),
796 place.projections.clone(),
799 match capture_info.capture_kind {
800 ty::UpvarCapture::ByValue => {
801 self.delegate_consume(&place_with_id, place_with_id.hir_id);
803 ty::UpvarCapture::ByRef(upvar_borrow) => {
804 self.delegate.borrow(
806 place_with_id.hir_id,
817 fn copy_or_move<'a, 'tcx>(
818 mc: &mc::MemCategorizationContext<'a, 'tcx>,
819 place_with_id: &PlaceWithHirId<'tcx>,
821 if !mc.type_is_copy_modulo_regions(
822 place_with_id.place.ty(),
823 mc.tcx().hir().span(place_with_id.hir_id),
831 // - If a place is used in a `ByValue` context then move it if it's not a `Copy` type.
832 // - If the place that is a `Copy` type consider it an `ImmBorrow`.
833 fn delegate_consume<'a, 'tcx>(
834 mc: &mc::MemCategorizationContext<'a, 'tcx>,
835 delegate: &mut (dyn Delegate<'tcx> + 'a),
836 place_with_id: &PlaceWithHirId<'tcx>,
837 diag_expr_id: hir::HirId,
839 debug!("delegate_consume(place_with_id={:?})", place_with_id);
841 let mode = copy_or_move(mc, place_with_id);
844 ConsumeMode::Move => delegate.consume(place_with_id, diag_expr_id),
845 ConsumeMode::Copy => delegate.copy(place_with_id, diag_expr_id),
849 fn is_multivariant_adt(ty: Ty<'_>) -> bool {
850 if let ty::Adt(def, _) = ty.kind() {
851 // Note that if a non-exhaustive SingleVariant is defined in another crate, we need
852 // to assume that more cases will be added to the variant in the future. This mean
853 // that we should handle non-exhaustive SingleVariant the same way we would handle
855 // If the variant is not local it must be defined in another crate.
856 let is_non_exhaustive = match def.adt_kind() {
857 AdtKind::Struct | AdtKind::Union => {
858 def.non_enum_variant().is_field_list_non_exhaustive()
860 AdtKind::Enum => def.is_variant_list_non_exhaustive(),
862 def.variants().len() > 1 || (!def.did().is_local() && is_non_exhaustive)