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.
5 use std::slice::from_ref;
9 // Export these here so that Clippy can use them.
10 pub use rustc_middle::hir::place::{Place, PlaceBase, PlaceWithHirId, Projection};
12 use rustc_data_structures::fx::FxIndexMap;
14 use rustc_hir::def::Res;
15 use rustc_hir::def_id::LocalDefId;
16 use rustc_hir::PatKind;
17 use rustc_index::vec::Idx;
18 use rustc_infer::infer::InferCtxt;
19 use rustc_middle::hir::place::ProjectionKind;
20 use rustc_middle::mir::FakeReadCause;
21 use rustc_middle::ty::{self, adjustment, AdtKind, Ty, TyCtxt};
22 use rustc_target::abi::VariantIdx;
23 use ty::BorrowKind::ImmBorrow;
25 use crate::mem_categorization as mc;
27 /// This trait defines the callbacks you can expect to receive when
28 /// employing the ExprUseVisitor.
29 pub trait Delegate<'tcx> {
30 /// The value found at `place` is moved, depending
31 /// on `mode`. Where `diag_expr_id` is the id used for diagnostics for `place`.
33 /// Use of a `Copy` type in a ByValue context is considered a use
34 /// by `ImmBorrow` and `borrow` is called instead. This is because
35 /// a shared borrow is the "minimum access" that would be needed
36 /// to perform a copy.
39 /// The parameter `diag_expr_id` indicates the HIR id that ought to be used for
40 /// diagnostics. Around pattern matching such as `let pat = expr`, the diagnostic
41 /// id will be the id of the expression `expr` but the place itself will have
42 /// the id of the binding in the pattern `pat`.
43 fn consume(&mut self, place_with_id: &PlaceWithHirId<'tcx>, diag_expr_id: hir::HirId);
45 /// The value found at `place` is being borrowed with kind `bk`.
46 /// `diag_expr_id` is the id used for diagnostics (see `consume` for more details).
49 place_with_id: &PlaceWithHirId<'tcx>,
50 diag_expr_id: hir::HirId,
54 /// The value found at `place` is being copied.
55 /// `diag_expr_id` is the id used for diagnostics (see `consume` for more details).
56 fn copy(&mut self, place_with_id: &PlaceWithHirId<'tcx>, diag_expr_id: hir::HirId) {
57 // In most cases, copying data from `x` is equivalent to doing `*&x`, so by default
58 // we treat a copy of `x` as a borrow of `x`.
59 self.borrow(place_with_id, diag_expr_id, ty::BorrowKind::ImmBorrow)
62 /// The path at `assignee_place` is being assigned to.
63 /// `diag_expr_id` is the id used for diagnostics (see `consume` for more details).
64 fn mutate(&mut self, assignee_place: &PlaceWithHirId<'tcx>, diag_expr_id: hir::HirId);
66 /// The path at `binding_place` is a binding that is being initialized.
68 /// This covers cases such as `let x = 42;`
69 fn bind(&mut self, binding_place: &PlaceWithHirId<'tcx>, diag_expr_id: hir::HirId) {
70 // Bindings can normally be treated as a regular assignment, so by default we
71 // forward this to the mutate callback.
72 self.mutate(binding_place, diag_expr_id)
75 /// The `place` should be a fake read because of specified `cause`.
78 place_with_id: &PlaceWithHirId<'tcx>,
80 diag_expr_id: hir::HirId,
84 #[derive(Copy, Clone, PartialEq, Debug)]
86 /// reference to x where x has a type that copies
88 /// reference to x where x has a type that moves
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<'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(.., receiver, args, _) => {
229 self.consume_expr(receiver);
230 self.consume_exprs(args);
233 hir::ExprKind::Struct(_, fields, ref opt_with) => {
234 self.walk_struct_expr(fields, opt_with);
237 hir::ExprKind::Tup(exprs) => {
238 self.consume_exprs(exprs);
241 hir::ExprKind::If(ref cond_expr, ref then_expr, ref opt_else_expr) => {
242 self.consume_expr(cond_expr);
243 self.consume_expr(then_expr);
244 if let Some(ref else_expr) = *opt_else_expr {
245 self.consume_expr(else_expr);
249 hir::ExprKind::Let(hir::Let { pat, init, .. }) => {
250 self.walk_local(init, pat, None, |t| t.borrow_expr(init, ty::ImmBorrow))
253 hir::ExprKind::Match(ref discr, arms, _) => {
254 let discr_place = return_if_err!(self.mc.cat_expr(discr));
255 self.maybe_read_scrutinee(
258 arms.iter().map(|arm| arm.pat),
261 // treatment of the discriminant is handled while walking the arms.
263 self.walk_arm(&discr_place, arm);
267 hir::ExprKind::Array(exprs) => {
268 self.consume_exprs(exprs);
271 hir::ExprKind::AddrOf(_, m, ref base) => {
273 // make sure that the thing we are pointing out stays valid
274 // for the lifetime `scope_r` of the resulting ptr:
275 let bk = ty::BorrowKind::from_mutbl(m);
276 self.borrow_expr(base, bk);
279 hir::ExprKind::InlineAsm(asm) => {
280 for (op, _op_sp) in asm.operands {
282 hir::InlineAsmOperand::In { expr, .. } => self.consume_expr(expr),
283 hir::InlineAsmOperand::Out { expr: Some(expr), .. }
284 | hir::InlineAsmOperand::InOut { expr, .. } => {
285 self.mutate_expr(expr);
287 hir::InlineAsmOperand::SplitInOut { in_expr, out_expr, .. } => {
288 self.consume_expr(in_expr);
289 if let Some(out_expr) = out_expr {
290 self.mutate_expr(out_expr);
293 hir::InlineAsmOperand::Out { expr: None, .. }
294 | hir::InlineAsmOperand::Const { .. }
295 | hir::InlineAsmOperand::SymFn { .. }
296 | hir::InlineAsmOperand::SymStatic { .. } => {}
301 hir::ExprKind::Continue(..)
302 | hir::ExprKind::Lit(..)
303 | hir::ExprKind::ConstBlock(..)
304 | hir::ExprKind::Err => {}
306 hir::ExprKind::Loop(blk, ..) => {
307 self.walk_block(blk);
310 hir::ExprKind::Unary(_, lhs) => {
311 self.consume_expr(lhs);
314 hir::ExprKind::Binary(_, lhs, rhs) => {
315 self.consume_expr(lhs);
316 self.consume_expr(rhs);
319 hir::ExprKind::Block(blk, _) => {
320 self.walk_block(blk);
323 hir::ExprKind::Break(_, ref opt_expr) | hir::ExprKind::Ret(ref opt_expr) => {
324 if let Some(expr) = *opt_expr {
325 self.consume_expr(expr);
329 hir::ExprKind::Assign(lhs, rhs, _) => {
330 self.mutate_expr(lhs);
331 self.consume_expr(rhs);
334 hir::ExprKind::Cast(base, _) => {
335 self.consume_expr(base);
338 hir::ExprKind::DropTemps(expr) => {
339 self.consume_expr(expr);
342 hir::ExprKind::AssignOp(_, lhs, rhs) => {
343 if self.mc.typeck_results.is_method_call(expr) {
344 self.consume_expr(lhs);
346 self.mutate_expr(lhs);
348 self.consume_expr(rhs);
351 hir::ExprKind::Repeat(base, _) => {
352 self.consume_expr(base);
355 hir::ExprKind::Closure(closure) => {
356 self.walk_captures(closure);
359 hir::ExprKind::Box(ref base) => {
360 self.consume_expr(base);
363 hir::ExprKind::Yield(value, _) => {
364 self.consume_expr(value);
369 fn walk_stmt(&mut self, stmt: &hir::Stmt<'_>) {
371 hir::StmtKind::Local(hir::Local { pat, init: Some(expr), els, .. }) => {
372 self.walk_local(expr, pat, *els, |_| {})
375 hir::StmtKind::Local(_) => {}
377 hir::StmtKind::Item(_) => {
378 // We don't visit nested items in this visitor,
379 // only the fn body we were given.
382 hir::StmtKind::Expr(ref expr) | hir::StmtKind::Semi(ref expr) => {
383 self.consume_expr(expr);
388 fn maybe_read_scrutinee<'t>(
391 discr_place: PlaceWithHirId<'tcx>,
392 pats: impl Iterator<Item = &'t hir::Pat<'t>>,
394 // Matching should not always be considered a use of the place, hence
395 // discr does not necessarily need to be borrowed.
396 // We only want to borrow discr if the pattern contain something other
398 let ExprUseVisitor { ref mc, body_owner: _, delegate: _ } = *self;
399 let mut needs_to_be_read = false;
401 return_if_err!(mc.cat_pattern(discr_place.clone(), pat, |place, pat| {
403 PatKind::Binding(.., opt_sub_pat) => {
404 // If the opt_sub_pat is None, than the binding does not count as
405 // a wildcard for the purpose of borrowing discr.
406 if opt_sub_pat.is_none() {
407 needs_to_be_read = true;
410 PatKind::Path(qpath) => {
411 // A `Path` pattern is just a name like `Foo`. This is either a
412 // named constant or else it refers to an ADT variant
414 let res = self.mc.typeck_results.qpath_res(qpath, pat.hir_id);
416 Res::Def(DefKind::Const, _) | Res::Def(DefKind::AssocConst, _) => {
417 // Named constants have to be equated with the value
418 // being matched, so that's a read of the value being matched.
420 // FIXME: We don't actually reads for ZSTs.
421 needs_to_be_read = true;
424 // Otherwise, this is a struct/enum variant, and so it's
425 // only a read if we need to read the discriminant.
426 needs_to_be_read |= is_multivariant_adt(place.place.ty());
430 PatKind::TupleStruct(..) | PatKind::Struct(..) | PatKind::Tuple(..) => {
431 // For `Foo(..)`, `Foo { ... }` and `(...)` patterns, check if we are matching
432 // against a multivariant enum or struct. In that case, we have to read
433 // the discriminant. Otherwise this kind of pattern doesn't actually
434 // read anything (we'll get invoked for the `...`, which may indeed
435 // perform some reads).
437 let place_ty = place.place.ty();
438 needs_to_be_read |= is_multivariant_adt(place_ty);
440 PatKind::Lit(_) | PatKind::Range(..) => {
441 // If the PatKind is a Lit or a Range then we want
443 needs_to_be_read = true;
450 // If the PatKind is Or, Box, Slice or Ref, the decision is made later
451 // as these patterns contains subpatterns
452 // If the PatKind is Wild, the decision is made based on the other patterns being
459 if needs_to_be_read {
460 self.borrow_expr(discr, ty::ImmBorrow);
462 let closure_def_id = match discr_place.place.base {
463 PlaceBase::Upvar(upvar_id) => Some(upvar_id.closure_expr_id),
467 self.delegate.fake_read(
469 FakeReadCause::ForMatchedPlace(closure_def_id),
473 // We always want to walk the discriminant. We want to make sure, for instance,
474 // that the discriminant has been initialized.
475 self.walk_expr(discr);
481 expr: &hir::Expr<'_>,
483 els: Option<&hir::Block<'_>>,
488 self.walk_expr(expr);
489 let expr_place = return_if_err!(self.mc.cat_expr(expr));
491 if let Some(els) = els {
492 // borrowing because we need to test the discriminant
493 self.maybe_read_scrutinee(expr, expr_place.clone(), from_ref(pat).iter());
496 self.walk_irrefutable_pat(&expr_place, &pat);
499 /// Indicates that the value of `blk` will be consumed, meaning either copied or moved
500 /// depending on its type.
501 fn walk_block(&mut self, blk: &hir::Block<'_>) {
502 debug!("walk_block(blk.hir_id={})", blk.hir_id);
504 for stmt in blk.stmts {
505 self.walk_stmt(stmt);
508 if let Some(ref tail_expr) = blk.expr {
509 self.consume_expr(tail_expr);
513 fn walk_struct_expr<'hir>(
515 fields: &[hir::ExprField<'_>],
516 opt_with: &Option<&'hir hir::Expr<'_>>,
518 // Consume the expressions supplying values for each field.
519 for field in fields {
520 self.consume_expr(field.expr);
523 let with_expr = match *opt_with {
530 let with_place = return_if_err!(self.mc.cat_expr(with_expr));
532 // Select just those fields of the `with`
533 // expression that will actually be used
534 match with_place.place.ty().kind() {
535 ty::Adt(adt, substs) if adt.is_struct() => {
536 // Consume those fields of the with expression that are needed.
537 for (f_index, with_field) in adt.non_enum_variant().fields.iter().enumerate() {
538 let is_mentioned = fields.iter().any(|f| {
539 self.tcx().field_index(f.hir_id, self.mc.typeck_results) == f_index
542 let field_place = self.mc.cat_projection(
545 with_field.ty(self.tcx(), substs),
546 ProjectionKind::Field(f_index as u32, VariantIdx::new(0)),
548 self.delegate_consume(&field_place, field_place.hir_id);
553 // the base expression should always evaluate to a
554 // struct; however, when EUV is run during typeck, it
555 // may not. This will generate an error earlier in typeck,
556 // so we can just ignore it.
557 if !self.tcx().sess.has_errors().is_some() {
558 span_bug!(with_expr.span, "with expression doesn't evaluate to a struct");
563 // walk the with expression so that complex expressions
564 // are properly handled.
565 self.walk_expr(with_expr);
568 /// Invoke the appropriate delegate calls for anything that gets
569 /// consumed or borrowed as part of the automatic adjustment
571 fn walk_adjustment(&mut self, expr: &hir::Expr<'_>) {
572 let adjustments = self.mc.typeck_results.expr_adjustments(expr);
573 let mut place_with_id = return_if_err!(self.mc.cat_expr_unadjusted(expr));
574 for adjustment in adjustments {
575 debug!("walk_adjustment expr={:?} adj={:?}", expr, adjustment);
576 match adjustment.kind {
577 adjustment::Adjust::NeverToAny
578 | adjustment::Adjust::Pointer(_)
579 | adjustment::Adjust::DynStar => {
580 // Creating a closure/fn-pointer or unsizing consumes
581 // the input and stores it into the resulting rvalue.
582 self.delegate_consume(&place_with_id, place_with_id.hir_id);
585 adjustment::Adjust::Deref(None) => {}
587 // Autoderefs for overloaded Deref calls in fact reference
588 // their receiver. That is, if we have `(*x)` where `x`
589 // is of type `Rc<T>`, then this in fact is equivalent to
590 // `x.deref()`. Since `deref()` is declared with `&self`,
591 // this is an autoref of `x`.
592 adjustment::Adjust::Deref(Some(ref deref)) => {
593 let bk = ty::BorrowKind::from_mutbl(deref.mutbl);
594 self.delegate.borrow(&place_with_id, place_with_id.hir_id, bk);
597 adjustment::Adjust::Borrow(ref autoref) => {
598 self.walk_autoref(expr, &place_with_id, autoref);
602 return_if_err!(self.mc.cat_expr_adjusted(expr, place_with_id, adjustment));
606 /// Walks the autoref `autoref` applied to the autoderef'd
607 /// `expr`. `base_place` is the mem-categorized form of `expr`
608 /// after all relevant autoderefs have occurred.
611 expr: &hir::Expr<'_>,
612 base_place: &PlaceWithHirId<'tcx>,
613 autoref: &adjustment::AutoBorrow<'tcx>,
616 "walk_autoref(expr.hir_id={} base_place={:?} autoref={:?})",
617 expr.hir_id, base_place, autoref
621 adjustment::AutoBorrow::Ref(_, m) => {
622 self.delegate.borrow(
625 ty::BorrowKind::from_mutbl(m.into()),
629 adjustment::AutoBorrow::RawPtr(m) => {
630 debug!("walk_autoref: expr.hir_id={} base_place={:?}", expr.hir_id, base_place);
632 self.delegate.borrow(base_place, base_place.hir_id, ty::BorrowKind::from_mutbl(m));
637 fn walk_arm(&mut self, discr_place: &PlaceWithHirId<'tcx>, arm: &hir::Arm<'_>) {
638 let closure_def_id = match discr_place.place.base {
639 PlaceBase::Upvar(upvar_id) => Some(upvar_id.closure_expr_id),
643 self.delegate.fake_read(
645 FakeReadCause::ForMatchedPlace(closure_def_id),
648 self.walk_pat(discr_place, arm.pat, arm.guard.is_some());
650 if let Some(hir::Guard::If(e)) = arm.guard {
652 } else if let Some(hir::Guard::IfLet(ref l)) = arm.guard {
653 self.consume_expr(l.init)
656 self.consume_expr(arm.body);
659 /// Walks a pat that occurs in isolation (i.e., top-level of fn argument or
660 /// let binding, and *not* a match arm or nested pat.)
661 fn walk_irrefutable_pat(&mut self, discr_place: &PlaceWithHirId<'tcx>, pat: &hir::Pat<'_>) {
662 let closure_def_id = match discr_place.place.base {
663 PlaceBase::Upvar(upvar_id) => Some(upvar_id.closure_expr_id),
667 self.delegate.fake_read(
669 FakeReadCause::ForLet(closure_def_id),
672 self.walk_pat(discr_place, pat, false);
675 /// The core driver for walking a pattern
678 discr_place: &PlaceWithHirId<'tcx>,
682 debug!("walk_pat(discr_place={:?}, pat={:?}, has_guard={:?})", discr_place, pat, has_guard);
684 let tcx = self.tcx();
685 let ExprUseVisitor { ref mc, body_owner: _, ref mut delegate } = *self;
686 return_if_err!(mc.cat_pattern(discr_place.clone(), pat, |place, pat| {
687 if let PatKind::Binding(_, canonical_id, ..) = pat.kind {
688 debug!("walk_pat: binding place={:?} pat={:?}", place, pat);
690 mc.typeck_results.extract_binding_mode(tcx.sess, pat.hir_id, pat.span)
692 debug!("walk_pat: pat.hir_id={:?} bm={:?}", pat.hir_id, bm);
694 // pat_ty: the type of the binding being produced.
695 let pat_ty = return_if_err!(mc.node_ty(pat.hir_id));
696 debug!("walk_pat: pat_ty={:?}", pat_ty);
698 let def = Res::Local(canonical_id);
699 if let Ok(ref binding_place) = mc.cat_res(pat.hir_id, pat.span, pat_ty, def) {
700 delegate.bind(binding_place, binding_place.hir_id);
703 // Subtle: MIR desugaring introduces immutable borrows for each pattern
704 // binding when lowering pattern guards to ensure that the guard does not
705 // modify the scrutinee.
707 delegate.borrow(place, discr_place.hir_id, ImmBorrow);
710 // It is also a borrow or copy/move of the value being matched.
711 // In a cases of pattern like `let pat = upvar`, don't use the span
712 // of the pattern, as this just looks confusing, instead use the span
713 // of the discriminant.
715 ty::BindByReference(m) => {
716 let bk = ty::BorrowKind::from_mutbl(m);
717 delegate.borrow(place, discr_place.hir_id, bk);
719 ty::BindByValue(..) => {
720 debug!("walk_pat binding consuming pat");
721 delegate_consume(mc, *delegate, place, discr_place.hir_id);
729 /// Handle the case where the current body contains a closure.
731 /// When the current body being handled is a closure, then we must make sure that
732 /// - The parent closure only captures Places from the nested closure that are not local to it.
734 /// In the following example the closures `c` only captures `p.x` even though `incr`
735 /// is a capture of the nested closure
738 /// struct P { x: i32 }
739 /// let mut p = P { x: 4 };
742 /// let nested = || p.x += incr;
746 /// - When reporting the Place back to the Delegate, ensure that the UpvarId uses the enclosing
747 /// closure as the DefId.
748 fn walk_captures(&mut self, closure_expr: &hir::Closure<'_>) {
749 fn upvar_is_local_variable<'tcx>(
750 upvars: Option<&'tcx FxIndexMap<hir::HirId, hir::Upvar>>,
751 upvar_id: hir::HirId,
752 body_owner_is_closure: bool,
754 upvars.map(|upvars| !upvars.contains_key(&upvar_id)).unwrap_or(body_owner_is_closure)
757 debug!("walk_captures({:?})", closure_expr);
759 let tcx = self.tcx();
760 let closure_def_id = closure_expr.def_id;
761 let upvars = tcx.upvars_mentioned(self.body_owner);
763 // For purposes of this function, generator and closures are equivalent.
764 let body_owner_is_closure =
765 matches!(tcx.hir().body_owner_kind(self.body_owner), hir::BodyOwnerKind::Closure,);
767 // If we have a nested closure, we want to include the fake reads present in the nested closure.
768 if let Some(fake_reads) = self.mc.typeck_results.closure_fake_reads.get(&closure_def_id) {
769 for (fake_read, cause, hir_id) in fake_reads.iter() {
770 match fake_read.base {
771 PlaceBase::Upvar(upvar_id) => {
772 if upvar_is_local_variable(
774 upvar_id.var_path.hir_id,
775 body_owner_is_closure,
777 // The nested closure might be fake reading the current (enclosing) closure's local variables.
778 // The only places we want to fake read before creating the parent closure are the ones that
779 // are not local to it/ defined by it.
781 // ```rust,ignore(cannot-test-this-because-pseudo-code)
783 // let c = || { // fake reads: v1
785 // let e = || { // fake reads: v1, v2
791 // This check is performed when visiting the body of the outermost closure (`c`) and ensures
792 // that we don't add a fake read of v2 in c.
798 "Do not know how to get HirId out of Rvalue and StaticItem {:?}",
803 self.delegate.fake_read(
804 &PlaceWithHirId { place: fake_read.clone(), hir_id: *hir_id },
811 if let Some(min_captures) = self.mc.typeck_results.closure_min_captures.get(&closure_def_id)
813 for (var_hir_id, min_list) in min_captures.iter() {
814 if upvars.map_or(body_owner_is_closure, |upvars| !upvars.contains_key(var_hir_id)) {
815 // The nested closure might be capturing the current (enclosing) closure's local variables.
816 // We check if the root variable is ever mentioned within the enclosing closure, if not
817 // then for the current body (if it's a closure) these aren't captures, we will ignore them.
820 for captured_place in min_list {
821 let place = &captured_place.place;
822 let capture_info = captured_place.info;
824 let place_base = if body_owner_is_closure {
825 // Mark the place to be captured by the enclosing closure
826 PlaceBase::Upvar(ty::UpvarId::new(*var_hir_id, self.body_owner))
828 // If the body owner isn't a closure then the variable must
829 // be a local variable
830 PlaceBase::Local(*var_hir_id)
832 let closure_hir_id = tcx.hir().local_def_id_to_hir_id(closure_def_id);
833 let place_with_id = PlaceWithHirId::new(
836 .unwrap_or(capture_info.capture_kind_expr_id.unwrap_or(closure_hir_id)),
839 place.projections.clone(),
842 match capture_info.capture_kind {
843 ty::UpvarCapture::ByValue => {
844 self.delegate_consume(&place_with_id, place_with_id.hir_id);
846 ty::UpvarCapture::ByRef(upvar_borrow) => {
847 self.delegate.borrow(
849 place_with_id.hir_id,
860 fn copy_or_move<'a, 'tcx>(
861 mc: &mc::MemCategorizationContext<'a, 'tcx>,
862 place_with_id: &PlaceWithHirId<'tcx>,
864 if !mc.type_is_copy_modulo_regions(
865 place_with_id.place.ty(),
866 mc.tcx().hir().span(place_with_id.hir_id),
874 // - If a place is used in a `ByValue` context then move it if it's not a `Copy` type.
875 // - If the place that is a `Copy` type consider it an `ImmBorrow`.
876 fn delegate_consume<'a, 'tcx>(
877 mc: &mc::MemCategorizationContext<'a, 'tcx>,
878 delegate: &mut (dyn Delegate<'tcx> + 'a),
879 place_with_id: &PlaceWithHirId<'tcx>,
880 diag_expr_id: hir::HirId,
882 debug!("delegate_consume(place_with_id={:?})", place_with_id);
884 let mode = copy_or_move(mc, place_with_id);
887 ConsumeMode::Move => delegate.consume(place_with_id, diag_expr_id),
888 ConsumeMode::Copy => delegate.copy(place_with_id, diag_expr_id),
892 fn is_multivariant_adt(ty: Ty<'_>) -> bool {
893 if let ty::Adt(def, _) = ty.kind() {
894 // Note that if a non-exhaustive SingleVariant is defined in another crate, we need
895 // to assume that more cases will be added to the variant in the future. This mean
896 // that we should handle non-exhaustive SingleVariant the same way we would handle
898 // If the variant is not local it must be defined in another crate.
899 let is_non_exhaustive = match def.adt_kind() {
900 AdtKind::Struct | AdtKind::Union => {
901 def.non_enum_variant().is_field_list_non_exhaustive()
903 AdtKind::Enum => def.is_variant_list_non_exhaustive(),
905 def.variants().len() > 1 || (!def.did().is_local() && is_non_exhaustive)