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;
22 use crate::mem_categorization as mc;
24 /// This trait defines the callbacks you can expect to receive when
25 /// employing the ExprUseVisitor.
26 pub trait Delegate<'tcx> {
27 /// The value found at `place` is moved, depending
28 /// on `mode`. Where `diag_expr_id` is the id used for diagnostics for `place`.
30 /// Use of a `Copy` type in a ByValue context is considered a use
31 /// by `ImmBorrow` and `borrow` is called instead. This is because
32 /// a shared borrow is the "minimum access" that would be needed
33 /// to perform a copy.
36 /// The parameter `diag_expr_id` indicates the HIR id that ought to be used for
37 /// diagnostics. Around pattern matching such as `let pat = expr`, the diagnostic
38 /// id will be the id of the expression `expr` but the place itself will have
39 /// the id of the binding in the pattern `pat`.
40 fn consume(&mut self, place_with_id: &PlaceWithHirId<'tcx>, diag_expr_id: hir::HirId);
42 /// The value found at `place` is being borrowed with kind `bk`.
43 /// `diag_expr_id` is the id used for diagnostics (see `consume` for more details).
46 place_with_id: &PlaceWithHirId<'tcx>,
47 diag_expr_id: hir::HirId,
51 /// The path at `assignee_place` is being assigned to.
52 /// `diag_expr_id` is the id used for diagnostics (see `consume` for more details).
53 fn mutate(&mut self, assignee_place: &PlaceWithHirId<'tcx>, diag_expr_id: hir::HirId);
55 /// The `place` should be a fake read because of specified `cause`.
56 fn fake_read(&mut self, place: Place<'tcx>, cause: FakeReadCause, diag_expr_id: hir::HirId);
59 #[derive(Copy, Clone, PartialEq, Debug)]
61 /// reference to x where x has a type that copies
63 /// reference to x where x has a type that moves
67 #[derive(Copy, Clone, PartialEq, Debug)]
76 /// The ExprUseVisitor type
78 /// This is the code that actually walks the tree.
79 pub struct ExprUseVisitor<'a, 'tcx> {
80 mc: mc::MemCategorizationContext<'a, 'tcx>,
81 body_owner: LocalDefId,
82 delegate: &'a mut dyn Delegate<'tcx>,
85 /// If the MC results in an error, it's because the type check
86 /// failed (or will fail, when the error is uncovered and reported
87 /// during writeback). In this case, we just ignore this part of the
90 /// Note that this macro appears similar to try!(), but, unlike try!(),
91 /// it does not propagate the error.
92 macro_rules! return_if_err {
97 debug!("mc reported err");
104 impl<'a, 'tcx> ExprUseVisitor<'a, 'tcx> {
105 /// Creates the ExprUseVisitor, configuring it with the various options provided:
107 /// - `delegate` -- who receives the callbacks
108 /// - `param_env` --- parameter environment for trait lookups (esp. pertaining to `Copy`)
109 /// - `typeck_results` --- typeck results for the code being analyzed
111 delegate: &'a mut (dyn Delegate<'tcx> + 'a),
112 infcx: &'a InferCtxt<'a, 'tcx>,
113 body_owner: LocalDefId,
114 param_env: ty::ParamEnv<'tcx>,
115 typeck_results: &'a ty::TypeckResults<'tcx>,
118 mc: mc::MemCategorizationContext::new(infcx, param_env, body_owner, typeck_results),
124 #[instrument(skip(self), level = "debug")]
125 pub fn consume_body(&mut self, body: &hir::Body<'_>) {
126 for param in body.params {
127 let param_ty = return_if_err!(self.mc.pat_ty_adjusted(param.pat));
128 debug!("consume_body: param_ty = {:?}", param_ty);
130 let param_place = self.mc.cat_rvalue(param.hir_id, param.pat.span, param_ty);
132 self.walk_irrefutable_pat(¶m_place, param.pat);
135 self.consume_expr(&body.value);
138 fn tcx(&self) -> TyCtxt<'tcx> {
142 fn delegate_consume(&mut self, place_with_id: &PlaceWithHirId<'tcx>, diag_expr_id: hir::HirId) {
143 delegate_consume(&self.mc, self.delegate, place_with_id, diag_expr_id)
146 fn consume_exprs(&mut self, exprs: &[hir::Expr<'_>]) {
148 self.consume_expr(expr);
152 pub fn consume_expr(&mut self, expr: &hir::Expr<'_>) {
153 debug!("consume_expr(expr={:?})", expr);
155 let place_with_id = return_if_err!(self.mc.cat_expr(expr));
156 self.delegate_consume(&place_with_id, place_with_id.hir_id);
157 self.walk_expr(expr);
160 fn mutate_expr(&mut self, expr: &hir::Expr<'_>) {
161 let place_with_id = return_if_err!(self.mc.cat_expr(expr));
162 self.delegate.mutate(&place_with_id, place_with_id.hir_id);
163 self.walk_expr(expr);
166 fn borrow_expr(&mut self, expr: &hir::Expr<'_>, bk: ty::BorrowKind) {
167 debug!("borrow_expr(expr={:?}, bk={:?})", expr, bk);
169 let place_with_id = return_if_err!(self.mc.cat_expr(expr));
170 self.delegate.borrow(&place_with_id, place_with_id.hir_id, bk);
175 fn select_from_expr(&mut self, expr: &hir::Expr<'_>) {
179 pub fn walk_expr(&mut self, expr: &hir::Expr<'_>) {
180 debug!("walk_expr(expr={:?})", expr);
182 self.walk_adjustment(expr);
185 hir::ExprKind::Path(_) => {}
187 hir::ExprKind::Type(subexpr, _) => self.walk_expr(subexpr),
189 hir::ExprKind::Unary(hir::UnOp::Deref, base) => {
191 self.select_from_expr(base);
194 hir::ExprKind::Field(base, _) => {
196 self.select_from_expr(base);
199 hir::ExprKind::Index(lhs, rhs) => {
201 self.select_from_expr(lhs);
202 self.consume_expr(rhs);
205 hir::ExprKind::Call(callee, args) => {
207 self.consume_expr(callee);
208 self.consume_exprs(args);
211 hir::ExprKind::MethodCall(.., args, _) => {
213 self.consume_exprs(args);
216 hir::ExprKind::Struct(_, fields, ref opt_with) => {
217 self.walk_struct_expr(fields, opt_with);
220 hir::ExprKind::Tup(exprs) => {
221 self.consume_exprs(exprs);
224 hir::ExprKind::If(ref cond_expr, ref then_expr, ref opt_else_expr) => {
225 self.consume_expr(cond_expr);
226 self.consume_expr(then_expr);
227 if let Some(ref else_expr) = *opt_else_expr {
228 self.consume_expr(else_expr);
232 hir::ExprKind::Let(hir::Let { pat, init, .. }) => {
233 self.walk_local(init, pat, |t| t.borrow_expr(init, ty::ImmBorrow));
236 hir::ExprKind::Match(ref discr, arms, _) => {
237 let discr_place = return_if_err!(self.mc.cat_expr(discr));
239 // Matching should not always be considered a use of the place, hence
240 // discr does not necessarily need to be borrowed.
241 // We only want to borrow discr if the pattern contain something other
243 let ExprUseVisitor { ref mc, body_owner: _, delegate: _ } = *self;
244 let mut needs_to_be_read = false;
245 for arm in arms.iter() {
246 return_if_err!(mc.cat_pattern(discr_place.clone(), arm.pat, |place, pat| {
248 PatKind::Binding(.., opt_sub_pat) => {
249 // If the opt_sub_pat is None, than the binding does not count as
250 // a wildcard for the purpose of borrowing discr.
251 if opt_sub_pat.is_none() {
252 needs_to_be_read = true;
255 PatKind::Path(qpath) => {
256 // A `Path` pattern is just a name like `Foo`. This is either a
257 // named constant or else it refers to an ADT variant
259 let res = self.mc.typeck_results.qpath_res(qpath, pat.hir_id);
261 Res::Def(DefKind::Const, _)
262 | Res::Def(DefKind::AssocConst, _) => {
263 // Named constants have to be equated with the value
264 // being matched, so that's a read of the value being matched.
266 // FIXME: We don't actually reads for ZSTs.
267 needs_to_be_read = true;
270 // Otherwise, this is a struct/enum variant, and so it's
271 // only a read if we need to read the discriminant.
272 needs_to_be_read |= is_multivariant_adt(place.place.ty());
276 PatKind::TupleStruct(..) | PatKind::Struct(..) | PatKind::Tuple(..) => {
277 // For `Foo(..)`, `Foo { ... }` and `(...)` patterns, check if we are matching
278 // against a multivariant enum or struct. In that case, we have to read
279 // the discriminant. Otherwise this kind of pattern doesn't actually
280 // read anything (we'll get invoked for the `...`, which may indeed
281 // perform some reads).
283 let place_ty = place.place.ty();
284 needs_to_be_read |= is_multivariant_adt(place_ty);
286 PatKind::Lit(_) | PatKind::Range(..) => {
287 // If the PatKind is a Lit or a Range then we want
289 needs_to_be_read = true;
296 // If the PatKind is Or, Box, Slice or Ref, the decision is made later
297 // as these patterns contains subpatterns
298 // If the PatKind is Wild, the decision is made based on the other patterns being
305 if needs_to_be_read {
306 self.borrow_expr(discr, ty::ImmBorrow);
308 let closure_def_id = match discr_place.place.base {
309 PlaceBase::Upvar(upvar_id) => Some(upvar_id.closure_expr_id.to_def_id()),
313 self.delegate.fake_read(
314 discr_place.place.clone(),
315 FakeReadCause::ForMatchedPlace(closure_def_id),
319 // We always want to walk the discriminant. We want to make sure, for instance,
320 // that the discriminant has been initialized.
321 self.walk_expr(discr);
324 // treatment of the discriminant is handled while walking the arms.
326 self.walk_arm(&discr_place, arm);
330 hir::ExprKind::Array(exprs) => {
331 self.consume_exprs(exprs);
334 hir::ExprKind::AddrOf(_, m, ref base) => {
336 // make sure that the thing we are pointing out stays valid
337 // for the lifetime `scope_r` of the resulting ptr:
338 let bk = ty::BorrowKind::from_mutbl(m);
339 self.borrow_expr(base, bk);
342 hir::ExprKind::InlineAsm(asm) => {
343 for (op, _op_sp) in asm.operands {
345 hir::InlineAsmOperand::In { expr, .. }
346 | hir::InlineAsmOperand::Sym { expr, .. } => self.consume_expr(expr),
347 hir::InlineAsmOperand::Out { expr: Some(expr), .. }
348 | hir::InlineAsmOperand::InOut { expr, .. } => {
349 self.mutate_expr(expr);
351 hir::InlineAsmOperand::SplitInOut { in_expr, out_expr, .. } => {
352 self.consume_expr(in_expr);
353 if let Some(out_expr) = out_expr {
354 self.mutate_expr(out_expr);
357 hir::InlineAsmOperand::Out { expr: None, .. }
358 | hir::InlineAsmOperand::Const { .. } => {}
363 hir::ExprKind::LlvmInlineAsm(ia) => {
364 for (o, output) in iter::zip(&ia.inner.outputs, ia.outputs_exprs) {
366 self.consume_expr(output);
368 self.mutate_expr(output);
371 self.consume_exprs(ia.inputs_exprs);
374 hir::ExprKind::Continue(..)
375 | hir::ExprKind::Lit(..)
376 | hir::ExprKind::ConstBlock(..)
377 | hir::ExprKind::Err => {}
379 hir::ExprKind::Loop(blk, ..) => {
380 self.walk_block(blk);
383 hir::ExprKind::Unary(_, lhs) => {
384 self.consume_expr(lhs);
387 hir::ExprKind::Binary(_, lhs, rhs) => {
388 self.consume_expr(lhs);
389 self.consume_expr(rhs);
392 hir::ExprKind::Block(blk, _) => {
393 self.walk_block(blk);
396 hir::ExprKind::Break(_, ref opt_expr) | hir::ExprKind::Ret(ref opt_expr) => {
397 if let Some(expr) = *opt_expr {
398 self.consume_expr(expr);
402 hir::ExprKind::Assign(lhs, rhs, _) => {
403 self.mutate_expr(lhs);
404 self.consume_expr(rhs);
407 hir::ExprKind::Cast(base, _) => {
408 self.consume_expr(base);
411 hir::ExprKind::DropTemps(expr) => {
412 self.consume_expr(expr);
415 hir::ExprKind::AssignOp(_, lhs, rhs) => {
416 if self.mc.typeck_results.is_method_call(expr) {
417 self.consume_expr(lhs);
419 self.mutate_expr(lhs);
421 self.consume_expr(rhs);
424 hir::ExprKind::Repeat(base, _) => {
425 self.consume_expr(base);
428 hir::ExprKind::Closure(..) => {
429 self.walk_captures(expr);
432 hir::ExprKind::Box(ref base) => {
433 self.consume_expr(base);
436 hir::ExprKind::Yield(value, _) => {
437 self.consume_expr(value);
442 fn walk_stmt(&mut self, stmt: &hir::Stmt<'_>) {
444 hir::StmtKind::Local(hir::Local { pat, init: Some(expr), .. }) => {
445 self.walk_local(expr, pat, |_| {});
448 hir::StmtKind::Local(_) => {}
450 hir::StmtKind::Item(_) => {
451 // We don't visit nested items in this visitor,
452 // only the fn body we were given.
455 hir::StmtKind::Expr(ref expr) | hir::StmtKind::Semi(ref expr) => {
456 self.consume_expr(expr);
461 fn walk_local<F>(&mut self, expr: &hir::Expr<'_>, pat: &hir::Pat<'_>, mut f: F)
465 self.walk_expr(expr);
466 let expr_place = return_if_err!(self.mc.cat_expr(expr));
468 self.walk_irrefutable_pat(&expr_place, &pat);
471 /// Indicates that the value of `blk` will be consumed, meaning either copied or moved
472 /// depending on its type.
473 fn walk_block(&mut self, blk: &hir::Block<'_>) {
474 debug!("walk_block(blk.hir_id={})", blk.hir_id);
476 for stmt in blk.stmts {
477 self.walk_stmt(stmt);
480 if let Some(ref tail_expr) = blk.expr {
481 self.consume_expr(tail_expr);
485 fn walk_struct_expr<'hir>(
487 fields: &[hir::ExprField<'_>],
488 opt_with: &Option<&'hir hir::Expr<'_>>,
490 // Consume the expressions supplying values for each field.
491 for field in fields {
492 self.consume_expr(field.expr);
495 let with_expr = match *opt_with {
502 let with_place = return_if_err!(self.mc.cat_expr(with_expr));
504 // Select just those fields of the `with`
505 // expression that will actually be used
506 match with_place.place.ty().kind() {
507 ty::Adt(adt, substs) if adt.is_struct() => {
508 // Consume those fields of the with expression that are needed.
509 for (f_index, with_field) in adt.non_enum_variant().fields.iter().enumerate() {
510 let is_mentioned = fields.iter().any(|f| {
511 self.tcx().field_index(f.hir_id, self.mc.typeck_results) == f_index
514 let field_place = self.mc.cat_projection(
517 with_field.ty(self.tcx(), substs),
518 ProjectionKind::Field(f_index as u32, VariantIdx::new(0)),
520 self.delegate_consume(&field_place, field_place.hir_id);
525 // the base expression should always evaluate to a
526 // struct; however, when EUV is run during typeck, it
527 // may not. This will generate an error earlier in typeck,
528 // so we can just ignore it.
529 if !self.tcx().sess.has_errors() {
530 span_bug!(with_expr.span, "with expression doesn't evaluate to a struct");
535 // walk the with expression so that complex expressions
536 // are properly handled.
537 self.walk_expr(with_expr);
540 /// Invoke the appropriate delegate calls for anything that gets
541 /// consumed or borrowed as part of the automatic adjustment
543 fn walk_adjustment(&mut self, expr: &hir::Expr<'_>) {
544 let adjustments = self.mc.typeck_results.expr_adjustments(expr);
545 let mut place_with_id = return_if_err!(self.mc.cat_expr_unadjusted(expr));
546 for adjustment in adjustments {
547 debug!("walk_adjustment expr={:?} adj={:?}", expr, adjustment);
548 match adjustment.kind {
549 adjustment::Adjust::NeverToAny | adjustment::Adjust::Pointer(_) => {
550 // Creating a closure/fn-pointer or unsizing consumes
551 // the input and stores it into the resulting rvalue.
552 self.delegate_consume(&place_with_id, place_with_id.hir_id);
555 adjustment::Adjust::Deref(None) => {}
557 // Autoderefs for overloaded Deref calls in fact reference
558 // their receiver. That is, if we have `(*x)` where `x`
559 // is of type `Rc<T>`, then this in fact is equivalent to
560 // `x.deref()`. Since `deref()` is declared with `&self`,
561 // this is an autoref of `x`.
562 adjustment::Adjust::Deref(Some(ref deref)) => {
563 let bk = ty::BorrowKind::from_mutbl(deref.mutbl);
564 self.delegate.borrow(&place_with_id, place_with_id.hir_id, bk);
567 adjustment::Adjust::Borrow(ref autoref) => {
568 self.walk_autoref(expr, &place_with_id, autoref);
572 return_if_err!(self.mc.cat_expr_adjusted(expr, place_with_id, adjustment));
576 /// Walks the autoref `autoref` applied to the autoderef'd
577 /// `expr`. `base_place` is the mem-categorized form of `expr`
578 /// after all relevant autoderefs have occurred.
581 expr: &hir::Expr<'_>,
582 base_place: &PlaceWithHirId<'tcx>,
583 autoref: &adjustment::AutoBorrow<'tcx>,
586 "walk_autoref(expr.hir_id={} base_place={:?} autoref={:?})",
587 expr.hir_id, base_place, autoref
591 adjustment::AutoBorrow::Ref(_, m) => {
592 self.delegate.borrow(
595 ty::BorrowKind::from_mutbl(m.into()),
599 adjustment::AutoBorrow::RawPtr(m) => {
600 debug!("walk_autoref: expr.hir_id={} base_place={:?}", expr.hir_id, base_place);
602 self.delegate.borrow(base_place, base_place.hir_id, ty::BorrowKind::from_mutbl(m));
607 fn walk_arm(&mut self, discr_place: &PlaceWithHirId<'tcx>, arm: &hir::Arm<'_>) {
608 let closure_def_id = match discr_place.place.base {
609 PlaceBase::Upvar(upvar_id) => Some(upvar_id.closure_expr_id.to_def_id()),
613 self.delegate.fake_read(
614 discr_place.place.clone(),
615 FakeReadCause::ForMatchedPlace(closure_def_id),
618 self.walk_pat(discr_place, arm.pat);
620 if let Some(hir::Guard::If(e)) = arm.guard {
622 } else if let Some(hir::Guard::IfLet(_, ref e)) = arm.guard {
626 self.consume_expr(arm.body);
629 /// Walks a pat that occurs in isolation (i.e., top-level of fn argument or
630 /// let binding, and *not* a match arm or nested pat.)
631 fn walk_irrefutable_pat(&mut self, discr_place: &PlaceWithHirId<'tcx>, pat: &hir::Pat<'_>) {
632 let closure_def_id = match discr_place.place.base {
633 PlaceBase::Upvar(upvar_id) => Some(upvar_id.closure_expr_id.to_def_id()),
637 self.delegate.fake_read(
638 discr_place.place.clone(),
639 FakeReadCause::ForLet(closure_def_id),
642 self.walk_pat(discr_place, pat);
645 /// The core driver for walking a pattern
646 fn walk_pat(&mut self, discr_place: &PlaceWithHirId<'tcx>, pat: &hir::Pat<'_>) {
647 debug!("walk_pat(discr_place={:?}, pat={:?})", discr_place, pat);
649 let tcx = self.tcx();
650 let ExprUseVisitor { ref mc, body_owner: _, ref mut delegate } = *self;
651 return_if_err!(mc.cat_pattern(discr_place.clone(), pat, |place, pat| {
652 if let PatKind::Binding(_, canonical_id, ..) = pat.kind {
653 debug!("walk_pat: binding place={:?} pat={:?}", place, pat,);
655 mc.typeck_results.extract_binding_mode(tcx.sess, pat.hir_id, pat.span)
657 debug!("walk_pat: pat.hir_id={:?} bm={:?}", pat.hir_id, bm);
659 // pat_ty: the type of the binding being produced.
660 let pat_ty = return_if_err!(mc.node_ty(pat.hir_id));
661 debug!("walk_pat: pat_ty={:?}", pat_ty);
663 // Each match binding is effectively an assignment to the
664 // binding being produced.
665 let def = Res::Local(canonical_id);
666 if let Ok(ref binding_place) = mc.cat_res(pat.hir_id, pat.span, pat_ty, def) {
667 delegate.mutate(binding_place, binding_place.hir_id);
670 // It is also a borrow or copy/move of the value being matched.
671 // In a cases of pattern like `let pat = upvar`, don't use the span
672 // of the pattern, as this just looks confusing, instead use the span
673 // of the discriminant.
675 ty::BindByReference(m) => {
676 let bk = ty::BorrowKind::from_mutbl(m);
677 delegate.borrow(place, discr_place.hir_id, bk);
679 ty::BindByValue(..) => {
680 debug!("walk_pat binding consuming pat");
681 delegate_consume(mc, *delegate, place, discr_place.hir_id);
689 /// Handle the case where the current body contains a closure.
691 /// When the current body being handled is a closure, then we must make sure that
692 /// - The parent closure only captures Places from the nested closure that are not local to it.
694 /// In the following example the closures `c` only captures `p.x` even though `incr`
695 /// is a capture of the nested closure
697 /// ```rust,ignore(cannot-test-this-because-pseudo-code)
701 /// let nested = || p.x += incr;
705 /// - When reporting the Place back to the Delegate, ensure that the UpvarId uses the enclosing
706 /// closure as the DefId.
707 fn walk_captures(&mut self, closure_expr: &hir::Expr<'_>) {
708 fn upvar_is_local_variable<'tcx>(
709 upvars: Option<&'tcx FxIndexMap<hir::HirId, hir::Upvar>>,
710 upvar_id: &hir::HirId,
711 body_owner_is_closure: bool,
713 upvars.map(|upvars| !upvars.contains_key(upvar_id)).unwrap_or(body_owner_is_closure)
716 debug!("walk_captures({:?})", closure_expr);
718 let tcx = self.tcx();
719 let closure_def_id = tcx.hir().local_def_id(closure_expr.hir_id).to_def_id();
720 let upvars = tcx.upvars_mentioned(self.body_owner);
722 // For purposes of this function, generator and closures are equivalent.
723 let body_owner_is_closure = matches!(
724 tcx.hir().body_owner_kind(tcx.hir().local_def_id_to_hir_id(self.body_owner)),
725 hir::BodyOwnerKind::Closure,
728 // If we have a nested closure, we want to include the fake reads present in the nested closure.
729 if let Some(fake_reads) = self.mc.typeck_results.closure_fake_reads.get(&closure_def_id) {
730 for (fake_read, cause, hir_id) in fake_reads.iter() {
731 match fake_read.base {
732 PlaceBase::Upvar(upvar_id) => {
733 if upvar_is_local_variable(
735 &upvar_id.var_path.hir_id,
736 body_owner_is_closure,
738 // The nested closure might be fake reading the current (enclosing) closure's local variables.
739 // The only places we want to fake read before creating the parent closure are the ones that
740 // are not local to it/ defined by it.
742 // ```rust,ignore(cannot-test-this-because-pseudo-code)
744 // let c = || { // fake reads: v1
746 // let e = || { // fake reads: v1, v2
752 // This check is performed when visiting the body of the outermost closure (`c`) and ensures
753 // that we don't add a fake read of v2 in c.
759 "Do not know how to get HirId out of Rvalue and StaticItem {:?}",
764 self.delegate.fake_read(fake_read.clone(), *cause, *hir_id);
768 if let Some(min_captures) = self.mc.typeck_results.closure_min_captures.get(&closure_def_id)
770 for (var_hir_id, min_list) in min_captures.iter() {
771 if upvars.map_or(body_owner_is_closure, |upvars| !upvars.contains_key(var_hir_id)) {
772 // The nested closure might be capturing the current (enclosing) closure's local variables.
773 // We check if the root variable is ever mentioned within the enclosing closure, if not
774 // then for the current body (if it's a closure) these aren't captures, we will ignore them.
777 for captured_place in min_list {
778 let place = &captured_place.place;
779 let capture_info = captured_place.info;
781 let place_base = if body_owner_is_closure {
782 // Mark the place to be captured by the enclosing closure
783 PlaceBase::Upvar(ty::UpvarId::new(*var_hir_id, self.body_owner))
785 // If the body owner isn't a closure then the variable must
786 // be a local variable
787 PlaceBase::Local(*var_hir_id)
789 let place_with_id = PlaceWithHirId::new(
790 capture_info.path_expr_id.unwrap_or(
791 capture_info.capture_kind_expr_id.unwrap_or(closure_expr.hir_id),
795 place.projections.clone(),
798 match capture_info.capture_kind {
799 ty::UpvarCapture::ByValue => {
800 self.delegate_consume(&place_with_id, place_with_id.hir_id);
802 ty::UpvarCapture::ByRef(upvar_borrow) => {
803 self.delegate.borrow(
805 place_with_id.hir_id,
816 fn copy_or_move<'a, 'tcx>(
817 mc: &mc::MemCategorizationContext<'a, 'tcx>,
818 place_with_id: &PlaceWithHirId<'tcx>,
820 if !mc.type_is_copy_modulo_regions(
821 place_with_id.place.ty(),
822 mc.tcx().hir().span(place_with_id.hir_id),
830 // - If a place is used in a `ByValue` context then move it if it's not a `Copy` type.
831 // - If the place that is a `Copy` type consider it an `ImmBorrow`.
832 fn delegate_consume<'a, 'tcx>(
833 mc: &mc::MemCategorizationContext<'a, 'tcx>,
834 delegate: &mut (dyn Delegate<'tcx> + 'a),
835 place_with_id: &PlaceWithHirId<'tcx>,
836 diag_expr_id: hir::HirId,
838 debug!("delegate_consume(place_with_id={:?})", place_with_id);
840 let mode = copy_or_move(mc, place_with_id);
843 ConsumeMode::Move => delegate.consume(place_with_id, diag_expr_id),
844 ConsumeMode::Copy => {
845 delegate.borrow(place_with_id, diag_expr_id, ty::BorrowKind::ImmBorrow)
850 fn is_multivariant_adt(ty: Ty<'_>) -> bool {
851 if let ty::Adt(def, _) = ty.kind() {
852 // Note that if a non-exhaustive SingleVariant is defined in another crate, we need
853 // to assume that more cases will be added to the variant in the future. This mean
854 // that we should handle non-exhaustive SingleVariant the same way we would handle
856 // If the variant is not local it must be defined in another crate.
857 let is_non_exhaustive = match def.adt_kind() {
858 AdtKind::Struct | AdtKind::Union => {
859 def.non_enum_variant().is_field_list_non_exhaustive()
861 AdtKind::Enum => def.is_variant_list_non_exhaustive(),
863 def.variants.len() > 1 || (!def.did.is_local() && is_non_exhaustive)