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 // Export these here so that Clippy can use them.
6 pub use rustc_middle::hir::place::{Place, PlaceBase, PlaceWithHirId, Projection};
8 use rustc_data_structures::fx::FxIndexMap;
10 use rustc_hir::def::Res;
11 use rustc_hir::def_id::LocalDefId;
12 use rustc_hir::PatKind;
13 use rustc_index::vec::Idx;
14 use rustc_infer::infer::InferCtxt;
15 use rustc_middle::hir::place::ProjectionKind;
16 use rustc_middle::mir::FakeReadCause;
17 use rustc_middle::ty::{self, adjustment, TyCtxt};
18 use rustc_target::abi::VariantIdx;
21 use crate::mem_categorization as mc;
23 ///////////////////////////////////////////////////////////////////////////
26 /// This trait defines the callbacks you can expect to receive when
27 /// employing the ExprUseVisitor.
28 pub trait Delegate<'tcx> {
29 // The value found at `place` is moved, depending
30 // on `mode`. Where `diag_expr_id` is the id used for diagnostics for `place`.
32 // Use of a `Copy` type in a ByValue context is considered a use
33 // by `ImmBorrow` and `borrow` is called instead. This is because
34 // a shared borrow is the "minimum access" that would be needed
38 // The parameter `diag_expr_id` indicates the HIR id that ought to be used for
39 // diagnostics. Around pattern matching such as `let pat = expr`, the diagnostic
40 // id will be the id of the expression `expr` but the place itself will have
41 // the id of the binding in the pattern `pat`.
42 fn consume(&mut self, place_with_id: &PlaceWithHirId<'tcx>, diag_expr_id: hir::HirId);
44 // The value found at `place` is being borrowed with kind `bk`.
45 // `diag_expr_id` is the id used for diagnostics (see `consume` for more details).
48 place_with_id: &PlaceWithHirId<'tcx>,
49 diag_expr_id: hir::HirId,
53 // The path at `assignee_place` is being assigned to.
54 // `diag_expr_id` is the id used for diagnostics (see `consume` for more details).
55 fn mutate(&mut self, assignee_place: &PlaceWithHirId<'tcx>, diag_expr_id: hir::HirId);
57 // The `place` should be a fake read because of specified `cause`.
58 fn fake_read(&mut self, place: Place<'tcx>, cause: FakeReadCause, diag_expr_id: hir::HirId);
61 #[derive(Copy, Clone, PartialEq, Debug)]
63 Copy, // reference to x where x has a type that copies
64 Move, // reference to x where x has a type that moves
67 #[derive(Copy, Clone, PartialEq, Debug)]
71 WriteAndRead, // x += y
74 ///////////////////////////////////////////////////////////////////////////
75 // The ExprUseVisitor type
77 // This is the code that actually walks the tree.
78 pub struct ExprUseVisitor<'a, 'tcx> {
79 mc: mc::MemCategorizationContext<'a, 'tcx>,
80 body_owner: LocalDefId,
81 delegate: &'a mut dyn Delegate<'tcx>,
84 // If the MC results in an error, it's because the type check
85 // failed (or will fail, when the error is uncovered and reported
86 // during writeback). In this case, we just ignore this part of the
89 // Note that this macro appears similar to try!(), but, unlike try!(),
90 // it does not propagate the error.
91 macro_rules! return_if_err {
96 debug!("mc reported err");
103 impl<'a, 'tcx> ExprUseVisitor<'a, 'tcx> {
104 /// Creates the ExprUseVisitor, configuring it with the various options provided:
106 /// - `delegate` -- who receives the callbacks
107 /// - `param_env` --- parameter environment for trait lookups (esp. pertaining to `Copy`)
108 /// - `typeck_results` --- typeck results for the code being analyzed
110 delegate: &'a mut (dyn Delegate<'tcx> + 'a),
111 infcx: &'a InferCtxt<'a, 'tcx>,
112 body_owner: LocalDefId,
113 param_env: ty::ParamEnv<'tcx>,
114 typeck_results: &'a ty::TypeckResults<'tcx>,
117 mc: mc::MemCategorizationContext::new(infcx, param_env, body_owner, typeck_results),
123 #[instrument(skip(self), level = "debug")]
124 pub fn consume_body(&mut self, body: &hir::Body<'_>) {
125 for param in body.params {
126 let param_ty = return_if_err!(self.mc.pat_ty_adjusted(¶m.pat));
127 debug!("consume_body: param_ty = {:?}", param_ty);
129 let param_place = self.mc.cat_rvalue(param.hir_id, param.pat.span, param_ty);
131 self.walk_irrefutable_pat(¶m_place, ¶m.pat);
134 self.consume_expr(&body.value);
137 fn tcx(&self) -> TyCtxt<'tcx> {
141 fn delegate_consume(&mut self, place_with_id: &PlaceWithHirId<'tcx>, diag_expr_id: hir::HirId) {
142 delegate_consume(&self.mc, self.delegate, place_with_id, diag_expr_id)
145 fn consume_exprs(&mut self, exprs: &[hir::Expr<'_>]) {
147 self.consume_expr(&expr);
151 pub fn consume_expr(&mut self, expr: &hir::Expr<'_>) {
152 debug!("consume_expr(expr={:?})", expr);
154 let place_with_id = return_if_err!(self.mc.cat_expr(expr));
155 self.delegate_consume(&place_with_id, place_with_id.hir_id);
156 self.walk_expr(expr);
159 fn mutate_expr(&mut self, expr: &hir::Expr<'_>) {
160 let place_with_id = return_if_err!(self.mc.cat_expr(expr));
161 self.delegate.mutate(&place_with_id, place_with_id.hir_id);
162 self.walk_expr(expr);
165 fn borrow_expr(&mut self, expr: &hir::Expr<'_>, bk: ty::BorrowKind) {
166 debug!("borrow_expr(expr={:?}, bk={:?})", expr, bk);
168 let place_with_id = return_if_err!(self.mc.cat_expr(expr));
169 self.delegate.borrow(&place_with_id, place_with_id.hir_id, bk);
174 fn select_from_expr(&mut self, expr: &hir::Expr<'_>) {
178 pub fn walk_expr(&mut self, expr: &hir::Expr<'_>) {
179 debug!("walk_expr(expr={:?})", expr);
181 self.walk_adjustment(expr);
184 hir::ExprKind::Path(_) => {}
186 hir::ExprKind::Type(ref subexpr, _) => self.walk_expr(subexpr),
188 hir::ExprKind::Unary(hir::UnOp::Deref, ref base) => {
190 self.select_from_expr(base);
193 hir::ExprKind::Field(ref base, _) => {
195 self.select_from_expr(base);
198 hir::ExprKind::Index(ref lhs, ref rhs) => {
200 self.select_from_expr(lhs);
201 self.consume_expr(rhs);
204 hir::ExprKind::Call(ref callee, ref args) => {
206 self.consume_expr(callee);
207 self.consume_exprs(args);
210 hir::ExprKind::MethodCall(.., ref args, _) => {
212 self.consume_exprs(args);
215 hir::ExprKind::Struct(_, ref fields, ref opt_with) => {
216 self.walk_struct_expr(fields, opt_with);
219 hir::ExprKind::Tup(ref exprs) => {
220 self.consume_exprs(exprs);
223 hir::ExprKind::If(ref cond_expr, ref then_expr, ref opt_else_expr) => {
224 self.consume_expr(&cond_expr);
225 self.consume_expr(&then_expr);
226 if let Some(ref else_expr) = *opt_else_expr {
227 self.consume_expr(&else_expr);
231 hir::ExprKind::Let(ref pat, ref expr, _) => {
232 self.walk_local(expr, pat, |t| t.borrow_expr(&expr, ty::ImmBorrow));
235 hir::ExprKind::Match(ref discr, arms, _) => {
236 let discr_place = return_if_err!(self.mc.cat_expr(&discr));
238 // Matching should not always be considered a use of the place, hence
239 // discr does not necessarily need to be borrowed.
240 // We only want to borrow discr if the pattern contain something other
242 let ExprUseVisitor { ref mc, body_owner: _, delegate: _ } = *self;
243 let mut needs_to_be_read = false;
244 for arm in arms.iter() {
245 return_if_err!(mc.cat_pattern(discr_place.clone(), &arm.pat, |place, pat| {
247 PatKind::Binding(.., opt_sub_pat) => {
248 // If the opt_sub_pat is None, than the binding does not count as
249 // a wildcard for the purpose of borrowing discr.
250 if opt_sub_pat.is_none() {
251 needs_to_be_read = true;
254 PatKind::TupleStruct(..)
256 | PatKind::Struct(..)
257 | PatKind::Tuple(..) => {
258 // If the PatKind is a TupleStruct, Path, Struct or Tuple then we want to check
259 // whether the Variant is a MultiVariant or a SingleVariant. We only want
260 // to borrow discr if it is a MultiVariant.
261 // If it is a SingleVariant and creates a binding we will handle that when
262 // this callback gets called again.
264 // Get the type of the Place after all projections have been applied
265 let place_ty = place.place.ty();
267 if let ty::Adt(def, _) = place_ty.kind() {
268 if def.variants.len() > 1 {
269 needs_to_be_read = true;
270 } else if let Some(variant) = def.variants.iter().next() {
271 // If the pat kind is a Path we want to check whether the
272 // variant contains at least one field. If that's the case,
273 // we want to borrow discr.
274 if matches!(pat.kind, PatKind::Path(..)) && variant.fields.len() > 0 {
275 needs_to_be_read = true;
279 // If it is not ty::Adt, then it should be read
280 needs_to_be_read = true;
283 PatKind::Lit(_) | PatKind::Range(..) => {
284 // If the PatKind is a Lit or a Range then we want
286 needs_to_be_read = true;
293 // If the PatKind is Or, Box, Slice or Ref, the decision is made later
294 // as these patterns contains subpatterns
295 // If the PatKind is Wild, the decision is made based on the other patterns being
302 if needs_to_be_read {
303 self.borrow_expr(&discr, ty::ImmBorrow);
305 let closure_def_id = match discr_place.place.base {
306 PlaceBase::Upvar(upvar_id) => Some(upvar_id.closure_expr_id.to_def_id()),
310 self.delegate.fake_read(
311 discr_place.place.clone(),
312 FakeReadCause::ForMatchedPlace(closure_def_id),
316 // We always want to walk the discriminant. We want to make sure, for instance,
317 // that the discriminant has been initialized.
318 self.walk_expr(&discr);
321 // treatment of the discriminant is handled while walking the arms.
323 self.walk_arm(&discr_place, arm);
327 hir::ExprKind::Array(ref exprs) => {
328 self.consume_exprs(exprs);
331 hir::ExprKind::AddrOf(_, m, ref base) => {
333 // make sure that the thing we are pointing out stays valid
334 // for the lifetime `scope_r` of the resulting ptr:
335 let bk = ty::BorrowKind::from_mutbl(m);
336 self.borrow_expr(&base, bk);
339 hir::ExprKind::InlineAsm(ref asm) => {
340 for (op, _op_sp) in asm.operands {
342 hir::InlineAsmOperand::In { expr, .. }
343 | hir::InlineAsmOperand::Sym { expr, .. } => self.consume_expr(expr),
344 hir::InlineAsmOperand::Out { expr, .. } => {
345 if let Some(expr) = expr {
346 self.mutate_expr(expr);
349 hir::InlineAsmOperand::InOut { expr, .. } => {
350 self.mutate_expr(expr);
352 hir::InlineAsmOperand::SplitInOut { in_expr, out_expr, .. } => {
353 self.consume_expr(in_expr);
354 if let Some(out_expr) = out_expr {
355 self.mutate_expr(out_expr);
358 hir::InlineAsmOperand::Const { .. } => {}
363 hir::ExprKind::LlvmInlineAsm(ref 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(ref blk, ..) => {
380 self.walk_block(blk);
383 hir::ExprKind::Unary(_, ref lhs) => {
384 self.consume_expr(lhs);
387 hir::ExprKind::Binary(_, ref lhs, ref rhs) => {
388 self.consume_expr(lhs);
389 self.consume_expr(rhs);
392 hir::ExprKind::Block(ref blk, _) => {
393 self.walk_block(blk);
396 hir::ExprKind::Break(_, ref opt_expr) | hir::ExprKind::Ret(ref opt_expr) => {
397 if let Some(ref expr) = *opt_expr {
398 self.consume_expr(expr);
402 hir::ExprKind::Assign(ref lhs, ref rhs, _) => {
403 self.mutate_expr(lhs);
404 self.consume_expr(rhs);
407 hir::ExprKind::Cast(ref base, _) => {
408 self.consume_expr(base);
411 hir::ExprKind::DropTemps(ref expr) => {
412 self.consume_expr(expr);
415 hir::ExprKind::AssignOp(_, ref lhs, ref 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(ref 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(ref value, _) => {
437 self.consume_expr(value);
442 fn walk_stmt(&mut self, stmt: &hir::Stmt<'_>) {
444 hir::StmtKind::Local(hir::Local { pat, init: Some(ref 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);
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(ref e)) = arm.guard {
624 self.consume_expr(&arm.body);
627 /// Walks a pat that occurs in isolation (i.e., top-level of fn argument or
628 /// let binding, and *not* a match arm or nested pat.)
629 fn walk_irrefutable_pat(&mut self, discr_place: &PlaceWithHirId<'tcx>, pat: &hir::Pat<'_>) {
630 let closure_def_id = match discr_place.place.base {
631 PlaceBase::Upvar(upvar_id) => Some(upvar_id.closure_expr_id.to_def_id()),
635 self.delegate.fake_read(
636 discr_place.place.clone(),
637 FakeReadCause::ForLet(closure_def_id),
640 self.walk_pat(discr_place, pat);
643 /// The core driver for walking a pattern
644 fn walk_pat(&mut self, discr_place: &PlaceWithHirId<'tcx>, pat: &hir::Pat<'_>) {
645 debug!("walk_pat(discr_place={:?}, pat={:?})", discr_place, pat);
647 let tcx = self.tcx();
648 let ExprUseVisitor { ref mc, body_owner: _, ref mut delegate } = *self;
649 return_if_err!(mc.cat_pattern(discr_place.clone(), pat, |place, pat| {
650 if let PatKind::Binding(_, canonical_id, ..) = pat.kind {
651 debug!("walk_pat: binding place={:?} pat={:?}", place, pat,);
653 mc.typeck_results.extract_binding_mode(tcx.sess, pat.hir_id, pat.span)
655 debug!("walk_pat: pat.hir_id={:?} bm={:?}", pat.hir_id, bm);
657 // pat_ty: the type of the binding being produced.
658 let pat_ty = return_if_err!(mc.node_ty(pat.hir_id));
659 debug!("walk_pat: pat_ty={:?}", pat_ty);
661 // Each match binding is effectively an assignment to the
662 // binding being produced.
663 let def = Res::Local(canonical_id);
664 if let Ok(ref binding_place) = mc.cat_res(pat.hir_id, pat.span, pat_ty, def) {
665 delegate.mutate(binding_place, binding_place.hir_id);
668 // It is also a borrow or copy/move of the value being matched.
669 // In a cases of pattern like `let pat = upvar`, don't use the span
670 // of the pattern, as this just looks confusing, instead use the span
671 // of the discriminant.
673 ty::BindByReference(m) => {
674 let bk = ty::BorrowKind::from_mutbl(m);
675 delegate.borrow(place, discr_place.hir_id, bk);
677 ty::BindByValue(..) => {
678 debug!("walk_pat binding consuming pat");
679 delegate_consume(mc, *delegate, place, discr_place.hir_id);
687 /// Handle the case where the current body contains a closure.
689 /// When the current body being handled is a closure, then we must make sure that
690 /// - The parent closure only captures Places from the nested closure that are not local to it.
692 /// In the following example the closures `c` only captures `p.x` even though `incr`
693 /// is a capture of the nested closure
695 /// ```rust,ignore(cannot-test-this-because-pseudo-code)
699 /// let nested = || p.x += incr;
703 /// - When reporting the Place back to the Delegate, ensure that the UpvarId uses the enclosing
704 /// closure as the DefId.
705 fn walk_captures(&mut self, closure_expr: &hir::Expr<'_>) {
706 fn upvar_is_local_variable(
707 upvars: Option<&'tcx FxIndexMap<hir::HirId, hir::Upvar>>,
708 upvar_id: &hir::HirId,
709 body_owner_is_closure: bool,
711 upvars.map(|upvars| !upvars.contains_key(upvar_id)).unwrap_or(body_owner_is_closure)
714 debug!("walk_captures({:?})", closure_expr);
716 let closure_def_id = self.tcx().hir().local_def_id(closure_expr.hir_id).to_def_id();
717 let upvars = self.tcx().upvars_mentioned(self.body_owner);
719 // For purposes of this function, generator and closures are equivalent.
720 let body_owner_is_closure = matches!(
721 self.tcx().type_of(self.body_owner.to_def_id()).kind(),
722 ty::Closure(..) | ty::Generator(..)
725 // If we have a nested closure, we want to include the fake reads present in the nested closure.
726 if let Some(fake_reads) = self.mc.typeck_results.closure_fake_reads.get(&closure_def_id) {
727 for (fake_read, cause, hir_id) in fake_reads.iter() {
728 match fake_read.base {
729 PlaceBase::Upvar(upvar_id) => {
730 if upvar_is_local_variable(
732 &upvar_id.var_path.hir_id,
733 body_owner_is_closure,
735 // The nested closure might be fake reading the current (enclosing) closure's local variables.
736 // The only places we want to fake read before creating the parent closure are the ones that
737 // are not local to it/ defined by it.
739 // ```rust,ignore(cannot-test-this-because-pseudo-code)
741 // let c = || { // fake reads: v1
743 // let e = || { // fake reads: v1, v2
749 // This check is performed when visiting the body of the outermost closure (`c`) and ensures
750 // that we don't add a fake read of v2 in c.
756 "Do not know how to get HirId out of Rvalue and StaticItem {:?}",
761 self.delegate.fake_read(fake_read.clone(), *cause, *hir_id);
765 if let Some(min_captures) = self.mc.typeck_results.closure_min_captures.get(&closure_def_id)
767 for (var_hir_id, min_list) in min_captures.iter() {
768 if upvars.map_or(body_owner_is_closure, |upvars| !upvars.contains_key(var_hir_id)) {
769 // The nested closure might be capturing the current (enclosing) closure's local variables.
770 // We check if the root variable is ever mentioned within the enclosing closure, if not
771 // then for the current body (if it's a closure) these aren't captures, we will ignore them.
774 for captured_place in min_list {
775 let place = &captured_place.place;
776 let capture_info = captured_place.info;
778 let place_base = if body_owner_is_closure {
779 // Mark the place to be captured by the enclosing closure
780 PlaceBase::Upvar(ty::UpvarId::new(*var_hir_id, self.body_owner))
782 // If the body owner isn't a closure then the variable must
783 // be a local variable
784 PlaceBase::Local(*var_hir_id)
786 let place_with_id = PlaceWithHirId::new(
787 capture_info.path_expr_id.unwrap_or(
788 capture_info.capture_kind_expr_id.unwrap_or(closure_expr.hir_id),
792 place.projections.clone(),
795 match capture_info.capture_kind {
796 ty::UpvarCapture::ByValue(_) => {
797 self.delegate_consume(&place_with_id, place_with_id.hir_id);
799 ty::UpvarCapture::ByRef(upvar_borrow) => {
800 self.delegate.borrow(
802 place_with_id.hir_id,
813 fn copy_or_move<'a, 'tcx>(
814 mc: &mc::MemCategorizationContext<'a, 'tcx>,
815 place_with_id: &PlaceWithHirId<'tcx>,
817 if !mc.type_is_copy_modulo_regions(
818 place_with_id.place.ty(),
819 mc.tcx().hir().span(place_with_id.hir_id),
827 // - If a place is used in a `ByValue` context then move it if it's not a `Copy` type.
828 // - If the place that is a `Copy` type consider it an `ImmBorrow`.
829 fn delegate_consume<'a, 'tcx>(
830 mc: &mc::MemCategorizationContext<'a, 'tcx>,
831 delegate: &mut (dyn Delegate<'tcx> + 'a),
832 place_with_id: &PlaceWithHirId<'tcx>,
833 diag_expr_id: hir::HirId,
835 debug!("delegate_consume(place_with_id={:?})", place_with_id);
837 let mode = copy_or_move(&mc, place_with_id);
840 ConsumeMode::Move => delegate.consume(place_with_id, diag_expr_id),
841 ConsumeMode::Copy => {
842 delegate.borrow(place_with_id, diag_expr_id, ty::BorrowKind::ImmBorrow)