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 path at `assignee_place` is being assigned to.
51 /// `diag_expr_id` is the id used for diagnostics (see `consume` for more details).
52 fn mutate(&mut self, assignee_place: &PlaceWithHirId<'tcx>, diag_expr_id: hir::HirId);
54 /// The path at `binding_place` is a binding that is being initialized.
56 /// This covers cases such as `let x = 42;`
57 fn bind(&mut self, binding_place: &PlaceWithHirId<'tcx>, diag_expr_id: hir::HirId) {
58 // Bindings can normally be treated as a regular assignment, so by default we
59 // forward this to the mutate callback.
60 self.mutate(binding_place, diag_expr_id)
63 /// The `place` should be a fake read because of specified `cause`.
64 fn fake_read(&mut self, place: Place<'tcx>, cause: FakeReadCause, diag_expr_id: hir::HirId);
67 #[derive(Copy, Clone, PartialEq, Debug)]
69 /// reference to x where x has a type that copies
71 /// reference to x where x has a type that moves
75 #[derive(Copy, Clone, PartialEq, Debug)]
84 /// The ExprUseVisitor type
86 /// This is the code that actually walks the tree.
87 pub struct ExprUseVisitor<'a, 'tcx> {
88 mc: mc::MemCategorizationContext<'a, 'tcx>,
89 body_owner: LocalDefId,
90 delegate: &'a mut dyn Delegate<'tcx>,
93 /// If the MC results in an error, it's because the type check
94 /// failed (or will fail, when the error is uncovered and reported
95 /// during writeback). In this case, we just ignore this part of the
98 /// Note that this macro appears similar to try!(), but, unlike try!(),
99 /// it does not propagate the error.
100 macro_rules! return_if_err {
105 debug!("mc reported err");
112 impl<'a, 'tcx> ExprUseVisitor<'a, 'tcx> {
113 /// Creates the ExprUseVisitor, configuring it with the various options provided:
115 /// - `delegate` -- who receives the callbacks
116 /// - `param_env` --- parameter environment for trait lookups (esp. pertaining to `Copy`)
117 /// - `typeck_results` --- typeck results for the code being analyzed
119 delegate: &'a mut (dyn Delegate<'tcx> + 'a),
120 infcx: &'a InferCtxt<'a, 'tcx>,
121 body_owner: LocalDefId,
122 param_env: ty::ParamEnv<'tcx>,
123 typeck_results: &'a ty::TypeckResults<'tcx>,
126 mc: mc::MemCategorizationContext::new(infcx, param_env, body_owner, typeck_results),
132 #[instrument(skip(self), level = "debug")]
133 pub fn consume_body(&mut self, body: &hir::Body<'_>) {
134 for param in body.params {
135 let param_ty = return_if_err!(self.mc.pat_ty_adjusted(param.pat));
136 debug!("consume_body: param_ty = {:?}", param_ty);
138 let param_place = self.mc.cat_rvalue(param.hir_id, param.pat.span, param_ty);
140 self.walk_irrefutable_pat(¶m_place, param.pat);
143 self.consume_expr(&body.value);
146 fn tcx(&self) -> TyCtxt<'tcx> {
150 fn delegate_consume(&mut self, place_with_id: &PlaceWithHirId<'tcx>, diag_expr_id: hir::HirId) {
151 delegate_consume(&self.mc, self.delegate, place_with_id, diag_expr_id)
154 fn consume_exprs(&mut self, exprs: &[hir::Expr<'_>]) {
156 self.consume_expr(expr);
160 pub fn consume_expr(&mut self, expr: &hir::Expr<'_>) {
161 debug!("consume_expr(expr={:?})", expr);
163 let place_with_id = return_if_err!(self.mc.cat_expr(expr));
164 self.delegate_consume(&place_with_id, place_with_id.hir_id);
165 self.walk_expr(expr);
168 fn mutate_expr(&mut self, expr: &hir::Expr<'_>) {
169 let place_with_id = return_if_err!(self.mc.cat_expr(expr));
170 self.delegate.mutate(&place_with_id, place_with_id.hir_id);
171 self.walk_expr(expr);
174 fn borrow_expr(&mut self, expr: &hir::Expr<'_>, bk: ty::BorrowKind) {
175 debug!("borrow_expr(expr={:?}, bk={:?})", expr, bk);
177 let place_with_id = return_if_err!(self.mc.cat_expr(expr));
178 self.delegate.borrow(&place_with_id, place_with_id.hir_id, bk);
183 fn select_from_expr(&mut self, expr: &hir::Expr<'_>) {
187 pub fn walk_expr(&mut self, expr: &hir::Expr<'_>) {
188 debug!("walk_expr(expr={:?})", expr);
190 self.walk_adjustment(expr);
193 hir::ExprKind::Path(_) => {}
195 hir::ExprKind::Type(subexpr, _) => self.walk_expr(subexpr),
197 hir::ExprKind::Unary(hir::UnOp::Deref, base) => {
199 self.select_from_expr(base);
202 hir::ExprKind::Field(base, _) => {
204 self.select_from_expr(base);
207 hir::ExprKind::Index(lhs, rhs) => {
209 self.select_from_expr(lhs);
210 self.consume_expr(rhs);
213 hir::ExprKind::Call(callee, args) => {
215 self.consume_expr(callee);
216 self.consume_exprs(args);
219 hir::ExprKind::MethodCall(.., args, _) => {
221 self.consume_exprs(args);
224 hir::ExprKind::Struct(_, fields, ref opt_with) => {
225 self.walk_struct_expr(fields, opt_with);
228 hir::ExprKind::Tup(exprs) => {
229 self.consume_exprs(exprs);
232 hir::ExprKind::If(ref cond_expr, ref then_expr, ref opt_else_expr) => {
233 self.consume_expr(cond_expr);
234 self.consume_expr(then_expr);
235 if let Some(ref else_expr) = *opt_else_expr {
236 self.consume_expr(else_expr);
240 hir::ExprKind::Let(hir::Let { pat, init, .. }) => {
241 self.walk_local(init, pat, |t| t.borrow_expr(init, ty::ImmBorrow));
244 hir::ExprKind::Match(ref discr, arms, _) => {
245 let discr_place = return_if_err!(self.mc.cat_expr(discr));
247 // Matching should not always be considered a use of the place, hence
248 // discr does not necessarily need to be borrowed.
249 // We only want to borrow discr if the pattern contain something other
251 let ExprUseVisitor { ref mc, body_owner: _, delegate: _ } = *self;
252 let mut needs_to_be_read = false;
253 for arm in arms.iter() {
254 return_if_err!(mc.cat_pattern(discr_place.clone(), arm.pat, |place, pat| {
256 PatKind::Binding(.., opt_sub_pat) => {
257 // If the opt_sub_pat is None, than the binding does not count as
258 // a wildcard for the purpose of borrowing discr.
259 if opt_sub_pat.is_none() {
260 needs_to_be_read = true;
263 PatKind::Path(qpath) => {
264 // A `Path` pattern is just a name like `Foo`. This is either a
265 // named constant or else it refers to an ADT variant
267 let res = self.mc.typeck_results.qpath_res(qpath, pat.hir_id);
269 Res::Def(DefKind::Const, _)
270 | Res::Def(DefKind::AssocConst, _) => {
271 // Named constants have to be equated with the value
272 // being matched, so that's a read of the value being matched.
274 // FIXME: We don't actually reads for ZSTs.
275 needs_to_be_read = true;
278 // Otherwise, this is a struct/enum variant, and so it's
279 // only a read if we need to read the discriminant.
280 needs_to_be_read |= is_multivariant_adt(place.place.ty());
284 PatKind::TupleStruct(..) | PatKind::Struct(..) | PatKind::Tuple(..) => {
285 // For `Foo(..)`, `Foo { ... }` and `(...)` patterns, check if we are matching
286 // against a multivariant enum or struct. In that case, we have to read
287 // the discriminant. Otherwise this kind of pattern doesn't actually
288 // read anything (we'll get invoked for the `...`, which may indeed
289 // perform some reads).
291 let place_ty = place.place.ty();
292 needs_to_be_read |= is_multivariant_adt(place_ty);
294 PatKind::Lit(_) | PatKind::Range(..) => {
295 // If the PatKind is a Lit or a Range then we want
297 needs_to_be_read = true;
304 // If the PatKind is Or, Box, Slice or Ref, the decision is made later
305 // as these patterns contains subpatterns
306 // If the PatKind is Wild, the decision is made based on the other patterns being
313 if needs_to_be_read {
314 self.borrow_expr(discr, ty::ImmBorrow);
316 let closure_def_id = match discr_place.place.base {
317 PlaceBase::Upvar(upvar_id) => Some(upvar_id.closure_expr_id.to_def_id()),
321 self.delegate.fake_read(
322 discr_place.place.clone(),
323 FakeReadCause::ForMatchedPlace(closure_def_id),
327 // We always want to walk the discriminant. We want to make sure, for instance,
328 // that the discriminant has been initialized.
329 self.walk_expr(discr);
332 // treatment of the discriminant is handled while walking the arms.
334 self.walk_arm(&discr_place, arm);
338 hir::ExprKind::Array(exprs) => {
339 self.consume_exprs(exprs);
342 hir::ExprKind::AddrOf(_, m, ref base) => {
344 // make sure that the thing we are pointing out stays valid
345 // for the lifetime `scope_r` of the resulting ptr:
346 let bk = ty::BorrowKind::from_mutbl(m);
347 self.borrow_expr(base, bk);
350 hir::ExprKind::InlineAsm(asm) => {
351 for (op, _op_sp) in asm.operands {
353 hir::InlineAsmOperand::In { expr, .. }
354 | hir::InlineAsmOperand::Sym { expr, .. } => self.consume_expr(expr),
355 hir::InlineAsmOperand::Out { expr: Some(expr), .. }
356 | hir::InlineAsmOperand::InOut { expr, .. } => {
357 self.mutate_expr(expr);
359 hir::InlineAsmOperand::SplitInOut { in_expr, out_expr, .. } => {
360 self.consume_expr(in_expr);
361 if let Some(out_expr) = out_expr {
362 self.mutate_expr(out_expr);
365 hir::InlineAsmOperand::Out { expr: None, .. }
366 | hir::InlineAsmOperand::Const { .. } => {}
371 hir::ExprKind::Continue(..)
372 | hir::ExprKind::Lit(..)
373 | hir::ExprKind::ConstBlock(..)
374 | hir::ExprKind::Err => {}
376 hir::ExprKind::Loop(blk, ..) => {
377 self.walk_block(blk);
380 hir::ExprKind::Unary(_, lhs) => {
381 self.consume_expr(lhs);
384 hir::ExprKind::Binary(_, lhs, rhs) => {
385 self.consume_expr(lhs);
386 self.consume_expr(rhs);
389 hir::ExprKind::Block(blk, _) => {
390 self.walk_block(blk);
393 hir::ExprKind::Break(_, ref opt_expr) | hir::ExprKind::Ret(ref opt_expr) => {
394 if let Some(expr) = *opt_expr {
395 self.consume_expr(expr);
399 hir::ExprKind::Assign(lhs, rhs, _) => {
400 self.mutate_expr(lhs);
401 self.consume_expr(rhs);
404 hir::ExprKind::Cast(base, _) => {
405 self.consume_expr(base);
408 hir::ExprKind::DropTemps(expr) => {
409 self.consume_expr(expr);
412 hir::ExprKind::AssignOp(_, lhs, rhs) => {
413 if self.mc.typeck_results.is_method_call(expr) {
414 self.consume_expr(lhs);
416 self.mutate_expr(lhs);
418 self.consume_expr(rhs);
421 hir::ExprKind::Repeat(base, _) => {
422 self.consume_expr(base);
425 hir::ExprKind::Closure(..) => {
426 self.walk_captures(expr);
429 hir::ExprKind::Box(ref base) => {
430 self.consume_expr(base);
433 hir::ExprKind::Yield(value, _) => {
434 self.consume_expr(value);
439 fn walk_stmt(&mut self, stmt: &hir::Stmt<'_>) {
441 hir::StmtKind::Local(hir::Local { pat, init: Some(expr), .. }) => {
442 self.walk_local(expr, pat, |_| {});
445 hir::StmtKind::Local(_) => {}
447 hir::StmtKind::Item(_) => {
448 // We don't visit nested items in this visitor,
449 // only the fn body we were given.
452 hir::StmtKind::Expr(ref expr) | hir::StmtKind::Semi(ref expr) => {
453 self.consume_expr(expr);
458 fn walk_local<F>(&mut self, expr: &hir::Expr<'_>, pat: &hir::Pat<'_>, mut f: F)
462 self.walk_expr(expr);
463 let expr_place = return_if_err!(self.mc.cat_expr(expr));
465 self.walk_irrefutable_pat(&expr_place, &pat);
468 /// Indicates that the value of `blk` will be consumed, meaning either copied or moved
469 /// depending on its type.
470 fn walk_block(&mut self, blk: &hir::Block<'_>) {
471 debug!("walk_block(blk.hir_id={})", blk.hir_id);
473 for stmt in blk.stmts {
474 self.walk_stmt(stmt);
477 if let Some(ref tail_expr) = blk.expr {
478 self.consume_expr(tail_expr);
482 fn walk_struct_expr<'hir>(
484 fields: &[hir::ExprField<'_>],
485 opt_with: &Option<&'hir hir::Expr<'_>>,
487 // Consume the expressions supplying values for each field.
488 for field in fields {
489 self.consume_expr(field.expr);
492 let with_expr = match *opt_with {
499 let with_place = return_if_err!(self.mc.cat_expr(with_expr));
501 // Select just those fields of the `with`
502 // expression that will actually be used
503 match with_place.place.ty().kind() {
504 ty::Adt(adt, substs) if adt.is_struct() => {
505 // Consume those fields of the with expression that are needed.
506 for (f_index, with_field) in adt.non_enum_variant().fields.iter().enumerate() {
507 let is_mentioned = fields.iter().any(|f| {
508 self.tcx().field_index(f.hir_id, self.mc.typeck_results) == f_index
511 let field_place = self.mc.cat_projection(
514 with_field.ty(self.tcx(), substs),
515 ProjectionKind::Field(f_index as u32, VariantIdx::new(0)),
517 self.delegate_consume(&field_place, field_place.hir_id);
522 // the base expression should always evaluate to a
523 // struct; however, when EUV is run during typeck, it
524 // may not. This will generate an error earlier in typeck,
525 // so we can just ignore it.
526 if !self.tcx().sess.has_errors() {
527 span_bug!(with_expr.span, "with expression doesn't evaluate to a struct");
532 // walk the with expression so that complex expressions
533 // are properly handled.
534 self.walk_expr(with_expr);
537 /// Invoke the appropriate delegate calls for anything that gets
538 /// consumed or borrowed as part of the automatic adjustment
540 fn walk_adjustment(&mut self, expr: &hir::Expr<'_>) {
541 let adjustments = self.mc.typeck_results.expr_adjustments(expr);
542 let mut place_with_id = return_if_err!(self.mc.cat_expr_unadjusted(expr));
543 for adjustment in adjustments {
544 debug!("walk_adjustment expr={:?} adj={:?}", expr, adjustment);
545 match adjustment.kind {
546 adjustment::Adjust::NeverToAny | adjustment::Adjust::Pointer(_) => {
547 // Creating a closure/fn-pointer or unsizing consumes
548 // the input and stores it into the resulting rvalue.
549 self.delegate_consume(&place_with_id, place_with_id.hir_id);
552 adjustment::Adjust::Deref(None) => {}
554 // Autoderefs for overloaded Deref calls in fact reference
555 // their receiver. That is, if we have `(*x)` where `x`
556 // is of type `Rc<T>`, then this in fact is equivalent to
557 // `x.deref()`. Since `deref()` is declared with `&self`,
558 // this is an autoref of `x`.
559 adjustment::Adjust::Deref(Some(ref deref)) => {
560 let bk = ty::BorrowKind::from_mutbl(deref.mutbl);
561 self.delegate.borrow(&place_with_id, place_with_id.hir_id, bk);
564 adjustment::Adjust::Borrow(ref autoref) => {
565 self.walk_autoref(expr, &place_with_id, autoref);
569 return_if_err!(self.mc.cat_expr_adjusted(expr, place_with_id, adjustment));
573 /// Walks the autoref `autoref` applied to the autoderef'd
574 /// `expr`. `base_place` is the mem-categorized form of `expr`
575 /// after all relevant autoderefs have occurred.
578 expr: &hir::Expr<'_>,
579 base_place: &PlaceWithHirId<'tcx>,
580 autoref: &adjustment::AutoBorrow<'tcx>,
583 "walk_autoref(expr.hir_id={} base_place={:?} autoref={:?})",
584 expr.hir_id, base_place, autoref
588 adjustment::AutoBorrow::Ref(_, m) => {
589 self.delegate.borrow(
592 ty::BorrowKind::from_mutbl(m.into()),
596 adjustment::AutoBorrow::RawPtr(m) => {
597 debug!("walk_autoref: expr.hir_id={} base_place={:?}", expr.hir_id, base_place);
599 self.delegate.borrow(base_place, base_place.hir_id, ty::BorrowKind::from_mutbl(m));
604 fn walk_arm(&mut self, discr_place: &PlaceWithHirId<'tcx>, arm: &hir::Arm<'_>) {
605 let closure_def_id = match discr_place.place.base {
606 PlaceBase::Upvar(upvar_id) => Some(upvar_id.closure_expr_id.to_def_id()),
610 self.delegate.fake_read(
611 discr_place.place.clone(),
612 FakeReadCause::ForMatchedPlace(closure_def_id),
615 self.walk_pat(discr_place, arm.pat);
617 if let Some(hir::Guard::If(e)) = arm.guard {
619 } else if let Some(hir::Guard::IfLet(_, ref e)) = arm.guard {
623 self.consume_expr(arm.body);
626 /// Walks a pat that occurs in isolation (i.e., top-level of fn argument or
627 /// let binding, and *not* a match arm or nested pat.)
628 fn walk_irrefutable_pat(&mut self, discr_place: &PlaceWithHirId<'tcx>, pat: &hir::Pat<'_>) {
629 let closure_def_id = match discr_place.place.base {
630 PlaceBase::Upvar(upvar_id) => Some(upvar_id.closure_expr_id.to_def_id()),
634 self.delegate.fake_read(
635 discr_place.place.clone(),
636 FakeReadCause::ForLet(closure_def_id),
639 self.walk_pat(discr_place, pat);
642 /// The core driver for walking a pattern
643 fn walk_pat(&mut self, discr_place: &PlaceWithHirId<'tcx>, pat: &hir::Pat<'_>) {
644 debug!("walk_pat(discr_place={:?}, pat={:?})", discr_place, pat);
646 let tcx = self.tcx();
647 let ExprUseVisitor { ref mc, body_owner: _, ref mut delegate } = *self;
648 return_if_err!(mc.cat_pattern(discr_place.clone(), pat, |place, pat| {
649 if let PatKind::Binding(_, canonical_id, ..) = pat.kind {
650 debug!("walk_pat: binding place={:?} pat={:?}", place, pat,);
652 mc.typeck_results.extract_binding_mode(tcx.sess, pat.hir_id, pat.span)
654 debug!("walk_pat: pat.hir_id={:?} bm={:?}", pat.hir_id, bm);
656 // pat_ty: the type of the binding being produced.
657 let pat_ty = return_if_err!(mc.node_ty(pat.hir_id));
658 debug!("walk_pat: pat_ty={:?}", pat_ty);
660 let def = Res::Local(canonical_id);
661 if let Ok(ref binding_place) = mc.cat_res(pat.hir_id, pat.span, pat_ty, def) {
662 delegate.bind(binding_place, binding_place.hir_id);
665 // It is also a borrow or copy/move of the value being matched.
666 // In a cases of pattern like `let pat = upvar`, don't use the span
667 // of the pattern, as this just looks confusing, instead use the span
668 // of the discriminant.
670 ty::BindByReference(m) => {
671 let bk = ty::BorrowKind::from_mutbl(m);
672 delegate.borrow(place, discr_place.hir_id, bk);
674 ty::BindByValue(..) => {
675 debug!("walk_pat binding consuming pat");
676 delegate_consume(mc, *delegate, place, discr_place.hir_id);
684 /// Handle the case where the current body contains a closure.
686 /// When the current body being handled is a closure, then we must make sure that
687 /// - The parent closure only captures Places from the nested closure that are not local to it.
689 /// In the following example the closures `c` only captures `p.x` even though `incr`
690 /// is a capture of the nested closure
692 /// ```rust,ignore(cannot-test-this-because-pseudo-code)
696 /// let nested = || p.x += incr;
700 /// - When reporting the Place back to the Delegate, ensure that the UpvarId uses the enclosing
701 /// closure as the DefId.
702 fn walk_captures(&mut self, closure_expr: &hir::Expr<'_>) {
703 fn upvar_is_local_variable<'tcx>(
704 upvars: Option<&'tcx FxIndexMap<hir::HirId, hir::Upvar>>,
705 upvar_id: &hir::HirId,
706 body_owner_is_closure: bool,
708 upvars.map(|upvars| !upvars.contains_key(upvar_id)).unwrap_or(body_owner_is_closure)
711 debug!("walk_captures({:?})", closure_expr);
713 let tcx = self.tcx();
714 let closure_def_id = tcx.hir().local_def_id(closure_expr.hir_id).to_def_id();
715 let upvars = tcx.upvars_mentioned(self.body_owner);
717 // For purposes of this function, generator and closures are equivalent.
718 let body_owner_is_closure = matches!(
719 tcx.hir().body_owner_kind(tcx.hir().local_def_id_to_hir_id(self.body_owner)),
720 hir::BodyOwnerKind::Closure,
723 // If we have a nested closure, we want to include the fake reads present in the nested closure.
724 if let Some(fake_reads) = self.mc.typeck_results.closure_fake_reads.get(&closure_def_id) {
725 for (fake_read, cause, hir_id) in fake_reads.iter() {
726 match fake_read.base {
727 PlaceBase::Upvar(upvar_id) => {
728 if upvar_is_local_variable(
730 &upvar_id.var_path.hir_id,
731 body_owner_is_closure,
733 // The nested closure might be fake reading the current (enclosing) closure's local variables.
734 // The only places we want to fake read before creating the parent closure are the ones that
735 // are not local to it/ defined by it.
737 // ```rust,ignore(cannot-test-this-because-pseudo-code)
739 // let c = || { // fake reads: v1
741 // let e = || { // fake reads: v1, v2
747 // This check is performed when visiting the body of the outermost closure (`c`) and ensures
748 // that we don't add a fake read of v2 in c.
754 "Do not know how to get HirId out of Rvalue and StaticItem {:?}",
759 self.delegate.fake_read(fake_read.clone(), *cause, *hir_id);
763 if let Some(min_captures) = self.mc.typeck_results.closure_min_captures.get(&closure_def_id)
765 for (var_hir_id, min_list) in min_captures.iter() {
766 if upvars.map_or(body_owner_is_closure, |upvars| !upvars.contains_key(var_hir_id)) {
767 // The nested closure might be capturing the current (enclosing) closure's local variables.
768 // We check if the root variable is ever mentioned within the enclosing closure, if not
769 // then for the current body (if it's a closure) these aren't captures, we will ignore them.
772 for captured_place in min_list {
773 let place = &captured_place.place;
774 let capture_info = captured_place.info;
776 let place_base = if body_owner_is_closure {
777 // Mark the place to be captured by the enclosing closure
778 PlaceBase::Upvar(ty::UpvarId::new(*var_hir_id, self.body_owner))
780 // If the body owner isn't a closure then the variable must
781 // be a local variable
782 PlaceBase::Local(*var_hir_id)
784 let place_with_id = PlaceWithHirId::new(
785 capture_info.path_expr_id.unwrap_or(
786 capture_info.capture_kind_expr_id.unwrap_or(closure_expr.hir_id),
790 place.projections.clone(),
793 match capture_info.capture_kind {
794 ty::UpvarCapture::ByValue => {
795 self.delegate_consume(&place_with_id, place_with_id.hir_id);
797 ty::UpvarCapture::ByRef(upvar_borrow) => {
798 self.delegate.borrow(
800 place_with_id.hir_id,
811 fn copy_or_move<'a, 'tcx>(
812 mc: &mc::MemCategorizationContext<'a, 'tcx>,
813 place_with_id: &PlaceWithHirId<'tcx>,
815 if !mc.type_is_copy_modulo_regions(
816 place_with_id.place.ty(),
817 mc.tcx().hir().span(place_with_id.hir_id),
825 // - If a place is used in a `ByValue` context then move it if it's not a `Copy` type.
826 // - If the place that is a `Copy` type consider it an `ImmBorrow`.
827 fn delegate_consume<'a, 'tcx>(
828 mc: &mc::MemCategorizationContext<'a, 'tcx>,
829 delegate: &mut (dyn Delegate<'tcx> + 'a),
830 place_with_id: &PlaceWithHirId<'tcx>,
831 diag_expr_id: hir::HirId,
833 debug!("delegate_consume(place_with_id={:?})", place_with_id);
835 let mode = copy_or_move(mc, place_with_id);
838 ConsumeMode::Move => delegate.consume(place_with_id, diag_expr_id),
839 ConsumeMode::Copy => {
840 delegate.borrow(place_with_id, diag_expr_id, ty::BorrowKind::ImmBorrow)
845 fn is_multivariant_adt(ty: Ty<'_>) -> bool {
846 if let ty::Adt(def, _) = ty.kind() {
847 // Note that if a non-exhaustive SingleVariant is defined in another crate, we need
848 // to assume that more cases will be added to the variant in the future. This mean
849 // that we should handle non-exhaustive SingleVariant the same way we would handle
851 // If the variant is not local it must be defined in another crate.
852 let is_non_exhaustive = match def.adt_kind() {
853 AdtKind::Struct | AdtKind::Union => {
854 def.non_enum_variant().is_field_list_non_exhaustive()
856 AdtKind::Enum => def.is_variant_list_non_exhaustive(),
858 def.variants.len() > 1 || (!def.did.is_local() && is_non_exhaustive)