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 `place` should be a fake read because of specified `cause`.
55 fn fake_read(&mut self, place: Place<'tcx>, cause: FakeReadCause, diag_expr_id: hir::HirId);
58 #[derive(Copy, Clone, PartialEq, Debug)]
60 /// reference to x where x has a type that copies
62 /// reference to x where x has a type that moves
66 #[derive(Copy, Clone, PartialEq, Debug)]
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(param.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, param.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(subexpr, _) => self.walk_expr(subexpr),
188 hir::ExprKind::Unary(hir::UnOp::Deref, base) => {
190 self.select_from_expr(base);
193 hir::ExprKind::Field(base, _) => {
195 self.select_from_expr(base);
198 hir::ExprKind::Index(lhs, rhs) => {
200 self.select_from_expr(lhs);
201 self.consume_expr(rhs);
204 hir::ExprKind::Call(callee, args) => {
206 self.consume_expr(callee);
207 self.consume_exprs(args);
210 hir::ExprKind::MethodCall(.., args, _) => {
212 self.consume_exprs(args);
215 hir::ExprKind::Struct(_, fields, ref opt_with) => {
216 self.walk_struct_expr(fields, opt_with);
219 hir::ExprKind::Tup(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(hir::Let { pat, init, .. }) => {
232 self.walk_local(init, pat, |t| t.borrow_expr(init, 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::Path(qpath) => {
255 // A `Path` pattern is just a name like `Foo`. This is either a
256 // named constant or else it refers to an ADT variant
258 let res = self.mc.typeck_results.qpath_res(qpath, pat.hir_id);
260 Res::Def(DefKind::Const, _)
261 | Res::Def(DefKind::AssocConst, _) => {
262 // Named constants have to be equated with the value
263 // being matched, so that's a read of the value being matched.
265 // FIXME: We don't actually reads for ZSTs.
266 needs_to_be_read = true;
269 // Otherwise, this is a struct/enum variant, and so it's
270 // only a read if we need to read the discriminant.
271 needs_to_be_read |= is_multivariant_adt(place.place.ty());
275 PatKind::TupleStruct(..) | PatKind::Struct(..) | PatKind::Tuple(..) => {
276 // For `Foo(..)`, `Foo { ... }` and `(...)` patterns, check if we are matching
277 // against a multivariant enum or struct. In that case, we have to read
278 // the discriminant. Otherwise this kind of pattern doesn't actually
279 // read anything (we'll get invoked for the `...`, which may indeed
280 // perform some reads).
282 let place_ty = place.place.ty();
283 needs_to_be_read |= is_multivariant_adt(place_ty);
285 PatKind::Lit(_) | PatKind::Range(..) => {
286 // If the PatKind is a Lit or a Range then we want
288 needs_to_be_read = true;
295 // If the PatKind is Or, Box, Slice or Ref, the decision is made later
296 // as these patterns contains subpatterns
297 // If the PatKind is Wild, the decision is made based on the other patterns being
304 if needs_to_be_read {
305 self.borrow_expr(discr, ty::ImmBorrow);
307 let closure_def_id = match discr_place.place.base {
308 PlaceBase::Upvar(upvar_id) => Some(upvar_id.closure_expr_id.to_def_id()),
312 self.delegate.fake_read(
313 discr_place.place.clone(),
314 FakeReadCause::ForMatchedPlace(closure_def_id),
318 // We always want to walk the discriminant. We want to make sure, for instance,
319 // that the discriminant has been initialized.
320 self.walk_expr(discr);
323 // treatment of the discriminant is handled while walking the arms.
325 self.walk_arm(&discr_place, arm);
329 hir::ExprKind::Array(exprs) => {
330 self.consume_exprs(exprs);
333 hir::ExprKind::AddrOf(_, m, ref base) => {
335 // make sure that the thing we are pointing out stays valid
336 // for the lifetime `scope_r` of the resulting ptr:
337 let bk = ty::BorrowKind::from_mutbl(m);
338 self.borrow_expr(base, bk);
341 hir::ExprKind::InlineAsm(asm) => {
342 for (op, _op_sp) in asm.operands {
344 hir::InlineAsmOperand::In { expr, .. }
345 | hir::InlineAsmOperand::Sym { expr, .. } => self.consume_expr(expr),
346 hir::InlineAsmOperand::Out { expr: Some(expr), .. }
347 | hir::InlineAsmOperand::InOut { expr, .. } => {
348 self.mutate_expr(expr);
350 hir::InlineAsmOperand::SplitInOut { in_expr, out_expr, .. } => {
351 self.consume_expr(in_expr);
352 if let Some(out_expr) = out_expr {
353 self.mutate_expr(out_expr);
356 hir::InlineAsmOperand::Out { expr: None, .. }
357 | hir::InlineAsmOperand::Const { .. } => {}
362 hir::ExprKind::Continue(..)
363 | hir::ExprKind::Lit(..)
364 | hir::ExprKind::ConstBlock(..)
365 | hir::ExprKind::Err => {}
367 hir::ExprKind::Loop(blk, ..) => {
368 self.walk_block(blk);
371 hir::ExprKind::Unary(_, lhs) => {
372 self.consume_expr(lhs);
375 hir::ExprKind::Binary(_, lhs, rhs) => {
376 self.consume_expr(lhs);
377 self.consume_expr(rhs);
380 hir::ExprKind::Block(blk, _) => {
381 self.walk_block(blk);
384 hir::ExprKind::Break(_, ref opt_expr) | hir::ExprKind::Ret(ref opt_expr) => {
385 if let Some(expr) = *opt_expr {
386 self.consume_expr(expr);
390 hir::ExprKind::Assign(lhs, rhs, _) => {
391 self.mutate_expr(lhs);
392 self.consume_expr(rhs);
395 hir::ExprKind::Cast(base, _) => {
396 self.consume_expr(base);
399 hir::ExprKind::DropTemps(expr) => {
400 self.consume_expr(expr);
403 hir::ExprKind::AssignOp(_, lhs, rhs) => {
404 if self.mc.typeck_results.is_method_call(expr) {
405 self.consume_expr(lhs);
407 self.mutate_expr(lhs);
409 self.consume_expr(rhs);
412 hir::ExprKind::Repeat(base, _) => {
413 self.consume_expr(base);
416 hir::ExprKind::Closure(..) => {
417 self.walk_captures(expr);
420 hir::ExprKind::Box(ref base) => {
421 self.consume_expr(base);
424 hir::ExprKind::Yield(value, _) => {
425 self.consume_expr(value);
430 fn walk_stmt(&mut self, stmt: &hir::Stmt<'_>) {
432 hir::StmtKind::Local(hir::Local { pat, init: Some(expr), .. }) => {
433 self.walk_local(expr, pat, |_| {});
436 hir::StmtKind::Local(_) => {}
438 hir::StmtKind::Item(_) => {
439 // We don't visit nested items in this visitor,
440 // only the fn body we were given.
443 hir::StmtKind::Expr(ref expr) | hir::StmtKind::Semi(ref expr) => {
444 self.consume_expr(expr);
449 fn walk_local<F>(&mut self, expr: &hir::Expr<'_>, pat: &hir::Pat<'_>, mut f: F)
453 self.walk_expr(expr);
454 let expr_place = return_if_err!(self.mc.cat_expr(expr));
456 self.walk_irrefutable_pat(&expr_place, &pat);
459 /// Indicates that the value of `blk` will be consumed, meaning either copied or moved
460 /// depending on its type.
461 fn walk_block(&mut self, blk: &hir::Block<'_>) {
462 debug!("walk_block(blk.hir_id={})", blk.hir_id);
464 for stmt in blk.stmts {
465 self.walk_stmt(stmt);
468 if let Some(ref tail_expr) = blk.expr {
469 self.consume_expr(tail_expr);
473 fn walk_struct_expr<'hir>(
475 fields: &[hir::ExprField<'_>],
476 opt_with: &Option<&'hir hir::Expr<'_>>,
478 // Consume the expressions supplying values for each field.
479 for field in fields {
480 self.consume_expr(field.expr);
483 let with_expr = match *opt_with {
490 let with_place = return_if_err!(self.mc.cat_expr(with_expr));
492 // Select just those fields of the `with`
493 // expression that will actually be used
494 match with_place.place.ty().kind() {
495 ty::Adt(adt, substs) if adt.is_struct() => {
496 // Consume those fields of the with expression that are needed.
497 for (f_index, with_field) in adt.non_enum_variant().fields.iter().enumerate() {
498 let is_mentioned = fields.iter().any(|f| {
499 self.tcx().field_index(f.hir_id, self.mc.typeck_results) == f_index
502 let field_place = self.mc.cat_projection(
505 with_field.ty(self.tcx(), substs),
506 ProjectionKind::Field(f_index as u32, VariantIdx::new(0)),
508 self.delegate_consume(&field_place, field_place.hir_id);
513 // the base expression should always evaluate to a
514 // struct; however, when EUV is run during typeck, it
515 // may not. This will generate an error earlier in typeck,
516 // so we can just ignore it.
517 if !self.tcx().sess.has_errors() {
518 span_bug!(with_expr.span, "with expression doesn't evaluate to a struct");
523 // walk the with expression so that complex expressions
524 // are properly handled.
525 self.walk_expr(with_expr);
528 /// Invoke the appropriate delegate calls for anything that gets
529 /// consumed or borrowed as part of the automatic adjustment
531 fn walk_adjustment(&mut self, expr: &hir::Expr<'_>) {
532 let adjustments = self.mc.typeck_results.expr_adjustments(expr);
533 let mut place_with_id = return_if_err!(self.mc.cat_expr_unadjusted(expr));
534 for adjustment in adjustments {
535 debug!("walk_adjustment expr={:?} adj={:?}", expr, adjustment);
536 match adjustment.kind {
537 adjustment::Adjust::NeverToAny | adjustment::Adjust::Pointer(_) => {
538 // Creating a closure/fn-pointer or unsizing consumes
539 // the input and stores it into the resulting rvalue.
540 self.delegate_consume(&place_with_id, place_with_id.hir_id);
543 adjustment::Adjust::Deref(None) => {}
545 // Autoderefs for overloaded Deref calls in fact reference
546 // their receiver. That is, if we have `(*x)` where `x`
547 // is of type `Rc<T>`, then this in fact is equivalent to
548 // `x.deref()`. Since `deref()` is declared with `&self`,
549 // this is an autoref of `x`.
550 adjustment::Adjust::Deref(Some(ref deref)) => {
551 let bk = ty::BorrowKind::from_mutbl(deref.mutbl);
552 self.delegate.borrow(&place_with_id, place_with_id.hir_id, bk);
555 adjustment::Adjust::Borrow(ref autoref) => {
556 self.walk_autoref(expr, &place_with_id, autoref);
560 return_if_err!(self.mc.cat_expr_adjusted(expr, place_with_id, adjustment));
564 /// Walks the autoref `autoref` applied to the autoderef'd
565 /// `expr`. `base_place` is the mem-categorized form of `expr`
566 /// after all relevant autoderefs have occurred.
569 expr: &hir::Expr<'_>,
570 base_place: &PlaceWithHirId<'tcx>,
571 autoref: &adjustment::AutoBorrow<'tcx>,
574 "walk_autoref(expr.hir_id={} base_place={:?} autoref={:?})",
575 expr.hir_id, base_place, autoref
579 adjustment::AutoBorrow::Ref(_, m) => {
580 self.delegate.borrow(
583 ty::BorrowKind::from_mutbl(m.into()),
587 adjustment::AutoBorrow::RawPtr(m) => {
588 debug!("walk_autoref: expr.hir_id={} base_place={:?}", expr.hir_id, base_place);
590 self.delegate.borrow(base_place, base_place.hir_id, ty::BorrowKind::from_mutbl(m));
595 fn walk_arm(&mut self, discr_place: &PlaceWithHirId<'tcx>, arm: &hir::Arm<'_>) {
596 let closure_def_id = match discr_place.place.base {
597 PlaceBase::Upvar(upvar_id) => Some(upvar_id.closure_expr_id.to_def_id()),
601 self.delegate.fake_read(
602 discr_place.place.clone(),
603 FakeReadCause::ForMatchedPlace(closure_def_id),
606 self.walk_pat(discr_place, arm.pat);
608 if let Some(hir::Guard::If(e)) = arm.guard {
610 } else if let Some(hir::Guard::IfLet(_, ref e)) = arm.guard {
614 self.consume_expr(arm.body);
617 /// Walks a pat that occurs in isolation (i.e., top-level of fn argument or
618 /// let binding, and *not* a match arm or nested pat.)
619 fn walk_irrefutable_pat(&mut self, discr_place: &PlaceWithHirId<'tcx>, pat: &hir::Pat<'_>) {
620 let closure_def_id = match discr_place.place.base {
621 PlaceBase::Upvar(upvar_id) => Some(upvar_id.closure_expr_id.to_def_id()),
625 self.delegate.fake_read(
626 discr_place.place.clone(),
627 FakeReadCause::ForLet(closure_def_id),
630 self.walk_pat(discr_place, pat);
633 /// The core driver for walking a pattern
634 fn walk_pat(&mut self, discr_place: &PlaceWithHirId<'tcx>, pat: &hir::Pat<'_>) {
635 debug!("walk_pat(discr_place={:?}, pat={:?})", discr_place, pat);
637 let tcx = self.tcx();
638 let ExprUseVisitor { ref mc, body_owner: _, ref mut delegate } = *self;
639 return_if_err!(mc.cat_pattern(discr_place.clone(), pat, |place, pat| {
640 if let PatKind::Binding(_, canonical_id, ..) = pat.kind {
641 debug!("walk_pat: binding place={:?} pat={:?}", place, pat,);
643 mc.typeck_results.extract_binding_mode(tcx.sess, pat.hir_id, pat.span)
645 debug!("walk_pat: pat.hir_id={:?} bm={:?}", pat.hir_id, bm);
647 // pat_ty: the type of the binding being produced.
648 let pat_ty = return_if_err!(mc.node_ty(pat.hir_id));
649 debug!("walk_pat: pat_ty={:?}", pat_ty);
651 // Each match binding is effectively an assignment to the
652 // binding being produced.
653 let def = Res::Local(canonical_id);
654 if let Ok(ref binding_place) = mc.cat_res(pat.hir_id, pat.span, pat_ty, def) {
655 delegate.mutate(binding_place, binding_place.hir_id);
658 // It is also a borrow or copy/move of the value being matched.
659 // In a cases of pattern like `let pat = upvar`, don't use the span
660 // of the pattern, as this just looks confusing, instead use the span
661 // of the discriminant.
663 ty::BindByReference(m) => {
664 let bk = ty::BorrowKind::from_mutbl(m);
665 delegate.borrow(place, discr_place.hir_id, bk);
667 ty::BindByValue(..) => {
668 debug!("walk_pat binding consuming pat");
669 delegate_consume(mc, *delegate, place, discr_place.hir_id);
677 /// Handle the case where the current body contains a closure.
679 /// When the current body being handled is a closure, then we must make sure that
680 /// - The parent closure only captures Places from the nested closure that are not local to it.
682 /// In the following example the closures `c` only captures `p.x` even though `incr`
683 /// is a capture of the nested closure
685 /// ```rust,ignore(cannot-test-this-because-pseudo-code)
689 /// let nested = || p.x += incr;
693 /// - When reporting the Place back to the Delegate, ensure that the UpvarId uses the enclosing
694 /// closure as the DefId.
695 fn walk_captures(&mut self, closure_expr: &hir::Expr<'_>) {
696 fn upvar_is_local_variable<'tcx>(
697 upvars: Option<&'tcx FxIndexMap<hir::HirId, hir::Upvar>>,
698 upvar_id: &hir::HirId,
699 body_owner_is_closure: bool,
701 upvars.map(|upvars| !upvars.contains_key(upvar_id)).unwrap_or(body_owner_is_closure)
704 debug!("walk_captures({:?})", closure_expr);
706 let tcx = self.tcx();
707 let closure_def_id = tcx.hir().local_def_id(closure_expr.hir_id).to_def_id();
708 let upvars = tcx.upvars_mentioned(self.body_owner);
710 // For purposes of this function, generator and closures are equivalent.
711 let body_owner_is_closure = matches!(
712 tcx.hir().body_owner_kind(tcx.hir().local_def_id_to_hir_id(self.body_owner)),
713 hir::BodyOwnerKind::Closure,
716 // If we have a nested closure, we want to include the fake reads present in the nested closure.
717 if let Some(fake_reads) = self.mc.typeck_results.closure_fake_reads.get(&closure_def_id) {
718 for (fake_read, cause, hir_id) in fake_reads.iter() {
719 match fake_read.base {
720 PlaceBase::Upvar(upvar_id) => {
721 if upvar_is_local_variable(
723 &upvar_id.var_path.hir_id,
724 body_owner_is_closure,
726 // The nested closure might be fake reading the current (enclosing) closure's local variables.
727 // The only places we want to fake read before creating the parent closure are the ones that
728 // are not local to it/ defined by it.
730 // ```rust,ignore(cannot-test-this-because-pseudo-code)
732 // let c = || { // fake reads: v1
734 // let e = || { // fake reads: v1, v2
740 // This check is performed when visiting the body of the outermost closure (`c`) and ensures
741 // that we don't add a fake read of v2 in c.
747 "Do not know how to get HirId out of Rvalue and StaticItem {:?}",
752 self.delegate.fake_read(fake_read.clone(), *cause, *hir_id);
756 if let Some(min_captures) = self.mc.typeck_results.closure_min_captures.get(&closure_def_id)
758 for (var_hir_id, min_list) in min_captures.iter() {
759 if upvars.map_or(body_owner_is_closure, |upvars| !upvars.contains_key(var_hir_id)) {
760 // The nested closure might be capturing the current (enclosing) closure's local variables.
761 // We check if the root variable is ever mentioned within the enclosing closure, if not
762 // then for the current body (if it's a closure) these aren't captures, we will ignore them.
765 for captured_place in min_list {
766 let place = &captured_place.place;
767 let capture_info = captured_place.info;
769 let place_base = if body_owner_is_closure {
770 // Mark the place to be captured by the enclosing closure
771 PlaceBase::Upvar(ty::UpvarId::new(*var_hir_id, self.body_owner))
773 // If the body owner isn't a closure then the variable must
774 // be a local variable
775 PlaceBase::Local(*var_hir_id)
777 let place_with_id = PlaceWithHirId::new(
778 capture_info.path_expr_id.unwrap_or(
779 capture_info.capture_kind_expr_id.unwrap_or(closure_expr.hir_id),
783 place.projections.clone(),
786 match capture_info.capture_kind {
787 ty::UpvarCapture::ByValue => {
788 self.delegate_consume(&place_with_id, place_with_id.hir_id);
790 ty::UpvarCapture::ByRef(upvar_borrow) => {
791 self.delegate.borrow(
793 place_with_id.hir_id,
804 fn copy_or_move<'a, 'tcx>(
805 mc: &mc::MemCategorizationContext<'a, 'tcx>,
806 place_with_id: &PlaceWithHirId<'tcx>,
808 if !mc.type_is_copy_modulo_regions(
809 place_with_id.place.ty(),
810 mc.tcx().hir().span(place_with_id.hir_id),
818 // - If a place is used in a `ByValue` context then move it if it's not a `Copy` type.
819 // - If the place that is a `Copy` type consider it an `ImmBorrow`.
820 fn delegate_consume<'a, 'tcx>(
821 mc: &mc::MemCategorizationContext<'a, 'tcx>,
822 delegate: &mut (dyn Delegate<'tcx> + 'a),
823 place_with_id: &PlaceWithHirId<'tcx>,
824 diag_expr_id: hir::HirId,
826 debug!("delegate_consume(place_with_id={:?})", place_with_id);
828 let mode = copy_or_move(mc, place_with_id);
831 ConsumeMode::Move => delegate.consume(place_with_id, diag_expr_id),
832 ConsumeMode::Copy => {
833 delegate.borrow(place_with_id, diag_expr_id, ty::BorrowKind::ImmBorrow)
838 fn is_multivariant_adt(ty: Ty<'_>) -> bool {
839 if let ty::Adt(def, _) = ty.kind() {
840 // Note that if a non-exhaustive SingleVariant is defined in another crate, we need
841 // to assume that more cases will be added to the variant in the future. This mean
842 // that we should handle non-exhaustive SingleVariant the same way we would handle
844 // If the variant is not local it must be defined in another crate.
845 let is_non_exhaustive = match def.adt_kind() {
846 AdtKind::Struct | AdtKind::Union => {
847 def.non_enum_variant().is_field_list_non_exhaustive()
849 AdtKind::Enum => def.is_variant_list_non_exhaustive(),
851 def.variants.len() > 1 || (!def.did.is_local() && is_non_exhaustive)