//! A different sort of visitor for walking fn bodies. Unlike the //! normal visitor, which just walks the entire body in one shot, the //! `ExprUseVisitor` determines how expressions are being used. use std::slice::from_ref; use hir::def::DefKind; use hir::Expr; // Export these here so that Clippy can use them. pub use rustc_middle::hir::place::{Place, PlaceBase, PlaceWithHirId, Projection}; use rustc_data_structures::fx::FxIndexMap; use rustc_hir as hir; use rustc_hir::def::Res; use rustc_hir::def_id::LocalDefId; use rustc_hir::PatKind; use rustc_index::vec::Idx; use rustc_infer::infer::InferCtxt; use rustc_middle::hir::place::ProjectionKind; use rustc_middle::mir::FakeReadCause; use rustc_middle::ty::{self, adjustment, AdtKind, Ty, TyCtxt}; use rustc_target::abi::VariantIdx; use ty::BorrowKind::ImmBorrow; use crate::mem_categorization as mc; /// This trait defines the callbacks you can expect to receive when /// employing the ExprUseVisitor. pub trait Delegate<'tcx> { /// The value found at `place` is moved, depending /// on `mode`. Where `diag_expr_id` is the id used for diagnostics for `place`. /// /// Use of a `Copy` type in a ByValue context is considered a use /// by `ImmBorrow` and `borrow` is called instead. This is because /// a shared borrow is the "minimum access" that would be needed /// to perform a copy. /// /// /// The parameter `diag_expr_id` indicates the HIR id that ought to be used for /// diagnostics. Around pattern matching such as `let pat = expr`, the diagnostic /// id will be the id of the expression `expr` but the place itself will have /// the id of the binding in the pattern `pat`. fn consume(&mut self, place_with_id: &PlaceWithHirId<'tcx>, diag_expr_id: hir::HirId); /// The value found at `place` is being borrowed with kind `bk`. /// `diag_expr_id` is the id used for diagnostics (see `consume` for more details). fn borrow( &mut self, place_with_id: &PlaceWithHirId<'tcx>, diag_expr_id: hir::HirId, bk: ty::BorrowKind, ); /// The value found at `place` is being copied. /// `diag_expr_id` is the id used for diagnostics (see `consume` for more details). fn copy(&mut self, place_with_id: &PlaceWithHirId<'tcx>, diag_expr_id: hir::HirId) { // In most cases, copying data from `x` is equivalent to doing `*&x`, so by default // we treat a copy of `x` as a borrow of `x`. self.borrow(place_with_id, diag_expr_id, ty::BorrowKind::ImmBorrow) } /// The path at `assignee_place` is being assigned to. /// `diag_expr_id` is the id used for diagnostics (see `consume` for more details). fn mutate(&mut self, assignee_place: &PlaceWithHirId<'tcx>, diag_expr_id: hir::HirId); /// The path at `binding_place` is a binding that is being initialized. /// /// This covers cases such as `let x = 42;` fn bind(&mut self, binding_place: &PlaceWithHirId<'tcx>, diag_expr_id: hir::HirId) { // Bindings can normally be treated as a regular assignment, so by default we // forward this to the mutate callback. self.mutate(binding_place, diag_expr_id) } /// The `place` should be a fake read because of specified `cause`. fn fake_read( &mut self, place_with_id: &PlaceWithHirId<'tcx>, cause: FakeReadCause, diag_expr_id: hir::HirId, ); } #[derive(Copy, Clone, PartialEq, Debug)] enum ConsumeMode { /// reference to x where x has a type that copies Copy, /// reference to x where x has a type that moves Move, } /// The ExprUseVisitor type /// /// This is the code that actually walks the tree. pub struct ExprUseVisitor<'a, 'tcx> { mc: mc::MemCategorizationContext<'a, 'tcx>, body_owner: LocalDefId, delegate: &'a mut dyn Delegate<'tcx>, } /// If the MC results in an error, it's because the type check /// failed (or will fail, when the error is uncovered and reported /// during writeback). In this case, we just ignore this part of the /// code. /// /// Note that this macro appears similar to try!(), but, unlike try!(), /// it does not propagate the error. macro_rules! return_if_err { ($inp: expr) => { match $inp { Ok(v) => v, Err(()) => { debug!("mc reported err"); return; } } }; } impl<'a, 'tcx> ExprUseVisitor<'a, 'tcx> { /// Creates the ExprUseVisitor, configuring it with the various options provided: /// /// - `delegate` -- who receives the callbacks /// - `param_env` --- parameter environment for trait lookups (esp. pertaining to `Copy`) /// - `typeck_results` --- typeck results for the code being analyzed pub fn new( delegate: &'a mut (dyn Delegate<'tcx> + 'a), infcx: &'a InferCtxt<'tcx>, body_owner: LocalDefId, param_env: ty::ParamEnv<'tcx>, typeck_results: &'a ty::TypeckResults<'tcx>, ) -> Self { ExprUseVisitor { mc: mc::MemCategorizationContext::new(infcx, param_env, body_owner, typeck_results), body_owner, delegate, } } #[instrument(skip(self), level = "debug")] pub fn consume_body(&mut self, body: &hir::Body<'_>) { for param in body.params { let param_ty = return_if_err!(self.mc.pat_ty_adjusted(param.pat)); debug!("consume_body: param_ty = {:?}", param_ty); let param_place = self.mc.cat_rvalue(param.hir_id, param.pat.span, param_ty); self.walk_irrefutable_pat(¶m_place, param.pat); } self.consume_expr(&body.value); } fn tcx(&self) -> TyCtxt<'tcx> { self.mc.tcx() } fn delegate_consume(&mut self, place_with_id: &PlaceWithHirId<'tcx>, diag_expr_id: hir::HirId) { delegate_consume(&self.mc, self.delegate, place_with_id, diag_expr_id) } fn consume_exprs(&mut self, exprs: &[hir::Expr<'_>]) { for expr in exprs { self.consume_expr(expr); } } pub fn consume_expr(&mut self, expr: &hir::Expr<'_>) { debug!("consume_expr(expr={:?})", expr); let place_with_id = return_if_err!(self.mc.cat_expr(expr)); self.delegate_consume(&place_with_id, place_with_id.hir_id); self.walk_expr(expr); } fn mutate_expr(&mut self, expr: &hir::Expr<'_>) { let place_with_id = return_if_err!(self.mc.cat_expr(expr)); self.delegate.mutate(&place_with_id, place_with_id.hir_id); self.walk_expr(expr); } fn borrow_expr(&mut self, expr: &hir::Expr<'_>, bk: ty::BorrowKind) { debug!("borrow_expr(expr={:?}, bk={:?})", expr, bk); let place_with_id = return_if_err!(self.mc.cat_expr(expr)); self.delegate.borrow(&place_with_id, place_with_id.hir_id, bk); self.walk_expr(expr) } fn select_from_expr(&mut self, expr: &hir::Expr<'_>) { self.walk_expr(expr) } pub fn walk_expr(&mut self, expr: &hir::Expr<'_>) { debug!("walk_expr(expr={:?})", expr); self.walk_adjustment(expr); match expr.kind { hir::ExprKind::Path(_) => {} hir::ExprKind::Type(subexpr, _) => self.walk_expr(subexpr), hir::ExprKind::Unary(hir::UnOp::Deref, base) => { // *base self.select_from_expr(base); } hir::ExprKind::Field(base, _) => { // base.f self.select_from_expr(base); } hir::ExprKind::Index(lhs, rhs) => { // lhs[rhs] self.select_from_expr(lhs); self.consume_expr(rhs); } hir::ExprKind::Call(callee, args) => { // callee(args) self.consume_expr(callee); self.consume_exprs(args); } hir::ExprKind::MethodCall(.., receiver, args, _) => { // callee.m(args) self.consume_expr(receiver); self.consume_exprs(args); } hir::ExprKind::Struct(_, fields, ref opt_with) => { self.walk_struct_expr(fields, opt_with); } hir::ExprKind::Tup(exprs) => { self.consume_exprs(exprs); } hir::ExprKind::If(ref cond_expr, ref then_expr, ref opt_else_expr) => { self.consume_expr(cond_expr); self.consume_expr(then_expr); if let Some(ref else_expr) = *opt_else_expr { self.consume_expr(else_expr); } } hir::ExprKind::Let(hir::Let { pat, init, .. }) => { self.walk_local(init, pat, None, |t| t.borrow_expr(init, ty::ImmBorrow)) } hir::ExprKind::Match(ref discr, arms, _) => { let discr_place = return_if_err!(self.mc.cat_expr(discr)); return_if_err!(self.maybe_read_scrutinee( discr, discr_place.clone(), arms.iter().map(|arm| arm.pat), )); // treatment of the discriminant is handled while walking the arms. for arm in arms { self.walk_arm(&discr_place, arm); } } hir::ExprKind::Array(exprs) => { self.consume_exprs(exprs); } hir::ExprKind::AddrOf(_, m, ref base) => { // &base // make sure that the thing we are pointing out stays valid // for the lifetime `scope_r` of the resulting ptr: let bk = ty::BorrowKind::from_mutbl(m); self.borrow_expr(base, bk); } hir::ExprKind::InlineAsm(asm) => { for (op, _op_sp) in asm.operands { match op { hir::InlineAsmOperand::In { expr, .. } => self.consume_expr(expr), hir::InlineAsmOperand::Out { expr: Some(expr), .. } | hir::InlineAsmOperand::InOut { expr, .. } => { self.mutate_expr(expr); } hir::InlineAsmOperand::SplitInOut { in_expr, out_expr, .. } => { self.consume_expr(in_expr); if let Some(out_expr) = out_expr { self.mutate_expr(out_expr); } } hir::InlineAsmOperand::Out { expr: None, .. } | hir::InlineAsmOperand::Const { .. } | hir::InlineAsmOperand::SymFn { .. } | hir::InlineAsmOperand::SymStatic { .. } => {} } } } hir::ExprKind::Continue(..) | hir::ExprKind::Lit(..) | hir::ExprKind::ConstBlock(..) | hir::ExprKind::Err(_) => {} hir::ExprKind::Loop(blk, ..) => { self.walk_block(blk); } hir::ExprKind::Unary(_, lhs) => { self.consume_expr(lhs); } hir::ExprKind::Binary(_, lhs, rhs) => { self.consume_expr(lhs); self.consume_expr(rhs); } hir::ExprKind::Block(blk, _) => { self.walk_block(blk); } hir::ExprKind::Break(_, ref opt_expr) | hir::ExprKind::Ret(ref opt_expr) => { if let Some(expr) = *opt_expr { self.consume_expr(expr); } } hir::ExprKind::Assign(lhs, rhs, _) => { self.mutate_expr(lhs); self.consume_expr(rhs); } hir::ExprKind::Cast(base, _) => { self.consume_expr(base); } hir::ExprKind::DropTemps(expr) => { self.consume_expr(expr); } hir::ExprKind::AssignOp(_, lhs, rhs) => { if self.mc.typeck_results.is_method_call(expr) { self.consume_expr(lhs); } else { self.mutate_expr(lhs); } self.consume_expr(rhs); } hir::ExprKind::Repeat(base, _) => { self.consume_expr(base); } hir::ExprKind::Closure(closure) => { self.walk_captures(closure); } hir::ExprKind::Box(ref base) => { self.consume_expr(base); } hir::ExprKind::Yield(value, _) => { self.consume_expr(value); } } } fn walk_stmt(&mut self, stmt: &hir::Stmt<'_>) { match stmt.kind { hir::StmtKind::Local(hir::Local { pat, init: Some(expr), els, .. }) => { self.walk_local(expr, pat, *els, |_| {}) } hir::StmtKind::Local(_) => {} hir::StmtKind::Item(_) => { // We don't visit nested items in this visitor, // only the fn body we were given. } hir::StmtKind::Expr(ref expr) | hir::StmtKind::Semi(ref expr) => { self.consume_expr(expr); } } } fn maybe_read_scrutinee<'t>( &mut self, discr: &Expr<'_>, discr_place: PlaceWithHirId<'tcx>, pats: impl Iterator>, ) -> Result<(), ()> { // Matching should not always be considered a use of the place, hence // discr does not necessarily need to be borrowed. // We only want to borrow discr if the pattern contain something other // than wildcards. let ExprUseVisitor { ref mc, body_owner: _, delegate: _ } = *self; let mut needs_to_be_read = false; for pat in pats { mc.cat_pattern(discr_place.clone(), pat, |place, pat| { match &pat.kind { PatKind::Binding(.., opt_sub_pat) => { // If the opt_sub_pat is None, than the binding does not count as // a wildcard for the purpose of borrowing discr. if opt_sub_pat.is_none() { needs_to_be_read = true; } } PatKind::Path(qpath) => { // A `Path` pattern is just a name like `Foo`. This is either a // named constant or else it refers to an ADT variant let res = self.mc.typeck_results.qpath_res(qpath, pat.hir_id); match res { Res::Def(DefKind::Const, _) | Res::Def(DefKind::AssocConst, _) => { // Named constants have to be equated with the value // being matched, so that's a read of the value being matched. // // FIXME: We don't actually reads for ZSTs. needs_to_be_read = true; } _ => { // Otherwise, this is a struct/enum variant, and so it's // only a read if we need to read the discriminant. needs_to_be_read |= is_multivariant_adt(place.place.ty()); } } } PatKind::TupleStruct(..) | PatKind::Struct(..) | PatKind::Tuple(..) => { // For `Foo(..)`, `Foo { ... }` and `(...)` patterns, check if we are matching // against a multivariant enum or struct. In that case, we have to read // the discriminant. Otherwise this kind of pattern doesn't actually // read anything (we'll get invoked for the `...`, which may indeed // perform some reads). let place_ty = place.place.ty(); needs_to_be_read |= is_multivariant_adt(place_ty); } PatKind::Lit(_) | PatKind::Range(..) => { // If the PatKind is a Lit or a Range then we want // to borrow discr. needs_to_be_read = true; } PatKind::Or(_) | PatKind::Box(_) | PatKind::Slice(..) | PatKind::Ref(..) | PatKind::Wild => { // If the PatKind is Or, Box, Slice or Ref, the decision is made later // as these patterns contains subpatterns // If the PatKind is Wild, the decision is made based on the other patterns being // examined } } })? } if needs_to_be_read { self.borrow_expr(discr, ty::ImmBorrow); } else { let closure_def_id = match discr_place.place.base { PlaceBase::Upvar(upvar_id) => Some(upvar_id.closure_expr_id), _ => None, }; self.delegate.fake_read( &discr_place, FakeReadCause::ForMatchedPlace(closure_def_id), discr_place.hir_id, ); // We always want to walk the discriminant. We want to make sure, for instance, // that the discriminant has been initialized. self.walk_expr(discr); } Ok(()) } fn walk_local( &mut self, expr: &hir::Expr<'_>, pat: &hir::Pat<'_>, els: Option<&hir::Block<'_>>, mut f: F, ) where F: FnMut(&mut Self), { self.walk_expr(expr); let expr_place = return_if_err!(self.mc.cat_expr(expr)); f(self); if let Some(els) = els { // borrowing because we need to test the discriminant return_if_err!(self.maybe_read_scrutinee( expr, expr_place.clone(), from_ref(pat).iter() )); self.walk_block(els) } self.walk_irrefutable_pat(&expr_place, &pat); } /// Indicates that the value of `blk` will be consumed, meaning either copied or moved /// depending on its type. fn walk_block(&mut self, blk: &hir::Block<'_>) { debug!("walk_block(blk.hir_id={})", blk.hir_id); for stmt in blk.stmts { self.walk_stmt(stmt); } if let Some(ref tail_expr) = blk.expr { self.consume_expr(tail_expr); } } fn walk_struct_expr<'hir>( &mut self, fields: &[hir::ExprField<'_>], opt_with: &Option<&'hir hir::Expr<'_>>, ) { // Consume the expressions supplying values for each field. for field in fields { self.consume_expr(field.expr); // The struct path probably didn't resolve if self.mc.typeck_results.opt_field_index(field.hir_id).is_none() { self.tcx().sess.delay_span_bug(field.span, "couldn't resolve index for field"); } } let with_expr = match *opt_with { Some(w) => &*w, None => { return; } }; let with_place = return_if_err!(self.mc.cat_expr(with_expr)); // Select just those fields of the `with` // expression that will actually be used match with_place.place.ty().kind() { ty::Adt(adt, substs) if adt.is_struct() => { // Consume those fields of the with expression that are needed. for (f_index, with_field) in adt.non_enum_variant().fields.iter().enumerate() { let is_mentioned = fields .iter() .any(|f| self.mc.typeck_results.opt_field_index(f.hir_id) == Some(f_index)); if !is_mentioned { let field_place = self.mc.cat_projection( &*with_expr, with_place.clone(), with_field.ty(self.tcx(), substs), ProjectionKind::Field(f_index as u32, VariantIdx::new(0)), ); self.delegate_consume(&field_place, field_place.hir_id); } } } _ => { // the base expression should always evaluate to a // struct; however, when EUV is run during typeck, it // may not. This will generate an error earlier in typeck, // so we can just ignore it. if !self.tcx().sess.has_errors().is_some() { span_bug!(with_expr.span, "with expression doesn't evaluate to a struct"); } } } // walk the with expression so that complex expressions // are properly handled. self.walk_expr(with_expr); } /// Invoke the appropriate delegate calls for anything that gets /// consumed or borrowed as part of the automatic adjustment /// process. fn walk_adjustment(&mut self, expr: &hir::Expr<'_>) { let adjustments = self.mc.typeck_results.expr_adjustments(expr); let mut place_with_id = return_if_err!(self.mc.cat_expr_unadjusted(expr)); for adjustment in adjustments { debug!("walk_adjustment expr={:?} adj={:?}", expr, adjustment); match adjustment.kind { adjustment::Adjust::NeverToAny | adjustment::Adjust::Pointer(_) | adjustment::Adjust::DynStar => { // Creating a closure/fn-pointer or unsizing consumes // the input and stores it into the resulting rvalue. self.delegate_consume(&place_with_id, place_with_id.hir_id); } adjustment::Adjust::Deref(None) => {} // Autoderefs for overloaded Deref calls in fact reference // their receiver. That is, if we have `(*x)` where `x` // is of type `Rc`, then this in fact is equivalent to // `x.deref()`. Since `deref()` is declared with `&self`, // this is an autoref of `x`. adjustment::Adjust::Deref(Some(ref deref)) => { let bk = ty::BorrowKind::from_mutbl(deref.mutbl); self.delegate.borrow(&place_with_id, place_with_id.hir_id, bk); } adjustment::Adjust::Borrow(ref autoref) => { self.walk_autoref(expr, &place_with_id, autoref); } } place_with_id = return_if_err!(self.mc.cat_expr_adjusted(expr, place_with_id, adjustment)); } } /// Walks the autoref `autoref` applied to the autoderef'd /// `expr`. `base_place` is the mem-categorized form of `expr` /// after all relevant autoderefs have occurred. fn walk_autoref( &mut self, expr: &hir::Expr<'_>, base_place: &PlaceWithHirId<'tcx>, autoref: &adjustment::AutoBorrow<'tcx>, ) { debug!( "walk_autoref(expr.hir_id={} base_place={:?} autoref={:?})", expr.hir_id, base_place, autoref ); match *autoref { adjustment::AutoBorrow::Ref(_, m) => { self.delegate.borrow( base_place, base_place.hir_id, ty::BorrowKind::from_mutbl(m.into()), ); } adjustment::AutoBorrow::RawPtr(m) => { debug!("walk_autoref: expr.hir_id={} base_place={:?}", expr.hir_id, base_place); self.delegate.borrow(base_place, base_place.hir_id, ty::BorrowKind::from_mutbl(m)); } } } fn walk_arm(&mut self, discr_place: &PlaceWithHirId<'tcx>, arm: &hir::Arm<'_>) { let closure_def_id = match discr_place.place.base { PlaceBase::Upvar(upvar_id) => Some(upvar_id.closure_expr_id), _ => None, }; self.delegate.fake_read( discr_place, FakeReadCause::ForMatchedPlace(closure_def_id), discr_place.hir_id, ); self.walk_pat(discr_place, arm.pat, arm.guard.is_some()); if let Some(hir::Guard::If(e)) = arm.guard { self.consume_expr(e) } else if let Some(hir::Guard::IfLet(ref l)) = arm.guard { self.consume_expr(l.init) } self.consume_expr(arm.body); } /// Walks a pat that occurs in isolation (i.e., top-level of fn argument or /// let binding, and *not* a match arm or nested pat.) fn walk_irrefutable_pat(&mut self, discr_place: &PlaceWithHirId<'tcx>, pat: &hir::Pat<'_>) { let closure_def_id = match discr_place.place.base { PlaceBase::Upvar(upvar_id) => Some(upvar_id.closure_expr_id), _ => None, }; self.delegate.fake_read( discr_place, FakeReadCause::ForLet(closure_def_id), discr_place.hir_id, ); self.walk_pat(discr_place, pat, false); } /// The core driver for walking a pattern fn walk_pat( &mut self, discr_place: &PlaceWithHirId<'tcx>, pat: &hir::Pat<'_>, has_guard: bool, ) { debug!("walk_pat(discr_place={:?}, pat={:?}, has_guard={:?})", discr_place, pat, has_guard); let tcx = self.tcx(); let ExprUseVisitor { ref mc, body_owner: _, ref mut delegate } = *self; return_if_err!(mc.cat_pattern(discr_place.clone(), pat, |place, pat| { if let PatKind::Binding(_, canonical_id, ..) = pat.kind { debug!("walk_pat: binding place={:?} pat={:?}", place, pat); if let Some(bm) = mc.typeck_results.extract_binding_mode(tcx.sess, pat.hir_id, pat.span) { debug!("walk_pat: pat.hir_id={:?} bm={:?}", pat.hir_id, bm); // pat_ty: the type of the binding being produced. let pat_ty = return_if_err!(mc.node_ty(pat.hir_id)); debug!("walk_pat: pat_ty={:?}", pat_ty); let def = Res::Local(canonical_id); if let Ok(ref binding_place) = mc.cat_res(pat.hir_id, pat.span, pat_ty, def) { delegate.bind(binding_place, binding_place.hir_id); } // Subtle: MIR desugaring introduces immutable borrows for each pattern // binding when lowering pattern guards to ensure that the guard does not // modify the scrutinee. if has_guard { delegate.borrow(place, discr_place.hir_id, ImmBorrow); } // It is also a borrow or copy/move of the value being matched. // In a cases of pattern like `let pat = upvar`, don't use the span // of the pattern, as this just looks confusing, instead use the span // of the discriminant. match bm { ty::BindByReference(m) => { let bk = ty::BorrowKind::from_mutbl(m); delegate.borrow(place, discr_place.hir_id, bk); } ty::BindByValue(..) => { debug!("walk_pat binding consuming pat"); delegate_consume(mc, *delegate, place, discr_place.hir_id); } } } } })); } /// Handle the case where the current body contains a closure. /// /// When the current body being handled is a closure, then we must make sure that /// - The parent closure only captures Places from the nested closure that are not local to it. /// /// In the following example the closures `c` only captures `p.x` even though `incr` /// is a capture of the nested closure /// /// ``` /// struct P { x: i32 } /// let mut p = P { x: 4 }; /// let c = || { /// let incr = 10; /// let nested = || p.x += incr; /// }; /// ``` /// /// - When reporting the Place back to the Delegate, ensure that the UpvarId uses the enclosing /// closure as the DefId. fn walk_captures(&mut self, closure_expr: &hir::Closure<'_>) { fn upvar_is_local_variable( upvars: Option<&FxIndexMap>, upvar_id: hir::HirId, body_owner_is_closure: bool, ) -> bool { upvars.map(|upvars| !upvars.contains_key(&upvar_id)).unwrap_or(body_owner_is_closure) } debug!("walk_captures({:?})", closure_expr); let tcx = self.tcx(); let closure_def_id = closure_expr.def_id; let upvars = tcx.upvars_mentioned(self.body_owner); // For purposes of this function, generator and closures are equivalent. let body_owner_is_closure = matches!(tcx.hir().body_owner_kind(self.body_owner), hir::BodyOwnerKind::Closure,); // If we have a nested closure, we want to include the fake reads present in the nested closure. if let Some(fake_reads) = self.mc.typeck_results.closure_fake_reads.get(&closure_def_id) { for (fake_read, cause, hir_id) in fake_reads.iter() { match fake_read.base { PlaceBase::Upvar(upvar_id) => { if upvar_is_local_variable( upvars, upvar_id.var_path.hir_id, body_owner_is_closure, ) { // The nested closure might be fake reading the current (enclosing) closure's local variables. // The only places we want to fake read before creating the parent closure are the ones that // are not local to it/ defined by it. // // ```rust,ignore(cannot-test-this-because-pseudo-code) // let v1 = (0, 1); // let c = || { // fake reads: v1 // let v2 = (0, 1); // let e = || { // fake reads: v1, v2 // let (_, t1) = v1; // let (_, t2) = v2; // } // } // ``` // This check is performed when visiting the body of the outermost closure (`c`) and ensures // that we don't add a fake read of v2 in c. continue; } } _ => { bug!( "Do not know how to get HirId out of Rvalue and StaticItem {:?}", fake_read.base ); } }; self.delegate.fake_read( &PlaceWithHirId { place: fake_read.clone(), hir_id: *hir_id }, *cause, *hir_id, ); } } if let Some(min_captures) = self.mc.typeck_results.closure_min_captures.get(&closure_def_id) { for (var_hir_id, min_list) in min_captures.iter() { if upvars.map_or(body_owner_is_closure, |upvars| !upvars.contains_key(var_hir_id)) { // The nested closure might be capturing the current (enclosing) closure's local variables. // We check if the root variable is ever mentioned within the enclosing closure, if not // then for the current body (if it's a closure) these aren't captures, we will ignore them. continue; } for captured_place in min_list { let place = &captured_place.place; let capture_info = captured_place.info; let place_base = if body_owner_is_closure { // Mark the place to be captured by the enclosing closure PlaceBase::Upvar(ty::UpvarId::new(*var_hir_id, self.body_owner)) } else { // If the body owner isn't a closure then the variable must // be a local variable PlaceBase::Local(*var_hir_id) }; let closure_hir_id = tcx.hir().local_def_id_to_hir_id(closure_def_id); let place_with_id = PlaceWithHirId::new( capture_info .path_expr_id .unwrap_or(capture_info.capture_kind_expr_id.unwrap_or(closure_hir_id)), place.base_ty, place_base, place.projections.clone(), ); match capture_info.capture_kind { ty::UpvarCapture::ByValue => { self.delegate_consume(&place_with_id, place_with_id.hir_id); } ty::UpvarCapture::ByRef(upvar_borrow) => { self.delegate.borrow( &place_with_id, place_with_id.hir_id, upvar_borrow, ); } } } } } } } fn copy_or_move<'a, 'tcx>( mc: &mc::MemCategorizationContext<'a, 'tcx>, place_with_id: &PlaceWithHirId<'tcx>, ) -> ConsumeMode { if !mc.type_is_copy_modulo_regions( place_with_id.place.ty(), mc.tcx().hir().span(place_with_id.hir_id), ) { ConsumeMode::Move } else { ConsumeMode::Copy } } // - If a place is used in a `ByValue` context then move it if it's not a `Copy` type. // - If the place that is a `Copy` type consider it an `ImmBorrow`. fn delegate_consume<'a, 'tcx>( mc: &mc::MemCategorizationContext<'a, 'tcx>, delegate: &mut (dyn Delegate<'tcx> + 'a), place_with_id: &PlaceWithHirId<'tcx>, diag_expr_id: hir::HirId, ) { debug!("delegate_consume(place_with_id={:?})", place_with_id); let mode = copy_or_move(mc, place_with_id); match mode { ConsumeMode::Move => delegate.consume(place_with_id, diag_expr_id), ConsumeMode::Copy => delegate.copy(place_with_id, diag_expr_id), } } fn is_multivariant_adt(ty: Ty<'_>) -> bool { if let ty::Adt(def, _) = ty.kind() { // Note that if a non-exhaustive SingleVariant is defined in another crate, we need // to assume that more cases will be added to the variant in the future. This mean // that we should handle non-exhaustive SingleVariant the same way we would handle // a MultiVariant. // If the variant is not local it must be defined in another crate. let is_non_exhaustive = match def.adt_kind() { AdtKind::Struct | AdtKind::Union => { def.non_enum_variant().is_field_list_non_exhaustive() } AdtKind::Enum => def.is_variant_list_non_exhaustive(), }; def.variants().len() > 1 || (!def.did().is_local() && is_non_exhaustive) } else { false } }