| //! 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_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::FIRST_VARIANT; |
| 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::OffsetOf(..) |
| | 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::Become(call) => { |
| self.consume_expr(call); |
| } |
| |
| 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::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<Item = &'t hir::Pat<'t>>, |
| ) -> 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::Slice(lhs, wild, rhs) => { |
| // We don't need to test the length if the pattern is `[..]` |
| if matches!((lhs, wild, rhs), (&[], Some(_), &[])) |
| // Arrays have a statically known size, so |
| // there is no need to read their length |
| || place.place.ty().peel_refs().is_array() |
| { |
| } else { |
| needs_to_be_read = true; |
| } |
| } |
| PatKind::Or(_) | PatKind::Box(_) | PatKind::Ref(..) | PatKind::Wild => { |
| // If the PatKind is Or, Box, 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<F>( |
| &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, args) 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_enumerated() { |
| 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(), args), |
| ProjectionKind::Field(f_index, FIRST_VARIANT), |
| ); |
| 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_none() { |
| 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<T>`, 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()); |
| |
| match arm.guard { |
| Some(hir::Guard::If(ref e)) => self.consume_expr(e), |
| Some(hir::Guard::IfLet(ref l)) => { |
| self.walk_local(l.init, l.pat, None, |t| t.borrow_expr(l.init, ty::ImmBorrow)) |
| } |
| None => {} |
| } |
| |
| 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<hir::HirId, hir::Upvar>>, |
| 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, coroutine 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()) { |
| 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 |
| } |
| } |
