| //! See The Book chapter on the borrow checker for more details. |
| |
| #![allow(non_camel_case_types)] |
| |
| pub use LoanPathKind::*; |
| pub use LoanPathElem::*; |
| |
| use InteriorKind::*; |
| |
| use rustc::hir::HirId; |
| use rustc::hir::Node; |
| use rustc::cfg; |
| use rustc::middle::borrowck::{BorrowCheckResult, SignalledError}; |
| use rustc::hir::def_id::{DefId, LocalDefId}; |
| use rustc::middle::mem_categorization as mc; |
| use rustc::middle::mem_categorization::Categorization; |
| use rustc::middle::region; |
| use rustc::middle::free_region::RegionRelations; |
| use rustc::ty::{self, Ty, TyCtxt}; |
| use rustc::ty::query::Providers; |
| |
| use std::borrow::Cow; |
| use std::cell::{Cell}; |
| use std::fmt; |
| use std::rc::Rc; |
| use std::hash::{Hash, Hasher}; |
| use log::debug; |
| |
| use rustc::hir; |
| |
| use crate::dataflow::{DataFlowContext, BitwiseOperator, DataFlowOperator, KillFrom}; |
| |
| pub mod check_loans; |
| |
| pub mod gather_loans; |
| |
| pub mod move_data; |
| |
| #[derive(Clone, Copy)] |
| pub struct LoanDataFlowOperator; |
| |
| pub type LoanDataFlow<'tcx> = DataFlowContext<'tcx, LoanDataFlowOperator>; |
| |
| pub fn check_crate(tcx: TyCtxt<'_>) { |
| tcx.par_body_owners(|body_owner_def_id| { |
| tcx.ensure().borrowck(body_owner_def_id); |
| }); |
| } |
| |
| pub fn provide(providers: &mut Providers<'_>) { |
| *providers = Providers { |
| borrowck, |
| ..*providers |
| }; |
| } |
| |
| /// Collection of conclusions determined via borrow checker analyses. |
| pub struct AnalysisData<'tcx> { |
| pub all_loans: Vec<Loan<'tcx>>, |
| pub loans: DataFlowContext<'tcx, LoanDataFlowOperator>, |
| pub move_data: move_data::FlowedMoveData<'tcx>, |
| } |
| |
| fn borrowck(tcx: TyCtxt<'_>, owner_def_id: DefId) -> &BorrowCheckResult { |
| assert!(tcx.use_ast_borrowck() || tcx.migrate_borrowck()); |
| |
| debug!("borrowck(body_owner_def_id={:?})", owner_def_id); |
| |
| let signalled_error = tcx.check_match(owner_def_id); |
| if let SignalledError::SawSomeError = signalled_error { |
| return tcx.arena.alloc(BorrowCheckResult { |
| signalled_any_error: SignalledError::SawSomeError, |
| }) |
| } |
| |
| let owner_id = tcx.hir().as_local_hir_id(owner_def_id).unwrap(); |
| |
| match tcx.hir().get(owner_id) { |
| Node::Ctor(..) => { |
| // We get invoked with anything that has MIR, but some of |
| // those things (notably the synthesized constructors from |
| // tuple structs/variants) do not have an associated body |
| // and do not need borrowchecking. |
| return tcx.arena.alloc(BorrowCheckResult { |
| signalled_any_error: SignalledError::NoErrorsSeen, |
| }) |
| } |
| _ => { } |
| } |
| |
| let body_id = tcx.hir().body_owned_by(owner_id); |
| let tables = tcx.typeck_tables_of(owner_def_id); |
| let region_scope_tree = tcx.region_scope_tree(owner_def_id); |
| let body = tcx.hir().body(body_id); |
| let mut bccx = BorrowckCtxt { |
| tcx, |
| tables, |
| region_scope_tree, |
| owner_def_id, |
| body, |
| signalled_any_error: Cell::new(SignalledError::NoErrorsSeen), |
| }; |
| |
| // Eventually, borrowck will always read the MIR, but at the |
| // moment we do not. So, for now, we always force MIR to be |
| // constructed for a given fn, since this may result in errors |
| // being reported and we want that to happen. |
| // |
| // Note that `mir_validated` is a "stealable" result; the |
| // thief, `optimized_mir()`, forces borrowck, so we know that |
| // is not yet stolen. |
| tcx.ensure().mir_validated(owner_def_id); |
| |
| // option dance because you can't capture an uninitialized variable |
| // by mut-ref. |
| let mut cfg = None; |
| if let Some(AnalysisData { all_loans, |
| loans: loan_dfcx, |
| move_data: flowed_moves }) = |
| build_borrowck_dataflow_data(&mut bccx, false, body_id, |
| |bccx| { |
| cfg = Some(cfg::CFG::new(bccx.tcx, &body)); |
| cfg.as_mut().unwrap() |
| }) |
| { |
| check_loans::check_loans(&mut bccx, &loan_dfcx, &flowed_moves, &all_loans, body); |
| } |
| |
| tcx.arena.alloc(BorrowCheckResult { |
| signalled_any_error: bccx.signalled_any_error.into_inner(), |
| }) |
| } |
| |
| fn build_borrowck_dataflow_data<'a, 'c, 'tcx, F>(this: &mut BorrowckCtxt<'a, 'tcx>, |
| force_analysis: bool, |
| body_id: hir::BodyId, |
| get_cfg: F) |
| -> Option<AnalysisData<'tcx>> |
| where F: FnOnce(&mut BorrowckCtxt<'a, 'tcx>) -> &'c cfg::CFG |
| { |
| // Check the body of fn items. |
| let (all_loans, move_data) = |
| gather_loans::gather_loans_in_fn(this, body_id); |
| |
| if !force_analysis && move_data.is_empty() && all_loans.is_empty() { |
| // large arrays of data inserted as constants can take a lot of |
| // time and memory to borrow-check - see issue #36799. However, |
| // they don't have places, so no borrow-check is actually needed. |
| // Recognize that case and skip borrow-checking. |
| debug!("skipping loan propagation for {:?} because of no loans", body_id); |
| return None; |
| } else { |
| debug!("propagating loans in {:?}", body_id); |
| } |
| |
| let cfg = get_cfg(this); |
| let mut loan_dfcx = |
| DataFlowContext::new(this.tcx, |
| "borrowck", |
| Some(this.body), |
| cfg, |
| LoanDataFlowOperator, |
| all_loans.len()); |
| for (loan_idx, loan) in all_loans.iter().enumerate() { |
| loan_dfcx.add_gen(loan.gen_scope.item_local_id(), loan_idx); |
| loan_dfcx.add_kill(KillFrom::ScopeEnd, |
| loan.kill_scope.item_local_id(), |
| loan_idx); |
| } |
| loan_dfcx.add_kills_from_flow_exits(cfg); |
| loan_dfcx.propagate(cfg, this.body); |
| |
| let flowed_moves = move_data::FlowedMoveData::new(move_data, |
| this, |
| cfg, |
| this.body); |
| |
| Some(AnalysisData { all_loans, |
| loans: loan_dfcx, |
| move_data:flowed_moves }) |
| } |
| |
| /// Accessor for introspective clients inspecting `AnalysisData` and |
| /// the `BorrowckCtxt` itself , e.g., the flowgraph visualizer. |
| pub fn build_borrowck_dataflow_data_for_fn<'a, 'tcx>( |
| tcx: TyCtxt<'tcx>, |
| body_id: hir::BodyId, |
| cfg: &cfg::CFG) |
| -> (BorrowckCtxt<'a, 'tcx>, AnalysisData<'tcx>) |
| { |
| let owner_id = tcx.hir().body_owner(body_id); |
| let owner_def_id = tcx.hir().local_def_id(owner_id); |
| let tables = tcx.typeck_tables_of(owner_def_id); |
| let region_scope_tree = tcx.region_scope_tree(owner_def_id); |
| let body = tcx.hir().body(body_id); |
| let mut bccx = BorrowckCtxt { |
| tcx, |
| tables, |
| region_scope_tree, |
| owner_def_id, |
| body, |
| signalled_any_error: Cell::new(SignalledError::NoErrorsSeen), |
| }; |
| |
| let dataflow_data = build_borrowck_dataflow_data(&mut bccx, true, body_id, |_| cfg); |
| (bccx, dataflow_data.unwrap()) |
| } |
| |
| // ---------------------------------------------------------------------- |
| // Type definitions |
| |
| pub struct BorrowckCtxt<'a, 'tcx> { |
| tcx: TyCtxt<'tcx>, |
| |
| // tables for the current thing we are checking; set to |
| // Some in `borrowck_fn` and cleared later |
| tables: &'a ty::TypeckTables<'tcx>, |
| |
| region_scope_tree: &'tcx region::ScopeTree, |
| |
| owner_def_id: DefId, |
| |
| body: &'tcx hir::Body, |
| |
| signalled_any_error: Cell<SignalledError>, |
| } |
| |
| |
| impl<'a, 'tcx: 'a> BorrowckCtxt<'a, 'tcx> { |
| fn signal_error(&self) { |
| self.signalled_any_error.set(SignalledError::SawSomeError); |
| } |
| } |
| |
| /////////////////////////////////////////////////////////////////////////// |
| // Loans and loan paths |
| |
| /// Record of a loan that was issued. |
| pub struct Loan<'tcx> { |
| index: usize, |
| loan_path: Rc<LoanPath<'tcx>>, |
| kind: ty::BorrowKind, |
| restricted_paths: Vec<Rc<LoanPath<'tcx>>>, |
| |
| /// gen_scope indicates where loan is introduced. Typically the |
| /// loan is introduced at the point of the borrow, but in some |
| /// cases, notably method arguments, the loan may be introduced |
| /// only later, once it comes into scope. See also |
| /// `GatherLoanCtxt::compute_gen_scope`. |
| gen_scope: region::Scope, |
| |
| /// kill_scope indicates when the loan goes out of scope. This is |
| /// either when the lifetime expires or when the local variable |
| /// which roots the loan-path goes out of scope, whichever happens |
| /// faster. See also `GatherLoanCtxt::compute_kill_scope`. |
| kill_scope: region::Scope, |
| } |
| |
| impl<'tcx> Loan<'tcx> { |
| pub fn loan_path(&self) -> Rc<LoanPath<'tcx>> { |
| self.loan_path.clone() |
| } |
| } |
| |
| #[derive(Eq)] |
| pub struct LoanPath<'tcx> { |
| kind: LoanPathKind<'tcx>, |
| ty: Ty<'tcx>, |
| } |
| |
| impl<'tcx> PartialEq for LoanPath<'tcx> { |
| fn eq(&self, that: &LoanPath<'tcx>) -> bool { |
| self.kind == that.kind |
| } |
| } |
| |
| impl<'tcx> Hash for LoanPath<'tcx> { |
| fn hash<H: Hasher>(&self, state: &mut H) { |
| self.kind.hash(state); |
| } |
| } |
| |
| #[derive(PartialEq, Eq, Hash, Debug)] |
| pub enum LoanPathKind<'tcx> { |
| LpVar(hir::HirId), // `x` in README.md |
| LpUpvar(ty::UpvarId), // `x` captured by-value into closure |
| LpDowncast(Rc<LoanPath<'tcx>>, DefId), // `x` downcast to particular enum variant |
| LpExtend(Rc<LoanPath<'tcx>>, mc::MutabilityCategory, LoanPathElem<'tcx>) |
| } |
| |
| impl<'tcx> LoanPath<'tcx> { |
| fn new(kind: LoanPathKind<'tcx>, ty: Ty<'tcx>) -> LoanPath<'tcx> { |
| LoanPath { kind: kind, ty: ty } |
| } |
| |
| fn to_type(&self) -> Ty<'tcx> { self.ty } |
| } |
| |
| // FIXME (pnkfelix): See discussion here |
| // https://github.com/pnkfelix/rust/commit/ |
| // b2b39e8700e37ad32b486b9a8409b50a8a53aa51#commitcomment-7892003 |
| const DOWNCAST_PRINTED_OPERATOR: &'static str = " as "; |
| |
| // A local, "cleaned" version of `mc::InteriorKind` that drops |
| // information that is not relevant to loan-path analysis. (In |
| // particular, the distinction between how precisely an array-element |
| // is tracked is irrelevant here.) |
| #[derive(Clone, Copy, PartialEq, Eq, Hash)] |
| pub enum InteriorKind { |
| InteriorField(mc::FieldIndex), |
| InteriorElement, |
| } |
| |
| trait ToInteriorKind { fn cleaned(self) -> InteriorKind; } |
| impl ToInteriorKind for mc::InteriorKind { |
| fn cleaned(self) -> InteriorKind { |
| match self { |
| mc::InteriorField(name) => InteriorField(name), |
| mc::InteriorElement(_) => InteriorElement, |
| } |
| } |
| } |
| |
| // This can be: |
| // - a pointer dereference (`*P` in README.md) |
| // - a field reference, with an optional definition of the containing |
| // enum variant (`P.f` in README.md) |
| // `DefId` is present when the field is part of struct that is in |
| // a variant of an enum. For instance in: |
| // `enum E { X { foo: u32 }, Y { foo: u32 }}` |
| // each `foo` is qualified by the definitition id of the variant (`X` or `Y`). |
| #[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)] |
| pub enum LoanPathElem<'tcx> { |
| LpDeref(mc::PointerKind<'tcx>), |
| LpInterior(Option<DefId>, InteriorKind), |
| } |
| |
| fn closure_to_block(closure_id: LocalDefId, tcx: TyCtxt<'_>) -> HirId { |
| let closure_id = tcx.hir().local_def_id_to_hir_id(closure_id); |
| match tcx.hir().get(closure_id) { |
| Node::Expr(expr) => match expr.node { |
| hir::ExprKind::Closure(.., body_id, _, _) => { |
| body_id.hir_id |
| } |
| _ => { |
| bug!("encountered non-closure id: {}", closure_id) |
| } |
| }, |
| _ => bug!("encountered non-expr id: {}", closure_id) |
| } |
| } |
| |
| impl<'a, 'tcx> LoanPath<'tcx> { |
| pub fn kill_scope(&self, bccx: &BorrowckCtxt<'a, 'tcx>) -> region::Scope { |
| match self.kind { |
| LpVar(hir_id) => { |
| bccx.region_scope_tree.var_scope(hir_id.local_id) |
| } |
| LpUpvar(upvar_id) => { |
| let block_id = closure_to_block(upvar_id.closure_expr_id, bccx.tcx); |
| region::Scope { id: block_id.local_id, data: region::ScopeData::Node } |
| } |
| LpDowncast(ref base, _) | |
| LpExtend(ref base, ..) => base.kill_scope(bccx), |
| } |
| } |
| } |
| |
| // Avoid "cannot borrow immutable field `self.x` as mutable" as that implies that a field *can* be |
| // mutable independently of the struct it belongs to. (#35937) |
| pub fn opt_loan_path_is_field<'tcx>(cmt: &mc::cmt_<'tcx>) -> (Option<Rc<LoanPath<'tcx>>>, bool) { |
| let new_lp = |v: LoanPathKind<'tcx>| Rc::new(LoanPath::new(v, cmt.ty)); |
| |
| match cmt.cat { |
| Categorization::Rvalue(..) | |
| Categorization::ThreadLocal(..) | |
| Categorization::StaticItem => { |
| (None, false) |
| } |
| |
| Categorization::Local(id) => { |
| (Some(new_lp(LpVar(id))), false) |
| } |
| |
| Categorization::Upvar(mc::Upvar { id, .. }) => { |
| (Some(new_lp(LpUpvar(id))), false) |
| } |
| |
| Categorization::Deref(ref cmt_base, pk) => { |
| let lp = opt_loan_path_is_field(cmt_base); |
| (lp.0.map(|lp| { |
| new_lp(LpExtend(lp, cmt.mutbl, LpDeref(pk))) |
| }), lp.1) |
| } |
| |
| Categorization::Interior(ref cmt_base, ik) => { |
| (opt_loan_path(cmt_base).map(|lp| { |
| let opt_variant_id = match cmt_base.cat { |
| Categorization::Downcast(_, did) => Some(did), |
| _ => None |
| }; |
| new_lp(LpExtend(lp, cmt.mutbl, LpInterior(opt_variant_id, ik.cleaned()))) |
| }), true) |
| } |
| |
| Categorization::Downcast(ref cmt_base, variant_def_id) => { |
| let lp = opt_loan_path_is_field(cmt_base); |
| (lp.0.map(|lp| { |
| new_lp(LpDowncast(lp, variant_def_id)) |
| }), lp.1) |
| } |
| } |
| } |
| |
| /// Computes the `LoanPath` (if any) for a `cmt`. |
| /// Note that this logic is somewhat duplicated in |
| /// the method `compute()` found in `gather_loans::restrictions`, |
| /// which allows it to share common loan path pieces as it |
| /// traverses the CMT. |
| pub fn opt_loan_path<'tcx>(cmt: &mc::cmt_<'tcx>) -> Option<Rc<LoanPath<'tcx>>> { |
| opt_loan_path_is_field(cmt).0 |
| } |
| |
| /////////////////////////////////////////////////////////////////////////// |
| // Misc |
| |
| impl<'a, 'tcx> BorrowckCtxt<'a, 'tcx> { |
| pub fn is_subregion_of(&self, |
| r_sub: ty::Region<'tcx>, |
| r_sup: ty::Region<'tcx>) |
| -> bool |
| { |
| let region_rels = RegionRelations::new(self.tcx, |
| self.owner_def_id, |
| &self.region_scope_tree, |
| &self.tables.free_region_map); |
| region_rels.is_subregion_of(r_sub, r_sup) |
| } |
| |
| pub fn append_loan_path_to_string(&self, |
| loan_path: &LoanPath<'tcx>, |
| out: &mut String) { |
| match loan_path.kind { |
| LpUpvar(ty::UpvarId { var_path: ty::UpvarPath { hir_id: id }, closure_expr_id: _ }) => { |
| out.push_str(&self.tcx.hir().name(id).as_str()); |
| } |
| LpVar(id) => { |
| out.push_str(&self.tcx.hir().name(id).as_str()); |
| } |
| |
| LpDowncast(ref lp_base, variant_def_id) => { |
| out.push('('); |
| self.append_loan_path_to_string(&lp_base, out); |
| out.push_str(DOWNCAST_PRINTED_OPERATOR); |
| out.push_str(&self.tcx.def_path_str(variant_def_id)); |
| out.push(')'); |
| } |
| |
| LpExtend(ref lp_base, _, LpInterior(_, InteriorField(mc::FieldIndex(_, info)))) => { |
| self.append_autoderefd_loan_path_to_string(&lp_base, out); |
| out.push('.'); |
| out.push_str(&info.as_str()); |
| } |
| |
| LpExtend(ref lp_base, _, LpInterior(_, InteriorElement)) => { |
| self.append_autoderefd_loan_path_to_string(&lp_base, out); |
| out.push_str("[..]"); |
| } |
| |
| LpExtend(ref lp_base, _, LpDeref(_)) => { |
| out.push('*'); |
| self.append_loan_path_to_string(&lp_base, out); |
| } |
| } |
| } |
| |
| pub fn append_autoderefd_loan_path_to_string(&self, |
| loan_path: &LoanPath<'tcx>, |
| out: &mut String) { |
| match loan_path.kind { |
| LpExtend(ref lp_base, _, LpDeref(_)) => { |
| // For a path like `(*x).f` or `(*x)[3]`, autoderef |
| // rules would normally allow users to omit the `*x`. |
| // So just serialize such paths to `x.f` or x[3]` respectively. |
| self.append_autoderefd_loan_path_to_string(&lp_base, out) |
| } |
| |
| LpDowncast(ref lp_base, variant_def_id) => { |
| out.push('('); |
| self.append_autoderefd_loan_path_to_string(&lp_base, out); |
| out.push_str(DOWNCAST_PRINTED_OPERATOR); |
| out.push_str(&self.tcx.def_path_str(variant_def_id)); |
| out.push(')'); |
| } |
| |
| LpVar(..) | LpUpvar(..) | LpExtend(.., LpInterior(..)) => { |
| self.append_loan_path_to_string(loan_path, out) |
| } |
| } |
| } |
| |
| pub fn loan_path_to_string(&self, loan_path: &LoanPath<'tcx>) -> String { |
| let mut result = String::new(); |
| self.append_loan_path_to_string(loan_path, &mut result); |
| result |
| } |
| |
| pub fn cmt_to_cow_str(&self, cmt: &mc::cmt_<'tcx>) -> Cow<'static, str> { |
| cmt.descriptive_string(self.tcx) |
| } |
| |
| pub fn cmt_to_path_or_string(&self, cmt: &mc::cmt_<'tcx>) -> String { |
| match opt_loan_path(cmt) { |
| Some(lp) => format!("`{}`", self.loan_path_to_string(&lp)), |
| None => self.cmt_to_cow_str(cmt).into_owned(), |
| } |
| } |
| } |
| |
| impl BitwiseOperator for LoanDataFlowOperator { |
| #[inline] |
| fn join(&self, succ: usize, pred: usize) -> usize { |
| succ | pred // loans from both preds are in scope |
| } |
| } |
| |
| impl DataFlowOperator for LoanDataFlowOperator { |
| #[inline] |
| fn initial_value(&self) -> bool { |
| false // no loans in scope by default |
| } |
| } |
| |
| impl fmt::Debug for InteriorKind { |
| fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { |
| match *self { |
| InteriorField(mc::FieldIndex(_, info)) => write!(f, "{}", info), |
| InteriorElement => write!(f, "[]"), |
| } |
| } |
| } |
| |
| impl<'tcx> fmt::Debug for Loan<'tcx> { |
| fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { |
| write!(f, "Loan_{}({:?}, {:?}, {:?}-{:?}, {:?})", |
| self.index, |
| self.loan_path, |
| self.kind, |
| self.gen_scope, |
| self.kill_scope, |
| self.restricted_paths) |
| } |
| } |
| |
| impl<'tcx> fmt::Debug for LoanPath<'tcx> { |
| fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { |
| match self.kind { |
| LpVar(id) => { |
| write!(f, "$({})", ty::tls::with(|tcx| tcx.hir().node_to_string(id))) |
| } |
| |
| LpUpvar(ty::UpvarId{ var_path: ty::UpvarPath {hir_id: var_id}, closure_expr_id }) => { |
| let s = ty::tls::with(|tcx| { |
| tcx.hir().node_to_string(var_id) |
| }); |
| write!(f, "$({} captured by id={:?})", s, closure_expr_id) |
| } |
| |
| LpDowncast(ref lp, variant_def_id) => { |
| let variant_str = if variant_def_id.is_local() { |
| ty::tls::with(|tcx| tcx.def_path_str(variant_def_id)) |
| } else { |
| format!("{:?}", variant_def_id) |
| }; |
| write!(f, "({:?}{}{})", lp, DOWNCAST_PRINTED_OPERATOR, variant_str) |
| } |
| |
| LpExtend(ref lp, _, LpDeref(_)) => { |
| write!(f, "{:?}.*", lp) |
| } |
| |
| LpExtend(ref lp, _, LpInterior(_, ref interior)) => { |
| write!(f, "{:?}.{:?}", lp, interior) |
| } |
| } |
| } |
| } |
| |
| impl<'tcx> fmt::Display for LoanPath<'tcx> { |
| fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { |
| match self.kind { |
| LpVar(id) => { |
| write!(f, "$({})", ty::tls::with(|tcx| tcx.hir().hir_to_user_string(id))) |
| } |
| |
| LpUpvar(ty::UpvarId{ var_path: ty::UpvarPath { hir_id }, closure_expr_id: _ }) => { |
| let s = ty::tls::with(|tcx| { |
| tcx.hir().node_to_string(hir_id) |
| }); |
| write!(f, "$({} captured by closure)", s) |
| } |
| |
| LpDowncast(ref lp, variant_def_id) => { |
| let variant_str = if variant_def_id.is_local() { |
| ty::tls::with(|tcx| tcx.def_path_str(variant_def_id)) |
| } else { |
| format!("{:?}", variant_def_id) |
| }; |
| write!(f, "({}{}{})", lp, DOWNCAST_PRINTED_OPERATOR, variant_str) |
| } |
| |
| LpExtend(ref lp, _, LpDeref(_)) => { |
| write!(f, "{}.*", lp) |
| } |
| |
| LpExtend(ref lp, _, LpInterior(_, ref interior)) => { |
| write!(f, "{}.{:?}", lp, interior) |
| } |
| } |
| } |
| } |