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Diffstat (limited to 'compiler/rustc_borrowck/src/lib.rs')
| -rw-r--r-- | compiler/rustc_borrowck/src/lib.rs | 2380 |
1 files changed, 2380 insertions, 0 deletions
diff --git a/compiler/rustc_borrowck/src/lib.rs b/compiler/rustc_borrowck/src/lib.rs new file mode 100644 index 000000000..3d8b07382 --- /dev/null +++ b/compiler/rustc_borrowck/src/lib.rs @@ -0,0 +1,2380 @@ +//! This query borrow-checks the MIR to (further) ensure it is not broken. + +#![allow(rustc::potential_query_instability)] +#![feature(box_patterns)] +#![feature(let_chains)] +#![feature(let_else)] +#![feature(min_specialization)] +#![feature(never_type)] +#![feature(rustc_attrs)] +#![feature(stmt_expr_attributes)] +#![feature(trusted_step)] +#![feature(try_blocks)] +#![recursion_limit = "256"] + +#[macro_use] +extern crate rustc_middle; +#[macro_use] +extern crate tracing; + +use rustc_data_structures::fx::{FxHashMap, FxHashSet}; +use rustc_data_structures::graph::dominators::Dominators; +use rustc_errors::{Applicability, Diagnostic, DiagnosticBuilder, ErrorGuaranteed}; +use rustc_hir as hir; +use rustc_hir::def_id::LocalDefId; +use rustc_index::bit_set::ChunkedBitSet; +use rustc_index::vec::IndexVec; +use rustc_infer::infer::{DefiningAnchor, InferCtxt, TyCtxtInferExt}; +use rustc_middle::mir::{ + traversal, Body, ClearCrossCrate, Local, Location, Mutability, Operand, Place, PlaceElem, + PlaceRef, VarDebugInfoContents, +}; +use rustc_middle::mir::{AggregateKind, BasicBlock, BorrowCheckResult, BorrowKind}; +use rustc_middle::mir::{Field, ProjectionElem, Promoted, Rvalue, Statement, StatementKind}; +use rustc_middle::mir::{InlineAsmOperand, Terminator, TerminatorKind}; +use rustc_middle::ty::query::Providers; +use rustc_middle::ty::{self, CapturedPlace, ParamEnv, RegionVid, TyCtxt}; +use rustc_session::lint::builtin::UNUSED_MUT; +use rustc_span::{Span, Symbol}; + +use either::Either; +use smallvec::SmallVec; +use std::cell::RefCell; +use std::collections::BTreeMap; +use std::rc::Rc; + +use rustc_mir_dataflow::impls::{ + EverInitializedPlaces, MaybeInitializedPlaces, MaybeUninitializedPlaces, +}; +use rustc_mir_dataflow::move_paths::{InitIndex, MoveOutIndex, MovePathIndex}; +use rustc_mir_dataflow::move_paths::{InitLocation, LookupResult, MoveData, MoveError}; +use rustc_mir_dataflow::Analysis; +use rustc_mir_dataflow::MoveDataParamEnv; + +use self::diagnostics::{AccessKind, RegionName}; +use self::location::LocationTable; +use self::prefixes::PrefixSet; +use facts::AllFacts; + +use self::path_utils::*; + +pub mod borrow_set; +mod borrowck_errors; +mod constraint_generation; +mod constraints; +mod dataflow; +mod def_use; +mod diagnostics; +mod facts; +mod invalidation; +mod location; +mod member_constraints; +mod nll; +mod path_utils; +mod place_ext; +mod places_conflict; +mod prefixes; +mod region_infer; +mod renumber; +mod session_diagnostics; +mod type_check; +mod universal_regions; +mod used_muts; + +// A public API provided for the Rust compiler consumers. +pub mod consumers; + +use borrow_set::{BorrowData, BorrowSet}; +use dataflow::{BorrowIndex, BorrowckFlowState as Flows, BorrowckResults, Borrows}; +use nll::{PoloniusOutput, ToRegionVid}; +use place_ext::PlaceExt; +use places_conflict::{places_conflict, PlaceConflictBias}; +use region_infer::RegionInferenceContext; + +// FIXME(eddyb) perhaps move this somewhere more centrally. +#[derive(Debug)] +struct Upvar<'tcx> { + place: CapturedPlace<'tcx>, + + /// If true, the capture is behind a reference. + by_ref: bool, +} + +/// Associate some local constants with the `'tcx` lifetime +struct TyCtxtConsts<'tcx>(TyCtxt<'tcx>); +impl<'tcx> TyCtxtConsts<'tcx> { + const DEREF_PROJECTION: &'tcx [PlaceElem<'tcx>; 1] = &[ProjectionElem::Deref]; +} + +pub fn provide(providers: &mut Providers) { + *providers = Providers { + mir_borrowck: |tcx, did| { + if let Some(def) = ty::WithOptConstParam::try_lookup(did, tcx) { + tcx.mir_borrowck_const_arg(def) + } else { + mir_borrowck(tcx, ty::WithOptConstParam::unknown(did)) + } + }, + mir_borrowck_const_arg: |tcx, (did, param_did)| { + mir_borrowck(tcx, ty::WithOptConstParam { did, const_param_did: Some(param_did) }) + }, + ..*providers + }; +} + +fn mir_borrowck<'tcx>( + tcx: TyCtxt<'tcx>, + def: ty::WithOptConstParam<LocalDefId>, +) -> &'tcx BorrowCheckResult<'tcx> { + let (input_body, promoted) = tcx.mir_promoted(def); + debug!("run query mir_borrowck: {}", tcx.def_path_str(def.did.to_def_id())); + let hir_owner = tcx.hir().local_def_id_to_hir_id(def.did).owner; + + let opt_closure_req = tcx + .infer_ctxt() + .with_opaque_type_inference(DefiningAnchor::Bind(hir_owner)) + .enter(|infcx| { + let input_body: &Body<'_> = &input_body.borrow(); + let promoted: &IndexVec<_, _> = &promoted.borrow(); + do_mir_borrowck(&infcx, input_body, promoted, false).0 + }); + debug!("mir_borrowck done"); + + tcx.arena.alloc(opt_closure_req) +} + +/// Perform the actual borrow checking. +/// +/// If `return_body_with_facts` is true, then return the body with non-erased +/// region ids on which the borrow checking was performed together with Polonius +/// facts. +#[instrument(skip(infcx, input_body, input_promoted), fields(id=?input_body.source.with_opt_param().as_local().unwrap()), level = "debug")] +fn do_mir_borrowck<'a, 'tcx>( + infcx: &InferCtxt<'a, 'tcx>, + input_body: &Body<'tcx>, + input_promoted: &IndexVec<Promoted, Body<'tcx>>, + return_body_with_facts: bool, +) -> (BorrowCheckResult<'tcx>, Option<Box<BodyWithBorrowckFacts<'tcx>>>) { + let def = input_body.source.with_opt_param().as_local().unwrap(); + + debug!(?def); + + let tcx = infcx.tcx; + let param_env = tcx.param_env(def.did); + + let mut local_names = IndexVec::from_elem(None, &input_body.local_decls); + for var_debug_info in &input_body.var_debug_info { + if let VarDebugInfoContents::Place(place) = var_debug_info.value { + if let Some(local) = place.as_local() { + if let Some(prev_name) = local_names[local] && var_debug_info.name != prev_name { + span_bug!( + var_debug_info.source_info.span, + "local {:?} has many names (`{}` vs `{}`)", + local, + prev_name, + var_debug_info.name + ); + } + local_names[local] = Some(var_debug_info.name); + } + } + } + + let mut errors = error::BorrowckErrors::new(); + + // Gather the upvars of a closure, if any. + let tables = tcx.typeck_opt_const_arg(def); + if let Some(ErrorGuaranteed { .. }) = tables.tainted_by_errors { + infcx.set_tainted_by_errors(); + errors.set_tainted_by_errors(); + } + let upvars: Vec<_> = tables + .closure_min_captures_flattened(def.did) + .map(|captured_place| { + let capture = captured_place.info.capture_kind; + let by_ref = match capture { + ty::UpvarCapture::ByValue => false, + ty::UpvarCapture::ByRef(..) => true, + }; + Upvar { place: captured_place.clone(), by_ref } + }) + .collect(); + + // Replace all regions with fresh inference variables. This + // requires first making our own copy of the MIR. This copy will + // be modified (in place) to contain non-lexical lifetimes. It + // will have a lifetime tied to the inference context. + let mut body_owned = input_body.clone(); + let mut promoted = input_promoted.clone(); + let free_regions = + nll::replace_regions_in_mir(infcx, param_env, &mut body_owned, &mut promoted); + let body = &body_owned; // no further changes + + let location_table_owned = LocationTable::new(body); + let location_table = &location_table_owned; + + let (move_data, move_errors): (MoveData<'tcx>, Vec<(Place<'tcx>, MoveError<'tcx>)>) = + match MoveData::gather_moves(&body, tcx, param_env) { + Ok((_, move_data)) => (move_data, Vec::new()), + Err((move_data, move_errors)) => (move_data, move_errors), + }; + let promoted_errors = promoted + .iter_enumerated() + .map(|(idx, body)| (idx, MoveData::gather_moves(&body, tcx, param_env))); + + let mdpe = MoveDataParamEnv { move_data, param_env }; + + let mut flow_inits = MaybeInitializedPlaces::new(tcx, &body, &mdpe) + .into_engine(tcx, &body) + .pass_name("borrowck") + .iterate_to_fixpoint() + .into_results_cursor(&body); + + let locals_are_invalidated_at_exit = tcx.hir().body_owner_kind(def.did).is_fn_or_closure(); + let borrow_set = + Rc::new(BorrowSet::build(tcx, body, locals_are_invalidated_at_exit, &mdpe.move_data)); + + let use_polonius = return_body_with_facts || infcx.tcx.sess.opts.unstable_opts.polonius; + + // Compute non-lexical lifetimes. + let nll::NllOutput { + regioncx, + opaque_type_values, + polonius_input, + polonius_output, + opt_closure_req, + nll_errors, + } = nll::compute_regions( + infcx, + free_regions, + body, + &promoted, + location_table, + param_env, + &mut flow_inits, + &mdpe.move_data, + &borrow_set, + &upvars, + use_polonius, + ); + + // Dump MIR results into a file, if that is enabled. This let us + // write unit-tests, as well as helping with debugging. + nll::dump_mir_results(infcx, &body, ®ioncx, &opt_closure_req); + + // We also have a `#[rustc_regions]` annotation that causes us to dump + // information. + nll::dump_annotation( + infcx, + &body, + ®ioncx, + &opt_closure_req, + &opaque_type_values, + &mut errors, + ); + + // The various `flow_*` structures can be large. We drop `flow_inits` here + // so it doesn't overlap with the others below. This reduces peak memory + // usage significantly on some benchmarks. + drop(flow_inits); + + let regioncx = Rc::new(regioncx); + + let flow_borrows = Borrows::new(tcx, body, ®ioncx, &borrow_set) + .into_engine(tcx, body) + .pass_name("borrowck") + .iterate_to_fixpoint(); + let flow_uninits = MaybeUninitializedPlaces::new(tcx, body, &mdpe) + .into_engine(tcx, body) + .pass_name("borrowck") + .iterate_to_fixpoint(); + let flow_ever_inits = EverInitializedPlaces::new(tcx, body, &mdpe) + .into_engine(tcx, body) + .pass_name("borrowck") + .iterate_to_fixpoint(); + + let movable_generator = + // The first argument is the generator type passed by value + if let Some(local) = body.local_decls.raw.get(1) + // Get the interior types and substs which typeck computed + && let ty::Generator(_, _, hir::Movability::Static) = local.ty.kind() + { + false + } else { + true + }; + + for (idx, move_data_results) in promoted_errors { + let promoted_body = &promoted[idx]; + + if let Err((move_data, move_errors)) = move_data_results { + let mut promoted_mbcx = MirBorrowckCtxt { + infcx, + param_env, + body: promoted_body, + move_data: &move_data, + location_table, // no need to create a real one for the promoted, it is not used + movable_generator, + fn_self_span_reported: Default::default(), + locals_are_invalidated_at_exit, + access_place_error_reported: Default::default(), + reservation_error_reported: Default::default(), + uninitialized_error_reported: Default::default(), + regioncx: regioncx.clone(), + used_mut: Default::default(), + used_mut_upvars: SmallVec::new(), + borrow_set: Rc::clone(&borrow_set), + dominators: Dominators::dummy(), // not used + upvars: Vec::new(), + local_names: IndexVec::from_elem(None, &promoted_body.local_decls), + region_names: RefCell::default(), + next_region_name: RefCell::new(1), + polonius_output: None, + errors, + }; + promoted_mbcx.report_move_errors(move_errors); + errors = promoted_mbcx.errors; + }; + } + + let dominators = body.basic_blocks.dominators(); + + let mut mbcx = MirBorrowckCtxt { + infcx, + param_env, + body, + move_data: &mdpe.move_data, + location_table, + movable_generator, + locals_are_invalidated_at_exit, + fn_self_span_reported: Default::default(), + access_place_error_reported: Default::default(), + reservation_error_reported: Default::default(), + uninitialized_error_reported: Default::default(), + regioncx: Rc::clone(®ioncx), + used_mut: Default::default(), + used_mut_upvars: SmallVec::new(), + borrow_set: Rc::clone(&borrow_set), + dominators, + upvars, + local_names, + region_names: RefCell::default(), + next_region_name: RefCell::new(1), + polonius_output, + errors, + }; + + // Compute and report region errors, if any. + mbcx.report_region_errors(nll_errors); + + let results = BorrowckResults { + ever_inits: flow_ever_inits, + uninits: flow_uninits, + borrows: flow_borrows, + }; + + mbcx.report_move_errors(move_errors); + + rustc_mir_dataflow::visit_results( + body, + traversal::reverse_postorder(body).map(|(bb, _)| bb), + &results, + &mut mbcx, + ); + + // For each non-user used mutable variable, check if it's been assigned from + // a user-declared local. If so, then put that local into the used_mut set. + // Note that this set is expected to be small - only upvars from closures + // would have a chance of erroneously adding non-user-defined mutable vars + // to the set. + let temporary_used_locals: FxHashSet<Local> = mbcx + .used_mut + .iter() + .filter(|&local| !mbcx.body.local_decls[*local].is_user_variable()) + .cloned() + .collect(); + // For the remaining unused locals that are marked as mutable, we avoid linting any that + // were never initialized. These locals may have been removed as unreachable code; or will be + // linted as unused variables. + let unused_mut_locals = + mbcx.body.mut_vars_iter().filter(|local| !mbcx.used_mut.contains(local)).collect(); + mbcx.gather_used_muts(temporary_used_locals, unused_mut_locals); + + debug!("mbcx.used_mut: {:?}", mbcx.used_mut); + let used_mut = std::mem::take(&mut mbcx.used_mut); + for local in mbcx.body.mut_vars_and_args_iter().filter(|local| !used_mut.contains(local)) { + let local_decl = &mbcx.body.local_decls[local]; + let lint_root = match &mbcx.body.source_scopes[local_decl.source_info.scope].local_data { + ClearCrossCrate::Set(data) => data.lint_root, + _ => continue, + }; + + // Skip over locals that begin with an underscore or have no name + match mbcx.local_names[local] { + Some(name) => { + if name.as_str().starts_with('_') { + continue; + } + } + None => continue, + } + + let span = local_decl.source_info.span; + if span.desugaring_kind().is_some() { + // If the `mut` arises as part of a desugaring, we should ignore it. + continue; + } + + tcx.struct_span_lint_hir(UNUSED_MUT, lint_root, span, |lint| { + let mut_span = tcx.sess.source_map().span_until_non_whitespace(span); + lint.build("variable does not need to be mutable") + .span_suggestion_short( + mut_span, + "remove this `mut`", + "", + Applicability::MachineApplicable, + ) + .emit(); + }) + } + + let tainted_by_errors = mbcx.emit_errors(); + + let result = BorrowCheckResult { + concrete_opaque_types: opaque_type_values, + closure_requirements: opt_closure_req, + used_mut_upvars: mbcx.used_mut_upvars, + tainted_by_errors, + }; + + let body_with_facts = if return_body_with_facts { + let output_facts = mbcx.polonius_output.expect("Polonius output was not computed"); + Some(Box::new(BodyWithBorrowckFacts { + body: body_owned, + input_facts: *polonius_input.expect("Polonius input facts were not generated"), + output_facts, + location_table: location_table_owned, + })) + } else { + None + }; + + debug!("do_mir_borrowck: result = {:#?}", result); + + (result, body_with_facts) +} + +/// A `Body` with information computed by the borrow checker. This struct is +/// intended to be consumed by compiler consumers. +/// +/// We need to include the MIR body here because the region identifiers must +/// match the ones in the Polonius facts. +pub struct BodyWithBorrowckFacts<'tcx> { + /// A mir body that contains region identifiers. + pub body: Body<'tcx>, + /// Polonius input facts. + pub input_facts: AllFacts, + /// Polonius output facts. + pub output_facts: Rc<self::nll::PoloniusOutput>, + /// The table that maps Polonius points to locations in the table. + pub location_table: LocationTable, +} + +struct MirBorrowckCtxt<'cx, 'tcx> { + infcx: &'cx InferCtxt<'cx, 'tcx>, + param_env: ParamEnv<'tcx>, + body: &'cx Body<'tcx>, + move_data: &'cx MoveData<'tcx>, + + /// Map from MIR `Location` to `LocationIndex`; created + /// when MIR borrowck begins. + location_table: &'cx LocationTable, + + movable_generator: bool, + /// This keeps track of whether local variables are free-ed when the function + /// exits even without a `StorageDead`, which appears to be the case for + /// constants. + /// + /// I'm not sure this is the right approach - @eddyb could you try and + /// figure this out? + locals_are_invalidated_at_exit: bool, + /// This field keeps track of when borrow errors are reported in the access_place function + /// so that there is no duplicate reporting. This field cannot also be used for the conflicting + /// borrow errors that is handled by the `reservation_error_reported` field as the inclusion + /// of the `Span` type (while required to mute some errors) stops the muting of the reservation + /// errors. + access_place_error_reported: FxHashSet<(Place<'tcx>, Span)>, + /// This field keeps track of when borrow conflict errors are reported + /// for reservations, so that we don't report seemingly duplicate + /// errors for corresponding activations. + // + // FIXME: ideally this would be a set of `BorrowIndex`, not `Place`s, + // but it is currently inconvenient to track down the `BorrowIndex` + // at the time we detect and report a reservation error. + reservation_error_reported: FxHashSet<Place<'tcx>>, + /// This fields keeps track of the `Span`s that we have + /// used to report extra information for `FnSelfUse`, to avoid + /// unnecessarily verbose errors. + fn_self_span_reported: FxHashSet<Span>, + /// This field keeps track of errors reported in the checking of uninitialized variables, + /// so that we don't report seemingly duplicate errors. + uninitialized_error_reported: FxHashSet<PlaceRef<'tcx>>, + /// This field keeps track of all the local variables that are declared mut and are mutated. + /// Used for the warning issued by an unused mutable local variable. + used_mut: FxHashSet<Local>, + /// If the function we're checking is a closure, then we'll need to report back the list of + /// mutable upvars that have been used. This field keeps track of them. + used_mut_upvars: SmallVec<[Field; 8]>, + /// Region inference context. This contains the results from region inference and lets us e.g. + /// find out which CFG points are contained in each borrow region. + regioncx: Rc<RegionInferenceContext<'tcx>>, + + /// The set of borrows extracted from the MIR + borrow_set: Rc<BorrowSet<'tcx>>, + + /// Dominators for MIR + dominators: Dominators<BasicBlock>, + + /// Information about upvars not necessarily preserved in types or MIR + upvars: Vec<Upvar<'tcx>>, + + /// Names of local (user) variables (extracted from `var_debug_info`). + local_names: IndexVec<Local, Option<Symbol>>, + + /// Record the region names generated for each region in the given + /// MIR def so that we can reuse them later in help/error messages. + region_names: RefCell<FxHashMap<RegionVid, RegionName>>, + + /// The counter for generating new region names. + next_region_name: RefCell<usize>, + + /// Results of Polonius analysis. + polonius_output: Option<Rc<PoloniusOutput>>, + + errors: error::BorrowckErrors<'tcx>, +} + +// Check that: +// 1. assignments are always made to mutable locations (FIXME: does that still really go here?) +// 2. loans made in overlapping scopes do not conflict +// 3. assignments do not affect things loaned out as immutable +// 4. moves do not affect things loaned out in any way +impl<'cx, 'tcx> rustc_mir_dataflow::ResultsVisitor<'cx, 'tcx> for MirBorrowckCtxt<'cx, 'tcx> { + type FlowState = Flows<'cx, 'tcx>; + + fn visit_statement_before_primary_effect( + &mut self, + flow_state: &Flows<'cx, 'tcx>, + stmt: &'cx Statement<'tcx>, + location: Location, + ) { + debug!("MirBorrowckCtxt::process_statement({:?}, {:?}): {:?}", location, stmt, flow_state); + let span = stmt.source_info.span; + + self.check_activations(location, span, flow_state); + + match &stmt.kind { + StatementKind::Assign(box (lhs, ref rhs)) => { + self.consume_rvalue(location, (rhs, span), flow_state); + + self.mutate_place(location, (*lhs, span), Shallow(None), flow_state); + } + StatementKind::FakeRead(box (_, ref place)) => { + // Read for match doesn't access any memory and is used to + // assert that a place is safe and live. So we don't have to + // do any checks here. + // + // FIXME: Remove check that the place is initialized. This is + // needed for now because matches don't have never patterns yet. + // So this is the only place we prevent + // let x: !; + // match x {}; + // from compiling. + self.check_if_path_or_subpath_is_moved( + location, + InitializationRequiringAction::Use, + (place.as_ref(), span), + flow_state, + ); + } + StatementKind::CopyNonOverlapping(box rustc_middle::mir::CopyNonOverlapping { + .. + }) => { + span_bug!( + span, + "Unexpected CopyNonOverlapping, should only appear after lower_intrinsics", + ) + } + StatementKind::Nop + | StatementKind::Coverage(..) + | StatementKind::AscribeUserType(..) + | StatementKind::Retag { .. } + | StatementKind::StorageLive(..) => { + // `Nop`, `AscribeUserType`, `Retag`, and `StorageLive` are irrelevant + // to borrow check. + } + StatementKind::StorageDead(local) => { + self.access_place( + location, + (Place::from(*local), span), + (Shallow(None), Write(WriteKind::StorageDeadOrDrop)), + LocalMutationIsAllowed::Yes, + flow_state, + ); + } + StatementKind::Deinit(..) | StatementKind::SetDiscriminant { .. } => { + bug!("Statement not allowed in this MIR phase") + } + } + } + + fn visit_terminator_before_primary_effect( + &mut self, + flow_state: &Flows<'cx, 'tcx>, + term: &'cx Terminator<'tcx>, + loc: Location, + ) { + debug!("MirBorrowckCtxt::process_terminator({:?}, {:?}): {:?}", loc, term, flow_state); + let span = term.source_info.span; + + self.check_activations(loc, span, flow_state); + + match term.kind { + TerminatorKind::SwitchInt { ref discr, switch_ty: _, targets: _ } => { + self.consume_operand(loc, (discr, span), flow_state); + } + TerminatorKind::Drop { place, target: _, unwind: _ } => { + debug!( + "visit_terminator_drop \ + loc: {:?} term: {:?} place: {:?} span: {:?}", + loc, term, place, span + ); + + self.access_place( + loc, + (place, span), + (AccessDepth::Drop, Write(WriteKind::StorageDeadOrDrop)), + LocalMutationIsAllowed::Yes, + flow_state, + ); + } + TerminatorKind::DropAndReplace { + place: drop_place, + value: ref new_value, + target: _, + unwind: _, + } => { + self.mutate_place(loc, (drop_place, span), Deep, flow_state); + self.consume_operand(loc, (new_value, span), flow_state); + } + TerminatorKind::Call { + ref func, + ref args, + destination, + target: _, + cleanup: _, + from_hir_call: _, + fn_span: _, + } => { + self.consume_operand(loc, (func, span), flow_state); + for arg in args { + self.consume_operand(loc, (arg, span), flow_state); + } + self.mutate_place(loc, (destination, span), Deep, flow_state); + } + TerminatorKind::Assert { ref cond, expected: _, ref msg, target: _, cleanup: _ } => { + self.consume_operand(loc, (cond, span), flow_state); + use rustc_middle::mir::AssertKind; + if let AssertKind::BoundsCheck { ref len, ref index } = *msg { + self.consume_operand(loc, (len, span), flow_state); + self.consume_operand(loc, (index, span), flow_state); + } + } + + TerminatorKind::Yield { ref value, resume: _, resume_arg, drop: _ } => { + self.consume_operand(loc, (value, span), flow_state); + self.mutate_place(loc, (resume_arg, span), Deep, flow_state); + } + + TerminatorKind::InlineAsm { + template: _, + ref operands, + options: _, + line_spans: _, + destination: _, + cleanup: _, + } => { + for op in operands { + match *op { + InlineAsmOperand::In { reg: _, ref value } => { + self.consume_operand(loc, (value, span), flow_state); + } + InlineAsmOperand::Out { reg: _, late: _, place, .. } => { + if let Some(place) = place { + self.mutate_place(loc, (place, span), Shallow(None), flow_state); + } + } + InlineAsmOperand::InOut { reg: _, late: _, ref in_value, out_place } => { + self.consume_operand(loc, (in_value, span), flow_state); + if let Some(out_place) = out_place { + self.mutate_place( + loc, + (out_place, span), + Shallow(None), + flow_state, + ); + } + } + InlineAsmOperand::Const { value: _ } + | InlineAsmOperand::SymFn { value: _ } + | InlineAsmOperand::SymStatic { def_id: _ } => {} + } + } + } + + TerminatorKind::Goto { target: _ } + | TerminatorKind::Abort + | TerminatorKind::Unreachable + | TerminatorKind::Resume + | TerminatorKind::Return + | TerminatorKind::GeneratorDrop + | TerminatorKind::FalseEdge { real_target: _, imaginary_target: _ } + | TerminatorKind::FalseUnwind { real_target: _, unwind: _ } => { + // no data used, thus irrelevant to borrowck + } + } + } + + fn visit_terminator_after_primary_effect( + &mut self, + flow_state: &Flows<'cx, 'tcx>, + term: &'cx Terminator<'tcx>, + loc: Location, + ) { + let span = term.source_info.span; + + match term.kind { + TerminatorKind::Yield { value: _, resume: _, resume_arg: _, drop: _ } => { + if self.movable_generator { + // Look for any active borrows to locals + let borrow_set = self.borrow_set.clone(); + for i in flow_state.borrows.iter() { + let borrow = &borrow_set[i]; + self.check_for_local_borrow(borrow, span); + } + } + } + + TerminatorKind::Resume | TerminatorKind::Return | TerminatorKind::GeneratorDrop => { + // Returning from the function implicitly kills storage for all locals and statics. + // Often, the storage will already have been killed by an explicit + // StorageDead, but we don't always emit those (notably on unwind paths), + // so this "extra check" serves as a kind of backup. + let borrow_set = self.borrow_set.clone(); + for i in flow_state.borrows.iter() { + let borrow = &borrow_set[i]; + self.check_for_invalidation_at_exit(loc, borrow, span); + } + } + + TerminatorKind::Abort + | TerminatorKind::Assert { .. } + | TerminatorKind::Call { .. } + | TerminatorKind::Drop { .. } + | TerminatorKind::DropAndReplace { .. } + | TerminatorKind::FalseEdge { real_target: _, imaginary_target: _ } + | TerminatorKind::FalseUnwind { real_target: _, unwind: _ } + | TerminatorKind::Goto { .. } + | TerminatorKind::SwitchInt { .. } + | TerminatorKind::Unreachable + | TerminatorKind::InlineAsm { .. } => {} + } + } +} + +use self::AccessDepth::{Deep, Shallow}; +use self::ReadOrWrite::{Activation, Read, Reservation, Write}; + +#[derive(Copy, Clone, PartialEq, Eq, Debug)] +enum ArtificialField { + ArrayLength, + ShallowBorrow, +} + +#[derive(Copy, Clone, PartialEq, Eq, Debug)] +enum AccessDepth { + /// From the RFC: "A *shallow* access means that the immediate + /// fields reached at P are accessed, but references or pointers + /// found within are not dereferenced. Right now, the only access + /// that is shallow is an assignment like `x = ...;`, which would + /// be a *shallow write* of `x`." + Shallow(Option<ArtificialField>), + + /// From the RFC: "A *deep* access means that all data reachable + /// through the given place may be invalidated or accesses by + /// this action." + Deep, + + /// Access is Deep only when there is a Drop implementation that + /// can reach the data behind the reference. + Drop, +} + +/// Kind of access to a value: read or write +/// (For informational purposes only) +#[derive(Copy, Clone, PartialEq, Eq, Debug)] +enum ReadOrWrite { + /// From the RFC: "A *read* means that the existing data may be + /// read, but will not be changed." + Read(ReadKind), + + /// From the RFC: "A *write* means that the data may be mutated to + /// new values or otherwise invalidated (for example, it could be + /// de-initialized, as in a move operation). + Write(WriteKind), + + /// For two-phase borrows, we distinguish a reservation (which is treated + /// like a Read) from an activation (which is treated like a write), and + /// each of those is furthermore distinguished from Reads/Writes above. + Reservation(WriteKind), + Activation(WriteKind, BorrowIndex), +} + +/// Kind of read access to a value +/// (For informational purposes only) +#[derive(Copy, Clone, PartialEq, Eq, Debug)] +enum ReadKind { + Borrow(BorrowKind), + Copy, +} + +/// Kind of write access to a value +/// (For informational purposes only) +#[derive(Copy, Clone, PartialEq, Eq, Debug)] +enum WriteKind { + StorageDeadOrDrop, + MutableBorrow(BorrowKind), + Mutate, + Move, +} + +/// When checking permissions for a place access, this flag is used to indicate that an immutable +/// local place can be mutated. +// +// FIXME: @nikomatsakis suggested that this flag could be removed with the following modifications: +// - Merge `check_access_permissions()` and `check_if_reassignment_to_immutable_state()`. +// - Split `is_mutable()` into `is_assignable()` (can be directly assigned) and +// `is_declared_mutable()`. +// - Take flow state into consideration in `is_assignable()` for local variables. +#[derive(Copy, Clone, PartialEq, Eq, Debug)] +enum LocalMutationIsAllowed { + Yes, + /// We want use of immutable upvars to cause a "write to immutable upvar" + /// error, not an "reassignment" error. + ExceptUpvars, + No, +} + +#[derive(Copy, Clone, Debug)] +enum InitializationRequiringAction { + Borrow, + MatchOn, + Use, + Assignment, + PartialAssignment, +} + +struct RootPlace<'tcx> { + place_local: Local, + place_projection: &'tcx [PlaceElem<'tcx>], + is_local_mutation_allowed: LocalMutationIsAllowed, +} + +impl InitializationRequiringAction { + fn as_noun(self) -> &'static str { + match self { + InitializationRequiringAction::Borrow => "borrow", + InitializationRequiringAction::MatchOn => "use", // no good noun + InitializationRequiringAction::Use => "use", + InitializationRequiringAction::Assignment => "assign", + InitializationRequiringAction::PartialAssignment => "assign to part", + } + } + + fn as_verb_in_past_tense(self) -> &'static str { + match self { + InitializationRequiringAction::Borrow => "borrowed", + InitializationRequiringAction::MatchOn => "matched on", + InitializationRequiringAction::Use => "used", + InitializationRequiringAction::Assignment => "assigned", + InitializationRequiringAction::PartialAssignment => "partially assigned", + } + } + + fn as_general_verb_in_past_tense(self) -> &'static str { + match self { + InitializationRequiringAction::Borrow + | InitializationRequiringAction::MatchOn + | InitializationRequiringAction::Use => "used", + InitializationRequiringAction::Assignment => "assigned", + InitializationRequiringAction::PartialAssignment => "partially assigned", + } + } +} + +impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> { + fn body(&self) -> &'cx Body<'tcx> { + self.body + } + + /// Checks an access to the given place to see if it is allowed. Examines the set of borrows + /// that are in scope, as well as which paths have been initialized, to ensure that (a) the + /// place is initialized and (b) it is not borrowed in some way that would prevent this + /// access. + /// + /// Returns `true` if an error is reported. + fn access_place( + &mut self, + location: Location, + place_span: (Place<'tcx>, Span), + kind: (AccessDepth, ReadOrWrite), + is_local_mutation_allowed: LocalMutationIsAllowed, + flow_state: &Flows<'cx, 'tcx>, + ) { + let (sd, rw) = kind; + + if let Activation(_, borrow_index) = rw { + if self.reservation_error_reported.contains(&place_span.0) { + debug!( + "skipping access_place for activation of invalid reservation \ + place: {:?} borrow_index: {:?}", + place_span.0, borrow_index + ); + return; + } + } + + // Check is_empty() first because it's the common case, and doing that + // way we avoid the clone() call. + if !self.access_place_error_reported.is_empty() + && self.access_place_error_reported.contains(&(place_span.0, place_span.1)) + { + debug!( + "access_place: suppressing error place_span=`{:?}` kind=`{:?}`", + place_span, kind + ); + return; + } + + let mutability_error = self.check_access_permissions( + place_span, + rw, + is_local_mutation_allowed, + flow_state, + location, + ); + let conflict_error = + self.check_access_for_conflict(location, place_span, sd, rw, flow_state); + + if conflict_error || mutability_error { + debug!("access_place: logging error place_span=`{:?}` kind=`{:?}`", place_span, kind); + self.access_place_error_reported.insert((place_span.0, place_span.1)); + } + } + + fn check_access_for_conflict( + &mut self, + location: Location, + place_span: (Place<'tcx>, Span), + sd: AccessDepth, + rw: ReadOrWrite, + flow_state: &Flows<'cx, 'tcx>, + ) -> bool { + debug!( + "check_access_for_conflict(location={:?}, place_span={:?}, sd={:?}, rw={:?})", + location, place_span, sd, rw, + ); + + let mut error_reported = false; + let tcx = self.infcx.tcx; + let body = self.body; + let borrow_set = self.borrow_set.clone(); + + // Use polonius output if it has been enabled. + let polonius_output = self.polonius_output.clone(); + let borrows_in_scope = if let Some(polonius) = &polonius_output { + let location = self.location_table.start_index(location); + Either::Left(polonius.errors_at(location).iter().copied()) + } else { + Either::Right(flow_state.borrows.iter()) + }; + + each_borrow_involving_path( + self, + tcx, + body, + location, + (sd, place_span.0), + &borrow_set, + borrows_in_scope, + |this, borrow_index, borrow| match (rw, borrow.kind) { + // Obviously an activation is compatible with its own + // reservation (or even prior activating uses of same + // borrow); so don't check if they interfere. + // + // NOTE: *reservations* do conflict with themselves; + // thus aren't injecting unsoundness w/ this check.) + (Activation(_, activating), _) if activating == borrow_index => { + debug!( + "check_access_for_conflict place_span: {:?} sd: {:?} rw: {:?} \ + skipping {:?} b/c activation of same borrow_index", + place_span, + sd, + rw, + (borrow_index, borrow), + ); + Control::Continue + } + + (Read(_), BorrowKind::Shared | BorrowKind::Shallow) + | ( + Read(ReadKind::Borrow(BorrowKind::Shallow)), + BorrowKind::Unique | BorrowKind::Mut { .. }, + ) => Control::Continue, + + (Reservation(_), BorrowKind::Shallow | BorrowKind::Shared) => { + // This used to be a future compatibility warning (to be + // disallowed on NLL). See rust-lang/rust#56254 + Control::Continue + } + + (Write(WriteKind::Move), BorrowKind::Shallow) => { + // Handled by initialization checks. + Control::Continue + } + + (Read(kind), BorrowKind::Unique | BorrowKind::Mut { .. }) => { + // Reading from mere reservations of mutable-borrows is OK. + if !is_active(&this.dominators, borrow, location) { + assert!(allow_two_phase_borrow(borrow.kind)); + return Control::Continue; + } + + error_reported = true; + match kind { + ReadKind::Copy => { + let err = this + .report_use_while_mutably_borrowed(location, place_span, borrow); + this.buffer_error(err); + } + ReadKind::Borrow(bk) => { + let err = + this.report_conflicting_borrow(location, place_span, bk, borrow); + this.buffer_error(err); + } + } + Control::Break + } + + (Reservation(kind) | Activation(kind, _) | Write(kind), _) => { + match rw { + Reservation(..) => { + debug!( + "recording invalid reservation of \ + place: {:?}", + place_span.0 + ); + this.reservation_error_reported.insert(place_span.0); + } + Activation(_, activating) => { + debug!( + "observing check_place for activation of \ + borrow_index: {:?}", + activating + ); + } + Read(..) | Write(..) => {} + } + + error_reported = true; + match kind { + WriteKind::MutableBorrow(bk) => { + let err = + this.report_conflicting_borrow(location, place_span, bk, borrow); + this.buffer_error(err); + } + WriteKind::StorageDeadOrDrop => this + .report_borrowed_value_does_not_live_long_enough( + location, + borrow, + place_span, + Some(kind), + ), + WriteKind::Mutate => { + this.report_illegal_mutation_of_borrowed(location, place_span, borrow) + } + WriteKind::Move => { + this.report_move_out_while_borrowed(location, place_span, borrow) + } + } + Control::Break + } + }, + ); + + error_reported + } + + fn mutate_place( + &mut self, + location: Location, + place_span: (Place<'tcx>, Span), + kind: AccessDepth, + flow_state: &Flows<'cx, 'tcx>, + ) { + // Write of P[i] or *P requires P init'd. + self.check_if_assigned_path_is_moved(location, place_span, flow_state); + + // Special case: you can assign an immutable local variable + // (e.g., `x = ...`) so long as it has never been initialized + // before (at this point in the flow). + if let Some(local) = place_span.0.as_local() { + if let Mutability::Not = self.body.local_decls[local].mutability { + // check for reassignments to immutable local variables + self.check_if_reassignment_to_immutable_state( + location, local, place_span, flow_state, + ); + return; + } + } + + // Otherwise, use the normal access permission rules. + self.access_place( + location, + place_span, + (kind, Write(WriteKind::Mutate)), + LocalMutationIsAllowed::No, + flow_state, + ); + } + + fn consume_rvalue( + &mut self, + location: Location, + (rvalue, span): (&'cx Rvalue<'tcx>, Span), + flow_state: &Flows<'cx, 'tcx>, + ) { + match *rvalue { + Rvalue::Ref(_ /*rgn*/, bk, place) => { + let access_kind = match bk { + BorrowKind::Shallow => { + (Shallow(Some(ArtificialField::ShallowBorrow)), Read(ReadKind::Borrow(bk))) + } + BorrowKind::Shared => (Deep, Read(ReadKind::Borrow(bk))), + BorrowKind::Unique | BorrowKind::Mut { .. } => { + let wk = WriteKind::MutableBorrow(bk); + if allow_two_phase_borrow(bk) { + (Deep, Reservation(wk)) + } else { + (Deep, Write(wk)) + } + } + }; + + self.access_place( + location, + (place, span), + access_kind, + LocalMutationIsAllowed::No, + flow_state, + ); + + let action = if bk == BorrowKind::Shallow { + InitializationRequiringAction::MatchOn + } else { + InitializationRequiringAction::Borrow + }; + + self.check_if_path_or_subpath_is_moved( + location, + action, + (place.as_ref(), span), + flow_state, + ); + } + + Rvalue::AddressOf(mutability, place) => { + let access_kind = match mutability { + Mutability::Mut => ( + Deep, + Write(WriteKind::MutableBorrow(BorrowKind::Mut { + allow_two_phase_borrow: false, + })), + ), + Mutability::Not => (Deep, Read(ReadKind::Borrow(BorrowKind::Shared))), + }; + + self.access_place( + location, + (place, span), + access_kind, + LocalMutationIsAllowed::No, + flow_state, + ); + + self.check_if_path_or_subpath_is_moved( + location, + InitializationRequiringAction::Borrow, + (place.as_ref(), span), + flow_state, + ); + } + + Rvalue::ThreadLocalRef(_) => {} + + Rvalue::Use(ref operand) + | Rvalue::Repeat(ref operand, _) + | Rvalue::UnaryOp(_ /*un_op*/, ref operand) + | Rvalue::Cast(_ /*cast_kind*/, ref operand, _ /*ty*/) + | Rvalue::ShallowInitBox(ref operand, _ /*ty*/) => { + self.consume_operand(location, (operand, span), flow_state) + } + Rvalue::CopyForDeref(place) => { + self.access_place( + location, + (place, span), + (Deep, Read(ReadKind::Copy)), + LocalMutationIsAllowed::No, + flow_state, + ); + + // Finally, check if path was already moved. + self.check_if_path_or_subpath_is_moved( + location, + InitializationRequiringAction::Use, + (place.as_ref(), span), + flow_state, + ); + } + + Rvalue::Len(place) | Rvalue::Discriminant(place) => { + let af = match *rvalue { + Rvalue::Len(..) => Some(ArtificialField::ArrayLength), + Rvalue::Discriminant(..) => None, + _ => unreachable!(), + }; + self.access_place( + location, + (place, span), + (Shallow(af), Read(ReadKind::Copy)), + LocalMutationIsAllowed::No, + flow_state, + ); + self.check_if_path_or_subpath_is_moved( + location, + InitializationRequiringAction::Use, + (place.as_ref(), span), + flow_state, + ); + } + + Rvalue::BinaryOp(_bin_op, box (ref operand1, ref operand2)) + | Rvalue::CheckedBinaryOp(_bin_op, box (ref operand1, ref operand2)) => { + self.consume_operand(location, (operand1, span), flow_state); + self.consume_operand(location, (operand2, span), flow_state); + } + + Rvalue::NullaryOp(_op, _ty) => { + // nullary ops take no dynamic input; no borrowck effect. + } + + Rvalue::Aggregate(ref aggregate_kind, ref operands) => { + // We need to report back the list of mutable upvars that were + // moved into the closure and subsequently used by the closure, + // in order to populate our used_mut set. + match **aggregate_kind { + AggregateKind::Closure(def_id, _) | AggregateKind::Generator(def_id, _, _) => { + let BorrowCheckResult { used_mut_upvars, .. } = + self.infcx.tcx.mir_borrowck(def_id); + debug!("{:?} used_mut_upvars={:?}", def_id, used_mut_upvars); + for field in used_mut_upvars { + self.propagate_closure_used_mut_upvar(&operands[field.index()]); + } + } + AggregateKind::Adt(..) + | AggregateKind::Array(..) + | AggregateKind::Tuple { .. } => (), + } + + for operand in operands { + self.consume_operand(location, (operand, span), flow_state); + } + } + } + } + + fn propagate_closure_used_mut_upvar(&mut self, operand: &Operand<'tcx>) { + let propagate_closure_used_mut_place = |this: &mut Self, place: Place<'tcx>| { + // We have three possibilities here: + // a. We are modifying something through a mut-ref + // b. We are modifying something that is local to our parent + // c. Current body is a nested closure, and we are modifying path starting from + // a Place captured by our parent closure. + + // Handle (c), the path being modified is exactly the path captured by our parent + if let Some(field) = this.is_upvar_field_projection(place.as_ref()) { + this.used_mut_upvars.push(field); + return; + } + + for (place_ref, proj) in place.iter_projections().rev() { + // Handle (a) + if proj == ProjectionElem::Deref { + match place_ref.ty(this.body(), this.infcx.tcx).ty.kind() { + // We aren't modifying a variable directly + ty::Ref(_, _, hir::Mutability::Mut) => return, + + _ => {} + } + } + + // Handle (c) + if let Some(field) = this.is_upvar_field_projection(place_ref) { + this.used_mut_upvars.push(field); + return; + } + } + + // Handle(b) + this.used_mut.insert(place.local); + }; + + // This relies on the current way that by-value + // captures of a closure are copied/moved directly + // when generating MIR. + match *operand { + Operand::Move(place) | Operand::Copy(place) => { + match place.as_local() { + Some(local) if !self.body.local_decls[local].is_user_variable() => { + if self.body.local_decls[local].ty.is_mutable_ptr() { + // The variable will be marked as mutable by the borrow. + return; + } + // This is an edge case where we have a `move` closure + // inside a non-move closure, and the inner closure + // contains a mutation: + // + // let mut i = 0; + // || { move || { i += 1; }; }; + // + // In this case our usual strategy of assuming that the + // variable will be captured by mutable reference is + // wrong, since `i` can be copied into the inner + // closure from a shared reference. + // + // As such we have to search for the local that this + // capture comes from and mark it as being used as mut. + + let temp_mpi = self.move_data.rev_lookup.find_local(local); + let init = if let [init_index] = *self.move_data.init_path_map[temp_mpi] { + &self.move_data.inits[init_index] + } else { + bug!("temporary should be initialized exactly once") + }; + + let InitLocation::Statement(loc) = init.location else { + bug!("temporary initialized in arguments") + }; + + let body = self.body; + let bbd = &body[loc.block]; + let stmt = &bbd.statements[loc.statement_index]; + debug!("temporary assigned in: stmt={:?}", stmt); + + if let StatementKind::Assign(box (_, Rvalue::Ref(_, _, source))) = stmt.kind + { + propagate_closure_used_mut_place(self, source); + } else { + bug!( + "closures should only capture user variables \ + or references to user variables" + ); + } + } + _ => propagate_closure_used_mut_place(self, place), + } + } + Operand::Constant(..) => {} + } + } + + fn consume_operand( + &mut self, + location: Location, + (operand, span): (&'cx Operand<'tcx>, Span), + flow_state: &Flows<'cx, 'tcx>, + ) { + match *operand { + Operand::Copy(place) => { + // copy of place: check if this is "copy of frozen path" + // (FIXME: see check_loans.rs) + self.access_place( + location, + (place, span), + (Deep, Read(ReadKind::Copy)), + LocalMutationIsAllowed::No, + flow_state, + ); + + // Finally, check if path was already moved. + self.check_if_path_or_subpath_is_moved( + location, + InitializationRequiringAction::Use, + (place.as_ref(), span), + flow_state, + ); + } + Operand::Move(place) => { + // move of place: check if this is move of already borrowed path + self.access_place( + location, + (place, span), + (Deep, Write(WriteKind::Move)), + LocalMutationIsAllowed::Yes, + flow_state, + ); + + // Finally, check if path was already moved. + self.check_if_path_or_subpath_is_moved( + location, + InitializationRequiringAction::Use, + (place.as_ref(), span), + flow_state, + ); + } + Operand::Constant(_) => {} + } + } + + /// Checks whether a borrow of this place is invalidated when the function + /// exits + fn check_for_invalidation_at_exit( + &mut self, + location: Location, + borrow: &BorrowData<'tcx>, + span: Span, + ) { + debug!("check_for_invalidation_at_exit({:?})", borrow); + let place = borrow.borrowed_place; + let mut root_place = PlaceRef { local: place.local, projection: &[] }; + + // FIXME(nll-rfc#40): do more precise destructor tracking here. For now + // we just know that all locals are dropped at function exit (otherwise + // we'll have a memory leak) and assume that all statics have a destructor. + // + // FIXME: allow thread-locals to borrow other thread locals? + + let (might_be_alive, will_be_dropped) = + if self.body.local_decls[root_place.local].is_ref_to_thread_local() { + // Thread-locals might be dropped after the function exits + // We have to dereference the outer reference because + // borrows don't conflict behind shared references. + root_place.projection = TyCtxtConsts::DEREF_PROJECTION; + (true, true) + } else { + (false, self.locals_are_invalidated_at_exit) + }; + + if !will_be_dropped { + debug!("place_is_invalidated_at_exit({:?}) - won't be dropped", place); + return; + } + + let sd = if might_be_alive { Deep } else { Shallow(None) }; + + if places_conflict::borrow_conflicts_with_place( + self.infcx.tcx, + &self.body, + place, + borrow.kind, + root_place, + sd, + places_conflict::PlaceConflictBias::Overlap, + ) { + debug!("check_for_invalidation_at_exit({:?}): INVALID", place); + // FIXME: should be talking about the region lifetime instead + // of just a span here. + let span = self.infcx.tcx.sess.source_map().end_point(span); + self.report_borrowed_value_does_not_live_long_enough( + location, + borrow, + (place, span), + None, + ) + } + } + + /// Reports an error if this is a borrow of local data. + /// This is called for all Yield expressions on movable generators + fn check_for_local_borrow(&mut self, borrow: &BorrowData<'tcx>, yield_span: Span) { + debug!("check_for_local_borrow({:?})", borrow); + + if borrow_of_local_data(borrow.borrowed_place) { + let err = self.cannot_borrow_across_generator_yield( + self.retrieve_borrow_spans(borrow).var_or_use(), + yield_span, + ); + + self.buffer_error(err); + } + } + + fn check_activations(&mut self, location: Location, span: Span, flow_state: &Flows<'cx, 'tcx>) { + // Two-phase borrow support: For each activation that is newly + // generated at this statement, check if it interferes with + // another borrow. + let borrow_set = self.borrow_set.clone(); + for &borrow_index in borrow_set.activations_at_location(location) { + let borrow = &borrow_set[borrow_index]; + + // only mutable borrows should be 2-phase + assert!(match borrow.kind { + BorrowKind::Shared | BorrowKind::Shallow => false, + BorrowKind::Unique | BorrowKind::Mut { .. } => true, + }); + + self.access_place( + location, + (borrow.borrowed_place, span), + (Deep, Activation(WriteKind::MutableBorrow(borrow.kind), borrow_index)), + LocalMutationIsAllowed::No, + flow_state, + ); + // We do not need to call `check_if_path_or_subpath_is_moved` + // again, as we already called it when we made the + // initial reservation. + } + } + + fn check_if_reassignment_to_immutable_state( + &mut self, + location: Location, + local: Local, + place_span: (Place<'tcx>, Span), + flow_state: &Flows<'cx, 'tcx>, + ) { + debug!("check_if_reassignment_to_immutable_state({:?})", local); + + // Check if any of the initializations of `local` have happened yet: + if let Some(init_index) = self.is_local_ever_initialized(local, flow_state) { + // And, if so, report an error. + let init = &self.move_data.inits[init_index]; + let span = init.span(&self.body); + self.report_illegal_reassignment(location, place_span, span, place_span.0); + } + } + + fn check_if_full_path_is_moved( + &mut self, + location: Location, + desired_action: InitializationRequiringAction, + place_span: (PlaceRef<'tcx>, Span), + flow_state: &Flows<'cx, 'tcx>, + ) { + let maybe_uninits = &flow_state.uninits; + + // Bad scenarios: + // + // 1. Move of `a.b.c`, use of `a.b.c` + // 2. Move of `a.b.c`, use of `a.b.c.d` (without first reinitializing `a.b.c.d`) + // 3. Uninitialized `(a.b.c: &_)`, use of `*a.b.c`; note that with + // partial initialization support, one might have `a.x` + // initialized but not `a.b`. + // + // OK scenarios: + // + // 4. Move of `a.b.c`, use of `a.b.d` + // 5. Uninitialized `a.x`, initialized `a.b`, use of `a.b` + // 6. Copied `(a.b: &_)`, use of `*(a.b).c`; note that `a.b` + // must have been initialized for the use to be sound. + // 7. Move of `a.b.c` then reinit of `a.b.c.d`, use of `a.b.c.d` + + // The dataflow tracks shallow prefixes distinctly (that is, + // field-accesses on P distinctly from P itself), in order to + // track substructure initialization separately from the whole + // structure. + // + // E.g., when looking at (*a.b.c).d, if the closest prefix for + // which we have a MovePath is `a.b`, then that means that the + // initialization state of `a.b` is all we need to inspect to + // know if `a.b.c` is valid (and from that we infer that the + // dereference and `.d` access is also valid, since we assume + // `a.b.c` is assigned a reference to an initialized and + // well-formed record structure.) + + // Therefore, if we seek out the *closest* prefix for which we + // have a MovePath, that should capture the initialization + // state for the place scenario. + // + // This code covers scenarios 1, 2, and 3. + + debug!("check_if_full_path_is_moved place: {:?}", place_span.0); + let (prefix, mpi) = self.move_path_closest_to(place_span.0); + if maybe_uninits.contains(mpi) { + self.report_use_of_moved_or_uninitialized( + location, + desired_action, + (prefix, place_span.0, place_span.1), + mpi, + ); + } // Only query longest prefix with a MovePath, not further + // ancestors; dataflow recurs on children when parents + // move (to support partial (re)inits). + // + // (I.e., querying parents breaks scenario 7; but may want + // to do such a query based on partial-init feature-gate.) + } + + /// Subslices correspond to multiple move paths, so we iterate through the + /// elements of the base array. For each element we check + /// + /// * Does this element overlap with our slice. + /// * Is any part of it uninitialized. + fn check_if_subslice_element_is_moved( + &mut self, + location: Location, + desired_action: InitializationRequiringAction, + place_span: (PlaceRef<'tcx>, Span), + maybe_uninits: &ChunkedBitSet<MovePathIndex>, + from: u64, + to: u64, + ) { + if let Some(mpi) = self.move_path_for_place(place_span.0) { + let move_paths = &self.move_data.move_paths; + + let root_path = &move_paths[mpi]; + for (child_mpi, child_move_path) in root_path.children(move_paths) { + let last_proj = child_move_path.place.projection.last().unwrap(); + if let ProjectionElem::ConstantIndex { offset, from_end, .. } = last_proj { + debug_assert!(!from_end, "Array constant indexing shouldn't be `from_end`."); + + if (from..to).contains(offset) { + let uninit_child = + self.move_data.find_in_move_path_or_its_descendants(child_mpi, |mpi| { + maybe_uninits.contains(mpi) + }); + + if let Some(uninit_child) = uninit_child { + self.report_use_of_moved_or_uninitialized( + location, + desired_action, + (place_span.0, place_span.0, place_span.1), + uninit_child, + ); + return; // don't bother finding other problems. + } + } + } + } + } + } + + fn check_if_path_or_subpath_is_moved( + &mut self, + location: Location, + desired_action: InitializationRequiringAction, + place_span: (PlaceRef<'tcx>, Span), + flow_state: &Flows<'cx, 'tcx>, + ) { + let maybe_uninits = &flow_state.uninits; + + // Bad scenarios: + // + // 1. Move of `a.b.c`, use of `a` or `a.b` + // partial initialization support, one might have `a.x` + // initialized but not `a.b`. + // 2. All bad scenarios from `check_if_full_path_is_moved` + // + // OK scenarios: + // + // 3. Move of `a.b.c`, use of `a.b.d` + // 4. Uninitialized `a.x`, initialized `a.b`, use of `a.b` + // 5. Copied `(a.b: &_)`, use of `*(a.b).c`; note that `a.b` + // must have been initialized for the use to be sound. + // 6. Move of `a.b.c` then reinit of `a.b.c.d`, use of `a.b.c.d` + + self.check_if_full_path_is_moved(location, desired_action, place_span, flow_state); + + if let Some((place_base, ProjectionElem::Subslice { from, to, from_end: false })) = + place_span.0.last_projection() + { + let place_ty = place_base.ty(self.body(), self.infcx.tcx); + if let ty::Array(..) = place_ty.ty.kind() { + self.check_if_subslice_element_is_moved( + location, + desired_action, + (place_base, place_span.1), + maybe_uninits, + from, + to, + ); + return; + } + } + + // A move of any shallow suffix of `place` also interferes + // with an attempt to use `place`. This is scenario 3 above. + // + // (Distinct from handling of scenarios 1+2+4 above because + // `place` does not interfere with suffixes of its prefixes, + // e.g., `a.b.c` does not interfere with `a.b.d`) + // + // This code covers scenario 1. + + debug!("check_if_path_or_subpath_is_moved place: {:?}", place_span.0); + if let Some(mpi) = self.move_path_for_place(place_span.0) { + let uninit_mpi = self + .move_data + .find_in_move_path_or_its_descendants(mpi, |mpi| maybe_uninits.contains(mpi)); + + if let Some(uninit_mpi) = uninit_mpi { + self.report_use_of_moved_or_uninitialized( + location, + desired_action, + (place_span.0, place_span.0, place_span.1), + uninit_mpi, + ); + return; // don't bother finding other problems. + } + } + } + + /// Currently MoveData does not store entries for all places in + /// the input MIR. For example it will currently filter out + /// places that are Copy; thus we do not track places of shared + /// reference type. This routine will walk up a place along its + /// prefixes, searching for a foundational place that *is* + /// tracked in the MoveData. + /// + /// An Err result includes a tag indicated why the search failed. + /// Currently this can only occur if the place is built off of a + /// static variable, as we do not track those in the MoveData. + fn move_path_closest_to(&mut self, place: PlaceRef<'tcx>) -> (PlaceRef<'tcx>, MovePathIndex) { + match self.move_data.rev_lookup.find(place) { + LookupResult::Parent(Some(mpi)) | LookupResult::Exact(mpi) => { + (self.move_data.move_paths[mpi].place.as_ref(), mpi) + } + LookupResult::Parent(None) => panic!("should have move path for every Local"), + } + } + + fn move_path_for_place(&mut self, place: PlaceRef<'tcx>) -> Option<MovePathIndex> { + // If returns None, then there is no move path corresponding + // to a direct owner of `place` (which means there is nothing + // that borrowck tracks for its analysis). + + match self.move_data.rev_lookup.find(place) { + LookupResult::Parent(_) => None, + LookupResult::Exact(mpi) => Some(mpi), + } + } + + fn check_if_assigned_path_is_moved( + &mut self, + location: Location, + (place, span): (Place<'tcx>, Span), + flow_state: &Flows<'cx, 'tcx>, + ) { + debug!("check_if_assigned_path_is_moved place: {:?}", place); + + // None case => assigning to `x` does not require `x` be initialized. + for (place_base, elem) in place.iter_projections().rev() { + match elem { + ProjectionElem::Index(_/*operand*/) | + ProjectionElem::ConstantIndex { .. } | + // assigning to P[i] requires P to be valid. + ProjectionElem::Downcast(_/*adt_def*/, _/*variant_idx*/) => + // assigning to (P->variant) is okay if assigning to `P` is okay + // + // FIXME: is this true even if P is an adt with a dtor? + { } + + // assigning to (*P) requires P to be initialized + ProjectionElem::Deref => { + self.check_if_full_path_is_moved( + location, InitializationRequiringAction::Use, + (place_base, span), flow_state); + // (base initialized; no need to + // recur further) + break; + } + + ProjectionElem::Subslice { .. } => { + panic!("we don't allow assignments to subslices, location: {:?}", + location); + } + + ProjectionElem::Field(..) => { + // if type of `P` has a dtor, then + // assigning to `P.f` requires `P` itself + // be already initialized + let tcx = self.infcx.tcx; + let base_ty = place_base.ty(self.body(), tcx).ty; + match base_ty.kind() { + ty::Adt(def, _) if def.has_dtor(tcx) => { + self.check_if_path_or_subpath_is_moved( + location, InitializationRequiringAction::Assignment, + (place_base, span), flow_state); + + // (base initialized; no need to + // recur further) + break; + } + + // Once `let s; s.x = V; read(s.x);`, + // is allowed, remove this match arm. + ty::Adt(..) | ty::Tuple(..) => { + check_parent_of_field(self, location, place_base, span, flow_state); + + // rust-lang/rust#21232, #54499, #54986: during period where we reject + // partial initialization, do not complain about unnecessary `mut` on + // an attempt to do a partial initialization. + self.used_mut.insert(place.local); + } + + _ => {} + } + } + } + } + + fn check_parent_of_field<'cx, 'tcx>( + this: &mut MirBorrowckCtxt<'cx, 'tcx>, + location: Location, + base: PlaceRef<'tcx>, + span: Span, + flow_state: &Flows<'cx, 'tcx>, + ) { + // rust-lang/rust#21232: Until Rust allows reads from the + // initialized parts of partially initialized structs, we + // will, starting with the 2018 edition, reject attempts + // to write to structs that are not fully initialized. + // + // In other words, *until* we allow this: + // + // 1. `let mut s; s.x = Val; read(s.x);` + // + // we will for now disallow this: + // + // 2. `let mut s; s.x = Val;` + // + // and also this: + // + // 3. `let mut s = ...; drop(s); s.x=Val;` + // + // This does not use check_if_path_or_subpath_is_moved, + // because we want to *allow* reinitializations of fields: + // e.g., want to allow + // + // `let mut s = ...; drop(s.x); s.x=Val;` + // + // This does not use check_if_full_path_is_moved on + // `base`, because that would report an error about the + // `base` as a whole, but in this scenario we *really* + // want to report an error about the actual thing that was + // moved, which may be some prefix of `base`. + + // Shallow so that we'll stop at any dereference; we'll + // report errors about issues with such bases elsewhere. + let maybe_uninits = &flow_state.uninits; + + // Find the shortest uninitialized prefix you can reach + // without going over a Deref. + let mut shortest_uninit_seen = None; + for prefix in this.prefixes(base, PrefixSet::Shallow) { + let Some(mpi) = this.move_path_for_place(prefix) else { continue }; + + if maybe_uninits.contains(mpi) { + debug!( + "check_parent_of_field updating shortest_uninit_seen from {:?} to {:?}", + shortest_uninit_seen, + Some((prefix, mpi)) + ); + shortest_uninit_seen = Some((prefix, mpi)); + } else { + debug!("check_parent_of_field {:?} is definitely initialized", (prefix, mpi)); + } + } + + if let Some((prefix, mpi)) = shortest_uninit_seen { + // Check for a reassignment into an uninitialized field of a union (for example, + // after a move out). In this case, do not report an error here. There is an + // exception, if this is the first assignment into the union (that is, there is + // no move out from an earlier location) then this is an attempt at initialization + // of the union - we should error in that case. + let tcx = this.infcx.tcx; + if base.ty(this.body(), tcx).ty.is_union() { + if this.move_data.path_map[mpi].iter().any(|moi| { + this.move_data.moves[*moi].source.is_predecessor_of(location, this.body) + }) { + return; + } + } + + this.report_use_of_moved_or_uninitialized( + location, + InitializationRequiringAction::PartialAssignment, + (prefix, base, span), + mpi, + ); + } + } + } + + /// Checks the permissions for the given place and read or write kind + /// + /// Returns `true` if an error is reported. + fn check_access_permissions( + &mut self, + (place, span): (Place<'tcx>, Span), + kind: ReadOrWrite, + is_local_mutation_allowed: LocalMutationIsAllowed, + flow_state: &Flows<'cx, 'tcx>, + location: Location, + ) -> bool { + debug!( + "check_access_permissions({:?}, {:?}, is_local_mutation_allowed: {:?})", + place, kind, is_local_mutation_allowed + ); + + let error_access; + let the_place_err; + + match kind { + Reservation(WriteKind::MutableBorrow( + borrow_kind @ (BorrowKind::Unique | BorrowKind::Mut { .. }), + )) + | Write(WriteKind::MutableBorrow( + borrow_kind @ (BorrowKind::Unique | BorrowKind::Mut { .. }), + )) => { + let is_local_mutation_allowed = match borrow_kind { + BorrowKind::Unique => LocalMutationIsAllowed::Yes, + BorrowKind::Mut { .. } => is_local_mutation_allowed, + BorrowKind::Shared | BorrowKind::Shallow => unreachable!(), + }; + match self.is_mutable(place.as_ref(), is_local_mutation_allowed) { + Ok(root_place) => { + self.add_used_mut(root_place, flow_state); + return false; + } + Err(place_err) => { + error_access = AccessKind::MutableBorrow; + the_place_err = place_err; + } + } + } + Reservation(WriteKind::Mutate) | Write(WriteKind::Mutate) => { + match self.is_mutable(place.as_ref(), is_local_mutation_allowed) { + Ok(root_place) => { + self.add_used_mut(root_place, flow_state); + return false; + } + Err(place_err) => { + error_access = AccessKind::Mutate; + the_place_err = place_err; + } + } + } + + Reservation( + WriteKind::Move + | WriteKind::StorageDeadOrDrop + | WriteKind::MutableBorrow(BorrowKind::Shared) + | WriteKind::MutableBorrow(BorrowKind::Shallow), + ) + | Write( + WriteKind::Move + | WriteKind::StorageDeadOrDrop + | WriteKind::MutableBorrow(BorrowKind::Shared) + | WriteKind::MutableBorrow(BorrowKind::Shallow), + ) => { + if self.is_mutable(place.as_ref(), is_local_mutation_allowed).is_err() + && !self.has_buffered_errors() + { + // rust-lang/rust#46908: In pure NLL mode this code path should be + // unreachable, but we use `delay_span_bug` because we can hit this when + // dereferencing a non-Copy raw pointer *and* have `-Ztreat-err-as-bug` + // enabled. We don't want to ICE for that case, as other errors will have + // been emitted (#52262). + self.infcx.tcx.sess.delay_span_bug( + span, + &format!( + "Accessing `{:?}` with the kind `{:?}` shouldn't be possible", + place, kind, + ), + ); + } + return false; + } + Activation(..) => { + // permission checks are done at Reservation point. + return false; + } + Read( + ReadKind::Borrow( + BorrowKind::Unique + | BorrowKind::Mut { .. } + | BorrowKind::Shared + | BorrowKind::Shallow, + ) + | ReadKind::Copy, + ) => { + // Access authorized + return false; + } + } + + // rust-lang/rust#21232, #54986: during period where we reject + // partial initialization, do not complain about mutability + // errors except for actual mutation (as opposed to an attempt + // to do a partial initialization). + let previously_initialized = + self.is_local_ever_initialized(place.local, flow_state).is_some(); + + // at this point, we have set up the error reporting state. + if previously_initialized { + self.report_mutability_error(place, span, the_place_err, error_access, location); + true + } else { + false + } + } + + fn is_local_ever_initialized( + &self, + local: Local, + flow_state: &Flows<'cx, 'tcx>, + ) -> Option<InitIndex> { + let mpi = self.move_data.rev_lookup.find_local(local); + let ii = &self.move_data.init_path_map[mpi]; + for &index in ii { + if flow_state.ever_inits.contains(index) { + return Some(index); + } + } + None + } + + /// Adds the place into the used mutable variables set + fn add_used_mut(&mut self, root_place: RootPlace<'tcx>, flow_state: &Flows<'cx, 'tcx>) { + match root_place { + RootPlace { place_local: local, place_projection: [], is_local_mutation_allowed } => { + // If the local may have been initialized, and it is now currently being + // mutated, then it is justified to be annotated with the `mut` + // keyword, since the mutation may be a possible reassignment. + if is_local_mutation_allowed != LocalMutationIsAllowed::Yes + && self.is_local_ever_initialized(local, flow_state).is_some() + { + self.used_mut.insert(local); + } + } + RootPlace { + place_local: _, + place_projection: _, + is_local_mutation_allowed: LocalMutationIsAllowed::Yes, + } => {} + RootPlace { + place_local, + place_projection: place_projection @ [.., _], + is_local_mutation_allowed: _, + } => { + if let Some(field) = self.is_upvar_field_projection(PlaceRef { + local: place_local, + projection: place_projection, + }) { + self.used_mut_upvars.push(field); + } + } + } + } + + /// Whether this value can be written or borrowed mutably. + /// Returns the root place if the place passed in is a projection. + fn is_mutable( + &self, + place: PlaceRef<'tcx>, + is_local_mutation_allowed: LocalMutationIsAllowed, + ) -> Result<RootPlace<'tcx>, PlaceRef<'tcx>> { + debug!("is_mutable: place={:?}, is_local...={:?}", place, is_local_mutation_allowed); + match place.last_projection() { + None => { + let local = &self.body.local_decls[place.local]; + match local.mutability { + Mutability::Not => match is_local_mutation_allowed { + LocalMutationIsAllowed::Yes => Ok(RootPlace { + place_local: place.local, + place_projection: place.projection, + is_local_mutation_allowed: LocalMutationIsAllowed::Yes, + }), + LocalMutationIsAllowed::ExceptUpvars => Ok(RootPlace { + place_local: place.local, + place_projection: place.projection, + is_local_mutation_allowed: LocalMutationIsAllowed::ExceptUpvars, + }), + LocalMutationIsAllowed::No => Err(place), + }, + Mutability::Mut => Ok(RootPlace { + place_local: place.local, + place_projection: place.projection, + is_local_mutation_allowed, + }), + } + } + Some((place_base, elem)) => { + match elem { + ProjectionElem::Deref => { + let base_ty = place_base.ty(self.body(), self.infcx.tcx).ty; + + // Check the kind of deref to decide + match base_ty.kind() { + ty::Ref(_, _, mutbl) => { + match mutbl { + // Shared borrowed data is never mutable + hir::Mutability::Not => Err(place), + // Mutably borrowed data is mutable, but only if we have a + // unique path to the `&mut` + hir::Mutability::Mut => { + let mode = match self.is_upvar_field_projection(place) { + Some(field) if self.upvars[field.index()].by_ref => { + is_local_mutation_allowed + } + _ => LocalMutationIsAllowed::Yes, + }; + + self.is_mutable(place_base, mode) + } + } + } + ty::RawPtr(tnm) => { + match tnm.mutbl { + // `*const` raw pointers are not mutable + hir::Mutability::Not => Err(place), + // `*mut` raw pointers are always mutable, regardless of + // context. The users have to check by themselves. + hir::Mutability::Mut => Ok(RootPlace { + place_local: place.local, + place_projection: place.projection, + is_local_mutation_allowed, + }), + } + } + // `Box<T>` owns its content, so mutable if its location is mutable + _ if base_ty.is_box() => { + self.is_mutable(place_base, is_local_mutation_allowed) + } + // Deref should only be for reference, pointers or boxes + _ => bug!("Deref of unexpected type: {:?}", base_ty), + } + } + // All other projections are owned by their base path, so mutable if + // base path is mutable + ProjectionElem::Field(..) + | ProjectionElem::Index(..) + | ProjectionElem::ConstantIndex { .. } + | ProjectionElem::Subslice { .. } + | ProjectionElem::Downcast(..) => { + let upvar_field_projection = self.is_upvar_field_projection(place); + if let Some(field) = upvar_field_projection { + let upvar = &self.upvars[field.index()]; + debug!( + "is_mutable: upvar.mutability={:?} local_mutation_is_allowed={:?} \ + place={:?}, place_base={:?}", + upvar, is_local_mutation_allowed, place, place_base + ); + match (upvar.place.mutability, is_local_mutation_allowed) { + ( + Mutability::Not, + LocalMutationIsAllowed::No + | LocalMutationIsAllowed::ExceptUpvars, + ) => Err(place), + (Mutability::Not, LocalMutationIsAllowed::Yes) + | (Mutability::Mut, _) => { + // Subtle: this is an upvar + // reference, so it looks like + // `self.foo` -- we want to double + // check that the location `*self` + // is mutable (i.e., this is not a + // `Fn` closure). But if that + // check succeeds, we want to + // *blame* the mutability on + // `place` (that is, + // `self.foo`). This is used to + // propagate the info about + // whether mutability declarations + // are used outwards, so that we register + // the outer variable as mutable. Otherwise a + // test like this fails to record the `mut` + // as needed: + // + // ``` + // fn foo<F: FnOnce()>(_f: F) { } + // fn main() { + // let var = Vec::new(); + // foo(move || { + // var.push(1); + // }); + // } + // ``` + let _ = + self.is_mutable(place_base, is_local_mutation_allowed)?; + Ok(RootPlace { + place_local: place.local, + place_projection: place.projection, + is_local_mutation_allowed, + }) + } + } + } else { + self.is_mutable(place_base, is_local_mutation_allowed) + } + } + } + } + } + } + + /// If `place` is a field projection, and the field is being projected from a closure type, + /// then returns the index of the field being projected. Note that this closure will always + /// be `self` in the current MIR, because that is the only time we directly access the fields + /// of a closure type. + fn is_upvar_field_projection(&self, place_ref: PlaceRef<'tcx>) -> Option<Field> { + path_utils::is_upvar_field_projection(self.infcx.tcx, &self.upvars, place_ref, self.body()) + } +} + +mod error { + use rustc_errors::ErrorGuaranteed; + + use super::*; + + pub struct BorrowckErrors<'tcx> { + /// This field keeps track of move errors that are to be reported for given move indices. + /// + /// There are situations where many errors can be reported for a single move out (see #53807) + /// and we want only the best of those errors. + /// + /// The `report_use_of_moved_or_uninitialized` function checks this map and replaces the + /// diagnostic (if there is one) if the `Place` of the error being reported is a prefix of the + /// `Place` of the previous most diagnostic. This happens instead of buffering the error. Once + /// all move errors have been reported, any diagnostics in this map are added to the buffer + /// to be emitted. + /// + /// `BTreeMap` is used to preserve the order of insertions when iterating. This is necessary + /// when errors in the map are being re-added to the error buffer so that errors with the + /// same primary span come out in a consistent order. + buffered_move_errors: + BTreeMap<Vec<MoveOutIndex>, (PlaceRef<'tcx>, DiagnosticBuilder<'tcx, ErrorGuaranteed>)>, + /// Diagnostics to be reported buffer. + buffered: Vec<Diagnostic>, + /// Set to Some if we emit an error during borrowck + tainted_by_errors: Option<ErrorGuaranteed>, + } + + impl BorrowckErrors<'_> { + pub fn new() -> Self { + BorrowckErrors { + buffered_move_errors: BTreeMap::new(), + buffered: Default::default(), + tainted_by_errors: None, + } + } + + // FIXME(eddyb) this is a suboptimal API because `tainted_by_errors` is + // set before any emission actually happens (weakening the guarantee). + pub fn buffer_error(&mut self, t: DiagnosticBuilder<'_, ErrorGuaranteed>) { + self.tainted_by_errors = Some(ErrorGuaranteed::unchecked_claim_error_was_emitted()); + t.buffer(&mut self.buffered); + } + + pub fn buffer_non_error_diag(&mut self, t: DiagnosticBuilder<'_, ()>) { + t.buffer(&mut self.buffered); + } + + pub fn set_tainted_by_errors(&mut self) { + self.tainted_by_errors = Some(ErrorGuaranteed::unchecked_claim_error_was_emitted()); + } + } + + impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> { + pub fn buffer_error(&mut self, t: DiagnosticBuilder<'_, ErrorGuaranteed>) { + self.errors.buffer_error(t); + } + + pub fn buffer_non_error_diag(&mut self, t: DiagnosticBuilder<'_, ()>) { + self.errors.buffer_non_error_diag(t); + } + + pub fn buffer_move_error( + &mut self, + move_out_indices: Vec<MoveOutIndex>, + place_and_err: (PlaceRef<'tcx>, DiagnosticBuilder<'tcx, ErrorGuaranteed>), + ) -> bool { + if let Some((_, diag)) = + self.errors.buffered_move_errors.insert(move_out_indices, place_and_err) + { + // Cancel the old diagnostic so we don't ICE + diag.cancel(); + false + } else { + true + } + } + + pub fn emit_errors(&mut self) -> Option<ErrorGuaranteed> { + // Buffer any move errors that we collected and de-duplicated. + for (_, (_, diag)) in std::mem::take(&mut self.errors.buffered_move_errors) { + // We have already set tainted for this error, so just buffer it. + diag.buffer(&mut self.errors.buffered); + } + + if !self.errors.buffered.is_empty() { + self.errors.buffered.sort_by_key(|diag| diag.sort_span); + + for mut diag in self.errors.buffered.drain(..) { + self.infcx.tcx.sess.diagnostic().emit_diagnostic(&mut diag); + } + } + + self.errors.tainted_by_errors + } + + pub fn has_buffered_errors(&self) -> bool { + self.errors.buffered.is_empty() + } + + pub fn has_move_error( + &self, + move_out_indices: &[MoveOutIndex], + ) -> Option<&(PlaceRef<'tcx>, DiagnosticBuilder<'cx, ErrorGuaranteed>)> { + self.errors.buffered_move_errors.get(move_out_indices) + } + } +} + +/// The degree of overlap between 2 places for borrow-checking. +enum Overlap { + /// The places might partially overlap - in this case, we give + /// up and say that they might conflict. This occurs when + /// different fields of a union are borrowed. For example, + /// if `u` is a union, we have no way of telling how disjoint + /// `u.a.x` and `a.b.y` are. + Arbitrary, + /// The places have the same type, and are either completely disjoint + /// or equal - i.e., they can't "partially" overlap as can occur with + /// unions. This is the "base case" on which we recur for extensions + /// of the place. + EqualOrDisjoint, + /// The places are disjoint, so we know all extensions of them + /// will also be disjoint. + Disjoint, +} |