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d6077f895a
Use associated type bounds in some places in the compiler Use associated type bounds for some nested `impl Trait<Assoc = impl Trait2>` cases. I'm generally keen to introduce new lang features that are more mature into the compiler, but maybe let's see what others think? Side-note: I was surprised that the only use-cases of nested impl trait in the compiler are just iterator related?!
2470 lines
98 KiB
Rust
2470 lines
98 KiB
Rust
//! This query borrow-checks the MIR to (further) ensure it is not broken.
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#![allow(rustc::potential_query_instability)]
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#![feature(associated_type_bounds)]
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#![feature(box_patterns)]
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#![feature(let_chains)]
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#![feature(min_specialization)]
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#![feature(never_type)]
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#![feature(once_cell)]
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#![feature(rustc_attrs)]
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#![feature(stmt_expr_attributes)]
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#![feature(trusted_step)]
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#![feature(try_blocks)]
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#![recursion_limit = "256"]
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#[macro_use]
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extern crate rustc_middle;
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#[macro_use]
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extern crate tracing;
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use rustc_data_structures::fx::{FxHashMap, FxHashSet};
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use rustc_data_structures::graph::dominators::Dominators;
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use rustc_data_structures::vec_map::VecMap;
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use rustc_errors::{Diagnostic, DiagnosticBuilder, DiagnosticMessage, SubdiagnosticMessage};
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use rustc_hir as hir;
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use rustc_hir::def_id::LocalDefId;
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use rustc_index::bit_set::ChunkedBitSet;
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use rustc_index::vec::IndexVec;
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use rustc_infer::infer::{
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DefiningAnchor, InferCtxt, NllRegionVariableOrigin, RegionVariableOrigin, TyCtxtInferExt,
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};
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use rustc_macros::fluent_messages;
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use rustc_middle::mir::{
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traversal, Body, ClearCrossCrate, Local, Location, Mutability, NonDivergingIntrinsic, Operand,
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Place, PlaceElem, PlaceRef, VarDebugInfoContents,
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};
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use rustc_middle::mir::{AggregateKind, BasicBlock, BorrowCheckResult, BorrowKind};
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use rustc_middle::mir::{Field, ProjectionElem, Promoted, Rvalue, Statement, StatementKind};
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use rustc_middle::mir::{InlineAsmOperand, Terminator, TerminatorKind};
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use rustc_middle::ty::query::Providers;
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use rustc_middle::ty::{self, CapturedPlace, ParamEnv, RegionVid, TyCtxt};
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use rustc_session::lint::builtin::UNUSED_MUT;
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use rustc_span::{Span, Symbol};
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use either::Either;
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use smallvec::SmallVec;
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use std::cell::OnceCell;
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use std::cell::RefCell;
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use std::collections::BTreeMap;
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use std::ops::Deref;
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use std::rc::Rc;
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use rustc_mir_dataflow::impls::{
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EverInitializedPlaces, MaybeInitializedPlaces, MaybeUninitializedPlaces,
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};
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use rustc_mir_dataflow::move_paths::{InitIndex, MoveOutIndex, MovePathIndex};
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use rustc_mir_dataflow::move_paths::{InitLocation, LookupResult, MoveData, MoveError};
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use rustc_mir_dataflow::Analysis;
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use rustc_mir_dataflow::MoveDataParamEnv;
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use crate::session_diagnostics::VarNeedNotMut;
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use self::diagnostics::{AccessKind, RegionName};
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use self::location::LocationTable;
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use self::prefixes::PrefixSet;
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use facts::AllFacts;
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use self::path_utils::*;
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pub mod borrow_set;
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mod borrowck_errors;
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mod constraint_generation;
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mod constraints;
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mod dataflow;
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mod def_use;
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mod diagnostics;
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mod facts;
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mod invalidation;
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mod location;
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mod member_constraints;
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mod nll;
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mod path_utils;
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mod place_ext;
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mod places_conflict;
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mod prefixes;
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mod region_infer;
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mod renumber;
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mod session_diagnostics;
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mod type_check;
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mod universal_regions;
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mod used_muts;
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/// A public API provided for the Rust compiler consumers.
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pub mod consumers;
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use borrow_set::{BorrowData, BorrowSet};
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use dataflow::{BorrowIndex, BorrowckFlowState as Flows, BorrowckResults, Borrows};
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use nll::{PoloniusOutput, ToRegionVid};
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use place_ext::PlaceExt;
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use places_conflict::{places_conflict, PlaceConflictBias};
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use region_infer::RegionInferenceContext;
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use renumber::RegionCtxt;
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fluent_messages! { "../locales/en-US.ftl" }
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// FIXME(eddyb) perhaps move this somewhere more centrally.
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#[derive(Debug)]
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struct Upvar<'tcx> {
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place: CapturedPlace<'tcx>,
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/// If true, the capture is behind a reference.
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by_ref: bool,
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}
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/// Associate some local constants with the `'tcx` lifetime
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struct TyCtxtConsts<'tcx>(TyCtxt<'tcx>);
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impl<'tcx> TyCtxtConsts<'tcx> {
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const DEREF_PROJECTION: &'tcx [PlaceElem<'tcx>; 1] = &[ProjectionElem::Deref];
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}
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pub fn provide(providers: &mut Providers) {
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*providers = Providers {
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mir_borrowck: |tcx, did| {
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if let Some(def) = ty::WithOptConstParam::try_lookup(did, tcx) {
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tcx.mir_borrowck_const_arg(def)
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} else {
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mir_borrowck(tcx, ty::WithOptConstParam::unknown(did))
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}
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},
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mir_borrowck_const_arg: |tcx, (did, param_did)| {
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mir_borrowck(tcx, ty::WithOptConstParam { did, const_param_did: Some(param_did) })
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},
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..*providers
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};
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}
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fn mir_borrowck(tcx: TyCtxt<'_>, def: ty::WithOptConstParam<LocalDefId>) -> &BorrowCheckResult<'_> {
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let (input_body, promoted) = tcx.mir_promoted(def);
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debug!("run query mir_borrowck: {}", tcx.def_path_str(def.did.to_def_id()));
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if input_body.borrow().should_skip() {
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debug!("Skipping borrowck because of injected body");
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// Let's make up a borrowck result! Fun times!
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let result = BorrowCheckResult {
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concrete_opaque_types: VecMap::new(),
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closure_requirements: None,
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used_mut_upvars: SmallVec::new(),
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tainted_by_errors: None,
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};
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return tcx.arena.alloc(result);
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}
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let hir_owner = tcx.hir().local_def_id_to_hir_id(def.did).owner;
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let infcx =
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tcx.infer_ctxt().with_opaque_type_inference(DefiningAnchor::Bind(hir_owner.def_id)).build();
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let input_body: &Body<'_> = &input_body.borrow();
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let promoted: &IndexVec<_, _> = &promoted.borrow();
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let opt_closure_req = do_mir_borrowck(&infcx, input_body, promoted, false).0;
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debug!("mir_borrowck done");
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tcx.arena.alloc(opt_closure_req)
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}
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/// Perform the actual borrow checking.
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///
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/// If `return_body_with_facts` is true, then return the body with non-erased
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/// region ids on which the borrow checking was performed together with Polonius
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/// facts.
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#[instrument(skip(infcx, input_body, input_promoted), fields(id=?input_body.source.with_opt_param().as_local().unwrap()), level = "debug")]
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fn do_mir_borrowck<'tcx>(
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infcx: &InferCtxt<'tcx>,
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input_body: &Body<'tcx>,
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input_promoted: &IndexVec<Promoted, Body<'tcx>>,
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return_body_with_facts: bool,
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) -> (BorrowCheckResult<'tcx>, Option<Box<BodyWithBorrowckFacts<'tcx>>>) {
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let def = input_body.source.with_opt_param().as_local().unwrap();
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debug!(?def);
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let tcx = infcx.tcx;
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let infcx = BorrowckInferCtxt::new(infcx);
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let param_env = tcx.param_env(def.did);
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let mut local_names = IndexVec::from_elem(None, &input_body.local_decls);
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for var_debug_info in &input_body.var_debug_info {
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if let VarDebugInfoContents::Place(place) = var_debug_info.value {
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if let Some(local) = place.as_local() {
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if let Some(prev_name) = local_names[local] && var_debug_info.name != prev_name {
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span_bug!(
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var_debug_info.source_info.span,
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"local {:?} has many names (`{}` vs `{}`)",
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local,
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prev_name,
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var_debug_info.name
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);
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}
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local_names[local] = Some(var_debug_info.name);
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}
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}
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}
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let mut errors = error::BorrowckErrors::new(infcx.tcx);
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// Gather the upvars of a closure, if any.
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let tables = tcx.typeck_opt_const_arg(def);
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if let Some(e) = tables.tainted_by_errors {
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infcx.set_tainted_by_errors(e);
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errors.set_tainted_by_errors(e);
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}
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let upvars: Vec<_> = tables
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.closure_min_captures_flattened(def.did)
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.map(|captured_place| {
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let capture = captured_place.info.capture_kind;
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let by_ref = match capture {
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ty::UpvarCapture::ByValue => false,
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ty::UpvarCapture::ByRef(..) => true,
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};
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Upvar { place: captured_place.clone(), by_ref }
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})
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.collect();
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// Replace all regions with fresh inference variables. This
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// requires first making our own copy of the MIR. This copy will
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// be modified (in place) to contain non-lexical lifetimes. It
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// will have a lifetime tied to the inference context.
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let mut body_owned = input_body.clone();
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let mut promoted = input_promoted.clone();
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let free_regions =
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nll::replace_regions_in_mir(&infcx, param_env, &mut body_owned, &mut promoted);
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let body = &body_owned; // no further changes
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let location_table_owned = LocationTable::new(body);
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let location_table = &location_table_owned;
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let (move_data, move_errors): (MoveData<'tcx>, Vec<(Place<'tcx>, MoveError<'tcx>)>) =
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match MoveData::gather_moves(&body, tcx, param_env) {
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Ok((_, move_data)) => (move_data, Vec::new()),
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Err((move_data, move_errors)) => (move_data, move_errors),
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};
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let promoted_errors = promoted
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.iter_enumerated()
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.map(|(idx, body)| (idx, MoveData::gather_moves(&body, tcx, param_env)));
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let mdpe = MoveDataParamEnv { move_data, param_env };
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let mut flow_inits = MaybeInitializedPlaces::new(tcx, &body, &mdpe)
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.into_engine(tcx, &body)
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.pass_name("borrowck")
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.iterate_to_fixpoint()
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.into_results_cursor(&body);
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let locals_are_invalidated_at_exit = tcx.hir().body_owner_kind(def.did).is_fn_or_closure();
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let borrow_set =
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Rc::new(BorrowSet::build(tcx, body, locals_are_invalidated_at_exit, &mdpe.move_data));
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let use_polonius = return_body_with_facts || infcx.tcx.sess.opts.unstable_opts.polonius;
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// Compute non-lexical lifetimes.
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let nll::NllOutput {
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regioncx,
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opaque_type_values,
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polonius_input,
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polonius_output,
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opt_closure_req,
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nll_errors,
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} = nll::compute_regions(
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&infcx,
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free_regions,
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body,
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&promoted,
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location_table,
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param_env,
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&mut flow_inits,
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&mdpe.move_data,
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&borrow_set,
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&upvars,
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use_polonius,
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);
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// Dump MIR results into a file, if that is enabled. This let us
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// write unit-tests, as well as helping with debugging.
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nll::dump_mir_results(&infcx, &body, ®ioncx, &opt_closure_req);
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// We also have a `#[rustc_regions]` annotation that causes us to dump
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// information.
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nll::dump_annotation(
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&infcx,
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&body,
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®ioncx,
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&opt_closure_req,
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&opaque_type_values,
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&mut errors,
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);
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// The various `flow_*` structures can be large. We drop `flow_inits` here
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// so it doesn't overlap with the others below. This reduces peak memory
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// usage significantly on some benchmarks.
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drop(flow_inits);
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let regioncx = Rc::new(regioncx);
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let flow_borrows = Borrows::new(tcx, body, ®ioncx, &borrow_set)
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.into_engine(tcx, body)
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.pass_name("borrowck")
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.iterate_to_fixpoint();
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let flow_uninits = MaybeUninitializedPlaces::new(tcx, body, &mdpe)
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.into_engine(tcx, body)
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.pass_name("borrowck")
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.iterate_to_fixpoint();
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let flow_ever_inits = EverInitializedPlaces::new(tcx, body, &mdpe)
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.into_engine(tcx, body)
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.pass_name("borrowck")
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.iterate_to_fixpoint();
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let movable_generator =
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// The first argument is the generator type passed by value
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if let Some(local) = body.local_decls.raw.get(1)
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// Get the interior types and substs which typeck computed
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&& let ty::Generator(_, _, hir::Movability::Static) = local.ty.kind()
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{
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false
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} else {
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true
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};
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for (idx, move_data_results) in promoted_errors {
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let promoted_body = &promoted[idx];
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if let Err((move_data, move_errors)) = move_data_results {
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let mut promoted_mbcx = MirBorrowckCtxt {
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infcx: &infcx,
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param_env,
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body: promoted_body,
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move_data: &move_data,
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location_table, // no need to create a real one for the promoted, it is not used
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movable_generator,
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fn_self_span_reported: Default::default(),
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locals_are_invalidated_at_exit,
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access_place_error_reported: Default::default(),
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reservation_error_reported: Default::default(),
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uninitialized_error_reported: Default::default(),
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regioncx: regioncx.clone(),
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used_mut: Default::default(),
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used_mut_upvars: SmallVec::new(),
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borrow_set: Rc::clone(&borrow_set),
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dominators: Default::default(),
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upvars: Vec::new(),
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local_names: IndexVec::from_elem(None, &promoted_body.local_decls),
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region_names: RefCell::default(),
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next_region_name: RefCell::new(1),
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polonius_output: None,
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errors,
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};
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promoted_mbcx.report_move_errors(move_errors);
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errors = promoted_mbcx.errors;
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};
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}
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let mut mbcx = MirBorrowckCtxt {
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infcx: &infcx,
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param_env,
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body,
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move_data: &mdpe.move_data,
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location_table,
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movable_generator,
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locals_are_invalidated_at_exit,
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fn_self_span_reported: Default::default(),
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access_place_error_reported: Default::default(),
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reservation_error_reported: Default::default(),
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uninitialized_error_reported: Default::default(),
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regioncx: Rc::clone(®ioncx),
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used_mut: Default::default(),
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used_mut_upvars: SmallVec::new(),
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borrow_set: Rc::clone(&borrow_set),
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dominators: Default::default(),
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upvars,
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local_names,
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region_names: RefCell::default(),
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next_region_name: RefCell::new(1),
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polonius_output,
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errors,
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};
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// Compute and report region errors, if any.
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mbcx.report_region_errors(nll_errors);
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let results = BorrowckResults {
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ever_inits: flow_ever_inits,
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uninits: flow_uninits,
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borrows: flow_borrows,
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};
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mbcx.report_move_errors(move_errors);
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rustc_mir_dataflow::visit_results(
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body,
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traversal::reverse_postorder(body).map(|(bb, _)| bb),
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&results,
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&mut mbcx,
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);
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// For each non-user used mutable variable, check if it's been assigned from
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// a user-declared local. If so, then put that local into the used_mut set.
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// Note that this set is expected to be small - only upvars from closures
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// would have a chance of erroneously adding non-user-defined mutable vars
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// to the set.
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let temporary_used_locals: FxHashSet<Local> = mbcx
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.used_mut
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.iter()
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.filter(|&local| !mbcx.body.local_decls[*local].is_user_variable())
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.cloned()
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.collect();
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// For the remaining unused locals that are marked as mutable, we avoid linting any that
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// were never initialized. These locals may have been removed as unreachable code; or will be
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// linted as unused variables.
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let unused_mut_locals =
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mbcx.body.mut_vars_iter().filter(|local| !mbcx.used_mut.contains(local)).collect();
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mbcx.gather_used_muts(temporary_used_locals, unused_mut_locals);
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debug!("mbcx.used_mut: {:?}", mbcx.used_mut);
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let used_mut = std::mem::take(&mut mbcx.used_mut);
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for local in mbcx.body.mut_vars_and_args_iter().filter(|local| !used_mut.contains(local)) {
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let local_decl = &mbcx.body.local_decls[local];
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let lint_root = match &mbcx.body.source_scopes[local_decl.source_info.scope].local_data {
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ClearCrossCrate::Set(data) => data.lint_root,
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_ => continue,
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};
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// Skip over locals that begin with an underscore or have no name
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match mbcx.local_names[local] {
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Some(name) => {
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if name.as_str().starts_with('_') {
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continue;
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}
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}
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None => continue,
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}
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let span = local_decl.source_info.span;
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if span.desugaring_kind().is_some() {
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// If the `mut` arises as part of a desugaring, we should ignore it.
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continue;
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}
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let mut_span = tcx.sess.source_map().span_until_non_whitespace(span);
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tcx.emit_spanned_lint(UNUSED_MUT, lint_root, span, VarNeedNotMut { span: mut_span })
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}
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let tainted_by_errors = mbcx.emit_errors();
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let result = BorrowCheckResult {
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concrete_opaque_types: opaque_type_values,
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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,
|
|
}
|
|
|
|
pub struct BorrowckInferCtxt<'cx, 'tcx> {
|
|
pub(crate) infcx: &'cx InferCtxt<'tcx>,
|
|
pub(crate) reg_var_to_origin: RefCell<FxHashMap<ty::RegionVid, RegionCtxt>>,
|
|
}
|
|
|
|
impl<'cx, 'tcx> BorrowckInferCtxt<'cx, 'tcx> {
|
|
pub(crate) fn new(infcx: &'cx InferCtxt<'tcx>) -> Self {
|
|
BorrowckInferCtxt { infcx, reg_var_to_origin: RefCell::new(Default::default()) }
|
|
}
|
|
|
|
pub(crate) fn next_region_var<F>(
|
|
&self,
|
|
origin: RegionVariableOrigin,
|
|
get_ctxt_fn: F,
|
|
) -> ty::Region<'tcx>
|
|
where
|
|
F: Fn() -> RegionCtxt,
|
|
{
|
|
let next_region = self.infcx.next_region_var(origin);
|
|
let vid = next_region
|
|
.as_var()
|
|
.unwrap_or_else(|| bug!("expected RegionKind::RegionVar on {:?}", next_region));
|
|
|
|
if cfg!(debug_assertions) {
|
|
debug!("inserting vid {:?} with origin {:?} into var_to_origin", vid, origin);
|
|
let ctxt = get_ctxt_fn();
|
|
let mut var_to_origin = self.reg_var_to_origin.borrow_mut();
|
|
let prev = var_to_origin.insert(vid, ctxt);
|
|
|
|
// This only makes sense if not called in a canonicalization context. If this
|
|
// ever changes we either want to get rid of `BorrowckInferContext::reg_var_to_origin`
|
|
// or modify how we track nll region vars for that map.
|
|
assert!(matches!(prev, None));
|
|
}
|
|
|
|
next_region
|
|
}
|
|
|
|
#[instrument(skip(self, get_ctxt_fn), level = "debug")]
|
|
pub(crate) fn next_nll_region_var<F>(
|
|
&self,
|
|
origin: NllRegionVariableOrigin,
|
|
get_ctxt_fn: F,
|
|
) -> ty::Region<'tcx>
|
|
where
|
|
F: Fn() -> RegionCtxt,
|
|
{
|
|
let next_region = self.infcx.next_nll_region_var(origin.clone());
|
|
let vid = next_region
|
|
.as_var()
|
|
.unwrap_or_else(|| bug!("expected RegionKind::RegionVar on {:?}", next_region));
|
|
|
|
if cfg!(debug_assertions) {
|
|
debug!("inserting vid {:?} with origin {:?} into var_to_origin", vid, origin);
|
|
let ctxt = get_ctxt_fn();
|
|
let mut var_to_origin = self.reg_var_to_origin.borrow_mut();
|
|
let prev = var_to_origin.insert(vid, ctxt);
|
|
|
|
// This only makes sense if not called in a canonicalization context. If this
|
|
// ever changes we either want to get rid of `BorrowckInferContext::reg_var_to_origin`
|
|
// or modify how we track nll region vars for that map.
|
|
assert!(matches!(prev, None));
|
|
}
|
|
|
|
next_region
|
|
}
|
|
}
|
|
|
|
impl<'cx, 'tcx> Deref for BorrowckInferCtxt<'cx, 'tcx> {
|
|
type Target = InferCtxt<'tcx>;
|
|
|
|
fn deref(&self) -> &'cx Self::Target {
|
|
self.infcx
|
|
}
|
|
}
|
|
|
|
struct MirBorrowckCtxt<'cx, 'tcx> {
|
|
infcx: &'cx BorrowckInferCtxt<'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: OnceCell<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, rhs)) => {
|
|
self.consume_rvalue(location, (rhs, span), flow_state);
|
|
|
|
self.mutate_place(location, (*lhs, span), Shallow(None), flow_state);
|
|
}
|
|
StatementKind::FakeRead(box (_, 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::Intrinsic(box kind) => match kind {
|
|
NonDivergingIntrinsic::Assume(op) => self.consume_operand(location, (op, span), flow_state),
|
|
NonDivergingIntrinsic::CopyNonOverlapping(..) => span_bug!(
|
|
span,
|
|
"Unexpected CopyNonOverlapping, should only appear after lower_intrinsics",
|
|
)
|
|
}
|
|
// Only relevant for mir typeck
|
|
StatementKind::AscribeUserType(..)
|
|
// Doesn't have any language semantics
|
|
| StatementKind::Coverage(..)
|
|
// These do not actually affect borrowck
|
|
| StatementKind::ConstEvalCounter
|
|
| StatementKind::StorageLive(..) => {}
|
|
StatementKind::StorageDead(local) => {
|
|
self.access_place(
|
|
location,
|
|
(Place::from(*local), span),
|
|
(Shallow(None), Write(WriteKind::StorageDeadOrDrop)),
|
|
LocalMutationIsAllowed::Yes,
|
|
flow_state,
|
|
);
|
|
}
|
|
StatementKind::Nop
|
|
| StatementKind::Retag { .. }
|
|
| 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 { discr, 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: 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 {
|
|
func,
|
|
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 { cond, expected: _, msg, target: _, cleanup: _ } => {
|
|
self.consume_operand(loc, (cond, span), flow_state);
|
|
use rustc_middle::mir::AssertKind;
|
|
if let AssertKind::BoundsCheck { len, index } = msg {
|
|
self.consume_operand(loc, (len, span), flow_state);
|
|
self.consume_operand(loc, (index, span), flow_state);
|
|
}
|
|
}
|
|
|
|
TerminatorKind::Yield { 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: _,
|
|
operands,
|
|
options: _,
|
|
line_spans: _,
|
|
destination: _,
|
|
cleanup: _,
|
|
} => {
|
|
for op in operands {
|
|
match op {
|
|
InlineAsmOperand::In { reg: _, 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: _, 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:
|
|
// - 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));
|
|
}
|
|
}
|
|
|
|
#[instrument(level = "debug", skip(self, flow_state))]
|
|
fn check_access_for_conflict(
|
|
&mut self,
|
|
location: Location,
|
|
place_span: (Place<'tcx>, Span),
|
|
sd: AccessDepth,
|
|
rw: ReadOrWrite,
|
|
flow_state: &Flows<'cx, 'tcx>,
|
|
) -> bool {
|
|
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);
|
|
|
|
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(operand)
|
|
| Rvalue::Repeat(operand, _)
|
|
| Rvalue::UnaryOp(_ /*un_op*/, operand)
|
|
| Rvalue::Cast(_ /*cast_kind*/, operand, _ /*ty*/)
|
|
| Rvalue::ShallowInitBox(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 (operand1, operand2))
|
|
| Rvalue::CheckedBinaryOp(_bin_op, box (operand1, 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(aggregate_kind, 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 def_id = def_id.expect_local();
|
|
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
|
|
#[instrument(level = "debug", skip(self))]
|
|
fn check_for_invalidation_at_exit(
|
|
&mut self,
|
|
location: Location,
|
|
borrow: &BorrowData<'tcx>,
|
|
span: Span,
|
|
) {
|
|
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_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::OpaqueCast(_) |
|
|
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);
|
|
|
|
// at this point, we have set up the error reporting state.
|
|
if let Some(init_index) = previously_initialized {
|
|
if let (AccessKind::Mutate, Some(_)) = (error_access, place.as_local()) {
|
|
// If this is a mutate access to an immutable local variable with no projections
|
|
// report the error as an illegal reassignment
|
|
let init = &self.move_data.inits[init_index];
|
|
let assigned_span = init.span(&self.body);
|
|
self.report_illegal_reassignment(location, (place, span), assigned_span, place);
|
|
} else {
|
|
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];
|
|
ii.into_iter().find(|&&index| flow_state.ever_inits.contains(index)).copied()
|
|
}
|
|
|
|
/// 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::OpaqueCast { .. }
|
|
| 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())
|
|
}
|
|
|
|
fn dominators(&self) -> &Dominators<BasicBlock> {
|
|
self.dominators.get_or_init(|| self.body.basic_blocks.dominators())
|
|
}
|
|
}
|
|
|
|
mod error {
|
|
use rustc_errors::ErrorGuaranteed;
|
|
|
|
use super::*;
|
|
|
|
pub struct BorrowckErrors<'tcx> {
|
|
tcx: TyCtxt<'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>)>,
|
|
buffered_mut_errors: FxHashMap<Span, (DiagnosticBuilder<'tcx, ErrorGuaranteed>, usize)>,
|
|
/// Diagnostics to be reported buffer.
|
|
buffered: Vec<Diagnostic>,
|
|
/// Set to Some if we emit an error during borrowck
|
|
tainted_by_errors: Option<ErrorGuaranteed>,
|
|
}
|
|
|
|
impl<'tcx> BorrowckErrors<'tcx> {
|
|
pub fn new(tcx: TyCtxt<'tcx>) -> Self {
|
|
BorrowckErrors {
|
|
tcx,
|
|
buffered_move_errors: BTreeMap::new(),
|
|
buffered_mut_errors: Default::default(),
|
|
buffered: Default::default(),
|
|
tainted_by_errors: None,
|
|
}
|
|
}
|
|
|
|
pub fn buffer_error(&mut self, t: DiagnosticBuilder<'_, ErrorGuaranteed>) {
|
|
if let None = self.tainted_by_errors {
|
|
self.tainted_by_errors = Some(
|
|
self.tcx
|
|
.sess
|
|
.delay_span_bug(t.span.clone(), "diagnostic buffered but not 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, e: ErrorGuaranteed) {
|
|
self.tainted_by_errors = Some(e);
|
|
}
|
|
}
|
|
|
|
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 get_buffered_mut_error(
|
|
&mut self,
|
|
span: Span,
|
|
) -> Option<(DiagnosticBuilder<'tcx, ErrorGuaranteed>, usize)> {
|
|
self.errors.buffered_mut_errors.remove(&span)
|
|
}
|
|
|
|
pub fn buffer_mut_error(
|
|
&mut self,
|
|
span: Span,
|
|
t: DiagnosticBuilder<'tcx, ErrorGuaranteed>,
|
|
count: usize,
|
|
) {
|
|
self.errors.buffered_mut_errors.insert(span, (t, count));
|
|
}
|
|
|
|
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);
|
|
}
|
|
for (_, (mut diag, count)) in std::mem::take(&mut self.errors.buffered_mut_errors) {
|
|
if count > 10 {
|
|
diag.note(&format!("...and {} other attempted mutable borrows", count - 10));
|
|
}
|
|
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,
|
|
}
|