Remove mutable_borrow_reservation_conflict lint

Author: jackh726

compiler/rustc_borrowck/src/borrow_set.rs

@@ -167,10 +167,6 @@ impl<'tcx> BorrowSet<'tcx> {
  crate fn get_index_of(&self, location: &Location) -> Option<BorrowIndex> {
  self.location_map.get_index_of(location).map(BorrowIndex::from)
  }
-
- crate fn contains(&self, location: &Location) -> bool {
- self.location_map.contains_key(location)
- }
 }
 
 struct GatherBorrows<'a, 'tcx> {

compiler/rustc_borrowck/src/lib.rs

@@ -35,14 +35,13 @@ use rustc_middle::mir::{Field, ProjectionElem, Promoted, Rvalue, Statement, Stat
 use rustc_middle::mir::{InlineAsmOperand, Terminator, TerminatorKind};
 use rustc_middle::ty::query::Providers;
 use rustc_middle::ty::{self, CapturedPlace, ParamEnv, RegionVid, TyCtxt};
-use rustc_session::lint::builtin::{MUTABLE_BORROW_RESERVATION_CONFLICT, UNUSED_MUT};
-use rustc_span::{Span, Symbol, DUMMY_SP};
+use rustc_session::lint::builtin::UNUSED_MUT;
+use rustc_span::{Span, Symbol};
 
 use either::Either;
 use smallvec::SmallVec;
 use std::cell::RefCell;
 use std::collections::BTreeMap;
-use std::mem;
 use std::rc::Rc;
 
 use rustc_mir_dataflow::impls::{
@@ -313,7 +312,6 @@ fn do_mir_borrowck<'a, 'tcx>(
  locals_are_invalidated_at_exit,
  access_place_error_reported: Default::default(),
  reservation_error_reported: Default::default(),
- reservation_warnings: Default::default(),
  uninitialized_error_reported: Default::default(),
  regioncx: regioncx.clone(),
  used_mut: Default::default(),
@@ -345,7 +343,6 @@ fn do_mir_borrowck<'a, 'tcx>(
  fn_self_span_reported: Default::default(),
  access_place_error_reported: Default::default(),
  reservation_error_reported: Default::default(),
- reservation_warnings: Default::default(),
  uninitialized_error_reported: Default::default(),
  regioncx: Rc::clone(&regioncx),
  used_mut: Default::default(),
@@ -378,34 +375,6 @@ fn do_mir_borrowck<'a, 'tcx>(
  &mut mbcx,
  );
 
- // Convert any reservation warnings into lints.
- let reservation_warnings = mem::take(&mut mbcx.reservation_warnings);
- for (_, (place, span, location, bk, borrow)) in reservation_warnings {
- let initial_diag = mbcx.report_conflicting_borrow(location, (place, span), bk, &borrow);
-
- let scope = mbcx.body.source_info(location).scope;
- let lint_root = match &mbcx.body.source_scopes[scope].local_data {
- ClearCrossCrate::Set(data) => data.lint_root,
- _ => tcx.hir().local_def_id_to_hir_id(def.did),
- };
-
- // Span and message don't matter; we overwrite them below anyway
- mbcx.infcx.tcx.struct_span_lint_hir(
- MUTABLE_BORROW_RESERVATION_CONFLICT,
- lint_root,
- DUMMY_SP,
- |lint| {
- let mut diag = lint.build("");
-
- diag.message = initial_diag.styled_message().clone();
- diag.span = initial_diag.span.clone();
-
- mbcx.buffer_non_error_diag(diag);
- },
- );
- initial_diag.cancel();
- }
-
  // For each non-user used mutable variable, check if it's been assigned from
  // a user-declared local. If so, then put that local into the used_mut set.
  // Note that this set is expected to be small - only upvars from closures
@@ -540,11 +509,6 @@ struct MirBorrowckCtxt<'cx, 'tcx> {
  /// used to report extra information for `FnSelfUse`, to avoid
  /// unnecessarily verbose errors.
  fn_self_span_reported: FxHashSet<Span>,
- /// Migration warnings to be reported for #56254. We delay reporting these
- /// so that we can suppress the warning if there's a corresponding error
- /// for the activation of the borrow.
- reservation_warnings:
- FxHashMap<BorrowIndex, (Place<'tcx>, Span, Location, BorrowKind, BorrowData<'tcx>)>,
  /// 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>>,
@@ -996,12 +960,6 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
  let conflict_error =
  self.check_access_for_conflict(location, place_span, sd, rw, flow_state);
 
- if let (Activation(_, borrow_idx), true) = (kind.1, conflict_error) {
- // Suppress this warning when there's an error being emitted for the
- // same borrow: fixing the error is likely to fix the warning.
- self.reservation_warnings.remove(&borrow_idx);
- }
-
  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));
@@ -1068,6 +1026,12 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
  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
@@ -1096,27 +1060,6 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
  Control::Break
  }
 
- (
- Reservation(WriteKind::MutableBorrow(bk)),
- BorrowKind::Shallow | BorrowKind::Shared,
- ) if { tcx.migrate_borrowck() && this.borrow_set.contains(&location) } => {
- let bi = this.borrow_set.get_index_of(&location).unwrap();
- debug!(
- "recording invalid reservation of place: {:?} with \
- borrow index {:?} as warning",
- place_span.0, bi,
- );
- // rust-lang/rust#56254 - This was previously permitted on
- // the 2018 edition so we emit it as a warning. We buffer
- // these separately so that we only emit a warning if borrow
- // checking was otherwise successful.
- this.reservation_warnings
- .insert(bi, (place_span.0, place_span.1, location, bk, borrow.clone()));
-
- // Don't suppress actual errors.
- Control::Continue
- }
-
  (Reservation(kind) | Activation(kind, _) | Write(kind), _) => {
  match rw {
  Reservation(..) => {

compiler/rustc_lint/src/lib.rs

@@ -491,6 +491,11 @@ fn register_builtins(store: &mut LintStore, no_interleave_lints: bool) {
  "converted into hard error, see RFC 2972 \
  <https://github.com/rust-lang/rfcs/blob/master/text/2972-constrained-naked.md> for more information",
  );
+ store.register_removed(
+ "mutable_borrow_reservation_conflict",
+ "now allowed, see issue #59159 \
+ <https://github.com/rust-lang/rust/issues/59159> for more information",
+ );
 }
 
 fn register_internals(store: &mut LintStore) {

compiler/rustc_lint_defs/src/builtin.rs

@@ -2345,40 +2345,6 @@ declare_lint! {
  };
 }
 
-declare_lint! {
- /// The `mutable_borrow_reservation_conflict` lint detects the reservation
- /// of a two-phased borrow that conflicts with other shared borrows.
- ///
- /// ### Example
- ///
- /// ```rust
- /// let mut v = vec![0, 1, 2];
- /// let shared = &v;
- /// v.push(shared.len());
- /// ```
- ///
- /// {{produces}}
- ///
- /// ### Explanation
- ///
- /// This is a [future-incompatible] lint to transition this to a hard error
- /// in the future. See [issue #59159] for a complete description of the
- /// problem, and some possible solutions.
- ///
- /// [issue #59159]: https://github.com/rust-lang/rust/issues/59159
- /// [future-incompatible]: ../index.md#future-incompatible-lints
- pub MUTABLE_BORROW_RESERVATION_CONFLICT,
- Warn,
- "reservation of a two-phased borrow conflicts with other shared borrows",
- @future_incompatible = FutureIncompatibleInfo {
- reason: FutureIncompatibilityReason::Custom(
- "this borrowing pattern was not meant to be accepted, \
- and may become a hard error in the future"
- ),
- reference: "issue #59159 <https://github.com/rust-lang/rust/issues/59159>",
- };
-}
-
 declare_lint! {
  /// The `soft_unstable` lint detects unstable features that were
  /// unintentionally allowed on stable.
@@ -3179,7 +3145,6 @@ declare_lint_pass! {
  META_VARIABLE_MISUSE,
  DEPRECATED_IN_FUTURE,
  AMBIGUOUS_ASSOCIATED_ITEMS,
- MUTABLE_BORROW_RESERVATION_CONFLICT,
  INDIRECT_STRUCTURAL_MATCH,
  POINTER_STRUCTURAL_MATCH,
  NONTRIVIAL_STRUCTURAL_MATCH,

src/test/ui/borrowck/suggest-local-var-imm-and-mut.nll.stderr

@@ -7,23 +7,12 @@ LL | self.foo(self.bar());
  | | | mutable borrow occurs here
  | | immutable borrow later used by call
  | immutable borrow occurs here
- |
-help: try adding a local storing this argument...
- --> $DIR/suggest-local-var-imm-and-mut.rs:12:22
- |
-LL | self.foo(self.bar());
- | ^^^^^^^^^^
-help: ...and then using that local as the argument to this call
- --> $DIR/suggest-local-var-imm-and-mut.rs:12:13
- |
-LL | self.foo(self.bar());
- | ^^^^^^^^^^^^^^^^^^^^
 
 error[E0502]: cannot borrow `*self` as mutable because it is also borrowed as immutable
- --> $DIR/suggest-local-var-imm-and-mut.rs:24:39
+ --> $DIR/suggest-local-var-imm-and-mut.rs:24:29
  |
 LL | Self::foo(self, Self::bar(self));
- | --------- ----  ^^^^ mutable borrow occurs here
+ | --------- ---- ^^^^^^^^^^^^^^^ mutable borrow occurs here
  | | |
  | | immutable borrow occurs here
  | immutable borrow later used by call

src/test/ui/borrowck/two-phase-cannot-nest-mut-self-calls.stderr

@@ -13,23 +13,6 @@ LL | |
 LL | | 0
 LL | | });
  | |______- immutable borrow occurs here
- |
-help: try adding a local storing this argument...
- --> $DIR/two-phase-cannot-nest-mut-self-calls.rs:16:9
- |
-LL | vec.push(2);
- | ^^^^^^^^^^^
-help: ...and then using that local as the argument to this call
- --> $DIR/two-phase-cannot-nest-mut-self-calls.rs:14:5
- |
-LL | / vec.get({
-LL | |
-LL | | vec.push(2);
-LL | |
-LL | |
-LL | | 0
-LL | | });
- | |______^
 
 error: aborting due to previous error
 

src/test/ui/borrowck/two-phase-reservation-sharing-interference-2.base.stderr

@@ -0,0 +1,25 @@
+error[E0502]: cannot borrow `v` as mutable because it is also borrowed as immutable
+ --> $DIR/two-phase-reservation-sharing-interference-2.rs:19:5
+ |
+LL | let shared = &v;
+ | -- immutable borrow occurs here
+LL | 
+LL | v.extend(shared);
+ | ^^------^^^^^^^^
+ | | |
+ | | immutable borrow later used by call
+ | mutable borrow occurs here
+
+error[E0502]: cannot borrow `v` as mutable because it is also borrowed as immutable
+ --> $DIR/two-phase-reservation-sharing-interference-2.rs:27:5
+ |
+LL | v.extend(&v);
+ | ^^------^--^
+ | | | |
+ | | | immutable borrow occurs here
+ | | immutable borrow later used by call
+ | mutable borrow occurs here
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0502`.

src/test/ui/borrowck/two-phase-reservation-sharing-interference-2.migrate2015.stderr

@@ -20,22 +20,6 @@ LL | v.extend(&v);
  | | immutable borrow later used by call
  | mutable borrow occurs here
 
-warning: cannot borrow `v` as mutable because it is also borrowed as immutable
- --> $DIR/two-phase-reservation-sharing-interference-2.rs:40:5
- |
-LL | let shared = &v;
- | -- immutable borrow occurs here
-LL | 
-LL | v.push(shared.len());
- | ^^^^^^^------------^
- | | |
- | | immutable borrow later used here
- | mutable borrow occurs here
- |
- = note: `#[warn(mutable_borrow_reservation_conflict)]` on by default
- = warning: this borrowing pattern was not meant to be accepted, and may become a hard error in the future
- = note: for more information, see issue #59159 <https://github.com/rust-lang/rust/issues/59159>
-
-error: aborting due to 2 previous errors; 1 warning emitted
+error: aborting due to 2 previous errors
 
 For more information about this error, try `rustc --explain E0502`.

src/test/ui/borrowck/two-phase-reservation-sharing-interference-2.migrate2018.stderr

@@ -20,22 +20,6 @@ LL | v.extend(&v);
  | | immutable borrow later used by call
  | mutable borrow occurs here
 
-warning: cannot borrow `v` as mutable because it is also borrowed as immutable
- --> $DIR/two-phase-reservation-sharing-interference-2.rs:40:5
- |
-LL | let shared = &v;
- | -- immutable borrow occurs here
-LL | 
-LL | v.push(shared.len());
- | ^^^^^^^------------^
- | | |
- | | immutable borrow later used here
- | mutable borrow occurs here
- |
- = note: `#[warn(mutable_borrow_reservation_conflict)]` on by default
- = warning: this borrowing pattern was not meant to be accepted, and may become a hard error in the future
- = note: for more information, see issue #59159 <https://github.com/rust-lang/rust/issues/59159>
-
-error: aborting due to 2 previous errors; 1 warning emitted
+error: aborting due to 2 previous errors
 
 For more information about this error, try `rustc --explain E0502`.

src/test/ui/borrowck/two-phase-reservation-sharing-interference-2.nll.stderr

@@ -0,0 +1,25 @@
+error[E0502]: cannot borrow `v` as mutable because it is also borrowed as immutable
+ --> $DIR/two-phase-reservation-sharing-interference-2.rs:19:5
+ |
+LL | let shared = &v;
+ | -- immutable borrow occurs here
+LL | 
+LL | v.extend(shared);
+ | ^^------^^^^^^^^
+ | | |
+ | | immutable borrow later used by call
+ | mutable borrow occurs here
+
+error[E0502]: cannot borrow `v` as mutable because it is also borrowed as immutable
+ --> $DIR/two-phase-reservation-sharing-interference-2.rs:27:5
+ |
+LL | v.extend(&v);
+ | ^^------^--^
+ | | | |
+ | | | immutable borrow occurs here
+ | | immutable borrow later used by call
+ | mutable borrow occurs here
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0502`.