diff options
4 files changed, 50 insertions, 31 deletions
diff --git a/src/librustc_mir/borrow_check/mod.rs b/src/librustc_mir/borrow_check/mod.rs index ccf7b75d878..b440cf87a24 100644 --- a/src/librustc_mir/borrow_check/mod.rs +++ b/src/librustc_mir/borrow_check/mod.rs @@ -1719,12 +1719,13 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> { } } - fn check_parent_of_field<'cx, 'gcx, 'tcx>(this: &mut MirBorrowckCtxt<'cx, 'gcx, 'tcx>, - context: Context, - base: &Place<'tcx>, - span: Span, - flow_state: &Flows<'cx, 'gcx, 'tcx>) - { + fn check_parent_of_field<'cx, 'gcx, 'tcx>( + this: &mut MirBorrowckCtxt<'cx, 'gcx, 'tcx>, + context: Context, + base: &Place<'tcx>, + span: Span, + flow_state: &Flows<'cx, 'gcx, '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 @@ -1776,6 +1777,22 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> { } if let Some((prefix, mpi)) = shortest_uninit_seen { + // Check for a reassignment into a uninitialized field of a union (for example, + // after a move out). In this case, do not report a 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 let ty::TyKind::Adt(def, _) = base.ty(this.mir, tcx).to_ty(tcx).sty { + let moved_before_this = this.move_data.path_map[mpi].iter().any(|moi| { + this.move_data.moves[*moi].source < context.loc + }); + + if def.is_union() && moved_before_this { + return; + } + } + this.report_use_of_moved_or_uninitialized( context, InitializationRequiringAction::PartialAssignment, diff --git a/src/librustc_mir/dataflow/move_paths/builder.rs b/src/librustc_mir/dataflow/move_paths/builder.rs index 6fb7d18a2bf..ba3da3aaa1a 100644 --- a/src/librustc_mir/dataflow/move_paths/builder.rs +++ b/src/librustc_mir/dataflow/move_paths/builder.rs @@ -430,6 +430,20 @@ impl<'b, 'a, 'gcx, 'tcx> Gatherer<'b, 'a, 'gcx, 'tcx> { fn gather_init(&mut self, place: &Place<'tcx>, kind: InitKind) { debug!("gather_init({:?}, {:?})", self.loc, place); + let place = match place { + // Check if we are assigning into a field of a union, if so, lookup the place + // of the union so it is marked as initialized again. + Place::Projection(box Projection { + base, + elem: ProjectionElem::Field(_, _), + }) if match base.ty(self.builder.mir, self.builder.tcx).to_ty(self.builder.tcx).sty { + ty::TyKind::Adt(def, _) if def.is_union() => true, + _ => false, + } => base, + // Otherwise, lookup the place. + _ => place, + }; + if let LookupResult::Exact(path) = self.builder.data.rev_lookup.find(place) { let init = self.builder.data.inits.push(Init { location: InitLocation::Statement(self.loc), diff --git a/src/test/ui/borrowck/borrowck-union-move-assign.nll.stderr b/src/test/ui/borrowck/borrowck-union-move-assign.nll.stderr index 423a44514db..a7125450e1c 100644 --- a/src/test/ui/borrowck/borrowck-union-move-assign.nll.stderr +++ b/src/test/ui/borrowck/borrowck-union-move-assign.nll.stderr @@ -8,28 +8,6 @@ LL | let a = u.a; //~ ERROR use of moved value: `u.a` | = note: move occurs because `u` has type `U`, which does not implement the `Copy` trait -error[E0382]: use of moved value: `u` - --> $DIR/borrowck-union-move-assign.rs:33:21 - | -LL | let a = u.a; - | --- value moved here -LL | u.a = A; -LL | let a = u.a; // OK - | ^^^ value used here after move - | - = note: move occurs because `u` has type `U`, which does not implement the `Copy` trait - -error[E0382]: use of moved value: `u` - --> $DIR/borrowck-union-move-assign.rs:39:21 - | -LL | let a = u.a; - | --- value moved here -LL | u.b = B; -LL | let a = u.a; // OK - | ^^^ value used here after move - | - = note: move occurs because `u` has type `U`, which does not implement the `Copy` trait - -error: aborting due to 3 previous errors +error: aborting due to previous error For more information about this error, try `rustc --explain E0382`. diff --git a/src/test/ui/borrowck/reassignment_immutable_fields_overlapping.nll.stderr b/src/test/ui/borrowck/reassignment_immutable_fields_overlapping.nll.stderr index 7da9dbfc088..fb1fe277740 100644 --- a/src/test/ui/borrowck/reassignment_immutable_fields_overlapping.nll.stderr +++ b/src/test/ui/borrowck/reassignment_immutable_fields_overlapping.nll.stderr @@ -4,6 +4,16 @@ error[E0381]: assign to part of possibly uninitialized variable: `x` LL | x.a = 1; //~ ERROR | ^^^^^^^ use of possibly uninitialized `x` -error: aborting due to previous error +error[E0594]: cannot assign to `x.b`, as `x` is not declared as mutable + --> $DIR/reassignment_immutable_fields_overlapping.rs:23:5 + | +LL | let x: Foo; + | - help: consider changing this to be mutable: `mut x` +LL | x.a = 1; //~ ERROR +LL | x.b = 22; //~ ERROR + | ^^^^^^^^ cannot assign + +error: aborting due to 2 previous errors -For more information about this error, try `rustc --explain E0381`. +Some errors occurred: E0381, E0594. +For more information about an error, try `rustc --explain E0381`. |