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Remove special case for zero-sized arrays from indirectly mut locals

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This commit is contained in:
Dylan MacKenzie 2019-10-13 12:27:45 -07:00
parent 061b906683
commit 8fd16baa57
1 changed files with 4 additions and 13 deletions
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17
src/librustc_mir/dataflow/impls/indirect_mutation.rs
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@ -104,25 +104,16 @@ impl<'tcx> TransferFunction<'_, '_, 'tcx> {
kind: mir::BorrowKind,
borrowed_place: &mir::Place<'tcx>,
) -> bool {
let borrowed_ty = borrowed_place.ty(self.body, self.tcx).ty;
// Zero-sized types cannot be mutated, since there is nothing inside to mutate.
//
// FIXME: For now, we only exempt arrays of length zero. We need to carefully
// consider the effects before extending this to all ZSTs.
if let ty::Array(_, len) = borrowed_ty.kind {
if len.try_eval_usize(self.tcx, self.param_env) == Some(0) {
return false;
}
}
match kind {
mir::BorrowKind::Mut { .. } => true,
| mir::BorrowKind::Shared
| mir::BorrowKind::Shallow
| mir::BorrowKind::Unique
=> !borrowed_ty.is_freeze(self.tcx, self.param_env, DUMMY_SP),
=> !borrowed_place
.ty(self.body, self.tcx)
.ty
.is_freeze(self.tcx, self.param_env, DUMMY_SP),
}
}
}