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Remove derived_from_illegal_borrow

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This commit is contained in:
Dylan MacKenzie 2019-11-26 11:53:10 -08:00
parent 5a10430f2c
commit 511740706c
1 changed files with 1 additions and 41 deletions
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42
src/librustc_mir/transform/check_consts/validation.rs
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@ -149,17 +149,6 @@ pub struct Validator<'a, 'mir, 'tcx> {
/// The span of the current statement.
span: Span,
/// True if the local was assigned the result of an illegal borrow (`ops::MutBorrow`).
///
/// This is used to hide errors from {re,}borrowing the newly-assigned local, instead pointing
/// the user to the place where the illegal borrow occurred. This set is only populated once an
/// error has been emitted, so it will never cause an erroneous `mir::Body` to pass validation.
///
/// FIXME(ecstaticmorse): assert at the end of checking that if `tcx.has_errors() == false`,
/// this set is empty. Note that if we start removing locals from
/// `derived_from_illegal_borrow`, just checking at the end won't be enough.
derived_from_illegal_borrow: BitSet<Local>,
}
impl Deref for Validator<'_, 'mir, 'tcx> {
@ -213,7 +202,6 @@ impl Validator<'a, 'mir, 'tcx> {
span: item.body.span,
item,
qualifs,
derived_from_illegal_borrow: BitSet::new_empty(item.body.local_decls.len()),
}
}
@ -406,35 +394,7 @@ impl Visitor<'tcx> for Validator<'_, 'mir, 'tcx> {
);
if borrowed_place_has_mut_interior {
let src_derived_from_illegal_borrow = borrowed_place
.as_local()
.map_or(false, |local| self.derived_from_illegal_borrow.contains(local));
// Don't emit errors for borrows of values that are *themselves* the result of
// an illegal borrow (e.g., the outermost `&` in `&&Cell::new(42)`). We want to
// point the user to the place where the original illegal borrow occurred, not
// to subsequent borrows of the resulting value.
let dest_derived_from_illegal_borrow = if !src_derived_from_illegal_borrow {
self.check_op(ops::MutBorrow(kind)) == CheckOpResult::Forbidden
} else {
true
};
// When the target of the assignment is a local with no projections, it will be
// marked as derived from an illegal borrow if necessary.
//
// FIXME: should we also clear `derived_from_illegal_borrow` when a local is
// assigned a new value?
if dest_derived_from_illegal_borrow {
let block = &self.body[location.block];
let statement = &block.statements[location.statement_index];
if let StatementKind::Assign(box (dest, _)) = &statement.kind {
if let Some(dest) = dest.as_local() {
self.derived_from_illegal_borrow.insert(dest);
}
}
}
self.check_op(ops::MutBorrow(kind));
}
}