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Use while let slice_pattern instead of carrying an index around #64518

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Merged
merged 1 commit into from
Sep 17, 2019
Merged

Use while let slice_pattern instead of carrying an index around #64518

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10 changes: 6 additions & 4 deletions src/librustc_mir/borrow_check/conflict_errors.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -614,8 +614,9 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
projection,
} = first_borrowed_place;

for (i, elem) in projection.iter().enumerate().rev() {
let proj_base = &projection[..i];
let mut cursor = &**projection;
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Can we refactor this idiom into a method on projection to reduce the repetition?

while let [proj_base @ .., elem] = cursor {
cursor = proj_base;

match elem {
ProjectionElem::Field(field, _) if union_ty(base, proj_base).is_some() => {
Expand All @@ -637,8 +638,9 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
projection,
} = second_borrowed_place;

for (i, elem) in projection.iter().enumerate().rev() {
let proj_base = &projection[..i];
let mut cursor = &**projection;
while let [proj_base @ .., elem] = cursor {
cursor = proj_base;

if let ProjectionElem::Field(field, _) = elem {
if let Some(union_ty) = union_ty(base, proj_base) {
Expand Down
8 changes: 4 additions & 4 deletions src/librustc_mir/borrow_check/mod.rs
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Expand Up @@ -1758,7 +1758,10 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
debug!("check_if_assigned_path_is_moved place: {:?}", place);

// None case => assigning to `x` does not require `x` be initialized.
for (i, elem) in place.projection.iter().enumerate().rev() {
let mut cursor = &*place.projection;
while let [proj_base @ .., elem] = cursor {
cursor = proj_base;

match elem {
ProjectionElem::Index(_/*operand*/) |
ProjectionElem::ConstantIndex { .. } |
Expand All @@ -1771,8 +1774,6 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {

// assigning to (*P) requires P to be initialized
ProjectionElem::Deref => {
let proj_base = &place.projection[..i];

self.check_if_full_path_is_moved(
location, InitializationRequiringAction::Use,
(PlaceRef {
Expand All @@ -1790,7 +1791,6 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
}

ProjectionElem::Field(..) => {
let proj_base = &place.projection[..i];
// if type of `P` has a dtor, then
// assigning to `P.f` requires `P` itself
// be already initialized
Expand Down
7 changes: 5 additions & 2 deletions src/librustc_mir/borrow_check/nll/type_check/mod.rs
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Expand Up @@ -2417,9 +2417,12 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
"add_reborrow_constraint({:?}, {:?}, {:?})",
location, borrow_region, borrowed_place
);
for (i, elem) in borrowed_place.projection.iter().enumerate().rev() {

let mut cursor = &*borrowed_place.projection;
while let [proj_base @ .., elem] = cursor {
cursor = proj_base;

debug!("add_reborrow_constraint - iteration {:?}", elem);
let proj_base = &borrowed_place.projection[..i];

match elem {
ProjectionElem::Deref => {
Expand Down
5 changes: 3 additions & 2 deletions src/librustc_mir/build/matches/mod.rs
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Expand Up @@ -1296,8 +1296,9 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
// Insert a Shallow borrow of the prefixes of any fake borrows.
for place in fake_borrows
{
for (i, elem) in place.projection.iter().enumerate().rev() {
let proj_base = &place.projection[..i];
let mut cursor = &*place.projection;
while let [proj_base @ .., elem] = cursor {
cursor = proj_base;

if let ProjectionElem::Deref = elem {
// Insert a shallow borrow after a deref. For other
Expand Down
5 changes: 3 additions & 2 deletions src/librustc_mir/transform/check_unsafety.rs
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Expand Up @@ -407,8 +407,9 @@ impl<'a, 'tcx> UnsafetyChecker<'a, 'tcx> {
place: &Place<'tcx>,
is_mut_use: bool,
) {
for (i, elem) in place.projection.iter().enumerate().rev() {
let proj_base = &place.projection[..i];
let mut cursor = &*place.projection;
while let [proj_base @ .., elem] = cursor {
cursor = proj_base;

match elem {
ProjectionElem::Field(..) => {
Expand Down
5 changes: 3 additions & 2 deletions src/librustc_mir/util/alignment.rs
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Expand Up @@ -38,8 +38,9 @@ fn is_within_packed<'tcx, L>(tcx: TyCtxt<'tcx>, local_decls: &L, place: &Place<'
where
L: HasLocalDecls<'tcx>,
{
for (i, elem) in place.projection.iter().enumerate().rev() {
let proj_base = &place.projection[..i];
let mut cursor = &*place.projection;
while let [proj_base @ .., elem] = cursor {
cursor = proj_base;

match elem {
// encountered a Deref, which is ABI-aligned
Expand Down