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Make is_mutable use PlaceRef instead of it's fields #63203

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Aug 2, 2019
Merged

Make is_mutable use PlaceRef instead of it's fields #63203

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133 changes: 71 additions & 62 deletions src/librustc_mir/borrow_check/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1942,7 +1942,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
BorrowKind::Mut { .. } => is_local_mutation_allowed,
BorrowKind::Shared | BorrowKind::Shallow => unreachable!(),
};
match self.is_mutable(&place.base, &place.projection, is_local_mutation_allowed) {
match self.is_mutable(place.as_ref(), is_local_mutation_allowed) {
Ok(root_place) => {
self.add_used_mut(root_place, flow_state);
return false;
Expand All @@ -1954,7 +1954,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
}
}
Reservation(WriteKind::Mutate) | Write(WriteKind::Mutate) => {
match self.is_mutable(&place.base, &place.projection, is_local_mutation_allowed) {
match self.is_mutable(place.as_ref(), is_local_mutation_allowed) {
Ok(root_place) => {
self.add_used_mut(root_place, flow_state);
return false;
Expand All @@ -1974,8 +1974,8 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
| Write(wk @ WriteKind::StorageDeadOrDrop)
| Write(wk @ WriteKind::MutableBorrow(BorrowKind::Shared))
| Write(wk @ WriteKind::MutableBorrow(BorrowKind::Shallow)) => {
if let (Err(_place_err), true) = (
self.is_mutable(&place.base, &place.projection, is_local_mutation_allowed),
if let (Err(place_err), true) = (
self.is_mutable(place.as_ref(), is_local_mutation_allowed),
self.errors_buffer.is_empty()
) {
if self.infcx.tcx.migrate_borrowck() {
Expand All @@ -1996,10 +1996,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
self.report_mutability_error(
place,
span,
PlaceRef {
base: _place_err.0,
projection: _place_err.1,
},
place_err,
error_access,
location,
);
Expand Down Expand Up @@ -2033,10 +2030,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
self.report_mutability_error(
place,
span,
PlaceRef {
base: the_place_err.0,
projection: the_place_err.1,
},
the_place_err,
error_access,
location,
);
Expand Down Expand Up @@ -2107,78 +2101,86 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
/// Returns the root place if the place passed in is a projection.
fn is_mutable<'d>(
&self,
place_base: &'d PlaceBase<'tcx>,
place_projection: &'d Option<Box<Projection<'tcx>>>,
place: PlaceRef<'d, 'tcx>,
is_local_mutation_allowed: LocalMutationIsAllowed,
) -> Result<RootPlace<'d, 'tcx>, (&'d PlaceBase<'tcx>, &'d Option<Box<Projection<'tcx>>>)> {
match (place_base, place_projection) {
(PlaceBase::Local(local), None) => {
) -> Result<RootPlace<'d, 'tcx>, PlaceRef<'d, 'tcx>> {
match place {
PlaceRef {
base: PlaceBase::Local(local),
projection: None,
} => {
let local = &self.body.local_decls[*local];
match local.mutability {
Mutability::Not => match is_local_mutation_allowed {
LocalMutationIsAllowed::Yes => Ok(RootPlace {
place_base,
place_projection,
place_base: place.base,
place_projection: place.projection,
is_local_mutation_allowed: LocalMutationIsAllowed::Yes,
}),
LocalMutationIsAllowed::ExceptUpvars => Ok(RootPlace {
place_base,
place_projection,
place_base: place.base,
place_projection: place.projection,
is_local_mutation_allowed: LocalMutationIsAllowed::ExceptUpvars,
}),
LocalMutationIsAllowed::No => Err((place_base, place_projection)),
LocalMutationIsAllowed::No => Err(place),
},
Mutability::Mut => Ok(RootPlace {
place_base,
place_projection,
place_base: place.base,
place_projection: place.projection,
is_local_mutation_allowed,
}),
}
}
// The rules for promotion are made by `qualify_consts`, there wouldn't even be a
// `Place::Promoted` if the promotion weren't 100% legal. So we just forward this
(PlaceBase::Static(box Static {
kind: StaticKind::Promoted(_),
..
}), None) =>
PlaceRef {
base: PlaceBase::Static(box Static {
kind: StaticKind::Promoted(_),
..
}),
projection: None,
} =>
Ok(RootPlace {
place_base,
place_projection,
place_base: place.base,
place_projection: place.projection,
is_local_mutation_allowed,
}),
(PlaceBase::Static(box Static {
kind: StaticKind::Static(def_id),
..
}), None) => {
PlaceRef {
base: PlaceBase::Static(box Static {
kind: StaticKind::Static(def_id),
..
}),
projection: None,
} => {
if !self.infcx.tcx.is_mutable_static(*def_id) {
Err((place_base, place_projection))
Err(place)
} else {
Ok(RootPlace {
place_base,
place_projection,
place_base: place.base,
place_projection: place.projection,
is_local_mutation_allowed,
})
}
}
(_, Some(ref proj)) => {
PlaceRef {
base: _,
projection: Some(proj),
} => {
match proj.elem {
ProjectionElem::Deref => {
let base_ty =
Place::ty_from(place_base, &proj.base, self.body, self.infcx.tcx).ty;
Place::ty_from(place.base, &proj.base, self.body, self.infcx.tcx).ty;

// Check the kind of deref to decide
match base_ty.sty {
ty::Ref(_, _, mutbl) => {
match mutbl {
// Shared borrowed data is never mutable
hir::MutImmutable => Err((place_base, place_projection)),
hir::MutImmutable => Err(place),
// Mutably borrowed data is mutable, but only if we have a
// unique path to the `&mut`
hir::MutMutable => {
let mode = match self.is_upvar_field_projection(PlaceRef {
base: &place_base,
projection: &place_projection,
}) {
let mode = match self.is_upvar_field_projection(place) {
Some(field)
if self.upvars[field.index()].by_ref =>
{
Expand All @@ -2187,28 +2189,34 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
_ => LocalMutationIsAllowed::Yes,
};

self.is_mutable(place_base, &proj.base, mode)
self.is_mutable(PlaceRef {
base: place.base,
projection: &proj.base,
}, mode)
}
}
}
ty::RawPtr(tnm) => {
match tnm.mutbl {
// `*const` raw pointers are not mutable
hir::MutImmutable => Err((place_base, place_projection)),
hir::MutImmutable => Err(place),
// `*mut` raw pointers are always mutable, regardless of
// context. The users have to check by themselves.
hir::MutMutable => {
Ok(RootPlace {
place_base,
place_projection,
place_base: place.base,
place_projection: place.projection,
is_local_mutation_allowed,
})
}
}
}
// `Box<T>` owns its content, so mutable if its location is mutable
_ if base_ty.is_box() => {
self.is_mutable(place_base, &proj.base, is_local_mutation_allowed)
self.is_mutable(PlaceRef {
base: place.base,
projection: &proj.base,
}, is_local_mutation_allowed)
}
// Deref should only be for reference, pointers or boxes
_ => bug!("Deref of unexpected type: {:?}", base_ty),
Expand All @@ -2221,21 +2229,18 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
| ProjectionElem::ConstantIndex { .. }
| ProjectionElem::Subslice { .. }
| ProjectionElem::Downcast(..) => {
let upvar_field_projection = self.is_upvar_field_projection(PlaceRef {
base: &place_base,
projection: &place_projection,
});
let upvar_field_projection = self.is_upvar_field_projection(place);
if let Some(field) = upvar_field_projection {
let upvar = &self.upvars[field.index()];
debug!(
"upvar.mutability={:?} local_mutation_is_allowed={:?} \
place={:?} {:?}",
upvar, is_local_mutation_allowed, place_base, place_projection
place={:?}",
upvar, is_local_mutation_allowed, place
);
match (upvar.mutability, is_local_mutation_allowed) {
(Mutability::Not, LocalMutationIsAllowed::No)
| (Mutability::Not, LocalMutationIsAllowed::ExceptUpvars) => {
Err((place_base, place_projection))
Err(place)
}
(Mutability::Not, LocalMutationIsAllowed::Yes)
| (Mutability::Mut, _) => {
Expand Down Expand Up @@ -2265,18 +2270,22 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
// });
// }
// ```
let _ = self.is_mutable(place_base,
&proj.base,
is_local_mutation_allowed)?;
let _ = self.is_mutable(PlaceRef {
base: place.base,
projection: &proj.base,
}, is_local_mutation_allowed)?;
Ok(RootPlace {
place_base,
place_projection,
place_base: place.base,
place_projection: place.projection,
is_local_mutation_allowed,
})
}
}
} else {
self.is_mutable(place_base, &proj.base, is_local_mutation_allowed)
self.is_mutable(PlaceRef {
base: place.base,
projection: &proj.base,
}, is_local_mutation_allowed)
}
}
}
Expand Down