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fix handling of immutable variables

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This commit is contained in:
Ariel Ben-Yehuda 2017-12-04 13:01:50 +02:00
parent 210f76816f
commit 82f3fc5dbc
1 changed files with 28 additions and 16 deletions
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44
src/librustc_mir/borrow_check/mod.rs
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@ -655,8 +655,9 @@ enum WriteKind {
/// - Take flow state into consideration in `is_assignable()` for local variables
#[derive(Copy, Clone, PartialEq, Eq, Debug)]
enum LocalMutationIsAllowed {
Move,
Yes,
No,
No
}
#[derive(Copy, Clone)]
@ -946,7 +947,7 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
context,
(place, span),
(Deep, Write(WriteKind::Move)),
LocalMutationIsAllowed::Yes,
LocalMutationIsAllowed::Move,
flow_state,
);
@ -1368,7 +1369,8 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
let local = &self.mir.local_decls[local];
match local.mutability {
Mutability::Not => match is_local_mutation_allowed {
LocalMutationIsAllowed::Yes => Ok(()),
LocalMutationIsAllowed::Yes |
LocalMutationIsAllowed::Move => Ok(()),
LocalMutationIsAllowed::No => Err(place),
},
Mutability::Mut => Ok(()),
@ -1393,10 +1395,14 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
// Mutably borrowed data is mutable, but only if we have a
// unique path to the `&mut`
hir::MutMutable => {
if self.is_upvar_field_projection(&proj.base).is_some() {
self.is_mutable(&proj.base, is_local_mutation_allowed)
} else {
self.is_unique(&proj.base)
match self.is_upvar_field_projection(&proj.base) {
Some(field) if {
self.mir.upvar_decls[field.index()].by_ref
} => {
self.is_mutable(&proj.base,
is_local_mutation_allowed)
}
_ => self.is_unique(&proj.base)
}
}
}
@ -1412,7 +1418,7 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
}
// `Box<T>` owns its content, so mutable if its location is mutable
_ if base_ty.is_box() => {
self.is_mutable(&proj.base, LocalMutationIsAllowed::No)
self.is_mutable(&proj.base, is_local_mutation_allowed)
}
// Deref should only be for reference, pointers or boxes
_ => bug!("Deref of unexpected type: {:?}", base_ty),
@ -1429,14 +1435,17 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
if let Some(field) = field_projection {
let decl = &self.mir.upvar_decls[field.index()];
return match decl.mutability {
Mutability::Mut => self.is_unique(&proj.base),
Mutability::Not => Err(place),
debug!("decl.mutability={:?} local_mutation_is_allowed={:?} place={:?}",
decl, is_local_mutation_allowed, place);
return match (decl.mutability, is_local_mutation_allowed) {
(Mutability::Not, LocalMutationIsAllowed::No) |
(Mutability::Not, LocalMutationIsAllowed::Yes) => Err(place),
(Mutability::Not, LocalMutationIsAllowed::Move) |
(Mutability::Mut, _) => self.is_unique(&proj.base),
};
}
self.is_mutable(&proj.base, LocalMutationIsAllowed::No)
self.is_mutable(&proj.base, is_local_mutation_allowed)
}
}
}
@ -1450,9 +1459,12 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
// Local variables are unique
Ok(())
}
Place::Static(..) => {
// Static variables are not
Err(place)
Place::Static(ref static_) => {
if !self.tcx.is_static_mut(static_.def_id) {
Err(place)
} else {
Ok(())
}
}
Place::Projection(ref proj) => {
match proj.elem {