true
}
- fn is_local_variable_or_arg(&self, cmt: mc::cmt<'tcx>) -> bool {
- match cmt.cat {
- mc::cat_local(_) => true,
- _ => false
- }
- }
-
fn consume_common(&self,
id: ast::NodeId,
span: Span,
mode: euv::MutateMode) {
debug!("check_assignment(assignee_cmt={:?})", assignee_cmt);
- // Mutable values can be assigned, as long as they obey loans
- // and aliasing restrictions:
- if assignee_cmt.mutbl.is_mutable() {
- if check_for_aliasable_mutable_writes(self, assignment_span, assignee_cmt.clone()) {
- if mode != euv::Init {
- check_for_assignment_to_borrowed_path(
- self, assignment_id, assignment_span, assignee_cmt.clone());
- mark_variable_as_used_mut(self, assignee_cmt);
- }
- }
-
- return;
- }
-
- // Initializations are OK if and only if they aren't partial
- // reinitialization of a partially-uninitialized structure.
+ // Initializations never cause borrow errors as they only
+ // affect a fresh local.
if mode == euv::Init {
return
}
- // For immutable local variables, assignments are legal
- // if they cannot already have been assigned
- if self.is_local_variable_or_arg(assignee_cmt.clone()) {
- assert!(assignee_cmt.mutbl.is_immutable()); // no "const" locals
- let lp = opt_loan_path(&assignee_cmt).unwrap();
- self.move_data.each_assignment_of(assignment_id, &lp, |assign| {
- self.bccx.report_reassigned_immutable_variable(
- assignment_span,
- &*lp,
- assign);
+ // Check that we don't invalidate any outstanding loans
+ if let Some(loan_path) = opt_loan_path(&assignee_cmt) {
+ let scope = region::CodeExtent::from_node_id(assignment_id);
+ self.each_in_scope_loan_affecting_path(scope, &*loan_path, |loan| {
+ self.report_illegal_mutation(assignment_span, &*loan_path, loan);
false
});
- return;
- }
-
- // Otherwise, just a plain error.
- match assignee_cmt.note {
- mc::NoteClosureEnv(upvar_id) => {
- // If this is an `Fn` closure, it simply can't mutate upvars.
- // If it's an `FnMut` closure, the original variable was declared immutable.
- // We need to determine which is the case here.
- let kind = match assignee_cmt.upvar().unwrap().cat {
- mc::cat_upvar(mc::Upvar { kind, .. }) => kind,
- _ => unreachable!()
- };
- if kind == ty::FnClosureKind {
- self.bccx.span_err(
- assignment_span,
- &format!("cannot assign to {}",
- self.bccx.cmt_to_string(&*assignee_cmt)));
- self.bccx.span_help(
- self.tcx().map.span(upvar_id.closure_expr_id),
- "consider changing this closure to take self by mutable reference");
- } else {
- self.bccx.span_err(
- assignment_span,
- &format!("cannot assign to {} {}",
- assignee_cmt.mutbl.to_user_str(),
- self.bccx.cmt_to_string(&*assignee_cmt)));
- }
- }
- _ => match opt_loan_path(&assignee_cmt) {
- Some(lp) => {
- self.bccx.span_err(
- assignment_span,
- &format!("cannot assign to {} {} `{}`",
- assignee_cmt.mutbl.to_user_str(),
- self.bccx.cmt_to_string(&*assignee_cmt),
- self.bccx.loan_path_to_string(&*lp)));
- }
- None => {
- self.bccx.span_err(
- assignment_span,
- &format!("cannot assign to {} {}",
- assignee_cmt.mutbl.to_user_str(),
- self.bccx.cmt_to_string(&*assignee_cmt)));
- }
- }
- }
- return;
-
- fn mark_variable_as_used_mut<'a, 'tcx>(this: &CheckLoanCtxt<'a, 'tcx>,
- mut cmt: mc::cmt<'tcx>) {
- //! If the mutability of the `cmt` being written is inherited
- //! from a local variable, liveness will
- //! not have been able to detect that this variable's mutability
- //! is important, so we must add the variable to the
- //! `used_mut_nodes` table here.
-
- loop {
- debug!("mark_variable_as_used_mut(cmt={:?})", cmt);
- match cmt.cat.clone() {
- mc::cat_upvar(mc::Upvar { id: ty::UpvarId { var_id: id, .. }, .. }) |
- mc::cat_local(id) => {
- this.tcx().used_mut_nodes.borrow_mut().insert(id);
- return;
- }
-
- mc::cat_rvalue(..) |
- mc::cat_static_item |
- mc::cat_deref(_, _, mc::UnsafePtr(..)) |
- mc::cat_deref(_, _, mc::Implicit(..)) => {
- assert_eq!(cmt.mutbl, mc::McDeclared);
- return;
- }
-
- mc::cat_deref(_, _, mc::BorrowedPtr(..)) => {
- assert_eq!(cmt.mutbl, mc::McDeclared);
- // We need to drill down to upvar if applicable
- match cmt.upvar() {
- Some(b) => cmt = b,
- None => return
- }
- }
-
- mc::cat_deref(b, _, mc::Unique) => {
- assert_eq!(cmt.mutbl, mc::McInherited);
- cmt = b;
- }
-
- mc::cat_downcast(b, _) |
- mc::cat_interior(b, _) => {
- assert_eq!(cmt.mutbl, mc::McInherited);
- cmt = b;
- }
- }
- }
}
- fn check_for_aliasable_mutable_writes<'a, 'tcx>(this: &CheckLoanCtxt<'a, 'tcx>,
- span: Span,
- cmt: mc::cmt<'tcx>) -> bool {
- //! Safety checks related to writes to aliasable, mutable locations
-
- let guarantor = cmt.guarantor();
- debug!("check_for_aliasable_mutable_writes(cmt={:?}, guarantor={:?})",
- cmt, guarantor);
- if let mc::cat_deref(ref b, _, mc::BorrowedPtr(ty::MutBorrow, _)) = guarantor.cat {
- // Statically prohibit writes to `&mut` when aliasable
- check_for_aliasability_violation(this, span, b.clone());
+ // Local variables can always be assigned to, expect for reassignments
+ // of immutable variables (or assignments that invalidate loans,
+ // of course).
+ if let mc::cat_local(local_id) = assignee_cmt.cat {
+ if assignee_cmt.mutbl.is_mutable() {
+ self.tcx().used_mut_nodes.borrow_mut().insert(local_id);
}
- return true; // no errors reported
- }
-
- fn check_for_aliasability_violation<'a, 'tcx>(this: &CheckLoanCtxt<'a, 'tcx>,
- span: Span,
- cmt: mc::cmt<'tcx>)
- -> bool {
- match cmt.freely_aliasable(this.tcx()) {
- mc::Aliasability::NonAliasable => {
- return true;
- }
- mc::Aliasability::FreelyAliasable(mc::AliasableStaticMut(..)) => {
- return true;
- }
- mc::Aliasability::ImmutableUnique(_) => {
- this.bccx.report_aliasability_violation(
- span,
- MutabilityViolation,
- mc::AliasableReason::UnaliasableImmutable);
- return false;
- }
- mc::Aliasability::FreelyAliasable(cause) => {
- this.bccx.report_aliasability_violation(
- span,
- MutabilityViolation,
- cause);
- return false;
+ let lp = opt_loan_path(&assignee_cmt).unwrap();
+ self.move_data.each_assignment_of(assignment_id, &lp, |assign| {
+ if !assignee_cmt.mutbl.is_mutable() {
+ self.bccx.report_reassigned_immutable_variable(
+ assignment_span,
+ &*lp,
+ assign);
}
- }
- }
-
- fn check_for_assignment_to_borrowed_path<'a, 'tcx>(
- this: &CheckLoanCtxt<'a, 'tcx>,
- assignment_id: ast::NodeId,
- assignment_span: Span,
- assignee_cmt: mc::cmt<'tcx>)
- {
- //! Check for assignments that violate the terms of an
- //! outstanding loan.
-
- let loan_path = match opt_loan_path(&assignee_cmt) {
- Some(lp) => lp,
- None => { return; /* no loan path, can't be any loans */ }
- };
-
- let scope = region::CodeExtent::from_node_id(assignment_id);
- this.each_in_scope_loan_affecting_path(scope, &*loan_path, |loan| {
- this.report_illegal_mutation(assignment_span, &*loan_path, loan);
false
});
+ return
}
}
fn report_error(&self, code: bckerr_code) {
self.bccx.report(BckError { cmt: self.cmt_original.clone(),
span: self.span,
- cause: self.cause,
+ cause: BorrowViolation(self.cause),
code: code });
}
}
assignee_cmt: mc::cmt<'tcx>,
mode: euv::MutateMode)
{
- let opt_lp = opt_loan_path(&assignee_cmt);
- debug!("mutate(assignment_id={}, assignee_cmt={:?}) opt_lp={:?}",
- assignment_id, assignee_cmt, opt_lp);
-
- match opt_lp {
- Some(lp) => {
- gather_moves::gather_assignment(self.bccx, &self.move_data,
- assignment_id, assignment_span,
- lp, assignee_cmt.id, mode);
- }
- None => {
- // This can occur with e.g. `*foo() = 5`. In such
- // cases, there is no need to check for conflicts
- // with moves etc, just ignore.
- }
- }
+ self.guarantee_assignment_valid(assignment_id,
+ assignment_span,
+ assignee_cmt,
+ mode);
}
fn decl_without_init(&mut self, id: ast::NodeId, span: Span) {
/// Implements the A-* rules in README.md.
fn check_aliasability<'a, 'tcx>(bccx: &BorrowckCtxt<'a, 'tcx>,
borrow_span: Span,
- loan_cause: euv::LoanCause,
+ loan_cause: AliasableViolationKind,
cmt: mc::cmt<'tcx>,
req_kind: ty::BorrowKind)
-> Result<(),()> {
(mc::Aliasability::ImmutableUnique(_), ty::MutBorrow) => {
bccx.report_aliasability_violation(
borrow_span,
- BorrowViolation(loan_cause),
+ loan_cause,
mc::AliasableReason::UnaliasableImmutable);
Err(())
}
(mc::Aliasability::FreelyAliasable(alias_cause), ty::MutBorrow) => {
bccx.report_aliasability_violation(
borrow_span,
- BorrowViolation(loan_cause),
+ loan_cause,
alias_cause);
Err(())
}
}
}
+/// Implements the M-* rules in README.md.
+fn check_mutability<'a, 'tcx>(bccx: &BorrowckCtxt<'a, 'tcx>,
+ borrow_span: Span,
+ cause: AliasableViolationKind,
+ cmt: mc::cmt<'tcx>,
+ req_kind: ty::BorrowKind)
+ -> Result<(),()> {
+ debug!("check_mutability(cause={:?} cmt={:?} req_kind={:?}",
+ cause, cmt, req_kind);
+ match req_kind {
+ ty::UniqueImmBorrow | ty::ImmBorrow => {
+ match cmt.mutbl {
+ // I am intentionally leaving this here to help
+ // refactoring if, in the future, we should add new
+ // kinds of mutability.
+ mc::McImmutable | mc::McDeclared | mc::McInherited => {
+ // both imm and mut data can be lent as imm;
+ // for mutable data, this is a freeze
+ Ok(())
+ }
+ }
+ }
+
+ ty::MutBorrow => {
+ // Only mutable data can be lent as mutable.
+ if !cmt.mutbl.is_mutable() {
+ Err(bccx.report(BckError { span: borrow_span,
+ cause: cause,
+ cmt: cmt,
+ code: err_mutbl }))
+ } else {
+ Ok(())
+ }
+ }
+ }
+}
+
impl<'a, 'tcx> GatherLoanCtxt<'a, 'tcx> {
pub fn tcx(&self) -> &'a ty::ctxt<'tcx> { self.bccx.tcx }
+ /// Guarantees that `cmt` is assignable, or reports an error.
+ fn guarantee_assignment_valid(&mut self,
+ assignment_id: ast::NodeId,
+ assignment_span: Span,
+ cmt: mc::cmt<'tcx>,
+ mode: euv::MutateMode) {
+
+ let opt_lp = opt_loan_path(&cmt);
+ debug!("guarantee_assignment_valid(assignment_id={}, cmt={:?}) opt_lp={:?}",
+ assignment_id, cmt, opt_lp);
+
+ if let mc::cat_local(..) = cmt.cat {
+ // Only re-assignments to locals require it to be
+ // mutable - this is checked in check_loans.
+ } else {
+ // Check that we don't allow assignments to non-mutable data.
+ if check_mutability(self.bccx, assignment_span, MutabilityViolation,
+ cmt.clone(), ty::MutBorrow).is_err() {
+ return; // reported an error, no sense in reporting more.
+ }
+ }
+
+ // Check that we don't allow assignments to aliasable data
+ if check_aliasability(self.bccx, assignment_span, MutabilityViolation,
+ cmt.clone(), ty::MutBorrow).is_err() {
+ return; // reported an error, no sense in reporting more.
+ }
+
+ match opt_lp {
+ Some(lp) => {
+ if let mc::cat_local(..) = cmt.cat {
+ // Only re-assignments to locals require it to be
+ // mutable - this is checked in check_loans.
+ } else {
+ self.mark_loan_path_as_mutated(&lp);
+ }
+ gather_moves::gather_assignment(self.bccx, &self.move_data,
+ assignment_id, assignment_span,
+ lp, cmt.id, mode);
+ }
+ None => {
+ // This can occur with e.g. `*foo() = 5`. In such
+ // cases, there is no need to check for conflicts
+ // with moves etc, just ignore.
+ }
+ }
+ }
+
/// Guarantees that `addr_of(cmt)` will be valid for the duration of `static_scope_r`, or
/// reports an error. This may entail taking out loans, which will be added to the
/// `req_loan_map`.
}
// Check that we don't allow mutable borrows of non-mutable data.
- if check_mutability(self.bccx, borrow_span, cause,
+ if check_mutability(self.bccx, borrow_span, BorrowViolation(cause),
cmt.clone(), req_kind).is_err() {
return; // reported an error, no sense in reporting more.
}
// Check that we don't allow mutable borrows of aliasable data.
- if check_aliasability(self.bccx, borrow_span, cause,
+ if check_aliasability(self.bccx, borrow_span, BorrowViolation(cause),
cmt.clone(), req_kind).is_err() {
return; // reported an error, no sense in reporting more.
}
// restrictions: restrictions
// }
// }
-
- fn check_mutability<'a, 'tcx>(bccx: &BorrowckCtxt<'a, 'tcx>,
- borrow_span: Span,
- cause: euv::LoanCause,
- cmt: mc::cmt<'tcx>,
- req_kind: ty::BorrowKind)
- -> Result<(),()> {
- //! Implements the M-* rules in README.md.
- debug!("check_mutability(cause={:?} cmt={:?} req_kind={:?}",
- cause, cmt, req_kind);
- match req_kind {
- ty::UniqueImmBorrow | ty::ImmBorrow => {
- match cmt.mutbl {
- // I am intentionally leaving this here to help
- // refactoring if, in the future, we should add new
- // kinds of mutability.
- mc::McImmutable | mc::McDeclared | mc::McInherited => {
- // both imm and mut data can be lent as imm;
- // for mutable data, this is a freeze
- Ok(())
- }
- }
- }
-
- ty::MutBorrow => {
- // Only mutable data can be lent as mutable.
- if !cmt.mutbl.is_mutable() {
- Err(bccx.report(BckError { span: borrow_span,
- cause: cause,
- cmt: cmt,
- code: err_mutbl }))
- } else {
- Ok(())
- }
- }
- }
- }
}
pub fn mark_loan_path_as_mutated(&self, loan_path: &LoanPath) {
let base_cmt = mc.cat_expr(&**base).unwrap();
let borrow_kind = ty::BorrowKind::from_mutbl(mutbl);
// Check that we don't allow borrows of unsafe static items.
- if check_aliasability(self.bccx, ex.span, euv::AddrOf,
+ if check_aliasability(self.bccx, ex.span,
+ BorrowViolation(euv::AddrOf),
base_cmt, borrow_kind).is_err() {
return; // reported an error, no sense in reporting more.
}
self.bccx.report(
BckError {
span: self.span,
- cause: self.cause,
+ cause: BorrowViolation(self.cause),
cmt: cmt_base,
code: err_borrowed_pointer_too_short(
self.loan_region, lt)});
#[derive(PartialEq)]
pub struct BckError<'tcx> {
span: Span,
- cause: euv::LoanCause,
+ cause: AliasableViolationKind,
cmt: mc::cmt<'tcx>,
code: bckerr_code
}
-#[derive(Copy, Clone)]
+#[derive(Copy, Clone, Debug, PartialEq)]
pub enum AliasableViolationKind {
MutabilityViolation,
BorrowViolation(euv::LoanCause)
pub fn report(&self, err: BckError<'tcx>) {
// Catch and handle some particular cases.
match (&err.code, &err.cause) {
- (&err_out_of_scope(ty::ReScope(_), ty::ReStatic), &euv::ClosureCapture(span)) |
- (&err_out_of_scope(ty::ReScope(_), ty::ReFree(..)), &euv::ClosureCapture(span)) => {
+ (&err_out_of_scope(ty::ReScope(_), ty::ReStatic),
+ &BorrowViolation(euv::ClosureCapture(span))) |
+ (&err_out_of_scope(ty::ReScope(_), ty::ReFree(..)),
+ &BorrowViolation(euv::ClosureCapture(span))) => {
return self.report_out_of_scope_escaping_closure_capture(&err, span);
}
_ => { }
self.tcx.sess.span_end_note(s, m);
}
- pub fn span_help(&self, s: Span, m: &str) {
- self.tcx.sess.span_help(s, m);
- }
-
pub fn fileline_help(&self, s: Span, m: &str) {
self.tcx.sess.fileline_help(s, m);
}
};
match err.cause {
- euv::ClosureCapture(_) => {
+ MutabilityViolation => {
+ format!("cannot assign to {}", descr)
+ }
+ BorrowViolation(euv::ClosureCapture(_)) => {
format!("closure cannot assign to {}", descr)
}
- euv::OverloadedOperator |
- euv::AddrOf |
- euv::RefBinding |
- euv::AutoRef |
- euv::AutoUnsafe |
- euv::ForLoop |
- euv::MatchDiscriminant => {
+ BorrowViolation(euv::OverloadedOperator) |
+ BorrowViolation(euv::AddrOf) |
+ BorrowViolation(euv::RefBinding) |
+ BorrowViolation(euv::AutoRef) |
+ BorrowViolation(euv::AutoUnsafe) |
+ BorrowViolation(euv::ForLoop) |
+ BorrowViolation(euv::MatchDiscriminant) => {
format!("cannot borrow {} as mutable", descr)
}
- euv::ClosureInvocation => {
+ BorrowViolation(euv::ClosureInvocation) => {
self.tcx.sess.span_bug(err.span,
"err_mutbl with a closure invocation");
}
projects / rust.git / commitdiff