765 lines
29 KiB
Rust
765 lines
29 KiB
Rust
// Copyright 2012 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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// ----------------------------------------------------------------------
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// Checking loans
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//
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// Phase 2 of check: we walk down the tree and check that:
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// 1. assignments are always made to mutable locations;
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// 2. loans made in overlapping scopes do not conflict
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// 3. assignments do not affect things loaned out as immutable
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// 4. moves do not affect things loaned out in any way
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use middle::moves;
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use middle::borrowck::*;
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use mc = middle::mem_categorization;
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use middle::ty;
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use util::ppaux::Repr;
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use core::hashmap::HashSet;
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use syntax::ast::{m_mutbl, m_imm, m_const};
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use syntax::ast;
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use syntax::ast_util;
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use syntax::visit;
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use syntax::codemap::span;
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struct CheckLoanCtxt<'self> {
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bccx: @BorrowckCtxt,
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dfcx: &'self LoanDataFlow,
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all_loans: &'self [Loan],
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reported: @mut HashSet<ast::node_id>,
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}
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pub fn check_loans(bccx: @BorrowckCtxt,
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dfcx: &LoanDataFlow,
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all_loans: &[Loan],
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body: &ast::blk) {
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debug!("check_loans(body id=%?)", body.node.id);
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let clcx = @mut CheckLoanCtxt {
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bccx: bccx,
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dfcx: dfcx,
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all_loans: all_loans,
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reported: @mut HashSet::new(),
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};
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let vt = visit::mk_vt(@visit::Visitor {visit_expr: check_loans_in_expr,
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visit_local: check_loans_in_local,
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visit_block: check_loans_in_block,
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visit_pat: check_loans_in_pat,
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visit_fn: check_loans_in_fn,
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.. *visit::default_visitor()});
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(vt.visit_block)(body, clcx, vt);
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}
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enum MoveError {
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MoveOk,
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MoveFromIllegalCmt(mc::cmt),
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MoveWhileBorrowed(/*loan*/@LoanPath, /*loan*/span)
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}
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pub impl<'self> CheckLoanCtxt<'self> {
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fn tcx(&self) -> ty::ctxt { self.bccx.tcx }
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fn each_issued_loan(&self,
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scope_id: ast::node_id,
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op: &fn(&Loan) -> bool)
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{
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//! Iterates over each loan that that has been issued
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//! on entrance to `scope_id`, regardless of whether it is
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//! actually *in scope* at that point. Sometimes loans
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//! are issued for future scopes and thus they may have been
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//! *issued* but not yet be in effect.
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for self.dfcx.each_bit_on_entry(scope_id) |loan_index| {
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let loan = &self.all_loans[loan_index];
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if !op(loan) {
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return;
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}
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}
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}
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fn each_in_scope_loan(&self,
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scope_id: ast::node_id,
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op: &fn(&Loan) -> bool)
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{
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//! Like `each_issued_loan()`, but only considers loans that are
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//! currently in scope.
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let region_maps = self.tcx().region_maps;
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for self.each_issued_loan(scope_id) |loan| {
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if region_maps.is_subscope_of(scope_id, loan.kill_scope) {
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if !op(loan) {
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return;
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}
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}
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}
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}
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fn each_in_scope_restriction(&self,
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scope_id: ast::node_id,
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loan_path: @LoanPath,
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op: &fn(&Loan, &Restriction) -> bool)
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{
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//! Iterates through all the in-scope restrictions for the
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//! given `loan_path`
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for self.each_in_scope_loan(scope_id) |loan| {
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for loan.restrictions.each |restr| {
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if restr.loan_path == loan_path {
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if !op(loan, restr) {
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return;
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}
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}
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}
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}
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}
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fn loans_generated_by(&self, scope_id: ast::node_id) -> ~[uint] {
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//! Returns a vector of the loans that are generated as
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//! we encounter `scope_id`.
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let mut result = ~[];
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for self.dfcx.each_gen_bit(scope_id) |loan_index| {
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result.push(loan_index);
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}
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return result;
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}
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fn check_for_conflicting_loans(&mut self, scope_id: ast::node_id) {
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//! Checks to see whether any of the loans that are issued
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//! by `scope_id` conflict with loans that have already been
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//! issued when we enter `scope_id` (for example, we do not
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//! permit two `&mut` borrows of the same variable).
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debug!("check_for_conflicting_loans(scope_id=%?)", scope_id);
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let new_loan_indices = self.loans_generated_by(scope_id);
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debug!("new_loan_indices = %?", new_loan_indices);
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for self.each_issued_loan(scope_id) |issued_loan| {
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for new_loan_indices.each |&new_loan_index| {
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let new_loan = &self.all_loans[new_loan_index];
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self.report_error_if_loans_conflict(issued_loan, new_loan);
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}
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}
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for uint::range(0, new_loan_indices.len()) |i| {
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let old_loan = &self.all_loans[new_loan_indices[i]];
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for uint::range(i+1, new_loan_indices.len()) |j| {
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let new_loan = &self.all_loans[new_loan_indices[j]];
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self.report_error_if_loans_conflict(old_loan, new_loan);
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}
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}
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}
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fn report_error_if_loans_conflict(&self,
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old_loan: &Loan,
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new_loan: &Loan) {
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//! Checks whether `old_loan` and `new_loan` can safely be issued
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//! simultaneously.
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debug!("report_error_if_loans_conflict(old_loan=%s, new_loan=%s)",
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old_loan.repr(self.tcx()),
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new_loan.repr(self.tcx()));
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// Should only be called for loans that are in scope at the same time.
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let region_maps = self.tcx().region_maps;
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assert!(region_maps.scopes_intersect(old_loan.kill_scope,
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new_loan.kill_scope));
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self.report_error_if_loan_conflicts_with_restriction(
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old_loan, new_loan, old_loan, new_loan) &&
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self.report_error_if_loan_conflicts_with_restriction(
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new_loan, old_loan, old_loan, new_loan);
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}
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fn report_error_if_loan_conflicts_with_restriction(&self,
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loan1: &Loan,
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loan2: &Loan,
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old_loan: &Loan,
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new_loan: &Loan) -> bool {
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//! Checks whether the restrictions introduced by `loan1` would
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//! prohibit `loan2`. Returns false if an error is reported.
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debug!("report_error_if_loan_conflicts_with_restriction(\
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loan1=%s, loan2=%s)",
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loan1.repr(self.tcx()),
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loan2.repr(self.tcx()));
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// Restrictions that would cause the new loan to be immutable:
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let illegal_if = match loan2.mutbl {
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m_mutbl => RESTR_ALIAS | RESTR_FREEZE | RESTR_MUTATE,
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m_imm => RESTR_ALIAS | RESTR_FREEZE,
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m_const => RESTR_ALIAS,
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};
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debug!("illegal_if=%?", illegal_if);
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for loan1.restrictions.each |restr| {
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if !restr.set.intersects(illegal_if) { loop; }
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if restr.loan_path != loan2.loan_path { loop; }
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match (new_loan.mutbl, old_loan.mutbl) {
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(m_mutbl, m_mutbl) => {
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self.bccx.span_err(
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new_loan.span,
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fmt!("cannot borrow `%s` as mutable \
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more than once at at a time",
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self.bccx.loan_path_to_str(new_loan.loan_path)));
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self.bccx.span_note(
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old_loan.span,
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fmt!("second borrow of `%s` as mutable occurs here",
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self.bccx.loan_path_to_str(new_loan.loan_path)));
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return false;
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}
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_ => {
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self.bccx.span_err(
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new_loan.span,
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fmt!("cannot borrow `%s` as %s because \
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it is also borrowed as %s"
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self.bccx.loan_path_to_str(new_loan.loan_path),
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self.bccx.mut_to_str(new_loan.mutbl),
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self.bccx.mut_to_str(old_loan.mutbl)));
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self.bccx.span_note(
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old_loan.span,
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fmt!("second borrow of `%s` occurs here",
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self.bccx.loan_path_to_str(new_loan.loan_path)));
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return false;
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}
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}
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}
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true
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}
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fn is_local_variable(&self, cmt: mc::cmt) -> bool {
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match cmt.cat {
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mc::cat_local(_) => true,
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_ => false
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}
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}
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fn check_assignment(&self, expr: @ast::expr) {
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// We don't use cat_expr() here because we don't want to treat
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// auto-ref'd parameters in overloaded operators as rvalues.
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let cmt = match self.bccx.tcx.adjustments.find(&expr.id) {
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None => self.bccx.cat_expr_unadjusted(expr),
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Some(&adj) => self.bccx.cat_expr_autoderefd(expr, adj)
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};
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debug!("check_assignment(cmt=%s)", cmt.repr(self.tcx()));
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// check that the value being assigned is declared as mutable
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// and report an error otherwise.
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match cmt.mutbl {
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mc::McDeclared => {
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// OK, but we have to mark arguments as requiring mut
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// if they are assigned (other cases are handled by liveness,
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// since we need to distinguish local variables assigned
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// once vs those assigned multiple times)
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match cmt.cat {
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mc::cat_self(*) |
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mc::cat_arg(*) => {
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mark_variable_as_used_mut(self, cmt);
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}
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_ => {}
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}
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}
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mc::McInherited => {
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// OK, but we may have to add an entry to `used_mut_nodes`
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mark_variable_as_used_mut(self, cmt);
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}
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mc::McReadOnly | mc::McImmutable => {
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// Subtle: liveness guarantees that immutable local
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// variables are only assigned once, so no need to
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// report an error for an assignment to a local
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// variable (note also that it is not legal to borrow
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// for a local variable before it has been assigned
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// for the first time).
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if !self.is_local_variable(cmt) {
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self.bccx.span_err(
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expr.span,
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fmt!("cannot assign to %s %s"
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cmt.mutbl.to_user_str(),
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self.bccx.cmt_to_str(cmt)));
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}
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return;
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}
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}
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if check_for_aliasable_mutable_writes(self, expr, cmt) {
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check_for_assignment_to_restricted_or_frozen_location(
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self, expr, cmt);
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}
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fn mark_variable_as_used_mut(self: &CheckLoanCtxt,
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cmt: mc::cmt) {
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//! If the mutability of the `cmt` being written is inherited
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//! from a local variable, liveness will
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//! not have been able to detect that this variable's mutability
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//! is important, so we must add the variable to the
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//! `used_mut_nodes` table here.
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let mut cmt = cmt;
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loop {
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debug!("mark_writes_through_upvars_as_used_mut(cmt=%s)",
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cmt.repr(self.tcx()));
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match cmt.cat {
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mc::cat_local(id) |
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mc::cat_arg(id) |
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mc::cat_self(id) => {
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self.tcx().used_mut_nodes.insert(id);
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return;
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}
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mc::cat_stack_upvar(b) => {
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cmt = b;
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}
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mc::cat_rvalue |
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mc::cat_static_item |
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mc::cat_implicit_self |
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mc::cat_copied_upvar(*) |
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mc::cat_deref(_, _, mc::unsafe_ptr(*)) |
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mc::cat_deref(_, _, mc::gc_ptr(*)) |
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mc::cat_deref(_, _, mc::region_ptr(*)) => {
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assert_eq!(cmt.mutbl, mc::McDeclared);
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return;
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}
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mc::cat_discr(b, _) |
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mc::cat_deref(b, _, mc::uniq_ptr(*)) => {
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assert_eq!(cmt.mutbl, mc::McInherited);
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cmt = b;
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}
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mc::cat_interior(b, _) => {
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if cmt.mutbl == mc::McInherited {
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cmt = b;
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} else {
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return; // field declared as mutable or some such
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}
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}
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}
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}
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}
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fn check_for_aliasable_mutable_writes(self: &CheckLoanCtxt,
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expr: @ast::expr,
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cmt: mc::cmt) -> bool {
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//! Safety checks related to writes to aliasable, mutable locations
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let guarantor = cmt.guarantor();
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debug!("check_for_aliasable_mutable_writes(cmt=%s, guarantor=%s)",
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cmt.repr(self.tcx()), guarantor.repr(self.tcx()));
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match guarantor.cat {
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mc::cat_deref(b, _, mc::region_ptr(m_mutbl, _)) => {
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// Statically prohibit writes to `&mut` when aliasable
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match b.freely_aliasable() {
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None => {}
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Some(cause) => {
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self.bccx.report_aliasability_violation(
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expr.span,
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MutabilityViolation,
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cause);
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}
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}
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}
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mc::cat_deref(base, deref_count, mc::gc_ptr(ast::m_mutbl)) => {
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// Dynamically check writes to `@mut`
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let key = root_map_key {
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id: base.id,
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derefs: deref_count
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};
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debug!("Inserting write guard at %?", key);
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self.bccx.write_guard_map.insert(key);
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}
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_ => {}
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}
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return true; // no errors reported
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}
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fn check_for_assignment_to_restricted_or_frozen_location(
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self: &CheckLoanCtxt,
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expr: @ast::expr,
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cmt: mc::cmt) -> bool
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{
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//! Check for assignments that violate the terms of an
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//! outstanding loan.
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let loan_path = match opt_loan_path(cmt) {
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Some(lp) => lp,
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None => { return true; /* no loan path, can't be any loans */ }
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};
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// Start by searching for an assignment to a *restricted*
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// location. Here is one example of the kind of error caught
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// by this check:
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//
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// let mut v = ~[1, 2, 3];
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// let p = &v;
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// v = ~[4];
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//
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// In this case, creating `p` triggers a RESTR_MUTATE
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// restriction on the path `v`.
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//
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// Here is a second, more subtle example:
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//
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// let mut v = ~[1, 2, 3];
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// let p = &const v[0];
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// v[0] = 4; // OK
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// v[1] = 5; // OK
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// v = ~[4, 5, 3]; // Error
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//
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// In this case, `p` is pointing to `v[0]`, and it is a
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// `const` pointer in any case. So the first two
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// assignments are legal (and would be permitted by this
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// check). However, the final assignment (which is
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// logically equivalent) is forbidden, because it would
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// cause the existing `v` array to be freed, thus
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// invalidating `p`. In the code, this error results
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// because `gather_loans::restrictions` adds a
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// `RESTR_MUTATE` restriction whenever the contents of an
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// owned pointer are borrowed, and hence while `v[*]` is not
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// restricted from being written, `v` is.
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for self.each_in_scope_restriction(expr.id, loan_path)
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|loan, restr|
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{
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if restr.set.intersects(RESTR_MUTATE) {
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self.report_illegal_mutation(expr, loan_path, loan);
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return false;
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}
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}
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// The previous code handled assignments to paths that
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// have been restricted. This covers paths that have been
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// directly lent out and their base paths, but does not
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// cover random extensions of those paths. For example,
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// the following program is not declared illegal by the
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// previous check:
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//
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// let mut v = ~[1, 2, 3];
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// let p = &v;
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// v[0] = 4; // declared error by loop below, not code above
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//
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// The reason that this passes the previous check whereas
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// an assignment like `v = ~[4]` fails is because the assignment
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// here is to `v[*]`, and the existing restrictions were issued
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// for `v`, not `v[*]`.
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//
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// So in this loop, we walk back up the loan path so long
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// as the mutability of the path is dependent on a super
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// path, and check that the super path was not lent out as
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// mutable or immutable (a const loan is ok).
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//
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// Note that we are *not* checking for any and all
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// restrictions. We are only interested in the pointers
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// that the user created, whereas we add restrictions for
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// all kinds of paths that are not directly aliased. If we checked
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// for all restrictions, and not just loans, then the following
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// valid program would be considered illegal:
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//
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// let mut v = ~[1, 2, 3];
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// let p = &const v[0];
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// v[1] = 5; // ok
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//
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// Here the restriction that `v` not be mutated would be misapplied
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// to block the subpath `v[1]`.
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let full_loan_path = loan_path;
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let mut loan_path = loan_path;
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loop {
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match *loan_path {
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// Peel back one layer if `loan_path` has
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// inherited mutability
|
|
LpExtend(lp_base, mc::McInherited, _) => {
|
|
loan_path = lp_base;
|
|
}
|
|
|
|
// Otherwise stop iterating
|
|
LpExtend(_, mc::McDeclared, _) |
|
|
LpExtend(_, mc::McImmutable, _) |
|
|
LpExtend(_, mc::McReadOnly, _) |
|
|
LpVar(_) => {
|
|
return true;
|
|
}
|
|
}
|
|
|
|
// Check for a non-const loan of `loan_path`
|
|
for self.each_in_scope_loan(expr.id) |loan| {
|
|
if loan.loan_path == loan_path && loan.mutbl != m_const {
|
|
self.report_illegal_mutation(expr, full_loan_path, loan);
|
|
return false;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
fn report_illegal_mutation(&self,
|
|
expr: @ast::expr,
|
|
loan_path: &LoanPath,
|
|
loan: &Loan) {
|
|
self.bccx.span_err(
|
|
expr.span,
|
|
fmt!("cannot assign to `%s` because it is borrowed",
|
|
self.bccx.loan_path_to_str(loan_path)));
|
|
self.bccx.span_note(
|
|
loan.span,
|
|
fmt!("borrow of `%s` occurs here",
|
|
self.bccx.loan_path_to_str(loan_path)));
|
|
}
|
|
|
|
fn check_move_out_from_expr(&self, ex: @ast::expr) {
|
|
match ex.node {
|
|
ast::expr_paren(*) => {
|
|
/* In the case of an expr_paren(), the expression inside
|
|
* the parens will also be marked as being moved. Ignore
|
|
* the parents then so as not to report duplicate errors. */
|
|
}
|
|
_ => {
|
|
let cmt = self.bccx.cat_expr(ex);
|
|
match self.analyze_move_out_from_cmt(cmt) {
|
|
MoveOk => {}
|
|
MoveFromIllegalCmt(_) => {
|
|
self.bccx.span_err(
|
|
cmt.span,
|
|
fmt!("cannot move out of %s",
|
|
self.bccx.cmt_to_str(cmt)));
|
|
}
|
|
MoveWhileBorrowed(loan_path, loan_span) => {
|
|
self.bccx.span_err(
|
|
cmt.span,
|
|
fmt!("cannot move out of `%s` \
|
|
because it is borrowed",
|
|
self.bccx.loan_path_to_str(loan_path)));
|
|
self.bccx.span_note(
|
|
loan_span,
|
|
fmt!("borrow of `%s` occurs here",
|
|
self.bccx.loan_path_to_str(loan_path)));
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
fn analyze_move_out_from_cmt(&self, cmt: mc::cmt) -> MoveError {
|
|
debug!("check_move_out_from_cmt(cmt=%s)", cmt.repr(self.tcx()));
|
|
|
|
match cmt.cat {
|
|
// Rvalues, locals, and arguments can be moved:
|
|
mc::cat_rvalue | mc::cat_local(_) |
|
|
mc::cat_arg(_) | mc::cat_self(_) => {}
|
|
|
|
// It seems strange to allow a move out of a static item,
|
|
// but what happens in practice is that you have a
|
|
// reference to a constant with a type that should be
|
|
// moved, like `None::<~int>`. The type of this constant
|
|
// is technically `Option<~int>`, which moves, but we know
|
|
// that the content of static items will never actually
|
|
// contain allocated pointers, so we can just memcpy it.
|
|
mc::cat_static_item => {}
|
|
|
|
mc::cat_deref(_, _, mc::unsafe_ptr(*)) => {}
|
|
|
|
// Nothing else.
|
|
_ => {
|
|
return MoveFromIllegalCmt(cmt);
|
|
}
|
|
}
|
|
|
|
// NOTE inadequare if/when we permit `move a.b`
|
|
|
|
// check for a conflicting loan:
|
|
for opt_loan_path(cmt).each |&lp| {
|
|
for self.each_in_scope_restriction(cmt.id, lp) |loan, _| {
|
|
// Any restriction prevents moves.
|
|
return MoveWhileBorrowed(loan.loan_path, loan.span);
|
|
}
|
|
}
|
|
|
|
return MoveOk;
|
|
}
|
|
|
|
fn check_call(&mut self,
|
|
_expr: @ast::expr,
|
|
_callee: Option<@ast::expr>,
|
|
_callee_id: ast::node_id,
|
|
_callee_span: span,
|
|
_args: &[@ast::expr])
|
|
{
|
|
// NB: This call to check for conflicting loans is not truly
|
|
// necessary, because the callee_id never issues new loans.
|
|
// However, I added it for consistency and lest the system
|
|
// should change in the future.
|
|
//
|
|
// FIXME(#5074) nested method calls
|
|
// self.check_for_conflicting_loans(callee_id);
|
|
}
|
|
}
|
|
|
|
fn check_loans_in_fn<'a>(fk: &visit::fn_kind,
|
|
decl: &ast::fn_decl,
|
|
body: &ast::blk,
|
|
sp: span,
|
|
id: ast::node_id,
|
|
self: @mut CheckLoanCtxt<'a>,
|
|
visitor: visit::vt<@mut CheckLoanCtxt<'a>>) {
|
|
match *fk {
|
|
visit::fk_item_fn(*) |
|
|
visit::fk_method(*) |
|
|
visit::fk_dtor(*) => {
|
|
// Don't process nested items.
|
|
return;
|
|
}
|
|
|
|
visit::fk_anon(*) |
|
|
visit::fk_fn_block(*) => {
|
|
let fty = ty::node_id_to_type(self.tcx(), id);
|
|
let fty_sigil = ty::ty_closure_sigil(fty);
|
|
check_moves_from_captured_variables(self, id, fty_sigil);
|
|
}
|
|
}
|
|
|
|
visit::visit_fn(fk, decl, body, sp, id, self, visitor);
|
|
|
|
fn check_moves_from_captured_variables(self: @mut CheckLoanCtxt,
|
|
id: ast::node_id,
|
|
fty_sigil: ast::Sigil) {
|
|
match fty_sigil {
|
|
ast::ManagedSigil | ast::OwnedSigil => {
|
|
let cap_vars = self.bccx.capture_map.get(&id);
|
|
for cap_vars.each |cap_var| {
|
|
match cap_var.mode {
|
|
moves::CapRef | moves::CapCopy => { loop; }
|
|
moves::CapMove => { }
|
|
}
|
|
let def_id = ast_util::def_id_of_def(cap_var.def).node;
|
|
let ty = ty::node_id_to_type(self.tcx(), def_id);
|
|
let cmt = self.bccx.cat_def(id, cap_var.span,
|
|
ty, cap_var.def);
|
|
let move_err = self.analyze_move_out_from_cmt(cmt);
|
|
match move_err {
|
|
MoveOk => {}
|
|
MoveFromIllegalCmt(move_cmt) => {
|
|
self.bccx.span_err(
|
|
cap_var.span,
|
|
fmt!("illegal by-move capture of %s",
|
|
self.bccx.cmt_to_str(move_cmt)));
|
|
}
|
|
MoveWhileBorrowed(loan_path, loan_span) => {
|
|
self.bccx.span_err(
|
|
cap_var.span,
|
|
fmt!("cannot move `%s` into closure \
|
|
because it is borrowed",
|
|
self.bccx.loan_path_to_str(loan_path)));
|
|
self.bccx.span_note(
|
|
loan_span,
|
|
fmt!("borrow of `%s` occurs here",
|
|
self.bccx.loan_path_to_str(loan_path)));
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
ast::BorrowedSigil => {}
|
|
}
|
|
}
|
|
}
|
|
|
|
fn check_loans_in_local<'a>(local: @ast::local,
|
|
self: @mut CheckLoanCtxt<'a>,
|
|
vt: visit::vt<@mut CheckLoanCtxt<'a>>) {
|
|
visit::visit_local(local, self, vt);
|
|
}
|
|
|
|
fn check_loans_in_expr<'a>(expr: @ast::expr,
|
|
self: @mut CheckLoanCtxt<'a>,
|
|
vt: visit::vt<@mut CheckLoanCtxt<'a>>) {
|
|
debug!("check_loans_in_expr(expr=%s)",
|
|
expr.repr(self.tcx()));
|
|
|
|
visit::visit_expr(expr, self, vt);
|
|
|
|
self.check_for_conflicting_loans(expr.id);
|
|
|
|
if self.bccx.moves_map.contains(&expr.id) {
|
|
self.check_move_out_from_expr(expr);
|
|
}
|
|
|
|
match expr.node {
|
|
ast::expr_swap(l, r) => {
|
|
self.check_assignment(l);
|
|
self.check_assignment(r);
|
|
}
|
|
ast::expr_assign(dest, _) |
|
|
ast::expr_assign_op(_, dest, _) => {
|
|
self.check_assignment(dest);
|
|
}
|
|
ast::expr_call(f, ref args, _) => {
|
|
self.check_call(expr, Some(f), f.id, f.span, *args);
|
|
}
|
|
ast::expr_method_call(_, _, _, ref args, _) => {
|
|
self.check_call(expr, None, expr.callee_id, expr.span, *args);
|
|
}
|
|
ast::expr_index(_, rval) |
|
|
ast::expr_binary(_, _, rval)
|
|
if self.bccx.method_map.contains_key(&expr.id) => {
|
|
self.check_call(expr,
|
|
None,
|
|
expr.callee_id,
|
|
expr.span,
|
|
~[rval]);
|
|
}
|
|
ast::expr_unary(*) | ast::expr_index(*)
|
|
if self.bccx.method_map.contains_key(&expr.id) => {
|
|
self.check_call(expr,
|
|
None,
|
|
expr.callee_id,
|
|
expr.span,
|
|
~[]);
|
|
}
|
|
_ => { }
|
|
}
|
|
}
|
|
|
|
fn check_loans_in_pat<'a>(pat: @ast::pat,
|
|
self: @mut CheckLoanCtxt<'a>,
|
|
vt: visit::vt<@mut CheckLoanCtxt<'a>>)
|
|
{
|
|
self.check_for_conflicting_loans(pat.id);
|
|
|
|
// Note: moves out of pattern bindings are not checked by
|
|
// the borrow checker, at least not directly. What happens
|
|
// is that if there are any moved bindings, the discriminant
|
|
// will be considered a move, and this will be checked as
|
|
// normal. Then, in `middle::check_match`, we will check
|
|
// that no move occurs in a binding that is underneath an
|
|
// `@` or `&`. Together these give the same guarantees as
|
|
// `check_move_out_from_expr()` without requiring us to
|
|
// rewalk the patterns and rebuild the pattern
|
|
// categorizations.
|
|
|
|
visit::visit_pat(pat, self, vt);
|
|
}
|
|
|
|
fn check_loans_in_block<'a>(blk: &ast::blk,
|
|
self: @mut CheckLoanCtxt<'a>,
|
|
vt: visit::vt<@mut CheckLoanCtxt<'a>>)
|
|
{
|
|
visit::visit_block(blk, self, vt);
|
|
self.check_for_conflicting_loans(blk.node.id);
|
|
}
|
|
|