MIR-borrowck: fix diagnostics for closures
This commit is contained in:
Shotaro Yamada
parent
45caff88d1
commit
d3e9881ed1
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@ -1949,7 +1949,7 @@ impl ForeignItem_ {
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}
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/// A free variable referred to in a function.
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#[derive(Copy, Clone, RustcEncodable, RustcDecodable)]
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#[derive(Debug, Copy, Clone, RustcEncodable, RustcDecodable)]
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pub struct Freevar {
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/// The variable being accessed free.
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pub def: Def,
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@ -267,10 +267,10 @@ impl<'tcx> Mir<'tcx> {
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let block = &self[location.block];
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let stmts = &block.statements;
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let idx = location.statement_index;
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if location.statement_index < stmts.len() {
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if idx < stmts.len() {
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&stmts[idx].source_info
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} else {
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assert!(location.statement_index == stmts.len());
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assert!(idx == stmts.len());
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&block.terminator().source_info
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}
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}
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@ -1169,8 +1169,70 @@ impl<'c, 'b, 'a: 'b+'c, 'gcx, 'tcx: 'a> MirBorrowckCtxt<'c, 'b, 'a, 'gcx, 'tcx>
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err.emit();
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}
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/// Finds the span of arguments of aclosure (within `maybe_closure_span`) and its usage of
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/// the local assigned at `location`.
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fn find_closure_span(
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&self,
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maybe_closure_span: Span,
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location: Location,
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) -> Option<(Span, Span)> {
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use rustc::hir::ExprClosure;
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use rustc::mir::AggregateKind;
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let local = if let StatementKind::Assign(Lvalue::Local(local), _) =
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self.mir[location.block].statements[location.statement_index].kind
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{
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local
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} else {
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return None;
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};
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for stmt in &self.mir[location.block].statements[location.statement_index + 1..] {
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if maybe_closure_span != stmt.source_info.span {
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break;
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}
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if let StatementKind::Assign(_, Rvalue::Aggregate(ref kind, ref lvs)) = stmt.kind {
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if let AggregateKind::Closure(def_id, _) = **kind {
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debug!("find_closure_span: found closure {:?}", lvs);
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return if let Some(node_id) = self.tcx.hir.as_local_node_id(def_id) {
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let args_span = if let ExprClosure(_, _, _, span, _) =
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self.tcx.hir.expect_expr(node_id).node
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{
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span
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} else {
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return None;
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};
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self.tcx
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.with_freevars(node_id, |freevars| {
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for (v, lv) in freevars.iter().zip(lvs) {
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if let Operand::Consume(Lvalue::Local(l)) = *lv {
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if local == l {
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debug!(
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"find_closure_span: found captured local {:?}",
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l
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);
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return Some(v.span);
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}
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}
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}
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None
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})
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.map(|var_span| (args_span, var_span))
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} else {
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None
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};
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}
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}
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}
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None
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}
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fn report_conflicting_borrow(&mut self,
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_context: Context,
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context: Context,
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common_prefix: &Lvalue,
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(lvalue, span): (&Lvalue, Span),
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gen_borrow_kind: BorrowKind,
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@ -1183,38 +1245,60 @@ impl<'c, 'b, 'a: 'b+'c, 'gcx, 'tcx: 'a> MirBorrowckCtxt<'c, 'b, 'a, 'gcx, 'tcx>
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let issued_span = self.retrieve_borrow_span(issued_borrow);
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let new_closure_span = self.find_closure_span(span, context.loc);
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let span = new_closure_span.map(|(args, _)| args).unwrap_or(span);
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let old_closure_span = self.find_closure_span(issued_span, issued_borrow.location);
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let issued_span = old_closure_span.map(|(args, _)| args).unwrap_or(issued_span);
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let desc_lvalue = self.describe_lvalue(lvalue);
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// FIXME: supply non-"" `opt_via` when appropriate
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let mut err = match (gen_borrow_kind, "immutable", "mutable",
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issued_borrow.kind, "immutable", "mutable") {
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(BorrowKind::Shared, lft, _, BorrowKind::Mut, _, rgt) |
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(BorrowKind::Mut, _, lft, BorrowKind::Shared, rgt, _) =>
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self.tcx.cannot_reborrow_already_borrowed(
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span, &self.describe_lvalue(lvalue), "", lft, issued_span,
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span, &desc_lvalue, "", lft, issued_span,
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"it", rgt, "", end_issued_loan_span, Origin::Mir),
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(BorrowKind::Mut, _, _, BorrowKind::Mut, _, _) =>
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self.tcx.cannot_mutably_borrow_multiply(
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span, &self.describe_lvalue(lvalue), "", issued_span,
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span, &desc_lvalue, "", issued_span,
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"", end_issued_loan_span, Origin::Mir),
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(BorrowKind::Unique, _, _, BorrowKind::Unique, _, _) =>
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self.tcx.cannot_uniquely_borrow_by_two_closures(
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span, &self.describe_lvalue(lvalue), issued_span,
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span, &desc_lvalue, issued_span,
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end_issued_loan_span, Origin::Mir),
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(BorrowKind::Unique, _, _, _, _, _) =>
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self.tcx.cannot_uniquely_borrow_by_one_closure(
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span, &self.describe_lvalue(lvalue), "",
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span, &desc_lvalue, "",
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issued_span, "it", "", end_issued_loan_span, Origin::Mir),
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(_, _, _, BorrowKind::Unique, _, _) =>
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self.tcx.cannot_reborrow_already_uniquely_borrowed(
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span, &self.describe_lvalue(lvalue), "it", "",
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span, &desc_lvalue, "it", "",
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issued_span, "", end_issued_loan_span, Origin::Mir),
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(BorrowKind::Shared, _, _, BorrowKind::Shared, _, _) =>
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unreachable!(),
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};
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if let Some((_, var_span)) = old_closure_span {
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err.span_label(
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var_span,
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format!("previous borrow occurs due to use of `{}` in closure", desc_lvalue),
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);
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}
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if let Some((_, var_span)) = new_closure_span {
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err.span_label(
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var_span,
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format!("borrow occurs due to use of `{}` in closure", desc_lvalue),
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);
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}
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err.emit();
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}
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@ -0,0 +1,62 @@
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// Copyright 2014 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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// Tests that two closures cannot simultaneously have mutable
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// access to the variable, whether that mutable access be used
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// for direct assignment or for taking mutable ref. Issue #6801.
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// compile-flags: -Z emit-end-regions -Z borrowck-mir
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#![feature(box_syntax)]
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fn to_fn_mut<F: FnMut()>(f: F) -> F { f }
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fn a() {
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let mut x = 3;
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let c1 = to_fn_mut(|| x = 4);
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let c2 = to_fn_mut(|| x = 5); //~ ERROR cannot borrow `x` as mutable more than once
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}
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fn set(x: &mut isize) {
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*x = 4;
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}
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fn b() {
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let mut x = 3;
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let c1 = to_fn_mut(|| set(&mut x));
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let c2 = to_fn_mut(|| set(&mut x)); //~ ERROR cannot borrow `x` as mutable more than once
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}
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fn c() {
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let mut x = 3;
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let c1 = to_fn_mut(|| x = 5);
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let c2 = to_fn_mut(|| set(&mut x)); //~ ERROR cannot borrow `x` as mutable more than once
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}
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fn d() {
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let mut x = 3;
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let c1 = to_fn_mut(|| x = 5);
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let c2 = to_fn_mut(|| { let _y = to_fn_mut(|| set(&mut x)); }); // (nested closure)
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//~^ ERROR cannot borrow `x` as mutable more than once
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}
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fn g() {
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struct Foo {
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f: Box<isize>
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}
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let mut x: Box<_> = box Foo { f: box 3 };
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let c1 = to_fn_mut(|| set(&mut *x.f));
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let c2 = to_fn_mut(|| set(&mut *x.f));
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//~^ ERROR cannot borrow `x` as mutable more than once
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}
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fn main() {
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}
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@ -0,0 +1,146 @@
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error[E0499]: cannot borrow `x` as mutable more than once at a time (Ast)
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--> $DIR/borrowck-closures-two-mut.rs:24:24
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23 | let c1 = to_fn_mut(|| x = 4);
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| -- - previous borrow occurs due to use of `x` in closure
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| first mutable borrow occurs here
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24 | let c2 = to_fn_mut(|| x = 5); //~ ERROR cannot borrow `x` as mutable more than once
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| ^^ - borrow occurs due to use of `x` in closure
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| second mutable borrow occurs here
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25 | }
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| - first borrow ends here
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error[E0499]: cannot borrow `x` as mutable more than once at a time (Ast)
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--> $DIR/borrowck-closures-two-mut.rs:34:24
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33 | let c1 = to_fn_mut(|| set(&mut x));
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| -- - previous borrow occurs due to use of `x` in closure
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| first mutable borrow occurs here
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34 | let c2 = to_fn_mut(|| set(&mut x)); //~ ERROR cannot borrow `x` as mutable more than once
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| ^^ - borrow occurs due to use of `x` in closure
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| second mutable borrow occurs here
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35 | }
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| - first borrow ends here
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error[E0499]: cannot borrow `x` as mutable more than once at a time (Ast)
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--> $DIR/borrowck-closures-two-mut.rs:40:24
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39 | let c1 = to_fn_mut(|| x = 5);
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| -- - previous borrow occurs due to use of `x` in closure
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| first mutable borrow occurs here
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40 | let c2 = to_fn_mut(|| set(&mut x)); //~ ERROR cannot borrow `x` as mutable more than once
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| ^^ - borrow occurs due to use of `x` in closure
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| |
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| second mutable borrow occurs here
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41 | }
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| - first borrow ends here
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error[E0499]: cannot borrow `x` as mutable more than once at a time (Ast)
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--> $DIR/borrowck-closures-two-mut.rs:46:24
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45 | let c1 = to_fn_mut(|| x = 5);
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| -- - previous borrow occurs due to use of `x` in closure
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| first mutable borrow occurs here
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46 | let c2 = to_fn_mut(|| { let _y = to_fn_mut(|| set(&mut x)); }); // (nested closure)
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| ^^ - borrow occurs due to use of `x` in closure
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| |
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| second mutable borrow occurs here
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47 | //~^ ERROR cannot borrow `x` as mutable more than once
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48 | }
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| - first borrow ends here
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error[E0499]: cannot borrow `x` as mutable more than once at a time (Ast)
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--> $DIR/borrowck-closures-two-mut.rs:57:24
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56 | let c1 = to_fn_mut(|| set(&mut *x.f));
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| -- - previous borrow occurs due to use of `x` in closure
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| |
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| first mutable borrow occurs here
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57 | let c2 = to_fn_mut(|| set(&mut *x.f));
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| ^^ - borrow occurs due to use of `x` in closure
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| |
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| second mutable borrow occurs here
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58 | //~^ ERROR cannot borrow `x` as mutable more than once
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59 | }
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| - first borrow ends here
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error[E0499]: cannot borrow `x` as mutable more than once at a time (Mir)
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--> $DIR/borrowck-closures-two-mut.rs:24:24
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23 | let c1 = to_fn_mut(|| x = 4);
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| -- - previous borrow occurs due to use of `x` in closure
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| |
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| first mutable borrow occurs here
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24 | let c2 = to_fn_mut(|| x = 5); //~ ERROR cannot borrow `x` as mutable more than once
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| ^^ - borrow occurs due to use of `x` in closure
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| |
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| second mutable borrow occurs here
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25 | }
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| - first borrow ends here
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error[E0499]: cannot borrow `x` as mutable more than once at a time (Mir)
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--> $DIR/borrowck-closures-two-mut.rs:34:24
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33 | let c1 = to_fn_mut(|| set(&mut x));
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| -- - previous borrow occurs due to use of `x` in closure
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| |
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| first mutable borrow occurs here
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34 | let c2 = to_fn_mut(|| set(&mut x)); //~ ERROR cannot borrow `x` as mutable more than once
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| ^^ - borrow occurs due to use of `x` in closure
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| |
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| second mutable borrow occurs here
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35 | }
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| - first borrow ends here
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error[E0499]: cannot borrow `x` as mutable more than once at a time (Mir)
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--> $DIR/borrowck-closures-two-mut.rs:40:24
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39 | let c1 = to_fn_mut(|| x = 5);
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| -- - previous borrow occurs due to use of `x` in closure
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| |
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| first mutable borrow occurs here
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40 | let c2 = to_fn_mut(|| set(&mut x)); //~ ERROR cannot borrow `x` as mutable more than once
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| ^^ - borrow occurs due to use of `x` in closure
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| |
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| second mutable borrow occurs here
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41 | }
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| - first borrow ends here
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error[E0499]: cannot borrow `x` as mutable more than once at a time (Mir)
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--> $DIR/borrowck-closures-two-mut.rs:46:24
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45 | let c1 = to_fn_mut(|| x = 5);
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| -- - previous borrow occurs due to use of `x` in closure
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| |
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| first mutable borrow occurs here
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46 | let c2 = to_fn_mut(|| { let _y = to_fn_mut(|| set(&mut x)); }); // (nested closure)
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| ^^ - borrow occurs due to use of `x` in closure
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| |
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| second mutable borrow occurs here
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47 | //~^ ERROR cannot borrow `x` as mutable more than once
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48 | }
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| - first borrow ends here
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error[E0499]: cannot borrow `x` as mutable more than once at a time (Mir)
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--> $DIR/borrowck-closures-two-mut.rs:57:24
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56 | let c1 = to_fn_mut(|| set(&mut *x.f));
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| -- - previous borrow occurs due to use of `x` in closure
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| |
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| first mutable borrow occurs here
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57 | let c2 = to_fn_mut(|| set(&mut *x.f));
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| ^^ - borrow occurs due to use of `x` in closure
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| |
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| second mutable borrow occurs here
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58 | //~^ ERROR cannot borrow `x` as mutable more than once
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59 | }
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| - first borrow ends here
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error: aborting due to 10 previous errors
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