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test describing a currently unsupported corner case.
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src/test/compile-fail/borrowck/two-phase-reservation-sharing-interference.rs
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// Copyright 2017 The Rust Project Developers. See the COPYRIGHT | ||
// file at the top-level directory of this distribution and at | ||
// http://rust-lang.org/COPYRIGHT. | ||
// | ||
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or | ||
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license | ||
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your | ||
// option. This file may not be copied, modified, or distributed | ||
// except according to those terms. | ||
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// revisions: lxl nll | ||
//[lxl]compile-flags: -Z borrowck=mir -Z two-phase-borrows | ||
//[nll]compile-flags: -Z borrowck=mir -Z two-phase-borrows -Z nll | ||
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// This is a corner case that the current implementation is (probably) | ||
// treating more conservatively than is necessary. But it also does | ||
// not seem like a terribly important use case to cover. | ||
// | ||
// So this test is just making a note of the current behavior, with | ||
// the caveat that in the future, the rules may be loosened, at which | ||
// point this test might be thrown out. | ||
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fn main() { | ||
let mut vec = vec![0, 1]; | ||
let delay: &mut Vec<_>; | ||
{ | ||
let shared = &vec; | ||
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// we reserve here, which could (on its own) be compatible | ||
// with the shared borrow. But in the current implementation, | ||
// its an error. | ||
delay = &mut vec; | ||
//[lxl]~^ ERROR cannot borrow `vec` as mutable because it is also borrowed as immutable | ||
//[nll]~^^ ERROR cannot borrow `vec` as mutable because it is also borrowed as immutable | ||
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shared[0]; | ||
} | ||
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// the &mut-borrow only becomes active way down here. | ||
// | ||
// (At least in theory; part of the reason this test fails is that | ||
// the constructed MIR throws in extra &mut reborrows which | ||
// flummoxes our attmpt to delay the activation point here.) | ||
delay.push(2); | ||
} | ||
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