46 lines
1.6 KiB
Rust
46 lines
1.6 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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struct point { x: int, y: int }
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fn a() {
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let mut p = point {x: 3, y: 4};
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let _q = &p; //~ NOTE loan of mutable local variable granted here
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// This assignment is illegal because the field x is not
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// inherently mutable; since `p` was made immutable, `p.x` is now
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// immutable. Otherwise the type of &_q.x (&int) would be wrong.
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p.x = 5; //~ ERROR assigning to mutable field prohibited due to outstanding loan
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}
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fn c() {
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// this is sort of the opposite. We take a loan to the interior of `p`
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// and then try to overwrite `p` as a whole.
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let mut p = point {x: 3, y: 4};
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let _q = &p.y; //~ NOTE loan of mutable local variable granted here
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p = point {x: 5, y: 7};//~ ERROR assigning to mutable local variable prohibited due to outstanding loan
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copy p;
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}
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fn d() {
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// just for completeness's sake, the easy case, where we take the
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// address of a subcomponent and then modify that subcomponent:
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let mut p = point {x: 3, y: 4};
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let _q = &p.y; //~ NOTE loan of mutable field granted here
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p.y = 5; //~ ERROR assigning to mutable field prohibited due to outstanding loan
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copy p;
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}
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fn main() {
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}
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