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25 lines
560 B
Rust
25 lines
560 B
Rust
#[derive(Copy, Clone, Debug, Eq, PartialEq)]
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pub struct Foo {
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}
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impl Foo {
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fn get(&self) -> Option<&Result<String, String>> {
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None
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}
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fn mutate(&mut self) { }
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}
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fn main() {
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let mut foo = Foo { };
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// foo.get() returns type Option<&Result<String, String>>, so
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// using `string` keeps borrow of `foo` alive. Hence calling
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// `foo.mutate()` should be an error.
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while let Some(Ok(string)) = foo.get() {
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foo.mutate();
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//~^ ERROR cannot borrow `foo` as mutable
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println!("foo={:?}", *string);
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}
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}
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