mirror of https://github.com/rust-lang/rust
35 lines
922 B
Rust
35 lines
922 B
Rust
#![feature(thin_box)]
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//@ run-pass
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use std::boxed::ThinBox;
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use std::error::Error;
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use std::{fmt, mem};
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use std::ops::DerefMut;
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const EXPECTED: &str = "boooo!";
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fn main() {
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let thin_error: ThinBox<dyn Error> = ThinBox::new_unsize(Foo);
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assert_eq!(mem::size_of::<*const i32>(), mem::size_of_val(&thin_error));
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let msg = thin_error.to_string();
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assert_eq!(EXPECTED, msg);
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let mut thin_concrete_error: ThinBox<Foo> = ThinBox::new(Foo);
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assert_eq!(mem::size_of::<*const i32>(), mem::size_of_val(&thin_concrete_error));
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let msg = thin_concrete_error.to_string();
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assert_eq!(EXPECTED, msg);
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let inner = thin_concrete_error.deref_mut();
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let msg = inner.to_string();
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assert_eq!(EXPECTED, msg);
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}
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#[derive(Debug)]
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struct Foo;
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impl fmt::Display for Foo {
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fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
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write!(f, "{}", EXPECTED)
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}
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}
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impl Error for Foo {}
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