rust/tests/ui/nll/issue-54556-used-vs-unused-tails.rs

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// This test case is exploring the space of how blocks with tail
// expressions and statements can be composed, trying to keep each
// case on one line so that we can compare them via a vertical scan
// with the human eye.
// Each comment on the right side of the line is summarizing the
// expected suggestion from the diagnostic for issue #54556.
fn main() {
{ let mut _t1 = D(Box::new("t1")); D(&_t1).end() } ; // suggest `;`
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//~^ ERROR does not live long enough
{ { let mut _t1 = D(Box::new("t1")); D(&_t1).end() } } ; // suggest `;`
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//~^ ERROR does not live long enough
{ { let mut _t1 = D(Box::new("t1")); D(&_t1).end() }; } // suggest `;`
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//~^ ERROR does not live long enough
let _ = { let mut _t1 = D(Box::new("t1")); D(&_t1).end() } ; // suggest `;`
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//~^ ERROR does not live long enough
let _u = { let mut _t1 = D(Box::new("t1")); D(&_t1).unit() } ; // suggest `;`
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//~^ ERROR does not live long enough
let _x = { let mut _t1 = D(Box::new("t1")); D(&_t1).end() } ; // `let x = ...; x`
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//~^ ERROR does not live long enough
let _x = { let mut _t1 = D(Box::new("t1")); let x = D(&_t1).end(); x } ; // no error
let mut _y;
_y = { let mut _t1 = D(Box::new("t1")); D(&_t1).end() } ; // `let x = ...; x`
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//~^ ERROR does not live long enough
_y = { let mut _t1 = D(Box::new("t1")); let x = D(&_t1).end(); x } ; // no error
}
fn f_param_ref(_t1: D<Box<&'static str>>) { D(&_t1).unit() } // no error
fn f_local_ref() { let mut _t1 = D(Box::new("t1")); D(&_t1).unit() } // suggest `;`
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//~^ ERROR does not live long enough
fn f() -> String { let mut _t1 = D(Box::new("t1")); D(&_t1).end() } // `let x = ...; x`
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//~^ ERROR does not live long enough
#[derive(Debug)]
struct D<T: std::fmt::Debug>(T);
impl<T: std::fmt::Debug> Drop for D<T> {
fn drop(&mut self) {
println!("dropping {:?})", self);
}
}
impl<T: std::fmt::Debug> D<T> {
fn next<U: std::fmt::Debug>(&self, _other: U) -> D<U> { D(_other) }
fn end(&self) -> String { format!("End({:?})", self.0) }
fn unit(&self) { }
}