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Unit tests for issue rust-lang#54556. Some were also taken from issues rust-lang#21114, rust-lang#46413.
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‎src/test/ui/nll/issue-21114-ebfull.rs

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// (this works, but only in NLL)
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// compile-pass
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#![feature(nll)]
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use std::collections::HashMap;
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use std::sync::Mutex;
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fn i_used_to_be_able_to(foo: &Mutex<HashMap<usize, usize>>) -> Vec<(usize, usize)> {
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let mut foo = foo.lock().unwrap();
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foo.drain().collect()
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}
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fn but_after_nightly_update_now_i_gotta(foo: &Mutex<HashMap<usize, usize>>) -> Vec<(usize, usize)> {
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let mut foo = foo.lock().unwrap();
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return foo.drain().collect();
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}
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fn main() {}

‎src/test/ui/nll/issue-21114-kixunil.rs

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// (this works, but only in NLL)
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// compile-pass
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#![feature(nll)]
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fn from_stdin(min: u64) -> Vec<u64> {
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use std::io::BufRead;
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let stdin = std::io::stdin();
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let stdin = stdin.lock();
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stdin.lines()
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.map(Result::unwrap)
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.map(|val| val.parse())
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.map(Result::unwrap)
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.filter(|val| *val >= min)
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.collect()
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}
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fn main() {}

‎src/test/ui/nll/issue-54556-niconii.nll.stderr

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error[E0597]: `counter` does not live long enough
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--> $DIR/issue-54556-niconii.rs:22:20
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|
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LL | if let Ok(_) = counter.lock() { }
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| ^^^^^^^-------
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| |
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| borrowed value does not live long enough
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| a temporary with access to the borrow is created here ...
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...
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LL | }
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| -
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| |
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| `counter` dropped here while still borrowed
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| ... and the borrow might be used here, when that temporary is dropped and runs the destructor for type `std::result::Result<MutexGuard<'_>, ()>`
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|
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= note: The temporary is part of an expression at the end of a block. Consider adding semicolon after the expression so its temporaries are dropped sooner, before the local variables declared by the block are dropped.
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error: aborting due to previous error
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For more information about this error, try `rustc --explain E0597`.

‎src/test/ui/nll/issue-54556-niconii.rs

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// This is a reduction of a concrete test illustrating a case that was
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// annoying to Rust developer niconii (see comment thread on #21114).
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//
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// With resolving issue #54556, pnkfelix hopes that the new diagnostic
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// output produced by NLL helps to *explain* the semantic significance
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// of temp drop order, and thus why inserting a semi-colon after the
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// `if let` expression in `main` works.
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struct Mutex;
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struct MutexGuard<'a>(&'a Mutex);
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impl Drop for Mutex { fn drop(&mut self) { println!("Mutex::drop"); } }
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impl<'a> Drop for MutexGuard<'a> { fn drop(&mut self) { println!("MutexGuard::drop"); } }
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impl Mutex {
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fn lock(&self) -> Result<MutexGuard, ()> { Ok(MutexGuard(self)) }
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}
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fn main() {
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let counter = Mutex;
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if let Ok(_) = counter.lock() { }
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// With this code as written, the dynamic semantics here implies
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// that `Mutex::drop` for `counter` runs *before*
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// `MutexGuard::drop`, which would be unsound since `MutexGuard`
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// still has a reference to `counter`.
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//
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// The goal of #54556 is to explain that within a compiler
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// diagnostic.
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}

‎src/test/ui/nll/issue-54556-niconii.stderr

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error[E0597]: `counter` does not live long enough
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--> $DIR/issue-54556-niconii.rs:22:20
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|
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LL | if let Ok(_) = counter.lock() { }
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| ^^^^^^^ borrowed value does not live long enough
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...
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LL | }
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| - `counter` dropped here while still borrowed
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|
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= note: values in a scope are dropped in the opposite order they are created
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error: aborting due to previous error
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For more information about this error, try `rustc --explain E0597`.

‎src/test/ui/nll/issue-54556-stephaneyfx.nll.stderr

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error[E0597]: `stmt` does not live long enough
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--> $DIR/issue-54556-stephaneyfx.rs:27:21
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|
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LL | let rows = Rows(&stmt);
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| ^^^^^ borrowed value does not live long enough
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LL | rows.map(|row| row).next()
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| ------------------- a temporary with access to the borrow is created here ...
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...
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LL | }
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| -
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| |
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| `stmt` dropped here while still borrowed
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| ... and the borrow might be used here, when that temporary is dropped and runs the destructor for type `std::iter::Map<Rows<'_>, [closure@$DIR/issue-54556-stephaneyfx.rs:28:14: 28:23]>`
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|
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= note: The temporary is part of an expression at the end of a block. Consider forcing this temporary to be dropped sooner, before the block's local variables are dropped. For example, you could save the expression's value in a new local variable `x` and then make `x` be the expression at the end of the block.
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error: aborting due to previous error
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For more information about this error, try `rustc --explain E0597`.

‎src/test/ui/nll/issue-54556-stephaneyfx.rs

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// This is a reduction of a concrete test illustrating a case that was
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// annoying to Rust developer stephaneyfx (see issue #46413).
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//
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// With resolving issue #54556, pnkfelix hopes that the new diagnostic
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// output produced by NLL helps to *explain* the semantic significance
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// of temp drop order, and thus why storing the result in `x` and then
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// returning `x` works.
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pub struct Statement;
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pub struct Rows<'stmt>(&'stmt Statement);
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impl<'stmt> Drop for Rows<'stmt> {
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fn drop(&mut self) {}
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}
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impl<'stmt> Iterator for Rows<'stmt> {
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type Item = String;
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fn next(&mut self) -> Option<Self::Item> {
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None
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}
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}
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fn get_names() -> Option<String> {
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let stmt = Statement;
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let rows = Rows(&stmt);
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rows.map(|row| row).next()
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// let x = rows.map(|row| row).next();
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// x
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//
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// Removing the map works too as does removing the Drop impl.
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}
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fn main() {}

‎src/test/ui/nll/issue-54556-stephaneyfx.stderr

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error[E0597]: `stmt` does not live long enough
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--> $DIR/issue-54556-stephaneyfx.rs:27:22
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|
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LL | let rows = Rows(&stmt);
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| ^^^^ borrowed value does not live long enough
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...
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LL | }
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| - `stmt` dropped here while still borrowed
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|
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= note: values in a scope are dropped in the opposite order they are created
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error: aborting due to previous error
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For more information about this error, try `rustc --explain E0597`.

‎src/test/ui/nll/issue-54556-temps-in-tail-diagnostic.nll.stderr

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error[E0597]: `_thing1` does not live long enough
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--> $DIR/issue-54556-temps-in-tail-diagnostic.rs:5:11
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|
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LL | D(&_thing1).end()
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| --^^^^^^^^-
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| | |
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| | borrowed value does not live long enough
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| a temporary with access to the borrow is created here ...
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LL | }
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| - `_thing1` dropped here while still borrowed
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LL |
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LL | ;
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| - ... and the borrow might be used here, when that temporary is dropped and runs the `Drop` code for type `D`
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|
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= note: The temporary is part of an expression at the end of a block. Consider adding semicolon after the expression so its temporaries are dropped sooner, before the local variables declared by the block are dropped.
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error: aborting due to previous error
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For more information about this error, try `rustc --explain E0597`.

‎src/test/ui/nll/issue-54556-temps-in-tail-diagnostic.rs

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fn main() {
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{
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let mut _thing1 = D(Box::new("thing1"));
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// D("other").next(&_thing1).end()
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D(&_thing1).end()
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}
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;
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}
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#[derive(Debug)]
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struct D<T: std::fmt::Debug>(T);
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impl<T: std::fmt::Debug> Drop for D<T> {
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fn drop(&mut self) {
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println!("dropping {:?})", self);
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}
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}
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impl<T: std::fmt::Debug> D<T> {
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fn next<U: std::fmt::Debug>(&self, _other: U) -> D<U> { D(_other) }
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fn end(&self) { }
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}

‎src/test/ui/nll/issue-54556-temps-in-tail-diagnostic.stderr

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error[E0597]: `_thing1` does not live long enough
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--> $DIR/issue-54556-temps-in-tail-diagnostic.rs:5:12
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|
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LL | D(&_thing1).end()
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| ^^^^^^^ borrowed value does not live long enough
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LL | }
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| - `_thing1` dropped here while still borrowed
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LL |
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LL | ;
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| - borrowed value needs to live until here
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error: aborting due to previous error
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For more information about this error, try `rustc --explain E0597`.

‎src/test/ui/nll/issue-54556-used-vs-unused-tails.nll.stderr

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error[E0597]: `_t1` does not live long enough
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--> $DIR/issue-54556-used-vs-unused-tails.rs:10:55
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|
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LL | { let mut _t1 = D(Box::new("t1")); D(&_t1).end() } ; // suggest `;`
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| --^^^^- - - ... and the borrow might be used here, when that temporary is dropped and runs the `Drop` code for type `D`
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| | | |
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| | | `_t1` dropped here while still borrowed
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| | borrowed value does not live long enough
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| a temporary with access to the borrow is created here ...
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|
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= note: The temporary is part of an expression at the end of a block. Consider adding semicolon after the expression so its temporaries are dropped sooner, before the local variables declared by the block are dropped.
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error[E0597]: `_t1` does not live long enough
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--> $DIR/issue-54556-used-vs-unused-tails.rs:12:55
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|
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LL | { { let mut _t1 = D(Box::new("t1")); D(&_t1).end() } } ; // suggest `;`
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| --^^^^- - - ... and the borrow might be used here, when that temporary is dropped and runs the `Drop` code for type `D`
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| | | |
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| | | `_t1` dropped here while still borrowed
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| | borrowed value does not live long enough
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| a temporary with access to the borrow is created here ...
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|
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= note: The temporary is part of an expression at the end of a block. Consider adding semicolon after the expression so its temporaries are dropped sooner, before the local variables declared by the block are dropped.
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error[E0597]: `_t1` does not live long enough
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--> $DIR/issue-54556-used-vs-unused-tails.rs:14:55
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|
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LL | { { let mut _t1 = D(Box::new("t1")); D(&_t1).end() }; } // suggest `;`
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| --^^^^- -- ... and the borrow might be used here, when that temporary is dropped and runs the `Drop` code for type `D`
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| | | |
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| | | `_t1` dropped here while still borrowed
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| | borrowed value does not live long enough
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| a temporary with access to the borrow is created here ...
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|
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= note: The temporary is part of an expression at the end of a block. Consider adding semicolon after the expression so its temporaries are dropped sooner, before the local variables declared by the block are dropped.
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error[E0597]: `_t1` does not live long enough
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--> $DIR/issue-54556-used-vs-unused-tails.rs:16:55
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|
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LL | let _ = { let mut _t1 = D(Box::new("t1")); D(&_t1).end() } ; // suggest `;`
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| --^^^^- - - ... and the borrow might be used here, when that temporary is dropped and runs the `Drop` code for type `D`
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| | | |
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| | | `_t1` dropped here while still borrowed
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| | borrowed value does not live long enough
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| a temporary with access to the borrow is created here ...
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|
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= note: The temporary is part of an expression at the end of a block. Consider adding semicolon after the expression so its temporaries are dropped sooner, before the local variables declared by the block are dropped.
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error[E0597]: `_t1` does not live long enough
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--> $DIR/issue-54556-used-vs-unused-tails.rs:18:55
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|
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LL | let _u = { let mut _t1 = D(Box::new("t1")); D(&_t1).unit() } ; // suggest `;`
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| --^^^^- - - ... and the borrow might be used here, when that temporary is dropped and runs the `Drop` code for type `D`
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| | | |
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| | | `_t1` dropped here while still borrowed
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| | borrowed value does not live long enough
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| a temporary with access to the borrow is created here ...
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|
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= note: The temporary is part of an expression at the end of a block. Consider adding semicolon after the expression so its temporaries are dropped sooner, before the local variables declared by the block are dropped.
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error[E0597]: `_t1` does not live long enough
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--> $DIR/issue-54556-used-vs-unused-tails.rs:20:55
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|
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LL | let _x = { let mut _t1 = D(Box::new("t1")); D(&_t1).end() } ; // `let x = ...; x`
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| --^^^^- - - ... and the borrow might be used here, when that temporary is dropped and runs the `Drop` code for type `D`
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| | | |
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| | | `_t1` dropped here while still borrowed
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| | borrowed value does not live long enough
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| a temporary with access to the borrow is created here ...
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|
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= note: The temporary is part of an expression at the end of a block. Consider forcing this temporary to be dropped sooner, before the block's local variables are dropped. For example, you could save the expression's value in a new local variable `x` and then make `x` be the expression at the end of the block.
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error[E0597]: `_t1` does not live long enough
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--> $DIR/issue-54556-used-vs-unused-tails.rs:24:55
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|
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LL | _y = { let mut _t1 = D(Box::new("t1")); D(&_t1).end() } ; // `let x = ...; x`
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| --^^^^- - - ... and the borrow might be used here, when that temporary is dropped and runs the `Drop` code for type `D`
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| | | |
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| | | `_t1` dropped here while still borrowed
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| | borrowed value does not live long enough
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| a temporary with access to the borrow is created here ...
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|
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= note: The temporary is part of an expression at the end of a block. Consider forcing this temporary to be dropped sooner, before the block's local variables are dropped. For example, you could save the expression's value in a new local variable `x` and then make `x` be the expression at the end of the block.
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error[E0597]: `_t1` does not live long enough
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--> $DIR/issue-54556-used-vs-unused-tails.rs:30:55
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|
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LL | fn f_local_ref() { let mut _t1 = D(Box::new("t1")); D(&_t1).unit() } // suggest `;`
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| --^^^^- -
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| | | |
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| | | `_t1` dropped here while still borrowed
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| | | ... and the borrow might be used here, when that temporary is dropped and runs the `Drop` code for type `D`
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| | borrowed value does not live long enough
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| a temporary with access to the borrow is created here ...
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|
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= note: The temporary is part of an expression at the end of a block. Consider adding semicolon after the expression so its temporaries are dropped sooner, before the local variables declared by the block are dropped.
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error[E0597]: `_t1` does not live long enough
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--> $DIR/issue-54556-used-vs-unused-tails.rs:32:55
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|
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LL | fn f() -> String { let mut _t1 = D(Box::new("t1")); D(&_t1).end() } // `let x = ...; x`
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| --^^^^- -
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| | | |
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| | | `_t1` dropped here while still borrowed
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| | | ... and the borrow might be used here, when that temporary is dropped and runs the `Drop` code for type `D`
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| | borrowed value does not live long enough
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| a temporary with access to the borrow is created here ...
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|
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= note: The temporary is part of an expression at the end of a block. Consider forcing this temporary to be dropped sooner, before the block's local variables are dropped. For example, you could save the expression's value in a new local variable `x` and then make `x` be the expression at the end of the block.
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error: aborting due to 9 previous errors
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For more information about this error, try `rustc --explain E0597`.

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