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|
// Edition 2024 lint for change in drop order at tail expression
// This lint is to capture potential change in program semantics
// due to implementation of RFC 3606 <https://github.com/rust-lang/rfcs/pull/3606>
//@ edition: 2021
#![deny(tail_expr_drop_order)] //~ NOTE: the lint level is defined here
#![allow(dropping_copy_types)]
struct LoudDropper;
impl Drop for LoudDropper {
//~^ NOTE: `#1` invokes this custom destructor
//~| NOTE: `x` invokes this custom destructor
//~| NOTE: `#1` invokes this custom destructor
//~| NOTE: `x` invokes this custom destructor
//~| NOTE: `#1` invokes this custom destructor
//~| NOTE: `x` invokes this custom destructor
//~| NOTE: `#1` invokes this custom destructor
//~| NOTE: `x` invokes this custom destructor
//~| NOTE: `#1` invokes this custom destructor
//~| NOTE: `_x` invokes this custom destructor
//~| NOTE: `#1` invokes this custom destructor
fn drop(&mut self) {
// This destructor should be considered significant because it is a custom destructor
// and we will assume that the destructor can generate side effects arbitrarily so that
// a change in drop order is visible.
println!("loud drop");
}
}
impl LoudDropper {
fn get(&self) -> i32 {
0
}
}
fn should_lint() -> i32 {
let x = LoudDropper;
//~^ NOTE: `x` calls a custom destructor
//~| NOTE: `x` will be dropped later as of Edition 2024
// Should lint
x.get() + LoudDropper.get()
//~^ ERROR: relative drop order changing in Rust 2024
//~| NOTE: this value will be stored in a temporary; let us call it `#1`
//~| NOTE: up until Edition 2021 `#1` is dropped last but will be dropped earlier in Edition 2024
//~| WARN: this changes meaning in Rust 2024
//~| NOTE: most of the time, changing drop order is harmless; inspect the `impl Drop`s for side effects
//~| NOTE: for more information, see
}
//~^ NOTE: now the temporary value is dropped here, before the local variables in the block or statement
fn should_not_lint_closure() -> impl FnOnce() -> i32 {
let x = LoudDropper;
move || {
// Should not lint because ...
x.get() + LoudDropper.get()
}
// ^ closure captures like `x` are always dropped last by contract
}
fn should_lint_in_nested_items() {
fn should_lint_me() -> i32 {
let x = LoudDropper;
//~^ NOTE: `x` calls a custom destructor
//~| NOTE: `x` will be dropped later as of Edition 2024
// Should lint
x.get() + LoudDropper.get()
//~^ ERROR: relative drop order changing in Rust 2024
//~| NOTE: this value will be stored in a temporary; let us call it `#1`
//~| NOTE: up until Edition 2021 `#1` is dropped last but will be dropped earlier in Edition 2024
//~| WARN: this changes meaning in Rust 2024
//~| NOTE: most of the time, changing drop order is harmless; inspect the `impl Drop`s for side effects
//~| NOTE: for more information, see
}
//~^ NOTE: now the temporary value is dropped here, before the local variables in the block or statement
}
fn should_not_lint_params(x: LoudDropper) -> i32 {
// Should not lint because ...
x.get() + LoudDropper.get()
}
// ^ function parameters like `x` are always dropped last
fn should_not_lint() -> i32 {
let x = LoudDropper;
// Should not lint
x.get()
}
fn should_lint_in_nested_block() -> i32 {
let x = LoudDropper;
//~^ NOTE: `x` calls a custom destructor
//~| NOTE: `x` will be dropped later as of Edition 2024
{ LoudDropper.get() }
//~^ ERROR: relative drop order changing in Rust 2024
//~| NOTE: this value will be stored in a temporary; let us call it `#1`
//~| NOTE: up until Edition 2021 `#1` is dropped last but will be dropped earlier in Edition 2024
//~| WARN: this changes meaning in Rust 2024
//~| NOTE: most of the time, changing drop order is harmless; inspect the `impl Drop`s for side effects
//~| NOTE: for more information, see
}
//~^ NOTE: now the temporary value is dropped here, before the local variables in the block or statement
fn should_not_lint_in_match_arm() -> i32 {
let x = LoudDropper;
// Should not lint because Edition 2021 drops temporaries in blocks earlier already
match &x {
_ => LoudDropper.get(),
}
}
fn should_not_lint_when_consumed() -> (LoudDropper, i32) {
let x = LoudDropper;
// Should not lint because `LoudDropper` is consumed by the return value
(LoudDropper, x.get())
}
struct MyAdt {
a: LoudDropper,
b: LoudDropper,
}
fn should_not_lint_when_consumed_in_ctor() -> MyAdt {
let a = LoudDropper;
// Should not lint
MyAdt { a, b: LoudDropper }
}
fn should_not_lint_when_moved() -> i32 {
let x = LoudDropper;
drop(x);
// Should not lint because `x` is not live
LoudDropper.get()
}
fn should_lint_into_async_body() -> i32 {
async fn f() {
async fn f() {}
let x = LoudDropper;
f().await;
drop(x);
}
let future = f();
//~^ NOTE: `future` calls a custom destructor
//~| NOTE: `future` will be dropped later as of Edition 2024
LoudDropper.get()
//~^ ERROR: relative drop order changing in Rust 2024
//~| WARN: this changes meaning in Rust 2024
//~| NOTE: this value will be stored in a temporary; let us call it `#1`
//~| NOTE: up until Edition 2021 `#1` is dropped last but will be dropped earlier in Edition 2024
//~| NOTE: most of the time, changing drop order is harmless; inspect the `impl Drop`s for side effects
//~| NOTE: for more information, see
}
//~^ NOTE: now the temporary value is dropped here, before the local variables in the block or statement
fn should_lint_generics<T: Default>() -> &'static str {
fn extract<T>(_: &T) -> &'static str {
todo!()
}
let x = T::default();
//~^ NOTE: `x` calls a custom destructor
//~| NOTE: `x` will be dropped later as of Edition 2024
extract(&T::default())
//~^ ERROR: relative drop order changing in Rust 2024
//~| WARN: this changes meaning in Rust 2024
//~| NOTE: this value will be stored in a temporary; let us call it `#1`
//~| NOTE: up until Edition 2021 `#1` is dropped last but will be dropped earlier in Edition 2024
//~| NOTE: most of the time, changing drop order is harmless; inspect the `impl Drop`s for side effects
//~| NOTE: for more information, see
}
//~^ NOTE: now the temporary value is dropped here, before the local variables in the block or statement
fn should_lint_adt() -> i32 {
let x: Result<LoudDropper, ()> = Ok(LoudDropper);
//~^ NOTE: `x` calls a custom destructor
//~| NOTE: `x` will be dropped later as of Edition 2024
LoudDropper.get()
//~^ ERROR: relative drop order changing in Rust 2024
//~| WARN: this changes meaning in Rust 2024
//~| NOTE: this value will be stored in a temporary; let us call it `#1`
//~| NOTE: up until Edition 2021 `#1` is dropped last but will be dropped earlier in Edition 2024
//~| NOTE: most of the time, changing drop order is harmless; inspect the `impl Drop`s for side effects
//~| NOTE: for more information, see
}
//~^ NOTE: now the temporary value is dropped here, before the local variables in the block or statement
fn should_not_lint_insign_dtor() -> i32 {
let x = String::new();
LoudDropper.get()
}
fn should_lint_with_dtor_span() -> i32 {
struct LoudDropper3;
impl Drop for LoudDropper3 {
//~^ NOTE: `#1` invokes this custom destructor
fn drop(&mut self) {
println!("loud drop");
}
}
impl LoudDropper3 {
fn get(&self) -> i32 {
0
}
}
struct LoudDropper2;
impl Drop for LoudDropper2 {
//~^ NOTE: `x` invokes this custom destructor
fn drop(&mut self) {
println!("loud drop");
}
}
impl LoudDropper2 {
fn get(&self) -> i32 {
0
}
}
let x = LoudDropper2;
//~^ NOTE: `x` calls a custom destructor
//~| NOTE: `x` will be dropped later as of Edition 2024
LoudDropper3.get()
//~^ ERROR: relative drop order changing in Rust 2024
//~| NOTE: this value will be stored in a temporary; let us call it `#1`
//~| NOTE: up until Edition 2021 `#1` is dropped last but will be dropped earlier in Edition 2024
//~| WARN: this changes meaning in Rust 2024
//~| NOTE: most of the time, changing drop order is harmless; inspect the `impl Drop`s for side effects
//~| NOTE: for more information, see
}
//~^ NOTE: now the temporary value is dropped here, before the local variables in the block or statement
fn should_lint_with_transient_drops() {
drop((
{
LoudDropper.get()
//~^ ERROR: relative drop order changing in Rust 2024
//~| NOTE: this value will be stored in a temporary; let us call it `#1`
//~| NOTE: up until Edition 2021 `#1` is dropped last but will be dropped earlier in Edition 2024
//~| WARN: this changes meaning in Rust 2024
//~| NOTE: most of the time, changing drop order is harmless; inspect the `impl Drop`s for side effects
//~| NOTE: for more information, see
},
{
let _x = LoudDropper;
//~^ NOTE: `_x` calls a custom destructor
//~| NOTE: `_x` will be dropped later as of Edition 2024
},
));
//~^ NOTE: now the temporary value is dropped here, before the local variables in the block or statement
}
fn main() {}
|
