add positive and negative tests for temporary scope shortening FCW
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dianne
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5 changed files with 214 additions and 0 deletions
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//! The macros that are in `../user-defined-macros.rs`, but external to test diagnostics.
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//@ edition: 2024
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#[macro_export]
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macro_rules! wrap {
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($arg:expr) => { { &$arg } }
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}
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#[macro_export]
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macro_rules! print_with_internal_wrap {
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() => { println!("{:?}{}", (), $crate::wrap!(String::new())) }
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}
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//! Future-compatibility warning test for #145838: make sure we catch all expected breakage.
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//! Shortening temporaries in the tails of block expressions should warn in Rust 2024, and
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//! shortening temporaries in the tails of `if` expressions' blocks should warn in all editions.
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//@ revisions: e2021 e2024
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//@ [e2021] edition: 2021
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//@ [e2024] edition: 2024
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//@ check-pass
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use std::pin::pin;
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struct Struct { field: () }
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fn cond() -> bool { true }
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fn temp() {}
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fn array_temp() -> [(); 1] { [()] }
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fn tuple_temp() -> ((),) { ((),) }
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fn struct_temp() -> Struct { Struct { field: () } }
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fn smart_ptr_temp() -> Box<()> { Box::new(()) }
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const CONST_STRING: String = String::new();
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static STATIC_UNIT: () = ();
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fn main() {
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let local = String::new();
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// #145880 doesn't apply here, so this `temp()`'s lifetime is reduced by #145838 in Rust 2024.
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println!("{:?}{:?}", { &temp() }, ());
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// TODO: warn in Rust 2024
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// In real-world projects, this breakage typically appeared in `if` expressions with a reference
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// to a `String` temporary in one branch's tail expression. This is edition-independent since
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// `if` expressions' blocks are temporary scopes in all editions.
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println!("{:?}{:?}", (), if cond() { &format!("") } else { "" });
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// TODO: warn in all editions
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println!("{:?}{:?}", (), if cond() { &"".to_string() } else { "" });
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// TODO: warn in all editions
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println!("{:?}{:?}", (), if cond() { &("string".to_owned() + "string") } else { "" });
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// TODO: warn in all editions
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// Make sure we catch indexed and dereferenced temporaries.
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pin!(
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if cond() {
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&array_temp()[0]
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// TODO: warn in all editions
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} else if cond() {
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&tuple_temp().0
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// TODO: warn in all editions
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} else if cond() {
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&struct_temp().field
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// TODO: warn in all editions
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} else {
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&*&*smart_ptr_temp()
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// TODO: warn in all editions
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}
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);
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// Test that `super let` extended by parent `super let`s in non-extending blocks are caught.
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pin!(pin!({ &temp() }));
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// TODO: warn in Rust 2024
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// We shouldn't warn when lifetime extension applies.
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let _ = format_args!("{:?}{:?}", { &temp() }, if cond() { &temp() } else { &temp() });
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let _ = pin!(
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if cond() {
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&array_temp()[0]
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} else if cond() {
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&tuple_temp().0
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} else if cond() {
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&struct_temp().field
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} else {
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&*&*smart_ptr_temp()
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}
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);
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let _ = pin!(pin!({ &temp() }));
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// We shouldn't warn when borrowing from non-temporary places.
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pin!({ &local });
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pin!({ &STATIC_UNIT });
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// We shouldn't warn for promoted constants.
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pin!({ &size_of::<()>() });
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pin!({ &(1 / 1) });
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pin!({ &mut ([] as [(); 0]) });
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pin!({ &None::<String> });
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pin!({ &|| String::new() });
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// But we do warn on these temporaries, since they aren't promoted.
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pin!({ &(1 / 0) });
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// TODO: warn in Rust 2024
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pin!({ &mut [()] });
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// TODO: warn in Rust 2024
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pin!({ &Some(String::new()) });
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// TODO: warn in Rust 2024
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pin!({ &(|| ())() });
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// TODO: warn in Rust 2024
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pin!({ &|| &local });
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// TODO: warn in Rust 2024
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pin!({ &CONST_STRING });
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// TODO: warn in Rust 2024
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// This lint only catches future errors. Future dangling pointers do not produce warnings.
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pin!({ &raw const *&temp() });
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}
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//! Test that `macro_extended_temporary_scopes` doesn't warn on non-extended temporaries.
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//@ edition: 2024
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#![deny(macro_extended_temporary_scopes)] //~ WARN unknown lint
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fn temp() {}
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fn main() {
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// Due to #145880, this argument isn't an extending context.
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println!("{:?}", { &temp() });
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//~^ ERROR temporary value dropped while borrowed
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// Subexpressions of function call expressions are not extending.
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println!("{:?}{:?}", (), { std::convert::identity(&temp()) });
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//~^ ERROR temporary value dropped while borrowed
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}
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warning: unknown lint: `macro_extended_temporary_scopes`
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--> $DIR/non-extended.rs:3:9
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LL | #![deny(macro_extended_temporary_scopes)]
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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= note: `#[warn(unknown_lints)]` on by default
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error[E0716]: temporary value dropped while borrowed
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--> $DIR/non-extended.rs:9:25
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LL | println!("{:?}", { &temp() });
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| ---^^^^^---
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| | | |
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| | | temporary value is freed at the end of this statement
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| | creates a temporary value which is freed while still in use
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| borrow later used here
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= note: consider using a `let` binding to create a longer lived value
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error[E0716]: temporary value dropped while borrowed
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--> $DIR/non-extended.rs:13:56
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LL | println!("{:?}{:?}", (), { std::convert::identity(&temp()) });
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| --------------------------^^^^^^---
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| | | |
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| | | temporary value is freed at the end of this statement
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| | creates a temporary value which is freed while still in use
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| borrow later used here
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= note: consider using a `let` binding to create a longer lived value
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error: aborting due to 2 previous errors; 1 warning emitted
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For more information about this error, try `rustc --explain E0716`.
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@ -0,0 +1,50 @@
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//! Test that the future-compatibility warning for #145838 doesn't break in the presence of
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//! user-defined macros.
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//@ build-pass
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//@ edition: 2024
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//@ aux-build:external-macros.rs
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//@ dont-require-annotations: NOTE
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extern crate external_macros;
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macro_rules! wrap {
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($arg:expr) => { { &$arg } }
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}
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macro_rules! print_with_internal_wrap {
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() => { println!("{:?}{}", (), wrap!(String::new())) }
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}
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fn main() {
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print!(
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"{:?}{}",
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(),
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format_args!(
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"{:?}{:?}",
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// This is promoted; do not warn.
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wrap!(None::<String>),
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// This does not promote; warn.
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wrap!(String::new())
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// TODO: warn
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)
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);
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print_with_internal_wrap!();
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// TODO: warn
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print!(
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"{:?}{:?}",
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// This is promoted; do not warn.
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external_macros::wrap!(None::<String>),
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// This does not promote; warn.
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external_macros::wrap!(String::new())
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// TODO: warn
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);
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external_macros::print_with_internal_wrap!();
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// TODO: warn
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}
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