Remove unused #[must_use]

[compiler-errors]

Self-explanatory

Fixes #145257

[rustbot]

r? @wesleywiser

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[rustbot]

Some changes occurred in compiler/rustc_passes/src/check_attr.rs

cc @jdonszelmann

[compiler-errors]

@run-rustfix requires that all warnings are gone, and foo is unused, so I'm suppressing it here.

[fmease]

Thenks!~

r? fmease @bors r+ rollup

[bors]

📌 Commit 6c571e7 has been approved by fmease

It is now in the queue for this repository.

[rust-log-analyzer]

The job aarch64-gnu-llvm-19-1 failed! Check out the build log: (web) (plain enhanced) (plain)

Click to see the possible cause of the failure (guessed by this bot)

#![allow(dead_code, path_statements)]
#![deny(unused_attributes, unused_must_use)]
#![feature(asm_experimental_arch, stmt_expr_attributes, trait_alias)]

 //~ ERROR `#[must_use]` has no effect
extern crate std as std2;

 //~ ERROR `#[must_use]` has no effect
mod test_mod {}

 //~ ERROR `#[must_use]` has no effect
use std::arch::global_asm;

 //~ ERROR `#[must_use]` has no effect
const CONST: usize = 4;
 //~ ERROR `#[must_use]` has no effect
#[no_mangle]
static STATIC: usize = 4;

#[must_use]
struct X;
---
union U {
    unit: (),
}

 //~ ERROR `#[must_use]` has no effect
impl U {
    #[must_use]
    fn method() -> i32 {
        4
    }
}

#[must_use]
#[no_mangle]
fn foo() -> i64 {
    4
}

 //~ ERROR `#[must_use]` has no effect
extern "Rust" {
    #[link_name = "STATIC"]
     //~ ERROR `#[must_use]` has no effect
    static FOREIGN_STATIC: usize;

    #[link_name = "foo"]
    #[must_use]
    fn foreign_foo() -> i64;
}

 //~ ERROR unused attribute
global_asm!("");

 //~ ERROR `#[must_use]` has no effect
type UseMe = ();

fn qux< T>(_: T) {} //~ ERROR `#[must_use]` has no effect

#[must_use]
trait Use {
     //~ ERROR `#[must_use]` has no effect
    const ASSOC_CONST: usize = 4;
     //~ ERROR `#[must_use]` has no effect
    type AssocTy;

    #[must_use]
    fn get_four(&self) -> usize {
        4
    }
}

 //~ ERROR `#[must_use]` has no effect
impl Use for () {
    type AssocTy = ();

     //~ ERROR `#[must_use]` has no effect
    fn get_four(&self) -> usize {
        4
    }
}

 //~ ERROR `#[must_use]` has no effect
trait Alias = Use;

 //~ ERROR `#[must_use]` has no effect
macro_rules! cool_macro {
    () => {
        4
    };
}

fn main() {
     //~ ERROR `#[must_use]` has no effect
    let x = || {};
    x();

    let x =  //~ ERROR `#[must_use]` has no effect
    || {};
    x();

    let _ = X; //~ ERROR that must be used
    let _ = Y::Z; //~ ERROR that must be used
    let _ = U { unit: () }; //~ ERROR that must be used
    let _ = U::method(); //~ ERROR that must be used
    let _ = foo(); //~ ERROR that must be used

    unsafe {
        let _ = foreign_foo(); //~ ERROR that must be used
    };

    CONST;
    STATIC;
    unsafe { FOREIGN_STATIC };
    cool_macro!();
    qux(4);
    let _ = ().get_four(); //~ ERROR that must be used

    match Some(4) {
         //~ ERROR `#[must_use]` has no effect
        Some(res) => res,
        None => 0,
    };

    struct PatternField {
        foo: i32,
    }
    let s = PatternField {   foo: 123 }; //~ ERROR `#[must_use]` has no effect
    let PatternField {  foo } = s; //~ ERROR `#[must_use]` has no effect
    let _ = foo;
}



The actual fixed differed from the expected fixed
To update references, rerun the tests and pass the `--bless` flag
To only update this specific test, also pass `--test-args lint/unused/unused_attributes-must_use.rs`

error: 1 errors occurred comparing output.
status: exit status: 1
command: env -u RUSTC_LOG_COLOR RUSTC_ICE="0" RUST_BACKTRACE="short" "/checkout/obj/build/aarch64-unknown-linux-gnu/stage2/bin/rustc" "/checkout/tests/ui/lint/unused/unused_attributes-must_use.rs" "-Zthreads=1" "-Zsimulate-remapped-rust-src-base=/rustc/FAKE_PREFIX" "-Ztranslate-remapped-path-to-local-path=no" "-Z" "ignore-directory-in-diagnostics-source-blocks=/cargo" "-Z" "ignore-directory-in-diagnostics-source-blocks=/checkout/vendor" "--sysroot" "/checkout/obj/build/aarch64-unknown-linux-gnu/stage2" "--target=aarch64-unknown-linux-gnu" "--check-cfg" "cfg(test,FALSE)" "--error-format" "json" "--json" "future-incompat" "-Ccodegen-units=1" "-Zui-testing" "-Zdeduplicate-diagnostics=no" "-Zwrite-long-types-to-disk=no" "-Cstrip=debuginfo" "--emit" "metadata" "-C" "prefer-dynamic" "--out-dir" "/checkout/obj/build/aarch64-unknown-linux-gnu/test/ui/lint/unused/unused_attributes-must_use" "-A" "unused" "-A" "internal_features" "-A" "unused_parens" "-A" "unused_braces" "-Crpath" "-Cdebuginfo=0" "-Lnative=/checkout/obj/build/aarch64-unknown-linux-gnu/native/rust-test-helpers"
stdout: none
--- stderr -------------------------------
error: unused attribute `must_use`
##[error]  --> /checkout/tests/ui/lint/unused/unused_attributes-must_use.rs:60:1
   |
LL | #[must_use] //~ ERROR unused attribute
   | ^^^^^^^^^^^
   |
note: the built-in attribute `must_use` will be ignored, since it's applied to the macro invocation `global_asm`
  --> /checkout/tests/ui/lint/unused/unused_attributes-must_use.rs:61:1
   |
LL | global_asm!("");
   | ^^^^^^^^^^
note: the lint level is defined here
  --> /checkout/tests/ui/lint/unused/unused_attributes-must_use.rs:4:9
   |
LL | #![deny(unused_attributes, unused_must_use)]
   |         ^^^^^^^^^^^^^^^^^

error: `#[must_use]` has no effect when applied to an extern crate
##[error]  --> /checkout/tests/ui/lint/unused/unused_attributes-must_use.rs:7:1
   |
LL | #[must_use] //~ ERROR `#[must_use]` has no effect
   | ^^^^^^^^^^^

error: `#[must_use]` has no effect when applied to a module
##[error]  --> /checkout/tests/ui/lint/unused/unused_attributes-must_use.rs:10:1
   |
LL | #[must_use] //~ ERROR `#[must_use]` has no effect
   | ^^^^^^^^^^^

error: `#[must_use]` has no effect when applied to a use
##[error]  --> /checkout/tests/ui/lint/unused/unused_attributes-must_use.rs:13:1
   |
LL | #[must_use] //~ ERROR `#[must_use]` has no effect
   | ^^^^^^^^^^^

error: `#[must_use]` has no effect when applied to a constant item
##[error]  --> /checkout/tests/ui/lint/unused/unused_attributes-must_use.rs:16:1
   |
LL | #[must_use] //~ ERROR `#[must_use]` has no effect
   | ^^^^^^^^^^^

error: `#[must_use]` has no effect when applied to a static item
##[error]  --> /checkout/tests/ui/lint/unused/unused_attributes-must_use.rs:18:1
   |
LL | #[must_use] //~ ERROR `#[must_use]` has no effect
   | ^^^^^^^^^^^

error: `#[must_use]` has no effect when applied to an inherent implementation block
##[error]  --> /checkout/tests/ui/lint/unused/unused_attributes-must_use.rs:35:1
   |
LL | #[must_use] //~ ERROR `#[must_use]` has no effect
   | ^^^^^^^^^^^

error: `#[must_use]` has no effect when applied to a foreign module
##[error]  --> /checkout/tests/ui/lint/unused/unused_attributes-must_use.rs:49:1
   |
LL | #[must_use] //~ ERROR `#[must_use]` has no effect
   | ^^^^^^^^^^^

error: `#[must_use]` has no effect when applied to a type alias
##[error]  --> /checkout/tests/ui/lint/unused/unused_attributes-must_use.rs:63:1
   |
LL | #[must_use] //~ ERROR `#[must_use]` has no effect
   | ^^^^^^^^^^^

error: `#[must_use]` has no effect when applied to a type parameter
##[error]  --> /checkout/tests/ui/lint/unused/unused_attributes-must_use.rs:66:8
   |
LL | fn qux<#[must_use] T>(_: T) {} //~ ERROR `#[must_use]` has no effect
   |        ^^^^^^^^^^^

error: `#[must_use]` has no effect when applied to an trait implementation block
##[error]  --> /checkout/tests/ui/lint/unused/unused_attributes-must_use.rs:81:1
   |
LL | #[must_use] //~ ERROR `#[must_use]` has no effect
   | ^^^^^^^^^^^

error: `#[must_use]` has no effect when applied to a trait alias
##[error]  --> /checkout/tests/ui/lint/unused/unused_attributes-must_use.rs:91:1
   |
LL | #[must_use] //~ ERROR `#[must_use]` has no effect
   | ^^^^^^^^^^^

error: `#[must_use]` has no effect when applied to a macro def
##[error]  --> /checkout/tests/ui/lint/unused/unused_attributes-must_use.rs:94:1
   |
LL | #[must_use] //~ ERROR `#[must_use]` has no effect
   | ^^^^^^^^^^^

error: `#[must_use]` has no effect when applied to a statement
##[error]  --> /checkout/tests/ui/lint/unused/unused_attributes-must_use.rs:102:5
   |
LL |     #[must_use] //~ ERROR `#[must_use]` has no effect
   |     ^^^^^^^^^^^

error: `#[must_use]` has no effect when applied to a closure
##[error]  --> /checkout/tests/ui/lint/unused/unused_attributes-must_use.rs:106:13
   |
LL |     let x = #[must_use] //~ ERROR `#[must_use]` has no effect
   |             ^^^^^^^^^^^

error: `#[must_use]` has no effect when applied to an match arm
##[error]  --> /checkout/tests/ui/lint/unused/unused_attributes-must_use.rs:128:9
   |
LL |         #[must_use] //~ ERROR `#[must_use]` has no effect
   |         ^^^^^^^^^^^

error: `#[must_use]` has no effect when applied to a struct field
##[error]  --> /checkout/tests/ui/lint/unused/unused_attributes-must_use.rs:136:28
   |
LL |     let s = PatternField { #[must_use]  foo: 123 }; //~ ERROR `#[must_use]` has no effect
   |                            ^^^^^^^^^^^

error: `#[must_use]` has no effect when applied to a pattern field
##[error]  --> /checkout/tests/ui/lint/unused/unused_attributes-must_use.rs:137:24
   |
LL |     let PatternField { #[must_use] foo } = s; //~ ERROR `#[must_use]` has no effect
   |                        ^^^^^^^^^^^

error: `#[must_use]` has no effect when applied to an associated const
##[error]  --> /checkout/tests/ui/lint/unused/unused_attributes-must_use.rs:70:5
   |
LL |     #[must_use] //~ ERROR `#[must_use]` has no effect
   |     ^^^^^^^^^^^

error: `#[must_use]` has no effect when applied to an associated type
##[error]  --> /checkout/tests/ui/lint/unused/unused_attributes-must_use.rs:72:5
   |
LL |     #[must_use] //~ ERROR `#[must_use]` has no effect
   |     ^^^^^^^^^^^

error: `#[must_use]` has no effect when applied to a provided trait method
##[error]  --> /checkout/tests/ui/lint/unused/unused_attributes-must_use.rs:85:5
   |
LL |     #[must_use] //~ ERROR `#[must_use]` has no effect
   |     ^^^^^^^^^^^

error: `#[must_use]` has no effect when applied to a foreign static item
##[error]  --> /checkout/tests/ui/lint/unused/unused_attributes-must_use.rs:52:5
   |
LL |     #[must_use] //~ ERROR `#[must_use]` has no effect
   |     ^^^^^^^^^^^

error: unused `X` that must be used
##[error]  --> /checkout/tests/ui/lint/unused/unused_attributes-must_use.rs:110:5
   |
LL |     X; //~ ERROR that must be used
   |     ^
   |
note: the lint level is defined here
  --> /checkout/tests/ui/lint/unused/unused_attributes-must_use.rs:4:28
   |
LL | #![deny(unused_attributes, unused_must_use)]
   |                            ^^^^^^^^^^^^^^^
help: use `let _ = ...` to ignore the resulting value
   |
LL |     let _ = X; //~ ERROR that must be used
   |     +++++++

error: unused `Y` that must be used
##[error]  --> /checkout/tests/ui/lint/unused/unused_attributes-must_use.rs:111:5
   |
LL |     Y::Z; //~ ERROR that must be used
   |     ^^^^
   |
help: use `let _ = ...` to ignore the resulting value
   |
LL |     let _ = Y::Z; //~ ERROR that must be used
   |     +++++++

error: unused `U` that must be used
##[error]  --> /checkout/tests/ui/lint/unused/unused_attributes-must_use.rs:112:5
   |
LL |     U { unit: () }; //~ ERROR that must be used
   |     ^^^^^^^^^^^^^^
   |
help: use `let _ = ...` to ignore the resulting value
   |
LL |     let _ = U { unit: () }; //~ ERROR that must be used
   |     +++++++

error: unused return value of `U::method` that must be used
##[error]  --> /checkout/tests/ui/lint/unused/unused_attributes-must_use.rs:113:5
   |
LL |     U::method(); //~ ERROR that must be used
   |     ^^^^^^^^^^^
   |
help: use `let _ = ...` to ignore the resulting value
   |
LL |     let _ = U::method(); //~ ERROR that must be used
   |     +++++++

error: unused return value of `foo` that must be used
##[error]  --> /checkout/tests/ui/lint/unused/unused_attributes-must_use.rs:114:5
   |
---

error: unused return value of `foreign_foo` that must be used
##[error]  --> /checkout/tests/ui/lint/unused/unused_attributes-must_use.rs:117:9
   |
LL |         foreign_foo(); //~ ERROR that must be used
   |         ^^^^^^^^^^^^^
   |
help: use `let _ = ...` to ignore the resulting value
   |
LL |         let _ = foreign_foo(); //~ ERROR that must be used
   |         +++++++

error: unused return value of `Use::get_four` that must be used
##[error]  --> /checkout/tests/ui/lint/unused/unused_attributes-must_use.rs:125:5
   |
LL |     ().get_four(); //~ ERROR that must be used
   |     ^^^^^^^^^^^^^
   |
help: use `let _ = ...` to ignore the resulting value
   |
LL |     let _ = ().get_four(); //~ ERROR that must be used
   |     +++++++

error: aborting due to 29 previous errors
------------------------------------------

[fmease]

@bors r-

[compiler-errors]

Will bless when I am back at my computer