tests/ui/unnecessary_operation.rs

#![allow(
    clippy::deref_addrof,
    clippy::no_effect,
    clippy::uninlined_format_args,
    clippy::unnecessary_struct_initialization,
    dead_code,
    unused
)]
#![warn(clippy::unnecessary_operation)]

use std::fmt::Display;
use std::ops::Shl;

struct Tuple(i32);
struct Struct {
    field: i32,
}
enum Enum {
    Tuple(i32),
    Struct { field: i32 },
}
struct DropStruct {
    field: i32,
}
impl Drop for DropStruct {
    fn drop(&mut self) {}
}
struct DropTuple(i32);
impl Drop for DropTuple {
    fn drop(&mut self) {}
}
enum DropEnum {
    Tuple(i32),
    Struct { field: i32 },
}
impl Drop for DropEnum {
    fn drop(&mut self) {}
}
struct FooString {
    s: String,
}

fn get_number() -> i32 {
    0
}

const fn get_usize() -> usize {
    0
}
fn get_struct() -> Struct {
    Struct { field: 0 }
}
fn get_drop_struct() -> DropStruct {
    DropStruct { field: 0 }
}

struct Cout;

impl<T> Shl<T> for Cout
where
    T: Display,
{
    type Output = Self;
    fn shl(self, rhs: T) -> Self::Output {
        println!("{}", rhs);
        self
    }
}

fn main() {
    Tuple(get_number());
    //~^ unnecessary_operation
    Struct { field: get_number() };
    //~^ unnecessary_operation
    Struct { ..get_struct() };
    //~^ unnecessary_operation
    Enum::Tuple(get_number());
    //~^ unnecessary_operation
    Enum::Struct { field: get_number() };
    //~^ unnecessary_operation
    5 + get_number();
    //~^ unnecessary_operation
    *&get_number();
    //~^ unnecessary_operation
    &get_number();
    //~^ unnecessary_operation
    (5, 6, get_number());
    //~^ unnecessary_operation
    get_number()..;
    //~^ unnecessary_operation
    ..get_number();
    //~^ unnecessary_operation
    5..get_number();
    //~^ unnecessary_operation
    [42, get_number()];
    //~^ unnecessary_operation
    [42, 55][get_usize()];
    //~^ unnecessary_operation
    (42, get_number()).1;
    //~^ unnecessary_operation
    [get_number(); 55];
    //~^ unnecessary_operation
    [42; 55][get_usize()];
    //~^ unnecessary_operation
    {
        //~^ unnecessary_operation
        get_number()
    };
    FooString {
        //~^ unnecessary_operation
        s: String::from("blah"),
    };

    // Do not warn
    DropTuple(get_number());
    DropStruct { field: get_number() };
    DropStruct { field: get_number() };
    DropStruct { ..get_drop_struct() };
    DropEnum::Tuple(get_number());
    DropEnum::Struct { field: get_number() };

    // Issue #9954
    fn one() -> i8 {
        1
    }
    macro_rules! use_expr {
        ($($e:expr),*) => {{ $($e;)* }}
    }
    use_expr!(isize::MIN / -(one() as isize), i8::MIN / -one());

    // Issue #11885
    Cout << 16;

    // Issue #11575
    // Bad formatting is required to trigger the bug
    #[rustfmt::skip]
    'label: {
        break 'label
    };
    let () = const {
        [42, 55][get_usize()];
    };
}

const _: () = {
    [42, 55][get_usize()];
};

const fn foo() {
    [42, 55][get_usize()];
    //~^ unnecessary_operation
}

fn issue15173() {
    // No lint as `Box::new(None)` alone would be ambiguous
    Box::new(None) as Box<Option<i32>>;
}

#[expect(clippy::redundant_closure_call)]
fn issue15173_original<MsU>(handler: impl FnOnce() -> MsU + Clone + 'static) {
    Box::new(move |value| {
        (|_| handler.clone()())(value);
        None
    }) as Box<dyn Fn(i32) -> Option<i32>>;
}