rust-clippy/tests/ui/drop_forget_ref.rs

#![warn(clippy::drop_ref, clippy::forget_ref)]
#![allow(clippy::toplevel_ref_arg, clippy::similar_names, clippy::needless_pass_by_value)]

use std::mem::{drop, forget};

struct SomeStruct;

fn main() {
    drop(&SomeStruct);
    forget(&SomeStruct);

    let mut owned1 = SomeStruct;
    drop(&owned1);
    drop(&&owned1);
    drop(&mut owned1);
    drop(owned1); //OK
    let mut owned2 = SomeStruct;
    forget(&owned2);
    forget(&&owned2);
    forget(&mut owned2);
    forget(owned2); //OK

    let reference1 = &SomeStruct;
    drop(reference1);
    forget(&*reference1);

    let reference2 = &mut SomeStruct;
    drop(reference2);
    let reference3 = &mut SomeStruct;
    forget(reference3);

    let ref reference4 = SomeStruct;
    drop(reference4);
    forget(reference4);
}

#[allow(dead_code)]
fn test_generic_fn_drop<T>(val: T) {
    drop(&val);
    drop(val); //OK
}

#[allow(dead_code)]
fn test_generic_fn_forget<T>(val: T) {
    forget(&val);
    forget(val); //OK
}

#[allow(dead_code)]
fn test_similarly_named_function() {
    fn drop<T>(_val: T) {}
    drop(&SomeStruct); //OK; call to unrelated function which happens to have the same name
    std::mem::drop(&SomeStruct);
    fn forget<T>(_val: T) {}
    forget(&SomeStruct); //OK; call to unrelated function which happens to have the same name
    std::mem::forget(&SomeStruct);
}

#[derive(Copy, Clone)]
pub struct Error;
fn produce_half_owl_error() -> Result<(), Error> {
    Ok(())
}

fn produce_half_owl_ok() -> Result<bool, ()> {
    Ok(true)
}

#[allow(dead_code)]
fn test_owl_result() -> Result<(), ()> {
    produce_half_owl_error().map_err(|_| ())?;
    produce_half_owl_ok().map(|_| ())?;
    // the following should not be linted,
    // we should not force users to use toilet closures
    // to produce owl results when drop is more convenient
    produce_half_owl_error().map_err(drop)?;
    produce_half_owl_ok().map_err(drop)?;
    Ok(())
}

#[allow(dead_code)]
fn test_owl_result_2() -> Result<u8, ()> {
    produce_half_owl_error().map_err(|_| ())?;
    produce_half_owl_ok().map(|_| ())?;
    // the following should not be linted,
    // we should not force users to use toilet closures
    // to produce owl results when drop is more convenient
    produce_half_owl_error().map_err(drop)?;
    produce_half_owl_ok().map(drop)?;
    Ok(1)
}