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// check-pass
#![warn(dropping_references)]
struct SomeStruct;
fn main() {
drop(&SomeStruct); //~ WARN calls to `std::mem::drop`
let mut owned1 = SomeStruct;
drop(&owned1); //~ WARN calls to `std::mem::drop`
drop(&&owned1); //~ WARN calls to `std::mem::drop`
drop(&mut owned1); //~ WARN calls to `std::mem::drop`
drop(owned1);
let reference1 = &SomeStruct;
drop(reference1); //~ WARN calls to `std::mem::drop`
let reference2 = &mut SomeStruct;
drop(reference2); //~ WARN calls to `std::mem::drop`
let ref reference3 = SomeStruct;
drop(reference3); //~ WARN calls to `std::mem::drop`
}
#[allow(dead_code)]
fn test_generic_fn_drop<T>(val: T) {
drop(&val); //~ WARN calls to `std::mem::drop`
drop(val);
}
#[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); //~ WARN calls to `std::mem::drop`
}
#[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)
}
#[allow(unused)]
#[allow(clippy::unit_cmp)]
fn issue10122(x: u8) {
// This is a function which returns a reference and has a side-effect, which means
// that calling drop() on the function is considered an idiomatic way of achieving
// the side-effect in a match arm.
fn println_and<T>(t: &T) -> &T {
println!("foo");
t
}
match x {
// Don't lint (copy type), we only care about side-effects
0 => drop(println_and(&12)),
// Don't lint (no copy type), we only care about side-effects
1 => drop(println_and(&String::new())),
2 => {
// Lint, even if we only care about the side-effect, it's already in a block
drop(println_and(&13)); //~ WARN calls to `std::mem::drop`
},
// Lint, idiomatic use is only in body of `Arm`
3 if drop(println_and(&14)) == () => (), //~ WARN calls to `std::mem::drop`
// Lint, not a fn/method call
4 => drop(&2), //~ WARN calls to `std::mem::drop`
_ => (),
}
}
fn issue112653() {
fn foo() -> Result<&'static u8, ()> {
println!("doing foo");
Ok(&0) // result is not always useful, the side-effect matters
}
fn bar() {
println!("doing bar");
}
fn stuff() -> Result<(), ()> {
match 42 {
0 => drop(foo()?), // drop is needed because we only care about side-effects
1 => bar(),
_ => (), // doing nothing (no side-effects needed here)
}
Ok(())
}
}
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