119 lines
3.4 KiB
Rust
119 lines
3.4 KiB
Rust
//@ check-pass
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#![warn(dropping_references)]
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struct SomeStruct;
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fn main() {
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drop(&SomeStruct); //~ WARN calls to `std::mem::drop`
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let mut owned1 = SomeStruct;
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drop(&owned1); //~ WARN calls to `std::mem::drop`
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drop(&&owned1); //~ WARN calls to `std::mem::drop`
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drop(&mut owned1); //~ WARN calls to `std::mem::drop`
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drop(owned1);
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let reference1 = &SomeStruct;
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drop(reference1); //~ WARN calls to `std::mem::drop`
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let reference2 = &mut SomeStruct;
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drop(reference2); //~ WARN calls to `std::mem::drop`
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let ref reference3 = SomeStruct;
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drop(reference3); //~ WARN calls to `std::mem::drop`
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}
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#[allow(dead_code)]
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fn test_generic_fn_drop<T>(val: T) {
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drop(&val); //~ WARN calls to `std::mem::drop`
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drop(val);
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}
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#[allow(dead_code)]
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fn test_similarly_named_function() {
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fn drop<T>(_val: T) {}
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drop(&SomeStruct); //OK; call to unrelated function which happens to have the same name
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std::mem::drop(&SomeStruct); //~ WARN calls to `std::mem::drop`
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}
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#[derive(Copy, Clone)]
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pub struct Error;
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fn produce_half_owl_error() -> Result<(), Error> {
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Ok(())
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}
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fn produce_half_owl_ok() -> Result<bool, ()> {
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Ok(true)
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}
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#[allow(dead_code)]
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fn test_owl_result() -> Result<(), ()> {
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produce_half_owl_error().map_err(|_| ())?;
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produce_half_owl_ok().map(|_| ())?;
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// the following should not be linted,
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// we should not force users to use toilet closures
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// to produce owl results when drop is more convenient
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produce_half_owl_error().map_err(drop)?;
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produce_half_owl_ok().map_err(drop)?;
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Ok(())
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}
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#[allow(dead_code)]
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fn test_owl_result_2() -> Result<u8, ()> {
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produce_half_owl_error().map_err(|_| ())?;
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produce_half_owl_ok().map(|_| ())?;
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// the following should not be linted,
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// we should not force users to use toilet closures
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// to produce owl results when drop is more convenient
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produce_half_owl_error().map_err(drop)?;
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produce_half_owl_ok().map(drop)?;
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Ok(1)
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}
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#[allow(unused)]
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#[allow(clippy::unit_cmp)]
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fn issue10122(x: u8) {
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// This is a function which returns a reference and has a side-effect, which means
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// that calling drop() on the function is considered an idiomatic way of achieving
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// the side-effect in a match arm.
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fn println_and<T>(t: &T) -> &T {
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println!("foo");
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t
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}
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match x {
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// Don't lint (copy type), we only care about side-effects
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0 => drop(println_and(&12)),
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// Don't lint (no copy type), we only care about side-effects
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1 => drop(println_and(&String::new())),
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2 => {
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// Lint, even if we only care about the side-effect, it's already in a block
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drop(println_and(&13)); //~ WARN calls to `std::mem::drop`
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},
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// Lint, idiomatic use is only in body of `Arm`
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3 if drop(println_and(&14)) == () => (), //~ WARN calls to `std::mem::drop`
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// Lint, not a fn/method call
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4 => drop(&2), //~ WARN calls to `std::mem::drop`
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_ => (),
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}
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}
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fn issue112653() {
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fn foo() -> Result<&'static u8, ()> {
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println!("doing foo");
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Ok(&0) // result is not always useful, the side-effect matters
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}
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fn bar() {
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println!("doing bar");
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}
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fn stuff() -> Result<(), ()> {
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match 42 {
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0 => drop(foo()?), // drop is needed because we only care about side-effects
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1 => bar(),
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_ => (), // doing nothing (no side-effects needed here)
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}
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Ok(())
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}
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}
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