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use discard;
use discard::Discard;
use std::ops::{Deref, DerefMut};
#[must_use = "
The DiscardOnDrop is unused, which causes it to be immediately discarded.
You probably don't want that to happen.
How to fix this:
* Store the DiscardOnDrop in a variable or data structure.
* Or use the leak() method which will cause it to not be
discarded (this will usually leak memory!)
See the documentation for more details.
"]
#[derive(Debug)]
pub struct DiscardOnDrop< A: Discard >( discard::DiscardOnDrop< A > );
impl< A: Discard > DiscardOnDrop< A > {
#[inline]
pub fn new( discarder: A ) -> Self {
DiscardOnDrop( discard::DiscardOnDrop::new( discarder ) )
}
#[inline]
pub fn leak( self ) -> A {
discard::DiscardOnDrop::leak( self.0 )
}
}
impl< A: Discard > Deref for DiscardOnDrop< A > {
type Target = A;
#[inline]
fn deref( &self ) -> &Self::Target {
&*self.0
}
}
impl< A: Discard > DerefMut for DiscardOnDrop< A > {
#[inline]
fn deref_mut( &mut self ) -> &mut Self::Target {
&mut *self.0
}
}
#[cfg(test)]
mod tests {
use discard::Discard;
use super::DiscardOnDrop;
use std::rc::Rc;
use std::cell::Cell;
struct Foo( Rc< Cell< bool > > );
impl Foo {
fn new() -> Self {
Foo( Rc::new( Cell::new( false ) ) )
}
fn dropped( &self ) -> Rc< Cell< bool > > {
self.0.clone()
}
fn as_mut( &mut self ) -> &mut Self {
self
}
}
impl Discard for Foo {
fn discard( self ) {
self.0.set( true );
}
}
#[test]
fn unused() {
Foo::new();
}
#[test]
#[allow(unused_must_use)]
fn unused_discard_on_drop() {
DiscardOnDrop::new( Foo::new() );
}
#[test]
fn discard() {
let foo = Foo::new();
let dropped = foo.dropped();
assert_eq!( dropped.get(), false );
foo.discard();
assert_eq!( dropped.get(), true );
}
#[test]
fn no_discard() {
let foo = Foo::new();
let dropped = foo.dropped();
assert_eq!( dropped.get(), false );
drop( foo );
assert_eq!( dropped.get(), false );
}
#[test]
fn discard_on_drop() {
let foo = DiscardOnDrop::new( Foo::new() );
let dropped = foo.dropped();
assert_eq!( dropped.get(), false );
drop( foo );
assert_eq!( dropped.get(), true );
}
#[test]
fn leak() {
let foo = DiscardOnDrop::new(Foo::new());
let dropped = foo.dropped();
assert_eq!( dropped.get(), false );
drop( foo.leak() );
assert_eq!( dropped.get(), false );
}
#[test]
fn deref_mut() {
let mut foo = DiscardOnDrop::new( Foo::new() );
let dropped = foo.as_mut().dropped();
assert_eq!( dropped.get(), false );
drop( foo.leak() );
assert_eq!( dropped.get(), false );
}
}