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#![warn(clippy::double_ended_iterator_last)]
// Typical case
pub fn last_arg(s: &str) -> Option<&str> {
s.split(' ').next_back() //~ ERROR: called `Iterator::last` on a `DoubleEndedIterator`
}
fn main() {
// General case
struct DeIterator;
impl Iterator for DeIterator {
type Item = ();
fn next(&mut self) -> Option<Self::Item> {
Some(())
}
}
impl DoubleEndedIterator for DeIterator {
fn next_back(&mut self) -> Option<Self::Item> {
Some(())
}
}
let _ = DeIterator.next_back(); //~ ERROR: called `Iterator::last` on a `DoubleEndedIterator`
// Should not apply to other methods of Iterator
let _ = DeIterator.count();
// Should not apply to simple iterators
struct SimpleIterator;
impl Iterator for SimpleIterator {
type Item = ();
fn next(&mut self) -> Option<Self::Item> {
Some(())
}
}
let _ = SimpleIterator.last();
// Should not apply to custom implementations of last()
struct CustomLast;
impl Iterator for CustomLast {
type Item = ();
fn next(&mut self) -> Option<Self::Item> {
Some(())
}
fn last(self) -> Option<Self::Item> {
Some(())
}
}
impl DoubleEndedIterator for CustomLast {
fn next_back(&mut self) -> Option<Self::Item> {
Some(())
}
}
let _ = CustomLast.last();
}
// Should not be linted because applying the lint would move the original iterator. This can only be
// linted if the iterator is used thereafter.
fn issue_14139() {
let mut index = [true, true, false, false, false, true].iter();
let subindex = index.by_ref().take(3);
let _ = subindex.last();
let _ = index.next();
let mut index = [true, true, false, false, false, true].iter();
let mut subindex = index.by_ref().take(3);
let _ = subindex.last();
let _ = index.next();
let mut index = [true, true, false, false, false, true].iter();
let mut subindex = index.by_ref().take(3);
let subindex = &mut subindex;
let _ = subindex.last();
let _ = index.next();
let mut index = [true, true, false, false, false, true].iter();
let mut subindex = index.by_ref().take(3);
let subindex = &mut subindex;
let _ = subindex.last();
let _ = index.next();
let mut index = [true, true, false, false, false, true].iter();
let (subindex, _) = (index.by_ref().take(3), 42);
let _ = subindex.last();
let _ = index.next();
let mut index = [true, true, false, false, false, true].iter();
let subindex = (index.by_ref().take(3), 42);
let _ = subindex.0.last();
let _ = index.next();
}
fn drop_order() {
struct DropDeIterator(std::vec::IntoIter<S>);
impl Iterator for DropDeIterator {
type Item = S;
fn next(&mut self) -> Option<Self::Item> {
self.0.next()
}
}
impl DoubleEndedIterator for DropDeIterator {
fn next_back(&mut self) -> Option<Self::Item> {
self.0.next_back()
}
}
struct S(&'static str);
impl std::ops::Drop for S {
fn drop(&mut self) {
println!("Dropping {}", self.0);
}
}
let v = vec![S("one"), S("two"), S("three")];
let mut v = DropDeIterator(v.into_iter());
println!("Last element is {}", v.next_back().unwrap().0);
//~^ ERROR: called `Iterator::last` on a `DoubleEndedIterator`
let v = vec![S("four"), S("five"), S("six")];
let mut v = (DropDeIterator(v.into_iter()), 42);
println!("Last element is {}", v.0.next_back().unwrap().0);
//~^ ERROR: called `Iterator::last` on a `DoubleEndedIterator`
println!("Done");
}
fn issue_14444() {
let mut squares = vec![];
let last_square = [1, 2, 3]
.into_iter()
.map(|x| {
squares.push(x * x);
Some(x * x)
})
.last();
}
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