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//@ run-pass
#![allow(dead_code)]
// This code produces a CFG with critical edges that, if we don't
// handle properly, will cause invalid codegen.
#![feature(rustc_attrs)]
enum State {
Both,
Front,
Back
}
pub struct Foo<A: Iterator, B: Iterator> {
state: State,
a: A,
b: B
}
impl<A, B> Foo<A, B>
where A: Iterator, B: Iterator<Item=A::Item>
{
// This is the function we care about
fn next(&mut self) -> Option<A::Item> {
match self.state {
State::Both => match self.a.next() {
elt @ Some(..) => elt,
None => {
self.state = State::Back;
self.b.next()
}
},
State::Front => self.a.next(),
State::Back => self.b.next(),
}
}
}
// Make sure we actually codegen a version of the function
pub fn do_stuff(mut f: Foo<Box<dyn Iterator<Item=u32>>, Box<dyn Iterator<Item=u32>>>) {
let _x = f.next();
}
fn main() {}
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