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// Issue 52126: With respect to variance, the assign-op's like += were
// accidentally lumped together with other binary op's. In both cases
// we were coercing the LHS of the op to the expected supertype.
//
// The problem is that since the LHS of += is modified, we need the
// parameter to be invariant with respect to the overall type, not
// covariant.
use std::collections::HashMap;
use std::ops::AddAssign;
pub fn main() {
panics();
}
pub struct Counter<'l> {
map: HashMap<&'l str, usize>,
}
impl<'l> AddAssign for Counter<'l>
{
fn add_assign(&mut self, rhs: Counter<'l>) {
rhs.map.into_iter().for_each(|(key, val)| {
let count = self.map.entry(key).or_insert(0);
*count += val;
});
}
}
/// Often crashes, if not prints invalid strings.
pub fn panics() {
let mut acc = Counter{map: HashMap::new()};
for line in vec!["123456789".to_string(), "12345678".to_string()] {
let v: Vec<&str> = line.split_whitespace().collect();
//~^ ERROR `line` does not live long enough
// println!("accumulator before add_assign {:?}", acc.map);
let mut map = HashMap::new();
for str_ref in v {
let e = map.entry(str_ref);
println!("entry: {:?}", e);
let count = e.or_insert(0);
*count += 1;
}
let cnt2 = Counter{map};
acc += cnt2;
// println!("accumulator after add_assign {:?}", acc.map);
// line gets dropped here but references are kept in acc.map
}
}
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