the method exists but the following trait bounds were not satisfied repeats the bounds multiple times

[nagisa]

use std::collections::HashMap;
fn intersect_map<K, V>(this: &mut HashMap<K, V>, other: HashMap<K, V>) -> bool {
    this.drain()
}

reports

note: the method `drain` exists but the following trait bounds were not satisfied: `K : std::cmp::Eq`, `K : std::hash::Hash`, `K : std::cmp::Eq`, `K : std::hash::Hash`

Note how it reports about K missing necessary bounds twice.