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trait Monad {
type Unwrapped;
type Wrapped<B>;
fn bind<B, F>(self, f: F) -> Self::Wrapped<B> {
//~^ ERROR: the size for values of type `Self` cannot be known
todo!()
}
}
fn join<MOuter, MInner, A>(outer: MOuter) -> MOuter::Wrapped<A>
where
MOuter: Monad<Unwrapped = MInner>,
MInner: Monad<Unwrapped = A, Wrapped = MOuter::Wrapped<A>>,
//~^ ERROR: missing generics for associated type `Monad::Wrapped`
{
outer.bind(|inner| inner)
}
fn main() {
assert_eq!(join(Some(Some(true))), Some(true));
//~^ ERROR: `Option<Option<bool>>: Monad` is not satisfied
}
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