| trait RefCont<'a, T> { |
| fn t(&'a self) -> &'a T; |
| } |
| |
| impl<'a, T> RefCont<'a, T> for &'a T { |
| fn t(&'a self) -> &'a T { |
| self |
| } |
| } |
| |
| impl<'a, T> RefCont<'a, T> for Box<T> { |
| fn t(&'a self) -> &'a T { |
| self.as_ref() |
| } |
| } |
| |
| trait MapLike<K, V> { |
| type VRefCont<'a>: RefCont<'a, V> |
| where |
| Self: 'a; |
| fn get<'a>(&'a self, key: &K) -> Option<Self::VRefCont<'a>>; |
| } |
| |
| impl<K: Ord, V: 'static> MapLike<K, V> for std::collections::BTreeMap<K, V> { |
| type VRefCont<'a> |
| = &'a V |
| where |
| Self: 'a; |
| fn get<'a>(&'a self, key: &K) -> Option<&'a V> { |
| std::collections::BTreeMap::get(self, key) |
| } |
| } |
| |
| struct Source; |
| |
| impl<K, V: Default> MapLike<K, V> for Source { |
| type VRefCont<'a> = Box<V>; |
| fn get<'a>(&self, _: &K) -> Option<Box<V>> { |
| Some(Box::new(V::default())) |
| } |
| } |
| |
| fn main() { |
| let m = Box::new(std::collections::BTreeMap::<u8, u8>::new()) |
| as Box<dyn MapLike<u8, u8, VRefCont = dyn RefCont<'_, u8>>>; |
| //~^ ERROR the trait |
| //~| ERROR missing generics for associated type |
| } |