mirror of https://github.com/rust-lang/rust
51 lines
1.2 KiB
Rust
51 lines
1.2 KiB
Rust
//@ revisions: base extended
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#![cfg_attr(extended, feature(generic_associated_types_extended))]
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#![cfg_attr(extended, allow(incomplete_features))]
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trait RefCont<'a, T> {
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fn t(&'a self) -> &'a T;
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}
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impl<'a, T> RefCont<'a, T> for &'a T {
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fn t(&'a self) -> &'a T {
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self
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}
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}
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impl<'a, T> RefCont<'a, T> for Box<T> {
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fn t(&'a self) -> &'a T {
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self.as_ref()
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}
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}
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trait MapLike<K, V> {
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type VRefCont<'a>: RefCont<'a, V> where Self: 'a;
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fn get<'a>(&'a self, key: &K) -> Option<Self::VRefCont<'a>>;
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}
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impl<K: Ord, V: 'static> MapLike<K, V> for std::collections::BTreeMap<K, V> {
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type VRefCont<'a> = &'a V where Self: 'a;
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fn get<'a>(&'a self, key: &K) -> Option<&'a V> {
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std::collections::BTreeMap::get(self, key)
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}
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}
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struct Source;
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impl<K, V: Default> MapLike<K, V> for Source {
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type VRefCont<'a> = Box<V>;
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fn get<'a>(&self, _: &K) -> Option<Box<V>> {
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Some(Box::new(V::default()))
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}
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}
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fn main() {
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let m = Box::new(std::collections::BTreeMap::<u8, u8>::new())
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//[base]~^ ERROR the trait
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//[extended]~^^ type mismatch
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as Box<dyn MapLike<u8, u8, VRefCont = dyn RefCont<'_, u8>>>;
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//~^ ERROR missing generics for associated type
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//[base]~^^ ERROR the trait
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}
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