Trait alloc::slice::Concat [−][src]
Expand description
Helper trait for [T]::concat
.
Note: the Item
type parameter is not used in this trait,
but it allows impls to be more generic.
Without it, we get this error:
error[E0207]: the type parameter `T` is not constrained by the impl trait, self type, or predica --> src/liballoc/slice.rs:608:6 | 608 | impl<T: Clone, V: Borrow<[T]>> Concat for [V] { | ^ unconstrained type parameter
This is because there could exist V
types with multiple Borrow<[_]>
impls,
such that multiple T
types would apply:
pub struct Foo(Vec<u32>, Vec<String>); impl std::borrow::Borrow<[u32]> for Foo { fn borrow(&self) -> &[u32] { &self.0 } } impl std::borrow::Borrow<[String]> for Foo { fn borrow(&self) -> &[String] { &self.1 } }Run