Trait type_equalities::IsEqual[−][src]

pub trait IsEqual<U: ?Sized>: AliasSelf<Alias = U> { }
Expand description

Equality at a constraint level, as a type alias. Reflexivity holds.

Example

Note that due to the rust type checker, coercions are not as simple as they might look.

ⓘ
// Trying to implement coerce like this fails!
fn foo<U, T: IsEqual<U>>(t: T) -> U { t }
assert_eq!(foo::<u32, u32>(42), 42)
//   |
// 6 | fn foo<U, T: IsEqual<U>>(t: T) -> U { t }
//   |        -  -                       -   ^ expected type parameter `U`, found type parameter `T`
//   |        |  |                       |
//   |        |  found type parameter    expected `U` because of return type
//   |        expected type parameter

But the following works correctly:

fn foo<U, T: IsEqual<U>>(t: T) -> U { trivial_eq().coerce(t) }
assert_eq!(foo::<u32, u32>(42), 42)

Implementors