hidden-trait

This library is a proc macro to expose a trait implementation.

The case we are trying to solve here: a library exposes some concrete structure for people to use. There can be multiple of them (e.g. Vector2, Vector3, Vector4 in a math library), or maybe it's one per platform (Vulkan vs Metal). Important part is - internally the library would like to have a trait implemented by this public type, but it doesn't want to expose the trait itself because of ergonomic reasons. Hence, "hidden-trait" to rescue.

```rust mod hidden { trait Foo { fn foo(&self) -> u32; }

pub struct Bar;

#[hidden_trait::expose]
impl Foo for Bar {
    fn foo(&self) -> u32 {
        42
    }
}

}

fn main() { let bar = hidden::Bar; // calling the trait method as if it's ours bar.foo(); } ```