Code shared from the Rust Playground

playground.rs

#![feature(trait_alias)]
#[derive(Debug, Clone)]
struct Context {
    a: A,
    b: B,
}

#[derive(Debug, Clone)]
struct A(i32);
#[derive(Debug, Clone)]
struct B(i32);

impl From<Context> for A {
    fn from(ctx: Context) -> Self {
        ctx.a
    }
}

impl From<Context> for B {
    fn from(ctx: Context) -> Self {
        ctx.b
    }
}

mod cw {
    pub(super) trait CallWith<Ctx, Args> {
    
        fn call_with(&self, ctx: Ctx);
    }
    
    impl<A: From<Ctx>, F: Fn(A), Ctx> CallWith<Ctx, (A,)> for F {
    
        fn call_with(&self, ctx: Ctx) {
            self(A::from(ctx));
        }
    }
    
    impl<A: From<Ctx>, B: From<Ctx>, F: Fn(A, B), Ctx: Clone> CallWith<Ctx, (A, B)> for F {
    
        fn call_with(&self, ctx: Ctx) {
            self(A::from(ctx.clone()), B::from(ctx));
        }
    }
}

trait CallWith<A> = cw::CallWith<Context, A>;



fn call<T>(ctx: Context, f:  impl CallWith<T>) {
    f.call_with(ctx)
}

fn main() {
    let ctx = Context {a: A(1), b: B(2) };
    call(ctx, |a: A, b: A| println!("{:?}", b));
}