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Existential types already exist as `impl Trait` for method parameters, unfortunately return position impl traits aren't fully existential because you can only r
by BlackFly 2y ago
Existential types already exist as `impl Trait` for method parameters, unfortunately return position impl traits aren't fully existential because you can only return one type from a function.
- Ericson2314 2y agoExistential quantification is type of variable bindings. You can't point to a think that doesn't bind a variable and say it's the same thing.
- BlackFly 2y agoI have absolutely no idea what you're trying to say. The RPIT will be bound by the caller and there exists a type such that the declared trait is implemented. Meanwhile an impl parameter will be bound within the method with some type existing such that the trait is implemented. That is the implication of existential, "there exists a type such that...".