Created
January 7, 2019 00:55
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A potential new API for ty::Binder
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| /// A number of lifetime and type parameters that a type is bound with | |
| #[derive(Copy, Clone, Debug)] | |
| pub struct Binder { | |
| num_lifetimes: u32, | |
| num_types: u32, | |
| } | |
| impl Binder { | |
| pub fn bind<T>(self, value: T) -> Bound<T> { | |
| Bound { | |
| binder: self, | |
| value, | |
| } | |
| } | |
| pub fn dummy() -> Self { | |
| Self { | |
| num_lifetimes: 0, | |
| num_types: 0, | |
| } | |
| } | |
| } | |
| /// A bound type, e.g. `for<'a, T> &'a T`. Contains a Binder with the number of | |
| /// lifetime and type parameters that it is bound with | |
| #[derive(Copy, Clone, Debug)] | |
| pub struct Bound<T> { | |
| binder: Binder, | |
| value: T, | |
| } | |
| impl<T> Bound<T> { | |
| pub fn unbind(self) -> (Binder, T) { | |
| (self.binder, self.value) | |
| } | |
| pub fn skip_binder(&self) -> &T { | |
| &self.value | |
| } | |
| pub fn map_bound<U> (self, f: impl FnOnce(T) -> U) -> Bound<U> { | |
| let (binder, value) = self.unbind(); | |
| f(value).bind_with(binder) | |
| } | |
| } | |
| pub trait Bind: Sized { | |
| fn bind_with(self, binder: Binder) -> Bound<Self> { | |
| Bound { | |
| binder, | |
| value: self, | |
| } | |
| } | |
| fn bind_with_dummy(self) -> Bound<Self> { | |
| self.bind_with(Binder::dummy()) | |
| } | |
| } | |
| impl<T> Bind for T {} | |
| fn main() { | |
| let bound = "1".bind_with_dummy(); | |
| let bound = bound.map_bound(|s| s.parse::<i32>().unwrap()); | |
| println!("{:#?}", bound); | |
| } |
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