update all_errors solution

src/exercises/all_errors.md

@@ -4,30 +4,39 @@ Make this compile and pass tests:
 
 ```rust
 # trait Collects {
-# type Error;
+# type Fast;
+# type Slow;
 # type Output;
-# fn push(&self, trace: Vec<i32>, next: i32) -> Result<Vec<i32>, Self::Error>;
-# fn regularize(&self, result: Result<Result<Vec<i32>, Vec<i32>>, Self::Error>) -> Result<Vec<i32>, Self::Output>;
+# fn create(&self, next: i32) -> Result<Self::Slow, Self::Fast>;
+# fn update(&self, slow: &mut Self::Slow, next: i32);
+# fn regularize(&self, result: Result<Result<Vec<i32>, Self::Slow>, Self::Fast>) -> Result<Vec<i32>, Self::Output>;
 # }
 # struct First;
 # struct All;
 # impl Collects for First {
-# type Error = i32;
+# type Fast = i32;
+# type Slow = std::convert::Infallible;
 # type Output = i32;
-# fn push(&self, _trace: Vec<i32>, next: i32) -> Result<Vec<i32>, Self::Error> { Err(next) }
-# fn regularize(&self, result: Result<Result<Vec<i32>, Vec<i32>>, Self::Error>) -> Result<Vec<i32>, Self::Output> { result.map(|r| r.unwrap()) }
+# fn create(&self, next: i32) -> Result<Self::Slow, Self::Fast> { Err(next) }
+# fn update(&self, slow: &mut Self::Slow, _next: i32) { match *slow {} }
+# fn regularize(&self, result: Result<Result<Vec<i32>, Self::Slow>, Self::Fast>) -> Result<Vec<i32>, Self::Output> { result.map(|r| r.unwrap_or_else(|slow| match slow {} )) }
 # }
 # impl Collects for All {
-# type Error = std::convert::Infallible;
+# type Fast = std::convert::Infallible;
+# type Slow = Vec<i32>;
 # type Output = Vec<i32>;
-# fn push(&self, mut trace: Vec<i32>, next: i32) -> Result<Vec<i32>, Self::Error> { trace.push(next); Ok(trace) }
-# fn regularize(&self, result: Result<Result<Vec<i32>, Vec<i32>>, Self::Error>) -> Result<Vec<i32>, Self::Output> { result.unwrap() }
+# fn create(&self, next: i32) -> Result<Self::Slow, Self::Fast> { let mut slow = vec![]; slow.push(next); Ok(slow) }
+# fn update(&self, slow: &mut Self::Slow, next: i32) { slow.push(next) }
+# fn regularize(&self, result: Result<Result<Vec<i32>, Self::Slow>, Self::Fast>) -> Result<Vec<i32>, Self::Output> { result.unwrap_or_else(|fast| match fast {}) }
 # }
 # fn first() -> impl Collects<Output = i32> { First }
 # fn all() -> impl Collects<Output = Vec<i32>> { All }
-# fn _only_postivie<C: Collects>(numbers: Vec<i32>, c: &C) -> Result<Result<Vec<i32>, Vec<i32>>, C::Error> {
+# fn _only_postivie<C: Collects>(numbers: Vec<i32>, c: &C) -> Result<Result<Vec<i32>, C::Slow>, C::Fast> {
 # let mut state = Ok(vec![]);
-# for x in numbers { state = if x > 0 { state.map(|mut vec| {vec.push(x); vec}) } else { Err(c.push(match state { Ok(_) => vec![], Err(vec) => vec }, x)?) } }
+# for x in numbers { state = if x > 0 { state.map(|mut vec| {vec.push(x); vec}) } else { Err(match state {
+# Ok(_) => c.create(x)?,
+# Err(mut slow) => { c.update(&mut slow, x) ; slow }
+# }) } }
 # Ok(state)
 # }
 # fn only_positive<C: Collects>(numbers: Vec<i32>, c: C) -> Result<Vec<i32>, C::Output> { c.regularize(_only_postivie(numbers, &c)) }