Trait rustc_middle::ty::CollectAndApply

pub trait CollectAndApply<T, R>: Sized {
    type Output;

    // Required method
    fn collect_and_apply<I, F>(iter: I, f: F) -> Self::Output
       where I: Iterator<Item = Self>,
             F: FnOnce(&[T]) -> R;
}

Imagine you have a function F: FnOnce(&[T]) -> R, plus an iterator iter that produces T items. You could combine them with f(&iter.collect::<Vec<_>>()), but this requires allocating memory for the Vec.

This trait allows for faster implementations, intended for cases where the number of items produced by the iterator is small. There is a blanket impl for T items, but there is also a fallible impl for Result<T, E> items.

Required Associated Types

type Output

Required Methods

fn collect_and_apply<I, F>(iter: I, f: F) -> Self::Output

where I: Iterator<Item = Self>, F: FnOnce(&[T]) -> R,

Produce a result of type Self::Output from iter. The result will typically be produced by applying f on the elements produced by iter, though this may not happen in some impls, e.g. if an error occurred during iteration.

Object Safety

This trait is not object safe.

Implementations on Foreign Types

impl<T, R, E> CollectAndApply<T, R> for Result<T, E>

A fallible impl that will fail, without calling f, if there are any errors during collection.

fn collect_and_apply<I, F>(iter: I, f: F) -> Result<R, E>

where I: Iterator<Item = Result<T, E>>, F: FnOnce(&[T]) -> R,

Equivalent to Ok(f(&iter.collect::<Result<Vec<_>>>()?)).

type Output = Result<R, E>

Implementors

impl<T, R> CollectAndApply<T, R> for T

The blanket impl that always collects all elements and applies f.

type Output = R