Trait BorrowRange

pub trait BorrowRange<T: ?Sized, R>: Borrow<R> { }

Helper trait to allow passing a range as either a owned value or a reference.

For instance:

use std::ops::RangeBounds;
use range_cmp::BorrowRange;
fn f<T, R: RangeBounds<T>, B: BorrowRange<T, R>>(range: B) {
    let range = range.borrow();
    // ...
}

With concrete type such as i32, this would be achieved by taking a generic type T with the bound T: Borrow<i32>. So we might be tempted to do the same with the RangeBounds trait:

use std::borrow::Borrow;
use std::ops::RangeBounds;
fn f<R: RangeBounds<i32>, B: Borrow<R>>(range: B) {
    let range = range.borrow();
    // ...
}
f(0..42)

However, this fails to compile when passing a reference:

f(&(0..42))

The compilation output is:

  | f(&(0..42))
  | ^ cannot infer type of the type parameter `R` declared on the function `f`

Indeed, although we understand we want to pass a Range<i32> by reference, the compiler need to assume that other types could yield a &Range<i32> when borrowed.

Implementations on Foreign Types

impl<T, R: RangeBounds<T>> BorrowRange<T, R> for &R

Implementors

impl<T, R: RangeBounds<T>> BorrowRange<T, R> for R