Commit
This commit does not belong to any branch on this repository, and may belong to a fork outside of the repository.
impl {Add, AddAssign}<{str, Cow<str>}> for Cow<str>
This does not actually add anything that wasn't there, but is merely an optimization for the given cases, which would have incurred additional heap allocation for adding empty strings, and improving the ergonomics of `Cow` with strings.
- Loading branch information
Showing
2 changed files
with
112 additions
and
1 deletion.
There are no files selected for viewing
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Original file line number | Diff line number | Diff line change |
---|---|---|
@@ -0,0 +1,65 @@ | ||
// Copyright 2012-2013-2014 The Rust Project Developers. See the COPYRIGHT | ||
// file at the top-level directory of this distribution and at | ||
// http://rust-lang.org/COPYRIGHT. | ||
// | ||
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or | ||
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license | ||
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your | ||
// option. This file may not be copied, modified, or distributed | ||
// except according to those terms. | ||
|
||
use std::borrow::Cow; | ||
|
||
// check that Cow<'a, str> implements addition | ||
#[test] | ||
fn check_cow_add() { | ||
borrowed1 = Cow::Borrowed("Hello, "); | ||
borrowed2 = Cow::Borrowed("World!"); | ||
borrow_empty = Cow::Borrowed(""); | ||
|
||
owned1 = Cow::Owned("Hi, ".into()); | ||
owned2 = Cow::Owned("Rustaceans!".into()); | ||
owned_empty = Cow::Owned("".into()); | ||
|
||
assert_eq!("Hello, World!", borrowed1 + borrowed2); | ||
assert_eq!("Hello, Rustaceans!", borrowed1 + owned2); | ||
|
||
assert_eq!("Hello, World!", owned1 + borrowed2); | ||
assert_eq!("Hello, Rustaceans!", owned1 + owned2); | ||
|
||
if let Cow::Owned(_) = borrowed1 + borrow_empty { | ||
panic!("Adding empty strings to a borrow should note allocate"); | ||
} | ||
if let Cow::Owned(_) = borrow_empty + borrowed1 { | ||
panic!("Adding empty strings to a borrow should note allocate"); | ||
} | ||
if let Cow::Owned(_) = borrowed1 + owned_empty { | ||
panic!("Adding empty strings to a borrow should note allocate"); | ||
} | ||
if let Cow::Owned(_) = owned_empty + borrowed1 { | ||
panic!("Adding empty strings to a borrow should note allocate"); | ||
} | ||
} | ||
|
||
fn check_cow_add_assign() { | ||
borrowed1 = Cow::Borrowed("Hello, "); | ||
borrowed2 = Cow::Borrowed("World!"); | ||
borrow_empty = Cow::Borrowed(""); | ||
|
||
owned1 = Cow::Owned("Hi, ".into()); | ||
owned2 = Cow::Owned("Rustaceans!".into()); | ||
owned_empty = Cow::Owned("".into()); | ||
|
||
let borrowed1clone = borrowed1.clone(); | ||
borrowed1clone += borrow_empty; | ||
assert_eq!((&borrowed1clone).as_ptr(), (&borrowed1).as_ptr()); | ||
|
||
borrowed1clone += owned_empty; | ||
assert_eq!((&borrowed1clone).as_ptr(), (&borrowed1).as_ptr()); | ||
|
||
owned1 += borrowed2; | ||
borrowed1 += owned2; | ||
|
||
assert_eq!("Hello, World!", owned1); | ||
assert_eq!("Hello, Rustaceans!", borrowed1); | ||
} |