libs: make Cow usable, improve documentation #19157
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This commit makes `Cow` more usable by allowing it to be applied to unsized types (as was intended) and providing some basic `ToOwned` implementations on slice types. It also corrects the documentation for `Cow` to no longer mention `DerefMut`, and adds an example.
| //! methods directly on the data it encloses. The first time a mutable reference | ||
| //! is required, the data will be cloned (via `to_owned`) if it is not | ||
| //! already owned. | ||
| //! `Cow` implements both `Deref`, which means that you can call |
|
This is actually really cool, I didn't know we had this 🐄 |
| @@ -609,6 +609,11 @@ impl BorrowFrom<String> for str { | |||
| fn borrow_from(owned: &String) -> &str { owned[] } | |||
| } | |||
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| #[unstable = "trait is unstable"] | |||
| impl ToOwned<String> for str { | |||
| fn to_owned(&self) -> String { self.to_string() } | |||
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This should use into_string. to_string goes through the formatting infrastructure, and tends to over-allocate space in the heap. See this playpen example, and also see #16415.
alexcrichton
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Nov 22, 2014
This commit makes `Cow` more usable by allowing it to be applied to unsized types (as was intended) and providing some basic `ToOwned` implementations on slice types. It also corrects the documentation for `Cow` to no longer mention `DerefMut`, and adds an example.
bors
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Nov 23, 2014
This commit makes `Cow` more usable by allowing it to be applied to unsized types (as was intended) and providing some basic `ToOwned` implementations on slice types. It also corrects the documentation for `Cow` to no longer mention `DerefMut`, and adds an example. Closes #19123
lnicola
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Feb 24, 2025
doc: move dev docs to manual
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This commit makes
Cowmore usable by allowing it to be applied tounsized types (as was intended) and providing some basic
ToOwnedimplementations on slice types. It also corrects the documentation for
Cowto no longer mentionDerefMut, and adds an example.Closes #19123