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Diffstat (limited to 'src/tools/clippy/src/docs/suspicious_to_owned.txt')
-rw-r--r-- | src/tools/clippy/src/docs/suspicious_to_owned.txt | 39 |
1 files changed, 39 insertions, 0 deletions
diff --git a/src/tools/clippy/src/docs/suspicious_to_owned.txt b/src/tools/clippy/src/docs/suspicious_to_owned.txt new file mode 100644 index 000000000..8cbf61dc7 --- /dev/null +++ b/src/tools/clippy/src/docs/suspicious_to_owned.txt @@ -0,0 +1,39 @@ +### What it does +Checks for the usage of `_.to_owned()`, on a `Cow<'_, _>`. + +### Why is this bad? +Calling `to_owned()` on a `Cow` creates a clone of the `Cow` +itself, without taking ownership of the `Cow` contents (i.e. +it's equivalent to calling `Cow::clone`). +The similarly named `into_owned` method, on the other hand, +clones the `Cow` contents, effectively turning any `Cow::Borrowed` +into a `Cow::Owned`. + +Given the potential ambiguity, consider replacing `to_owned` +with `clone` for better readability or, if getting a `Cow::Owned` +was the original intent, using `into_owned` instead. + +### Example +``` +let s = "Hello world!"; +let cow = Cow::Borrowed(s); + +let data = cow.to_owned(); +assert!(matches!(data, Cow::Borrowed(_))) +``` +Use instead: +``` +let s = "Hello world!"; +let cow = Cow::Borrowed(s); + +let data = cow.clone(); +assert!(matches!(data, Cow::Borrowed(_))) +``` +or +``` +let s = "Hello world!"; +let cow = Cow::Borrowed(s); + +let data = cow.into_owned(); +assert!(matches!(data, String)) +```
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