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Diffstat (limited to 'src/tools/clippy/src/docs/rc_buffer.txt')
-rw-r--r-- | src/tools/clippy/src/docs/rc_buffer.txt | 27 |
1 files changed, 27 insertions, 0 deletions
diff --git a/src/tools/clippy/src/docs/rc_buffer.txt b/src/tools/clippy/src/docs/rc_buffer.txt new file mode 100644 index 000000000..82ac58eeb --- /dev/null +++ b/src/tools/clippy/src/docs/rc_buffer.txt @@ -0,0 +1,27 @@ +### What it does +Checks for `Rc<T>` and `Arc<T>` when `T` is a mutable buffer type such as `String` or `Vec`. + +### Why is this bad? +Expressions such as `Rc<String>` usually have no advantage over `Rc<str>`, since +it is larger and involves an extra level of indirection, and doesn't implement `Borrow<str>`. + +While mutating a buffer type would still be possible with `Rc::get_mut()`, it only +works if there are no additional references yet, which usually defeats the purpose of +enclosing it in a shared ownership type. Instead, additionally wrapping the inner +type with an interior mutable container (such as `RefCell` or `Mutex`) would normally +be used. + +### Known problems +This pattern can be desirable to avoid the overhead of a `RefCell` or `Mutex` for +cases where mutation only happens before there are any additional references. + +### Example +``` +fn foo(interned: Rc<String>) { ... } +``` + +Better: + +``` +fn foo(interned: Rc<str>) { ... } +```
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