Fix ImmutableString docs.
@@ -16,8 +16,8 @@ use std::{
/// The system immutable string type.
///
-/// An [`ImmutableString`] wraps an [`Rc`][std::rc::Rc]`<`[`String`]`>`
-/// (or [`Arc`][std::sync::Arc]`<`[`String`]`>` under the `sync` feature)
+/// An [`ImmutableString`] wraps an [`Rc`][std::rc::Rc]`<`[`SmartString`][smartstring::SmartString]`>`
+/// (or [`Arc`][std::sync::Arc]`<`[`SmartString`][smartstring::SmartString]`>` under the `sync` feature)
/// so that it can be simply shared and not cloned.
///
/// # Example
