docs: add note regarding LazyCell::borrow_mut

Add a notice in the documentation stating that `LazyCell::borrow_mut` allows the mutation of the inner contents.
indiv0 · Sep 10, 2018 · 9d634d1 · 9d634d1
1 parent b807802
commit 9d634d1
Showing 1 changed file with 4 additions and 0 deletions.
diff --git a/src/lib.rs b/src/lib.rs
@@ -53,6 +53,10 @@ use std::cell::UnsafeCell;
 use std::sync::atomic::{AtomicUsize, Ordering};
 
 /// A lazily filled `Cell`, with mutable contents.
+///
+/// A `LazyCell` is completely frozen once filled, **unless** you have `&mut`
+/// access to it, in which case `LazyCell::borrow_mut` may be used to mutate the
+/// contents.
 #[derive(Debug, Default)]
 pub struct LazyCell<T> {
     inner: UnsafeCell<Option<T>>,