Fix typo “a Rc” → “an Rc”

compiler/rustc_data_structures/src/owning_ref/mod.rs

@@ -1146,7 +1146,7 @@ unsafe fn to_handle_mut(x: *const Self) -> Self::HandleMut {
 /// Typedef of an owning reference that uses a `String` as the owner.
 pub type StringRef = OwningRef<String, str>;
 
-/// Typedef of an owning reference that uses a `Rc` as the owner.
+/// Typedef of an owning reference that uses an `Rc` as the owner.
 pub type RcRef<T, U = T> = OwningRef<Rc<T>, U>;
 /// Typedef of an owning reference that uses an `Arc` as the owner.
 pub type ArcRef<T, U = T> = OwningRef<Arc<T>, U>;

library/alloc/src/rc.rs

@@ -1743,7 +1743,7 @@ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 #[cfg(not(no_global_oom_handling))]
 #[stable(feature = "from_for_ptrs", since = "1.6.0")]
 impl<T> From<T> for Rc<T> {
-    /// Converts a generic type `T` into a `Rc<T>`
+    /// Converts a generic type `T` into an `Rc<T>`
     ///
     /// The conversion allocates on the heap and moves `t`
     /// from the stack into it.

library/std/src/ffi/c_str.rs

@@ -958,7 +958,7 @@ fn from(s: &CStr) -> Arc<CStr> {
 
 #[stable(feature = "shared_from_slice2", since = "1.24.0")]
 impl From<CString> for Rc<CStr> {
-    /// Converts a [`CString`] into a [`Rc`]`<CStr>` without copying or allocating.
+    /// Converts a [`CString`] into an [`Rc`]`<CStr>` without copying or allocating.
     #[inline]
     fn from(s: CString) -> Rc<CStr> {
         let rc: Rc<[u8]> = Rc::from(s.into_inner());

library/std/src/ffi/os_str.rs

@@ -916,7 +916,7 @@ fn from(s: &OsStr) -> Arc<OsStr> {
 
 #[stable(feature = "shared_from_slice2", since = "1.24.0")]
 impl From<OsString> for Rc<OsStr> {
-    /// Converts an [`OsString`] into a [`Rc`]`<OsStr>` without copying or allocating.
+    /// Converts an [`OsString`] into an [`Rc`]`<OsStr>` without copying or allocating.
     #[inline]
     fn from(s: OsString) -> Rc<OsStr> {
         let rc = s.inner.into_rc();