Rollup merge of #56941 - euclio:deny-libstd-resolution-failures, r=QuietMisdreavus

deny intra-doc link resolution failures in libstd

Fixes #56693.

Until we land a fix for the underlying issue (#56922), we can at least fix the failures in libstd so they don't propagate to downstream crates.

src/liballoc/rc.rs

@@ -843,6 +843,8 @@ unsafe impl<#[may_dangle] T: ?Sized> Drop for Rc<T> {
     /// drop(foo);    // Doesn't print anything
     /// drop(foo2);   // Prints "dropped!"
     /// ```
+    ///
+    /// [`Weak`]: ../../std/rc/struct.Weak.html
     fn drop(&mut self) {
         unsafe {
             self.dec_strong();
@@ -1422,9 +1424,10 @@ impl<T: ?Sized + fmt::Debug> fmt::Debug for Weak<T> {
 #[stable(feature = "downgraded_weak", since = "1.10.0")]
 impl<T> Default for Weak<T> {
     /// Constructs a new `Weak<T>`, allocating memory for `T` without initializing
-    /// it. Calling [`upgrade`][Weak::upgrade] on the return value always gives [`None`].
+    /// it. Calling [`upgrade`] on the return value always gives [`None`].
     ///
     /// [`None`]: ../../std/option/enum.Option.html
+    /// [`upgrade`]: ../../std/rc/struct.Weak.html#method.upgrade
     ///
     /// # Examples
     ///