Disambiguate str doc-links

Author: zachs18

library/alloc/src/string.rs

@@ -352,7 +352,7 @@ use crate::vec::{self, Vec};
 ///
 /// # Invariant
 ///
-/// Rust libraries may assume that `String`s are always valid UTF-8, [just like `str`s](str#invariant).
+/// Rust libraries may assume that `String`s are always valid UTF-8, [just like `str`s](prim@str#invariant).
 ///
 /// Constructing a non-UTF-8 `String` is not immediate undefined behavior, but any function
 /// called on a `String` may assume that it is valid UTF-8, which means that a non-UTF-8 `String`

library/core/src/str/converts.rs

@@ -149,7 +149,7 @@ pub const fn from_utf8_mut(v: &mut [u8]) -> Result<&mut str, Utf8Error> {
 /// This function is unsafe because it does not check that the bytes passed
 /// to it are valid UTF-8. If this constraint is violated, it may cause
 /// memory unsafety issues with future users of the `str`, as the rest of
-/// the standard library [assumes that `str`s are valid UTF-8](str#invariant).
+/// the standard library [assumes that `str`s are valid UTF-8](prim@str#invariant).
 ///
 /// # Examples
 ///

library/core/src/str/mod.rs

@@ -313,7 +313,7 @@ impl str {
     /// bytes which are not valid UTF-8. If this constraint is violated, using
     /// the original `str` after the `&mut [u8]` borrow expires may violate memory
     /// safety, as the rest of the standard library [assumes that `str`s are
-    /// valid UTF-8](str#invariant).
+    /// valid UTF-8](prim@str#invariant).
     ///
     /// # Examples
     ///