Update docs for manual_split_once

Author: Jarcho

clippy_lints/src/methods/mod.rs

@@ -1774,24 +1774,28 @@ declare_clippy_lint! {
 }
 
 declare_clippy_lint! {
-    /// **What it does:** Checks for usages of `splitn(2, _)`
+    /// **What it does:** Checks for usages of `str::splitn(2, _)`
     ///
-    /// **Why is this bad?** `split_once` is clearer.
+    /// **Why is this bad?** `split_once` is both clearer in intent and slightly more efficient.
     ///
     /// **Known problems:** None.
     ///
     /// **Example:**
     ///
     /// ```rust
     /// // Bad
-    /// let some_str = "name=value";
-    /// let mut iter = some_str.splitn(2, '=');
-    /// let name = iter.next().unwrap();
-    /// let value = iter.next().unwrap_or("");
+    /// fn f(s: &str) -> Option<&str> {
+    ///     let (key, value) = s.splitn(2, '=').next_tuple()?;
+    ///     let value = s.splitn(2, '=').nth(1)?;
+    ///     None
+    /// }
     ///
     /// // Good
-    /// let some_str = "name=value";
-    /// let (name, value) = some_str.split_once('=').unwrap_or((some_str, ""));
+    /// fn f2(s: &str) -> Option<&str> {
+    ///     let (key, value) = s.splitn(2, '=').next_tuple()?;
+    ///     let value = s.splitn(2, '=').nth(1)?;
+    ///     None
+    /// }
     /// ```
     pub MANUAL_SPLIT_ONCE,
     complexity,