Cleanup for ref_mut_iter_method_chain

Author: Jarcho

clippy_lints/src/methods/mod.rs

@@ -1867,19 +1867,17 @@ declare_clippy_lint! {
     /// Check for `&mut iter` followed by a method call.
     ///
     /// ### Why is this bad?
-    /// This requires using parenthesis to signify precedence.
+    /// Using `(&mut iter)._` requires using parenthesis to signify precedence.
     ///
     /// ### Example
     /// ```rust
     /// let mut iter = ['a', 'b', '.', 'd'].iter();
     /// let before_dot = (&mut iter).take_while(|&&c| c != '.').collect::<Vec<_>>();
-    /// let after_dot = iter.collect::<Vec<_>>();
     /// ```
     /// Use instead:
     /// ```rust
     /// let mut iter = ['a', 'b', '.', 'd'].iter();
     /// let before_dot = iter.by_ref().take_while(|&&c| c != '.').collect::<Vec<_>>();
-    /// let after_dot = iter.collect::<Vec<_>>();
     /// ```
     pub REF_MUT_ITER_METHOD_CHAIN,
     style,

tests/ui/ref_mut_iter_method_chain.fixed

@@ -26,7 +26,11 @@ fn main() {
 
     // Don't lint. No method chain.
     for &x in &mut iter {
-        print!("{}", x)
+        print!("{}", x);
+    }
+
+    for &x in iter.by_ref().filter(|&&x| x % 2 == 0) {
+        print!("{}", x);
     }
 
     let iter = &mut iter;

tests/ui/ref_mut_iter_method_chain.rs

@@ -26,7 +26,11 @@ fn main() {
 
     // Don't lint. No method chain.
     for &x in &mut iter {
-        print!("{}", x)
+        print!("{}", x);
+    }
+
+    for &x in (&mut iter).filter(|&&x| x % 2 == 0) {
+        print!("{}", x);
     }
 
     let iter = &mut iter;

tests/ui/ref_mut_iter_method_chain.stderr

@@ -13,16 +13,22 @@ LL |     let _ = (&mut m!(iter)).find(|&&x| x == 1);
    |             ^^^^^^^^^^^^^^^ help: try: `m!(iter).by_ref()`
 
 error: use of `&mut` on an iterator in a method chain
-  --> $DIR/ref_mut_iter_method_chain.rs:33:5
+  --> $DIR/ref_mut_iter_method_chain.rs:32:15
+   |
+LL |     for &x in (&mut iter).filter(|&&x| x % 2 == 0) {
+   |               ^^^^^^^^^^^ help: try: `iter.by_ref()`
+
+error: use of `&mut` on an iterator in a method chain
+  --> $DIR/ref_mut_iter_method_chain.rs:37:5
    |
 LL |     (&mut *iter).find(|&&x| x == 1);
    |     ^^^^^^^^^^^^ help: try: `iter.by_ref()`
 
 error: use of `&mut` on an iterator in a method chain
-  --> $DIR/ref_mut_iter_method_chain.rs:36:5
+  --> $DIR/ref_mut_iter_method_chain.rs:40:5
    |
 LL |     (&mut **iter).find(|&&x| x == 1);
    |     ^^^^^^^^^^^^^ help: try: `(*iter).by_ref()`
 
-error: aborting due to 4 previous errors
+error: aborting due to 5 previous errors