Auto merge of #4567 - phansch:toplevel_ref_arg, r=flip1995

Add run-rustfix for toplevel_ref_arg lint

changelog: none

cc #3630

tests/ui/toplevel_ref_arg.fixed

@@ -0,0 +1,25 @@
+// run-rustfix
+
+#![warn(clippy::toplevel_ref_arg)]
+#![allow(unused)]
+
+fn main() {
+    // Closures should not warn
+    let y = |ref x| println!("{:?}", x);
+    y(1u8);
+
+    let x = &1;
+
+    let y: &(&_, u8) = &(&1, 2);
+
+    let z = &(1 + 2);
+
+    let z = &mut (1 + 2);
+
+    let (ref x, _) = (1, 2); // ok, not top level
+    println!("The answer is {}.", x);
+
+    // Make sure that allowing the lint works
+    #[allow(clippy::toplevel_ref_arg)]
+    let ref mut x = 1_234_543;
+}

tests/ui/toplevel_ref_arg.rs

@@ -1,13 +1,9 @@
-#![warn(clippy::all)]
+// run-rustfix
+
+#![warn(clippy::toplevel_ref_arg)]
 #![allow(unused)]
 
-fn the_answer(ref mut x: u8) {
-    *x = 42;
-}
-
 fn main() {
-    let mut x = 0;
-    the_answer(x);
     // Closures should not warn
     let y = |ref x| println!("{:?}", x);
     y(1u8);

tests/ui/toplevel_ref_arg.stderr

@@ -1,34 +1,28 @@
-error: `ref` directly on a function argument is ignored. Consider using a reference type instead.
-  --> $DIR/toplevel_ref_arg.rs:4:15
+error: `ref` on an entire `let` pattern is discouraged, take a reference with `&` instead
+  --> $DIR/toplevel_ref_arg.rs:11:9
    |
-LL | fn the_answer(ref mut x: u8) {
-   |               ^^^^^^^^^
+LL |     let ref x = 1;
+   |     ----^^^^^----- help: try: `let x = &1;`
    |
    = note: `-D clippy::toplevel-ref-arg` implied by `-D warnings`
 
 error: `ref` on an entire `let` pattern is discouraged, take a reference with `&` instead
-  --> $DIR/toplevel_ref_arg.rs:15:9
-   |
-LL |     let ref x = 1;
-   |     ----^^^^^----- help: try: `let x = &1;`
-
-error: `ref` on an entire `let` pattern is discouraged, take a reference with `&` instead
-  --> $DIR/toplevel_ref_arg.rs:17:9
+  --> $DIR/toplevel_ref_arg.rs:13:9
    |
 LL |     let ref y: (&_, u8) = (&1, 2);
    |     ----^^^^^--------------------- help: try: `let y: &(&_, u8) = &(&1, 2);`
 
 error: `ref` on an entire `let` pattern is discouraged, take a reference with `&` instead
-  --> $DIR/toplevel_ref_arg.rs:19:9
+  --> $DIR/toplevel_ref_arg.rs:15:9
    |
 LL |     let ref z = 1 + 2;
    |     ----^^^^^--------- help: try: `let z = &(1 + 2);`
 
 error: `ref` on an entire `let` pattern is discouraged, take a reference with `&` instead
-  --> $DIR/toplevel_ref_arg.rs:21:9
+  --> $DIR/toplevel_ref_arg.rs:17:9
    |
 LL |     let ref mut z = 1 + 2;
    |     ----^^^^^^^^^--------- help: try: `let z = &mut (1 + 2);`
 
-error: aborting due to 5 previous errors
+error: aborting due to 4 previous errors
 

tests/ui/toplevel_ref_arg_non_rustfix.rs

@@ -0,0 +1,11 @@
+#![warn(clippy::toplevel_ref_arg)]
+#![allow(unused)]
+
+fn the_answer(ref mut x: u8) {
+    *x = 42;
+}
+
+fn main() {
+    let mut x = 0;
+    the_answer(x);
+}

tests/ui/toplevel_ref_arg_non_rustfix.stderr

@@ -0,0 +1,10 @@
+error: `ref` directly on a function argument is ignored. Consider using a reference type instead.
+  --> $DIR/toplevel_ref_arg_non_rustfix.rs:4:15
+   |
+LL | fn the_answer(ref mut x: u8) {
+   |               ^^^^^^^^^
+   |
+   = note: `-D clippy::toplevel-ref-arg` implied by `-D warnings`
+
+error: aborting due to previous error
+