deref_addrof_double_trigger: Note why rustfix can't be used

Author: Manishearth

tests/ui/deref_addrof_double_trigger.rs

@@ -1,5 +1,7 @@
+// This test can't work with run-rustfix because it needs two passes of test+fix
+
 #[warn(clippy::deref_addrof)]
-#[allow(unused_variables)]
+#[allow(unused_variables, unused_mut)]
 fn main() {
     let a = 10;
 

tests/ui/deref_addrof_double_trigger.stderr

@@ -1,19 +1,19 @@
 error: immediately dereferencing a reference
-  --> $DIR/deref_addrof_double_trigger.rs:8:14
+  --> $DIR/deref_addrof_double_trigger.rs:10:14
    |
 LL |     let b = **&&a;
    |              ^^^^ help: try this: `&a`
    |
    = note: `-D clippy::deref-addrof` implied by `-D warnings`
 
 error: immediately dereferencing a reference
-  --> $DIR/deref_addrof_double_trigger.rs:12:17
+  --> $DIR/deref_addrof_double_trigger.rs:14:17
    |
 LL |         let y = *&mut x;
    |                 ^^^^^^^ help: try this: `x`
 
 error: immediately dereferencing a reference
-  --> $DIR/deref_addrof_double_trigger.rs:19:18
+  --> $DIR/deref_addrof_double_trigger.rs:21:18
    |
 LL |         let y = **&mut &mut x;
    |                  ^^^^^^^^^^^^ help: try this: `&mut x`