Fix unnecessary_cast suggestion when taking a reference

Author: Jarcho

clippy_lints/src/casts/unnecessary_cast.rs

@@ -90,7 +90,11 @@ pub(super) fn check<'tcx>(
             expr.span,
             &format!("casting to the same type is unnecessary (`{cast_from}` -> `{cast_to}`)"),
             "try",
-            cast_str,
+            if get_parent_expr(cx, expr).map_or(false, |e| matches!(e.kind, ExprKind::AddrOf(..))) {
+                format!("{{ {cast_str} }}")
+            } else {
+                cast_str
+            },
             Applicability::MachineApplicable,
         );
         return true;

tests/ui/unnecessary_cast.fixed

@@ -96,6 +96,9 @@ mod fixable {
 
         let _ = 1 as I32Alias;
         let _ = &1 as &I32Alias;
+
+        let x = 1i32;
+        let _ = &{ x };
     }
 
     type I32Alias = i32;

tests/ui/unnecessary_cast.rs

@@ -96,6 +96,9 @@ mod fixable {
 
         let _ = 1 as I32Alias;
         let _ = &1 as &I32Alias;
+
+        let x = 1i32;
+        let _ = &(x as i32);
     }
 
     type I32Alias = i32;

tests/ui/unnecessary_cast.stderr

@@ -150,35 +150,41 @@ error: casting float literal to `f32` is unnecessary
 LL |         let _ = -1.0 as f32;
    |                 ^^^^^^^^^^^ help: try: `-1.0_f32`
 
+error: casting to the same type is unnecessary (`i32` -> `i32`)
+  --> $DIR/unnecessary_cast.rs:101:18
+   |
+LL |         let _ = &(x as i32);
+   |                  ^^^^^^^^^^ help: try: `{ x }`
+
 error: casting integer literal to `i32` is unnecessary
-  --> $DIR/unnecessary_cast.rs:104:22
+  --> $DIR/unnecessary_cast.rs:107:22
    |
 LL |         let _: i32 = -(1) as i32;
    |                      ^^^^^^^^^^^ help: try: `-1_i32`
 
 error: casting integer literal to `i64` is unnecessary
-  --> $DIR/unnecessary_cast.rs:106:22
+  --> $DIR/unnecessary_cast.rs:109:22
    |
 LL |         let _: i64 = -(1) as i64;
    |                      ^^^^^^^^^^^ help: try: `-1_i64`
 
 error: casting float literal to `f64` is unnecessary
-  --> $DIR/unnecessary_cast.rs:113:22
+  --> $DIR/unnecessary_cast.rs:116:22
    |
 LL |         let _: f64 = (-8.0 as f64).exp();
    |                      ^^^^^^^^^^^^^ help: try: `(-8.0_f64)`
 
 error: casting float literal to `f64` is unnecessary
-  --> $DIR/unnecessary_cast.rs:115:23
+  --> $DIR/unnecessary_cast.rs:118:23
    |
 LL |         let _: f64 = -(8.0 as f64).exp(); // should suggest `-8.0_f64.exp()` here not to change code behavior
    |                       ^^^^^^^^^^^^ help: try: `8.0_f64`
 
 error: casting to the same type is unnecessary (`f32` -> `f32`)
-  --> $DIR/unnecessary_cast.rs:123:20
+  --> $DIR/unnecessary_cast.rs:126:20
    |
 LL |         let _num = foo() as f32;
    |                    ^^^^^^^^^^^^ help: try: `foo()`
 
-error: aborting due to 30 previous errors
+error: aborting due to 31 previous errors