Don't lint on auto-deref field access

Author: Jarcho

clippy_lints/src/only_used_in_recursion.rs

@@ -339,10 +339,15 @@ impl<'tcx> LateLintPass<'tcx> for OnlyUsedInRecursion {
                             e = parent;
                             continue;
                         },
-                        ExprKind::Field(..) | ExprKind::AddrOf(..) | ExprKind::Cast(..) => {
+                        ExprKind::AddrOf(..) | ExprKind::Cast(..) => {
                             e = parent;
                             continue;
                         },
+                        // Only allow field accesses without auto-deref
+                        ExprKind::Field(..) if typeck.adjustments().get(child_id).is_none() => {
+                            e = parent;
+                            continue
+                        }
                         _ => (),
                     },
                     _ => (),

tests/ui/only_used_in_recursion.rs

@@ -177,7 +177,25 @@ fn overwritten_param(flag: u32, mut a: usize) -> usize {
     } else {
         a = 5;
     }
-    overwritten_param(flag, a)
+    overwritten_param(flag - 1, a)
+}
+
+fn field_direct(flag: u32, mut a: (usize,)) -> usize {
+    if flag == 0 {
+        0
+    } else {
+        a.0 += 5;
+        field_direct(flag - 1, a)
+    }
+}
+
+fn field_deref(flag: u32, a: &mut Box<(usize,)>) -> usize {
+    if flag == 0 {
+        0
+    } else {
+        a.0 += 5;
+        field_deref(flag - 1, a)
+    }
 }
 
 fn main() {}

tests/ui/only_used_in_recursion.stderr

@@ -234,10 +234,22 @@ LL | fn overwritten_param(flag: u32, mut a: usize) -> usize {
    |                                     ^ help: if this is intentional, prefix it with an underscore: `_a`
    |
 note: parameter used here
-  --> $DIR/only_used_in_recursion.rs:180:29
+  --> $DIR/only_used_in_recursion.rs:180:33
    |
-LL |     overwritten_param(flag, a)
-   |                             ^
+LL |     overwritten_param(flag - 1, a)
+   |                                 ^
 
-error: aborting due to 20 previous errors
+error: parameter is only used in recursion
+  --> $DIR/only_used_in_recursion.rs:183:32
+   |
+LL | fn field_direct(flag: u32, mut a: (usize,)) -> usize {
+   |                                ^ help: if this is intentional, prefix it with an underscore: `_a`
+   |
+note: parameter used here
+  --> $DIR/only_used_in_recursion.rs:188:32
+   |
+LL |         field_direct(flag - 1, a)
+   |                                ^
+
+error: aborting due to 21 previous errors