Add necessary parentheses to manual_unwrap_or_default lint output

tests/ui/manual_unwrap_or_default.fixed

@@ -17,3 +17,12 @@ fn main() {
     let x: Option<Vec<String>> = None;
     x.unwrap_or_default();
 }
+
+// Issue #12531
+unsafe fn no_deref_ptr(a: Option<i32>, b: *const Option<i32>) -> i32 {
+    match a {
+        // `*b` being correct depends on `a == Some(_)`
+        Some(_) => (*b).unwrap_or_default(),
+        _ => 0,
+    }
+}

tests/ui/manual_unwrap_or_default.rs

@@ -38,3 +38,15 @@ fn main() {
         Vec::default()
     };
 }
+
+// Issue #12531
+unsafe fn no_deref_ptr(a: Option<i32>, b: *const Option<i32>) -> i32 {
+    match a {
+        // `*b` being correct depends on `a == Some(_)`
+        Some(_) => match *b {
+            Some(v) => v,
+            _ => 0,
+        },
+        _ => 0,
+    }
+}

tests/ui/manual_unwrap_or_default.stderr

@@ -52,5 +52,15 @@ LL | |         Vec::default()
 LL | |     };
    | |_____^ help: replace it with: `x.unwrap_or_default()`
 
-error: aborting due to 5 previous errors
+error: match can be simplified with `.unwrap_or_default()`
+  --> tests/ui/manual_unwrap_or_default.rs:46:20
+   |
+LL |           Some(_) => match *b {
+   |  ____________________^
+LL | |             Some(v) => v,
+LL | |             _ => 0,
+LL | |         },
+   | |_________^ help: replace it with: `(*b).unwrap_or_default()`
+
+error: aborting due to 6 previous errors