Consider this code:
---
public class PatternLocal {
    public static boolean test(Object o) {
        return o instanceof String s && s.length() > 0;
    }
}
---

javac desugars the pattern test into:
---
public class PatternLocal {
    
    public PatternLocal() {
        super();
    }
    
    public static boolean test(Object o) {
        return (let String s in (let /*synthetic*/ Object s$temp = o in s$temp instanceof String && (let s = (String)s$temp; in true)) && s.length() > 0);
    }
}
---

The temporary variable s$temp is unnecessary here, as o is already a local variable and its value cannot change inside the pattern matching expression.