PatternMatchingInstanceof misses casts with a parenthesized operand `(T)(x)`

[Chordrain]

Error Prone version

Error Prone 2.49.0 (javac plugin) — javac 21.0.8, source/target 21.

Check name

PatternMatchingInstanceof

Description

PatternMatchingInstanceof flags if (x instanceof T) { ... (T) x ... } blocks that could be rewritten with a pattern binding if (x instanceof T t). The matcher inspects the cast expression (T) x to decide applicability. Wrapping the cast operand in parentheses — (T) x → (T)(x) — is syntactically inert (JLS §15.16: parentheses around an operand do not change value or type), but the rule no longer recognizes the cast and drops the suggestion.

Reproducer

// BEFORE — 1 finding on the cast
public class Sample {
  public int f(Object o) {
    if (o instanceof String) {  // PatternMatchingInstanceof reported here
      String s = (String) o;
      return s.length();
    }
    return o.hashCode();
  }
}

// AFTER — parenthesized cast operand, 0 findings
public class Sample {
  public int f(Object o) {
    if (o instanceof String) {
      String s = (String)(o);    // semantically identical, no warning
      return s.length();
    }
    return o.hashCode();
  }
}

Expected behavior

PatternMatchingInstanceof should produce the same finding on BEFORE and AFTER. (String) o and (String)(o) are the same cast with the same operand, type, and runtime value.

Actual behavior

• BEFORE: 1 finding.
• AFTER: 0 findings.

The matcher only inspects the bare-operand cast form and does not look through enclosing parentheses on the cast operand.