Signedness Checker unable to know signedness of cast Object assigned to integral type

[DmitriyShepelev]

The Signedness Checker is unable to know the signedness of a cast (without an explicit annotation) Object assigned to the integral types byte, short, int, and long:

import org.checkerframework.checker.signedness.qual.Signed;

public class ObjectCasts {
    void castObjectToBoxedVariants() {
        byte b1 = 1;
        short s1 = 1;
        int i1 = 1;
        long l1 = 1;
        Object[] obj = new Object[] {b1, s1, i1, l1};
        byteParameter((Byte) obj[0]);
        shortParameter((Short) obj[1]);
        integralParameter((Integer) obj[2]);
        longParameter((Long) obj[3]);
    }

    void byteParameter(byte b) {}

    void shortParameter(short s) {}

    void integralParameter(int i) {}

    void longParameter(long l) {}
}

Command: javacheck -version -verbose -AprintAllQualifiers -processor SignednessChecker ObjectCasts.java

Output:
ObjectCastsOutput.txt

javacheck alias:
alias javacheck='$CHECKERFRAMEWORK/checker/bin/javac'

What can be changed in the Signedness Checker to eliminate this type of error?