Inline Method drops the qualifier of a method reference, changing program output #9774

Apache NetBeans version

Apache NetBeans 31

What happened

Inline Method on a bound method reference replaces the reference with a lambda and drops the qualifier expression entirely. In this case the qualifier is a method call with a side effect, so the refactored program produces a different result.

Language / Project Type / NetBeans Component

Java SE application

How to reproduce

InlineMethod_S005_T07.java

1. Create a Java SE project and add a file named InlineMethod_S005_T07.java with the
   code below (InlineMethod_S005_T07 is the test-case ID from my refactoring
   comparison suite; the class is self-contained).
2. Put the caret on getValue in the method reference getArrayHolder()::getValue.
3. Refactor-> Inline ,and accept the defaults.
4. Run the class.

Before reflactoring:

import java.util.function.IntSupplier;
public class InlineMethod_S005_T07 {
    private static int[] values = new int[]{1, 2, 3};
    static class ArrayHolder {
        int getValue() {
            return values[0];
        }
    }
    static ArrayHolder getArrayHolder() {
        values[0] = 99;
        return new ArrayHolder();
    }
    static int run() {
        IntSupplier supplier = getArrayHolder()::getValue;
        return supplier.getAsInt();
    }
    public static void main(String[] args) {
        System.out.println(run());
    }
}
//output: 99

After reflactoring:

import java.util.function.IntSupplier;
public class InlineMethod_S005_T07 {
    private static int[] values = new int[]{1, 2, 3};
    static class ArrayHolder {
    }
    static ArrayHolder getArrayHolder() {
        values[0] = 99;
        return new ArrayHolder();
    }
    static int run() {
        IntSupplier supplier = () -> {
            return values[0];
        };
        return supplier.getAsInt();
    }
    public static void main(String[] args) {
        System.out.println(run());
    }
}
//output: 1

Did this work correctly in an earlier version?

Apache NetBeans 31

Operating System

Windows 11

JDK

JDK 24

Apache NetBeans packaging

Apache NetBeans binary zip

Anything else

Possible directions:

1. Evaluate the qualifier once into a temporary and inline the body against it, e.g.
   ArrayHolder tmp = getArrayHolder();
   IntSupplier supplier = () -> { return tmp.getValue(); };
2. Or refuse/warn when the qualifier is not a simple effectively-final variable.
3. Keep the current path only for unbound references (Type::method).
   The same code path is used for every bound method reference, so this is not specific to the test case. I can provide the full project or a screen recording if useful.

Are you willing to submit a pull request?

No