[Bug]: VariableAccessFilter does not find all accesses of a generic variable

[Luro02]

Describe the bug

The VariableAccessFilter should match all accesses to a variable:

This simple filter matches all the accesses to a given field.

(from the docs)

This is not the case for the below code. The implementation looks like this:

boolean matches(CtVariableAccess<?> ctVariableAccess) {
     return ctVariableAccess.getVariable().equals(this.variableReference);
}

In the below code, this.variableReference is a reference to T field and ctVariableAccess would be a reference to String field. That is why even though they access the same field, they do not match.

A potential fix for this would be to check if they are refering to the same field:

record BetterVariableAccessFilter<T extends CtVariableAccess<?>>(CtVariable<?> ctVariable) implements Filter<T> {
    @Override
    public boolean matches(T element) {
        return element.getVariable().equals(this.ctVariable.getReference())
            || (element.getVariable().getDeclaration() != null && element.getVariable().getDeclaration().equals(this.ctVariable));
    }
}

Source code you are trying to analyze/transform

public class Example<T> {
    T field;

    public static void main(String[] args) {
        Example<String> example = new Example<>();

        example.field = "Hello"; // write access to Example#field
        System.out.println(example.field); // read access to Example#field
    }
}

Source code for your Spoon processing

import org.junit.jupiter.api.Test;
import spoon.Launcher;
import spoon.reflect.code.CtVariableAccess;
import spoon.reflect.declaration.CtClass;
import spoon.reflect.visitor.filter.VariableAccessFilter;

import java.util.List;

import static org.junit.jupiter.api.Assertions.assertEquals;

class TestVariableAccessFilter {
    @Test
    void testGenericFieldAccess() {
        CtClass<?> ctClass = Launcher.parseClass("""
            public class Example<T> {
                T field;

                public static void main(String[] args) {
                    Example<String> example = new Example<>();
                    
                    example.field = "Hello"; // write access to Example#field
                    System.out.println(example.field); // read access to Example#field
                }
            }
            """);

        List<CtVariableAccess<?>> accesses = ctClass.getElements(
            new VariableAccessFilter<>(ctClass.getField("field").getReference())
        );

        assertEquals(2, accesses.size());
    }
}

Actual output

org.opentest4j.AssertionFailedError: 
Expected :2
Actual   :0
<Click to see difference>

Expected output

No response

Spoon Version

10.4.0

JVM Version

openjdk version "17.0.1" 2021-10-19 OpenJDK Runtime Environment Temurin-17.0.1+12 (build 17.0.1+12) OpenJDK 64-Bit Server VM Temurin-17.0.1+12 (build 17.0.1+12, mixed mode, sharing)

What operating system are you using?

Windows 10

[MartinWitt]

Looks reasonable, can you make a PR?