RequireThis: False positive for lambda parameters

[MEZk]

$ cat TestClass.java
class InputAllowLocalVars {

    private String s1 = "foo1";

    void foo1() {
        final java.util.List<String> strings = new java.util.ArrayList<>();
            strings.add("foo1");
            strings.stream().filter(s1 -> s1.contains("f"))
            .collect(java.util.stream.Collectors.toList());
    }
}

$ cat TestConfig.xml
<?xml version="1.0"?>
<!DOCTYPE module PUBLIC
        "-//Puppy Crawl//DTD Check Configuration 1.3//EN"
        "http://www.puppycrawl.com/dtds/configuration_1_3.dtd">
<module name="Checker">
    <module name="TreeWalker">
        <module name="RequireThis">
            <property name="checkMethods" value="false" />
            <property name="validateOnlyOverlapping" value="false" />
        </module>
    </module>
</module>


$ java -jar checkstyle-7.6.1-all.jar -c TestConfig.xml TestClass.java
Starting audit...
[ERROR] TestClass.java:8:37: Reference to instance variable 's1' needs "this.". [RequireThis]
[ERROR] TestClass.java:8:43: Reference to instance variable 's1' needs "this.". [RequireThis]
Audit done.
Checkstyle ends with 2 errors.

http://rveach.no-ip.org/checkstyle/checkstyle.php?action=view&config=2b75d3a2ecffeba47690e0416ccd9906&code=c5b8991fb27367d9bfbf7d120993a7cb&checkstyle=checkstyle-7.6.1-all.jar&printTree=

---

Expected: no violations as this cannot be used for s1 on line 8 and column 37 (compile time error); s1 on line 8 and column 43 is a lambda parameter and it does not make sense to prefix it with this.

Note, that if validateOnlyOverlapping is set to true, the violations disappear.

[voidfist]

I am on it.

[voidfist]

class foo {   

     int x;
     int z;
     void methodInFirstLevel(int x) {
        
         //There would be no compiler errors for the statement A
         //because the parameter x is effectively final.
         
         Consumer<Integer> myConsumer = (y) -> 
         {
             System.out.println("x = " + x);         // Statement A
             System.out.println("y = " + y);
             System.out.println("this.x = " + this.x);
             System.out.println("LambdaScopeTest.this.x = " +
                 LambdaScopeTest.this.x);
             z++;                //Statement B
         };

         myConsumer.accept(x);

     }
}

Would it be desirable for RequireThis to report an error for statement A ? Currently there's no violation for x in statement A

@MEZk @romani please address. Thanks.

UPDATE: there's no violation for statement A because it's previous sibling isn't null and neither it's parent an assignment token. This policy has been maintained throughout RequireThis and holds for all the blocks and not just lambdas. Therefore I feel there shouldn't be any violation for statement A.

Also, in the current form, RequireThis points a violation for statement B. That is violation is acceptable, right ?

@rnveach Please address. Thanks

[MEZk]

@PS-SP

there's no violation for statement A because it's previous sibling isn't null and neither it's parent an assignment token.

Yes, this is not an assignment.

Also, in the current form, RequireThis points a violation for statement B. That is violation is acceptable, right ?

Yes, this is an assignment.

[rnveach]

Fix is merged