False positive on UnnecessaryInnerClass calls to this

[dzirbel]

Expected Behavior

If an inner class has a plan reference to this, UnnecessaryInnerClass should still raise an issue.

Observed Behavior

UnnecessaryInnerClass does not raise an issue, even though the class could be made non-inner.

Steps to Reproduce

@Test
fun `reports even with calls to this`() {
    val code = """
        class A {
            inner class B {
                fun foo() {
                    this
                }
            }
        }
    """.trimIndent()

    assertThat(subject.lintWithContext(env, code)).hasSize(1)
}

Context

I came across this issue while working on labeled expressions in #4865 but was unable to find a resolution. It seems that visitReferenceExpression() will be invoked for any plain call to this and resolve it in the example above as class A when it should be B. Even though it's a reference to this, the expression is not a KtThisExpression but a plain KtNameReferenceExpression with a referenced name of this; aside from checking against that referenced name I couldn't find a way to distinguish it from other expressions.

I don't have a particular use case, but it does seem to interfere with labeled expressions in some cases, e.g.

@Test
fun `reports irrelevant labeled expressions`() {
    val code = """
        class A {
            inner class B {
                fun inner() {
                    return Unit.apply { this@B }
                }
            }
        }
    """.trimIndent()

    assertThat(subject.lintWithContext(env, code)).hasSize(1)
}

this test will fail, not because of labeled expression as per #4865 but because of the use of this@B, even though that doesn't require B to be inner.

Your Environment

• current main branch (fcd9c48159685fc049da6e6d2b3a77db3aea00bd)