Ignore actual members in UnusedPrivateMember

[sczerwinski]

The general rule of thumb should be:

• if a rule is ignored for abstract members, it should be ignored for expect members,
• if a rule is ignored for overridden members, it should be ignored for actual members.

See also:

• FunctionOnlyReturningConstant should ignore actual functions #3388
• Ignore actual functions in FunctionOnlyReturningConstant (#3388) #3390

Related to #3415

[codecov]

Codecov Report

Merging #3669 (adef6d3) into main (e9fd9f3) will increase coverage by 0.00%.
The diff coverage is 80.00%.

❗ Current head adef6d3 differs from pull request most recent head a6f6157. Consider uploading reports for the commit a6f6157 to get more accurate results

@@            Coverage Diff            @@
##               main    #3669   +/-   ##
=========================================
  Coverage     77.95%   77.96%           
  Complexity     2870     2870           
=========================================
  Files           470      470           
  Lines          9245     9248    +3     
  Branches       1761     1763    +2     
=========================================
+ Hits           7207     7210    +3     
  Misses         1077     1077           
  Partials        961      961           

Impacted Files	Coverage Δ	Complexity Δ
...turbosch/detekt/rules/style/UnusedPrivateMember.kt	91.17% <80.00%> (+0.19%)	5.00 <0.00> (ø)

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[chao2zhang]

How is this related to the rule of thumb if a rule is ignored for overridden members, it should be ignored for actual members.?

[sczerwinski]

This line is actually my mistake (I went with isExpect() one step too far). Actual classes or objects should be visited. Just their actual members should be ignored.

I'll update the PR.

[sczerwinski]

@chao2zhang, Sorry for the mistake. I've fixed the PR, rebased and squashed for better readability.

Also an example of an actual constructor, that should be ignored:
commonMain:

expect class Foo(bar: Bar) {
    expect fun doSomething()
}

jvmMain:

actual class Foo actual constructor(private val bar: Bar) {
    actual fun doSomething() {
        bar.doSomething()
    }
}

jsMain:

actual class Foo actual constructor(bar: Bar) {
    actual fun doSomething() {
        // Do something with JS that doesn't require bar
    }
}