IgnoredReturnValue: fix false negative when annotation is on the class

[t-kameyama]

Fixes #3975

[codecov]

Codecov Report

Merging #3979 (12fbbed) into main (70c2c25) will increase coverage by 0.00%.
The diff coverage is 88.88%.

@@            Coverage Diff            @@
##               main    #3979   +/-   ##
=========================================
  Coverage     83.49%   83.50%           
- Complexity     3160     3163    +3     
=========================================
  Files           458      458           
  Lines          9047     9052    +5     
  Branches       1759     1760    +1     
=========================================
+ Hits           7554     7559    +5     
- Misses          567      568    +1     
+ Partials        926      925    -1     

Impacted Files	Coverage Δ
...arturbosch/detekt/rules/bugs/IgnoredReturnValue.kt	83.33% <88.88%> (+3.33%)	⬆️
...osch/detekt/rules/empty/EmptyDefaultConstructor.kt	80.00% <0.00%> (ø)

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[t-kameyama]

We need to take @CanIgnoreReturnValue into account.
https://github.com/assertj/assertj-core/blob/main/src/main/java/org/assertj/core/api/Assertions.java#L1483

[BraisGabin]

Nice and thanks for the PR! But now we have another problem: https://github.com/detekt/detekt/pull/3979/checks?check_run_id=3159666709#step:5:1836

And as it seems it was a false positive that AssertJ had and they fixed using @CanIgnoreReturnValue: https://github.com/assertj/assertj-core/pull/1534/files

It seems like error prone supports that annotation so maybe we should do it too.

Edit: Ups! Didn't saw your comment!

[BraisGabin]

Thank you so much for this contribution! I can't imagine how much bugs can fix this PR in our users code base.

[picklebento]

Would you mind adding a test case when the annotation @CheckReturnValue is on the parent class but the method on a child class is invoked without checking the return value?

I do not have strong opinion whether we should report a violation or not, but documenting it in the test would help us clarify.