Add UseIsNullOrEmpty rule

[t-kameyama]

Fixes #3466

[codecov]

Codecov Report

Merging #3469 (7181506) into master (230bd48) will decrease coverage by 0.18%.
The diff coverage is 59.74%.

@@             Coverage Diff              @@
##             master    #3469      +/-   ##
============================================
- Coverage     80.28%   80.09%   -0.19%     
- Complexity     2784     2824      +40     
============================================
  Files           454      455       +1     
  Lines          8414     8490      +76     
  Branches       1608     1637      +29     
============================================
+ Hits           6755     6800      +45     
- Misses          789      793       +4     
- Partials        870      897      +27     

Impacted Files	Coverage Δ	Complexity Δ
.../arturbosch/detekt/rules/style/UseIsNullOrEmpty.kt	58.66% <58.66%> (ø)	40.00 <40.00> (?)
...rturbosch/detekt/rules/style/StyleGuideProvider.kt	100.00% <100.00%> (ø)	3.00 <0.00> (ø)

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[chao2zhang]

Given that we are having nested whens, I would recommend simplifying by extracting this when into two separate functions so that:

        val (expression, isEmptyString) = when {
            right.isEmptyString() -> sizeCheckedEmptyString(left as? KtSimpleNameExpression)
            left.isEmptyString() -> sizeCheckedEmptyString(right as? KtSimpleNameExpression)
            right.isZero() -> sizeCheckedEqualToZero(left as? KtDotQualifiedExpression)
            left.isZero() -> sizeCheckedEqualToZero(right as? KtDotQualifiedExpression)
            else -> null
        } ?: return null

[t-kameyama]

24be9d3