CharSequence extensions might return String or StringBuilder

1

Hi, is it expected behaviour that some of CharSequence extensions returns String while some StringBuilder?

for ex:

val s = "abc"
val s1 = s.substring(0, s.length).reversed()
val s2 = s.subSequence(0, s.length).reversed()
val s3 = s.subSequence(0, s.length).filter { true }
val s4 = s.subSequence(0, s.length)
val s5 = s.filter { true }
val s6 = s.subSequence(0, s.length).drop(1)

then log javaClass.simpleName:

s1 is String
s2 is StringBuilder
s3 is StringBuilder
s4 is String
s5 is String
s6 is String
2

Yes, operations on CharSequence are declared so that they produce another CharSequece. Both StringBuilder and String implement CharSequence, thus it’s ok to return either of them as the result.

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