Just out of interest - back in the days when Kotli...

# compiler

[Rob Elliot]

Just out of interest - back in the days when Kotlin was first designed was there any discussion about making covariant generic types the default, with invariant & contravariant requiring extra syntax? My gut feel is that most people expect Foo<String> to be a subtype of Foo<Any>, and if you favour immutable data types then covariance often Just Works™.

I try and remember to use <out T> as my starting point, until I need something else, but I often forget...

[ephemient]

I don't know, but defaulting to <out T> only makes sense for immutable types

[Rob Elliot]

Yup, but I think there's a case, in the spirit of nudge, for biasing the language towards immutable types.