This compiles in Kotlin 1.5.21 but fails to typecheck in Kotlin 1.5.30-RC: ```fun f(l: MutableList&l...

# announcements

[ephemient]

This compiles in Kotlin 1.5.21 but fails to typecheck in Kotlin 1.5.30-RC:

fun f(l: MutableList<String>) {}
@ExperimentalStdlibApi
val l: List<Any> = buildList {
    javaClass
    f(this)
}

Did something change with builder inference?

[Rajkumar Singh]

this could be one of many reasons
https://blog.jetbrains.com/kotlin/2021/08/kotlin-1-5-30-rc-released/#opt-in-requirements

[ephemient]

no, it happens with other @BuilderInference, this is just the simplest reproduction example

[dmitriy.novozhilov]

cc @Victor Petukhov

[Victor Petukhov]

We have a lot of changes in the builder inference and soon there will be the corresponding announcement. Your example will work in 1.5.30 (including RC) under the compiler flag -Xunrestricted-builder-inference.