Can someone give a simple code example of builder ...

# getting-started

[smit01]

Can someone give a simple code example of builder inference in new kotlin 1.7.0 version. I tried to go through docs but didn't quite understand please.😅

[ephemient]

interface BuilderScope<T> {
    fun emit(value: T)
}
fun <T> build(builder: BuilderScope<T>.() -> Unit)

build { emit(0) }

in Kotlin 1.2: does not typecheck, you need to write build<Int> { emit(0) } explicitly
in Kotlin 1.3: does not typecheck, but it will if the function is declared fun <T> build(@BuilderInference builder: BuilderScope<T>.() -> Unit)
In Kotlin 1.7: will typecheck as written above

[ephemient]

the standard builders (buildList, buildSet, buildMap, sequence, etc.) all have a return type involving T, so another way to get it to typecheck is to put it in some context where the return type doesn't need to be inferred, e.g.

val foo: List<Int> = buildList { add(0) }

but without builder inference, Kotlin cannot infer the type if Int does not appear anywhere