Could not get unknown property 'extra' for object of type DefaultScriptHandler

Question

I try to convert gradle file into kotlin script file: build.gradle

buildscript {
    ext {
        compose_version = '1.2.0'
    }
}
plugins {
    id("com.android.application") version "7.4.0" apply false
    id("com.android.library") version "7.4.0" apply false
    id("org.jetbrains.kotlin.android") version "1.7.0" apply false
}

I refer to this answer: build.gradle.kts

buildscript {
    extra.apply{
        set("compose_version", "1.2.0")
    }
}

but not working:

A problem occurred evaluating root project 'Sage'.
> Could not get unknown property 'extra' for object of type org.gradle.api.internal.initialization.DefaultScriptHandler.