Could not find method kotlin() for arguments [gradle-plugin, 1.3.20]

Question

I've copied exactly what the kotlin gradle docs say to implement kotlin gradle plugin, however it's returning the following error:

Could not find method kotlin() for arguments [gradle-plugin, 1.3.20] on object of type org.gradle.api.internal.artifacts.dsl.dependencies.DefaultDependencyHandler.

my gradle

buildscript {
    ext.kotlin_version = '1.3.0'
    repositories {
        google()
        jcenter()
    }

    dependencies {
        classpath 'com.android.tools.build:gradle:3.3.0'
        classpath(kotlin("gradle-plugin", version = "1.3.20"))

        // NOTE: Do not place your application dependencies here; they belong
        // in the individual module build.gradle files
    }
//    ext {
//        navigationVersion = '28.0.0'
//    }
    plugins {
        kotlin("<...>")
    }
}


allprojects {
    repositories {
        google()
        jcenter()
    }
}

task clean(type: Delete) {
    delete rootProject.buildDir
}

Any idea?

Answer 1

build.gradle can be written in Groovy or Kotlin. You're typing your build.gradle in Groovy (not Kotlin), but you have copied the Kotlin code. You should select the Groovy tab on the documentation:

buildscript {
    repositories {
        google()
        jcenter()
    }
    dependencies {
        classpath "com.android.tools.build:gradle:3.3.0"
        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:1.3.20"
    }

}

Here: https://kotlinlang.org/docs/reference/using-gradle.html#targeting-android

You can also find a decent example by creating an empty Android and Kotlin project.