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kotlinlang

How does kotlin gradle dsl generate... I guess the ability to use extensions like tasks.jar?

What do you mean exactly? It uses configuration time information about available tasks/extensions/configurations and generate Kotlin code with type-safe accessors

Well like, if I use apply&lt;SomePlugin&gt;() that doesn't work in a typeasfe way... UNLESS I do it in a subprojects block in a superproject.

I don't really understand why that would be

Apply doesn't generate accessors, only applying plugin in plugins block

Check official doc, it explains this:
 <https://docs.gradle.org/current/userguide/kotlin_dsl.html#type-safe-accessors|https://docs.gradle.org/current/userguide/kotlin_dsl.html#type-safe-accessors>