Why does directly calling groovy closure not work, but using .call() does?

问题

This question relates to another question: passing a closure in a plugin extension in gradle

The solution was to call the closure with .call().

Why does this work instead of directly calling the closure?

来源：https://stackoverflow.com/questions/56467564/why-does-directly-calling-groovy-closure-not-work-but-using-call-does