noinline

In Kotlin, the noinline keyword is used as an annotation on a function parameter of a higher-order function to specify that the corresponding lambda expression passed to that parameter should not be allowed to be inlined by the compiler.

When a function is marked with the inline modifier, the compiler may choose to inline the function's code at the call site, eliminating the overhead of a function call. However, when you pass a lambda expression as a parameter to an inline function, the compiler may also attempt to inline the lambda code at the call site. In some cases, you may want to prevent the inlining of a particular lambda expression, and that's where noinline comes in.

Here's an example to illustrate its usage:

inline fun executeWithLogging(action: () -> Unit, noinline loggingAction: () -> Unit) {
    println("Executing action")
    action()
    println("Action executed")
    
    println("Logging action")
    loggingAction()
    println("Action logged")
}

fun main() {
    executeWithLogging(
        {
            // This code will be inlined
            println("Performing some action")
        },
        {
            // This code will NOT be inlined, thanks to 'noinline'
            println("Logging the action")
        }
    )
}

In this example, the executeWithLogging function is marked as inline, allowing the compiler to inline the lambda passed to the action parameter. The lambda passed to the loggingAction parameter, on the other hand, is marked with noinline, indicating that it should not be inlined even though the containing function is marked as inline.