```In Book.kt: data class Book(val isbn: ISBN, va...

# getting-started

[Tim Schraepen]

In Book.kt:

data class Book(val isbn: ISBN, val title: Title)
@JvmInline value class ISBN(val value: String)
@JvmInline value class Title(val value: String)

Somewhere in BookDAO.java:
new Book("123","Thundercats");

When I'm looking at the code in IntelliJ, it's simply compiling (no red squiggly lines).
When I run a mvn clean install it also just compiles.
But when I do a build (ctrl+F9), I'm getting this:
java: Book(java.lang.String,java.lang.String) has private access in Book

When I define book as
data class Book(val isbn: String, val title: String)
compilation does succeed.

What is going on? It smells like intelliJ is using an older Kotlin version to compile or something?
In the build output I'm getting this:

...
Kotlin: kotlinc-jvm 1.7.20 (JRE 17.0.2+8)
...
javac 11.0.9 was used to compile java sources

I'd like to try to get kotlinc-jvm to use JRE 11 to compile, but don't know how.

[ephemient]

https://github.com/Kotlin/KEEP/blob/master/proposals/inline-classes.md#:~:text=Constructors%20with%20inline%[…]ameters%20are%20marked%20as%20private

[Tim Schraepen]

Thanks for the very fast response @ephemient!
So, works as intended I guess 😅
Why is it that there's not squiggly line in IntelliJ's edit window?

[ephemient]

I don't know, that seems like a bug

[Tim Schraepen]

Follow up questions:

in Book.kt
data class Book(private val _isbn: String, private val _title: String){
    val isbn: ISBN
        @JvmName("getIsbn") get() = ISBN(_isbn)
    val title: Title = Title(_title)
}
@JvmInline value class ISBN(val value: String)
@JvmInline value class Title(val value: String)

Somewhere in BookDAO.java:
book.getIsbn()
book.getTitle()

Same issue, IntelliJ the editor is not showing any issues, and even provides auto-completion hints for both .getIsbn() and .getTitle().

Build Output:

java: cannot find symbol
  symbol:   method getTitle()
  location: variable book of type Book

[Tim Schraepen]

The culprit was actually
<kotlin.compiler.incremental>true</kotlin.compiler.incremental>
in my pom.xml.
Setting it to false actually produces a publically visible constructor with the value classes inlined, like you'd expect, and also generates the correct getters, during compilation (build output).