In Arrow 2.0

NonEmptyList

has

@JvmInline

annotation, with this change

mock

libraries can not mock if

NonEmptyList

is used as a function parameter. Example:

interface Operation {
  suspend fun execute(items: NonEmptyList<String>): Either<Throwable, Unit>
class NonEmptyListTests : ShouldSpec({
  should("mocking") {
    val operation = mockk<Operation> {
      coEvery { execute(any()) } returns Unit.right()
    operation.execute(NonEmptyList("a", listOf("b", "c"))) shouldBe Unit.right()
Fails with the exception (less stack trace for brevity):
 Copy code
Caused by: java.lang.TypeNotPresentException: Type <unknown> not present
	at net.bytebuddy.description.type.TypeDefinition$Sort.describeOrNull(TypeDefinition.java:295)
	at net.bytebuddy.description.type.TypeDescription$Generic$OfWildcardType$ForLoadedType$WildcardUpperBoundTypeList.get(TypeDescription.java:4841)
	at net.bytebuddy.description.type.TypeDescription$Generic$OfWildcardType$ForLoadedType$WildcardUpperBoundTypeList.get(TypeDescription.java:4814)
	at net.bytebuddy.matcher.FilterableList$AbstractBase.getOnly(FilterableList.java:141)
The reason I believe Inline Classes are not open to generating proxies from them.
The workaround I did was change my codebase into 
List
  version of the implementation, but there might be people who might get affected.

We've switched to using Mokkery as it doesn't have as many issues around value classes. That said, we were bitten by this change to a value class as you cannot use a value class in a

lateinit var

I've updated to 2.0 and I have a similar issue to the one listed above in an Android project, except for me the issue is with Dagger2. Most likely, it's related to this issue. For me it seems that if any of my injectable classes have a method (public or private) that references an inline class that uses generics, it will fail to compile with an error similar to this:

Copy code

bad class file: ~/path/to/class.kt
    undeclared type variable: A
    Please remove or make sure it appears in the correct subdirectory of the classpath.

I was curious if it would be a reasonable request to have

NonEmptySet

and

NonEmptyList

changed to interfaces and have all factories that generate instances of these return an

inline

implementation? I know this isn't really an Arrow issue but I can't think of any good workarounds to this. I've ended up having to change most references to

NonEmptyCollection

for compilation to work, which is acceptable but I end up needing to cast or change the type of lists or sets more frequently and I feel that my API's aren't as clear.

Either

way, I'm open to `Option`s. 😅 See what I did there? 😂

I'm not entirely sure if there's any real benefit to making NonEmptySet and NonEmptyList inline value classes, given that most of the usages of it will likely be via the

List<T>

or

Set<T>

interfaces (or a supertype of), and thus will always be a boxed instance.

not really, people use

NonEmptyList

directly quite often, and in that case the inline implementation directly calls the function in the wrapper value, without having to perform additional boxing