Can anyone explain why the compiler can't smart cast

b

in

b.isEmpty()

but it does for

a

in

a.isEmpty()

?

val a: String? = null
val b: String? = null
when {
  a == null && b == null -> true
  a == null -> b.isEmpty()
  b == null -> a.isEmpty()
}

So I'm working on a project with dagger and kotlin, and including the kapt execution is giving me a whole bunch of xlint errors, it seems to process the annotations correctly, it's just crowding the compile logs quite a bit. here is the compiler config

<plugin>
                <groupId>org.jetbrains.kotlin</groupId>
                <artifactId>kotlin-maven-plugin</artifactId>
                <version>${kotlin.version}</version>
                <executions>
                    <execution>
                        <id>kapt</id>
                        <goals>
                            <goal>kapt</goal>
                        </goals>
                        <configuration>
                            <sourceDirs>
                                <sourceDir>${project.basedir}/src/main</sourceDir>
                            </sourceDirs>
                            <annotationProcessorPaths>
                                <annotationProcessorPath>
                                    <groupId>com.google.dagger</groupId>
                                    <artifactId>dagger-compiler</artifactId>
                                    <version>${dagger.version}</version>
                                </annotationProcessorPath>
                            </annotationProcessorPaths>
                        </configuration>
                    </execution>
                    <execution>
                        <id>compile</id>
                        <phase>process-sources</phase>
                        <goals>
                            <goal>compile</goal>
                        </goals>
                    </execution>
                    <execution>
                        <id>test-compile</id>
                        <phase>test-compile</phase>
                        <goals>
                            <goal>test-compile</goal>
                        </goals>
                    </execution>
                </executions>
                <configuration>
                    <jvmTarget>1.8</jvmTarget>
                    <compilerPlugins>
                        <!-- Or "jpa" for JPA support -->
                        <plugin>no-arg</plugin>
                    </compilerPlugins>
                </configuration>
                <dependencies>
                    <dependency>
                        <groupId>org.jetbrains.kotlin</groupId>
                        <artifactId>kotlin-maven-noarg</artifactId>
                        <version>${kotlin.version}</version>
                    </dependency>
                </dependencies>
            </plugin>

these are the errors, there are hundred of them

[Xlint:cantFindType]
[URLClassLoader@4914000c] error can't determine annotations of missing type org.springframework.cache.annotation.Cacheable
when weaving type dagger.internal.codegen.BindingGraphValidator
when weaving classes
when weaving
 [Xlint:cantFindType]
[URLClassLoader@4914000c] error can't determine annotations of missing type org.springframework.cache.annotation.CacheEvict
when weaving type dagger.spi.DiagnosticReporter
when weaving classes
when weaving

I tried scouring the internet without any luck, so I thought i'd check and see if anyone here had insights.

Does

<data class>.copy

do anything special in terms of GC, or is it the same as allocating a new object? If I have a list of objects that are instances of data classes in a performance critical part of my code, and I need to routinely update the value of one of their fields, would I be better off making it a

var

and updating it in place, or using

copy

?

is there more info about the incremental compilation introduced in 1.2.50 ?

Kotlin plugin update arrived in Android Studio. Any info on what changed?

Is there any documentation about creating custom compilation target for Kotlin?

Hey everyone 👋 A few months ago I ran a survey about the state of Kotlin, and we just released the results in a report! You can find it here: https://pusher.com/state-of-kotlin Hope you find it interesting, and if you do - I’d really appreciate some social shares 🙂 There’s also a link to Kaggle where you can get the raw data from the responses. Also if you have any ideas of what I can do to make it better next year I’m all ears and open to feedback. Cheers!

is it possible to enforce at compile time surjectivity of a function to a sealed type (ignoring that some of the "case classes" may have properties or may be subclassed)?

What would be a good book to teach someone Kotlin with? Like a complete beginner

when will SAM conversion will be implemented in Kotlin? I mean for Kotlin SAM interfaces

You can do

unfilteredResultsCache.filterNot { it.value.timeStamp.toEpochSecond(offset) < lastHourEpoch }

, which will only create 1 new collection. Not one collection for every element removed.

let' say I have a sealed class with two options SC -> {A, B}, and I want to create an interface which takes A or B as argument. Is there any way to do so. I would like to implement this interface in a class that takes only A as argument and similarly for B.

Whats wrong with

mutablemap.entries.removeIf {}

?

hi guys, is there a channel to ask questions about datagrip or intellij, for example?

why does the mapValues[To] method pass the map entry and not only the key to the transform function?

am I going insane or do Kotlin's bitwise operations behave differently than Java's?

System.out.println((byte) -84 & 0xFF); // 172
println((-84).toByte() and (0xFF).toByte()) // -84

org.antlr.v4.runtime.ANTLRFileStream

instead of

org.antlr.runtime.ANTLRFileStream

Certainly, I can make it work by not using a

companion object

and having the class annotated with

@TestInstance(TestInstance.Lifecycle.PER_CLASS)

...but still, I would like to use the

companion object

approach. Is there any workaround for this?

not really, actually I wanted to use the ::variable.isInitialized from kotlin, which I cant

Implicit

0

returned, I didn't know this was

C

!

fun foo(): Int {
    a@when (1) {
        1 -> return@a
    }
    return 8
}

println(foo()) //prints 0

Is there a way to get compiler warnings/errors when the return values of certain functions are ignored?

If I have a

List<List<T>>

, is there a way to flatten it while adding items at the boundaries between the lists?

Ok, we’ve tried to create a new Kotlin project from scratch and just call intArrayOf() in main() function on that machine, and we’ve got the same error 😞

trying to remove duplicate items from list:

result.filterIndexed{ i, n -> nums.indexOf(n) == i }

(0 until N).reversed()

Did you mean

n downTo 0

Can i do something like this in kotlin?

products.sort {
            a,b -> }

If you know if advance you need distinct elements, use a set instead of

list.distinct()

.

Hello guys, is there separate channel or hashtag for kotlin-native?

Is it expected that this comparison returns false?

(1L as Any)::class.java == (1L)::class.java