Fix warnings generated by kotlin 2.0.20

Author: nedtwigg

jvm/selfie-lib/build.gradle

@@ -31,6 +31,11 @@ kotlin {
         compileOnly("org.jetbrains.kotlinx:kotlinx-serialization-json:$ver_KOTLIN_SERIALIZATION")
       }
     }
+    jsMain {
+      dependencies {
+        api("org.jetbrains.kotlinx:kotlinx-serialization-json:$ver_KOTLIN_SERIALIZATION")
+      }
+    }
     commonTest {
       dependencies {
         implementation kotlin('test')

jvm/selfie-lib/src/commonMain/kotlin/com/diffplug/selfie/Roundtrip.kt

@@ -32,6 +32,7 @@ interface Roundtrip<T, SerializedForm> {
 /** Roundtrips the given type into pretty-printed Json. */
 class RoundtripJson<T>(private val strategy: kotlinx.serialization.KSerializer<T>) :
     Roundtrip<T, String> {
+  @OptIn(kotlinx.serialization.ExperimentalSerializationApi::class)
   private val json =
       kotlinx.serialization.json.Json {
         prettyPrint = true

jvm/selfie-lib/src/commonMain/kotlin/com/diffplug/selfie/SnapshotFile.kt

@@ -63,6 +63,7 @@ internal data class SnapshotValueString(val value: String) : SnapshotValue {
   override fun toString(): String = value
 }
 
+@ConsistentCopyVisibility
 data class Snapshot
 private constructor(
     val subject: SnapshotValue,