HMPP: Fix serialization of TargetPlatform in Kotlin facet

core/descriptors/src/org/jetbrains/kotlin/platform/TargetPlatform.kt

@@ -57,7 +57,14 @@ open class TargetPlatform(val componentPlatforms: Set<SimplePlatform>) : Collect
  * Ideally, each specific subtype should be either a data class or singleton.
  */
 abstract class SimplePlatform(val platformName: String) {
-    override fun toString(): String = platformName
+    override fun toString(): String {
+        val targetName = targetName
+        return if (targetName.isNotEmpty()) "$platformName ($targetName)" else platformName
+    }
+
+    // description of TargetPlatformVersion or name of custom platform-specific target; used in serialization
+    open val targetName: String
+        get() = targetPlatformVersion.description
 
     /** See KDoc for [TargetPlatform.oldFashionedDescription] */
     abstract val oldFashionedDescription: String
@@ -87,4 +94,4 @@ fun TargetPlatform?.isCommon(): Boolean = this != null && size > 1 && iterator()
 
 fun SimplePlatform.toTargetPlatform(): TargetPlatform = TargetPlatform(setOf(this))
 
-fun SimplePlatform.serializeToString() = "${this.platformName} [${this.targetPlatformVersion.description}]"
+fun SimplePlatform.serializeToString(): String = "$platformName [$targetName]"

core/descriptors/src/org/jetbrains/kotlin/platform/platformUtil.kt

@@ -25,16 +25,16 @@ fun <T> TargetPlatform?.has(klass: Class<T>): Boolean = this != null && subplatf
  * also provides better description for multiplatforms.
  */
 val TargetPlatform.oldFashionedDescription: String
-    // the invocation if isCommon is not preferable as it could be governed by separate flag and may
-    // to appear independently on count of target platforms
+    // this method mistakenly detects "common native" platform as "Common (experimental)"
+    // though this does not seem to have any significant effect
     get() = this.singleOrNull()?.oldFashionedDescription ?: "Common (experimental) "
 
 
 /**
  * Renders multiplatform in form
- *      '$PLATFORM_1 / $PLATFORM_2 / ...'
+ *      '$PLATFORM_1/$PLATFORM_2/...'
  * e.g.
- *      'JVM (1.8) / JS / Native'
+ *      'JVM (1.8)/JS/Native (ios_x64)'
  */
 val TargetPlatform.presentableDescription: String
-    get() = componentPlatforms.joinToString(separator = "/")
+    get() = componentPlatforms.joinToString(separator = "/")