[Compatibility] Restore KotlinFacetSettings.getTargetPlatform()

idea/idea-jps-common/src/org/jetbrains/kotlin/config/KotlinFacetSettings.kt

@@ -25,6 +25,7 @@ import org.jetbrains.kotlin.cli.common.arguments.parseCommandLineArguments
 import org.jetbrains.kotlin.platform.IdePlatformKind
 import org.jetbrains.kotlin.platform.TargetPlatformVersion
 import org.jetbrains.kotlin.platform.TargetPlatform
+import org.jetbrains.kotlin.platform.compat.toIdePlatform
 import org.jetbrains.kotlin.utils.DescriptionAware
 
 @Deprecated("Use IdePlatformKind instead.", level = DeprecationLevel.ERROR)
@@ -194,6 +195,16 @@ class KotlinFacetSettings {
             return IdePlatformKind.platformByCompilerArguments(compilerArguments)
         }
 
+    @Suppress("DEPRECATION_ERROR")
+    @Deprecated(
+        message = "This accessor is deprecated and will be removed soon, use API from 'org.jetbrains.kotlin.platform.*' packages instead",
+        replaceWith = ReplaceWith("targetPlatform"),
+        level = DeprecationLevel.ERROR
+    )
+    fun getPlatform(): org.jetbrains.kotlin.platform.IdePlatform<*, *>? {
+        return platform?.toIdePlatform()
+    }
+
     var coroutineSupport: LanguageFeature.State?
         get() {
             val languageVersion = languageLevel ?: return LanguageFeature.Coroutines.defaultState

idea/idea-jps-common/src/org/jetbrains/kotlin/platform/compat/compatConversions.kt

@@ -7,6 +7,7 @@
 
 package org.jetbrains.kotlin.platform.compat
 
+import org.jetbrains.kotlin.config.JvmTarget
 import org.jetbrains.kotlin.platform.CommonPlatforms
 import org.jetbrains.kotlin.platform.IdePlatform
 import org.jetbrains.kotlin.platform.impl.CommonIdePlatformKind
@@ -46,7 +47,6 @@ fun OldPlatform.toNewPlatform(): NewPlatform = when (this) {
     )
 }
 
-
 fun IdePlatform<*, *>.toNewPlatform(): NewPlatform = when (this) {
     is CommonIdePlatformKind.Platform -> CommonPlatforms.defaultCommonPlatform
     is JvmIdePlatformKind.Platform -> JvmPlatforms.jvmPlatformByTargetVersion(this.version)
@@ -54,3 +54,12 @@ fun IdePlatform<*, *>.toNewPlatform(): NewPlatform = when (this) {
     is NativeIdePlatformKind.Platform -> KonanPlatforms.defaultKonanPlatform
     else -> error("Unknown platform $this")
 }
+
+fun NewPlatform.toIdePlatform(): IdePlatform<*, *> = when (val single = singleOrNull()) {
+    null -> CommonIdePlatformKind.Platform
+    is JdkPlatform -> JvmIdePlatformKind.Platform(single.targetVersion)
+    is JvmPlatform -> JvmIdePlatformKind.Platform(JvmTarget.DEFAULT)
+    is JsPlatform -> JsIdePlatformKind.Platform
+    is KonanPlatform -> NativeIdePlatformKind.Platform
+    else -> error("Unknown platform $single")
+}