[Compatibility] Restore old TargetPlatform and subtypes for compatibility

compiler/frontend.java/src/org/jetbrains/kotlin/platform/jvm/JvmPlatform.kt

@@ -16,11 +16,26 @@ abstract class JvmPlatform : SimplePlatform("JVM") {
         get() = "JVM "
 }
 
+@Suppress("DEPRECATION_ERROR")
 object JvmPlatforms {
+    private object UnspecifiedSimpleJvmPlatform : JvmPlatform() {
+        override val targetPlatformVersion: TargetPlatformVersion
+            get() = JvmTarget.JVM_1_6
+    }
+
+    @Deprecated(
+        message = "Should be accessed only by compatibility layer, other clients should use 'defaultJvmPlatform'",
+        level = DeprecationLevel.ERROR
+    )
+    object CompatJvmPlatform : TargetPlatform(setOf(UnspecifiedSimpleJvmPlatform)),
+        // Needed for backward compatibility, because old code uses INSTANCEOF checks instead of calling extensions
+        org.jetbrains.kotlin.resolve.jvm.platform.JvmPlatform {}
+
     private val jvmTargetToJdkPlatform: Map<JvmTarget, TargetPlatform> =
         JvmTarget.values().map { it to JdkPlatform(it).toTargetPlatform() }.toMap()
 
-    val defaultJvmPlatform: TargetPlatform = jvmTargetToJdkPlatform[JvmTarget.DEFAULT]!!
+    val defaultJvmPlatform: TargetPlatform
+        get() = CompatJvmPlatform
 
     val jvm16: TargetPlatform = jvmTargetToJdkPlatform[JvmTarget.JVM_1_6]!!
     val jvm18: TargetPlatform = jvmTargetToJdkPlatform[JvmTarget.JVM_1_8]!!

compiler/frontend.java/src/org/jetbrains/kotlin/resolve/jvm/platform/JvmPlatform.kt

@@ -0,0 +1,27 @@
+/*
+ * Copyright 2010-2019 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+@file:Suppress("DEPRECATION_ERROR")
+
+package org.jetbrains.kotlin.resolve.jvm.platform
+
+import org.jetbrains.kotlin.platform.jvm.JvmPlatforms
+import org.jetbrains.kotlin.resolve.TargetPlatform
+
+@Deprecated(
+    message = "This class is deprecated and will be removed soon, use API from 'org.jetbrains.kotlin.platform.*' packages instead",
+    replaceWith = ReplaceWith("JvmPlatforms.defaultJvmPlatform", "org.jetbrains.kotlin.platform.jvm.JvmPlatforms"),
+    level = DeprecationLevel.ERROR
+)
+interface JvmPlatform : TargetPlatform {
+    @JvmDefault
+    override val platformName: String
+        get() = "JVM"
+
+    companion object {
+        @JvmField
+        val INSTANCE: JvmPlatform = JvmPlatforms.CompatJvmPlatform
+    }
+}