Introduce language version 2.0 and associate K2 compiler with it

compiler/tests-common/tests/org/jetbrains/kotlin/checkers/CompilerTestLanguageVersionSettings.kt

@@ -26,19 +26,23 @@ const val SANITIZE_PARENTHESES = "SANITIZE_PARENTHESES"
 const val ENABLE_JVM_PREVIEW = "ENABLE_JVM_PREVIEW"
 
 data class CompilerTestLanguageVersionSettings(
-        private val initialLanguageFeatures: Map<LanguageFeature, LanguageFeature.State>,
-        override val apiVersion: ApiVersion,
-        override val languageVersion: LanguageVersion,
-        val analysisFlags: Map<AnalysisFlag<*>, Any?> = emptyMap()
+    private val initialLanguageFeatures: Map<LanguageFeature, LanguageFeature.State>,
+    override val apiVersion: ApiVersion,
+    override val languageVersion: LanguageVersion,
+    val analysisFlags: Map<AnalysisFlag<*>, Any?> = emptyMap()
 ) : LanguageVersionSettings {
     val extraLanguageFeatures = specificFeaturesForTests() + initialLanguageFeatures
     private val delegate = LanguageVersionSettingsImpl(languageVersion, apiVersion, emptyMap(), extraLanguageFeatures)
 
     override fun getFeatureSupport(feature: LanguageFeature): LanguageFeature.State =
-            extraLanguageFeatures[feature] ?: delegate.getFeatureSupport(feature)
+        extraLanguageFeatures[feature] ?: delegate.getFeatureSupport(feature)
 
     override fun isPreRelease(): Boolean = false
 
+    override fun copy(languageVersion: LanguageVersion): LanguageVersionSettings {
+        return CompilerTestLanguageVersionSettings(initialLanguageFeatures, apiVersion, languageVersion, analysisFlags)
+    }
+
     @Suppress("UNCHECKED_CAST")
     override fun <T> getFlag(flag: AnalysisFlag<T>): T = analysisFlags[flag] as T? ?: flag.defaultValue
 }

compiler/tests-common/tests/org/jetbrains/kotlin/jvm/compiler/AbstractKotlinCompilerIntegrationTest.kt

@@ -138,7 +138,7 @@ abstract class AbstractKotlinCompilerIntegrationTest : TestCaseWithTmpdir() {
 
     private fun String.removeFirWarning(): String {
         return this.replace(
-            "warning: ATTENTION!\n This build uses experimental K2 compiler: \n  -Xuse-k2\n", ""
+            "warning: language version 2.0 is experimental, there are no backwards compatibility guarantees for new language and library features\n", ""
         )
     }