K2 tests: always use language version 2.0 or higher

compiler/test-infrastructure/tests/org/jetbrains/kotlin/test/builders/LanguageVersionSettingsBuilder.kt

@@ -53,7 +53,8 @@ class LanguageVersionSettingsBuilder {
     fun configureUsingDirectives(
         directives: RegisteredDirectives,
         environmentConfigurators: List<AbstractEnvironmentConfigurator>,
-        targetBackend: TargetBackend?
+        targetBackend: TargetBackend?,
+        useK2: Boolean
     ) {
         val apiVersion = directives.singleOrZeroValue(LanguageSettingsDirectives.API_VERSION)
         if (apiVersion != null) {
@@ -61,6 +62,10 @@ class LanguageVersionSettingsBuilder {
             val languageVersion = maxOf(LanguageVersion.LATEST_STABLE, LanguageVersion.fromVersionString(apiVersion.versionString)!!)
             this.languageVersion = languageVersion
         }
+        when {
+            useK2 && this.languageVersion < LanguageVersion.KOTLIN_2_0 -> this.languageVersion = LanguageVersion.KOTLIN_2_0
+            !useK2 && this.languageVersion > LanguageVersion.KOTLIN_1_9 -> this.languageVersion = LanguageVersion.KOTLIN_1_9
+        }
 
         val analysisFlags = listOfNotNull(
             analysisFlag(AnalysisFlags.optIn, directives[LanguageSettingsDirectives.OPT_IN].takeIf { it.isNotEmpty() }),

compiler/tests-common-new/tests/org/jetbrains/kotlin/test/services/impl/ModuleStructureExtractorImpl.kt

@@ -334,7 +334,11 @@ class ModuleStructureExtractorImpl(
             moduleDirectives.forEach { it.checkDirectiveApplicability(contextIsGlobal = isImplicitModule, contextIsModule = true) }
 
             val targetBackend = currentModuleTargetBackend ?: defaultsProvider.defaultTargetBackend
-            currentModuleLanguageVersionSettingsBuilder.configureUsingDirectives(moduleDirectives, environmentConfigurators, targetBackend)
+            val frontendKind = currentModuleFrontendKind ?: defaultsProvider.defaultFrontend
+
+            currentModuleLanguageVersionSettingsBuilder.configureUsingDirectives(
+                moduleDirectives, environmentConfigurators, targetBackend, useK2 = frontendKind == FrontendKinds.FIR
+            )
             val moduleName = currentModuleName
                 ?: testServices.defaultDirectives[ModuleStructureDirectives.MODULE].firstOrNull()
                 ?: DEFAULT_MODULE_NAME