Show LV=1.2 in IDE only in internal mode

compiler/cli/src/org/jetbrains/kotlin/cli/common/CLICompiler.java

@@ -253,7 +253,7 @@ public abstract class CLICompiler<A extends CommonCompilerArguments> {
             );
         }
 
-        if (languageVersion.compareTo(LanguageVersion.LATEST_STABLE) > 0) {
+        if (!languageVersion.isStable()) {
             configuration.getNotNull(CLIConfigurationKeys.MESSAGE_COLLECTOR_KEY).report(
                     CompilerMessageSeverity.STRONG_WARNING,
                     "Language version " + languageVersion.getVersionString() + " is experimental, there are " +

compiler/util/src/org/jetbrains/kotlin/config/LanguageVersionSettings.kt

@@ -83,11 +83,14 @@ enum class LanguageVersion(val major: Int, val minor: Int) : DescriptionAware {
     KOTLIN_1_1(1, 1),
     KOTLIN_1_2(1, 2);
 
+    val isStable: Boolean
+        get() = this <= LATEST_STABLE
+
     val versionString: String
         get() = "$major.$minor"
 
     override val description: String
-        get() = if (this > LATEST_STABLE) "$versionString (EXPERIMENTAL)" else versionString
+        get() = if (isStable) versionString else "$versionString (EXPERIMENTAL)"
 
     override fun toString() = versionString
 

idea/src/org/jetbrains/kotlin/idea/compiler/configuration/KotlinCompilerConfigurableTab.java

@@ -50,6 +50,7 @@ import org.jetbrains.kotlin.cli.common.arguments.K2JsArgumentConstants;
 import org.jetbrains.kotlin.config.*;
 import org.jetbrains.kotlin.idea.KotlinBundle;
 import org.jetbrains.kotlin.idea.PluginStartupComponent;
+import org.jetbrains.kotlin.idea.actions.internal.KotlinInternalMode;
 import org.jetbrains.kotlin.idea.facet.DescriptionListCellRenderer;
 import org.jetbrains.kotlin.idea.facet.KotlinFacet;
 import org.jetbrains.kotlin.idea.util.application.ApplicationUtilsKt;
@@ -334,6 +335,10 @@ public class KotlinCompilerConfigurableTab implements SearchableConfigurable, Co
     @SuppressWarnings("unchecked")
     private void fillLanguageAndAPIVersionList() {
         for (LanguageVersion version : LanguageVersion.values()) {
+            if (!version.isStable() && !KotlinInternalMode.Instance.getEnabled()) {
+                continue;
+            }
+
             languageVersionComboBox.addItem(version.getDescription());
             apiVersionComboBox.addItem(version.getDescription());
         }

idea/src/org/jetbrains/kotlin/idea/quickfix/EnableUnsupportedFeatureFix.kt

@@ -35,6 +35,7 @@ import org.jetbrains.kotlin.config.LanguageVersion
 import org.jetbrains.kotlin.diagnostics.Diagnostic
 import org.jetbrains.kotlin.diagnostics.Errors
 import org.jetbrains.kotlin.idea.KotlinPluginUtil
+import org.jetbrains.kotlin.idea.actions.internal.KotlinInternalMode
 import org.jetbrains.kotlin.idea.compiler.configuration.KotlinCommonCompilerArgumentsHolder
 import org.jetbrains.kotlin.idea.configuration.KotlinWithGradleConfigurator
 import org.jetbrains.kotlin.idea.facet.KotlinFacet
@@ -146,6 +147,10 @@ sealed class EnableUnsupportedFeatureFix(
             val apiVersionOnly = sinceVersion <= languageFeatureSettings.languageVersion &&
                                  feature.sinceApiVersion > languageFeatureSettings.apiVersion
 
+            if (!sinceVersion.isStable && !KotlinInternalMode.enabled) {
+                return null
+            }
+
             val module = ModuleUtilCore.findModuleForPsiElement(diagnostic.psiElement) ?: return null
             if (KotlinPluginUtil.isMavenModule(module)) return null
             if (!KotlinPluginUtil.isGradleModule(module)) {