Add -Xeffect-system CLI argument which enables Effect System

compiler/cli/cli-common/src/org/jetbrains/kotlin/cli/common/arguments/CommonCompilerArguments.kt

@@ -118,6 +118,12 @@ abstract class CommonCompilerArguments : CommonToolArguments() {
     )
     var legacySmartCastAfterTry by FreezableVar(false)
 
+    @Argument(
+            value = "-Xeffect-system",
+            description = "Enable experimental language feature: effect system"
+    )
+    var effectSystem: Boolean by FreezableVar(false)
+
     open fun configureAnalysisFlags(collector: MessageCollector): MutableMap<AnalysisFlag<*>, Any> {
         return HashMap<AnalysisFlag<*>, Any>().apply {
             put(AnalysisFlag.skipMetadataVersionCheck, skipMetadataVersionCheck)

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

@@ -212,6 +212,12 @@ public abstract class CLICompiler<A extends CommonCompilerArguments> extends CLI
             extraLanguageFeatures.put(LanguageFeature.SoundSmartCastsAfterTry, LanguageFeature.State.DISABLED);
         }
 
+        if (arguments.getEffectSystem()) {
+            extraLanguageFeatures.put(LanguageFeature.CallsInPlaceEffect, LanguageFeature.State.ENABLED);
+            extraLanguageFeatures.put(LanguageFeature.ReturnsEffect, LanguageFeature.State.ENABLED);
+        }
+
+
         setupPlatformSpecificLanguageFeatureSettings(extraLanguageFeatures, arguments);
 
         CommonConfigurationKeysKt.setLanguageVersionSettings(configuration, new LanguageVersionSettingsImpl(