Add multi-platform projects as experimental language feature

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

@@ -64,6 +64,9 @@ public abstract class CommonCompilerArguments {
     @ValueDescription("<path>")
     public String[] pluginClasspaths;
 
+    @Argument(value = "Xmulti-platform", description = "Enable experimental language support for multi-platform projects")
+    public boolean multiPlatform;
+
     @Argument(value = "P", description = "Pass an option to a plugin")
     @ValueDescription(PLUGIN_OPTION_FORMAT)
     public String[] pluginOptions;

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

@@ -42,6 +42,7 @@ import org.jetbrains.kotlin.progress.ProgressIndicatorAndCompilationCanceledStat
 import org.jetbrains.kotlin.utils.StringsKt;
 
 import java.io.PrintStream;
+import java.util.ArrayList;
 import java.util.List;
 import java.util.Properties;
 
@@ -248,33 +249,46 @@ public abstract class CLICompiler<A extends CommonCompilerArguments> {
             configuration.put(CLIConfigurationKeys.COMPILER_JAR_LOCATOR, locator);
         }
 
-        LanguageVersion languageVersion = parseVersion(configuration, arguments.languageVersion, "language");
-        LanguageVersion apiVersion = parseVersion(configuration, arguments.apiVersion, "API");
-        if (languageVersion != null || apiVersion != null) {
-            if (languageVersion == null) {
-                // If only "-api-version" is specified, language version is assumed to be the latest
-                languageVersion = LanguageVersion.LATEST;
-            }
-            if (apiVersion == null) {
-                // If only "-language-version" is specified, API version is assumed to be equal to the language version
-                // (API version cannot be greater than the language version)
-                apiVersion = languageVersion;
-            }
-
-            if (apiVersion.compareTo(languageVersion) > 0) {
-                configuration.getNotNull(CLIConfigurationKeys.MESSAGE_COLLECTOR_KEY).report(
-                        CompilerMessageSeverity.ERROR,
-                        "-api-version (" + apiVersion.getVersionString() + ") cannot be greater than " +
-                        "-language-version (" + languageVersion.getVersionString() + ")",
-                        CompilerMessageLocation.NO_LOCATION
-                );
-            }
-
-            configuration.put(CommonConfigurationKeys.LANGUAGE_VERSION_SETTINGS,
-                              new LanguageVersionSettingsImpl(languageVersion, ApiVersion.createByLanguageVersion(apiVersion)));
-        }
+        setupLanguageVersionSettings(configuration, arguments);
     }
 
+    private static void setupLanguageVersionSettings(
+            @NotNull CompilerConfiguration configuration, @NotNull CommonCompilerArguments arguments
+    ) {
+        LanguageVersion languageVersion = parseVersion(configuration, arguments.languageVersion, "language");
+        LanguageVersion apiVersion = parseVersion(configuration, arguments.apiVersion, "API");
+
+        if (languageVersion == null) {
+            // If only "-api-version" is specified, language version is assumed to be the latest
+            languageVersion = LanguageVersion.LATEST;
+        }
+        if (apiVersion == null) {
+            // If only "-language-version" is specified, API version is assumed to be equal to the language version
+            // (API version cannot be greater than the language version)
+            apiVersion = languageVersion;
+        }
+
+        if (apiVersion.compareTo(languageVersion) > 0) {
+            configuration.getNotNull(CLIConfigurationKeys.MESSAGE_COLLECTOR_KEY).report(
+                    CompilerMessageSeverity.ERROR,
+                    "-api-version (" + apiVersion.getVersionString() + ") cannot be greater than " +
+                    "-language-version (" + languageVersion.getVersionString() + ")",
+                    CompilerMessageLocation.NO_LOCATION
+            );
+        }
+
+        List<LanguageFeature> extraLanguageFeatures = new ArrayList<LanguageFeature>(0);
+        if (arguments.multiPlatform) {
+            extraLanguageFeatures.add(LanguageFeature.MultiPlatformProjects);
+        }
+
+        configuration.put(
+                CommonConfigurationKeys.LANGUAGE_VERSION_SETTINGS,
+                new LanguageVersionSettingsImpl(languageVersion, ApiVersion.createByLanguageVersion(apiVersion), extraLanguageFeatures)
+        );
+    }
+
+    @Nullable
     private static LanguageVersion parseVersion(
             @NotNull CompilerConfiguration configuration, @Nullable String value, @NotNull String versionOf
     ) {

compiler/frontend/src/org/jetbrains/kotlin/diagnostics/rendering/DefaultErrorMessages.java

@@ -22,6 +22,7 @@ import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 import org.jetbrains.annotations.TestOnly;
 import org.jetbrains.kotlin.config.LanguageFeature;
+import org.jetbrains.kotlin.config.LanguageVersion;
 import org.jetbrains.kotlin.diagnostics.Diagnostic;
 import org.jetbrains.kotlin.diagnostics.DiagnosticFactory;
 import org.jetbrains.kotlin.diagnostics.Errors;
@@ -517,11 +518,14 @@ public class DefaultErrorMessages {
         MAP.put(UNSAFE_IMPLICIT_INVOKE_CALL, "Reference has a nullable type ''{0}'', use explicit ''?.invoke()'' to make a function-like call instead", RENDER_TYPE);
         MAP.put(AMBIGUOUS_LABEL, "Ambiguous label");
         MAP.put(UNSUPPORTED, "Unsupported [{0}]", STRING);
-        MAP.put(UNSUPPORTED_FEATURE, "The feature is only available since Kotlin {0}", new DiagnosticParameterRenderer<LanguageFeature>() {
+        MAP.put(UNSUPPORTED_FEATURE, "The feature is {0}", new DiagnosticParameterRenderer<LanguageFeature>() {
             @NotNull
             @Override
             public String render(LanguageFeature feature, @NotNull RenderingContext renderingContext) {
-                return feature.getSinceVersion().getVersionString() + ": " + feature.getPresentableText();
+                LanguageVersion version = feature.getSinceVersion();
+                return version != null
+                       ? "only available since Kotlin " + version.getVersionString() + ": " + feature.getPresentableText()
+                       : "experimental and should be turned on explicitly via a command line option or in IDE settings: " + feature.getPresentableText();
             }
         });
         MAP.put(EXCEPTION_FROM_ANALYZER, "Internal Error occurred while analyzing this expression:\n{0}", THROWABLE);

compiler/testData/cli/js/jsExtraHelp.out

@@ -3,6 +3,7 @@ where advanced options include:
   -Xno-inline                Disable method inlining
   -Xrepeat <count>           Repeat compilation (for performance analysis)
   -Xplugin <path>            Load plugins from the given classpath
+  -Xmulti-platform           Enable experimental language support for multi-platform projects
 
 Advanced options are non-standard and may be changed or removed without any notice.
 OK

compiler/testData/cli/jvm/extraHelp.out

@@ -16,6 +16,7 @@ where advanced options include:
   -Xno-inline                Disable method inlining
   -Xrepeat <count>           Repeat compilation (for performance analysis)
   -Xplugin <path>            Load plugins from the given classpath
+  -Xmulti-platform           Enable experimental language support for multi-platform projects
 
 Advanced options are non-standard and may be changed or removed without any notice.
 OK

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

@@ -16,13 +16,11 @@
 
 package org.jetbrains.kotlin.config
 
-import com.intellij.openapi.module.Module
-import com.intellij.util.text.VersionComparatorUtil
 import org.jetbrains.kotlin.config.LanguageVersion.KOTLIN_1_1
 import org.jetbrains.kotlin.utils.DescriptionAware
 
-enum class LanguageFeature(val sinceVersion: LanguageVersion) {
-    // Note: names of these entries are also used in diagnostic tests
+enum class LanguageFeature(val sinceVersion: LanguageVersion?) {
+    // Note: names of these entries are also used in diagnostic tests and in user-visible messages (see presentableText below)
     TypeAliases(KOTLIN_1_1),
     BoundCallableReferences(KOTLIN_1_1),
     LocalDelegatedProperties(KOTLIN_1_1),
@@ -34,7 +32,10 @@ enum class LanguageFeature(val sinceVersion: LanguageVersion) {
     DestructuringLambdaParameters(KOTLIN_1_1),
     SingleUnderscoreForParameterName(KOTLIN_1_1),
     DslMarkersSupport(KOTLIN_1_1),
-    UnderscoresInNumericLiterals(KOTLIN_1_1)
+    UnderscoresInNumericLiterals(KOTLIN_1_1),
+
+    // Experimental features
+    MultiPlatformProjects(null),
     ;
 
     val presentableText: String
@@ -74,15 +75,22 @@ interface LanguageVersionSettings {
     val apiVersion: ApiVersion
 }
 
-class LanguageVersionSettingsImpl(
+class LanguageVersionSettingsImpl @JvmOverloads constructor(
         private val languageVersion: LanguageVersion,
-        override val apiVersion: ApiVersion
+        override val apiVersion: ApiVersion,
+        additionalFeatures: Collection<LanguageFeature> = emptySet()
 ) : LanguageVersionSettings {
+    private val additionalFeatures = additionalFeatures.toSet()
+
     override fun supportsFeature(feature: LanguageFeature): Boolean {
-        return languageVersion >= feature.sinceVersion
+        val since = feature.sinceVersion
+        return (since != null && languageVersion >= since) || feature in additionalFeatures
     }
 
-    override fun toString() = "Language = $languageVersion, API = $apiVersion"
+    override fun toString() = buildString {
+        append("Language = $languageVersion, API = $apiVersion")
+        additionalFeatures.forEach { feature -> append(" +$feature") }
+    }
 
     companion object {
         @JvmField