Require "-Xuse-experimental=kotlin.Experimental" on usages of Experimental

Since we're not yet sure of the design of Experimental/UseExperimental,
we're making them "experimental" themselves in some sense, in that the
user is required to provide the magic argument
"-Xuse-experimental=kotlin.Experimental" to be allowed to use either
Experimental or UseExperimental. This is more convenient than the
previous approach of "-language-version 1.3
-Xskip-metadata-version-check" because it's simpler and does not cause
pre-release binaries to be produced

compiler/frontend/src/org/jetbrains/kotlin/diagnostics/Errors.java

@@ -240,6 +240,7 @@ public interface Errors {
     DiagnosticFactory2<PsiElement, FqName, DeclarationDescriptor> EXPERIMENTAL_OVERRIDE = DiagnosticFactory2.create(WARNING);
     DiagnosticFactory2<PsiElement, FqName, DeclarationDescriptor> EXPERIMENTAL_OVERRIDE_ERROR = DiagnosticFactory2.create(ERROR);
 
+    DiagnosticFactory0<PsiElement> EXPERIMENTAL_IS_NOT_ENABLED = DiagnosticFactory0.create(ERROR);
     DiagnosticFactory0<KtAnnotationEntry> USE_EXPERIMENTAL_WITHOUT_ARGUMENTS = DiagnosticFactory0.create(WARNING);
     DiagnosticFactory1<KtAnnotationEntry, FqName> USE_EXPERIMENTAL_ARGUMENT_IS_NOT_MARKER = DiagnosticFactory1.create(WARNING);
     DiagnosticFactory1<KtAnnotationEntry, String> EXPERIMENTAL_ANNOTATION_WITH_WRONG_TARGET = DiagnosticFactory1.create(ERROR);

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

@@ -146,6 +146,7 @@ public class DefaultErrorMessages {
         MAP.put(EXPERIMENTAL_OVERRIDE, "This declaration overrides experimental member of supertype ''{1}'' and should be annotated with ''@{0}''", TO_STRING, NAME);
         MAP.put(EXPERIMENTAL_OVERRIDE_ERROR, "This declaration overrides experimental member of supertype ''{1}'' and must be annotated with ''@{0}''", TO_STRING, NAME);
 
+        MAP.put(EXPERIMENTAL_IS_NOT_ENABLED, "This class can only be used with the compiler argument '-Xuse-experimental=kotlin.Experimental'");
         MAP.put(USE_EXPERIMENTAL_WITHOUT_ARGUMENTS, "@UseExperimental without any arguments has no effect");
         MAP.put(USE_EXPERIMENTAL_ARGUMENT_IS_NOT_MARKER, "Annotation ''{0}'' is not an experimental API marker, therefore its usage in @UseExperimental is ignored", TO_STRING);
         MAP.put(EXPERIMENTAL_ANNOTATION_WITH_WRONG_TARGET, "Experimental annotation cannot be used on the following code elements: {0}. Please remove these targets", STRING);

compiler/frontend/src/org/jetbrains/kotlin/resolve/checkers/ExperimentalUsageChecker.kt

@@ -37,6 +37,7 @@ import org.jetbrains.kotlin.resolve.constants.EnumValue
 import org.jetbrains.kotlin.resolve.constants.KClassValue
 import org.jetbrains.kotlin.resolve.descriptorUtil.annotationClass
 import org.jetbrains.kotlin.resolve.descriptorUtil.fqNameSafe
+import org.jetbrains.kotlin.resolve.descriptorUtil.fqNameUnsafe
 import org.jetbrains.kotlin.resolve.descriptorUtil.module
 import org.jetbrains.kotlin.storage.LockBasedStorageManager
 import org.jetbrains.kotlin.utils.SmartSet
@@ -67,6 +68,9 @@ class ExperimentalUsageChecker(project: Project) : CallChecker {
         private val WARNING_LEVEL = Name.identifier("WARNING")
         private val ERROR_LEVEL = Name.identifier("ERROR")
 
+        private val EXPERIMENTAL_SHORT_NAME = EXPERIMENTAL_FQ_NAME.shortName()
+        private val USE_EXPERIMENTAL_SHORT_NAME = USE_EXPERIMENTAL_FQ_NAME.shortName()
+
         private fun reportNotAcceptedExperimentalities(
             experimentalities: Collection<Experimentality>, element: PsiElement, context: CheckerContext
         ) {
@@ -196,7 +200,9 @@ class ExperimentalUsageChecker(project: Project) : CallChecker {
             }
 
             val validExperimental = languageVersionSettings.getFlag(AnalysisFlag.experimental).filter(::checkAnnotation)
-            val validUseExperimental = languageVersionSettings.getFlag(AnalysisFlag.useExperimental).filter(::checkAnnotation)
+            val validUseExperimental = languageVersionSettings.getFlag(AnalysisFlag.useExperimental).filter { fqName ->
+                fqName == EXPERIMENTAL_FQ_NAME.asString() || checkAnnotation(fqName)
+            }
 
             for (fqName in validExperimental.intersect(validUseExperimental)) {
                 reportError("'-Xuse-experimental=$fqName' has no effect because '-Xexperimental=$fqName' is used")
@@ -208,9 +214,24 @@ class ExperimentalUsageChecker(project: Project) : CallChecker {
         private val moduleAnnotationsResolver = ModuleAnnotationsResolver.getInstance(project)
 
         override fun check(targetDescriptor: ClassifierDescriptor, element: PsiElement, context: ClassifierUsageCheckerContext) {
+            val name = targetDescriptor.name
+            if (name == EXPERIMENTAL_SHORT_NAME || name == USE_EXPERIMENTAL_SHORT_NAME) {
+                val fqName = targetDescriptor.fqNameUnsafe
+                if (fqName == EXPERIMENTAL_FQ_NAME.toUnsafe() || fqName == USE_EXPERIMENTAL_FQ_NAME.toUnsafe()) {
+                    checkUsageOfKotlinExperimentalOrUseExperimental(element, context)
+                    return
+                }
+            }
+
             val experimentalities = targetDescriptor.loadExperimentalities(moduleAnnotationsResolver)
             reportNotAcceptedExperimentalities(experimentalities, element, context)
         }
+
+        private fun checkUsageOfKotlinExperimentalOrUseExperimental(element: PsiElement, context: CheckerContext) {
+            if (EXPERIMENTAL_FQ_NAME.asString() !in context.languageVersionSettings.getFlag(AnalysisFlag.useExperimental)) {
+                context.trace.report(Errors.EXPERIMENTAL_IS_NOT_ENABLED.on(element))
+            }
+        }
     }
 
     class Overrides(project: Project) : DeclarationChecker {

compiler/testData/cli/jvm/experimentalAndUseExperimentalWithSameAnnotation.args

@@ -1,8 +1,6 @@
 $TESTDATA_DIR$/experimentalAndUseExperimentalWithSameAnnotation.kt
 -d
 $TEMP_DIR$
--Xskip-runtime-version-check
+-Xuse-experimental=kotlin.Experimental
--language-version
-1.3
 -Xexperimental=org.test.ExperimentalAPI
 -Xuse-experimental=org.test.ExperimentalAPI

compiler/testData/cli/jvm/experimentalAndUseExperimentalWithSameAnnotation.out

@@ -1,3 +1,2 @@
-warning: language version 1.3 is experimental, there are no backwards compatibility guarantees for new language and library features
 error: '-Xuse-experimental=org.test.ExperimentalAPI' has no effect because '-Xexperimental=org.test.ExperimentalAPI' is used
 COMPILATION_ERROR

compiler/testData/cli/jvm/experimentalDeprecated.args

@@ -1,9 +1,7 @@
 $TESTDATA_DIR$/experimentalDeprecated.kt
 -d
 $TEMP_DIR$
--Xskip-runtime-version-check
+-Xuse-experimental=kotlin.Experimental
--language-version
-1.3
 -Xexperimental=org.test.Error1
 -Xexperimental=org.test.Hidden1
 -Xuse-experimental=org.test.Error2

compiler/testData/cli/jvm/experimentalDeprecated.out

@@ -1,4 +1,3 @@
-warning: language version 1.3 is experimental, there are no backwards compatibility guarantees for new language and library features
 error: experimental API marker org.test.Error1 is deprecated. Error1
 error: experimental API marker org.test.Hidden1 is deprecated. Hidden1
 error: experimental API marker org.test.Error2 is deprecated. Error2

compiler/testData/cli/jvm/experimentalDeprecatedWarning.args

@@ -1,8 +1,6 @@
 $TESTDATA_DIR$/experimentalDeprecatedWarning.kt
 -d
 $TEMP_DIR$
--Xskip-runtime-version-check
+-Xuse-experimental=kotlin.Experimental
--language-version
-1.3
 -Xuse-experimental=org.test.Warning1
 -Xexperimental=org.test.Warning2

compiler/testData/cli/jvm/experimentalDeprecatedWarning.out

@@ -1,4 +1,3 @@
-warning: language version 1.3 is experimental, there are no backwards compatibility guarantees for new language and library features
 warning: experimental API marker org.test.Warning2 is deprecated. Warning2
 warning: experimental API marker org.test.Warning1 is deprecated. Warning1
 OK

compiler/testData/cli/jvm/experimentalNested.args

@@ -1,7 +1,5 @@
 $TESTDATA_DIR$/experimentalNested.kt
 -d
 $TEMP_DIR$
--Xskip-runtime-version-check
+-Xuse-experimental=kotlin.Experimental
--language-version
-1.3
 -Xexperimental=org.test.Outer.Nested

compiler/testData/cli/jvm/experimentalNested.out

@@ -1,2 +1 @@
-warning: language version 1.3 is experimental, there are no backwards compatibility guarantees for new language and library features
 OK

compiler/testData/diagnostics/testsWithStdLib/experimental/annotation.kt

@@ -1,4 +1,4 @@
-// !API_VERSION: 1.3
+// !USE_EXPERIMENTAL: kotlin.Experimental
 // !DIAGNOSTICS: -UNUSED_PARAMETER
 // FILE: api.kt
 

compiler/testData/diagnostics/testsWithStdLib/experimental/bodyUsages.kt

@@ -1,4 +1,4 @@
-// !API_VERSION: 1.3
+// !USE_EXPERIMENTAL: kotlin.Experimental
 // FILE: api.kt
 
 package api

compiler/testData/diagnostics/testsWithStdLib/experimental/classMembers.kt

@@ -1,4 +1,4 @@
-// !API_VERSION: 1.3
+// !USE_EXPERIMENTAL: kotlin.Experimental
 // FILE: api.kt
 
 package api

compiler/testData/diagnostics/testsWithStdLib/experimental/classMembersOverlyExperimental.kt

@@ -1,4 +1,4 @@
-// !API_VERSION: 1.3
+// !USE_EXPERIMENTAL: kotlin.Experimental
 // FILE: api.kt
 
 package api

compiler/testData/diagnostics/testsWithStdLib/experimental/constVal.kt

@@ -1,4 +1,4 @@
-// !API_VERSION: 1.3
+// !USE_EXPERIMENTAL: kotlin.Experimental
 // FILE: api.kt
 
 package api

compiler/testData/diagnostics/testsWithStdLib/experimental/deeplyNestedClass.kt

@@ -1,4 +1,4 @@
-// !API_VERSION: 1.3
+// !USE_EXPERIMENTAL: kotlin.Experimental
 // FILE: api.kt
 
 package api

compiler/testData/diagnostics/testsWithStdLib/experimental/errors.kt

@@ -1,4 +1,4 @@
-// !API_VERSION: 1.3
+// !USE_EXPERIMENTAL: kotlin.Experimental
 // FILE: api.kt
 
 package api

compiler/testData/diagnostics/testsWithStdLib/experimental/experimentalIsNotEnabled.kt

@@ -0,0 +1,23 @@
+// FILE: api.kt
+
+@<!EXPERIMENTAL_IS_NOT_ENABLED!>Experimental<!>
+annotation class Marker
+
+@Marker
+fun f() {}
+
+// FILE: usage.kt
+
+fun use1() {
+    <!EXPERIMENTAL_API_USAGE_ERROR!>f<!>()
+}
+
+@Marker
+fun use2() {
+    f()
+}
+
+@<!EXPERIMENTAL_IS_NOT_ENABLED!>UseExperimental<!>(Marker::class)
+fun use3() {
+    f()
+}

compiler/testData/diagnostics/testsWithStdLib/experimental/experimentalIsNotEnabled.txt

@@ -0,0 +1,13 @@
+package
+
+@Marker public fun f(): kotlin.Unit
+public fun use1(): kotlin.Unit
+@Marker public fun use2(): kotlin.Unit
+@kotlin.UseExperimental(markerClass = {Marker::class}) public fun use3(): kotlin.Unit
+
+@kotlin.Experimental public final annotation class Marker : kotlin.Annotation {
+    public constructor Marker()
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}

compiler/testData/diagnostics/testsWithStdLib/experimental/experimentalOnWholeModule.kt

@@ -1,4 +1,4 @@
-// !API_VERSION: 1.3
+// !USE_EXPERIMENTAL: kotlin.Experimental
 // !EXPERIMENTAL: api.ExperimentalAPI
 // MODULE: api
 // FILE: api.kt

compiler/testData/diagnostics/testsWithStdLib/experimental/incorrectTargetsForExperimentalAnnotation.kt

@@ -1,4 +1,4 @@
-// !API_VERSION: 1.3
+// !USE_EXPERIMENTAL: kotlin.Experimental
 // FILE: api.kt
 
 package api

compiler/testData/diagnostics/testsWithStdLib/experimental/incorrectUseExperimental.kt

@@ -1,4 +1,4 @@
-// !API_VERSION: 1.3
+// !USE_EXPERIMENTAL: kotlin.Experimental
 
 <!USE_EXPERIMENTAL_WITHOUT_ARGUMENTS!>@UseExperimental<!>
 fun f1() {}

compiler/testData/diagnostics/testsWithStdLib/experimental/override.kt

@@ -1,4 +1,4 @@
-// !API_VERSION: 1.3
+// !USE_EXPERIMENTAL: kotlin.Experimental
 // FILE: api.kt
 
 package api

compiler/testData/diagnostics/testsWithStdLib/experimental/overrideDifferentExperimentalities.kt

@@ -1,4 +1,4 @@
-// !API_VERSION: 1.3
+// !USE_EXPERIMENTAL: kotlin.Experimental
 
 @Experimental(Experimental.Level.WARNING)
 annotation class E1

compiler/testData/diagnostics/testsWithStdLib/experimental/scripts.kt

@@ -1,4 +1,4 @@
-// !API_VERSION: 1.3
+// !USE_EXPERIMENTAL: kotlin.Experimental
 // !DIAGNOSTICS: -UNUSED_VARIABLE
 // FILE: api.kt
 

compiler/testData/diagnostics/testsWithStdLib/experimental/topLevel.kt

@@ -1,4 +1,4 @@
-// !API_VERSION: 1.3
+// !USE_EXPERIMENTAL: kotlin.Experimental
 // !DIAGNOSTICS: -UNUSED_VARIABLE
 // FILE: api.kt
 

compiler/testData/diagnostics/testsWithStdLib/experimental/typealias.kt

@@ -1,4 +1,4 @@
-// !API_VERSION: 1.3
+// !USE_EXPERIMENTAL: kotlin.Experimental
 // FILE: api.kt
 
 package api

compiler/testData/diagnostics/testsWithStdLib/experimental/useExperimentalOnFile.kt

@@ -1,4 +1,4 @@
-// !API_VERSION: 1.3
+// !USE_EXPERIMENTAL: kotlin.Experimental
 // FILE: api.kt
 
 package api

compiler/testData/diagnostics/testsWithStdLib/experimental/useExperimentalOnFileWithVeryExperimentalMarker.kt

@@ -1,4 +1,4 @@
-// !API_VERSION: 1.3
+// !USE_EXPERIMENTAL: kotlin.Experimental
 // FILE: api.kt
 
 package api

compiler/testData/diagnostics/testsWithStdLib/experimental/useExperimentalOnWholeModule.kt

@@ -1,5 +1,4 @@
-// !API_VERSION: 1.3
+// !USE_EXPERIMENTAL: kotlin.Experimental api.ExperimentalAPI
-// !USE_EXPERIMENTAL: api.ExperimentalAPI
 // MODULE: api
 // FILE: api.kt
 

compiler/testData/diagnostics/testsWithStdLib/experimental/useExperimentalTargets.kt

@@ -1,4 +1,4 @@
-// !API_VERSION: 1.3
+// !USE_EXPERIMENTAL: kotlin.Experimental
 // !DIAGNOSTICS: -UNUSED_PARAMETER
 // FILE: api.kt
 

compiler/testData/diagnostics/testsWithStdLib/experimental/useExperimentalWithSeveralAnnotations.kt

@@ -1,4 +1,4 @@
-// !API_VERSION: 1.3
+// !USE_EXPERIMENTAL: kotlin.Experimental
 // FILE: api.kt
 
 package api

compiler/tests/org/jetbrains/kotlin/checkers/DiagnosticsTestWithStdLibGenerated.java

@@ -2112,6 +2112,11 @@ public class DiagnosticsTestWithStdLibGenerated extends AbstractDiagnosticsTestW
             runTest("compiler/testData/diagnostics/testsWithStdLib/experimental/errors.kt");
         }
 
+        @TestMetadata("experimentalIsNotEnabled.kt")
+        public void testExperimentalIsNotEnabled() throws Exception {
+            runTest("compiler/testData/diagnostics/testsWithStdLib/experimental/experimentalIsNotEnabled.kt");
+        }
+
         @TestMetadata("experimentalOnWholeModule.kt")
         public void testExperimentalOnWholeModule() throws Exception {
             runTest("compiler/testData/diagnostics/testsWithStdLib/experimental/experimentalOnWholeModule.kt");

compiler/tests/org/jetbrains/kotlin/checkers/javac/DiagnosticsTestWithStdLibUsingJavacGenerated.java

@@ -2112,6 +2112,11 @@ public class DiagnosticsTestWithStdLibUsingJavacGenerated extends AbstractDiagno
             runTest("compiler/testData/diagnostics/testsWithStdLib/experimental/errors.kt");
         }
 
+        @TestMetadata("experimentalIsNotEnabled.kt")
+        public void testExperimentalIsNotEnabled() throws Exception {
+            runTest("compiler/testData/diagnostics/testsWithStdLib/experimental/experimentalIsNotEnabled.kt");
+        }
+
         @TestMetadata("experimentalOnWholeModule.kt")
         public void testExperimentalOnWholeModule() throws Exception {
             runTest("compiler/testData/diagnostics/testsWithStdLib/experimental/experimentalOnWholeModule.kt");

compiler/tests/org/jetbrains/kotlin/codegen/JvmModuleProtoBufTest.kt

@@ -97,9 +97,7 @@ class JvmModuleProtoBufTest : KtUsefulTestCase() {
     fun testExperimental() {
         doTest(
             "/moduleProtoBuf/experimental", extraOptions = listOf(
-                "-Xskip-runtime-version-check",
+                "-Xuse-experimental=kotlin.Experimental",
-                "-language-version",
-                "1.3",
                 "-Xexperimental=org.foo.A",
                 "-Xexperimental=org.foo.B.C",
                 "-Xuse-experimental=org.foo.D"

compiler/tests/org/jetbrains/kotlin/jvm/compiler/ExperimentalIntegrationTest.kt

@@ -15,29 +15,22 @@ class ExperimentalIntegrationTest : AbstractKotlinCompilerIntegrationTest() {
     fun testJvmExperimentalModule() {
         val lib = compileLibrary(
             "lib", additionalOptions = listOf(
-                "-Xskip-runtime-version-check",
+                "-Xuse-experimental=kotlin.Experimental",
-                "-language-version",
-                "1.3",
                 "-Xexperimental=lib.ExperimentalAPI"
             ),
             checkKotlinOutput = { output -> assertTrue(output, output.trimEnd().endsWith("OK")) }
         )
-        compileKotlin("usage.kt", tmpdir, listOf(lib), additionalOptions = listOf("-Xskip-metadata-version-check"))
+        compileKotlin("usage.kt", tmpdir, listOf(lib))
     }
 
     fun testJsExperimentalModule() {
         val lib = compileJsLibrary(
             "lib", additionalOptions = listOf(
-                "-Xskip-runtime-version-check",
+                "-Xuse-experimental=kotlin.Experimental",
-                "-language-version",
-                "1.3",
                 "-Xexperimental=lib.ExperimentalAPI"
             ),
             checkKotlinOutput = { output -> assertTrue(output, output.trimEnd().endsWith("OK")) }
         )
-        compileKotlin(
+        compileKotlin("usage.kt", File(tmpdir, "usage.js"), listOf(lib), K2JSCompiler())
-            "usage.kt", File(tmpdir, "usage.js"), listOf(lib), K2JSCompiler(),
-            additionalOptions = listOf("-Xskip-metadata-version-check")
-        )
     }
 }

idea/tests/org/jetbrains/kotlin/idea/caches/resolve/MultiModuleHighlightingTest.kt

@@ -33,7 +33,6 @@ import org.jetbrains.kotlin.cli.common.arguments.K2JVMCompilerArguments
 import org.jetbrains.kotlin.config.LanguageVersion
 import org.jetbrains.kotlin.idea.caches.project.ModuleSourceInfo
 import org.jetbrains.kotlin.idea.caches.project.SdkInfo
-import org.jetbrains.kotlin.idea.compiler.configuration.KotlinCommonCompilerArgumentsHolder
 import org.jetbrains.kotlin.idea.completion.test.withServiceRegistered
 import org.jetbrains.kotlin.idea.facet.KotlinFacetConfiguration
 import org.jetbrains.kotlin.idea.facet.KotlinFacetType
@@ -218,42 +217,24 @@ open class MultiModuleHighlightingTest : AbstractMultiModuleHighlightingTest() {
         val lib = MockLibraryUtil.compileJvmLibraryToJar(
             testDataPath + "${getTestName(true)}/lib", "lib",
             extraOptions = listOf(
-                "-Xskip-runtime-version-check",
+                "-Xuse-experimental=kotlin.Experimental",
-                "-language-version",
-                "1.3",
                 "-Xexperimental=lib.ExperimentalAPI"
             )
         )
-        withSkipMetadataVersionCheck {
+        module("usage").addLibrary(lib)
-            module("usage").addLibrary(lib)
+        checkHighlightingInAllFiles()
-            checkHighlightingInAllFiles()
-        }
     }
 
     fun testJsExperimentalLibrary() {
         val lib = MockLibraryUtil.compileJsLibraryToJar(
             testDataPath + "${getTestName(true)}/lib", "lib", false,
             extraOptions = listOf(
-                "-Xskip-runtime-version-check",
+                "-Xuse-experimental=kotlin.Experimental",
-                "-language-version",
-                "1.3",
                 "-Xexperimental=lib.ExperimentalAPI"
             )
         )
-        withSkipMetadataVersionCheck {
+        module("usage").addLibrary(lib, kind = JSLibraryKind)
-            module("usage").addLibrary(lib, kind = JSLibraryKind)
+        checkHighlightingInAllFiles()
-            checkHighlightingInAllFiles()
-        }
-    }
-
-    private fun withSkipMetadataVersionCheck(block: () -> Unit) {
-        val holder = KotlinCommonCompilerArgumentsHolder.getInstance(project)
-        try {
-            holder.update { skipMetadataVersionCheck = true }
-            block()
-        } finally {
-            holder.update { skipMetadataVersionCheck = false }
-        }
     }
 
     private fun Module.setupKotlinFacet(configure: KotlinFacetConfiguration.() -> Unit) = apply {

libraries/stdlib/js/build.gradle

@@ -176,8 +176,8 @@ task compileJs(type: JavaExec) {
     doFirst {
         args = [jsOutputFile, rootDir, "$jsSrcDir/wrapper.js"] + inputFiles.collect { it.path }.sort() +
                (compileBuiltinsKotlin2Js.outputs.files.collect { it.path }.sort() +
-                compileKotlin2Js.outputs.files.collect { it.path }.sort() +
+                compileKotlin2Js.outputs.files.collect { it.path }.sort() /* +
-                compileExperimentalKotlin2Js.outputs.files.collect { it.path }.sort()).findAll {
+                compileExperimentalKotlin2Js.outputs.files.collect { it.path }.sort() */).findAll {
                    it.endsWith(".js") && !it.endsWith(".meta.js")
                }
     }
@@ -223,9 +223,9 @@ task compileJs(type: JavaExec) {
 
         sourceMapFile.text = groovy.json.JsonOutput.toJson(sourceMap)
 
-        file(jsOutputMetaFile).text = file(compileKotlin2Js.outputFile.path.replaceAll('\\.js$', '.meta.js')).text +
+        file(jsOutputMetaFile).text = file(compileKotlin2Js.outputFile.path.replaceAll('\\.js$', '.meta.js')).text /* +
                                       file(compileExperimentalKotlin2Js.outputFile.path.replaceAll('\\.js$', '.meta.js')).text
-                                              .replaceFirst(experimentalJsModuleName, 'kotlin')
+                                              .replaceFirst(experimentalJsModuleName, 'kotlin') */
     }
 }
 

libraries/stdlib/src/kotlin/annotations/Experimental.kt

@@ -8,16 +8,21 @@ package kotlin
 import kotlin.annotation.AnnotationRetention.BINARY
 import kotlin.annotation.AnnotationRetention.SOURCE
 import kotlin.annotation.AnnotationTarget.*
+import kotlin.internal.RequireKotlin
+import kotlin.internal.RequireKotlinVersionKind
 import kotlin.reflect.KClass
 
 /**
  * Signals that the annotated annotation class is a marker of an experimental API. Any declaration annotated with that marker is thus
  * considered an experimental declaration and its call sites should accept the experimental aspect of it either by using [UseExperimental],
  * or by being annotated with that marker themselves, effectively causing further propagation of that experimental aspect.
+ *
+ * This class is experimental itself and can only be used with the compiler argument `-Xuse-experimental=kotlin.Experimental`.
  */
 @Target(ANNOTATION_CLASS)
 @Retention(BINARY)
-@SinceKotlin("1.3")
+@SinceKotlin("1.2")
+@RequireKotlin("1.2.50", versionKind = RequireKotlinVersionKind.COMPILER_VERSION)
 @Suppress("ANNOTATION_CLASS_MEMBER")
 annotation class Experimental(val level: Level = Level.ERROR) {
     /**
@@ -35,10 +40,13 @@ annotation class Experimental(val level: Level = Level.ERROR) {
 /**
  * Allows to use experimental API denoted by the given markers in the annotated file, declaration, or expression.
  * If a declaration is annotated with [UseExperimental], its usages are **not** required to opt-in to that experimental API.
+ *
+ * This class is experimental itself and can only be used with the compiler argument `-Xuse-experimental=kotlin.Experimental`.
  */
 @Target(CLASS, PROPERTY, LOCAL_VARIABLE, VALUE_PARAMETER, CONSTRUCTOR, FUNCTION, PROPERTY_GETTER, PROPERTY_SETTER, EXPRESSION, FILE)
 @Retention(SOURCE)
-@SinceKotlin("1.3")
+@SinceKotlin("1.2")
+@RequireKotlin("1.2.50", versionKind = RequireKotlinVersionKind.COMPILER_VERSION)
 annotation class UseExperimental(
     vararg val markerClass: KClass<out Annotation>
 )

libraries/tools/binary-compatibility-validator/src/test/kotlin/org.jetbrains.kotlin.tools.tests/RuntimePublicAPITest.kt

@@ -35,7 +35,7 @@ class RuntimePublicAPITest {
     @Test fun kotlinStdlibRuntimeMerged() {
         snapshotAPIAndCompare(
             "../../stdlib/jvm/build/libs", "kotlin-stdlib",
-            listOf("../stdlib-declarations.json", "../stdlib-experimental-declarations.json"),
+            listOf("../stdlib-declarations.json"/*, "../stdlib-experimental-declarations.json"*/),
             listOf("kotlin.jvm.internal")
         )
     }