Value classes: Add JvmInlineValueClasses language feature

compiler/frontend/src/org/jetbrains/kotlin/resolve/ModifiersChecker.kt

@@ -119,8 +119,7 @@ object ModifierCheckerCore {
         EXPECT_KEYWORD to listOf(LanguageFeature.MultiPlatformProjects),
         ACTUAL_KEYWORD to listOf(LanguageFeature.MultiPlatformProjects),
         LATEINIT_KEYWORD to listOf(LanguageFeature.LateinitTopLevelProperties, LanguageFeature.LateinitLocalVariables),
-        FUN_KEYWORD to listOf(LanguageFeature.FunctionalInterfaceConversion),
+        FUN_KEYWORD to listOf(LanguageFeature.FunctionalInterfaceConversion)
-        VALUE_KEYWORD to listOf(LanguageFeature.InlineClasses)
     )
 
     private val featureDependenciesTargets = mapOf(
@@ -128,6 +127,7 @@ object ModifierCheckerCore {
         LanguageFeature.LateinitLocalVariables to setOf(LOCAL_VARIABLE),
         LanguageFeature.LateinitTopLevelProperties to setOf(TOP_LEVEL_PROPERTY),
         LanguageFeature.InlineClasses to setOf(CLASS_ONLY),
+        LanguageFeature.JvmInlineValueClasses to setOf(CLASS_ONLY),
         LanguageFeature.FunctionalInterfaceConversion to setOf(INTERFACE)
     )
 

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

@@ -7,6 +7,7 @@ package org.jetbrains.kotlin.resolve.checkers
 
 import org.jetbrains.kotlin.builtins.KotlinBuiltIns
 import org.jetbrains.kotlin.builtins.StandardNames
+import org.jetbrains.kotlin.config.LanguageFeature
 import org.jetbrains.kotlin.descriptors.*
 import org.jetbrains.kotlin.diagnostics.Errors
 import org.jetbrains.kotlin.lexer.KtTokens
@@ -32,11 +33,28 @@ object InlineClassDeclarationChecker : DeclarationChecker {
         if (descriptor !is ClassDescriptor || !descriptor.isInline && !descriptor.isValue) return
         if (descriptor.kind != ClassKind.CLASS) return
 
-        val inlineOrValueKeyword = declaration.modifierList?.getModifier(KtTokens.INLINE_KEYWORD)
+        val trace = context.trace
-            ?: declaration.modifierList?.getModifier(KtTokens.VALUE_KEYWORD)
+
+        val valueKeyword = declaration.modifierList?.getModifier(KtTokens.VALUE_KEYWORD)
+
+        // The check cannot be done in ModifierCheckerCore, since `value` keyword is enabled by one of two features, not by both of
+        // them simultaneously
+        if (valueKeyword != null) {
+            if (!context.languageVersionSettings.supportsFeature(LanguageFeature.JvmInlineValueClasses) &&
+                !context.languageVersionSettings.supportsFeature(LanguageFeature.InlineClasses)
+            ) {
+                trace.report(
+                    Errors.UNSUPPORTED_FEATURE.on(
+                        valueKeyword, LanguageFeature.JvmInlineValueClasses to context.languageVersionSettings
+                    )
+                )
+                return
+            }
+        }
+
+        val inlineOrValueKeyword = declaration.modifierList?.getModifier(KtTokens.INLINE_KEYWORD) ?: valueKeyword
         require(inlineOrValueKeyword != null) { "Declaration of inline class must have 'inline' keyword" }
 
-        val trace = context.trace
         if (descriptor.isInner || DescriptorUtils.isLocal(descriptor)) {
             trace.report(Errors.INLINE_CLASS_NOT_TOP_LEVEL.on(inlineOrValueKeyword))
             return

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

@@ -21,7 +21,8 @@ class ResultClassInReturnTypeChecker : DeclarationChecker {
         val languageVersionSettings = context.languageVersionSettings
         if (
             languageVersionSettings.getFlag(AnalysisFlags.allowResultReturnType) ||
-            languageVersionSettings.getFeatureSupport(LanguageFeature.InlineClasses) == LanguageFeature.State.ENABLED &&
+            (languageVersionSettings.getFeatureSupport(LanguageFeature.InlineClasses) == LanguageFeature.State.ENABLED ||
+                    languageVersionSettings.supportsFeature(LanguageFeature.JvmInlineValueClasses)) &&
             languageVersionSettings.supportsFeature(LanguageFeature.AllowResultInReturnType)
         ) return
 

compiler/testData/diagnostics/tests/valueClasses/basicValueClassDeclarationDisabled.kt

@@ -13,4 +13,4 @@ annotation class JvmInline
 <!VALUE_CLASS_WITHOUT_JVM_INLINE_ANNOTATION, WRONG_MODIFIER_TARGET!>value<!> enum class InlineEnum
 
 @JvmInline
-<!UNSUPPORTED_FEATURE!>value<!> class NotVal(<!INLINE_CLASS_CONSTRUCTOR_NOT_FINAL_READ_ONLY_PARAMETER!>x: Int<!>)
+<!UNSUPPORTED_FEATURE!>value<!> class NotVal(x: Int)

compiler/testData/diagnostics/testsWithJvmBackend/noWarningInLV1_5.kt

@@ -0,0 +1,9 @@
+// !LANGUAGE: +JvmInlineValueClasses
+// WITH_RUNTIME
+
+package kotlin.jvm
+
+annotation class JvmInline
+
+@JvmInline
+value class VC(val a: Any)

compiler/testData/diagnostics/testsWithJvmBackend/noWarningInLV1_5.txt

@@ -0,0 +1,23 @@
+package
+
+package kotlin {
+
+    package kotlin.jvm {
+
+        public final annotation class JvmInline : kotlin.Annotation {
+            public constructor JvmInline()
+            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
+        }
+
+        @kotlin.jvm.JvmInline public final value class VC {
+            public constructor VC(/*0*/ a: kotlin.Any)
+            public final val a: kotlin.Any
+            public open override /*1*/ /*synthesized*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+            public open override /*1*/ /*synthesized*/ fun hashCode(): kotlin.Int
+            public open override /*1*/ /*synthesized*/ fun toString(): kotlin.String
+        }
+    }
+}
+

compiler/tests-common-new/tests-gen/org/jetbrains/kotlin/test/runners/DiagnosticsTestWithJvmIrBackendGenerated.java

@@ -43,6 +43,12 @@ public class DiagnosticsTestWithJvmIrBackendGenerated extends AbstractDiagnostic
         runTest("compiler/testData/diagnostics/testsWithJvmBackend/multipleBigArityFunsImplemented_ir.kt");
     }
 
+    @Test
+    @TestMetadata("noWarningInLV1_5.kt")
+    public void testNoWarningInLV1_5() throws Exception {
+        runTest("compiler/testData/diagnostics/testsWithJvmBackend/noWarningInLV1_5.kt");
+    }
+
     @Test
     @TestMetadata("suspendInlineCycle_ir.kt")
     public void testSuspendInlineCycle_ir() throws Exception {

compiler/tests-common-new/tests-gen/org/jetbrains/kotlin/test/runners/DiagnosticsTestWithOldJvmBackendGenerated.java

@@ -43,6 +43,12 @@ public class DiagnosticsTestWithOldJvmBackendGenerated extends AbstractDiagnosti
         runTest("compiler/testData/diagnostics/testsWithJvmBackend/multipleBigArityFunsImplemented.kt");
     }
 
+    @Test
+    @TestMetadata("noWarningInLV1_5.kt")
+    public void testNoWarningInLV1_5() throws Exception {
+        runTest("compiler/testData/diagnostics/testsWithJvmBackend/noWarningInLV1_5.kt");
+    }
+
     @Test
     @TestMetadata("suspendInlineCycle.kt")
     public void testSuspendInlineCycle() throws Exception {

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

@@ -194,6 +194,7 @@ enum class LanguageFeature(
     // Next features can be enabled regardless of new inference
 
     InlineClasses(sinceVersion = KOTLIN_1_3, defaultState = State.ENABLED_WITH_WARNING, kind = UNSTABLE_FEATURE),
+    JvmInlineValueClasses(sinceVersion = KOTLIN_1_5, defaultState = State.ENABLED, kind = OTHER),
     ;
 
     val presentableName: String