Support fun interfaces in kotlinx-metadata

 #KT-37421 Fixed

compiler/fir/analysis-tests/testData/loadCompiledKotlin/class/FunInterface.txt

+public abstract interface F : R|kotlin/Any| {
+    public abstract fun R|kotlin/String|.f(x: R|kotlin/Int|): R|kotlin/Unit|
+
+}

compiler/fir/analysis-tests/tests/org/jetbrains/kotlin/fir/FirLoadCompiledKotlinGenerated.java

@@ -604,6 +604,11 @@ public class FirLoadCompiledKotlinGenerated extends AbstractFirLoadCompiledKotli
             runTest("compiler/testData/loadJava/compiledKotlin/class/EnumWithPrimitiveConstructorParameter.kt");
         }
 
+        @TestMetadata("FunInterface.kt")
+        public void testFunInterface() throws Exception {
+            runTest("compiler/testData/loadJava/compiledKotlin/class/FunInterface.kt");
+        }
+
         @TestMetadata("InheritClassSimple.kt")
         public void testInheritClassSimple() throws Exception {
             runTest("compiler/testData/loadJava/compiledKotlin/class/InheritClassSimple.kt");

compiler/testData/loadJava/compiledKotlin/class/FunInterface.kt

+package test
+
+fun interface F {
+    fun String.f(x: Int)
+}

compiler/testData/loadJava/compiledKotlin/class/FunInterface.txt

+package test
+
+public fun interface F {
+    public abstract fun kotlin.String.f(/*0*/ x: kotlin.Int): kotlin.Unit
+}

compiler/tests/org/jetbrains/kotlin/jvm/compiler/LoadJavaTestGenerated.java

@@ -2295,6 +2295,11 @@ public class LoadJavaTestGenerated extends AbstractLoadJavaTest {
                 runTest("compiler/testData/loadJava/compiledKotlin/class/EnumWithPrimitiveConstructorParameter.kt");
             }
 
+            @TestMetadata("FunInterface.kt")
+            public void testFunInterface() throws Exception {
+                runTest("compiler/testData/loadJava/compiledKotlin/class/FunInterface.kt");
+            }
+
             @TestMetadata("InheritClassSimple.kt")
             public void testInheritClassSimple() throws Exception {
                 runTest("compiler/testData/loadJava/compiledKotlin/class/InheritClassSimple.kt");

compiler/tests/org/jetbrains/kotlin/jvm/compiler/LoadKotlinWithTypeTableTestGenerated.java

@@ -604,6 +604,11 @@ public class LoadKotlinWithTypeTableTestGenerated extends AbstractLoadKotlinWith
             runTest("compiler/testData/loadJava/compiledKotlin/class/EnumWithPrimitiveConstructorParameter.kt");
         }
 
+        @TestMetadata("FunInterface.kt")
+        public void testFunInterface() throws Exception {
+            runTest("compiler/testData/loadJava/compiledKotlin/class/FunInterface.kt");
+        }
+
         @TestMetadata("InheritClassSimple.kt")
         public void testInheritClassSimple() throws Exception {
             runTest("compiler/testData/loadJava/compiledKotlin/class/InheritClassSimple.kt");

compiler/tests/org/jetbrains/kotlin/jvm/compiler/ir/IrLoadJavaTestGenerated.java

@@ -2296,6 +2296,11 @@ public class IrLoadJavaTestGenerated extends AbstractIrLoadJavaTest {
                 runTest("compiler/testData/loadJava/compiledKotlin/class/EnumWithPrimitiveConstructorParameter.kt");
             }
 
+            @TestMetadata("FunInterface.kt")
+            public void testFunInterface() throws Exception {
+                runTest("compiler/testData/loadJava/compiledKotlin/class/FunInterface.kt");
+            }
+
             @TestMetadata("InheritClassSimple.kt")
             public void testInheritClassSimple() throws Exception {
                 runTest("compiler/testData/loadJava/compiledKotlin/class/InheritClassSimple.kt");

compiler/tests/org/jetbrains/kotlin/jvm/compiler/javac/LoadJavaUsingJavacTestGenerated.java

@@ -2295,6 +2295,11 @@ public class LoadJavaUsingJavacTestGenerated extends AbstractLoadJavaUsingJavacT
                 runTest("compiler/testData/loadJava/compiledKotlin/class/EnumWithPrimitiveConstructorParameter.kt");
             }
 
+            @TestMetadata("FunInterface.kt")
+            public void testFunInterface() throws Exception {
+                runTest("compiler/testData/loadJava/compiledKotlin/class/FunInterface.kt");
+            }
+
             @TestMetadata("InheritClassSimple.kt")
             public void testInheritClassSimple() throws Exception {
                 runTest("compiler/testData/loadJava/compiledKotlin/class/InheritClassSimple.kt");

core/descriptors.runtime/tests/org/jetbrains/kotlin/jvm/runtime/JvmRuntimeDescriptorLoaderTestGenerated.java

@@ -606,6 +606,11 @@ public class JvmRuntimeDescriptorLoaderTestGenerated extends AbstractJvmRuntimeD
                 runTest("compiler/testData/loadJava/compiledKotlin/class/EnumWithPrimitiveConstructorParameter.kt");
             }
 
+            @TestMetadata("FunInterface.kt")
+            public void testFunInterface() throws Exception {
+                runTest("compiler/testData/loadJava/compiledKotlin/class/FunInterface.kt");
+            }
+
             @TestMetadata("InheritClassSimple.kt")
             public void testInheritClassSimple() throws Exception {
                 runTest("compiler/testData/loadJava/compiledKotlin/class/InheritClassSimple.kt");

libraries/kotlinx-metadata/jvm/ChangeLog.md

 # kotlinx-metadata-jvm
 
+## 0.1.1
+
+- [`KT-37421`](https://youtrack.jetbrains.com/issue/KT-37421) Add Flag.Class.IS_FUN for functional interfaces
+- Add `KmModule.optionalAnnotationClasses` for the new scheme of compilation of OptionalExpectation annotations in multiplatform projects ([KT-38652](https://youtrack.jetbrains.com/issue/KT-38652))
+
 ## 0.1.0
 
 - [`KT-26602`](https://youtrack.jetbrains.com/issue/KT-26602) Provide a value-based API

libraries/kotlinx-metadata/src/kotlinx/metadata/Flag.kt

@@ -207,6 +207,12 @@ class Flag(private val offset: Int, private val bitWidth: Int, private val value
          */
         @JvmField
         val IS_INLINE = Flag(F.IS_INLINE_CLASS)
+
+        /**
+         * Signifies that the corresponding class is a functional interface, i.e. marked with the keyword `fun`.
+         */
+        @JvmField
+        val IS_FUN = Flag(F.IS_FUN_INTERFACE)
     }
 
     /**

libraries/tools/kotlinp/src/org/jetbrains/kotlin/kotlinp/printers.kt

@@ -946,6 +946,7 @@ private val CLASS_FLAGS_MAP = COMMON_FLAGS_MAP + mapOf(
     Flag.Class.IS_EXTERNAL to "external",
     Flag.Class.IS_EXPECT to "expect",
     Flag.Class.IS_INLINE to "inline",
+    Flag.Class.IS_FUN to "fun",
 
     Flag.Class.IS_CLASS to "class",
     Flag.Class.IS_INTERFACE to "interface",

libraries/tools/kotlinp/test/org/jetbrains/kotlin/kotlinp/test/GenerateKotlinpTests.kt

@@ -7,7 +7,7 @@ package org.jetbrains.kotlin.kotlinp.test
 
 import org.jetbrains.kotlin.generators.tests.generator.testGroup
 
-fun main(args: Array<String>) {
+fun main() {
     System.setProperty("java.awt.headless", "true")
 
     testGroup("libraries/tools/kotlinp/test", "libraries/tools/kotlinp/testData") {

libraries/tools/kotlinp/test/org/jetbrains/kotlin/kotlinp/test/KotlinpTestGenerated.java

@@ -38,6 +38,11 @@ public class KotlinpTestGenerated extends AbstractKotlinpTest {
         runTest("libraries/tools/kotlinp/testData/Contracts.kt");
     }
 
+    @TestMetadata("FunInterface.kt")
+    public void testFunInterface() throws Exception {
+        runTest("libraries/tools/kotlinp/testData/FunInterface.kt");
+    }
+
     @TestMetadata("Lambda.kt")
     public void testLambda() throws Exception {
         runTest("libraries/tools/kotlinp/testData/Lambda.kt");

libraries/tools/kotlinp/testData/FunInterface.kt

+fun interface F {
+    fun String.f(x: Int)
+}

libraries/tools/kotlinp/testData/FunInterface.txt

+// F.class
+// ------------------------------------------
+public abstract fun interface F : kotlin/Any {
+
+  // signature: f(Ljava/lang/String;I)V
+  public abstract fun kotlin/String.f(x: kotlin/Int): kotlin/Unit
+
+  // module name: test-module
+}
+// META-INF/test-module.kotlin_module
+// ------------------------------------------
+module {
+}