Add underlying property name & type for inline class to kotlinx-metadata

#KT-45635 Fixed

core/metadata/src/org/jetbrains/kotlin/metadata/deserialization/protoTypeTableUtil.kt

@@ -23,6 +23,12 @@ import org.jetbrains.kotlin.metadata.ProtoBuf
 fun ProtoBuf.Class.supertypes(typeTable: TypeTable): List<ProtoBuf.Type> =
     supertypeList.takeIf(Collection<*>::isNotEmpty) ?: supertypeIdList.map { typeTable[it] }
 
+fun ProtoBuf.Class.inlineClassUnderlyingType(typeTable: TypeTable): ProtoBuf.Type? = when {
+    hasInlineClassUnderlyingType() -> inlineClassUnderlyingType
+    hasInlineClassUnderlyingTypeId() -> typeTable[inlineClassUnderlyingTypeId]
+    else -> null
+}
+
 fun ProtoBuf.Type.Argument.type(typeTable: TypeTable): ProtoBuf.Type? = when {
     hasType() -> type
     hasTypeId() -> typeTable[typeId]

libraries/kotlinx-metadata/jvm/ChangeLog.md

@@ -17,6 +17,7 @@
 - Breaking change: deprecate `KotlinClassHeader.bytecodeVersion` and `KotlinClassHeader`'s constructor that takes a bytecode version array.
   Related to ['KT-41758`](https://youtrack.jetbrains.com/issue/KT-41758).
 - [`KT-45594`](https://youtrack.jetbrains.com/issue/KT-45594) KClass annotation argument containing array of classes is not read/written correctly
+- [`KT-45635`](https://youtrack.jetbrains.com/issue/KT-45635) Add underlying property name & type for inline classes
 
 ## 0.2.0
 

libraries/kotlinx-metadata/src/kotlinx/metadata/impl/readers.kt

@@ -93,6 +93,13 @@ fun ProtoBuf.Class.accept(
         v.visitSealedSubclass(c.className(sealedSubclassFqName))
     }
 
+    if (hasInlineClassUnderlyingPropertyName()) {
+        v.visitInlineClassUnderlyingPropertyName(c[inlineClassUnderlyingPropertyName])
+    }
+    loadInlineClassUnderlyingType(c)?.let { underlyingType ->
+        v.visitInlineClassUnderlyingType(underlyingType.flags)?.let { underlyingType.accept(it, c) }
+    }
+
     for (versionRequirement in versionRequirementList) {
         v.visitVersionRequirement()?.let { acceptVersionRequirementVisitor(versionRequirement, it, c) }
     }
@@ -104,6 +111,18 @@ fun ProtoBuf.Class.accept(
     v.visitEnd()
 }
 
+private fun ProtoBuf.Class.loadInlineClassUnderlyingType(c: ReadContext): ProtoBuf.Type? {
+    val type = inlineClassUnderlyingType(c.types)
+    if (type != null) return type
+
+    if (!hasInlineClassUnderlyingPropertyName()) return null
+
+    // Kotlin compiler doesn't write underlying type to metadata in case it can be loaded from the underlying property.
+    return propertyList
+        .singleOrNull { it.receiverType(c.types) == null && c[it.name] == c[inlineClassUnderlyingPropertyName] }
+        ?.returnType(c.types)
+}
+
 fun ProtoBuf.Package.accept(
     v: KmPackageVisitor,
     strings: NameResolver,

libraries/kotlinx-metadata/src/kotlinx/metadata/impl/writers.kt

@@ -457,6 +457,13 @@ open class ClassWriter(stringTable: StringTable, contextExtensions: List<WriteCo
         t.addSealedSubclassFqName(c.getClassName(name))
     }
 
+    override fun visitInlineClassUnderlyingPropertyName(name: String) {
+        t.inlineClassUnderlyingPropertyName = c[name]
+    }
+
+    override fun visitInlineClassUnderlyingType(flags: Flags): KmTypeVisitor? =
+        writeType(c, flags) { t.inlineClassUnderlyingType = it.build() }
+
     override fun visitVersionRequirement(): KmVersionRequirementVisitor? =
         writeVersionRequirement(c) { t.addVersionRequirement(it) }
 

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

@@ -93,6 +93,16 @@ class KmClass : KmClassVisitor(), KmDeclarationContainer {
      */
     val sealedSubclasses: MutableList<ClassName> = ArrayList(0)
 
+    /**
+     * Name of the underlying property, if this class is `inline`.
+     */
+    var inlineClassUnderlyingPropertyName: String? = null
+
+    /**
+     * Type of the underlying property, if this class is `inline`.
+     */
+    var inlineClassUnderlyingType: KmType? = null
+
     /**
      * Version requirements on this class.
      */
@@ -140,6 +150,13 @@ class KmClass : KmClassVisitor(), KmDeclarationContainer {
         sealedSubclasses.add(name)
     }
 
+    override fun visitInlineClassUnderlyingPropertyName(name: String) {
+        inlineClassUnderlyingPropertyName = name
+    }
+
+    override fun visitInlineClassUnderlyingType(flags: Flags): KmTypeVisitor =
+        KmType(flags).also { inlineClassUnderlyingType = it }
+
     override fun visitVersionRequirement(): KmVersionRequirementVisitor =
         KmVersionRequirement().addTo(versionRequirements)
 
@@ -163,6 +180,8 @@ class KmClass : KmClassVisitor(), KmDeclarationContainer {
         nestedClasses.forEach(visitor::visitNestedClass)
         enumEntries.forEach(visitor::visitEnumEntry)
         sealedSubclasses.forEach(visitor::visitSealedSubclass)
+        inlineClassUnderlyingPropertyName?.let(visitor::visitInlineClassUnderlyingPropertyName)
+        inlineClassUnderlyingType?.let { visitor.visitInlineClassUnderlyingType(it.flags)?.let(it::accept) }
         versionRequirements.forEach { visitor.visitVersionRequirement()?.let(it::accept) }
         extensions.forEach { visitor.visitExtensions(it.type)?.let(it::accept) }
         visitor.visitEnd()

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

@@ -132,6 +132,23 @@ abstract class KmClassVisitor @JvmOverloads constructor(delegate: KmClassVisitor
         delegate?.visitSealedSubclass(name)
     }
 
+    /**
+     * Visits the name of the underlying property, if this class is `inline`.
+     *
+     * @param name the name of the underlying property.
+     */
+    open fun visitInlineClassUnderlyingPropertyName(name: String) {
+        delegate?.visitInlineClassUnderlyingPropertyName(name)
+    }
+
+    /**
+     * Visits the type of the underlying property, if this class is `inline`.
+     *
+     * @param flags type flags, consisting of [Flag.Type] flags
+     */
+    open fun visitInlineClassUnderlyingType(flags: Flags): KmTypeVisitor? =
+        delegate?.visitInlineClassUnderlyingType(flags)
+
     /**
      * Visits the version requirement on this class.
      */

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

@@ -767,6 +767,17 @@ class ClassPrinter(private val settings: KotlinpSettings) : KmClassVisitor(), Ab
         sb.appendLine("  // sealed subclass: $name")
     }
 
+    override fun visitInlineClassUnderlyingPropertyName(name: String) {
+        sb.appendLine()
+        sb.appendLine("  // underlying property: $name")
+    }
+
+    override fun visitInlineClassUnderlyingType(flags: Flags): KmTypeVisitor? =
+        printType(flags) {
+            sb.appendLine()
+            sb.appendLine("  // underlying type: $it")
+        }
+
     override fun visitVersionRequirement(): KmVersionRequirementVisitor? =
         printVersionRequirement { versionRequirements.add(it) }
 

libraries/tools/kotlinp/testData/ValueClass.txt

@@ -21,6 +21,10 @@ public final value class Z : kotlin/Any {
   public final val s: kotlin/String
     public final get
 
+  // underlying property: s
+
+  // underlying type: kotlin/String
+
   // module name: test-module
 }
 // META-INF/test-module.kotlin_module