JVM: add $delegate method support to kotlinx-metadata

and kotlinp as well -- it is now possible to see the effect of the
previous commit.

libraries/kotlinx-metadata/jvm/src/kotlinx/metadata/jvm/impl/JvmMetadataExtensions.kt

@@ -82,6 +82,10 @@ internal class JvmMetadataExtensions : MetadataExtensions {
             if (propertySignature != null && propertySignature.hasSyntheticMethod()) propertySignature.syntheticMethod else null
         ext.visitSyntheticMethodForAnnotations(syntheticMethod?.run { JvmMethodSignature(c[name], c[desc]) })
 
+        val delegateMethod =
+            if (propertySignature != null && propertySignature.hasDelegateMethod()) propertySignature.delegateMethod else null
+        ext.visitSyntheticMethodForDelegate(delegateMethod?.run { JvmMethodSignature(c[name], c[desc]) })
+
         ext.visitEnd()
     }
 
@@ -180,8 +184,11 @@ internal class JvmMetadataExtensions : MetadataExtensions {
     ): KmPropertyExtensionVisitor? {
         if (type != JvmPropertyExtensionVisitor.TYPE) return null
         return object : JvmPropertyExtensionVisitor() {
-            var jvmFlags: Flags = ProtoBuf.Property.getDefaultInstance().getExtension(JvmProtoBuf.flags)
-            var signature: JvmProtoBuf.JvmPropertySignature.Builder? = null
+            private var jvmFlags: Flags = ProtoBuf.Property.getDefaultInstance().getExtension(JvmProtoBuf.flags)
+            private var signatureOrNull: JvmProtoBuf.JvmPropertySignature.Builder? = null
+
+            private val signature: JvmProtoBuf.JvmPropertySignature.Builder
+                get() = signatureOrNull ?: JvmProtoBuf.JvmPropertySignature.newBuilder().also { signatureOrNull = it }
 
             override fun visit(
                 jvmFlags: Flags,
@@ -190,44 +197,38 @@ internal class JvmMetadataExtensions : MetadataExtensions {
                 setterSignature: JvmMethodSignature?
             ) {
                 this.jvmFlags = jvmFlags
-
-                if (fieldSignature == null && getterSignature == null && setterSignature == null) return
-
-                if (signature == null) {
-                    signature = JvmProtoBuf.JvmPropertySignature.newBuilder()
+                if (fieldSignature != null) {
+                    signature.field = JvmProtoBuf.JvmFieldSignature.newBuilder().also { field ->
+                        field.name = c[fieldSignature.name]
+                        field.desc = c[fieldSignature.desc]
+                    }.build()
                 }
-                signature!!.apply {
-                    if (fieldSignature != null) {
-                        field = JvmProtoBuf.JvmFieldSignature.newBuilder().also { field ->
-                            field.name = c[fieldSignature.name]
-                            field.desc = c[fieldSignature.desc]
-                        }.build()
-                    }
-                    if (getterSignature != null) {
-                        getter = getterSignature.toJvmMethodSignature(c)
-                    }
-                    if (setterSignature != null) {
-                        setter = setterSignature.toJvmMethodSignature(c)
-                    }
+                if (getterSignature != null) {
+                    signature.getter = getterSignature.toJvmMethodSignature(c)
+                }
+                if (setterSignature != null) {
+                    signature.setter = setterSignature.toJvmMethodSignature(c)
                 }
             }
 
             override fun visitSyntheticMethodForAnnotations(signature: JvmMethodSignature?) {
                 if (signature == null) return
 
-                if (this.signature == null) {
-                    this.signature = JvmProtoBuf.JvmPropertySignature.newBuilder()
-                }
+                this.signature.syntheticMethod = signature.toJvmMethodSignature(c)
+            }
 
-                this.signature!!.syntheticMethod = signature.toJvmMethodSignature(c)
+            override fun visitSyntheticMethodForDelegate(signature: JvmMethodSignature?) {
+                if (signature == null) return
+
+                this.signature.delegateMethod = signature.toJvmMethodSignature(c)
             }
 
             override fun visitEnd() {
                 if (jvmFlags != ProtoBuf.Property.getDefaultInstance().getExtension(JvmProtoBuf.flags)) {
                     proto.setExtension(JvmProtoBuf.flags, jvmFlags)
                 }
-                if (signature != null) {
-                    proto.setExtension(JvmProtoBuf.propertySignature, signature!!.build())
+                if (signatureOrNull != null) {
+                    proto.setExtension(JvmProtoBuf.propertySignature, signature.build())
                 }
             }
         }

libraries/kotlinx-metadata/jvm/src/kotlinx/metadata/jvm/impl/jvmExtensionNodes.kt

@@ -105,6 +105,7 @@ internal class JvmPropertyExtension : JvmPropertyExtensionVisitor(), KmPropertyE
     var getterSignature: JvmMethodSignature? = null
     var setterSignature: JvmMethodSignature? = null
     var syntheticMethodForAnnotations: JvmMethodSignature? = null
+    var syntheticMethodForDelegate: JvmMethodSignature? = null
 
     override fun visit(
         jvmFlags: Flags,
@@ -122,10 +123,15 @@ internal class JvmPropertyExtension : JvmPropertyExtensionVisitor(), KmPropertyE
         this.syntheticMethodForAnnotations = signature
     }
 
+    override fun visitSyntheticMethodForDelegate(signature: JvmMethodSignature?) {
+        this.syntheticMethodForDelegate = signature
+    }
+
     override fun accept(visitor: KmPropertyExtensionVisitor) {
         require(visitor is JvmPropertyExtensionVisitor)
         visitor.visit(jvmFlags, fieldSignature, getterSignature, setterSignature)
         visitor.visitSyntheticMethodForAnnotations(syntheticMethodForAnnotations)
+        visitor.visitSyntheticMethodForDelegate(syntheticMethodForDelegate)
         visitor.visitEnd()
     }
 }

libraries/kotlinx-metadata/jvm/src/kotlinx/metadata/jvm/jvmExtensionVisitors.kt

@@ -212,6 +212,19 @@ open class JvmPropertyExtensionVisitor @JvmOverloads constructor(
         delegate?.visitSyntheticMethodForAnnotations(signature)
     }
 
+    /**
+     * Visits the JVM signature of a synthetic method which is generated when a delegated property's delegate object is
+     * optimized out, e.g. because it is constant; in that case, a copy of that object can be obtained on demand by calling
+     * this method. It takes up to two arguments - the property's receivers.
+     *
+     * Example: `JvmMethodSignature("getX$delegate", "(LMyClass;)LMyDelegate;")`
+     *
+     * @param signature the signature of the synthetic method
+     */
+    open fun visitSyntheticMethodForDelegate(signature: JvmMethodSignature?) {
+        delegate?.visitSyntheticMethodForDelegate(signature)
+    }
+
     /**
      * Visits the end of JVM extensions for the property.
      */

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

@@ -103,6 +103,7 @@ private fun visitProperty(
         var jvmGetterSignature: JvmMemberSignature? = null
         var jvmSetterSignature: JvmMemberSignature? = null
         var jvmSyntheticMethodForAnnotationsSignature: JvmMemberSignature? = null
+        var jvmSyntheticMethodForDelegateSignature: JvmMemberSignature? = null
         var isMovedFromInterfaceCompanion: Boolean = false
 
         override fun visitReceiverParameterType(flags: Flags): KmTypeVisitor? =
@@ -138,6 +139,10 @@ private fun visitProperty(
                 override fun visitSyntheticMethodForAnnotations(signature: JvmMethodSignature?) {
                     jvmSyntheticMethodForAnnotationsSignature = signature
                 }
+
+                override fun visitSyntheticMethodForDelegate(signature: JvmMethodSignature?) {
+                    jvmSyntheticMethodForDelegateSignature = signature
+                }
             }
         }
 
@@ -158,6 +163,9 @@ private fun visitProperty(
             if (jvmSyntheticMethodForAnnotationsSignature != null) {
                 sb.appendLine("  // synthetic method for annotations: $jvmSyntheticMethodForAnnotationsSignature")
             }
+            if (jvmSyntheticMethodForDelegateSignature != null) {
+                sb.appendLine("  // synthetic method for delegate: $jvmSyntheticMethodForDelegateSignature")
+            }
             if (isMovedFromInterfaceCompanion) {
                 sb.appendLine("  // is moved from interface companion")
             }