[FIR generator] Factor out AbstractElement to common module

This is a step towards commonizing the code generator between
FIR and IR: KT-61970

compiler/fir/tree/tree-generator/src/org/jetbrains/kotlin/fir/tree/generator/model/Builder.kt

@@ -5,9 +5,9 @@
 
 package org.jetbrains.kotlin.fir.tree.generator.model
 
-import org.jetbrains.kotlin.fir.tree.generator.printer.generics
 import org.jetbrains.kotlin.generators.tree.FieldContainer
 import org.jetbrains.kotlin.generators.tree.Importable
+import org.jetbrains.kotlin.generators.tree.generics
 
 private const val DEFAULT_BUILDER_PACKAGE = "org.jetbrains.kotlin.fir.tree.builder"
 

compiler/fir/tree/tree-generator/src/org/jetbrains/kotlin/fir/tree/generator/model/Element.kt

@@ -6,21 +6,14 @@
 package org.jetbrains.kotlin.fir.tree.generator.model
 
 import org.jetbrains.kotlin.fir.tree.generator.printer.BASE_PACKAGE
-import org.jetbrains.kotlin.fir.tree.generator.printer.generics
-import org.jetbrains.kotlin.generators.tree.typeWithArguments
 import org.jetbrains.kotlin.fir.tree.generator.util.set
-import org.jetbrains.kotlin.generators.tree.FieldContainer
 import org.jetbrains.kotlin.generators.tree.ImplementationKind
 import org.jetbrains.kotlin.generators.tree.Importable
 import org.jetbrains.kotlin.generators.tree.TypeArgument
-import org.jetbrains.kotlin.generators.tree.ImplementationKindOwner
+import org.jetbrains.kotlin.generators.tree.typeWithArguments
+import org.jetbrains.kotlin.generators.tree.AbstractElement as CommonAbstractElement
 
-interface AbstractElement : FieldContainer, ImplementationKindOwner {
-    val name: String
-    val fields: Set<Field>
-    val parents: List<AbstractElement>
-    val typeArguments: List<TypeArgument>
-    val parentsArguments: Map<AbstractElement, Map<Importable, Importable>>
+interface AbstractElement : CommonAbstractElement<AbstractElement, Field> {
     val baseTransformerType: AbstractElement?
     val transformerType: AbstractElement
     val doesNotNeedImplementation: Boolean
@@ -29,15 +22,7 @@ interface AbstractElement : FieldContainer, ImplementationKindOwner {
     val allFirFields: List<Field>
     val defaultImplementation: Implementation?
     val customImplementations: List<Implementation>
-    val overridenFields: Map<Field, Map<Importable, Boolean>>
     val useNullableForReplace: Set<Field>
-
-    val isSealed: Boolean
-        get() = false
-
-    override val allParents: List<ImplementationKindOwner> get() = parents
-
-    override fun getTypeWithArguments(notNull: Boolean): String = type + generics
 }
 
 class Element(override val name: String, kind: Kind) : AbstractElement {

compiler/fir/tree/tree-generator/src/org/jetbrains/kotlin/fir/tree/generator/printer/utils.kt

@@ -169,11 +169,6 @@ val Element.safeDecapitalizedName: String get() = if (name == "Class") "klass" e
 val ImplementationWithArg.generics: String
     get() = argument?.let { "<${it.type}>" } ?: ""
 
-val AbstractElement.generics: String
-    get() = typeArguments.takeIf { it.isNotEmpty() }
-        ?.let { it.joinToString(", ", "<", ">") { it.name } }
-        ?: ""
-
 val Field.generics: String
     get() = arguments.takeIf { it.isNotEmpty() }
         ?.let { it.joinToString(", ", "<", ">") { it.typeWithArguments } }

generators/tree-generator-common/src/org/jetbrains/kotlin/generators/tree/AbstractElement.kt

@@ -0,0 +1,37 @@
+/*
+ * Copyright 2010-2023 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+package org.jetbrains.kotlin.generators.tree
+
+/**
+ * A common interface representing a FIR or IR tree element.
+ */
+interface AbstractElement<Element : AbstractElement<Element, Field>, Field : AbstractField> : FieldContainer, ImplementationKindOwner {
+
+    val name: String
+
+    val fields: Set<Field>
+
+    val parents: List<Element>
+
+    val typeArguments: List<TypeArgument>
+
+    val parentsArguments: Map<Element, Map<Importable, Importable>>
+
+    val overridenFields: Map<Field, Map<Importable, Boolean>>
+
+    val isSealed: Boolean
+        get() = false
+
+    override val allParents: List<ImplementationKindOwner>
+        get() = parents
+
+    override fun getTypeWithArguments(notNull: Boolean): String = type + generics
+}
+
+val AbstractElement<*, *>.generics: String
+    get() = typeArguments.takeIf { it.isNotEmpty() }
+        ?.let { it.joinToString(", ", "<", ">") { it.name } }
+        ?: ""