[IR] Move IrValueDeclaration.isAssignable to extension property

to remove custom logic from generated classes, in particular
to simplify source generator itself.

compiler/ir/backend.common/src/org/jetbrains/kotlin/backend/common/ir/ValueRemapper.kt

@@ -1,5 +1,5 @@
 /*
- * Copyright 2010-2021 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Copyright 2010-2024 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.
  */
 
@@ -11,6 +11,7 @@ import org.jetbrains.kotlin.ir.expressions.IrSetValue
 import org.jetbrains.kotlin.ir.expressions.impl.IrGetValueImpl
 import org.jetbrains.kotlin.ir.expressions.impl.IrSetValueImpl
 import org.jetbrains.kotlin.ir.symbols.IrValueSymbol
+import org.jetbrains.kotlin.ir.util.isAssignable
 import org.jetbrains.kotlin.ir.visitors.IrElementTransformerVoid
 
 abstract class AbstractValueRemapper : IrElementTransformerVoid() {

compiler/ir/ir.tree/gen/org/jetbrains/kotlin/ir/declarations/IrValueDeclaration.kt

@@ -23,6 +23,4 @@ interface IrValueDeclaration : IrDeclarationWithName, IrSymbolOwner {
     override val symbol: IrValueSymbol
 
     var type: IrType
-
-    val isAssignable: Boolean
 }

compiler/ir/ir.tree/gen/org/jetbrains/kotlin/ir/declarations/IrValueParameter.kt

@@ -24,6 +24,8 @@ abstract class IrValueParameter : IrDeclarationBase(), IrValueDeclaration {
     @ObsoleteDescriptorBasedAPI
     abstract override val descriptor: ParameterDescriptor
 
+    abstract val isAssignable: Boolean
+
     abstract override val symbol: IrValueParameterSymbol
 
     abstract var index: Int

compiler/ir/ir.tree/gen/org/jetbrains/kotlin/ir/declarations/IrVariable.kt

@@ -11,7 +11,6 @@ package org.jetbrains.kotlin.ir.declarations
 import org.jetbrains.kotlin.descriptors.VariableDescriptor
 import org.jetbrains.kotlin.ir.ObsoleteDescriptorBasedAPI
 import org.jetbrains.kotlin.ir.expressions.IrExpression
-import org.jetbrains.kotlin.ir.expressions.IrSetValue
 import org.jetbrains.kotlin.ir.symbols.IrVariableSymbol
 import org.jetbrains.kotlin.ir.visitors.IrElementTransformer
 import org.jetbrains.kotlin.ir.visitors.IrElementVisitor
@@ -33,14 +32,6 @@ abstract class IrVariable : IrDeclarationBase(), IrValueDeclaration {
 
     abstract var initializer: IrExpression?
 
-    /**
-     * Variables are assignable by default. This means that they can be used in [IrSetValue].
-     * Variables are assigned in the IR even though they are not 'var' in the input. Hence
-     * the separate assignability flag.
-     */
-    override val isAssignable: Boolean
-        get() = true
-
     override fun <R, D> accept(visitor: IrElementVisitor<R, D>, data: D): R =
         visitor.visitVariable(this, data)
 

compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/expressions/impl/IrSetValueImpl.kt

@@ -12,6 +12,7 @@ import org.jetbrains.kotlin.ir.expressions.IrStatementOrigin
 import org.jetbrains.kotlin.ir.symbols.IrValueSymbol
 import org.jetbrains.kotlin.ir.types.IrType
 import org.jetbrains.kotlin.ir.util.IrElementConstructorIndicator
+import org.jetbrains.kotlin.ir.util.isAssignable
 
 class IrSetValueImpl internal constructor(
     @Suppress("UNUSED_PARAMETER")

compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/util/IrUtils.kt

@@ -1,5 +1,5 @@
 /*
- * Copyright 2010-2018 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Copyright 2010-2024 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.
  */
 
@@ -1590,4 +1590,14 @@ fun IrElement.sourceElement(): AbstractKtSourceElement? =
     else null
 
 fun IrFunction.isTopLevelInPackage(name: String, packageFqName: FqName) =
-    this.name.asString() == name && parent.kotlinFqName == packageFqName
+    this.name.asString() == name && parent.kotlinFqName == packageFqName
+
+val IrValueDeclaration.isAssignable: Boolean
+    get() = when (this) {
+        is IrValueParameter -> isAssignable
+        // Variables are assignable by default. This means that they can be used in [IrSetValue].
+        // Variables are assigned in the IR even though they are not 'var' in the input. Hence
+        // the separate assignability flag.
+        is IrVariable -> true
+        else -> error("Unexpected IrValueDeclaration class $this")
+    }

compiler/ir/ir.tree/tree-generator/src/org/jetbrains/kotlin/ir/generator/IrTree.kt

@@ -194,7 +194,6 @@ object IrTree : AbstractTreeBuilder() {
         +descriptor("ValueDescriptor")
         +symbol(valueSymbolType)
         +field("type", irTypeType)
-        +field("isAssignable", boolean, mutable = false)
     }
     val valueParameter: Element by element(Declaration) {
         needTransformMethod()
@@ -203,6 +202,7 @@ object IrTree : AbstractTreeBuilder() {
         parent(valueDeclaration)
 
         +descriptor("ParameterDescriptor")
+        +field("isAssignable", boolean, mutable = false)
         +symbol(valueParameterSymbolType)
         +field("index", int)
         +field("varargElementType", irTypeType, nullable = true)
@@ -597,16 +597,6 @@ object IrTree : AbstractTreeBuilder() {
         +field("isConst", boolean)
         +field("isLateinit", boolean)
         +field("initializer", expression, nullable = true)
-        +field("isAssignable", boolean, mutable = false) {
-            defaultValueInBase = "true"
-            withGetter = true
-            additionalImports.add(setValue)
-            kDoc = """
-            Variables are assignable by default. This means that they can be used in [${setValue.typeName}].
-            Variables are assigned in the IR even though they are not 'var' in the input. Hence
-            the separate assignability flag.
-            """.trimIndent()
-        }
     }
     val packageFragment: Element by element(Declaration) {
         ownsChildren = false