K2 Scripting, IR: non-class based scripts support in IR

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

@@ -26,9 +26,9 @@ abstract class IrScript : IrDeclarationBase(), IrDeclarationWithName, IrDeclarat
         IrStatementContainer, IrMetadataSourceOwner {
     abstract override val symbol: IrScriptSymbol
 
-    abstract var thisReceiver: IrValueParameter
+    abstract var thisReceiver: IrValueParameter?
 
-    abstract var baseClass: IrType
+    abstract var baseClass: IrType?
 
     abstract var explicitCallParameters: List<IrValueParameter>
 
@@ -53,7 +53,7 @@ abstract class IrScript : IrDeclarationBase(), IrDeclarationWithName, IrDeclarat
 
     override fun <D> acceptChildren(visitor: IrElementVisitor<Unit, D>, data: D) {
         statements.forEach { it.accept(visitor, data) }
-        thisReceiver.accept(visitor, data)
+        thisReceiver?.accept(visitor, data)
         explicitCallParameters.forEach { it.accept(visitor, data) }
         implicitReceiversParameters.forEach { it.accept(visitor, data) }
         providedPropertiesParameters.forEach { it.accept(visitor, data) }
@@ -62,7 +62,7 @@ abstract class IrScript : IrDeclarationBase(), IrDeclarationWithName, IrDeclarat
 
     override fun <D> transformChildren(transformer: IrElementTransformer<D>, data: D) {
         statements.transformInPlace(transformer, data)
-        thisReceiver = thisReceiver.transform(transformer, data)
+        thisReceiver = thisReceiver?.transform(transformer, data)
         explicitCallParameters = explicitCallParameters.transformIfNeeded(transformer, data)
         implicitReceiversParameters = implicitReceiversParameters.transformIfNeeded(transformer,
                 data)

compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/declarations/impl/IrScriptImpl.kt

@@ -43,9 +43,9 @@ class IrScriptImpl(
 
     override var metadata: MetadataSource? = null
 
-    override lateinit var thisReceiver: IrValueParameter
+    override var thisReceiver: IrValueParameter? = null
+    override var baseClass: IrType? = null
 
-    override lateinit var baseClass: IrType
     override lateinit var explicitCallParameters: List<IrValueParameter>
     override lateinit var implicitReceiversParameters: List<IrValueParameter>
     override lateinit var providedProperties: List<IrPropertySymbol>

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

@@ -130,7 +130,7 @@ open class DeepCopyIrTreeWithSymbols(
             declaration.startOffset,
             declaration.endOffset
         ).also { scriptCopy ->
-            scriptCopy.thisReceiver = declaration.thisReceiver.transform()
+            scriptCopy.thisReceiver = declaration.thisReceiver?.transform()
             declaration.statements.mapTo(scriptCopy.statements) { it.transform() }
             scriptCopy.earlierScripts = declaration.earlierScripts
             scriptCopy.earlierScriptsParameter = declaration.earlierScriptsParameter

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

@@ -398,8 +398,8 @@ object IrTree : AbstractTreeBuilder() {
         +symbol(scriptSymbolType)
         // NOTE: is the result of the FE conversion, because there script interpreted as a class and has receiver
         // TODO: consider removing from here and handle appropriately in the lowering
-        +field("thisReceiver", valueParameter, mutable = true, isChild = true)
-        +field("baseClass", irTypeType, mutable = true)
+        +field("thisReceiver", valueParameter, mutable = true, isChild = true, nullable = true) // K1
+        +field("baseClass", irTypeType, mutable = true, nullable = true) // K1
         +listField("explicitCallParameters", valueParameter, mutability = Var, isChild = true)
         +listField("implicitReceiversParameters", valueParameter, mutability = Var, isChild = true)
         +listField("providedProperties", propertySymbolType, mutability = Var)
@@ -408,7 +408,7 @@ object IrTree : AbstractTreeBuilder() {
         +field("earlierScriptsParameter", valueParameter, mutable = true, nullable = true, isChild = true)
         +listField("earlierScripts", scriptSymbolType, mutability = Var, nullable = true)
         +field("targetClass", classSymbolType, mutable = true, nullable = true)
-        +field("constructor", constructor, mutable = true, nullable = true)
+        +field("constructor", constructor, mutable = true, nullable = true) // K1
     }
     val simpleFunction: ElementConfig by element(Declaration) {
         visitorParent = function