[FIR/IR generator] Add default arguments to TypeVariable constructor

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

@@ -48,7 +48,7 @@ private class TransformerPrinter(
             println()
             val elementParameterName = element.safeDecapitalizedName
             if (element.isRootElement) {
-                val elementTP = TypeVariable("E", listOf(element), variance = Variance.INVARIANT)
+                val elementTP = TypeVariable("E", listOf(element))
                 printFunctionDeclaration(
                     name = "transformElement",
                     parameters = listOf(

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

@@ -160,7 +160,7 @@ private class TypeTransformerPrinter(
 
     context(ImportCollector)
     override fun SmartPrinter.printAdditionalMethods() {
-        val typeTP = TypeVariable("Type", listOf(irTypeType.copy(nullable = true)), Variance.INVARIANT)
+        val typeTP = TypeVariable("Type", listOf(irTypeType.copy(nullable = true)))
         printFunctionDeclaration(
             name = "transformType",
             parameters = listOf(

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

@@ -283,8 +283,8 @@ fun <Self : ParametrizedTypeRef<Self, PositionTypeParameterRef>> ParametrizedTyp
 
 class TypeVariable(
     name: String,
-    val bounds: List<TypeRef>,
+    val bounds: List<TypeRef> = emptyList(),
-    val variance: Variance,
+    val variance: Variance = Variance.INVARIANT,
 ) : NamedTypeParameterRef(name)
 
 fun <P : TypeParameterRef> KClass<*>.asRef(): ClassRef<P> {