parser: use ast user data to store attribution

ast/src/main/kotlin/gay/pizza/pork/ast/Definition.kt

@@ -8,5 +8,6 @@ import kotlinx.serialization.Serializable
 @SerialName("definition")
 sealed class Definition : Node() {
   abstract val symbol: Symbol
+
   abstract val modifiers: DefinitionModifiers
 }

ast/src/main/kotlin/gay/pizza/pork/ast/Node.kt

@@ -1,6 +1,7 @@
 // GENERATED CODE FROM PORK AST CODEGEN
 package gay.pizza.pork.ast
 
+import kotlinx.serialization.Transient
 import kotlinx.serialization.SerialName
 import kotlinx.serialization.Serializable
 
@@ -9,6 +10,9 @@ import kotlinx.serialization.Serializable
 sealed class Node {
   abstract val type: NodeType
 
+  @Transient
+  var data: Any? = null
+
   open fun <T> visitChildren(visitor: NodeVisitor<T>): List<T> =
     emptyList()
 

ast/src/main/kotlin/gay/pizza/pork/ast/NodeExtensions.kt

@@ -0,0 +1,6 @@
+// GENERATED CODE FROM PORK AST CODEGEN
+package gay.pizza.pork.ast
+
+@Suppress("UNCHECKED_CAST")
+fun <P> Node.data(): P? =
+  data as? P?