Stop checking _parent and _root of external types

Since #283, it's
incorrect to assume that `_parent` should be `this` and `_root` should
be `this._root` for external types. Instead, when crossing the .ksy spec
boundary to an external type `obj`, `obj._root == obj` and
`obj._parent == null` should hold, but we will not check that for now.

Author: generalmimon

shared/src/main/scala/io/kaitai/struct/languages/JavaCompiler.scala

@@ -1042,8 +1042,6 @@ class JavaCompiler(typeProvider: ClassTypeProvider, config: RuntimeConfig)
   }
 
   override def attrParentParamCheck(actualParentExpr: Ast.expr, ut: UserType, shouldDependOnIo: Option[Boolean], msg: String): Unit = {
-    if (ut.isOpaque)
-      return
     /** @note Must be kept in sync with [[JavaCompiler.parseExpr]] */
     val (expectedParent, dependsOnIo) = ut.forcedParent match {
       case Some(USER_TYPE_NO_PARENT) => ("null", false)

shared/src/main/scala/io/kaitai/struct/languages/PythonCompiler.scala

@@ -804,8 +804,6 @@ class PythonCompiler(typeProvider: ClassTypeProvider, config: RuntimeConfig)
   }
 
   override def attrParentParamCheck(actualParentExpr: Ast.expr, ut: UserType, shouldDependOnIo: Option[Boolean], msg: String): Unit = {
-    if (ut.isOpaque)
-      return
     /** @note Must be kept in sync with [[PythonCompiler.parseExpr]] */
     val (expectedParent, dependsOnIo) = ut.forcedParent match {
       case Some(USER_TYPE_NO_PARENT) => ("None", false)

shared/src/main/scala/io/kaitai/struct/languages/components/GenericChecks.scala

@@ -390,12 +390,17 @@ trait GenericChecks extends LanguageCompiler with EveryReadIsExpression {
 
   def attrUserTypeCheck(id: Identifier, utExpr: Ast.expr, ut: UserType, shouldDependOnIo: Option[Boolean]): Unit = {
     /** @note Must be kept in sync with [[JavaCompiler.parseExpr]] */
-    if (!ut.isOpaque) {
+    if (!ut.isExternal(typeProvider.nowClass)) {
+      // TODO: perhaps it would make sense to enforce `obj._root == obj` and `obj._parent == null`
+      // for non-opaque external types in the future, but for now we won't perform any checks on
+      // external types
       attrUserTypeParamCheck(id, ut, utExpr, RootIdentifier, CalcKaitaiStructType(), Ast.expr.Name(Ast.identifier(Identifier.ROOT)), shouldDependOnIo)
+      attrParentParamCheck(id, Ast.expr.Attribute(utExpr, Ast.identifier(Identifier.PARENT)), ut, shouldDependOnIo)
     }
-    attrParentParamCheck(id, Ast.expr.Attribute(utExpr, Ast.identifier(Identifier.PARENT)), ut, shouldDependOnIo)
-    (ut.classSpec.get.params, ut.args).zipped.foreach { (paramDef, argExpr) =>
-      attrUserTypeParamCheck(id, ut, utExpr, paramDef.id, paramDef.dataType, argExpr, shouldDependOnIo)
+    if (!ut.isOpaque) {
+      (ut.classSpec.get.params, ut.args).zipped.foreach { (paramDef, argExpr) =>
+        attrUserTypeParamCheck(id, ut, utExpr, paramDef.id, paramDef.dataType, argExpr, shouldDependOnIo)
+      }
     }
   }