[ruby] Re-implemented "Ignore "Throwaway" AST Structures (#4982)"

This correctly prevents re-use of nodes that are already being used elsewhere by ensuring deep copies.

joern-cli/frontends/rubysrc2cpg/src/main/scala/io/joern/rubysrc2cpg/astcreation/AstForFunctionsCreator.scala

@@ -26,10 +26,10 @@ import scala.collection.mutable
 
 trait AstForFunctionsCreator(implicit withSchemaValidation: ValidationMode) { this: AstCreator =>
 
- /** As expressions may be discarded, we cannot store closure ASTs in the diffgraph at the point of creation. We need
- * to only write these at the end.
+ /** As expressions may be discarded, we cannot store closure ASTs in the diffgraph at the point of creation. So we
+ * assume every reference to this map means that the closure AST was successfully propagated.
  */
- protected val closureToRefs = mutable.Map.empty[RubyExpression, Seq[Ast]]
+ protected val closureToRefs = mutable.Map.empty[RubyExpression, Seq[NewNode]]
 
  /** Creates method declaration related structures.
  * @param node

joern-cli/frontends/rubysrc2cpg/src/main/scala/io/joern/rubysrc2cpg/astcreation/AstForStatementsCreator.scala

@@ -93,18 +93,18 @@ trait AstForStatementsCreator(implicit withSchemaValidation: ValidationMode) { t
  protected def astForDoBlock(block: Block & RubyExpression): Seq[Ast] = {
  // Create closure structures: [MethodDecl, TypeRef, MethodRef]
  if (closureToRefs.contains(block)) {
- closureToRefs(block)
+ closureToRefs(block).map(x => Ast(x.copy))
  } else {
  val methodName = nextClosureName()
 
- val methodAstsWithRefs = block.body match {
+ val methodRefAsts = block.body match {
  case x: Block =>
  astForMethodDeclaration(x.toMethodDeclaration(methodName, Option(block.parameters)), isClosure = true)
  case _ =>
  astForMethodDeclaration(block.toMethodDeclaration(methodName, Option(block.parameters)), isClosure = true)
  }
- closureToRefs.put(block, methodAstsWithRefs)
- methodAstsWithRefs
+ closureToRefs.put(block, methodRefAsts.flatMap(_.root))
+ methodRefAsts
  }
  }