[rust2cpg] refactor visitImpl.

joern-cli/frontends/rust2cpg/src/main/scala/io/joern/rust2cpg/astcreation/AstCreator.scala

@@ -7,14 +7,7 @@ import io.joern.rust2cpg.parser.RustNodeSyntax
 import io.joern.rust2cpg.parser.RustNodeSyntax.RustNode
 import io.joern.x2cpg.datastructures.Stack.*
 import io.joern.x2cpg.{Ast, AstCreatorBase, ValidationMode}
-import io.shiftleft.codepropertygraph.generated.nodes.{
-  NewCall,
-  NewControlStructure,
-  NewMethod,
-  NewNamespaceBlock,
-  NewNode,
-  NewTypeDecl
-}
+import io.shiftleft.codepropertygraph.generated.nodes.{NewCall, NewMethod, NewNamespaceBlock, NewNode, NewTypeDecl}
 import io.shiftleft.codepropertygraph.generated.{NodeTypes, Operators, PropertyDefaults, PropertyNames}
 import io.shiftleft.semanticcpg.language.types.structure.NamespaceTraversal
 import org.slf4j.LoggerFactory
@@ -29,14 +22,20 @@ class AstCreator(val config: Config, val parseResult: ParseResult)(implicit with
   private val logger = LoggerFactory.getLogger(getClass)
 
   protected val methodAstParentStack = new Stack[NewNode]
+  private var detachedAsts           = List.empty[Ast]
 
   override def createAst(): DiffGraphBuilder = {
     val sourceFile = parseResult.ast.asInstanceOf[RustNodeSyntax.SourceFile]
     val ast        = visitSourceFile(sourceFile)
     Ast.storeInDiffGraph(ast, diffGraph)
+    detachedAsts.foreach(Ast.storeInDiffGraph(_, diffGraph))
     diffGraph
   }
 
+  protected def addDetachedAst(ast: Ast): Unit = {
+    detachedAsts = ast :: detachedAsts
+  }
+
   // NB: rust_ast_gen uses 0-based line/column
   override protected def line(node: RustNode): Option[Int] =
     if (node.isMacroExpanded) None else node.startLine.map(_ + 1)

joern-cli/frontends/rust2cpg/src/main/scala/io/joern/rust2cpg/astcreation/RustVisitor.scala

@@ -355,25 +355,35 @@ trait RustVisitor(implicit withSchemaValidation: ValidationMode) { this: AstCrea
   //  AssocItemList
   private def visitImpl(impl: Impl): Seq[Ast] = {
     if (impl.forKwToken.isDefined) {
-      impl.typ match {
-        case implTrait :: implType :: Nil =>
-          val typeDecl = typeDeclForTraitImpl(impl, implTrait, implType)
-          methodAstParentStack.push(typeDecl)
-          val methodAsts = impl.assocItemList.assocItem.collect { case fn: Fn => visitFn(fn) }
-          methodAstParentStack.pop()
-          Ast(typeDecl).withChildren(methodAsts) :: Nil
-        case _ => notHandledYet(impl) :: Nil
-      }
+      lowerImplFor(impl) :: Nil
     } else {
-      methodAstParentStack.push(typeDeclForImpl(impl))
-      val methodAsts = impl.assocItemList.assocItem.collect { case fn: Fn => visitFn(fn) }
-      methodAstParentStack.pop()
-      // TODO: remove this side-effect once ref-linker/scope is in.
-      methodAsts.foreach(Ast.storeInDiffGraph(_, diffGraph))
+      lowerInherentImplAsDetachedAst(impl)
       Nil
     }
   }
 
+  // There can be at most one `impl X for Y` (for some X, Y) in the same file/project.
+  private def lowerImplFor(impl: Impl): Ast = {
+    impl.typ match {
+      case implTrait :: implType :: Nil =>
+        val typeDecl = typeDeclForTraitImpl(impl, implTrait, implType)
+        methodAstParentStack.push(typeDecl)
+        val methodAsts = impl.assocItemList.assocItem.collect { case fn: Fn => visitFn(fn) }
+        methodAstParentStack.pop()
+        Ast(typeDecl).withChildren(methodAsts)
+      case _ => notHandledYet(impl)
+    }
+  }
+
+  // There can be multiple `impl X` in the same file/project, so we lower their
+  // methods as detached Asts. The AstLinker pass shall later create the appropriate Ast edges.
+  private def lowerInherentImplAsDetachedAst(impl: Impl): Unit = {
+    methodAstParentStack.push(typeDeclForImpl(impl))
+    val methodAsts = impl.assocItemList.assocItem.collect { case fn: Fn => visitFn(fn) }
+    methodAstParentStack.pop()
+    methodAsts.foreach(addDetachedAst)
+  }
+
   // Trait =
   //  Attr* Visibility?
   //  'unsafe'? 'auto'?