Swift: respond to PR comments on constructor flow

Author: rdmarsh2

swift/ql/lib/codeql/swift/dataflow/internal/DataFlowPrivate.qll

@@ -399,26 +399,13 @@ private module ReturnNodes {
     override ReturnKind getKind() { result instanceof NormalReturnKind }
   }
 
-  class SelfReturnNode extends ReturnNode, TInoutReturnNode, NodeImpl {
-    SelfParamDecl param;
-    ControlFlowNode exit;
-    SelfReturnNode() {
-      this = TInoutReturnNode(param) and
-      exit instanceof ExitNode and
-      exit.getScope() = param.getDeclaringFunction() and
-      param.getDeclaringFunction() instanceof ConstructorDecl
-    }
-    override ControlFlowNode getCfgNode() { result = exit }
-
-    override DataFlowCallable getEnclosingCallable() {
-      result = TDataFlowFunc(param.getDeclaringFunction())
-    }
-
-    ParamDecl getParameter() { result = param }
-
-    override Location getLocationImpl() { result = exit.getLocation() }
+  /**
+   * A data-flow node that represents the `self` value in a constructor being
+   * implicitly returned as the newly-constructed object
+   * */
+  class SelfReturnNode extends InoutReturnNodeImpl {
+    SelfReturnNode() { exit.getScope() instanceof ConstructorDecl }
 
-    override string toStringImpl() { result = param.toString() + "[constructor return]" }
     override ReturnKind getKind() { result instanceof NormalReturnKind }
   }