fix: change Node#parentElement to allow non-HTMLElement parents

CLAUDE.md

@@ -21,6 +21,8 @@ This project generates alternative TypeScript standard library definitions with
 
 - **`TypeScript/`** - Git submodule containing the official TypeScript repository for source lib files
 
+  - Note: `TypeScript/lib/lib.dom.d.ts` and `TypeScript/lib/lib.es5.d.ts` are HUGE. Never try to read the whole file at once. Always grep for specific parts.
+
 - **`tests/`** - Type-level tests using `tsd` to verify the improved type definitions work correctly
 
 ## Essential Commands

generated/lib.dom.d.ts

@@ -19836,7 +19836,7 @@ interface Node extends EventTarget {
    *
    * [MDN Reference](https://developer.mozilla.org/docs/Web/API/Node/parentElement)
    */
-  readonly parentElement: HTMLElement | null;
+  readonly parentElement: Element | null;
   /**
    * Returns the parent.
    *
@@ -19941,6 +19941,12 @@ interface Node extends EventTarget {
   readonly DOCUMENT_POSITION_CONTAINED_BY: 0x10;
   readonly DOCUMENT_POSITION_IMPLEMENTATION_SPECIFIC: 0x20;
 }
+//     /**
+//      * Returns the parent element.
+//      *
+//      * [MDN Reference](https://developer.mozilla.org/docs/Web/API/Node/parentElement)
+//      */
+//     readonly parentElement: HTMLElement | null;
 
 declare var Node: {
   prototype: Node;

lib/lib.dom.d.ts

@@ -255,3 +255,12 @@ interface Document
 interface DocumentFragment extends Node, NonElementParentNode, ParentNode {
   getElementById(elementId: string): Element | null;
 }
+
+interface Node extends EventTarget {
+  /**
+   * Returns the parent element.
+   *
+   * [MDN Reference](https://developer.mozilla.org/docs/Web/API/Node/parentElement)
+   */
+  readonly parentElement: Element | null;
+}

tests/src/dom.ts

@@ -161,3 +161,29 @@ const test = async (url: string) => {
   const svgElement: SVGElement = {} as SVGElement;
   const elementOrNull: typeof element = svgElement;
 }
+
+// Node.parentElement
+{
+  const div = document.createElement("div");
+  const parent = div.parentElement;
+  expectType<Element | null>(parent);
+
+  // Verify that the return type is not specifically HTMLElement
+  expectNotType<HTMLElement | null>(parent);
+
+  // Verify that SVGElement can be assigned to parentElement (without type assertion)
+  const svgElement: SVGElement = {} as SVGElement;
+  const elementOrNull: typeof parent = svgElement;
+
+  // Test with SVG elements
+  const svgElement2 = document.createElementNS("http://www.w3.org/2000/svg", "circle");
+  const svgParent = svgElement2.parentElement;
+  expectType<Element | null>(svgParent);
+
+  // Verify SVG elements work with parentElement
+  if (svgParent) {
+    expectType<Element>(svgParent);
+    // Should be able to call methods available on Element
+    svgParent.getAttribute("id");
+  }
+}