fix(compiler): fix Elements not making a new ParseSourceSpan (#31190)

Change the Element constructor in r3_ast to create a new ParseSourceSpan when regenerating it rather than extending an object, which does not contain the overloaded toString().

PR Close #31190

packages/compiler/test/render3/r3_template_transform_spec.ts

@@ -95,7 +95,17 @@ function expectFromR3Nodes(nodes: t.Node[]) {
   return expect(humanizer.result);
 }
 
+function expectSpanFromHtml(html: string) {
+  const {nodes} = parse(html);
+  return expect(nodes[0] !.sourceSpan.toString());
+}
+
 describe('R3 template transform', () => {
+  describe('ParseSpan on nodes toString', () => {
+    it('should create valid text span on Element with adjacent start and end tags',
+       () => { expectSpanFromHtml('<div></div>').toBe('<div></div>'); });
+  });
+
   describe('Nodes without binding', () => {
     it('should parse text nodes', () => {
       expectFromHtml('a').toEqual([