Auto merge of #29456 - 2shiori17:issue-29097, r=mukilan

Make HTMLInputElement.list an HTMLDataListElement

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---
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- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [x] These changes fix #29097

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- [ ] There are tests for these changes OR
- [x] These changes do not require tests because the only change is the return type.

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components/script/dom/htmlinputelement.rs

@@ -744,7 +744,7 @@ impl HTMLInputElement {
     }
 
     // https://html.spec.whatwg.org/multipage/#concept-input-list
-    fn suggestions_source_element(&self) -> Option<DomRoot<HTMLElement>> {
+    fn suggestions_source_element(&self) -> Option<DomRoot<HTMLDataListElement>> {
         let list_string = self
             .upcast::<Element>()
             .get_string_attribute(&local_name!("list"));
@@ -762,10 +762,7 @@ impl HTMLInputElement {
             });
         first_with_id
             .as_ref()
-            .and_then(|el| {
-                el.downcast::<HTMLDataListElement>()
-                    .map(|data_el| data_el.upcast::<HTMLElement>())
-            })
+            .and_then(|el| el.downcast::<HTMLDataListElement>())
             .map(|el| DomRoot::from_ref(&*el))
     }
 
@@ -1314,7 +1311,7 @@ impl HTMLInputElementMethods for HTMLInputElement {
     make_setter!(SetMin, "min");
 
     // https://html.spec.whatwg.org/multipage/#dom-input-list
-    fn GetList(&self) -> Option<DomRoot<HTMLElement>> {
+    fn GetList(&self) -> Option<DomRoot<HTMLDataListElement>> {
         self.suggestions_source_element()
     }
 

components/script/dom/webidls/HTMLInputElement.webidl

@@ -39,7 +39,7 @@ interface HTMLInputElement : HTMLElement {
            attribute boolean indeterminate;
   // [CEReactions]
   //          attribute DOMString inputMode;
-  readonly attribute HTMLElement? list;
+  readonly attribute HTMLDataListElement? list;
   [CEReactions]
            attribute DOMString max;
   [CEReactions, SetterThrows]