types: improve typing (#309)

packages/runtime-dom/src/modules/style.ts

@@ -1,14 +1,16 @@
 import { isString } from '@vue/shared'
 
-export function patchStyle(el: any, prev: any, next: any) {
-  const { style } = el
+type Style = string | Partial<CSSStyleDeclaration> | null
+
+export function patchStyle(el: Element, prev: Style, next: Style) {
+  const style = (el as HTMLElement).style
   if (!next) {
     el.removeAttribute('style')
   } else if (isString(next)) {
     style.cssText = next
   } else {
     for (const key in next) {
-      style[key] = next[key]
+      style[key] = next[key] as string
     }
     if (prev && !isString(prev)) {
       for (const key in prev) {