refactor: simplify slot extraneous child check

packages/compiler-core/src/transforms/vSlot.ts

@@ -66,18 +66,18 @@ export function buildSlots(
   // 2. Iterate through children and check for template slots
   //    <template v-slot:foo="{ prop }">
   let hasTemplateSlots = false
+  let extraneousChild: ChildNode | undefined = undefined
   const seenSlotNames = new Set<string>()
-  const nonSlotChildren: ChildNode[] = []
   for (let i = 0; i < children.length; i++) {
     const child = children[i]
+    let slotDir
     if (
       child.type === NodeTypes.ELEMENT &&
-      child.tagType === ElementTypes.TEMPLATE
+      child.tagType === ElementTypes.TEMPLATE &&
+      (slotDir = child.props.find(isVSlot))
     ) {
-      const { props, children, loc: nodeLoc } = child
-      const slotDir = props.find(isVSlot)
-      if (slotDir) {
       hasTemplateSlots = true
+      const { children, loc: nodeLoc } = child
       const { arg: slotName, exp: slotProps, loc: dirLoc } = slotDir
       if (explicitDefaultSlot) {
         // already has on-component default slot - this is incorrect usage.
@@ -104,19 +104,16 @@ export function buildSlots(
           buildSlot(slotName || `default`, slotProps, children, nodeLoc)
         )
       }
-      } else {
+    } else if (!extraneousChild) {
-        nonSlotChildren.push(child)
+      extraneousChild = child
-      }
-    } else {
-      nonSlotChildren.push(child)
     }
   }
 
-  if (hasTemplateSlots && nonSlotChildren.length) {
+  if (hasTemplateSlots && extraneousChild) {
     context.onError(
       createCompilerError(
         ErrorCodes.X_EXTRANEOUS_NON_SLOT_CHILDREN,
-        nonSlotChildren[0].loc
+        extraneousChild.loc
       )
     )
   }