chore: annotate generated slot flag

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

@@ -33,7 +33,7 @@ import {
 } from '../utils'
 import { CREATE_SLOTS, RENDER_LIST, WITH_CTX } from '../runtimeHelpers'
 import { parseForExpression, createForLoopParams } from './vFor'
-import { SlotFlags } from '@vue/shared'
+import { SlotFlags, slotFlagsText } from '@vue/shared'
 
 const defaultFallback = createSimpleExpression(`undefined`, false)
 
@@ -334,7 +334,10 @@ export function buildSlots(
         `_`,
         // 2 = compiled but dynamic = can skip normalization, but must run diff
         // 1 = compiled and static = can skip normalization AND diff as optimized
-        createSimpleExpression('' + slotFlag, false)
+        createSimpleExpression(
+          slotFlag + (__DEV__ ? ` /* ${slotFlagsText[slotFlag]} */` : ``),
+          false
+        )
       )
     ),
     loc