chore: use const instead of let (#283)

fisker · yyx990803 · commit 1fbb4d22fa16 · 2019-10-14T23:15:36.000-04:00
diff --git a/packages/runtime-core/src/warning.ts b/packages/runtime-core/src/warning.ts
@@ -7,7 +7,7 @@ type ComponentVNode = VNode & {
   type: Component
 }
 
-let stack: VNode[] = []
+const stack: VNode[] = []
 
 type TraceEntry = {
   vnode: ComponentVNode
