feat(compiler-core): more hoisting optimizations (#276)

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

@@ -2,6 +2,7 @@ import {
   RootNode,
   NodeTypes,
   TemplateChildNode,
+  SimpleExpressionNode,
   ElementTypes,
   ElementCodegenNode,
   PlainElementNode,
@@ -11,7 +12,7 @@ import {
 } from '../ast'
 import { TransformContext } from '../transform'
 import { APPLY_DIRECTIVES } from '../runtimeHelpers'
-import { PatchFlags } from '@vue/shared'
+import { PatchFlags, isString, isSymbol } from '@vue/shared'
 import { isSlotOutlet, findProp } from '../utils'
 
 function hasDynamicKey(node: ElementNode) {
@@ -107,7 +108,7 @@ function getPatchFlag(node: PlainElementNode): number | undefined {
 }
 
 function isStaticNode(
-  node: TemplateChildNode,
+  node: TemplateChildNode | SimpleExpressionNode,
   resultCache: Map<TemplateChildNode, boolean>
 ): boolean {
   switch (node.type) {
@@ -119,7 +120,7 @@ function isStaticNode(
         return resultCache.get(node) as boolean
       }
       const flag = getPatchFlag(node)
-      if (!flag) {
+      if (!flag || flag === PatchFlags.TEXT) {
         // element self is static. check its children.
         for (let i = 0; i < node.children.length; i++) {
           if (!isStaticNode(node.children[i], resultCache)) {
@@ -137,9 +138,17 @@ function isStaticNode(
       return true
     case NodeTypes.IF:
     case NodeTypes.FOR:
-    case NodeTypes.INTERPOLATION:
-    case NodeTypes.COMPOUND_EXPRESSION:
       return false
+    case NodeTypes.INTERPOLATION:
+      return isStaticNode(node.content, resultCache)
+    case NodeTypes.SIMPLE_EXPRESSION:
+      return node.isConstant
+    case NodeTypes.COMPOUND_EXPRESSION:
+      return node.children.every(child => {
+        return (
+          isString(child) || isSymbol(child) || isStaticNode(child, resultCache)
+        )
+      })
     default:
       if (__DEV__) {
         const exhaustiveCheck: never = node