fix(warn): do not warn when destructuring in v-for

Fixes vuejs#7096

Author: posva

src/compiler/error-detector.js

@@ -80,7 +80,11 @@ function checkIdentifier (
 ) {
   if (typeof ident === 'string') {
     try {
-      new Function(`var ${ident}`)
+      // #7096 use an array because it makes it possible to destructure
+      // arrays and objects:
+      // var { foo } = [] works
+      // var [ foo ] = [] works
+      new Function(`var ${ident} = []`)
     } catch (e) {
       errors.push(`invalid ${type} "${ident}" in expression: ${text.trim()}`)
     }

test/unit/features/options/template.spec.js

@@ -78,6 +78,25 @@ describe('Options template', () => {
     expect('Raw expression: v-for="(1, 2) in a----"').toHaveBeenWarned()
   })
 
+  // #7096
+  it('should not warn with object destructuring in v-for', () => {
+    new Vue({
+      data: { items: [] },
+      template: '<div><div v-for="{ foo } in items"></div></div>'
+    }).$mount()
+    expect('Error compiling template').not.toHaveBeenWarned()
+    expect('invalid v-for alias ').not.toHaveBeenWarned()
+  })
+
+  it('should not warn with array destructuring in v-for', () => {
+    new Vue({
+      data: { items: [] },
+      template: '<div><div v-for="[ foo ] in items"></div></div>'
+    }).$mount()
+    expect('Error compiling template').not.toHaveBeenWarned()
+    expect('invalid v-for alias ').not.toHaveBeenWarned()
+  })
+
   it('warn error in generated function (v-on)', () => {
     new Vue({
       template: `<div @click="delete('Delete')"></div>`,