Make LazyMultiError only constructable via function

common/errors/multierror_test.go

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 package errors
 
 import (
         "errors"
         "sync"
         "testing"
@@ skipping 47 matching lines @@
         Convey("Fix passes through", t, func() {
                 e := errors.New("unique")
                 So(Fix(e), ShouldEqual, e)
         })
 }
 
 func TestLazyMultiError(t *testing.T) {
         t.Parallel()
 
         Convey("Test LazyMultiError", t, func() {
-                lme := LazyMultiError{Size: 10}
+                lme := NewLazyMultiError(10)
                 So(lme.Get(), ShouldEqual, nil)
 
                 e := errors.New("sup")
                 lme.Assign(6, e)
                 So(lme.Get(), ShouldResemble,
                         MultiError{nil, nil, nil, nil, nil, nil, e, nil, nil, nil})
 
                 lme.Assign(2, e)
                 So(lme.Get(), ShouldResemble,
                         MultiError{nil, nil, e, nil, nil, nil, e, nil, nil, nil})
 
                 So(func() { lme.Assign(20, e) }, ShouldPanic)
 
                 Convey("Try to freak out the race detector", func() {
-                        lme := LazyMultiError{Size: 64}
+                        lme := NewLazyMultiError(64)
                         Convey("all nils", func() {
                                 wg := sync.WaitGroup{}
                                 for i := 0; i < 64; i++ {
                                         wg.Add(1)
                                         go func(i int) {
                                                 lme.Assign(i, nil)
                                                 wg.Done()
                                         }(i)
                                 }
                                 wg.Wait()
@@ skipping 35 matching lines @@
                                 wg.Wait()
                                 me := make(MultiError, 64)
                                 for i := range me {
                                         me[i] = wow
                                 }
                                 So(lme.Get(), ShouldResemble, me)
                         })
                 })
         })
 }