testing/checkers: more informative DeepEquals

testing/checkers/deepequal.go

 // Copied with small adaptations from the reflect package in the
 // Go source tree.
 
 // Copyright 2009 The Go 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 checkers
 
 import (
@@ skipping 209 matching lines @@
 func DeepEqual(a1, a2 interface{}) (bool, error) {
         errorf := func(f string, a ...interface{}) error {
                 return &mismatchError{
                         v1:   reflect.ValueOf(a1),
                         v2:   reflect.ValueOf(a2),
                         path: "",
                         how:  fmt.Sprintf(f, a...),
                 }
         }
         if a1 == nil || a2 == nil {
-                return a1 == a2, errorf("nil vs non-nil mismatch")
+                if a1 == a2 {
+                        return true, nil
+                }
+                return false, errorf("nil vs non-nil mismatch")
         }
         v1 := reflect.ValueOf(a1)
         v2 := reflect.ValueOf(a2)
         if v1.Type() != v2.Type() {
                 return false, errorf("type mismatch %s vs %s", v1.Type(), v2.Type())
         }
         return deepValueEqual("", v1, v2, make(map[visit]bool), 0)
 }
 
 // interfaceOf returns v.Interface() even if v.CanInterface() == false.
@@ skipping 50 matching lines @@
                 A int
         }
         vA := reflect.ValueOf(t).FieldByName("A")
         va := reflect.ValueOf(t).FieldByName("a")
         flagA := *flagField(&vA)
         flaga := *flagField(&va)
         if flagA&flagRO != 0 || flaga&flagRO == 0 {
                 panic("reflect.Value read-only flag has changed value")
         }
 }