code review 2246049: json: do not write to unexported fields

src/pkg/json/decode.go

 // Copyright 2010 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.
 
 // Represents JSON data structure using native Go types: booleans, floats,
 // strings, arrays, and maps.
 
 package json
 
 import (
@@ skipping 67 matching lines @@
         Type  reflect.Type // type of Go value it could not be assigned to
 }
 
 func (e *UnmarshalTypeError) String() string {
         return "json: cannot unmarshal " + e.Value + " into Go value of type " + e.Type.String()
 }
 
 // An UnmarshalFieldError describes a JSON object key that
 // led to an unexported (and therefore unwritable) struct field.
 type UnmarshalFieldError struct {
-        Key string
-        Type *reflect.StructType
+        Key   string
+        Type  *reflect.StructType
         Field reflect.StructField
 }
 
 func (e *UnmarshalFieldError) String() string {
         return "json: cannot unmarshal object key " + strconv.Quote(e.Key) + " into unexported field " + e.Field.Name + " of type " + e.Type.String()
 }
 
 // An InvalidUnmarshalError describes an invalid argument passed to Unmarshal.
 // (The argument to Unmarshal must be a non-nil pointer.)
 type InvalidUnmarshalError struct {
@@ skipping 374 matching lines @@
                                 }
                         }
                         if !ok {
                                 // Second, exact match.
                                 f, ok = st.FieldByName(key)
                         }
                         if !ok {
                                 // Third, case-insensitive match.
                                 f, ok = st.FieldByNameFunc(func(s string) bool { return matchName(key, s) })
                         }
-                        
+
                         // Extract value; name must be exported.
                         if ok {
                                 if f.PkgPath != "" {
                                         d.saveError(&UnmarshalFieldError{key, st, f})
                                 } else {
                                         subv = sv.FieldByIndex(f.Index)
                                 }
                         }
                 }
 
@@ skipping 355 matching lines @@
 
                 // Coerce to well-formed UTF-8.
                 default:
                         rune, size := utf8.DecodeRune(s[r:])
                         r += size
                         w += utf8.EncodeRune(rune, b[w:])
                 }
         }
         return string(b[0:w]), true
 }