You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: discard.go
    path of file: ./repos/docker-ce/components/cli/vendor/github.com/gogo/protobuf/proto
    
    the code of the file until where you have to start completion: // Go support for Protocol Buffers - Google's data interchange format
//
// Copyright 2017 The Go Authors.  All rights reserved.
// https://github.com/golang/protobuf
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
//     * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
//     * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
//     * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
    
func (di *discardInfo) computeDiscardInfo() {
	di.lock.Lock()
	defer di.lock.Unlock()
	if di.initialized != 0 {
		return
	}
	t := di.typ
	n := t.NumField()

	for i := 0; i < n; i++ {
		f := t.Field(i)
		if strings.HasPrefix(f.Name, "XXX_") {
			continue
		}

		dfi := discardFieldInfo{field: toField(&f)}
		tf := f.Type

		// Unwrap tf to get its most basic type.
		var isPointer, isSlice bool
		if tf.Kind() == reflect.Slice && tf.Elem().Kind() != reflect.Uint8 {
			isSlice = true
			tf = tf.Elem()
		}
		if tf.Kind() == reflect.Ptr {
			isPointer = true
			tf = tf.Elem()
		}
		if isPointer && isSlice && tf.Kind() != reflect.Struct {
			panic(fmt.Sprintf("%v.%s cannot be a slice of pointers to primitive types", t, f.Name))
		}

		switch tf.Kind() {
		case reflect.Struct:
			switch {
			case !isPointer:
				panic(fmt.Sprintf("%v.%s cannot be a direct struct value", t, f.Name))
			case isSlice: // E.g., []*pb.T
				discardInfo := getDiscardInfo(tf)
				dfi.discard = func(src pointer) {
					sps := src.getPointerSlice()
					for _, sp := range sps {
						if !sp.isNil() {
							discardInfo.discard(sp)
						}
					}
				}
			default: // E.g., *pb.T
				discardInfo := getDiscardInfo(tf)
				dfi.discard = func(src pointer) {
					sp := src.getPointer()
					if !sp.isNil() {
						discardInfo.discard(sp)
					}
				}
			}
		case reflect.Map:
			switch {
			case isPointer || isSlice:
				panic(fmt.Sprintf("%v.%s cannot be a pointer to a map or a slice of map values", t, f.Name))
			default: // E.g., map[K]V
				if tf.Elem().Kind() == reflect.Ptr { // Proto struct (e.g., *T)
					dfi.discard = func(src pointer) {
						sm := src.asPointerTo(tf).Elem()
						if sm.Len() == 0 {
							return
						}
						for _, key := range sm.MapKeys() {
							val := sm.MapIndex(key)
							DiscardUnknown(val.Interface().(Message))
						}
					}
				} else {
					dfi.discard = func(pointer) {} // Noop
				}
			}
		case reflect.Interface:
			// Must be oneof field.
			switch {
			case isPointer || isSlice:
				panic(fmt.Sprintf("%v.%s cannot be a pointer to a interface or a slice of interface values", t, f.Name))
			default: // E.g., interface{}
				// TODO: Make this faster?
				dfi.discard = func(src pointer) {
					su := src.asPointerTo(tf).Elem()
					if !su.IsNil() {
						sv := su.Elem().Elem().Field(0)
						if sv.Kind() == reflect.Ptr && sv.IsNil() {
							return
						}
						switch sv.Type().Kind() {
						case reflect.Ptr: // Proto struct (e.g., *T)
							DiscardUnknown(sv.Interface().(Message))
						}
					}
				}
			}
		default:
			continue
		}
		di.fields = append(di.fields, dfi)
	}

	di.unrecognized = invalidField
	if f, ok := t.FieldByName("XXX_unrecognized"); ok {
		if f.Type != reflect.TypeOf([]byte{}) {
			panic("expected XXX_unrecognized to be of type []byte")
		}
		di.unrecognized = toField(&f)
	}

	atomic.StoreInt32(&di.initialized, 1)
}