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: errors.go
    path of file: ./repos/gccrs/libgo/go/cmd/go/internal/mvs
    
    the code of the file until where you have to start completion: // Copyright 2020 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 mvs

import (
	"fmt"
	"strings"

	"golang.org/x/mod/module"
)

// BuildListError decorates an error that occurred gathering requirements
// while constructing a build list. BuildListError prints the ch
    
func (e *BuildListError) Error() string {
	b := &strings.Builder{}
	stack := e.stack

	// Don't print modules at the beginning of the chain without a
	// version. These always seem to be the main module or a
	// synthetic module ("target@").
	for len(stack) > 0 && stack[0].m.Version == "" {
		stack = stack[1:]
	}

	if len(stack) == 0 {
		b.WriteString(e.Err.Error())
	} else {
		for _, elem := range stack[:len(stack)-1] {
			fmt.Fprintf(b, "%s %s\n\t", elem.m, elem.nextReason)
		}
		// Ensure that the final module path and version are included as part of the
		// error message.
		m := stack[len(stack)-1].m
		if mErr, ok := e.Err.(*module.ModuleError); ok {
			actual := module.Version{Path: mErr.Path, Version: mErr.Version}
			if v, ok := mErr.Err.(*module.InvalidVersionError); ok {
				actual.Version = v.Version
			}
			if actual == m {
				fmt.Fprintf(b, "%v", e.Err)
			} else {
				fmt.Fprintf(b, "%s (replaced by %s): %v", m, actual, mErr.Err)
			}
		} else {
			fmt.Fprintf(b, "%v", module.VersionError(m, e.Err))
		}
	}
	return b.String()
}