go errors 源码
golang errors 代码
文件路径：/src/go/scanner/errors.go
// 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 scanner
import (
"fmt"
"go/token"
"io"
"sort"
)
// In an ErrorList, an error is represented by an *Error.
// The position Pos, if valid, points to the beginning of
// the offending token, and the error condition is described
// by Msg.
type Error struct {
Pos token.Position
Msg string
}
// Error implements the error interface.
func (e Error) Error() string {
if e.Pos.Filename != "" || e.Pos.IsValid() {
// don't print "<unknown position>"
// TODO(gri) reconsider the semantics of Position.IsValid
return e.Pos.String() + ": " + e.Msg
}
return e.Msg
}
// ErrorList is a list of *Errors.
// The zero value for an ErrorList is an empty ErrorList ready to use.
type ErrorList []*Error
// Add adds an Error with given position and error message to an ErrorList.
func (p *ErrorList) Add(pos token.Position, msg string) {
*p = append(*p, &Error{pos, msg})
}
// Reset resets an ErrorList to no errors.
func (p *ErrorList) Reset() { *p = (*p)[0:0] }
// ErrorList implements the sort Interface.
func (p ErrorList) Len() int { return len(p) }
func (p ErrorList) Swap(i, j int) { p[i], p[j] = p[j], p[i] }
func (p ErrorList) Less(i, j int) bool {
e := &p[i].Pos
f := &p[j].Pos
// Note that it is not sufficient to simply compare file offsets because
// the offsets do not reflect modified line information (through //line
// comments).
if e.Filename != f.Filename {
return e.Filename < f.Filename
}
if e.Line != f.Line {
return e.Line < f.Line
}
if e.Column != f.Column {
return e.Column < f.Column
}
return p[i].Msg < p[j].Msg
}
// Sort sorts an ErrorList. *Error entries are sorted by position,
// other errors are sorted by error message, and before any *Error
// entry.
func (p ErrorList) Sort() {
sort.Sort(p)
}
// RemoveMultiples sorts an ErrorList and removes all but the first error per line.
func (p *ErrorList) RemoveMultiples() {
sort.Sort(p)
var last token.Position // initial last.Line is != any legal error line
i := 0
for _, e := range *p {
if e.Pos.Filename != last.Filename || e.Pos.Line != last.Line {
last = e.Pos
(*p)[i] = e
i++
}
}
*p = (*p)[0:i]
}
// An ErrorList implements the error interface.
func (p ErrorList) Error() string {
switch len(p) {
case 0:
return "no errors"
case 1:
return p[0].Error()
}
return fmt.Sprintf("%s (and %d more errors)", p[0], len(p)-1)
}
// Err returns an error equivalent to this error list.
// If the list is empty, Err returns nil.
func (p ErrorList) Err() error {
if len(p) == 0 {
return nil
}
return p
}
// PrintError is a utility function that prints a list of errors to w,
// one error per line, if the err parameter is an ErrorList. Otherwise
// it prints the err string.
func PrintError(w io.Writer, err error) {
if list, ok := err.(ErrorList); ok {
for _, e := range list {
fmt.Fprintf(w, "%s\n", e)
}
} else if err != nil {
fmt.Fprintf(w, "%s\n", err)
}
}
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