libgo/go/fmt/errors.go

   1 // Copyright 2018 The Go Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style
   3 // license that can be found in the LICENSE file.
   4
   5 package fmt
   6
   7 import "errors"
   8
   9 // Errorf formats according to a format specifier and returns the string as a
  10 // value that satisfies error.
  11 //
  12 // If the format specifier includes a %w verb with an error operand,
  13 // the returned error will implement an Unwrap method returning the operand. It is
  14 // invalid to include more than one %w verb or to supply it with an operand
  15 // that does not implement the error interface. The %w verb is otherwise
  16 // a synonym for %v.
  17 func Errorf(format string, a ...any) error {
  18         p := newPrinter()
  19         p.wrapErrs = true
  20         p.doPrintf(format, a)
  21         s := string(p.buf)
  22         var err error
  23         if p.wrappedErr == nil {
  24                 err = errors.New(s)
  25         } else {
  26                 err = &wrapError{s, p.wrappedErr}
  27         }
  28         p.free()
  29         return err
  30 }
  31
  32 type wrapError struct {
  33         msg string
  34         err error
  35 }
  36
  37 func (e *wrapError) Error() string {
  38         return e.msg
  39 }
  40
  41 func (e *wrapError) Unwrap() error {
  42         return e.err
  43 }