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// Copyright 2020 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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//go:build !go1.13
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// +build !go1.13
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package errors
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import "reflect"
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// Is is a copy of Go 1.13's errors.Is for use with older Go versions.
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func Is(err, target error) bool {
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	if target == nil {
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		return err == target
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	}
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	isComparable := reflect.TypeOf(target).Comparable()
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	for {
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		if isComparable && err == target {
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			return true
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		}
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		if x, ok := err.(interface{ Is(error) bool }); ok && x.Is(target) {
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			return true
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		}
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		if err = unwrap(err); err == nil {
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			return false
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		}
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	}
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}
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func unwrap(err error) error {
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	u, ok := err.(interface {
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		Unwrap() error
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	})
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	if !ok {
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		return nil
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	}
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	return u.Unwrap()
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}
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