// Copyright 2018 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 errors

import (
	
)

// Unwrap returns the result of calling the Unwrap method on err, if err's
// type contains an Unwrap method returning error.
// Otherwise, Unwrap returns nil.
func ( error) error {
	,  := .(interface {
		() error
	})
	if ! {
		return nil
	}
	return .()
}

// Is reports whether any error in err's chain matches target.
//
// The chain consists of err itself followed by the sequence of errors obtained by
// repeatedly calling Unwrap.
//
// An error is considered to match a target if it is equal to that target or if
// it implements a method Is(error) bool such that Is(target) returns true.
//
// An error type might provide an Is method so it can be treated as equivalent
// to an existing error. For example, if MyError defines
//
//	func (m MyError) Is(target error) bool { return target == fs.ErrExist }
//
// then Is(MyError{}, fs.ErrExist) returns true. See syscall.Errno.Is for
// an example in the standard library.
func (,  error) bool {
	if  == nil {
		return  == 
	}

	 := reflectlite.TypeOf().Comparable()
	for {
		if  &&  ==  {
			return true
		}
		if ,  := .(interface{ (error) bool });  && .() {
			return true
		}
		// TODO: consider supporting target.Is(err). This would allow
		// user-definable predicates, but also may allow for coping with sloppy
		// APIs, thereby making it easier to get away with them.
		if  = Unwrap();  == nil {
			return false
		}
	}
}

// As finds the first error in err's chain that matches target, and if so, sets
// target to that error value and returns true. Otherwise, it returns false.
//
// The chain consists of err itself followed by the sequence of errors obtained by
// repeatedly calling Unwrap.
//
// An error matches target if the error's concrete value is assignable to the value
// pointed to by target, or if the error has a method As(interface{}) bool such that
// As(target) returns true. In the latter case, the As method is responsible for
// setting target.
//
// An error type might provide an As method so it can be treated as if it were a
// different error type.
//
// As panics if target is not a non-nil pointer to either a type that implements
// error, or to any interface type.
func ( error,  interface{}) bool {
	if  == nil {
		panic("errors: target cannot be nil")
	}
	 := reflectlite.ValueOf()
	 := .Type()
	if .Kind() != reflectlite.Ptr || .IsNil() {
		panic("errors: target must be a non-nil pointer")
	}
	 := .Elem()
	if .Kind() != reflectlite.Interface && !.Implements(errorType) {
		panic("errors: *target must be interface or implement error")
	}
	for  != nil {
		if reflectlite.TypeOf().AssignableTo() {
			.Elem().Set(reflectlite.ValueOf())
			return true
		}
		if ,  := .(interface{ (interface{}) bool });  && .() {
			return true
		}
		 = Unwrap()
	}
	return false
}

var errorType = reflectlite.TypeOf((*error)(nil)).Elem()