// +build go1.13

package errors

import (

	stderrors "errors"

)

// 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.

func Is(err, target error) bool { return stderrors.Is(err, target) }

// As finds the first error in err's chain that matches target, and if so, sets

// target to that error value and returns true.

//

// 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.

//

// As will panic if target is not a non-nil pointer to either a type that implements

// error, or to any interface type. As returns false if err is nil.

func As(err error, target interface{}) bool { return stderrors.As(err, target) }

// 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 Unwrap(err error) error {

	return stderrors.Unwrap(err)

}