// +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)
}
