1 // +build go1.13

     2 

     3 package errors

     4 

     5 import (

     6 	stderrors "errors"

     7 )

     8 

     9 // Is reports whether any error in err's chain matches target.

    10 //

    11 // The chain consists of err itself followed by the sequence of errors obtained by

    12 // repeatedly calling Unwrap.

    13 //

    14 // An error is considered to match a target if it is equal to that target or if

    15 // it implements a method Is(error) bool such that Is(target) returns true.

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

    17 

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

    19 // target to that error value and returns true.

    20 //

    21 // The chain consists of err itself followed by the sequence of errors obtained by

    22 // repeatedly calling Unwrap.

    23 //

    24 // An error matches target if the error's concrete value is assignable to the value

    25 // pointed to by target, or if the error has a method As(interface{}) bool such that

    26 // As(target) returns true. In the latter case, the As method is responsible for

    27 // setting target.

    28 //

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

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

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

    32 

    33 // Unwrap returns the result of calling the Unwrap method on err, if err's

    34 // type contains an Unwrap method returning error.

    35 // Otherwise, Unwrap returns nil.

    36 func Unwrap(err error) error {

    37 	return stderrors.Unwrap(err)

    38 }