go/src/errors/wrap.go

// 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.
//
// Unwrap only calls a method of the form "Unwrap() error".
// In particular Unwrap does not unwrap errors returned by [Join].
func Unwrap(err error) error { … }

// Is reports whether any error in err's tree matches target.
//
// The tree consists of err itself, followed by the errors obtained by repeatedly
// calling its Unwrap() error or Unwrap() []error method. When err wraps multiple
// errors, Is examines err followed by a depth-first traversal of its children.
//
// 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. An Is method should only shallowly
// compare err and the target and not call [Unwrap] on either.
func Is(err, target error) bool { … }

func is(err, target error, targetComparable bool) bool { … }

// As finds the first error in err's tree that matches target, and if one is found, sets
// target to that error value and returns true. Otherwise, it returns false.
//
// The tree consists of err itself, followed by the errors obtained by repeatedly
// calling its Unwrap() error or Unwrap() []error method. When err wraps multiple
// errors, As examines err followed by a depth-first traversal of its children.
//
// 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(any) 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 As(err error, target any) bool { … }

func as(err error, target any, targetVal reflectlite.Value, targetType reflectlite.Type) bool { … }

var errorType …