tailscale/types/result/result.go
Brad Fitzpatrick 01185e436f types/result, util/lineiter: add package for a result type, use it
This adds a new generic result type (motivated by golang/go#70084) to
try it out, and uses it in the new lineutil package (replacing the old
lineread package), changing that package to return iterators:
sometimes over []byte (when the input is all in memory), but sometimes
iterators over results of []byte, if errors might happen at runtime.

Updates #12912
Updates golang/go#70084

Change-Id: Iacdc1070e661b5fb163907b1e8b07ac7d51d3f83
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
2024-11-05 10:27:52 -08:00

50 lines
1.2 KiB
Go

// Copyright (c) Tailscale Inc & AUTHORS
// SPDX-License-Identifier: BSD-3-Clause
// Package result contains the Of result type, which is
// either a value or an error.
package result
// Of is either a T value or an error.
//
// Think of it like Rust or Swift's result types.
// It's named "Of" because the fully qualified name
// for callers reads result.Of[T].
type Of[T any] struct {
v T // valid if Err is nil; invalid if Err is non-nil
err error
}
// Value returns a new result with value v,
// without an error.
func Value[T any](v T) Of[T] {
return Of[T]{v: v}
}
// Error returns a new result with error err.
// If err is nil, the returned result is equivalent
// to calling Value with T's zero value.
func Error[T any](err error) Of[T] {
return Of[T]{err: err}
}
// MustValue returns r's result value.
// It panics if r.Err returns non-nil.
func (r Of[T]) MustValue() T {
if r.err != nil {
panic(r.err)
}
return r.v
}
// Value returns r's result value and error.
func (r Of[T]) Value() (T, error) {
return r.v, r.err
}
// Err returns r's error, if any.
// When r.Err returns nil, it's safe to call r.MustValue without it panicking.
func (r Of[T]) Err() error {
return r.err
}