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01185e436f
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>
50 lines
1.2 KiB
Go
50 lines
1.2 KiB
Go
// Copyright (c) Tailscale Inc & AUTHORS
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// SPDX-License-Identifier: BSD-3-Clause
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// Package result contains the Of result type, which is
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// either a value or an error.
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package result
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// Of is either a T value or an error.
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//
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// Think of it like Rust or Swift's result types.
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// It's named "Of" because the fully qualified name
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// for callers reads result.Of[T].
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type Of[T any] struct {
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v T // valid if Err is nil; invalid if Err is non-nil
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err error
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}
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// Value returns a new result with value v,
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// without an error.
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func Value[T any](v T) Of[T] {
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return Of[T]{v: v}
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}
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// Error returns a new result with error err.
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// If err is nil, the returned result is equivalent
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// to calling Value with T's zero value.
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func Error[T any](err error) Of[T] {
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return Of[T]{err: err}
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}
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// MustValue returns r's result value.
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// It panics if r.Err returns non-nil.
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func (r Of[T]) MustValue() T {
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if r.err != nil {
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panic(r.err)
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}
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return r.v
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}
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// Value returns r's result value and error.
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func (r Of[T]) Value() (T, error) {
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return r.v, r.err
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}
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// Err returns r's error, if any.
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// When r.Err returns nil, it's safe to call r.MustValue without it panicking.
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func (r Of[T]) Err() error {
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return r.err
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}
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