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// Copyright (c) 2020, the Dart project authors. Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.
/// A handle on a [Future] that detaches from the original evaluation context
/// after it has resolved.
/// A [Future] holds the Zone it was created in and may hold references to
/// `async` functions that `await` it. When a future is stored in a static
/// variable it won't be garbage collected which means all zone variables and
/// variables in async functions get leaked. [DetachingFuture] works around this
/// by forgetting the original [Future] after it has resolved, and wrapping the
/// resolved value with `Future.value` for later calls.
/// In the case of a future that resolves to an error the original future is
/// retained.
class DetachingFuture<T> {
late T _value;
Future<T>? _inProgress;
DetachingFuture(Future<T> inProgress) : _inProgress = inProgress {
inProgress.then((result) {
_value = result;
_inProgress = null;
Future<T> get asFuture => _inProgress ?? Future.value(_value);